Re: [Repeater-Builder] GE Master II Pa decks

[Doug Bade]

I do not largely recommend the Astron BB series for proper battery 
maintenance. The issue is the charge voltage is directly related to 
the operating voltage so to se the appropriate float voltage you need 
to tweak the operating voltage pot to a lower level and the charge 
current is strictly resistive limited...A simple choice but not a 
good one for long term proper operation of the battery...

Our Trace Engineering charger/controller has 22000 current amps 
passed through it over the last number of years and the original 
batteries are still there... they were good batteries to start with 
and they are non vented UPS type... 5 years or so at this 
point...Trace Engineering is now known as Xantrex..I think...

Real Charge controllers on real UPS type batteries have very tight 
control on bulk, float and maintenance charge cycles to optimize 
charge for your particular battery and work VERY well for a rather 
insignificant amount of money in the big picture...

The BULK charge is fed straight through from your Power supply and is 
regulated by the Charge Controller... The station will largely run on 
the power supply but as I said it is used as a source to the battery 
charger.. not the source to the station...

Size it all correctly and you will never revisit the "problem" again

Astron's are good sources ... but lousy chargers on their own.. at 
least that is my opinion...

Doug
KD8B


At 07:33 PM 2/10/2009, you wrote:

>Doug Bade wrote:
> > The loaded voltage is about 12.5 to 12.8 comparable to what would be
> > in the trunk of a car starting at 13.8 at the battery alternator
> > connection.. including voltage drop...
> > That was the design anyhow... Astron's or eq are some what of a
> > problem as they really do not sag at all.. 13.8 all day all night 
> all nice
> >
>The club is talking about building a battery band that will be somewhere
>around 400ah at 12vcd. they want to buy some "smart charger" that puts
>out 5a. I tried to explain at the club meeting last night that should be
>battery bank go completely down because of an extended power outage,
>that a 5a charger would take 80+ hours to bring the batteries back up,
>and it woul probably take longer than that if the repeater was on during
>the charge. I was thinking about a rs50BB or the like, but wasn't sure
>what the MastrII needed if 13.8 would be too much.. That's the basis of
>the original question.
>
> > I chose a different route at work and built a battery stack with a
> > trace engineering charge controller float charging the batteries
> > active all the time using a astron or eq as the "charger" source..
> > The trace engineering controller ( from the solar world) does the
> > charge maintenance etc like no aftermarket tool I have found for eq
> > moneyI think it was a Model C40 or C65... maybe a C30 would do...
> > all are different current specs...
> >
>Back we go to Google for product specs. Thanks for the idea! 73 Mike
>
>

Re: [Repeater-Builder] GE Master II Pa decks

[Mike Pugh]

Nate Duehr wrote:
> Careful.. 
>
> 1) You should never let a lead-acid battery go "completely down", not even a
> so-called "deep-cycle" one, if you want it to last a long time.  Look at the
> manufacturer's specs and build a voltage-based cut-off switch that will shut
> down the output before they go below the manufacturer's recommended
> discharge voltage.  You could get fancy and include some kind of over-ride
> for a "real" emergency, but at that point you really should have a generator
> and someone to fuel it.
>   
That's what I am trying to avoid. I am once again violating my personal 
rule to not get involved with a club owned repeater. There are always 
way too many "experts" and it usually gets to me when they are at the 
frustration point.
> 2) Direct charging of even that big of a bank with a 50A charger could be
> above the manufacturer's upper limits on charge rate, and you'll likely boil
> off water, reducing the life of the batteries, venting gas, and generally
> wearing out the system.  You need to limit the charge rate to their
> recommendations, if you want the batteries to survive a long time.  (Number
> 1 should help with this.  Maybe the 5A charger will be fine, if you do #1.
> It won't take 80 hours then...)
>   
You're right.

> Most of the time, the better option is a generator.  Yes, the repeater
> system goes down while it takes over, but you can run for a very long time
> for a lot less headache than a battery system.  You could design the battery
> system just to hold-over the system during generator cut-in, but even that's
> overly complex.  Most generators take less than a minute to start and decide
> that their output is sane enough to switch in the load...
>   
You're looking at the same thing that I have already considered. At this 
point, they don't know what they want to do. I'm just looking for 
possible solutions to present to their committee..

> Are they designing for long-term outages or smoothing out short-term ones?
> That's the main design question to ask... 
Well, they just went about 10 days with intermittent power because of 
the huge ice/snow storm that blew through the mid eastern US. So they're 
fresh from the "gotta last forever" mentality.. Doesn't matter that it 
sits 90% of the time unused, they want it to be there whenever... 
Current plans are for a Saturday morning breakfast and subsequent trip 
to the repeater site. I've never been there, so it will be interesting 
to see what they've done up to this point. thanks for the input. Mike KA4MKG

RE: [Repeater-Builder] GE Master II Pa decks

[Nate Duehr]

Careful.. 

1) You should never let a lead-acid battery go "completely down", not even a
so-called "deep-cycle" one, if you want it to last a long time.  Look at the
manufacturer's specs and build a voltage-based cut-off switch that will shut
down the output before they go below the manufacturer's recommended
discharge voltage.  You could get fancy and include some kind of over-ride
for a "real" emergency, but at that point you really should have a generator
and someone to fuel it.

2) Direct charging of even that big of a bank with a 50A charger could be
above the manufacturer's upper limits on charge rate, and you'll likely boil
off water, reducing the life of the batteries, venting gas, and generally
wearing out the system.  You need to limit the charge rate to their
recommendations, if you want the batteries to survive a long time.  (Number
1 should help with this.  Maybe the 5A charger will be fine, if you do #1.
It won't take 80 hours then...)

Most of the time, the better option is a generator.  Yes, the repeater
system goes down while it takes over, but you can run for a very long time
for a lot less headache than a battery system.  You could design the battery
system just to hold-over the system during generator cut-in, but even that's
overly complex.  Most generators take less than a minute to start and decide
that their output is sane enough to switch in the load...

Are they designing for long-term outages or smoothing out short-term ones?
That's the main design question to ask... 

Nate WY0X

Re: [Repeater-Builder] GE Master II Pa decks

[Mike Pugh]

Doug Bade wrote:
> The loaded voltage is about 12.5 to 12.8 comparable to what would be 
> in the trunk of a car starting at 13.8 at the battery alternator 
> connection.. including voltage drop...
> That was the design anyhow... Astron's or eq are some what of a 
> problem as they really do not sag at all.. 13.8 all day all night all nice
>   
The club is talking about building a battery band that will be somewhere 
around 400ah at 12vcd. they want to buy some "smart charger" that puts 
out 5a. I tried to explain at the club meeting last night that should be 
battery bank go completely down because of an extended power outage, 
that a 5a charger would take 80+ hours to bring the batteries back up, 
and it woul probably take longer than that if the repeater was on during 
the charge. I was thinking about a rs50BB or the like, but wasn't sure 
what the MastrII needed if 13.8 would be too much.. That's the basis of 
the original question.

> I chose a different route at work and built a battery stack with a 
> trace engineering charge controller float charging the batteries 
> active all the time using a astron or eq as the "charger" source.. 
> The trace engineering controller ( from the solar world) does the 
> charge maintenance etc like no aftermarket tool I have found for eq 
> moneyI think it was a Model C40 or C65... maybe a C30 would do... 
> all are different current specs...
>   
Back we go to Google for product specs. Thanks for the idea! 73 Mike

Re: [Repeater-Builder] GE Master II Pa decks

[Doug Bade]

The loaded voltage is about 12.5 to 12.8 comparable to what would be 
in the trunk of a car starting at 13.8 at the battery alternator 
connection.. including voltage drop...
That was the design anyhow... Astron's or eq are some what of a 
problem as they really do not sag at all.. 13.8 all day all night all nice

I chose a different route at work and built a battery stack with a 
trace engineering charge controller float charging the batteries 
active all the time using a astron or eq as the "charger" source.. 
The trace engineering controller ( from the solar world) does the 
charge maintenance etc like no aftermarket tool I have found for eq 
moneyI think it was a Model C40 or C65... maybe a C30 would do... 
all are different current specs...

Doug


At 03:53 PM 2/10/2009, you wrote:

>Doug Bade wrote:
> > Mid power Mastr II stations used 15 amp factory power supplies...100w
> > stations used 30 amp power supples..
> > so.. probably less than 15 amps.. maybe 10-12..
> >
>Apparently I am going to be inheriting the care and feeding of some
>MastrII's. First order of business is to get battery backup going on one
>of them. Is the loaded voltage of the factory supplies 13.8, or
>something close? I need to know what I am going to be dealing with.
>Thanks! Mike KA4MKG
>
>

Re: [Repeater-Builder] GE Master II Pa decks

[Mike Pugh]

Doug Bade wrote:
> Mid power Mastr II stations used 15 amp factory power supplies...100w 
> stations used 30 amp power supples..
> so.. probably less than 15 amps.. maybe 10-12..
>   
Apparently I am going to be inheriting the care and feeding of some 
MastrII's. First order of business is to get battery backup going on one 
of them. Is the loaded voltage of the factory supplies 13.8, or 
something close? I need to know what I am going to be dealing with. 
Thanks! Mike KA4MKG

Re: [Repeater-Builder] GE Master II Pa decks

[AJ]

Let me clarify - this is a Mid Power Mastr II station, however, it has a
high power P/S (original 15 amp power supply was repurposed).

This factory supply at no load typically sits around 15 VDC with 121 VAC
input.




On Tue, Feb 10, 2009 at 1:30 PM, Doug Bade  wrote:

>   Mid power Mastr II stations used 15 amp factory power supplies...100w
> stations used 30 amp power supples..
> so.. probably less than 15 amps.. maybe 10-12..
>
> Reducing the voltage to 12.8 from the batteries will significantly
> lower the output power relative to 13.8v power supplies too..Factory
> power supplies are designed to collapse on voltage to about 12.5 vdc
> or so..at rated power load...
>
> Doug
> KD8B
>
> At 03:08 PM 2/10/2009, you wrote:
>
> >Ok, the Elmer fully retuned the Mastr2 mid power repeater on Sunday
> >and has it tuned for roughly 26 watts out of the P/A... This is a 40
> >watt P/A. What will this station typically draw current-wise? Right
> >now it's fed off of a 30 amp supply (major overkill) but we'd like
> >to have a rough idea on amp draw to calculate standby time off of
> batteries.
> >
> >Thanks!
> >
> >-AJ, K6LOR
> >
> >On Tue, Feb 3, 2009 at 9:45 AM, AJ
> ><
> aj.grant...@gmail.com > wrote:
> >Charles:
> >
> >Any idea what your current draw was when you had it tuned down to 10
> watts?
> >
> >I've been doing the alignment directly off of the exciter (250 mw
> >off of the RCA jack on the drawer) but the power output doesn't
> >match the needs of the mobile usage.
> >
> >Thanks!
> >
> >73s,
> >AJ, K6LOR
>
>  
>

Re: [Repeater-Builder] GE Master II Pa decks

[Doug Bade]

Mid power Mastr II stations used 15 amp factory power supplies...100w 
stations used 30 amp power supples..
so.. probably less than 15 amps.. maybe 10-12..

Reducing the voltage to 12.8 from the batteries will significantly 
lower the output power relative to 13.8v power supplies too..Factory 
power supplies are designed to collapse on voltage to about 12.5 vdc 
or so..at rated power load...

Doug
KD8B

At 03:08 PM 2/10/2009, you wrote:

>Ok, the Elmer fully retuned the Mastr2 mid power repeater on Sunday 
>and has it tuned for roughly 26 watts out of the P/A... This is a 40 
>watt P/A. What will this station typically draw current-wise? Right 
>now it's fed off of a 30 amp supply (major overkill) but we'd like 
>to have a rough idea on amp draw to calculate standby time off of batteries.
>
>Thanks!
>
>-AJ, K6LOR
>
>On Tue, Feb 3, 2009 at 9:45 AM, AJ 
><aj.grant...@gmail.com> wrote:
>Charles:
>
>Any idea what your current draw was when you had it tuned down to 10 watts?
>
>I've been doing the alignment directly off of the exciter (250 mw 
>off of the RCA jack on the drawer) but the power output doesn't 
>match the needs of the mobile usage.
>
>Thanks!
>
>73s,
>AJ, K6LOR

Re: [Repeater-Builder] GE Master II Pa decks

[AJ]

Ok, the Elmer fully retuned the Mastr2 mid power repeater on Sunday and has
it tuned for roughly 26 watts out of the P/A... This is a 40 watt P/A. What
will this station typically draw current-wise? Right now it's fed off of a
30 amp supply (major overkill) but we'd like to have a rough idea on amp
draw to calculate standby time off of batteries.

Thanks!

-AJ, K6LOR

On Tue, Feb 3, 2009 at 9:45 AM, AJ  wrote:

> Charles:
>
> Any idea what your current draw was when you had it tuned down to 10 watts?
>
> I've been doing the alignment directly off of the exciter (250 mw off of
> the RCA jack on the drawer) but the power output doesn't match the needs of
> the mobile usage.
>
> Thanks!
>
> 73s,
> AJ, K6LOR
>
>   On Tue, Feb 3, 2009 at 9:22 AM, Ham-Radio wrote:
>
>>AJ,
>>
>> You asked what is the lowest power level for the Mastr2 radio. I had taken
>> a 250 Watt base and turned it down to 10 Watts out for testing purposes with
>> out generating any spurs.
>>
>> However, If I remember to documents say to not run the poweer any lower
>> than 50% of rated power out.
>>
>> Remember, you can use only the driver if you need low power out.
>>
>> Charles Miller
>>
>>
>>  --
>> *From:* Repeater-Builder@yahoogroups.com [mailto:
>> repeater-buil...@yahoogroups.com] *On Behalf Of *AJ
>> *Sent:* Tuesday, February 03, 2009 10:04 AM
>> *To:* Repeater-Builder@yahoogroups.com
>> *Subject:* Re: [Repeater-Builder] GE Master II Pa decks
>>
>>   With regard to the Intermittent Duty 50 watt Stations, what is the
>> lowest these will tune down to without excessive spurs?
>>
>> I have a Mastr2 VHF station we're looking at placing in our command
>> trailer for temporary operations - AC power most of the time, but would like
>> to have it draw as little power as possible (within reason) for times when
>> working on battery power only. 250 mw off the exciter just isn't enough, 65
>> watts out of the P/A is just too much.
>>
>>
>> 73s,
>>
>> AJ, K6LOR/R
>> 147.080+
>> 444.750+
>>
>> On Mon, Feb 2, 2009 at 6:13 PM, Nate Duehr  wrote:
>>
>>>   An isolator with appropriate harmonic filtering AFTER it (they create
>>> harmonics, which are not friendly to your neighbors), presents a nice
>>> solid
>>> non-reactive 50 ohm load to the transmitter. It doesn't matter if it's a
>>> GE
>>> MASTR II PA, or someone elses. Many Motorola PA's have the isolator built
>>> in, for example.
>>>
>>> The GE PA likes a 50 ohm load or it tends to do squirrelly things, like
>>> die.
>>> You can get this by proper choice of QUALITY products for your
>>> filtering/feedline/antenna system, or you can use an isolator, or you can
>>> have the "belt and suspenders" mentality and always run an isolator on
>>> the
>>> output of the PA. Another good reason to do this at high RF commercial
>>> sites is that the PA (depending on how you may have modified it) has
>>> transistors in the final section that are "always on", thus... mixing can
>>> occur in the PA if RF from the outside world can get down INTO the PA
>>> from
>>> elsewhere. Also not a nice thing for your neighbors.
>>>
>>> The final "benefit" to a properly sized dummy load on your isolator is
>>> that
>>> the antenna can literally fall off the tower, and the PA will still be
>>> driving into a solid 50 ohm dummy load. As long as that load is the
>>> correct
>>> size for your PA's power level, no damage to the PA will occur, even
>>> though
>>> your antenna is gone.
>>>
>>> Some late-model MASTR II PA's have built in Z-matchers on their output
>>> Low-Pass Filter board on the right lower side. These have to be adjusted
>>> correctly per the manual any time a new PA is installed on a new antenna
>>> system, or anything changes in the antenna system. Older PA's do not have
>>> this feature, but an off-board Z-matcher can be added in lieu of an
>>> isolator
>>> if all you're concerned about is matching the source (PA) to the load
>>> (antenna system).
>>>
>>> The GE PA comes in different sizes for different power level needs. The
>>> VHF
>>> 100W (original with four final driver transistors) was known to get
>>> spurious
>>> and throw stuff up and down the band for various reasons. The newer
>>> three-final-transis

Re: [Repeater-Builder] GE Master II Pa decks

[AJ]

Charles:

Any idea what your current draw was when you had it tuned down to 10 watts?

I've been doing the alignment directly off of the exciter (250 mw off of the
RCA jack on the drawer) but the power output doesn't match the needs of the
mobile usage.

Thanks!

73s,
AJ, K6LOR

On Tue, Feb 3, 2009 at 9:22 AM, Ham-Radio  wrote:

>AJ,
>
> You asked what is the lowest power level for the Mastr2 radio. I had taken
> a 250 Watt base and turned it down to 10 Watts out for testing purposes with
> out generating any spurs.
>
> However, If I remember to documents say to not run the poweer any lower
> than 50% of rated power out.
>
> Remember, you can use only the driver if you need low power out.
>
> Charles Miller
>
>
>  --
> *From:* Repeater-Builder@yahoogroups.com [mailto:
> repeater-buil...@yahoogroups.com] *On Behalf Of *AJ
> *Sent:* Tuesday, February 03, 2009 10:04 AM
> *To:* Repeater-Builder@yahoogroups.com
> *Subject:* Re: [Repeater-Builder] GE Master II Pa decks
>
>   With regard to the Intermittent Duty 50 watt Stations, what is the
> lowest these will tune down to without excessive spurs?
>
> I have a Mastr2 VHF station we're looking at placing in our command trailer
> for temporary operations - AC power most of the time, but would like to have
> it draw as little power as possible (within reason) for times when working
> on battery power only. 250 mw off the exciter just isn't enough, 65 watts
> out of the P/A is just too much.
>
>
> 73s,
>
> AJ, K6LOR/R
> 147.080+
> 444.750+
>
> On Mon, Feb 2, 2009 at 6:13 PM, Nate Duehr  wrote:
>
>>   An isolator with appropriate harmonic filtering AFTER it (they create
>> harmonics, which are not friendly to your neighbors), presents a nice
>> solid
>> non-reactive 50 ohm load to the transmitter. It doesn't matter if it's a
>> GE
>> MASTR II PA, or someone elses. Many Motorola PA's have the isolator built
>> in, for example.
>>
>> The GE PA likes a 50 ohm load or it tends to do squirrelly things, like
>> die.
>> You can get this by proper choice of QUALITY products for your
>> filtering/feedline/antenna system, or you can use an isolator, or you can
>> have the "belt and suspenders" mentality and always run an isolator on the
>> output of the PA. Another good reason to do this at high RF commercial
>> sites is that the PA (depending on how you may have modified it) has
>> transistors in the final section that are "always on", thus... mixing can
>> occur in the PA if RF from the outside world can get down INTO the PA from
>> elsewhere. Also not a nice thing for your neighbors.
>>
>> The final "benefit" to a properly sized dummy load on your isolator is
>> that
>> the antenna can literally fall off the tower, and the PA will still be
>> driving into a solid 50 ohm dummy load. As long as that load is the
>> correct
>> size for your PA's power level, no damage to the PA will occur, even
>> though
>> your antenna is gone.
>>
>> Some late-model MASTR II PA's have built in Z-matchers on their output
>> Low-Pass Filter board on the right lower side. These have to be adjusted
>> correctly per the manual any time a new PA is installed on a new antenna
>> system, or anything changes in the antenna system. Older PA's do not have
>> this feature, but an off-board Z-matcher can be added in lieu of an
>> isolator
>> if all you're concerned about is matching the source (PA) to the load
>> (antenna system).
>>
>> The GE PA comes in different sizes for different power level needs. The
>> VHF
>> 100W (original with four final driver transistors) was known to get
>> spurious
>> and throw stuff up and down the band for various reasons. The newer
>> three-final-transistor PA's (the most commonly seen) are less prone to do
>> this, but can also become RF noisemakers if turned down too much. No MASTR
>> II tech I know of will recommend turning any MASTR II PA any further down
>> than roughly 2/3's its maximum rated power output, ESPECIALLY not without
>> looking at it on a spectrum analyzer to make sure it's not spurring. When
>> they go spurious, which is rare enough people get away with turning the
>> PA's
>> down more than 2/3's, they also typically overheat drastically and they'll
>> destroy themselves relatively quickly.
>>
>> If you need less power than 50W it's highly recommended to remove stages
>> of
>> the PA to get to the lower power level you need, bypassing them
>> completel

RE: [Repeater-Builder] GE Master II Pa decks

[Ham-Radio]

AJ,
 
You asked what is the lowest power level for the Mastr2 radio. I had taken a
250 Watt base and turned it down to 10 Watts out for testing purposes with
out generating any spurs.
 
However, If I remember to documents say to not run the poweer any lower than
50% of rated power out.
 
Remember, you can use only the driver if you need low power out.
 
Charles Miller
 

  _  

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of AJ
Sent: Tuesday, February 03, 2009 10:04 AM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] GE Master II Pa decks


With regard to the Intermittent Duty 50 watt Stations, what is the lowest
these will tune down to without excessive spurs?
 
I have a Mastr2 VHF station we're looking at placing in our command trailer
for temporary operations - AC power most of the time, but would like to have
it draw as little power as possible (within reason) for times when working
on battery power only. 250 mw off the exciter just isn't enough, 65 watts
out of the P/A is just too much.
 
 
73s,
 
AJ, K6LOR/R
147.080+
444.750+


On Mon, Feb 2, 2009 at 6:13 PM, Nate Duehr  wrote:


An isolator with appropriate harmonic filtering AFTER it (they create
harmonics, which are not friendly to your neighbors), presents a nice solid
non-reactive 50 ohm load to the transmitter. It doesn't matter if it's a GE
MASTR II PA, or someone elses. Many Motorola PA's have the isolator built
in, for example.

The GE PA likes a 50 ohm load or it tends to do squirrelly things, like die.
You can get this by proper choice of QUALITY products for your
filtering/feedline/antenna system, or you can use an isolator, or you can
have the "belt and suspenders" mentality and always run an isolator on the
output of the PA. Another good reason to do this at high RF commercial
sites is that the PA (depending on how you may have modified it) has
transistors in the final section that are "always on", thus... mixing can
occur in the PA if RF from the outside world can get down INTO the PA from
elsewhere. Also not a nice thing for your neighbors.

The final "benefit" to a properly sized dummy load on your isolator is that
the antenna can literally fall off the tower, and the PA will still be
driving into a solid 50 ohm dummy load. As long as that load is the correct
size for your PA's power level, no damage to the PA will occur, even though
your antenna is gone.

Some late-model MASTR II PA's have built in Z-matchers on their output
Low-Pass Filter board on the right lower side. These have to be adjusted
correctly per the manual any time a new PA is installed on a new antenna
system, or anything changes in the antenna system. Older PA's do not have
this feature, but an off-board Z-matcher can be added in lieu of an isolator
if all you're concerned about is matching the source (PA) to the load
(antenna system).

The GE PA comes in different sizes for different power level needs. The VHF
100W (original with four final driver transistors) was known to get spurious
and throw stuff up and down the band for various reasons. The newer
three-final-transistor PA's (the most commonly seen) are less prone to do
this, but can also become RF noisemakers if turned down too much. No MASTR
II tech I know of will recommend turning any MASTR II PA any further down
than roughly 2/3's its maximum rated power output, ESPECIALLY not without
looking at it on a spectrum analyzer to make sure it's not spurring. When
they go spurious, which is rare enough people get away with turning the PA's
down more than 2/3's, they also typically overheat drastically and they'll
destroy themselves relatively quickly. 

If you need less power than 50W it's highly recommended to remove stages of
the PA to get to the lower power level you need, bypassing them completely,
or moving to a lower power/lower-duty-cycle PA in the model line.

Done right, even after 20 years of commercial service, the VHF MASTR II PA
will happily sit there and put out 85W all day long, without batting an
eyelash. Many will still do a strong 110W and never care, either. It's
just a little "easier" on the gear to run the power back just a little bit.
The difference (in dB) between 85W and 110W often isn't significant,
depending on your area you're wanting to cover.

Why are you wanting to turn your MASTR II back so far? After duplexer
losses, you're down to roughly 20W if you're putting 45W into a duplexer (if
you're running split antenna, with no duplexer and vertical separation,
nevermind -- but I doubt you are), and 20W doesn't "balance" well with 50W
mobiles. If you're trying to balance for HT coverage only, I could see it
maybe... 

My personal rule for the MASTR II PA's is: Set 'em to 85W and forget 'em.
Put an isolator on for ALL of the good reaso

Re: [Repeater-Builder] GE Master II Pa decks

[AJ]

ig converted into a repeater. That's NOT a
> MASTR II Repeater PA. They're de-rating the PA to save it from overheating
> and dying, as it's not rated for 100% continuous duty at full power in the
> mobile rig with the small heatsink. The MASTR II REPEATER PA is a giant
> heavy thing with plenty of heatsink fins, 19" wide and multiple RU tall,
> that is EIA rated to do continuous-duty cycle at 110W for at least 24
> hours.
>
> Nate WY0X
>
> -Original Message-
> From: Repeater-Builder@yahoogroups.com
> [mailto:Repeater-Builder@yahoogroups.com]
> On Behalf Of Randy
> Sent: Sunday, February 01, 2009 8:24 AM
> To: Repeater-Builder@yahoogroups.com 
> Subject: [Repeater-Builder] GE Master II Pa decks
>
> Hi group whats the deal with the GE Master II PA decks needing to use a
> ferrite isolator with a 50 ohm dummy load and a low pass filter between
> the PA and the High Q duplexer. Is this something that most do with
> the 75 and 100 w Pa's We just replaced one in a Master II Mobile radio
> which lasted for years with no issues. After installing the PA and
> doing a tune up the Radio did about 80 watts we set it to 45 watts I
> was also told that was not a good thing to do so whats the story on the
> PA. I seen where Repeater Builder the Company talks about the 75 or 100
> watt PA's in there web site only bening good set to 45 watts or so
> anyway so I assume they are setting theres at that level when they do a
> Duplex conversion ect making the radio into a repeater. I have read the
> information on the website about this but would like some user comments
> as well. Also where would one get the needed parts ect to do this Mod.
>
> Randy
>
> 
>
> Yahoo! Groups Links
>
> 
>

RE: [Repeater-Builder] GE Master II Pa decks

[Nate Duehr]

An isolator with appropriate harmonic filtering AFTER it (they create
harmonics, which are not friendly to your neighbors), presents a nice solid
non-reactive 50 ohm load to the transmitter.  It doesn't matter if it's a GE
MASTR II PA, or someone elses.  Many Motorola PA's have the isolator built
in, for example.

The GE PA likes a 50 ohm load or it tends to do squirrelly things, like die.
You can get this by proper choice of QUALITY products for your
filtering/feedline/antenna system, or you can use an isolator, or you can
have the "belt and suspenders" mentality and always run an isolator on the
output of the PA.  Another good reason to do this at high RF commercial
sites is that the PA (depending on how you may have modified it) has
transistors in the final section that are "always on", thus... mixing can
occur in the PA if RF from the outside world can get down INTO the PA from
elsewhere.  Also not a nice thing for your neighbors.

The final "benefit" to a properly sized dummy load on your isolator is that
the antenna can literally fall off the tower, and the PA will still be
driving into a solid 50 ohm dummy load.  As long as that load is the correct
size for your PA's power level, no damage to the PA will occur, even though
your antenna is gone.

Some late-model MASTR II PA's have built in Z-matchers on their output
Low-Pass Filter board on the right lower side.  These have to be adjusted
correctly per the manual any time a new PA is installed on a new antenna
system, or anything changes in the antenna system.  Older PA's do not have
this feature, but an off-board Z-matcher can be added in lieu of an isolator
if all you're concerned about is matching the source (PA) to the load
(antenna system).

The GE PA comes in different sizes for different power level needs.  The VHF
100W (original with four final driver transistors) was known to get spurious
and throw stuff up and down the band for various reasons.  The newer
three-final-transistor PA's (the most commonly seen) are less prone to do
this, but can also become RF noisemakers if turned down too much.  No MASTR
II tech I know of will recommend turning any MASTR II PA any further down
than roughly 2/3's its maximum rated power output, ESPECIALLY not without
looking at it on a spectrum analyzer to make sure it's not spurring.  When
they go spurious, which is rare enough people get away with turning the PA's
down more than 2/3's, they also typically overheat drastically and they'll
destroy themselves relatively quickly.  

If you need less power than 50W it's highly recommended to remove stages of
the PA to get to the lower power level you need, bypassing them completely,
or moving to a lower power/lower-duty-cycle PA in the model line.

Done right, even after 20 years of commercial service, the VHF MASTR II PA
will happily sit there and put out 85W all day long, without batting an
eyelash.  Many will still do a strong 110W and never care, either.  It's
just a little "easier" on the gear to run the power back just a little bit.
The difference (in dB) between 85W and 110W often isn't significant,
depending on your area you're wanting to cover.

Why are you wanting to turn your MASTR II back so far?  After duplexer
losses, you're down to roughly 20W if you're putting 45W into a duplexer (if
you're running split antenna, with no duplexer and vertical separation,
nevermind -- but I doubt you are), and 20W doesn't "balance" well with 50W
mobiles.  If you're trying to balance for HT coverage only, I could see it
maybe... 

My personal rule for the MASTR II PA's is: Set 'em to 85W and forget 'em.
Put an isolator on for ALL of the good reasons for an isolator, filter it
properly, and forget about it.  The vast majority of them will run for 10 or
more years without touching them again after doing that.

Look carefully at the Repeater-Builder company specifications -- you may be
looking at a MASTR II *MOBILE* rig converted into a repeater.  That's NOT a
MASTR II Repeater PA.  They're de-rating the PA to save it from overheating
and dying, as it's not rated for 100% continuous duty at full power in the
mobile rig with the small heatsink.  The MASTR II REPEATER PA is a giant
heavy thing with plenty of heatsink fins, 19" wide and multiple RU tall,
that is EIA rated to do continuous-duty cycle at 110W for at least 24 hours.

Nate WY0X

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Randy
Sent: Sunday, February 01, 2009 8:24 AM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] GE Master II Pa decks

Hi group whats the deal with the GE Master II PA decks needing to use a 
ferrite isolator with a 50 ohm dummy load and a low pass filter between 
the PA and the High Q duplexer. Is this some

[Repeater-Builder] GE Master II Pa decks

[Randy]

Hi group whats the deal with the GE Master II PA decks needing to use a 
ferrite isolator with a 50 ohm dummy load and a low pass filter between 
the PA and the High Q duplexer. Is this something that most do  with 
the 75 and 100 w Pa's We just replaced one in a Master II Mobile radio 
which lasted for years with no issues. After installing the PA and 
doing a tune up the Radio did about 80 watts we set it to 45 watts  I 
was also told that was not a good thing to do so whats the story on the 
PA. I seen where Repeater Builder the Company talks about the 75 or 100 
watt PA's in there web site only bening good set to 45 watts or so 
anyway so I assume they are setting theres at that level when they do a 
Duplex conversion ect making the radio into a repeater. I have read the 
information on the website about this but would like some user comments 
as well. Also where would one get the needed parts ect to do this Mod.


Randy