a case where one core mix is the be all end all for the range of things
you run into in the field. Especially at high common mode impedances.
Receiving is a completely different story, because core stresses are always
low.
73 Tom
_
Topband Reflector Archives - http
I have seen distributors of core mix cores many times over the years. This
includes distributors on the only approved list. This is why I always
verify cores I use.
As for Fair Rite being the only legitimate source of part numbers, and
everyone else being a criminal or trying to rip people
position. We often hear hum, noise, distortion,
and artifacts that are not on the antenna line.
73 Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
well if they were), they are all
different.
73 Tom
- Original Message -
From: Carl k...@jeremy.mv.com
To: Mike Greenway k...@bellsouth.net; topband@contesting.com
Sent: Thursday, July 31, 2014 8:00 PM
Subject: Re: Topband: Topband Digest, Vol 139, Issue 20
More like a Chevy vs
to almost any taste, except those who specifically don't like the brand.
The K3 does some things virtually no other radio does properly concerning
diversity and DX use, and it has excellent close spaced receiver
performance, so for me there is really no other choice.
73 Tom
or a very nominal cost
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
That's what I was thinking all along. If you put enough large loops in it,
you could even get away with using 3/4 aluminum hardline. :-) Of course,
that doesn't mean it should be done.
Even the CB operator down the road does this. He has regular 7/8th inch and,
as far as I know, it has been
not decouple some of mine because the feedlines are all buried a foot
deep for 160-170 feet to the center, I have several reasonably long radials
on each element, and the antenna is far from any noise. Some of mine I
decouple, because they are near the house and the cables are not deep
buried.
73 Tom
Mike,
I like LMR400-DB. Not only is it direct burial but it is the lowest loss of
the RG8 type cables.
73,
Tom WA2BCK
-Original Message-
From: mstang...@comcast.net
Sent: Tuesday, June 03, 2014 10:10 AM
To: topband@contesting.com
Subject: Topband: 50 ohm direct burial coax cable
I am putting up a single DXE 80m 1/4 vertical. I can put out the proper
radials. I will have to add some longer ones for 160.
That's a good vertical, and the 80M radials will probaby be adequate if you
have enough of them.
Now to figure out switching in and out 160 and the matching.
The only damage on my Yagi antennas from the ice storm we had (about an inch
of radial ice) was to Philliystran struts. In every case the jacket held in
place under the clamps but the strand inside moved. Now I have to rent a
crane with man basket to repair the struts.
The end attachment with
I've been looking at the Shared Apex Loop, and one thing I am puzzled by
(among many) is that the bias tee/DC coupler circuit has both sides of
the 75-ohm feed coming in from the antenna and the DC supplied to the
coupler totally isolated from ground, while the ground side of the coax
going to
mosfets that
has overheated and I can not read the value. Can you tell me the value of
that resistor if yours is ok?
Regards,
Tom Miller
WA3PZI
73
_
Topband Reflector Archives - http://www.contesting.com/_topband
such as 450 ohms.
Surplus hardline is a much better option, IMO.
73 Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
on that line was in the .25 dB range on 4 MHz, including
baluns.
Unfortunately regular window line is neither 450 ohm, or as low loss as is
published most places (or calculated in some calculators). Some of the ARRL
stuff shows half the real loss.
73 Tom
_
Topband
.
If there is a significant common mode, a few cheap beads and/or some grounds
would be a better investment than new cables. :)
Far more worrisome are ground paths through devices or improperly installed
lines.
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
Tom,
Let's revisit Jaan's original question:
Background:
I have a tower that is 137ft. or 42m tall. It is triangular 1ft 10inches
or
40cm wide. The tower is guy wired at three levels with non-isolated wire.
The foundation is a concrete slab on on rocky ground.
The surroundings is quite flat
Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
160m power on FL2100z
Is the input circuit properly matched?
Herb Schenbohm, KV4FZ
On 4/19/2014 7:47 PM, Tom W8JI wrote:
I think we must do something on the anode coil for better Q or add some
length, change diameter?.. or other things ..?!
The only real tank circuit issue is range
falls too low. While it is unsafe
and should never be done, sometimes removing the cover restores performance
by increasing tank inductance when the coil is near the cabinet. Dentron is
bad about this.
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
, which is not necessary.
It is possible it has an open load padding capacitor, because they are
notorious for going open, but the real fix is to correct the tank by
increasing inductance (which reduces loaded Q) so it acts normal.
73 Tom
- Original Message -
From: JC N4IS n
)
If you are doing work you may as well do it correctly. Adding tank
inductance will probably fix the entire problem, plus give you more matching
range and sharper tuning. Then you can probably remove capacitance.
73 Tom
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Topband Reflector Archives - http://www.contesting.com
I think we must do something on the anode coil for better Q or add some
length, change diameter?.. or other things ..?!
The only real tank circuit issue is range of the tank components used to
adjust the matching. Some amplifiers run outside optimum capacitor
adjustment ranges.
Are any
I think the rules need changed to require an ID.
- Original Message -
From: Lee K7TJR k7...@msn.com
To: topband@contesting.com
Sent: Monday, March 31, 2014 11:52 AM
Subject: Topband: 1810.8 carrier found.
I have been informed that the carrier on 1810.8 KHz has been found.
I
Floating the shield may even make it work better?
This shield could be used as the antenna, and the inner pair as the
transmission line. That would work fine.
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Topband Reflector Archives - http://www.contesting.com/_topband
Has anyone on the reflector ACTUALLY tried two wire audio twisted pair for
a 2 wire, two direction Beverage antenna. If yes, how did it work ? Notice
any added directional properties?
There is no reason why it won't work or why shielded wire won't work with
proper transformers and wiring.
I would like to see if anyone actually tried the wire, and if it rejected
any portion of RF signals.
How would someone measure rejected any portion of RF signals in a
meaningful, quantitative, way?
_
Topband Reflector Archives - http://www.contesting.com/_topband
Before we get too nasty with names about this, the USPS has a terrible
website for finding first class to Canada.
It intentionally steers people into priority, with first class as a somewhat
hidden option.
It is very common to miss the cheaper rates unless one reads the fine print.
No good
here for
contests, and have had one operator who consistently melts down the plate
tuning capacitor from grossly improper tuning, but it never hurts a switch.
Send me a picture of the arc area before you move any wires.
73 Tom
_
Topband Reflector Archives - http
-to-back L networks at some higher frequency.
http://www.w8ji.com/rf_plate_choke.htm
This is why almost all amplifiers use pick-up-and-hold switch contacts. It
can be a problem with matching networks, too.
73 Tom
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Topband Reflector Archives - http://www.contesting.com
Hi Jim,
They call everything 450 ohm.
450 ohm ladder line is not really 450 ohms, unless you use a certain type.
It actually ranges from around 350 ohms upwards, depending on line type.
If you need to not mix impedances, what type line do you have now?
73 Tom
- Original Message
Wrong reflector, but I disagree completely with this:
The HV build up was mitigated by the 10pf cap between the 40-20M positions
which also reduces arcing on the SB-220 which is a shorting switch and a
cap can be adapted to some 160-10M amps. The right hand one in that photo
had the 80-40M
Here's my question: the large inductor is much higher Q on 160 than the
small inductor (large inductor is about 4.5 diameter, small one about 2
diameter). Would it be better to have the large inductor connected to the
antenna and the small one to the feed (the two inductors would still be in
is less of an issue than 80 or 160 through 10.
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
and hold the
lower band contacts when switched to higher bands. This allows the taps to
build up high voltages on lower band taps when working higher bands.
Switches should be pick up and hold, or progressively shorting.
73 Tom
_
Topband Reflector Archives - http
People also have to be careful with systems.
The resistor on center tap splits the signal, but runs the ports
out-of-phase. This is OK when you need a 180 flip between port, or you don't
care about phase, but it can get you in trouble in many cases.
Also, the very same thing that makes it
Has anyone modeled the 1/4 slopers? Perhaps the Alpha Delta DXA?
The pattern and performance of a 1/4 wave sloper is extremely dependent on
the tower and what is on the tower, the guy lines (if uninsulated), and even
how the tower is grounded.
There are very common cases where it won't
. With the shield attached to the tower, the tower is the ground.
This is where all the problems with operating inconsistency come in.
73 Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
Hi Paul,
Where is a selectivity spec or a description??
73 Tom
- Original Message -
From: Paul Christensen w...@arrl.net
To: topband topband@contesting.com
Sent: Wednesday, March 05, 2014 10:15 AM
Subject: Re: Topband: New MFJ 259C available
+13 dBm is nothing. That is only 20
the page to near the bottom, we find the superheterodyne or
direct conversion frequency selective types. This is the mistake I think MFJ
made, not doing a selective detector. The single overwhelming problem is
external voltage.
73 Tom
.
- Original Message -
From: Paul Christensen w
need, but would be a whole
lot better with a cal correction (open, short, load), sweep, wide range, and
receivers with a phase detector instead of a diode bridge.
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
Half wave verticals have been very disappointing to me over the years when
I had the tall BC towers in my backyard to play with after midnight on
160.
I installed a 318 ft insulated base tower in stages and watched the results.
I felt there was very little difference from 1/4 wave up to about
Depends on the noise at your location, before I removed the 300 ft
towers
here I matched one for 160 and ran low power in the Stew Perry a few years
ago, ended up number 1 world wide if memory is correct, and receive was
only the xmt antenna at that time.
If the locations noise is low you
All the other 4 conductors are bright clean copper when stripped.
Could anyone tell me why some insulated copper conductors turn black in
this way and whether there's a better way of cleaning it off.
Water inside the insulation plus sulfur and/or irons that formed copper
sulfide or
and reactance as things are
tuned.
I would not even guess at a cure for something with a bunch of unknowns that
might not even be a problem. I think this is a bigger worry and more complex
than it should be.
73 Tom
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Topband Reflector Archives - http://www.contesting.com
you have indicates loss. It
doesn't. There are a whole lot of things that go into bandwidth beside loss!
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
and I'm back to my 45 - j11 ohms.
The choke is completely unnecessary with a shunt feed tower. It won't help a
thing, so leave it out.
73 Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
I have a MFJ-1025 and I have seen some past post about using this unit for
direction steering using two separate antennas. I am installing a new two
wire beverage and wonder if there would be any steering possible using the
two inputs from the beverage into the MFJ. I had to ask
Is there is a way the information available in the LP-100A in the
shack or the MFJ-259B can be used to locate the defective area?
The 259B, if used correctly, will get you within a couple feet of the
problem.
Download the latest manual.
73 Tom
_
Topband Reflector
The double female was fine, it was either in the 259 or right after,
close enough that the connector smelled. No idea where it was made, I
have a lot of parts from my hayday 30 years ago back then it was
pretty much all from here. Some are marked Amphenol, some unmarked.
If you open a
that occasional mistakes by people trying
to be helpful becomes an issue with score.
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
Dielectric losses become evident at 2M with 1500W and at 432 400W of
steady
carrier will heat up even the best N connectors and RG-213. For that
reason
many are switching to the 7/16 DIN.
That has nothing at all to do with dielectric losses.
N connectors have a tiny BNC size center pin.
The lowest loss cable I have here is 75 Ohm 1 General Cable Fused Disc;
its under a differnt name these days. Mostly air with poly discs and used
for the 200' runs for 10M, 2M, and 222 MHz.
For the 160/80 inverted vee it is 450' of regular foamed 3/4 75 Ohm CATV
hardline with a RG-11 jumper
the element, I can gamma match without a capacitor.
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
of stumbling on things. Why, I remember when Walt patiently
taught me how conductor losses dominated transmission line loss, and why
that was important! :-)
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
I didn't notice that the K index jumped to 5 until after I posted this.
That doesn't help.
But the 3 or 4 stations that I hear calling CQ are quite strong (S9+) in
SW
Missouri.
W3LPL is S9+, but he had a lot of trouble hearing my 1500 watts. Odd.
He would hear you better if you were
the capacitor, you will have a lot of work to
do.
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
pulleys could be released.
I have not looked at Beverages and in woods and fields, but I have a lot of
tree and building damage so I expect some chain saw and receiving antenna
work.
All in all not bad for such a large amount of ice.
73 Tom
_
Topband Reflector Archives - http
locations, and even different with
different antennas. So what happens in one cause is probably not true in
others.
Read carefully, and you will see even Rudy Severns says that, so his gold
standard isn't gold.
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
Jerry Sevick, W2FMI, has an interesting comment about the 120 number in
his book, The Short Vertical Antenna and Ground Radial. At the end of
the first chapter he notes:
...it should be mentioned that the world standard for the number of
radials to be used with verticals in the AM broadcast
could happen. But that may be nit picking.
Jim - KR9U
From: JC N4IS [mailto:n...@comcast.net]
Sent:
Wednesday, February 05, 2014 10:45 PM
To: jbw...@comcast.net; 'Tom
W8JI'; he...@vitelcom.net;
topband@contesting.com
Subject: RE:
Topband: circular polarization on 160m
James
You brought
I'll have to look into that, Gary! Mine is much bigger.
I have a 25kW continuous 50 KW intermittent at the power pole.
It runs from a tractor PTO. All I do is back one of tractors up to it and
away we go. What I like about this arrangement is I don't have to exercise
it. It is always in
Gee, that should work great, Tom! How is the shaft rotatoion speed
controlled to maintain 60 Hz?
Tractors are like almost any other thing that has an engine and a manual
throttle control, including lawn mowers. They have engine speed feedback
that works like mechanical ALC. It isn't like
JA stations.
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
is a good null.
The no free lunch rule is, as usual, in full force. We simplify by using one
support and decrease length, and we lose other nice things.
We have two short verticals phased, instead of what would be three or four
with wider spacing.
73 Tom
_
Topband Reflector
Regardless, I am not sure if any sort of descriptive logical explanation
will ever allow me to understand what is going on with this antenna but I am
beginning to get comfortable with the modeling. The bigger question to me
is; do you think the 4NEC2 model results faithfully represent what is
You can temporarily use an inductor in series with the cap to extend the
range. It will not be a good idea for transmitting, but OK for tuning.
- Original Message -
From: Carl Braun carl.br...@lairdtech.com
To: Tom W8JI w...@w8ji.com
Cc: 160 topband@contesting.com
Sent: Tuesday
wave being useful.
The bottom line is we are S/N driven on HF, not absolute signal level.
What ratio of V to H signal levels do you expect, Carl? What direction is
the rotation? I'm assuming this is actually a circular signal, and not
something rotating very slowly that is causing fades?
73 Tom
time-sync rotation at that
slow fading rate.
Someone correct me if I am wrong.
73 Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
claiming the rotational direction makes a difference, that
implies the wave is circular. But if the wave were circular, he would not
have fading on a linear antenna.
73 Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
propagation, a circular polarized system is a net detriment.
73 Tom
- Original Message -
From: Carl Luetzelschwab carlluetzelsch...@gmail.com
To: topband@contesting.com
Sent: Monday, February 03, 2014 12:16 PM
Subject: Topband: circular polarization on 160m
I hope everyone has had a chance
the vertical section was still suppressed and the top 29' was resonating.
With this in mind I decided to run a shunt wire from the top to see where
the antenna resonates. Here's what I found..
I was afraid the tower was messing up the L. This is what happens when they
are are nearly
So, i'm assuming you're suggesting that I drop the gamma arm down to the 67'
level and see what the impedance looks like? If so, I'm guessing the series
C required to tune would increase in value?
There will be some tap point where the shunt capacitor is not required.
Eliminating the shunt
The major issue with dielectrics is dissipation factor at 2 MHz, which
affects losses and Q. Dissipation factor is not published all the time. I
can't find dissipation factor for mineral oil.
- Original Message -
From: Bill Wichers bi...@waveform.net
To: Tom W8JI w...@w8ji.com
Cc
, but no one can say how much. The last resort for me
would be no hats. Perhaps you can use T elements with loading wires away
from foliage that might change tuning or losses?
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
Still I am intrigued by the thought of a remote tuning capacitor via
hydraulic tubing :-). The capacitor plates could be as simple as two
concentric cylinder conductors with appropriate spacers. I betcha crud
collecting on the top of the oil would set voltage limit.
I would be as concerned,
You might be dealing with AM BCB being detected by the meter - and masking
what you are looking for.
No, because he gets a dip to zero reactance.
If that happens anywhere, there is no BCI.
73 Tom
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Topband Reflector Archives - http://www.contesting.com/_topband
Very true but the RF is still in the oil dielectric from the coax
connector to the hot end of the resistor.
Not the same at all.
Loss tangent is meaningless in the dummy load application because impedance
is low (weak electric field). There is very little displacement current
compared to
Tom
Maybe you saw my post where I stated that the MFJ plunged to a minimum
reading of 4 0hms at 1825? Does this reading mean that the L is near ground
potential and 'in union' with the grounded Skyneedle at that freq?
It could be from a few things, but two closely spaced conductors
?
The coil would have almost no effect. The loading wires effect would depend
on angle.
73 Tom
73 de Björn,
SM0MDG
8Q7BM
SE0X
_
Topband Reflector Archives - http://www.contesting.com/_topband
-
No virus found in this message.
Checked by AVG - www.avg.com
Version
grounding of the + power supply lead
Sincerely, MFJ
but silly me, I went ahead and added the transformer so they could
pretty much connect it any way they like without blowing up their radio or
having distortion.
73 Tom
_
Topband Reflector Archives - http
where significant changes are possible without a
significant height increase are:
1.) reducing foldback of the hat
2.) improving the ground system
73 Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
worse situation.
Advising people to not isolate grounds on audio lines between different
cabinet grounded pieces of gear is a reversal of progress made with
interfaces. It really can only bring problems to all of us in the long term.
73 Tom
_
Topband Reflector Archives
the way we want, but it
virtually never happens.
Good engineering plans around the imperfections.
73 Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
I have an omega matched 120 foot tower and I apparently have a bad vacuum
variable capacitor. Upon applying more than about 300 watts, the SWR goes
off scale. Tuning it out and trying again, yields the same thing.
The question is which capacitor is the culprit. These are surplus Soviet
caps
headphone lines, because they serve multiple desks, all have isolation
transformers. I suppose I could run a big copper buss bar across the room,
but it seems more logical and safer to just spend $2 on a transformer at
each radio. :)
73 Tom
_
Topband Reflector Archives - http
no
manufacturer in their right mind would listen to that advice. ANY good
interface by almost any manufacturer has shield isolation, with a chassis
bond only at one point. If they don't do that, the help lines get busy with
complaints.
73 Tom
_
Topband Reflector Archives
and besides the NH0 being on 1826 this morning listening up, there were no
spots on the FT5.
:-)
- Original Message -
From: Merv Schweigert k...@flex.com
To: topband@contesting.com
Sent: Monday, January 27, 2014 10:50 AM
Subject: Re: Topband: FT5ZM
Now thats a strange one Milt,
Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
were still there, make measurements with 3 dB of wobble in the readings and
pick the numbers they liked, and call it conclusive evidence.
73 Tom
_
Topband Reflector Archives - http://www.contesting.com/_topband
After making all of the recommended changes, I hooked up my MFJ and got
650 readings regardless. When connected to a 75 ohm dummy load, it
reads completely normally, as does shorting the input (R=0_ If I had
managed to damage the MFJ with DC voltage on the input, would you expect
no readings
Hi Pete,
You are going to have to trust me on this one.
You really should ***NOT*** be measuring the input of the bias T with the
MFJ 259 B analyzer with the configuration you have.
You can damage the 259 unless you use a smaller series cap and a shunt choke
to protect the 259. The most
The Hammond is 400 mA and probably OK, I never used one.
I use something like these 100 uH from Mouser Electronics:
542-73F104AF-RC
or depending on current
542-5250-RC
- Original Message -
From: Pete Smith N4ZR n...@contesting.com
To: Tom W8JI w...@w8ji.com; Richard (Rick
.
You should use the .01 as a coupling cap and the .1 as a bypass if that is
all you have. :-)
The RF choke may also be changing inductance from DC current, but first you
need to make life easier on the 259 by changing the caps around and by
bypassing the RX port with a choke.
73 Tom
Thanks to everyone for their suggestions - consensus seems to be that the
homebrew chokes are not enough reactance at 1.8 MHz, so I'll get some
store bought ones at 220 uH or more. I tried battery power for the whole
system, but no difference. I'm going to try battery power for the remote
However, I did run into an antenna design that was significantly different
(to me, anyway) last month, in an old article about inverted-Ls by L.B.
Cebik. He showed an inverted-L fed at the transition from vertical to
horizontal. Open-wire line ran down and away from it at a 45 degree angle.
Indeed. I've had problems with ICE 196 receiver protectors for several
years. I assume the intermod is generated by the diodes in those devices,
though I do not know that for a fact. The problem occurs on nights when
propagation is very good both in the AM BC band and shortwave in the 5-7
MHz
I use protection diodes on the front end of my W1FB preamps (as well as
before an IC amp in the preamp, and on the output of the preamp) and have
never been able to detect receiver performance degradation on 160 meters
due to the clamping diodes (had to include the diode clamps before the IC
amp
milliamperes in severe stuff. The transients from nearby
strikes can be amperes, but the slew rate is so high they will not go
through a choke or resistor anyway. Reducing any voltage from close
discharges takes a close gap or a low impedance RF path.
73 Tom
_
Topband Reflector
bar with multiple champhered holes,
with the Phillystran woven through from side-to-side? With enough weaves,
this should self-tension with just a single clamp on the far end.
Regardless, I would test pull and see what breaks first at what tension.
73 Tom
_
Topband Reflector
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