Re: [Repeater-Builder] Wacom WP-639 Duplexer question

[Kevin Custer]

  On 9/8/2010 6:11 PM, RichardK wrote:
> Good evening, our club has a Wacom WP-639 four can duplexer as part of our 
> repeater system.  Input Fq is 147.915 and Output Fq is 147.315.  We have a 
> 600kHz (+) offset.  Very simply, our main problem is when we run the 
> transmitter at full power 100 watts, there is a HUGE desense on the receive 
> side of things.  When we drop the transmitter power level to around 20-50 
> watts, the receive side opens WAY up to a large area where people can get 
> into the repeater.  As we begin to bring up the transmitter power, "white 
> noise" begins to appear and the receive side starts to desense again.  All 
> the cables have been switched to double sheilded cables and all the same 
> wavelength in length.  We have the duplexer seperated&  sheilded from the 
> transmitter&  preamp parts.  We have not replaced the antenna feed coax with 
> double sheilded coax yet.  Antenna is a Hustler G7 atop a 55' mast.  The 
> duplexer was retuned just over 1 year ago. Any suggestions as to what we 
> could look into next?  Some of us believe the problem is with the tuning of 
> the duplexer receive cans.  Thank you very much.


The Wacom WP-639 is insufficient for 100 solid state watts, unless you 
run a GE MASTR II PLL exciter and no preamp.

You will either need to replace the duplexer with another unit capable 
of properly isolating 100 solid state watts, add additional filters, 
change to a less noisy transmitter and amplifier (tubes are better - no 
I'm not kidding).

Kevin Custer - W3KKC

Re: [Repeater-Builder] Running a Mastr II Repeater QRP

[Kevin Custer]

  On 8/30/2010 6:01 PM, Chuck Kelsey wrote:
> I agree with Jeff 100%.

Me three...

Kevin

Re: [Repeater-Builder] ariels

[Kevin Custer]

  On 8/29/2010 1:15 PM, Doug Hutchison wrote:
> Ariel?  Antenna maybe? C'mon guys.

Be careful Doug.  The poster is from the United Kingdom, where they use 
the term Ariel, not Antenna.

You know what it means, so let it go.  This list is not just for 
Americans, as we have many members from other Countries.

Kevin Custer
List Owner

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

this works for my 2007 copy anyway).
Is it less a voltmeter because the induced voltage tracks current on 
the line?  Want to call it an ammeter or current meter then, after all 
that's what the actual meter movement is?


Talked yourself right around the circle there. ;-)   You didn't say 
anything about CURRENT in your first post.
While it reads voltage, it also reads current.  These two are combined 
to read power.




I submit this particular voltmeter happens to be calibrated to read 
average power at 50 ohms impedance, and it does this quite well within 
its limitations. 



No - they measure current and voltage and display power in watts, no 
matter what the impedance is.


/ That's why they can be fooled into displaying an erroneous reflected 
power reading, perhaps lulling us into a sense of security that the 
VSWR on the line is acceptable when it may not be./


Sorry - I don't agree.

Kevin Custer

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Ross Johnson wrote:



So will someone post a simple rule of thumb... If you have the option 
of optimizing cable length from PA to first cavity, IE you haven't 
made them yet what's the best "simple" rule of thumb to follow to 
build them to avoid reactance. 1/2wl if allowed minus coupling loop 
depth? Or is that past a simple thumb.




Simple rule - there is none.  The length can be determined 
experimentally as outlined in several publications of various duplexer 
manufacturers.


I use the length I need to do a good job - then, if the transmitter is 
unhappy, I build a cable long enough to do the job and satisfy the 
transmitter.


Kevin

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Russ Hines wrote:



Some related comments, if you don't mind.

Temperature changes seem to be the biggest "detuner" of largely 
mechanical devices like cavity duplexers.  We often send our repeaters 
off to live in less-than-ideal environments, then expect cavity 
input/output impedances to remain as we measured them in the shop?  
Don't think so.


I largely disagree.  Most modern duplexer designs (within the last 25 
years or so) use compensating elements to make the duplexer or cavity 
temperature stable.  Invar is a nickel-steel alloy that exhibits about 
1/10 the thermal expansion as a common carbon steel counterpart.  Invar 
is used to make the tuning rod - many times it's threaded.  The rest of 
the duplexer or cavity is usually made of similar metals and generally 
thermal expansion occurs across these components equally, resulting in 
extremely low frequency drift over its rated operating temperature.





Our in-line power meters, like our trusted Bird 43, do not directly 
measure power.  They're really voltage meters calibrated in watts at a 
specific impedance.  That's why they can be fooled into displaying an 
erroneous reflected power reading, perhaps lulling us into a sense of 
security that the VSWR on the line is acceptable when it may not be.


What?  Maybe you would like to have another chance at that one

Kevin Custer

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Kevin Custer wrote:
I had one instance of a ham radio club loosing PA's left and right on 
their 2M machine.


Indeed - I am loosing my mind - 

K

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Kevin Custer wrote:


Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II 
repeater and gets 50 watts out the antenna port.  He does his homework 
and realizes that he should only be loosing 29%


Wow -* loosing -*  that should have been losing - that's what I get for 
being in a hurry

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Jeff DePolo wrote:
Because the impedance is not matched between the transmitter 
and duplexer, the 'apparent' loss of the duplexer is greater 
than the manufacturers stated loss of the duplexer.  Changing 
the cable length is not changing the loss of the duplexer, 
it's changing the power that is accepted at the transmitter 
port of the duplexer by matching the output impedance of the 
transmitter to the input impedance of the transmitter port of 
the duplexer.



But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying
the cable length isn't going to change the Z seen by the transmitter.  Or
are you suggesting the duplexer is purposely de-tuned from 50 ohms?
  


Purposely, accidentally, by lack of good design - people not having the 
right equipment to tune it correctly - whatever.
  
	  And also that by varying the cable length between the 
transmitter and the duplexer that you can vary the reflected

power on that same line?


Yes.



With all due respect, that's not possible, regardless of what the Z is of
the duplexer.  The only time it could have an effect on the reflected power
would be if the transmitter/PA were spurious, and the amplitude/frequency of
the spurs changed with varying load Z, and I think we can both agree that if
that's the case, we have bigger fish to fry.
  


And this is where I believe the duplexer manufacturers are covering 
their butt.  They don't want the problem with complex reactance 
presented by the duplexer to be their problem.  Not that I don't agree, 
because it's usually the transmitter that is really at fault. 

Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II 
repeater and gets 50 watts out the antenna port.  He does his homework 
and realizes that he should only be loosing 29% with the 1.5 dB of 
insertion loss stated in the paperwork - but he's loosing over 50%.  The 
duplexer manufacturer supposedly engineered and tuned it for a 50 Ohm 
system.  He knows that the cable he connected to the transmitter is 
good, because when he disconnects the end going to the transmitter port 
of the duplexer and connects it to his Bird 43 terminated with a good 
load - it reads 110 watts.


Now, is the transmitter becoming spurious and the cable length being 
changed in length satisfies the match between the duplexer and 
transmitter - I don't know...   All I can tell you is I have followed 
the suggestions written in the WACOM manual and it has worked.  I had 
one instance of a ham radio club loosing PA's left and right on their 2M 
machine.  They told me of the situation and I offered to do a little 
testing.  The 110 watt PA would put out 110 watts into a Bird and dummy, 
but only 45 watts was coming out the antenna port of the duplexer.  At 
the time I didn't own a spectrum analyzer.  The repeater wouldn't duplex 
without desense.  I changed the length of the line between the PA and 
duplexer until I got the power to read about 75 Watts as I remember.  
That was 13 years and they still have the same PA - no desense either.




Not to belabor the point, but whatever the VSWR is on a length of
transmission line, that's the VSWR that's on the line *regardless of
length*.  You can't change the VSWR by changing the length of the line.  As
you vary the length, you go round n' round the Smith Chart in a constant
VSWR circle, with the Z repeating cyclicly every half-wavelength, but you've
still got a complex Z that nets a 1:5:1 VSWR relative to 50 ohms at the end
of whatever length of line you choose (cable loss effects notwithstanding).
There are an infinite number of complex Z's that yield a 1.5:1 VSWR - cut
the line to any random length and you'll hit one of them.

  
In a situation where the duplexer and transmitter have 
differing impedances, and a cable optimized in length matches 
these impedances, the mismatch at the duplexer is minimized, 
therefore the power reflected by the duplexer is minimized.  



I think what you're really saying is that the mismatch at the *input to the
matching section* (i.e. the cable between the PA and the duplexer), NOT the
mismatch at the duplexer, is minimized.


Sorry - that is what I meant to say.  Many of us use converted 
commercial gear in the ham band.  Many don't take the time to properly 
convert the receiver and especially the transmitter to properly operate 
in the adjacent ham band.  So, when you run a 150.8 to 174 MHz amplifier 
in the 2M ham band or a 450 to 470 MHz amplifier in the UHF ham band is 
it going to represent a good 50 Ohm impedance?  Likely not...


We need to realize that most duplexer manufacturers know what they are 
doing and their products are presenting a 50 ohm match on its intended 
frequencies - unless somebody has adjusted on it.  But, because the 
duplexer is not a perfect load, it creates reactance and the 
transmitter/PA may not like it.  If it doesn't like it, it may become 
spurious.  If it becomes spurious, it isn't putting out all of its power 

Re: [Repeater-Builder] Need low power PA mod help for VHF MVP

[Kevin Custer]

Thomas Oliver wrote:



I am in need of a 2-5 watt range amp to drive an external amplifier, 
the stock VHF MVP amp is adjustable from 8-25 watts output,


I think by bypassing Q202 I will be close to my goal.  I need to know 
where to connect the coax to keep Q201 from getting mad.


I have done this on UHF MVP's before but the VHF amp is coupled 
differently between stages.


Schematic here:  www.repeater-builder.com/ge/lbi-library/lbi-30143a.pdf


Try removing Q202 and placing a coupling capacitor between the pads 
where the Base and Collector were.  Something between 100 and 470 pF 
should do it.  I'd use a silver mica with short leads.


Kevin

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Jeff DePolo wrote:


Maybe I'm not understanding right.  Are you saying that by varying the cable
length between the transmitter and the duplexer that you can affect the
insertion loss of the duplexer?


No. 

Because the impedance is not matched between the transmitter and 
duplexer, the 'apparent' loss of the duplexer is greater than the 
manufacturers stated loss of the duplexer.  Changing the cable length is 
not changing the loss of the duplexer, it's changing the power that is 
accepted at the transmitter port of the duplexer by matching the output 
impedance of the transmitter to the input impedance of the transmitter 
port of the duplexer.



  And also that by varying the cable length between the transmitter and the 
duplexer that you can vary the reflected
power on that same line?


Yes.

In a situation where the duplexer and transmitter have differing 
impedances, and a cable optimized in length matches these impedances, 
the mismatch at the duplexer is minimized, therefore the power reflected 
by the duplexer is minimized. 


  Please tell me I'm reading this wrong...I've been
on the road a long time and working a lot of long hours, so it's quite
possible...

--- Jeff WN3A


I have found that when you get a transmitter that is 'picky' about the 
length of interconnecting cable, power being read at the output port of 
the duplexer is low and you cannot alter the tuning of the cavity 
closest to the transmitter to make things right.  In other words, the 
place where lowest VSWR and maximum power transfer occurs is at two 
completely different places, and power transfer is not up where it 
should be (transmitter makes 100 watts into a dummy load but only shows 
50 watts on the output port of the duplexer that has a stated 1.5 dB 
loss (29 %)).  As you get close to the 'optimum' cable length, the 
lowest VSWR and maximum power transfer occur near the same place when 
tuning the cavity closest to the transmitter.


I usually pay more attention to what is coming out the antenna port of 
the duplexer - first.  Then, when things are right, comparing forward 
power going to the duplexer and power going to a good dummy load will be 
very close the same, since matching the impedance of the transmitter to 
the impedance of the duplexer was accomplished by some means.


I use a compensation cable along with my Bird so that the samplers 
transmission line length is nullified in the line under test.  This 
compensation cable results in exactly 1/2 WL including the samplers 
transmission line.  Compensation cable lengths are outlined in the 
manual for the Bird 43.


Kevin

Re: [Repeater-Builder] Dissasembly of msr 2000 continuous duty amp. How?

[Kevin Custer]

radi...@aol.com wrote:


Hi Kevin,
The desense is a staticy reception of "weaker" signals( ie an HT at 25 
miles) It had gotten worse as it started to affect strong signals too. 
If the transmitter was turned off, the repeater could hear just fine. 
Problem is intermittent and often followed a rainy day. We replaced 
"EVERYTHING" A UHF repeater on the same tower is unaffected. At this 
point we think the "new" antenna is failing. Tower sections have been 
bonded grounds improved etc etc


To know whether or not the problem is the antenna system, do a 
desensitization test directly at the antenna port of the duplexer using 
a good load and a lossy tee or other acceptable method like a coupler 
slug installed into the Bird Watt meter.  If you don't know how to 
perform a desense test, there are several articles on the website that 
will assist you.


If this proves good, then you have more work to do on the outside.

Let us know...

Kevin

Re: [Repeater-Builder] Mirage B-320-G as a Repeater Amp

[Kevin Custer]

Bob - AF6D wrote:
> Before adding a Mirage 320 our TKR 750 was putting out 50 watts into a 6 
> cavity Wacom WP-642 at the cost of 2-3dB loss on TX (as the spec sheet said.) 
> The cans are tuned right on the money and the Hustler G5-144 fed with LMR-400 
> is 1.1:1. This has worked for over a year just fine (except for grungy weak 
> signal audio.)
>
> Now add the Mirage B-320-G 200 watt amplifier. It seems to work just fine 
> outside of the repeater chain. On its low setting 3 watts will drive it to 
> 200 watts. On its high setting 50 watts will drive it to 200 watts. We plan 
> on adding two fans on the heat sinks and rack mounting it and running it with 
> only 25 watts drive. The power meter lights up all the way to the red.
>
> But as soon as we tune it all up and connect it to the duplexer the Mirage 
> SWR/Drive trips and the amp goes to sleep. A SWR meter between the repeater 
> and the amp shows 1.1:1. The amp to the duplexer shows 1.1:1. The duplexer to 
> the antenna shows 1.1:1.
>
> I've lost my mojo. Waz up?

We'll assume the Mirage amplifier is either tuned to a 50 Ohm output 
impedance by any internal adjustments or there are no adjustments to 
tune the amplifier to match the load.

That being said, it is possible that the Mirage Amplifier doesn't like 
the reactive load presented by the duplexer.  If so, you will need to do 
one (or more) of the following:


1.) Use an impedance matcher (sometimes referred to as Z-Matcher) 
capable of handling the output power of the amplifier.
<http://www.repeater-builder.com/db/pdfs/db-z-matcher-tuning-info.pdf>
<http://www.repeater-builder.com/antenna/duplexer-cabling-lengths.html>

2.) Use an Isolator or Circulator tuned to your transmitter frequency 
properly sized to absorb the reflected power.  You still might have to 
use #1 or #3 to aide in matching so you aren't wasting the power 
reflected back to the transmitter or the power not being transferred to 
the duplexer, out the antenna port, as seen as a loss greater than the 2 
to 3 dB stated by the manufacturer for this duplexer and your 
interconnecting cabling.

3.) Optimize the cable length from the amplifier to the transmitter port 
of the duplexer to maximize the return loss (create a better match).
http://www.repeater-builder.com/antenna/duplexer-cabling-lengths.html
Please also read the note about cabling lengths between the repeater and 
the duplexer in the section on page 4 of the following document:
<http://www.repeater-builder.com/wacom/wp6xx-vhf-tuning-instructions-remec.pdf> 


Watch for word wrap...
Doing #3 might require doing #4.

4.) Optimize the tuning of the first cavity of the duplexer from the 
factory setting.  BE CAREFUL HERE...   Assuming no one has ever tuned 
the duplexer from its factory settings, and assuming the factory knew 
what they were doing and tuned the duplexer correctly (tuned it for 
maximum return loss (best match at 50 Ohms on your frequencies) and best 
response, or a compromise of both - usually the case in a factory tuned 
Wacom product.  Realize if any cavity is/was re-tuned at any point you 
are altering the response intended by the factory.  It is possible, 
however, to optimize the cable length and lightly retouch the tuning the 
first cavity to fix the situation you have encountered.  Optimizing the 
cable length will shift the impedance to create an acceptable match 
between the amplifier and the transmitter port of the duplexer and 
retouching the first transmitter cavity will nullify the reactance 
presented by the line.  If you are not willing to re-tune the duplexer, 
then only consider the solutions in #1 or #2.

I'm hopeful Jeff DePolo or Allan Crites will look this over and add 
correct what ever I missed.

Kevin Custer

Re: [Repeater-Builder] Dissasembly of msr 2000 continuous duty amp. How?

[Kevin Custer]

radi...@aol.com wrote:


 
Hi Kevin,
I have confirmed that 2 of the 4 finals are bad. both  are on one side 
of the push pull. Both open base connection One has collector to 
emitter short. The other open emitter.
I have not yet checked the drivers I might be able to test them 
without removal. I have a friend trying to scare up a Mitrek
Aside from the transistors which I know are hard to find, and the 
cooked 12 ohm resistors, Is there something else I need to look for?


I doubt it.  Usually the resistors go because of the imbalance from one 
or more of the transistors failing.
I recommend replacing all of the output together with matched gain 
transistors, if you choose to repair the PA.


We think it was an intermittent Duplexer or antenna issue that caused 
it to blow. We have since replaced the repeater, amp,  and duplexer 
but a desense condition has returned after a few weeks. The antenna is 
a 4 bay folded dipole on a 100 foot tower. this  Antenna replaced a 
Stationmaster  only about 3 years ago. Tower is Rohn 45?  guyed with 
Phillystrand.

Thanks for your help.
Marty


What kind of desense?  Does the repeater properly duplex on a known good 
dummy load?


Kevin

Re: [Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?

[Kevin Custer]

wb6dgn wrote:
> "There is a process I use to easily see which stage is 
>  bad.  Reply if you need more help."
>
> Maybe you'd consider posting it here?  Always looking for better ways to do 
> things.
> Tom DGN

Verify you have drive to the PA by looking to see how much is coming out 
of it or any filters that follow.  Then take the watt meter and put it 
on the antenna connector and terminate the meter with a suitable load.  
I use a Bird 43 with matching 100 watt dummy load.  I usually start with 
a 10 or 25 watt slug no matter the size of the PA.

If the correct drive is coming from the exciter, make sure the correct 
voltages are present on the stages of the PA.  PNP RF transistors are 
used in the MICOR VHF PA, so put your thinking cap on upside down. 

If you have a hand-held radio, tune it to the frequency of the 
transmitter, and remove the rubber duck and set it off to the side - out 
of arms reach.

Key the defective radio and touch the base of the first transistor in 
the PA with the metal blade of the Motorola MICOR tuning tool.  Watch 
the S-Meter on the hand-held or listen for quieting.  On my Yaesu FT530, 
I normally get about 1/2 scale S-Meter reading on the base of the first 
stage.  Keeping the radio keyed, touch the collector - the S-Meter 
reading should be considerably stronger and quieter.  If not, you might 
have found your problem.

Anyway, continue doing this down through the stages until you find the 
bad one - moving the hand-held radio back away as need to add loss.  
Once you find the stage that has no apparent gain, take a small 
capacitor (a few hundred pF) and trim the leads so you can use it to 
bridge across the base to the collector.  The leads only need to be long 
enough to be able to go across the transistor to couple energy at the 
base to the collector.  If the stage is bad, you will see the PA make 
*some* power  - there will be some indication on the watt meter.  The 
transistor, when bridged shows output power, is likely bad and needs 
replaced.  This method can generically to troubleshoot other makes and 
models of PA's. 

DISCLAIMER:  I have worked on some ill engineered equipment that will go 
spurious and blow up if you touch one of the RF transistor conductors 
with some metallic object.  This has never happened to me with a MICOR 
or MASTR II PA, but has with Spectrum and some other junk.  Do This At 
Your Own Risk!!

In the MICOR, the first or second stages are usually the culprit, unless 
something has taken out the final stages, which should only be replaced 
as a whole, with matched units, if one or more are found to be bad.

Kevin Custer

Re: [Repeater-Builder] Re: Coax length, etc.

[Kevin Custer]

motarolla_doctor wrote:
> Kevin,
>
> I am using your coaxial matching section on a couple of antennas with good 
> results. Great article on RB and not too hard to build

MD,

I wish I could take the credit, but the original concept was from a 
friend W8ZD - I just improved upon his concept.  For those interested in 
what we are referring to, or, have availability of large (free) CATV 
hardline and want to use it in 50 Ohm service, go here:
http://www.repeater-builder.com/projects/matchingstubs.html

Thanks,
Kevin

Re: [Repeater-Builder] Dissasembly of msr 2000 continuous duty amp. How?

[Kevin Custer]

Tom Parker wrote:



Why has no one suggested replacing the guts of this beast with a 
Mitrek PA?


Why?

Kevin

Re: [Repeater-Builder] Dissasembly of msr 2000 continuous duty amp. How?

[Kevin Custer]

radi...@aol.com wrote:



Sucess!
I completely cleaned and re tinned my Weller 8100 tip, added some 
solder, and got heat transfer to pop it up. I was not aware of the 
fish paper that the wires came thru. Now to troubleshoot the amp. It 
probably has some blown transistors as well as the cooked caps and 12 
ohm resistors across some of the finals. We do have a Motorola test 
set, I have done component level work in the past, but this is out of 
my league. Kevin, I may take you up on your offer for further help.

Thanks to all who responded.
73, Marty


Consider obtaining a used MICOR mobile (usually can be gotten for $5 to 
$50) having a power amplifier board of the desired size and transplant 
it onto your heatsink.  The PA assembly for this mobile radio is 
identical to the one(s) used on the continuous duty MICOR and MSR2000 
power amplifiers.


Or, just figure out which stage is bad and replace the transistor(s) 
that have failed.  There is a process I use to easily see which stage is 
bad.  Reply if you need more help.


Kevin

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Russ Hines wrote:


Thanks, guys, a good topic and one that always seems to come up.  And 
it sparks more questions and comments, of course.


The cable length issue is a brother to "if you don't like your VSWR, 
change the point along the transmission line where you're measuring 
it."  By changing the length of the line, we're creating a 
transmission line transformer (a good thing) but we're limited by its 
length (not so good).  It seems to me the mentioned 
circulator/isolator at the output of the xmtr is a better fix, as 
reflections coming back from the duplexer is absorbed by the 
circulator's load, the xmtr is generally happy, and we're no longer 
limited where we can put things in a rack or elsewhere. 

For amateurs, coming up with usable VHF circulators seems to be 
difficult and usually expensive, and coax always seems to be cheaper.  
Has anyone had luck finding a source for reasonbly priced VHF 
circulators, or success in rolling their own?


Also, I noted in the pamphlet Kevin referenced that the unused 
duplexer port was left open (Figs. 1 & 2).  I guess if the isolation 
is already greater than the load's return loss, it doesn't matter, at 
least at the reject frequency.  But it seems to me one could possibly 
create problems for oneself by not terminating the unused open port.  
Just a thought.


Maybe I work better knowing there's a load there. ;-)

Your comments, please. 


73, Russ WB8ZCC




I think we all agree that a real impedance matching device is the best 
approach, but hams (generally speaking) are cheap.  Many will spend two 
days hacking on a piece of RG-214 before spending fifty or a hundred 
bucks on a different (better?) solution.


Allan Crites and I are currently in discussion which will be used as the 
basis of a RB web article that will explain exactly what is happening, 
why it happens, and why an 'optimized' cable length can be used to 
transfer power ending up with the stated loss of the duplexer and have 
little reflected power toward the transmitter - so long as the duplexer 
is tuned properly and exhibits good return loss on the frequency it's 
designed to pass. 


Kevin Custer

Re: [Repeater-Builder] Coax length

[Kevin Custer]

Doug Hutchison wrote:
> Does the length of coax connecting cable between repeater and filters 
> matter?


Yes - and no.

Please read the note about cabling lengths between the repeater and the
duplexer in the section on page 4 of the following document:
<http://www.repeater-builder.com/wacom/wp6xx-vhf-tuning-instructions-remec.pdf>

Watch for word wrap...

Kevin Custer

Re: [Repeater-Builder] Re: Dissasembly of msr 2000 continuous duty amp. How?

[Kevin Custer]

Bill wrote:
> Apparently no one here got the moto memo on working with giant 
> heat-sinks. First you only need a 30-40 watt iron to work on them as moto 
> did at the factory  The secret is.. raising  the heat-sink to 
> about 3-400 degrees while you are working on what needs to be done.  PS 
> .. don't touch it with fingers or arms.  This technique also lowers 
> possibility of cracking the ceramics. I usually lay out everything that has 
> to be done in advance with extra planning.  Hey, I didn't say it was going to 
> be quick...
> .
> Bill
> Atlanta

The amplifier in question is a MSR2000 VHF, not  UHF - no ceramics to 
worry about - no oven required.

Kevin

Re: [Repeater-Builder] Dissasembly of msr 2000 continuous duty amp. How?

[Kevin Custer]

radi...@aol.com wrote:



OK Kevin,
I had already tried the desoldering with a really good Pace unit, but 
the heat did not transfer well. I will get a buddy to help and use my  
Weller guns. I have a big 250 watt one here somewhere.

Marty



Let us know how you make out - or, if you need more help...

Kevin

Re: [Repeater-Builder] Dissasembly of msr 2000 continuous duty amp. How?

[Kevin Custer]

radi...@aol.com wrote:


Thanks Kevin,
I think you are on to something. The areas that are pinned down seem 
to be close to where the power supply wires enter the board from the 
underside. I am wondering if the wires are glued down with RTV or 
something.  Cautious prying is still not getting me anywhere.

Marty



Get a friend.  Using two solder guns (Weller 8200 or like) heat both 
joints where the feed-through pins come through.  Pull straight up when 
you have both heated well enough that the solder is fully molten.


This process can be done with one gun/iron, but it's difficult at best; 
as you have to alternately heat and pry which puts a good bit of strain 
on the board until it becomes free.  You could also try a de-soldering 
tool cleaning out the holes where the feed-throughs protrude from the 
board, but again, this can be difficult to remove the solder that lays 
under the board depending on the amount of heat you apply and the 
quality of your de-soldering pump.


Kevin

Re: [Repeater-Builder] Dissasembly of msr 2000 continuous duty amp. How?

[Kevin Custer]

martinfriedman67 wrote:
> Our Amateur radio club's Motorola MSR 2000 continuous  duty amp needs repair. 
> I cant figure out how to remove the amp board from the heat sink. I removed 
> all screws from corners as well as the transistors. It seems to be held by 
> the center,  just below the tall air variable cap. I tried heating the  
> solder in the area but, no joy. I don't want to crack the board. The drawings 
> in the manual I found here do not show even the screw holes.
> Thanks in advance, 73, Marty (WB2BEW)


Look for the via that carries the power supply connections to the 
board.  Sounds like they are holding you back. 

Kevin

Re: [Repeater-Builder] Repeater trans mit levels at the receiver?

[Kevin Custer]

n...@no6b.com wrote:

At 7/31/2010 09:31, you wrote:
  

Joe - the picture was inside the e-mail.

Bob - it is an SO-239 Tee, and it is into
a dummy load.  (checked on 2 different ones).



Longshot, but try replacing the T, preferably with a silver-plated one.  I 
know I've had old PL259/SO239 elbows generate desense when I tried using 
them on the duplexer output of my 2 meter portapeater.



Cutting apart some cheap UHF elbows manufactured by a famous CB company 
revealed a spring between the contacts.  Great for CB, not so great for 
VHF/UHF.


Use Amphenol or Kings - costs more, but tastes great - less filling

Kevin

Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier

[Kevin Custer]

  
Kevin wrote: 
The problem is, like any receiver that has several 
helicals in cascade before the first active stage, 
the loss that precedes the active stage has a majority 
role in the overall NF of the system that follows.  It 
matters little what the quality of the active stage is, 
because the loss has already determined (for the most 
part) the system Noise Figure.


Skipp wrote:
Kind of makes it look like helicals are a sin doesn't it... 
  


Hamtronics thinks it's a sin  -  that's why their receivers have some of 
the best sensitivity numbers of all of the stuff we commonly build 
repeater from.  However, their receivers get hammered in high RF density 
locations, and the result is the need of some added filtering ahead of 
it.  This is where the GLB can and does provide an improvement.  I speak 
with experience here.  I have used many Hamtronics receivers and GLB 
preselector/preamps (that I bought new) over the years. 

If you are lucky enough to have a really clean repeater site, the 
Hamtronics receiver line will work fine with no added preselection.  I 
bought the GLB's primarily for protection to the repeater receiver when 
I was using a frequency agile in-band remote base.  Many times it was 
possible to link to repeaters on the adjacent channel when I had the GLB 
in place.  The addition of the GLB wasn't without its drawbacks though.  
My Hamtronics receiver would hear at -125 dBm for 12 dB SINAD stock with 
no preamp or preselection (the first GaAs device is basically 
unprotected).  Running an in-band remote base anywhere within a MHz or 
so of the repeater input would desensitize the Hamtronics repeater 
receiver.  After installing the GLB, I could link to repeaters 15 kHz 
away from my input with very little desense from the remote base 
transmitter.  Anything over 60 kHz had no affect on repeater receiver 
sensitivity.   The link beams were 50 to 100 feet below the repeater 
antenna and I normally run 5 watts on the Icom 900 stack.




A 2-Meter version I have lots of pictures of has 1 stage of 
pre-selection and four trailing stages. The active device is 
an MRF-901. And the coupling for this model is a slightly 
different method than some (not all) of the other models I 
have looked at. 
  


Are you sure that's not 4 section preceding the device and 1 following?



In more than a few real world situations you might really 
need the filter pre-selection a lot more than the most 
optimum NF. A practical trade of pre-selection for a slightly 
higher noise figure can and does sometimes make the difference 
in a usable radio system.
  


No argument here   If the site noise figure is worse than the NF of 
the GLB, adding it won't hurt your actual effective receiver 
sensitivity, and the added filtering can be a real boost.  However, I'm 
blessed with sites that allow me to realize most of the sensitivity from 
a good preamp - with not much ahead of it (now that I don't do much RF 
linking).


Kevin

Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier

[Kevin Custer]

Joe wrote:
>   Hello Bob,
>
> I agree that the GLB is a space saving device, but don't you think that 
> the multistage helical coil stages in the preselector with beat a single 
> cavity in skirts and out-of-band rejection?

Curves for the GLB are available here:
http://www.repeater-builder.com/glb/glb-preselector-order-form.pdf

While the skirts and OBR of the GLB might beat a single cavity, many 
times it isn't necessary - especially if the receiver that follows is 
able to cope with high out of band signals and the preamp that follows 
the cavity has a high overload point. 

The problem is, like any receiver that has several helicals in cascade 
before the first active stage, the loss that precedes the active stage 
has a majority role in the overall NF of the system that follows.  It 
matters little what the quality of the active stage is, because the loss 
has already determined (for the most part) the system Noise Figure.

The GLB preselector preamp has 4 helical stages of unknown (unknown to 
me) coupling.  If they are over-coupled (and I believe they are not 
looking at the response curves) only a few dB of loss will occur before 
the active stage.  If they are lightly coupled (which I believe is true) 
then several dB of loss occurs ahead of the active stage.  Every dB of 
loss ahead of the first active stage ADDS to the system NF - period.  
This loss can NEVER be recovered no matter how good the preamp is that 
follows. 

Kevin

Re: [Repeater-Builder] Repeater transmit levels at the receiver?

[Kevin Custer]

Tim wrote:
> Hi Kevin,
>
> Yes, the original used RG-58.. couldn't see using it.  Figured
> it would give me desense!
>
> As far as the amount of notch, I was surprised that the total
> was more than each one added,

Don't be - it's common for the apparent notch to be deeper than the 
measured addition of individual cavities - added together.  Don't be 
fooled, the depth was there the whole time (no black magic here), it 
just wasn't all being realized in the test set-up.  Proper interconnect 
cable lengths can do a bunch for notch depths. 

>  but with 50 watts
> coming out of the antenna port, I see -55dBm at the RX
> port. - kinda made me think the original measurements
> were ok.
>   

What you see coming out the RX port depends on several factors:  How 
good the match of the attached equipment is - at the frequency being 
tested, and the phase angle of the connecting cable.  Other factors play 
a part too, but these two play the bigger part. 


> I cut them to 35" each. (visible coax showing between each
> end of the PL-259).  Not exactly to length.  Might affect
> performance a bit.

I wouldn't have chosen UHF connectors for building the duplexer.  IMHO, 
their construction leaves a lot to be desired when trying to optimize a 
duplexer for maximum performance, unless you take their inherent flaws 
into consideration when using them.  Wacom built a good duplexer which 
uses UHF connectors, but they actually used those properties to their 
advantage.

35 inches, plus the amount inside the connector results in approximately 
37-1/2 inches of interconnecting cable.  From my calculations, I have 
extrapolated your optimum notch depth to appear on 54.44 MHz.  I 
believe, with RG-142 coax, that a length longer than 38 inches will be 
needed, depending on your exact frequency. 

 From your photo, I believe some of your problem to be the UHF connector 
and how you have it mounted.  A solid ground all around the connector is 
important to achieve a low impedance (low inductive reactance) 
connection.  I have always preferred the "Utah Cap" approach for 
building the Heliax duplexer.  It allows you to realize most/all of the 
potential of the stub.  The thicker the copper (within reason) the 
better.  Also - it looks like you might be using only one connector per 
stub.  If this is true, and you are using a UHF tee connector with the 
stub - it won't work as expected.  The electrical length of the tee will 
throw the whole thing off - this might be your biggest problem with your 
design/construction.

Kevin

Re: [Repeater-Builder] Repeater transmit levels at the receiver?

[Kevin Custer]

Tim wrote:

Hi Kevin,

On the notch depth, using Wavetek 2410 for signal source,
HP 8590B spectrum analyzer.

Start @ 0dBm on sig gen.

1st 'can'.  hook input to sig gen, output to SA.  Using RG-142
with PL259s.  Using a T at the can.  Tune for minimum signal
display on SA.  Hook up 2nd in series, - tune for minimum. 
Hook up 3rd in series.  Up sig gen to +20dBm.  Hook up 3rd can. 
Tune for minimum.  Looks to be about -80dBm.  80+20=100.


I have some experience with this duplexer and about 80 dB of rejection 
(or so - some are slightly worse than others) is all that can be 
afforded with three stubs of "inch and 5" in cascade.  I'd say something 
is amiss with your test set-up.  Some reactance is likely occurring 
which is skewing your test results.  You should be seeing some real 
world numbers between -70 and -84 dB for the notch depths depending on 
your construction.


You said you used RG-142 for the interconnecting cables.  What method 
was used to calculate the lengths - or did you simply cut them to the 
lengths called out in the article/website/diagram?  As I remember, RG-58 
was used in the original article.  The velocity of propagation (velocity 
factor or VF) is different between RG-58 and RG-142 therefore making the 
lengths of cable different than what is called out for RG-58. 


Kevin

Re: [Repeater-Builder] Repeater transmit levels at the receiver?

[Kevin Custer]

Tim wrote:


Actually, the output is about +26dBm, so it's closer to 400mW.


Good - that's more like it.


I've also tried a VX-5 on low power, and got the same result.


Obviously, something is wrong with the operation of your duplexer or 
interconnecting cabling.  I really don't think it's providing the 
isolation you believe it is...


Can you explain in detail how you are determining the notch depth of the 
duplexer.  Also, what exactly are you using for the components of the 
duplexer?  If it's the coax stub type, which article have you followed?


Thanks,
Kevin

Re: [Repeater-Builder] Repeater transmit levels at the receiver?

[Kevin Custer]

Steve wrote:
> Hi Kev
> would it be feasable to use a sig gen cranked right up ?

Depends on how clean the signal generator is.  I'd think it doesn't have 
enough smoke (output capability) to really be beneficial

Many generators have a strong carrier (here we go again) adjacent from 
the desired carrier by few, several, many kHz/MHz.  Also, depending on 
make/model, it may not be as clean (spurious emissions) as a tuned 
circuit (read MICOR exciter).




I wonder how many of the -53 naysayers have or have used a Cushman 
CE-3?  LOL!  The folks that have looked at the output of one of these on 
a spectrum analyzer will get it.

K

Re: [Repeater-Builder] Repeater transmit levels at the receiver?

[Kevin Custer]

Tim wrote:
>
> Using the Micor's exciter - about 270mW.  Cannot see any spurs/noise
> within 80dB of the main carrier.

I wonder Most of the MICOR exciters I have converted to 6M 
result in more than 270 mW of power  - in fact, 400 to 600 mW is 
common.  I wonder if something is amiss at the exciter, like a bad 
crystal or stage not peaked correctly generating noise.

If you have a 6M hand-held or mobile rig capable of transmitting on your 
repeater output frequency, try substituting it for the MICOR and see 
what happens to your receiver with one of these transmitting instead.

Kevin

Re: [Repeater-Builder] Re: Simrex - GLB Pre-Selector Pre-Amplifier

[Kevin Custer]

skipp025 wrote:


The less gain is related to the internal filtering "stages", 
not the device.  I would expect the version with the GasFet 
to have the typical expected NF for that device. Any other 
available active devices to have Noise Figures commensurate 
with their typical expected values (for those devices). 

  
I doubt it.  But without any real NF numbers, it's all 
guesswork.



I have measured all the original GLB Pre-selectors and their 
performance values are very realistic (no surprises). I wouldn't 
expect a surprise/difference if I ordered the GasFet equipped 
Simrex Pre-selector. 


What you are missing is that ANY losses ahead of the first active stage 
add to the noise figure of the system - directly.  So, while filtering 
exists in the GLB device, so does loss, and this loss is more than what 
is experienced when using a quality large diameter cavity.  Many times 
Skipp you tell us there is no free lunch, and the same applies to the 
comparison of selectivity and loss between the GLB and a quality cavity 
followed by a good active stage.


Real world test.  Take a Hamtronics receiver (no preamp) and do a basic 
bench sensitivity test to obtain a baseline.  If you find something 
around -123 dBm your in the right ballpark.  Now install a bi-polar GLB 
preselector/preamp in front and measure the sensitivity again - you'll 
find you have lost several dB of bench sensitivity - at least 3 or 4 
dB.  Take the same receiver and add a quality 1/4 bottle with a good 
preamp (your choice - something with 1.5 dB NF or less) and do the test 
again.  Now, the receiver hears at -123 to -127 dBm (dependent mainly 
upon the quality of the preamp that follows) because the filter hasn't 
severely ruined the system NF ahead of the first active stage.  Even 
though the GLB has gain, the noise figure of the design has already 
determined the sensitivity that will be realized by the receiver that 
follows.


The GLB preselector/preamp should not be considered for adding basic 
sensitivity, because it's possible (depending on how good the receiver 
is to begin with) the opposite will happen - however, it will protect a 
receiver that lacks good front-end filtering, like the Hamtronics.  Like 
everything, the situation helps to dictate what equipment will give the 
best results. 


Kevin

Re: [Repeater-Builder] Repeater transmit levels at the receiver?

[Kevin Custer]

Larry - I didn't. 

The 250 watts is produced by a GE MASTR Pro/II 4EF5A1 capable of 330 
watts continuous.  The MICOR high-band tube amplifier, IMHO, is junk 
compared to the GE 4CX250R based VHF power amplifier.  The 4EF5A1 is 
designed to operate from 144 to 174 MHz. without modification.  
Obtaining proper drive for it was the fun part. 

Read all about it here:
http://www.kuggie.com/ahra/hmft.html

Pictures of it here:
http://www.kuggie.com/ahra/hmft.html

Kevin

> Kevin - how did you get the MICOR 250 Watt VHF Amplifier to go down to 
> 2-Meters? Or was it a factory 140-150 MHz range unit originally? 
>
> I see plenty of the 100-watt (I think they're a TLD-1692) amps that are 
> factory 2-Meter range PA decks (I have a few spares, in case I ever need 
> them) but haven't ever seen a factory 140-150 range 1/4 KW PA. I know they do 
> exist, and a few people have them. I just haven't found one, or found anyone 
> who can move the 150-170 MHz range units down to 2-Meters.
>
> Thanks and 73,
>  
> LJ

Re: [Repeater-Builder] Repeater transmit levels at the receiver?

[Kevin Custer]

Tim wrote:
> Hi Kevin,
>
> Thanks for the info.  I've used the PLL MastrII exciter on a couple of
> systems also.
>
> Now, since this duplexer is of the 'notch' variety, I already have about
> 100db of notch (on the TX side) that is tuned to the RX freq.  Shouldn't
> this be enough?


Yes, 100 dB of duplexer isolation should be plenty - something is 
obviously a amiss.  How dirty is the transmitter (spectral purity)?

Re: [Repeater-Builder] Repeater transmit levels at the receiver?

[Kevin Custer]

Tim,

I have a two meter repeater that outputs 250 watts (approximately +54 
dBm) into the duplexer.  After the 93 dB of rejection that the duplexer 
provides for shear power reduction toward the receiver port, -39 dBm of 
transmitter power leaves the duplexer receiver port - headed toward the 
receiver.  The repeater is a Motorola MICOR VHF equipped with a MICOR 
preamp.  Bench sensitivity is -125 dBm for 12 dB SINAD.  The duplexer is 
a stock Wacom WP-641.


This repeater normally uses a tube type power amplifier to achieve the 
250 watt level.  Using the tube power amp, no desense occurs on the 
repeater.  I also have a the stock 110 watt MICOR power amplifier (solid 
state) that can be switched in.  The repeater has a slight amount of 
desense when running the solid state PA.  Why?  It's obviously not the 
shear amount of power, as it has been reduced over 3 dB.  The culprit is 
/transmitter side-band noise/.  The solid-state power amplifier provides 
no additional protection of the amount of transmitter side-band noise 
being produced by the exciter, in fact, being wide-band in nature, the 
solid-state unit amplifies the noise.  The tube power amplifier, 
however, is a High Q (very narrow band - tuned to the exact transmit 
frequency) device only providing power gain on the 'desired' repeater 
output frequency, and reducing (or at least not amplifying) the 
transmitter side-band noise appearing on the receiver frequency.


From your explanation below, I don't believe shear power is ruining 
your ability to duplex, but rater the amount of transmitter side-band 
noise reaching the receiver.  To prove this, install a notch cavity in 
the transmit leg tuned to the receiver frequency. 

If your duplexer isn't capable of allowing the present radio equipment 
to properly duplex, either the duplexer needs replaced, or you can 
change the type of transmitter to something else - no, I'm not 
suggesting tube-type. 

General Electric built a VHF exciter that has 22 dB less transmitter 
side band noise (600 kHz from its primary carrier) than most multiplier 
counterparts (like your Motorola MICOR).  Using it is like installing a 
22 dB notch filter between the exciter (transmitter) and receiver where 
side-band noise is concerned.  This exciter is the MASTR II PLL.


To comment on the folks privately emailing you telling you a MICOR 
receiver cannot handle an off frequency carrier of -53 - they are full 
of it - period.  The answer is HOW CLEAN the adjacent frequency signal 
is.  If the adjacent carrier is full of noise, and that noise falls on 
the frequency the receiver is listening to - then no the receiver can't 
handle it, but that's a totally different thing ruining your lunch - 
comparing apples to oranges.


Hope this helps...
Kevin Custer



Hi guys,

Took some time away from the project... loosing too many hairs.

Ok, I've gotten another receiver strip, and it has the specified
sensitivity per Mot.

Guess I want to bounce some ideas around with those of you
who are more learned in the arts!

With 250mW (+24dBm) into the transmit port... antenna port is
a quality 50 ohm load, I see -72dBM at the receiver port. (pretty
much what I expect.. 1.8dB loss through the xmit side, & 100dB
notch through the RX side.

With it all hooked up receiving an input signal of about 0.7uV,
application of the 250mw to the transmitter side will cause noise
in the receiver, although not much.

So, it appears that if I add an additional 30dB notch (another 'can'),
the problem at high power may go away.

If I compare what 50 watts with an additional can would be (-130dB)
to what I get with 250mW & current notch (100dB), then it looks like I just
need to add an additional can.

50 w = +47dBm - 130dB future notch = -83dBm at receiver.

250mw = +24 - 100dB current notch = -76dBm

With the current notch @ 50 watts, I see a receive signal of -53dBm.
Some have said that the Micor can handle that, while others (off-line)
have said no way.

This setup appears to support the opinion that -53 is still way too much.

Any comments and thoughts would be most appreciated!

Thanks,

Tim

Re: [Repeater-Builder] Re: Repeater receiver testing

[Kevin Custer]

allan crites wrote:


Kevin, I'm sorry to have to tell you this but I think your calculator 
batteries need to be changed.

0 dBM = 0.2236 volts in a 50 Ohm circuit.
+20 dBM is indeed 100 mW and P=EI and inserting 100 mW  into the Eq. 
 for Volts in a 50 Ohm system, E= the sq. rt. of the quantity (.100 x 
50) = sq. rt. of 5 = .707 V. or 707 mV. not the 2.24 V. you indicated.



Not sure what planet you are from Allan, but since you admit that 0 dBm 
is .2236 Volts, and everyone knows that an increase in power by 10 dB is 
the same as multiplying that figure by 10, I'm correct - you are way off.



Even if the rcvr had an input Z of 50 Ohms (without any X component at 
the operating freq. which I doubt but let's accept that as so) , the 
rcvr input Z at a freq. removed by 6 MHz can hardly be assummed to be 
any thing close to 50 Ohms and is more likely to be highly + or -X 
 therefor not absorbing or accepting any input signal and your 
analysis lacks merit.


My statement said power "hitting the input port", I said nothing about 
power being accepted or absorbed into the receiver, therefore again - 
I'm correct - you are way off.


Let me remind you that, on this particular email list, I (we) strive for 
accuracy.  I don't just come up with some crap to make things 
interesting - I've been 'doing' duplex radio systems since I was 14 - 
I'm now 46, so you do the math, correctly this time. 

You state my "analysis lacks merit".  Unless you have tried the the 
experiment I refer to - and have found something different to report, 
why don't you try keeping your off base thoughts and inaccurate 
calculations/information to yourself.  If this seems to come off as a 
hot headed warning - you have read this post correctly.  (I'm the list 
owner (in case you haven't figured that out)).  By the way, the GE PLL 
exciter has 22 dB less phase noise at 600 kHz from its primary carrier 
than does its multiplier counterpart, you can bet it's way more than 
that at 6 MHz.


End of thread - everyone please more forward.

Kevin Custer

Re: [Repeater-Builder] Re: Repeater receiver testing

[Kevin Custer]

  

yes I know -55db is I think around 399 microvolts which will flatten
any receiver,



I sure hope not; there are many signals coming down my antenna that are 
that strong.  In fact, my 440 repeater 13 miles away is at about that level 
at my antenna connector.


Reminds me of a test I did with a GE MASTR Pro VHF receiver (stock - no 
preamp - ER-41C) and a GE MASTR II PLL exciter (stock - 200 mW output) 
and a tee connector.  Receiver and exciter on each end of the tee (with 
short cables) and antenna/service monitor on the center.  As I remember, 
the frequencies were about 6 MHz apart and the 'repeater' would duplex 
reasonably well considering no filtering was used between the units.  Of 
course, I'm not saying there wasn't desense, but it worked - pretty well.


Obviously, the 200 mW was split into two paths and who knows how much 
was hitting the input port of the receiver, but lets say half of it was 
- 100 mW.  That power level is +20 dBm.   I can almost guarantee you 
that transmitter side band noise is what created the desense - not the 
shear power of the transmitter.  +20 dBm is 2,240,000 ?V or 2.24 volts 
of RF.


My receive antenna for the UHF remote receivers is top mounted across 
the tower face beside the VHF stick.  The VHF repeater runs 250 watts.  
4 watts of VHF power appears at the splitter (in the shelter - including 
feedline loss) which feeds the 4 UHF receivers.  The splitter (old CATV 
type) gets warm - you figure out how much VHF power is getting to each 
UHF receiver .


Kevin Custer

Re: [Repeater-Builder] 6 Meter Heliax Duplexers

[Kevin Custer]

Tim wrote:
> I think I've found a way to make it work.
>
> 1.  Got some brass tubing that is just about the same
>   diameter as the rg-8's center conductor & poly.
>   (might have to use some silicon grease to make it
>   slide a bit easier).

Tip...

I made a lot of antennas using hobby brass tubing.  I found that the 
center conductor and dielectric from quality RG-8 was slightly too large 
for the (5/16"?) hobby brass, HOWEVER, the center conductor and 
dielectric from legacy Radio Shack solid dielectric coax sleeved in with 
a nice snug fit.  The RS coax was of poor quality (in my opinion) 
because of the lack of adequate shielding, but this made good use of 
otherwise poor quality cable.  YMMV.

Kevin Custer

Re: [Repeater-Builder] MASTR II LOW BAND TUNING

[Kevin Custer]

Jeff DePolo wrote:
> I took a quick look at them, and what stands out like a sore thumb is 1.6 db
> insertion loss with a 150 watt power rating.  That means they'll be
> dissipating close to 50 watts in such a small package.  Doesn't give me a
> warm and fuzzy feeling... 
>
>   --- Jeff WN3A

Warm likely - maybe even hot,  but certainly not fuzzy.   - - Sort of 
like a cheap soldering iron.

Kevin

Re: [Repeater-Builder] Quantar Simulcast Issue

[Kevin Custer]

Jeff DePolo wrote:
> To get the RF phase accuracy you're implying that is required would mean
> that everything in the RF path would have to guarantee that phase
> relationship.  That means the same length RF interconnect cables inside the
> cabinet, same RF feedline length (or full-wavelength multiples thereof),
> same antenna type, etc.  Even if you could guarantee that kind of accuracy
> at the time of installation, thermal effects would quickly throw it way off
> (cables expanding/contracting with temperature for example).  Not to mention
> the propagation delay will vary a whole lot with temperature, humidity, etc.
> Just not gotta happen


And in practice, we know it isn't going to happen, so we purposely set 
the frequency difference between transmitters that overlap in coverage 
to about 20 Hz.  This negates most negative effects of two transmitters 
being real close but not dead on frequency or angle. 
Transmitters that are very close to one another will cause PL tone 
decoders in the users radio to not reliably open, not to mention to 
weird audio artifacts that are produced/heard.  At 20 Hertz, or so, 
CTCSS tone decoders work fine and radios' speakers don't emit a horrible 
beat note.

Kevin

Re: [Repeater-Builder] Simulcast Information on-line

[Kevin Custer]

skipp025 wrote:
> For those of you who'd like to see a few different examples 
> of various Simulcast Systems explained. 
>
> http://www.simulcastsolutions.com/case-studies.htm

Another explanation is available here:
http://www.repeater-builder.com/k7pp/index.html

Kevin Custer

Re: [Repeater-Builder] Astron RS50 Power Supply

[Kevin Custer]

Jeff DePolo wrote:
>  
> Everyone is entitled to make an ass out of himself now and then, but you're
> abusing the privilege...


Now that's funny...

BTW:  I had set the dudes posting privileges to "Moderated", but Scott 
decided to toss him - - Scott wins.

Onward and Upward.
Kevin Custer

Re: [Repeater-Builder] Lost 10 volts in a Master II UHF Repeater

[Kevin Custer]

Scott Zimmerman wrote:
> <--- That reminds me of a story Kevin told about when he worked in a CB 
> shop.
>
> A guy came in and said he mounted his radio and now it didn't work. 
> Kevin went out to investigate and found the guy drilled two holes right 
> straight through the radio and used two lag bolts to fasten it to the 
> dash!! It sure wasn't going anywhere in a crash!!


Yup..Radio was a week old - and totally ruined. 

Dude comes in to the CB shop I was working at when I was 14; wants a CB 
right now, and doesn't have the time to have it installed.  So, we ran 
the power and antenna wires and laid it on the passenger seat until he 
could return to have it mounted.  He comes back a week later to 
'complain' that the radio no longer works.  He had taken some time at 
his delivery lay-over to professionally mount his new radio to the under 
side of the dash. 

I went out and saw the bolt heads (with nice washers I might add) on the 
under side of the case of the radio.  He drilled 2 mounting holes right 
through both sides of the case (and circuit board) and mounted that 
radio to the dash.  It sure looked good, and it wasn't going anywhere, 
but the radio failed to operate after he wiped out most of the VCO and 
audio amplifier components with the 1/2" drill bit.

True story - sigh

Kevin

Re: [Repeater-Builder] Re: Micor ?

[Kevin Custer]

Ryan,

A,  Your problem is likely not the Station Control Module.  I'm just 
guessing, but I'd say JU401 needs installed on the exciter. 

This circuit is sort-of a loop back - meaning PTT cannot occur on the 
exciter unless Keyed A+ is delivered to the exciter, and brought back to 
the SCM, where it is used to create Keyed A-.  This is done so the 
exciter will not transmit until the channel element has had time to be 
enabled and become stable.  Keyed A+ is either run through the PL 
encoder (which someone my have removed) or through JU401 if the encoder 
is absent.

See if the jumper has been cut or removed on the exciter.  If so, 
replace it or install a PL encoder board.

Kevin


> Hi Kevin and group,
> I get PTT on pin 9 and 10. before i replace parts the manual says about Q8 
> and a CR5 as problems any thoughts ?
>
> Ryan n3ssl 
>
> --- In Repeater-Builder@yahoogroups.com, Kevin Custer  wrote:
>   
>> n3ssl wrote:
>> 
>>> Hi Group,
>>>
>>> I have a Vhf Micor unified station that was modfied prior to ownership. The 
>>> Mods for the Station control module were performed as on the RB site. The 
>>> problem I am having is there is no PTT on pin 5 of the back plane. Is there 
>>> something i should check ? The Station control module is the TLN 4635
>>>
>>> Ryan n3ssl 
>>>   
>> Ryan,
>>
>> Can you PTT from any of the other inputs?
>>
>> Kevin

Re: [Repeater-Builder] Micor ?

[Kevin Custer]

n3ssl wrote:
> Hi Group,
>
> I have a Vhf Micor unified station that was modfied prior to ownership. The 
> Mods for the Station control module were performed as on the RB site. The 
> problem I am having is there is no PTT on pin 5 of the back plane. Is there 
> something i should check ? The Station control module is the TLN 4635
>
> Ryan n3ssl 

Ryan,

Can you PTT from any of the other inputs?

Kevin

Re: [Repeater-Builder] Linear Modulation EPROM files

[Kevin Custer]

DCFluX wrote:
> Can you power one up and see what the display says?
>
> Mine all show  and have a solid squelch that blinks off about once
> every 2 seconds.  Maybe there is something critical in the RAM module
> and the battery went dead.
>
> As I understand it there is an elaborate power up thing that gets
> displayed. and the switches should be functional. Holding mode down
> during power up should make the module run in a diagnostic mode.

Replied directly

K

Re: [Repeater-Builder] Linear Modulation EPROM files

[Kevin Custer]

DCFluX wrote:
> Working on converting a Linear Modulation  (Similar to ACSSB) 220
> Trunking repeater to Amateur Radio applications, but I need your help.
>
> I am experimenting with a LMC3005 repeater, also known as
> the Viking LX. I believe the RF and Signal processing boards are similar
> to the ones found in the LMM3115 mobile radio if that is what you
> have.
>
> Possible suspect brands of manufacture are:
> Intek Global
> Linear Modulation Technology
> Midland
> Securicor Radiocoms Pty. Ltd.
> RoameR One
> EF Johnson
>
> For some reason the repeater I have is missing the EPROMs from the
> Trunking Channel Controller module. It is the one that has the 7
> segment display and LEDs that sits in between the Exciter and Receiver
> modules. It is labeled They are labeled IC13, IC20 and IC21. 13 and 20
> should be a 27C256 and IC21 is a battery backed up clock module
> M48T18.

The LM/Viking LX Repeater (relabeled Securicor) I have has IC20 missing 
as well, but does have IC21- the clock module, and IC13 the EPROM.  It 
was supposedly operational when it was pulled from service, so I don't 
believe you'll need IC20.  I don't have any way to read them, but if you 
want, I'll pull and send them to you as long as I get them back.

Kevin

[Repeater-Builder] The Repeater Builder website....

[Kevin Custer]

So, here is the conclusion to today's events following the supposed 
repeater-builder.com site hack.


We have processed your request for review of your website, 
http://repeater-builder.com/. At this time, none of our data partners 
are reporting badware activity related to the site. Any warnings 
displayed by our partners about your site have either already been 
removed or should be removed shortly. In addition, the report(s) about 
this site in StopBadware's Clearinghouse have been moved from "active" 
to "archived."


For tips on keeping your website clean and secure, please visit: 
http://stopbadware.org/home/security


If you have further questions, please visit our online help & 
discussion community: BadwareBusters.org .


The StopBadware Team



The whole thing was a BS scam to try to gain business from a bogus warning.
So much for Google being your friend  Webmasters BEWARE!

Oh yea - Firefox resolves the site again.

Tell everyone they are safe now (you do feel safer now don't you?)



W3KKC
..  Long day, I'm going to bed.

Re: [Repeater-Builder] Problems reaching the RB website

[Kevin Custer]

La Rue Communications wrote:

Right on Kevin -
 
Thanks for staying on top of this. I checked all my browsers, I have 
about 10 on both my Mac and PCs and got no errors.


Warning page redirects are only happening to people that have or use 
(subscribe to) Google add-ons and similar software.  The RB site has 
been tested by several others and unless there is infection deep within 
the site (and there could be, but I really don't think so), no one 
should be at risk for navigating the site.  AVG link scanner says the 
site is safe, as well as other anti-virus and anti-malware services 
being run on the site.


The message I got from Google used wording like "The site /may/ be 
compromised" and "The site could have been mis-identified". 

Again, all of my webmasters are doing what we can to insure the site is 
safe to navigate.   I'll post any updates I have as I can.


Thanks everyone for your understanding...
Kevin

[Repeater-Builder] Problems reaching the RB website

[Kevin Custer]

I got several personal emails about not being able to reach the Repeater 
Builder site this morning.  Google has reported the site has been hacked 
and most browsers redirect you to a big warning page.  I scanned the 
supposed infected pages,  http://repeater-builder.com and 
http://www.repeater-builder.com with AVG link scanner  
http://www.avg.com.au/resources/web-page-scanner/.  I also looked at the 
.htaccess file and other content to make sure there isn't anything going 
on.  I found NOTHING that resembled malware or suspicious links, 
forwarders, scripts, etc.  I have submitted for re-evaluation on both 
Google and another independent evaluator - stopbadware.org.  If you look 
at the help sites, this BS generates a LOT of business for companies 
that scan sites for money. 

We shall see what the re-evaluations say.   Realize I changed NOTHING on 
the website, and I believe it has been clean all along. 

If the site proved to be clean on these subsequent scans, I can only 
assume there is collusion between Google and businesses that scan 
websites for money.  I have no proof of this - it's just an observation.

Kevin

[Repeater-Builder] Nice article on the Molotora Gontor

[Kevin Custer]

Bob Meister has written a nice article on the Molotora Gontor for RB.
http://www.repeater-builder.com/molotora/gontor/gontor.html

Thanks go out to Bob for his efforts!

Kevin Custer

Re: [Repeater-Builder] HP E8285A Cellular Test Sets

[Kevin Custer]

Dawn wrote:
> I checked the archives and noticed there was scant mention of these units. 
> For the money, these seem like a dream come true. From what I understand, 
> once set up in the test mode, they have most all of the function of the 
> HP-8920 series minus the following:
>
> No Edacs,LTR or any signaling formats or DPL except raw tone generation and 
> DTMF.
>
> Three watt limitation
>
> No frequency count on Spec A screen
>
> Pre-set squelch or none.
>
> Otherwise these function as a complete service monitor from 100kc-1 gig and 
> another second band to 1.7gig.
>
> I also gather that with a suitable thruline or similar power attenuator, the 
> wattmeter indication can be adjusted to read correctly removing the 3 watt 
> limitation.
>
> If all this is correct and with an external multi format tone generator such 
> as Motorola's or Cromco's and a Multiformat tone reader such as Opto's or 
> Connect System's boxes, you pretty much have the entire enchilada por poco 
> dinero.
> Am I missing something or is this quite possibly a fantastic deal due to the 
> shere amount of orphaned CDMA/TDMA test sets since GSM?
> Anyone have one of these? The 100 kc-1 gig isn't part of Agilent's specs. Is 
> this a hack or was this a function of earlier units?
>
> Any info or caveats appreciated on these units.


I bought one recently on eBay.  It had, what the seller referred to as, 
a 'jittery' display.  It also has the desired "Option 102" (spectrum 
analyzer / tracking generator.
They can be branded either HP or Agilent.  Some later models aren't able 
to tune below 800 MHz, as the downconverter and input modules 'may' not 
be calibrated by the factory for operation in this portion of the 
spectrum.  Also, the firmware on the newer units doesn't support 
operation below 800 and some other functionality.  The unit I was 
watching looked pretty good, had 102, and I took the plunge...

There is a guy in Lakewood NY that is very knowledgeable on HP / Agilent 
equipment (as well as some other brands).  His name is Rick Bowman, and 
he owns Amtronix Instruments.  Before purchasing my unit, I asked Rick 
all of the same questions you are wondering about.  Basically, if you 
buy one from eBay or another surplus source, it isn't known if you will 
have a 'good one' until someone like Rick takes a look and determines 
what it needs.

I lucked out.  Even though the unit I have has a serial number above 
what Rick considered would be okay for operation below 800, mine didn't 
require a different downconverter or input module.  It did require a 
firmware downgrade and I had him run it through calibration.  The 
display jitter was caused by some bad capacitors on the display board.  
If you have one of these and the display is jittery, don't run it as it 
will eventually take out the regulators on the display board.  My 
display is a little burned - common I'm told for these machines.

Rick has these units already 'fixed up' from time to time for around 
$700.00.  He is currently out of stock on these, but expects to be 
getting some in soon.  My suggestion is to get on his waiting list.  
Rick is a good guy to deal with.  His prices are fair and his work 
second to none.

In the past, I have used the HP 8920A/B and my HP E8285A is very similar 
in operation.  Basically it doesn't have the items you mentioned above, 
but does have a few things that the 8920 doesn't.  It is a good machine, 
and for the price, you can't beat it for a good monitor.  I'm told all 
E8285A's have the high-stability reference oscillator.  Here's a page 
that does a comparison between them:
http://www.amtronix.com/e8285a.htm

Rick can be reached at:
http://www.amtronix.com/

Kevin Custer

Re: [Repeater-Builder] Doug Hall 4RV Voter

[Kevin Custer]

Nicholas Cerreto wrote:

Hello!
 
Does anyone have a service manual for the Doug Hall Voter 4RV Voter?


Not likely...A manual with schematic is not offered by Hall.
If you need it repaired, try shotgunning the IC's or send it back to 
them for repair.


Kevin Custer

Re: [Repeater-Builder] Service Monitor (HP) calibration

[Kevin Custer]

James Delancy wrote:
> Does anyone know of a place relatively close to CT (or NYC metro area) 
> that does service monitor calibrations?

While not close to your area, here's a place that will do it right, and 
treat you right:
http://www.amtronix.com/

Rick specializes in HP / Agilent as well as others.

Kevin Custer

Re: [Repeater-Builder] Low Band Micor mobile not making power

[Kevin Custer]

tahrens301 wrote:
> Hi all,
>
> Working on a micor mobile to be used as a 
> repeater (only using the exciter/control board/PA).
>
> Was going through it, and am only able to get
> about 75 watts out of it with the exciter on 53.7.
>
> The exciter is putting out 0.3 watts... a bit more
> than most exciters I've seen, but they were high band.


I'd expect to only see 75 watts out of a 110 watt PA if you only have 
300 mW of drive.  Low Band exciters usually have about 600 mW leaving 
the exciter on frequencies within original specification, and it's 
common to see 150 watts out of a Low Band PA.

Under drive can be a bad thing.  I'd look at it with a spectrum analyzer 
and make sure it isn't spurious because of the 3 dB of under drive.  It 
probably isn't, but I'd check it anyway...

Kevin

Re: [Repeater-Builder] Low Band Micor mobile not making power

[Kevin Custer]

Kris Kirby wrote:
> IIRC Motorola usually used about 1W at the exciter to drive the PA to full 
> power. 
>
> --
> Kris Kirby, KE4AHR
> Disinformation Analyst

Not on the MICOR line.  All are 400 mW out of the exciter regardless of 
band.  Low Band exciters usually make 600 mW, but their spec is 400 mW.

UHF Stations takes the 400 mW at the VHF exciter and makes 1 to 2 watts 
for the PA as a function of the tripler.  The UHF MICOR mobile is 
similar, but different.

Kevin

Re: [Repeater-Builder] Pion and Simon - the rest of the story....

[Kevin Custer]

Tedd Doda wrote:

Kevin Custer wrote:

  
John paid with an eCheck, which is subject to delays just like a check 
that clears the the bank.  There are ways to transfer money to PayPal 
instantly, like instant transfers from checking and savings accounts.



In all the years (since 1999) of selling on Ebay, I've never run into a 
e-cheque.


Lucky me, I guess :)


The link below will explain the differences, advantages, (and obviously 
in this case, disadvantages) of using an eCheck.

https://www.paypal.com/helpcenter/main.jsp?t=solutionTab&solutionId=13054&cmd=_help-ext

John's delay won't be substantial, only a few days.  He is wanting to 
receive his controller before the 20'th of this month.  I see no reason 
why he won't get it by then.


Kevin Custer

Re: [Repeater-Builder] Pion and Simon - the rest of the story....

[Kevin Custer]

Tedd Doda wrote:


But John said he paid with Paypal?


Not all PayPal transactions are instantaneous. 

John paid with an eCheck, which is subject to delays just like a check 
that clears the the bank.  There are ways to transfer money to PayPal 
instantly, like instant transfers from checking and savings accounts.


Kevin Custer

[Repeater-Builder] Pion and Simon - the rest of the story....

[Kevin Custer]

As promised, here are two replies I received about 30 minutes after 
sending an email to Al and Elizabeth:



Kevin, I received an e-mail from him just today.
I sent him a reply within minutes.  I just read his response.  I hope 
the attached file explains everything, but if not, please feel free to 
inquire further.


And by the way, thanks again for your site.

Best regards,
Al KK7XO


And I was CC'd on his response to John,

John, it's unfortunate that you put a complaint on the repeater 
builder site.  I answered your e-mail inquiry within minutes of 
reading it, as I do with virtually every e-mail I receive.


Your check should clear as early as tomorrow according to the 
information I have.  We have no control over how the check is 
handled.  Apparently it has to do with the fact that there is an 
international transfer of funds and the related monetary conversion 
from Canadian funds to US funds.  I will mail your board as soon as we 
have confirmation.  It usually takes 3 days or less for the package to 
arrive after we mail it.


I hope this is satisfactory.  I'm sorry you had difficulty purchasing 
our board.  We will do everything we can to make sure your order goes 
out promptly as soon as we get confirmation of the transaction.


73 de Al KK7XO 








I have sent a message to Al and Elizabeth as well - asking for help 
here.  Maybe your messages are getting caught in a SPAM filter or 
something.  This is not their normal practice and I can only assume 
your messages are not getting delivered.


I'll let you know when I get their reply.

Kevin Custer
List Owner

Re: [Repeater-Builder] Pion and Simon

[Kevin Custer]

John J. Riddell wrote:


Thanks, James.but you'll recall that my question was for a phone 
number.

I sent two E mails with no reply..to the address shown...


I have sent a message to Al and Elizabeth as well - asking for help 
here.  Maybe your messages are getting caught in a SPAM filter or 
something.  This is not their normal practice and I can only assume your 
messages are not getting delivered.


I'll let you know when I get their reply.

Kevin Custer
List Owner

Re: [Repeater-Builder] Writing Guidelines

[Kevin Custer]

Kris Kirby wrote:
> I see the guidelines for writing; what are the guidelines for scanning 
> documents?

PDF please.   Make the file as small as possible, BUT, don't skimp 
terribly just to save server space.  There are many methods in which to 
scan and save - trial and error will reveal what you like and what you 
don't.

Kevin

Re: [Repeater-Builder] Re: 200 watts on a repeater transmitter - was something else...

[Kevin Custer]

Steve wrote:
> It seems logical that if a rptr tx is running 200w, and the mobile is running 
> say 50w then it is going to be one way ie mobile hears rptr but rptr don't 
> hear mobile too well

Common misconception. 

Lets say the mobile radio has a receive sensitivity of -116 dBm and 50 
watts of transmitter power.  The repeater has a receive sensitivity of 
-122 dBm - how much power will it take to balance out the receive 
advantage of the repeater?  If you said 6 dB, you are correct.  50 watts 
with a 6 dB improvement is 200 watts.

I have seen several VHF and UHF repeater systems with -125 dBm actual 
sensitivity on air - connected to the antenna and duplexing.  You do the 
math...

400 watts is the answer.

The original poster mentioned an LDG voter and remote links.  If the 
repeater has remote receivers that will increase the distance of 
operation from the transmitter, he'll need all of his 200 watts.

Kevin Custer

Re: [Repeater-Builder] Re: 200 watts on a repeater transmitter - was something else...

[Kevin Custer]

Kris Kirby wrote:


I think that one would be better served by choosing an antenna 
appropriate to the purpose of the repeater. If you need urban coverage, 
choose an antenna with more null-fill, or less gain. 

If you have to pay for power (or make your own power!), you'll spend 
more time working on an antenna that will cover what you need so your 
transmitter can be ten watts or less.



The antenna doesn't know if it's receiving or transmitting - so the 
antenna has absolutely nothing to do with transmit or receive balance - 
which is now the subject.


Kevin Custer

Re: [Repeater-Builder] 200 watts on a repeater transmitter - was something else...

[Kevin Custer]

We have been over this many times.  If a system is balanced with a 
receiver at -116 dBm running 50 watts of power, then it will be balanced 
with 200 watts and a properly deployed preamp adding 6 dB of gain.  The 
added power level on the repeater transmitter helps with noise that is 
common in urban locations experienced by the mobile; noise that is not 
experienced by the repeater receiver.  Most commercial vendors will tell 
you a system is balanced with 100 watts and a receiver at -116 dBm.  
That mentality would require 400 watts to remain balanced with a mere 6 
dB (easy) preamp improvement.

Why is it that folks think that if you are running more than 100 watts 
of power that AUTOMATICALLY it qualifies as an alligator?  I have two 
repeaters that run in excess of 200 watts - neither of them have EVER 
been considered an alligator.  In fact, both are nicely balanced with a 
rural run 50 watt Japanese mobile.

Kevin Custer




> The question that pops into my mind concerns the proposed 200 watt power
> amplifier.  I have to wonder where the notion to run an alligator system
> originated.  I see four possible answers:
> 1.  We have this 200 watt amplifier, so we are duty-bound to use it
> regardless of whether it is necessary or not.
> 2.  We subscribe to the policy that more power is always better, and it
> always increases coverage.
> 3.  We have performed a thorough analysis of coverage, and have determined
> that less power will result in insufficient coverage.
> 4.  We know that 50 watts is enough, but a real powerhouse station will give
> us bragging rights.
>
> Once again, I must recall my favorite repeater-coverage dictum:  Repeater
> coverage is determined by receiver performance, not by transmitter power.
>
> 73, Eric Lemmon WB6FLY

Re: [Repeater-Builder] Re: Hamtronics versus Commercial (Kenwood) Repeater Selection

[Kevin Custer]

skipp025 wrote:
> The more famous surplus commercial radio 224 MHz conversions 
> replace the PA with a Hybrid RF Amplifier Module... wonder if 
> they also include SWR Protection? 

"They" don't - at lease not all do, but in the case of the MICOR mobile 
- the power set functionality (power level setting, power leveling, and 
SWR protection) is retained.  This is because the VHF directional 
coupler works very well at 220 MHz, and if done right, can still drive a 
power transistor; which then controls the hybrid module.  Scott 
Zimmerman/Repeater Builder builds a nice PC interface board that allows 
all of this to happen easily:
http://www.repeater-builder.com/products/ampbd.html

The picture on the right (MICOR mobile installation) shows the TO-220 
pass transistor and you can see the little purple lead from the power 
set board coming through the PA wall and connecting to the base of the 
pass transistor.  Because, in a MICOR, the power set control is done 
with circuitry that is separate from power amplifier board - this 
protection is not difficult to maintain.  The interface board allows 
easy installation of the hybrid and even incorporates the reverse 
polarity diode that gets removed when you discard the original MICOR VHF PA.

In the case of the GE MASTR II, power control is done with a simple pot, 
and all SWR protection, leveling, etc. is bypassed/eliminated - at least 
with this interface board.  Maybe someone has hacked the MASTR II PA to 
allow for the incorporation of its protection in a 220 conversion - but 
I have never saw it if it has been done.

Kevin Custer

Re: [Repeater-Builder] Micor Stock Power Supplies

[Kevin Custer]

Sorry, I cannot answer that question.  My reference was more toward the 
replacement of an existing linear supply or new installations such as 
GMRS or Amateur Radio systems - repeater or otherwise.  Whether or not 
their rule applies to newer Motorola or other commercial radio 
manufacturers -  I'm not certain.

I am told that Motorola offers alternative powering methods to systems 
that normally come with switching supplies.  I'm not totally sure 
why...  possibly there are companies that aren't totally sold on 
"switcher" technology?

Unfortunately, like with so many things, price dictates quality.  If you 
buy a JAN crystal, be prepared to have it drift all over the place.  If 
you buy a cheap switcher, be prepared to have it throw garbage out all 
over the place.  While the better switchers like Samlex and DuraComm are 
good performers, many of us will buy something cheap.   With education, 
more of us will buy the better product, like International Crystals with 
temperature compensation performed by them.

Kevin


> So, these tower management companies no longer allow the latest Motorola and
> Kenwood stations- which come with switching power supplies- to be installed
> at their sites?
>
> 73, Eric Lemmon WB6FLY
>
>
>
>
>   
>
> There are a few tower management companies that I know of that won't let 
> you install a switcher because of the possibility of interference. The 
> same companies also do not let anyone install LMR coax onto the site.
>
> I'll be interested to see the results too, Bob.
>
>   

Re: [Repeater-Builder] Micor Stock Power Supplies

[Kevin Custer]

You wrote:
> Switchers -as a class- are more efficient and reliable than linear supplies.

As a Class...
More efficient - yes,  More reliable - that's debatable. 

In the two-way radio world, linear supplies are the rule, switchers are 
the exception.  In 25 or 30 years, we'll see if switchers are 'really' 
as reliable.   In my experience with switchers (as a class), they are 
hard on filter capacitors, with failures of them way before the normal 
'dry out' time - many times in just a few years. 

There are a few tower management companies that I know of that won't let 
you install a switcher because of the possibility of interference.  The 
same companies also do not let anyone install LMR coax onto the site.

I'll be interested to see the results too, Bob.

Kevin

Re: [Repeater-Builder] Re: Micor UHF Repeater Base 9.6 vdc current requirement?

[Kevin Custer]

DCFluX wrote:
> How about a 7809 regulator IC with a 1N4004 diode in the ground leg to
> raise the output voltage to 9.6V?

There is nothing mysterious about 9.6 volts.  It could be 9.00 volts 
10.00 volts 11.00 12.00 volts or *anything* in between.  The part that 
is critical is that it is stiffly regulated.  Something less than 10.6 
volts was chosen because that is the point where a lead acid battery is 
technically totally depleted.  This means the critical circuitry 
(oscillators, multipliers, etc.) are always fed with stable power to the 
point where the battery is dead.

In a station, the 9.6 volt circuitry *could* be run from 12 volts, as 
long as its regulated.  I'm not suggesting someone does that, because 
the circuits were optimized for 9.6 volts, but I'm trying to make a point.

If it were me, I'd just use a 9 or 10 volt three terminal regulator 
(7809 or 7810) and skip the whole LM-317 or diodes in the ground leg 
deal.  It only serves to make the circuitry more involved , harder to 
mount, and for NO advantage whatsoever.

Kevin Custer

Re: [Repeater-Builder] Re: Key Collection

[Kevin Custer]

skipp025 wrote:


Oh yeah..?  Got an Allen B. Dumont, (Fred) Link key in that collection?


My father had a Link FM transmitter on VHF - used a pair of 2E26's in 
the final.  It was paired with a receiver, but I don't recall what it 
was.  The receiver would get so hot it would burn up the tube sockets.
Both were in a small Link cabinet, but the door wasn't lockable, as I 
remember.


We did have a small/unstable DuMont oscilloscope - it sure wasn't a 
Tektronix.


Kevin

Re: [Repeater-Builder] "Bend" an ICOM a little further

[Kevin Custer]

> Doug wrote:
>
> Jared;
> You need to warp 4khz not 400hz... If they were made up for 146.01 I would 
> assume that they can do that. 
>>  
>> Jared wrote:
>>
>> I just need the crystal to go up a hair more (400 Hz on the crystal freq).
>> 

In Jared's defense, he did say "on the crystal frequency"
He needs to go 3600 cycles higher on the channel, which relates to 400 
cycles at the crystal because the LO multiplier in a VHF MASTR II 
receiver is 9
400 cycles (400 more than the present netting excursion, that is...) at 
the crystal frequency is going to be difficult without breaking the 
oscillator - IMHO.

Kevin

Re: [Repeater-Builder] 85VAC to 12 VDC?

[Kevin Custer]

AJ wrote:

Gents -

I completely spaced using existing CATV gear - I have a pallet of 
Motorola/GI minibridger housings with just the power modules in the lid.
I'll see what I can do to test this out over the week and try to 
report back - Pretty sure I can fit an entire remote receiver in to a 
MB housing...


AJ,

Just make sure the model power pack you have will take 90 VAC.  Most 
Jerrold/GI/Motorola MiniBridgers up to and including 750 MHz were 60 
volts.  If you are lucky, you have 60/90 units.
Also, I'd be interested in a few MB housings if the inserts aren't 
stripped and were never water damaged.  I have a few castings that 
aren't good enough to be put into the field, but have good looking guts.


Thanks!

Kevin

Re: [Repeater-Builder] 85VAC to 12 VDC?

[Kevin Custer]

Eric Lemmon wrote:
> AJ,
>
> The obvious solution is to connect a commercial switching power supply-
> definitely NOT a linear supply- across the AC source.  Most Samlex, Astron,
> and DuraComm switchers can work wonders in such an environment, where
> conventional linear power supplies will surely fail.  Don't use a larger
> (higher capacity) power supply than you really need; in this case, larger is
> not better!

Be careful here...   The output of a CATV power supply is not a sine 
wave.  I'm not sure how these commercial switchers would react to the AC 
available from the CATV line.  Certainly while switching supplies are 
used in the CATV industry to power the amplifiers, nodes, and telemetry, 
I don't know if they are made exactly like the ones fed from commercial AC.

It would be much better if he uses a power supply intended to be 
connected to the CATV line.  These can be scavenged from working surplus 
CATV equipment.  Several of the ones I'm familiar with can supply an amp 
or two at 24 VDC, and that used to feed a regulator or charging circuit 
for 12 volts.

Kevin

Re: [Repeater-Builder] 85VAC to 12 VDC?

[Kevin Custer]

AJ wrote:



We've been given the opportunity to setup a remote receiver at the end 
of local local cable television provider's plant on the hill to help 
with coverage. Powering is the only issue we're running in to - 
currently the only power available within 6 pole spans is the 90 V AC 
plant power across the CATV coax. They've offered to cut in a power 
inserter at this location to feed up to 4 amps of 90 VAC to us 
(roughly 85 VAC at that point in the plant) - what is out there for a 
reasonable cost effective solution to convert this to 12 VDC?


This stub of plant does not have RF across it, nor will it any time 
soon (RF removed when fiber backbone was overlashed on the same pole 
line). Our first concern was leakage but that shouldn't be an issue.


Build new coax plant as close to the desired location as possible.  Have 
the CATV company feed this coax with the power inserter.  The power 
inserter will allow the extraction of power without upsetting the RF if 
it is ever re-activated.  Have the lineman cut in an old CATV amplifier 
housing with a mating power pack at the end of the coax line. Use the 
power supply module (power pack) inside the amplifier to convert the 
available AC to 24 volts DC.  Then, use a regulator to cut the 24 down 
to 12.  Obtain a few spares of the power pack so when lightning does its 
thing, you can get it back up and going.


Another option to continuing the coax plant is to have them cut in the 
power inserter and then run some kind of power line (duplex cable) and 
use this line to feed a CATV power pack housed in a weather proof box.  
You can make the AC go much farther then the DC.


I had a ham remote receiver location work for many years using this 
principal.  The power availability wasn't nearly as substantial as what 
you have.  I was at the end of the line in a 60 volt plant.  Nearest 
power supply was 2 miles away and it fed the microwave receive site on 
the same tower I was on.  I had to be careful not to drag the AC down 
too far or the receive site would go out.  Available AC was about 45 
volts and I used it to supply a CATV amplifier switching power pack (24 
VDC out).  The 24 volts fed a home brew charging circuit to trickle 
charge a 12 volt SLA battery.  Since the duty cycle was relatively low, 
there was plenty of time to recharge the battery after use.  The 
charging circuit was limited so even if the battery was stone dead, it 
wouldn't load the line too much that it outened the CATV microwave site.


Kevin

Re: [Repeater-Builder] Re: 11m Repeater - THREAD NOW CLOSED - W3KKC

[Kevin Custer]

RE: 11M Repeater

This thread is now closed.  Period.

Kevin Custer
List Owner

Re: [Repeater-Builder] Question for the Moderators

[Kevin Custer]

> Off topic but curious—my Google Alert for myself picks up every entry 
> I make on Repeater builders—I belong to a number of sigs on yahoo and 
> yours is the only one that Google finds, wondering if there is a sig 
> setting to prevent Google from finding the posts or if it is something 
> you like to have happen?

Andy,

It might be that it's not YahooGroups but rather the archive we have 
running for this list.

Kevin







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[Repeater-Builder] MICOR VHF receiver conversion to 2 Meter band - W3KKC winter special

[Kevin Custer]

I have decided to run another winter special on the conversion from 
high-band 150.8 - 174 MHz to 2 Meters (142 - 150.8 MHz) for the Motorola 
MICOR VHF receiver.
This special is offered two ways:
1 -  Just the helical resonator rebuild.
2 -  The complete receiver redo - (for high-side injection). 

I use new Silver Mica capacitors for the conversion.

Go here for more information and current pricing:
http://www.repeater-builder.com/rbtip/hs-coilinstructions.html

This pricing offer is also available for the conversion of 150.8 - 174 
MHz MICOR receivers to 222 - 225 MHz.
http://www.repeater-builder.com/rbtip/222sensitronRX.html

This deeply discounted pricing won't last forever.  Email me (directly 
please) with any questions.

Thanks,
Kevin Custer
kuggie [at] kuggie [dot] com

Re: [Repeater-Builder] Remote Receiver site

[Kevin Custer]

John Szwarc wrote:


I'm looking for some advice on constructing a remote receiver site.  
Ideally I'd like to have everything contained in one neat package just 
like at the repeater site.  We'd be receiving on VHF and transmitting 
the link signal on UHF back to the repeater site.Any thoughts?




Here's one...

GE MASTR II mobile - VHF Receiver, UHF "FM" Exciter (and PA if 
necessary).  Modify the audio path for flat audio and use an AP-50 for 
modulating the exciter.  If you want or need a controller, use one of 
the plug-in NHRC models.  Makes a nice little package and the sound will 
be excellent so the voter can do it's job well.  FM exciters on UHF in 
the MASTR II are a little scarce.  Use the following article to change 
the common phase modulated UHF exciter to FM:


http://www.repeater-builder.com/ge/mastrII/ap-50-fm-mastr2.html

Kevin Custer

Re: [Repeater-Builder] Longshot - Duke Energy/Texas Eastern

[Kevin Custer]

Jeff DePolo wrote:
> Does anyone have any two-way or microwave engineering contacts at Duke
> Energy or Texas Eastern (pipeline)?  

(If my memory isn't failing me  As I remember)
N3LIF Roy "Ed" Kern worked for Texas Eastern as a radio/microwave 
technician.   He is likely retired now.

Ed's in Green County - a repeater owner, and a nice guy.  I don't have 
any contact information other than the usual QRZ database.

> Along the same lines, does anyone know if they maintain their own microwave 
> network or if they subcontract the
> maintenance out?

As of 10 or 12 years ago - they utilized mostly in-house maintenance.  
That may have changed. 

If you can get a hold of Ed, he might be able to put you in contact with 
the folks in engineering.  KR3P might have Ed's email address he can 
relay via private message?

Kevin

Re: [Repeater-Builder] Mastr II mods and parts

[Kevin Custer]

Michael Cox wrote:

Ralph (and others)
 
So is there a IDA equipped version the controller?  If not, what does 
it mean that I have the IDA equiped version?


The IDA version of the MASTR II station was (originally) controlled by a 
means other than the usual plug-in cards.  What you bought is okay, but 
maybe not the preferred version for building a stand-alone repeater.



  Does that mean I need, for example, a different duplexer?


No, it has nothing to do with the duplexer - or anything RF for that 
matter.  When we build repeaters from surplus equipment, most of us rip 
out the original control circuitry and connect an after market repeater 
controller of some sort.  Many have mentioned the Pion & Simon units 
because they "plug right in", but not to the model of station you bought 
from eBay. 

That being said, either of the NHRC GE controllers will plug-in to one 
you bought.  The conversion you'll do to this station to make a repeater 
will likely more closely follow one written for a mobile - as you'll be 
using the Systems Board for controller interface if you choose a plug-in 
NHRC model.  If you choose some other controller - it'll have to be 
"wired in" making it a bit more difficult.


Kevin Custer

[Repeater-Builder] - was dispatch centers run through the internet

[Kevin Custer]

Kevin Custer wrote:
> and it seams 

Geesh   It seems that I got lost in the seams.

[Repeater-Builder] PLEASE READ - was dispatch centers run through the internet

[Kevin Custer]

Since we have veered off course with this discussion, and it seams that 
everyone that was interested gave an opinion, the THREAD IS NOW CLOSED.

Let's move on - back to subjects that are more on topic.

Thank you,
Kevin Custer

Re: [Repeater-Builder] dispatch centers run through the internet

[Kevin Custer]

The Internet is a shared medium.  A private WAN/LAN commonly utilizes 
fiber optic cable or licensed wireless networking to accomplish 
connectivity. While private systems can deliver Internet, it is not 
(necessarily) THE Internet.  Privately owned facilities like what many 
CATV, Phone, Internet, and combinations of them can have dark fiber or 
reserved virtual space that cannot get clogged with Internet overhead.  
The bottlenecking you might experience with facilities you cannot (do 
not) control can (will) be the downfall of such a system - unless a SLA 
can be gotten.  A SLA is a service level agreement in which a company 
guarantees connectivity - to some degree.  The more reliability the 
agreement extends - the higher the cost.

Kevin Custer

> Jed Barton wrote:
> tell me about this system a little bit. 
>   
>
> You'll note that the manufacturer is not suggesting that you utilize the
> Internet for this device. It is marketed for use on a private LAN/WAN.
>  
> Chuck
> WB2EDV

Re: [Repeater-Builder] 73 Magazine Archivers

[Kevin Custer]

AA8K73 GMail wrote:
> Here is an attached scan, 2.59 MB.
>
> Wow, an IMSAI for development.
> That brings back memories.
>
>
> Mike - AA8K

I remember reading it the first time around.  It was the work which 
eventually evolved into the Advanced Computer Controls (ACC) RC-850.

Fun reading...  Thanks Mike.

Kevin Custer

Re: [Repeater-Builder] Mastr II mods and parts

[Kevin Custer]

Michael Cox wrote:



Will this Duplexer work with the Mastr II repeater?
 
http://cgi.ebay.com/UHF-50W-6-CAVITY-DUPLEXER-FOR-REPEATER-FREE-TUNING 
<http://cgi.ebay.com/UHF-50W-6-CAVITY-DUPLEXER-FOR-REPEATER-FREE-TUNING_W0QQitemZ350300447727QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item518f88a3ef>



Sure, it would work.  It's a six cavity unit capable of providing enough 
isolation for desense free operation with a receiver of -116 dBm and a 
50 watt transmitter at a 5 MHz TX to RX spacing - as long as you aren't 
in a crowded RF environment.


Would I recommend it? - absolutely not.   As I and others have 
mentioned, a BpBr design, (like the WP-678 I referenced in an earlier 
mailing) would be a much better choice.  Why?  You'll likely buy a 100 
watt PA to go along with your recent repeater purchase, and likely some 
day you'll want to add a receiver preamp for hearing the real weak 
ones  The duplexer must provide enough RF isolation so the receiver 
can hear a very weak signal, while, at the same instant, putting out 
several watts from the transmitter so people can hear it.  Look at it 
this way, let's say you are listening for a pin to drop on a cushioned  
floor while someone is shouting into your ear.  The duplexer allows you 
to 'tune out' the person shouting - giving you the ability to hear the 
pin drop.  This can only happen because the transmitter and receiver are 
on two distinctively separate frequencies and the duplexer is optimized 
for those exact frequencies. 

There are places to save money where building a repeater is concerned.  
The duplexer is not one of them.  This doesn't mean you can't save money 
- you can.  The $250.00 WP-678 I spoke of in an earlier mailing was 
about $800 to $1000 new.  I'm recommending you buy $800.00 technology 
not $79.00 technology.


Kevin Custer

Re: [Repeater-Builder] Mastr II mods and parts

[Kevin Custer]

Michael Cox wrote:



Thank you for your help.  I appreciate it!  I've put a couple of 
questions inline below.


Well - you'll need a duplexer no mater the price...   

 
I was under the impression that if I had two antennas, I could get by 
without a duplexer.  Thanks for the heads up.


While two antennas will work, and you'd initially think there is a cost 
savings using two antennas, that isn't always the case.


The determining factor usually ends up being the length and size of 
feed-line necessary to get from the repeater to the antenna.  On UHF, 
unless the feed-line length is really short, you'll want to use some 
type of hard-line cable.  The cost of this cable, depending on type and 
length, can be costly.  It may be less costly to use one antenna and a 
duplexer then to install two antennas and have two runs of feed-line.  
In addition, you'll usually end up with a better balanced system using 
one antenna because using two can cause a disparity if both antennas 
don't have the exact same pattern - which could be difficult to achieve 
depending on the tower space available.  In installations where you have 
to pay rent on tower space - it's usually by far cheaper to purchase a 
duplexer.

RE: Power Amplifier

Are these what I'm looking for?


Generically - Yes.

  It looks like there is a UHF and a VHF version of the PA.  Is that 
correct?


Yes.

  Are they not compatible with each other?


No. 

VHF and UHF are two totally different bands.  You cannot use a UHF PA on 
a VHF repeater and vice-versa.  The third one you listed is a Mobile PA 
- not something you'll want. 

You want a UHF Station PA like the second one you listed - but it isn't 
the exact one either.  The one you want requires 200 mW of drive - not 
20 watts - but, the correct one looks very similar to the one in your 
number two listing.


I don't presently see a good candidate on eBay - but they show up all 
the time.



Duplexer - used WACOM Products WP-678 (or similar), also available
from eBay.

 
I couldn't find any on eBay.   Any guesses what I'd be paying for 
something like this?


$250 plus shipping.

 
 


Controller - I recommend a NHRC model that plugs into the
"Systems" board, or, one of the Pion & Simon models that plug into
the card cage.

http://www.nhrc.net/ge-stuff.php
http://www.pionsimon.com/products.htm

 
 
It looks like I can use the NHRC-4/M2 to make it a linked repeater.  
If I go with the Ham repeater, I'll most likely do that.  That would 
require, if I understand correctly, another radio connected in, so 
that will have to be done later with future funds. :)


Correct.
 
If I decide to make it a GMRS repeater, I won't have to worry about 
that and will go with the PSE508-2, as its a little less expensive.


Also a good choice.

Kevin

Re: [Repeater-Builder] Mastr II mods and parts

[Kevin Custer]

Michael Cox wrote:



I justed purchased a GE MAST II UHF repeater that has a 450-460 split
 
(see it at 
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230415711221&ssPageName=STRK:MEWNX:IT 
<http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230415711221&ssPageName=STRK:MEWNX:IT>)
 
 
I need to get a power adapter, a CWID,


You mean a Power Amplifier or simply called a PA. 


For a CWID, I recommend a real repeater controller.



 and, depening on the price, a duplexer.


Well - you'll need a duplexer no mater the price...   

  I'd like to modify this to use on either a GMRS repeater or a 40cm 
ham band.  This will be my first repeater.


I think you meant 70 cm ham band...  Modification is easy, as no RF mods 
need made for either use.  You just need to make it duplex.  Information 
on www.mastr2.com will help you there.


 
I'm assuming that I could get this 
http://www.repeater-builder.com/products/ampbd.html for the power 
adapter.


You could, but I'd just buy the right PA.  They are on eBay all the time. 


Do you have any recommendations for the duplexer and CWID?


Duplexer - used WACOM Products WP-678 (or similar), also available from 
eBay.


Controller - I recommend a NHRC model that plugs into the "Systems" 
board, or, one of the Pion & Simon models that plug into the card cage.


http://www.nhrc.net/ge-stuff.php
http://www.pionsimon.com/products.htm

Good luck,
Kevin Custer

Re: [Repeater-Builder] 220 repeater

[Kevin Custer]

Kevin Custer wrote:
> If you are into GE MASTR II radios instead of MICOR's, get yourself a 
> PLL VHF MASTR II mobile and use this conversion kit.  It's by far the 
> simplest conversion to the 220 ham band. 


Forgot the dumb link
http://www.repeater-builder.com/products/MIIconversionkit.html

Kevin

Re: [Repeater-Builder] 220 repeater

[Kevin Custer]

Dan Blasberg wrote:
> So it look like the general recommendation is a converted GE or Micor.
>
> That is kind of the direction I was leaning for the group.
>
> As for conversions, what are folks using for final amps?

Japanese Power Brick:
http://www.repeater-builder.com/products/ampbd.html

The Amp Board is a little circuit board that allows easy installation of 
a power module in a commercial band radio set.

If you are into GE MASTR II radios instead of MICOR's, get yourself a 
PLL VHF MASTR II mobile and use this conversion kit.  It's by far the 
simplest conversion to the 220 ham band. 

I prefer the MICOR, but there is absolutely nothing wrong with a MASTR 
II on 220.

If you'd rather not do the conversion yourself, Scott Zimmerman will do 
the conversion (GE or Motorola) for you:
http://www.repeater-builder.com/custombuilt/index.html

Kevin Custer

Re: [Repeater-Builder] 220 repeater

[Kevin Custer]

Dan Blasberg wrote:
> All right folks,
>
> For those that run a 220 repeater, what are you running as far as the  
> machine itself?
>   

MICOR VHF Mobile converted to 220 and duplexed to a repeater.

> A local group is looking to put a 220 MHz repeater on the air and  
> would like some ideas.

Here's how:
http://www.repeater-builder.com/rbtip/micor-index.html#220

Kevin

Re: [Repeater-Builder] ACC RC-85 QUESTION.

[Kevin Custer]

W8YSU wrote:
> Did anyone have any problems after the new year?
> Our controller will not take any codes to set the time and the date.
>
> also some of the voice messages are not playing right.


Here is your fix.  Remember to set the date back in time (to 1982) so it 
matches the correct Day of the Week.
http://www.repeater-builder.com/acc/acc-rc-85-96y2k.html

Kevin Custer

Re: [Repeater-Builder] Micor VHF 12W Amplifier??

[Kevin Custer]

tahrens301 wrote:
> .snip.
>
> I noticed that there is some silkscreen on the transmitter
> interconnect board (in the big hole to the right of the
> exciter) that says 12WPA.
>
> Didn't know whether Mot actually had put a low power amplifier
> into the space or not.
>
> Anybody know?
Hi Tim,

Yes, the 12 watt PA was used in UHF Stations in that location.  On VHF, 
the amplifier was usually mounted externally - usually in the form of a 
mobile heat sink mounted into the rack above the Unified Chassis.  The 
VHF 12 watt PA was commonly used to driver higher level tube-type PA's.

The MICOR series is not known for its efficiency, especially when 
commercial frequency range gear is tuned into the ham band without being 
properly converted.   That being said, there are several things that you 
can do to improve the power efficiency.  I don't believe the exciter 
itself is terribly inefficient, as it uses an unheated channel element.  
The tuning of the exciter into the ham band usually results in factory 
specification performance without modification, the exciter filter and 
PA are another story.  Modification of the exciter filter is usually not 
difficult, but the PA conversion can be.   So, since you only want a 
small amount of transmitter power, you might want to look into using a 
Japanese Power Brick for the PA; as they are usually very power efficient.

Repeater Builder makes a little circuit board to aide in the use of such 
a module for this type of purpose.
http://www.repeater-builder.com/products/

The receiver can be made to have better power efficiency by removing the 
B+ from the audio power amplifier.  Since these circuits are Class A/B, 
they draw current all the time.  In solar applications I usually place a 
SPST switch in the B+ lead to the audio power amp so the current can be 
cut off when it's not in use. 

There is a bunch of other circuitry that you might also consider 
eliminating, like any cards that may no longer serve any useful 
purpose.  Most repeaters can be built to deliver the necessities to a 
controller and the rest of the support circuitry can be gotten rid of.  
The NHRC Micro is a really good controller choice where power 
consumption is concerned.  The Micro installed in a MICOR allows solid 
RF technology to be interfaced with a modern controller. 
http://www.nhrc.net

Good luck with the project,
Kevin Custer

Re: [Repeater-Builder] Dead GLB 2 Meter Preselector

[Kevin Custer]

Joe wrote:
> We were just talking about the GLB preselectors recently.  Now I have a 
> dead one.
>
> I got a call that one of the local ham repeaters went stone deaf after a 
> lightning storm a couple of weeks ago.  I got time today to stop by and 
> found that the GLB preselector bit the dust.  I have used several of 
> these GLB preselectors and the ones that I have had apart use a Motorola 
> MRF901 transistor.  This one looks like it is using a different device 
> but there are no markings except for a "UF on one side.  There looks 
> like there are a couple of extra resistors on this one too.  This is a 
> very early version of the GLB unit.
>
> Any ideas?


My guess is it has a GaAs FET transistor as the active device.

Kevin

Re: [Repeater-Builder] MSTR II Mobile @ < 100W

[Kevin Custer]

tahrens301 wrote:
> Hi Folks,
>
> snip---
> Since I'm looking at using it as a solar pwr'd repeater, what
> is the best way to turn the power down (without making a bunch
> of spurs along with it)?
>   

Remove parts of the PA back to the desired output.  Match that output 
correctly to the LPF.
Here is a similar conversion where I took a 100 watt MICOR PA and sawed 
it in half - wound a custom output transformer - and coupled it to the 
LPF (low pass filter):
Scroll down in the page to see the picture and read the caption above:
http://www.kuggie.com/ahra/hmftinfo.html

OR
Use the exciter to drive a Japanese power brick.  Easily done with one 
of these:
http://www.repeater-builder.com/products/ampbd.html
Tastes great - less filling (cheap and spur free)

Remove the audio amplifier or put a switch in line with the B+ to it.

Kevin

Re: [Repeater-Builder] Re: The GLB Preselector- Preamplifier

[Kevin Custer]

skipp025 wrote:


Smart guy... cumbersome type of duplexer that worked 
fairly well. I survived living near Tonawanda NY in 
Cheektowaga where snow is no fun. 


Yes, Gil was a very smart guy - somewhat ahead of his time.
Here is the only information I can find (that is still available) about 
his untimely passing:

http://barra.hamgate.net/links/jun2001.pdf

Snow?  Oh yes, about 6 inches here is Friedens PA today - it was 50 
degrees yesterday.


Kevin

Re: [Repeater-Builder] Re: The GLB Preselector- Preamplifier

[Kevin Custer]

FWIW the BF981 is a dual-gate MOSFET, not a GaAsFET.  I assume Aria 
switched to a GaAsFET for the current-production unit?


Bob NO6B


I bought several of these when they were first on the market.

When this unit was first in production from Gil, he made it available 
like this:
Under 200 MHz was Bi Polar, over was GaAs FET  -  HOWEVER, you could 
custom order under 200 MHz the GaAs option.


The Bi Polar device was MRF-901 Motorola.

I don't know what the FET was...  I only ever owned one GLB 
Preselector/Preamp above 200 MHz (it was custom built for 222 MHz) and 
it had a MRF-901 in it  --  go figure.


GLB  stand for Gilbert L. Boelke W2EUP  inventor of the Hybrid Ring 
Duplexer - a design sold to Sinclair Radio Labs in Tonawonda NY


Kevin Custer

Re: [Repeater-Builder] Simulcasting of Repeaters

[Kevin Custer]

Hi Folks,

I know it's been done a lot, but I have no experience in
having two repeaters simulcasting.

Here's the info:

There is an existing repeater that has some coverage issues
in a neighboring area.  The folks in that area, while still
wanting to be on the same output frequency, will put a 2nd
repeater (with a different rx PL tone) up on a hill.

What kinds of issues will we see (from a user's perspective)?

The dispatcher will probably key up both repeaters at the same
time for tone-out purposes.

What kind of frequency tolerance is acceptable to make sure 
there isn't any hetrodyning?  (especially with PL tones &

tone-out tones).



Here is a good tutorial written by a good friend of mine, Pete Policani K7PP

Hope this helps...
Kevin Custer

"Properly" simulcast transmitters coupled with voted receivers really 
make a nice system; where the user is concerned







*SIMULCASTING*

By Peter Policani, K7PP

So, what's all this simulcasting that we are hearing about?
What's it mean and how does it work?
Does it really help?

These questions and many more have been asked since we started 
simulcasting on the K7PP repeater system.




Well, let's talk about something you have heard. Have you ever heard two 
stations on two meters doubling with each other. It happens all the time 
and all that is heard is chaos.


What would happen if two signals were transmitted on the same frequency 
at the same time?

Would there still be the noise and chaos?
Why?

You might think of a time when you were operating CW. You switch to 
calibrate mode and check the band edges. You zero beat the calibrator. 
What do you hear when you are zero beat? If you said nothing, you are 
right. But the fact is, there are two signals occupying the same rf 
frequency at the same time. When they zero beat, the beat note is zero 
and no tone is heard.




The same is true in simulcasting. In the K7PP repeater system, we have 
four transmitters on the same frequency. We zero beat all of the 
transmitters so that areas in between hear little or no zero beat tone.


This is tough to do, so we use hi stability oscillators that don't drift 
much. If they do it's only a couple of hertz. The beat note from a 
couple of hertz is almost inaudible. Most radios don't like to pass 
audio that's under 300 hz and as a matter of fact the speakers 
themselves don't like to reproduce audio at that frequency either.




The one remaining thing is the phase of the audio. If we transmit the 
same audio from the same source but the transmitters in the system are 
located different distances from the audio source, the audio arriving at 
the closest transmitter gets there sooner than the audio from the 
farthest. If we could just slow the audio down a little or delay it's 
arrival time at the closest transmitter a little, the audio would then 
be in phase.


There are several manufacturers that make audio phase delay panels that 
are programmable. You just crank in the amount of delay you want.


You might ask, how do you know how much delay is needed?

The fact is, that radio signals travel at the speed of light. That works 
out to be about 5.4 microseconds per statute mile.


Let's say that your two simulcasting transmitters are located with the 
first one at 20 miles from the audio source and the other at say, five 
miles from the source, you would have a difference of 15 miles between 
your first and second simulcast transmitter. If you take 15 miles times 
5.4 microseconds, you come up with 81 microseconds. Now all you have to 
do is delay the audio to your closest transmitter 81 microseconds and 
then your source audio arrives at the same instant at both simulcast 
transmitters.




With both signals zero beat and in phase, you have what amounts to one 
big transmitter.


I know of one paging system in Puget sound that has 47 transmitters on 
the same frequency.


This means that you could grow your existing system into coverage areas 
that you didn't have before. Many repeaters have gaps between them and 
their closest neighbors. Now you can move your coverage area out to your 
neighbors border where before nothing could be in operation because it 
was to close to either repeater. Since you won't be interfering with 
your self, you can pick and choose the right site to allow you to 
accomplish this.




The other big advantage is that you don't have to run high power or for 
that matter operate from a tall mountain to get

[Repeater-Builder] Re: [GE Mastr II] MASTER II TO RC-210

[Kevin Custer]

W8YSU wrote:
> Does anyone on this list have pictures or scematic of a VHF Master II hooked 
> up to an ARCOM RC-210?
>
> We are starting to work on one for our Club Repeater and I am looking for 
> some examples for reference.

Dean,

Station or converted mobile?

Did you look here?
www.mastr2.com

Kevin

[Repeater-Builder] Off Topic (religious or other) posts - please read.

[Kevin Custer]

I asked once already for everyone to stop the threads where OT posts are 
concerned - many didn't listen.

I'll ask once more - please do NOT post about this OT subject again.

If I cannot gain the respect of those continuing to post, I WILL SHUT 
THE LIST OFF for a few awhile and we'll have a nice vacation.  Those 
continuing with the OT posts will be promptly banned - period.

Thank you for your consideration,
Kevin Custer
List Owner

Re: [Repeater-Builder] Automated spam.

[Kevin Custer]

Facility 406 DM09 wrote:
> Well, you see, it's like this...

You don't have a clue.  You have been a member for 10 days, so, stick 
around and see how spam-less this list really works, or join one that 
explains the working of the lists here on Yahoo.

This and every other off topic post is now over - back to our regularly 
scheduled programming.

Kevin Custer
List Owner