Re: Topband: RG-179 Coax

[Richard (Rick) Karlquist]

On 2/14/2020 1:04 PM, Jim Brown wrote:

On 2/14/2020 11:40 AM, Fred Moeves wrote:

Can you figure out impedance of coax with a device like the Rig Expert?


Yes, if it's a model that can be calibrated, and if the calibration is 
properly done, and if it's a model that can export measurements to a 
computer. Calibration requires of Standard Short, Open, and Load parts. 
Once you've calibrated, sweep a length of the coax with the far end open 
and again with it shorted. Export the data to a computer, then import it 
into AC6LA's free ZPlots Excel spreadsheet and follow his instructions. 
For the measurements, the coax must be connected at precisely the same 
point as where the calibration was done.


Before attempting this, study parts of the manual for the equipment that 
talks about the "measurement plane."


73, Jim K9YC



This is the "hard" way to measure Zo.  Been there, done that.

The easy way is to attach a small 100 ohm (non-wire-wound) pot to one 
end of the coax and attach the other end of the coax to any old 
impedance meter.  Even an MFJ-259 will work.  Now adjust the pot until 
you see a constant impedance across all frequencies.  Don't worry about 
what the impedance meter says this impedance is.  Instead, measure the 
DC resistance of the pot.  More accurate.  Foolproof.


Rick N6RK
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Re: Topband: RG-179 Coax

[Jim Brown]

On 2/14/2020 12:59 PM, CUTTER DAVID wrote:
However, in my experience cmc causes erroneous swr readings on antenna 
analysers I have used.  I would say it's almost useless to measure swr 
until cmc is eliminated.


The proper location for the first common mode choke is at the feedpoint. 
When it is inserted, it 1) adds to the length of the line; and 2) 
isolates the feedline from the antenna so that it cannot detune the 
antenna; and 3) may shift the APPARENT resonance of the antenna by 
virtue of this isolation, AND by whatever impedance transformation along 
the feedline that occurs by the addition of the choke.


This is all predicted by the fundamentals of how transmission lines 
work. Consider any real antenna -- it's feedpoint Z will be affected by 
height, surrounding objects, etc., AND will be different at every 
frequency. VERY few antennas have a feedpoint Z that is precisely equal 
to the feedline Zo over the range of operating frequencies (i.e., the 
width of a band), so any change made to the feedline can change the 
apparent resonance.


Take the simple example of a dipole resonant on the band. It's feedpoint 
Z at resonance will vary depending on its height above ground, soil 
conductivity, and surrounding objects. Specifically, the soil acts as a 
passive element of the antenna -- the reflection from it changes the 
feedpoint Z just like any other passive element, and HOW it changes it 
depends on the strength of the reflection and the phase shift 
corresponding to 2X the antenna's height. There are plots in ON4UN's 
"Low Band DXing" that show how feedpoint Z oscillates around its nominal 
value with height for certain ground conductivity values, and modeling 
software like NEC can predict it. In general, dipoles that are 
electrically low tend to be a better match to 50 ohm feedline, while 
those that are electrically high tend closer to 75 ohm coax. My high 
dipoles (hung at about 40m high from tall trees) for 80 and 40M measure 
in the range of 85 ohms at resonance. The measurement is done with a 
vector analyzer in the shack and exported to SimSmith, where the 
electrical length of the feedline is subtracted from the measured data. 
The feedline length is obtained by a TDR.


Similarly, feedpoint Z of vertical antennas will be affected by the 
radial/counterpoise system, ground losses, and surrounding objects.


73, Jim K9YC
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Re: Topband: RG-179 Coax

[Jim Brown]

On 2/14/2020 11:40 AM, Fred Moeves wrote:

Can you figure out impedance of coax with a device like the Rig Expert?


Yes, if it's a model that can be calibrated, and if the calibration is 
properly done, and if it's a model that can export measurements to a 
computer. Calibration requires of Standard Short, Open, and Load parts. 
Once you've calibrated, sweep a length of the coax with the far end open 
and again with it shorted. Export the data to a computer, then import it 
into AC6LA's free ZPlots Excel spreadsheet and follow his instructions. 
For the measurements, the coax must be connected at precisely the same 
point as where the calibration was done.


Before attempting this, study parts of the manual for the equipment that 
talks about the "measurement plane."


73, Jim K9YC


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Re: Topband: RG-179 Coax

[Fred Moeves]

Jim,

That's what I thought.

Can you figure out impedance of coax with a device like the Rig Expert?

Also I was only sending the info to somewhat confirm it's 75 ohm cable 
because it's not marked.


I was not saying that it's a good or effective choke because the SWR was 
good.


Thank You

Fred KB4QZH


On 2/14/2020 2:02 PM, Jim Brown wrote:

On 2/14/2020 9:11 AM, Fred Moeves wrote:
I put 75 resistor and 50 ohm dummy load on each choke and scanned it 
with the Rig Expert 230 zoom and it seems fine.


Common mode chokes do not affect SWR, and measuring SWR tells nothing 
about their effectiveness. See http://k9yc.com/2018Cookbook.pdf


73, Jim K9YC

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Re: Topband: RG-179 Coax

[Jim Brown]

On 2/14/2020 9:11 AM, Fred Moeves wrote:
I put 75 resistor and 50 ohm dummy load  on each choke and scanned it 
with the Rig Expert 230 zoom and it seems fine.


Common mode chokes do not affect SWR, and measuring SWR tells nothing 
about their effectiveness. See http://k9yc.com/2018Cookbook.pdf


73, Jim K9YC

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Re: Topband: Cheating etc

[Fred Moeves]

Roger,

I agree 100%.

If it's easy enough to get the card I'll send off for it.

I don't chase for the ARRL's certificate.

I have a couple from the 80's and 90's couple DXCC's WAS WAZ...

Truthfully I can't even remember...I don't think I even have 160 DXCC 
from ARRL.


I know I have worked enough ...but it got too expensive...I would rather 
spend the cash on my station.


Like Mike said you are only cheating yourself.


Nick we hear you and understand but I think you have to present your 
evidence to the proper authorities.


To be Top Dog on Topband must be a big deal to some??


As far as I'm concerned I'm Top Dog on Topband ...well in my 
neighborhood anyway.maybe just on my street    ;)



73

Fred KB4QZH


On 2/14/2020 6:43 AM, Roger Kennedy wrote:

Personally, I don't really care what anyone else does !

I achieved DXCC on 160m many years ago . . . and stopped even counting new
countries once I had worked over 200.  (it used to be really hard, as so few
Countries were licensed for Top Band, but these days almost everyone is)

I KNOW I worked those stations . . . but never bothered collecting QSL cards
or applying for some piece of paper to put on the wall. To me it's about the
SATISFACTION of having achieved something.

In fact - as I've stated before on here - I'm really not bothered about
working somebody in a rare country . . . it's working ANY distant station on
Top Band that gives me a buzz . . . and regardless of how many times I've
worked that station before.

The same goes for Contests . . . decades ago I used to actually enter Top
Band contests . . . but it really holds no interest for me having hundreds
of quite easy contacts hour after hour . . . I now just come on to try and
pick out the DX stations in-between all the strong Europeans (again, a
unique problem on 160m, as there is no Skip) - THAT to me is an achievement.

Again, I am not bothered about the people using their Computer to have
contacts . . . it would never interest me in a million years, as I feel
there is no operator or equipment skill involved, so zero satisfaction.  But
hey, if it floats some people's boats, that's up to them.

The only thing that DOES bother me is when people stop coming on Human-based
modes on 160m because they think the only activity is on the Computer modes
!

If more people make an effort to come on the band (instead of complaining)
there WILL be more CW & SSB DX activity on Top Band !

Anyway . . . hope to work some of you in the Contest this weekend. (Had to
put my antenna back up yesterday, as it came down in the Gales we had over
here !)

73 Roger G3YRO

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Re: Topband: RG-179 Coax

[Fred Moeves]

Mike,

I bought some from this Link 
 
.


It seems ok to me.

No markings on it and the guy could use a lesson on how to coil wire.


I put 75 resistor and 50 ohm dummy load  on each choke and scanned it 
with the Rig Expert 230 zoom and it seems fine.


I scanned it from 100khz to 10mhz ... SWR was 1:00 to 1:35... and on a 
50 ohm dummy it was 1:12 to 1:35.


Not really sure if that tells anything but there it is.

I have nothing to measure L or C.

I did try shorting one end of the coax then scanned it with the 230 zoom 
read L and C and then calculate the impedance but didn't look right.


Bad math on my part I'm sure.

I also bought these connectors and the worked just fine...Link 



And Link 2 




I have made four on these chokes now all test the same.

I have one in service and waiting for the rain to stop to install the 
other ones.



I am replacing old chokes that work but take up to much room...I'm sure 
I will see no change when I do this.


The old chokes were made from old Commscope RG 59 with 4" cores..works 
but too big...


Also I can send you a piece if you want to see it or. better yet how 
much do you need?


I think I used 5.5 feet for each choke.

73

Fred KB4QZH


On 2/13/2020 6:31 PM, W0MU Mike Fatchett wrote:
I am looking for a good source for RG-179 coax to build some RX 
antennas.  I tried an Ebay seller and got rg58!!


W0MU
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Re: Topband: Fw: E44CC on ARRL CONTEST

[Tuomas Talka]

They had a good signal over here a couple of days ago but they had serious
problems in hearing. I don't know why they only have a bog in their hotel's
garden. Maybe a some kind of loop would hear better in their noisy
environment.

73, Tuomas OH5JJL


pe 14. helmik. 2020 klo 17.45  kirjoitti:

> Topbanders. . .looks like E44 will be in the contest after all.   73.
> . . Dave, W0FLS
>
> From: f8...@sfr.fr
> Sent: Friday, February 14, 2020 3:02 AM
> To: daraym...@iowatelecom.net
> Subject: E44CC on ARRL CONTEST
>
> ‌Hi David,
>
> so it's OK, we will have 1 station this week end for the ARRL contest and
> help the NA Community to work E44.
> CUL
>
> Best 73
>
> Manu F8FKI
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Topband: Fw: E44CC on ARRL CONTEST

[daraymond]

Topbanders. . .looks like E44 will be in the contest after all.   73. . . 
Dave, W0FLS

From: f8...@sfr.fr 
Sent: Friday, February 14, 2020 3:02 AM
To: daraym...@iowatelecom.net 
Subject: E44CC on ARRL CONTEST

‌Hi David,

so it's OK, we will have 1 station this week end for the ARRL contest and help 
the NA Community to work E44.
CUL 

Best 73

Manu F8FKI
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Re: Topband: RG-179 Coax

[Ham Hicks]

The Amphenol 21-579 I mentioned earlier is very flexible.
KB4BR

-Original Message-
From: Topband [mailto:topband-bounces+ham306=bellsouth@contesting.com] On 
Behalf Of W0MU Mike Fatchett
Sent: Friday, February 14, 2020 2:40 AM
To: Andreas Junge 
Cc: 160 
Subject: Re: Topband: RG-179 Coax

I am making some receive antennas and the coax will be for the choke that goes 
through a torriod.  The cores I have would not take rg6. This is from the YCCC 
receive antenna array.

W0MU

On 2/13/2020 5:55 PM, Andreas Junge wrote:
> Mike,
>
> What’s wrong with RG6? Or the DX Engineering version of it:
>
> https://www.dxengineering.com/search/department/cable-and-connectors/p
> roduct-line/dx-engineering-f6-75-ohm-bulk-coaxial-cable?autoview=SKU&k
> eyword=rg6&sortby=BestKeywordMatch&sortorder=Ascending
>
> $0.30/foot
>
> Plenty good for RX antenna use.
>
> 73, Andreas, N6NU
>
>> On Feb 13, 2020, at 3:31 PM, W0MU Mike Fatchett > > wrote:
>>
>> I am looking for a good source for RG-179 coax to build some RX 
>> antennas.  I tried an Ebay seller and got rg58!!
>>
>> W0MU
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>> Reflector
>

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Re: Topband: RG-179 Coax

[Thomas]

Hi Jim,

I use Belden 9221 miniature 75-Ohm coax for my receive antenna chokes. It is 
very flexible making it easy to wind over the torroid core. I recently bought 
100' of 9221 on ebay for a very reasonable price. It is readily available there 
and seems to do the job.

Thomas - ac7a

> On February 14, 2020 at 4:56 AM Jim Brown  mailto:j...@audiosystemsgroup.com > wrote:
> 
> 
> On 2/13/2020 11:40 PM, W0MU Mike Fatchett wrote:
> 
> > > I am making some receive antennas and the coax will be for the 
> choke
> > that goes through a torriod.
> > 
> > > As Mike understands, RG6 doesn't work. See pages 3 of
> http://k9yc.com/2018Cookbook.pdf
> 
> 73, Jim K9YC
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Re: Topband: Cheating etc

[Michael Walker]

To put it simply

You are only cheating yourself.

It is not up to me to control other adults.

Mike va3mw


On Fri, Feb 14, 2020 at 6:43 AM Roger Kennedy 
wrote:

>
> Personally, I don't really care what anyone else does !
>
> I achieved DXCC on 160m many years ago . . . and stopped even counting new
> countries once I had worked over 200.  (it used to be really hard, as so
> few
> Countries were licensed for Top Band, but these days almost everyone is)
>
> I KNOW I worked those stations . . . but never bothered collecting QSL
> cards
> or applying for some piece of paper to put on the wall. To me it's about
> the
> SATISFACTION of having achieved something.
>
> In fact - as I've stated before on here - I'm really not bothered about
> working somebody in a rare country . . . it's working ANY distant station
> on
> Top Band that gives me a buzz . . . and regardless of how many times I've
> worked that station before.
>
> The same goes for Contests . . . decades ago I used to actually enter Top
> Band contests . . . but it really holds no interest for me having hundreds
> of quite easy contacts hour after hour . . . I now just come on to try and
> pick out the DX stations in-between all the strong Europeans (again, a
> unique problem on 160m, as there is no Skip) - THAT to me is an
> achievement.
>
> Again, I am not bothered about the people using their Computer to have
> contacts . . . it would never interest me in a million years, as I feel
> there is no operator or equipment skill involved, so zero satisfaction.
> But
> hey, if it floats some people's boats, that's up to them.
>
> The only thing that DOES bother me is when people stop coming on
> Human-based
> modes on 160m because they think the only activity is on the Computer modes
> !
>
> If more people make an effort to come on the band (instead of complaining)
> there WILL be more CW & SSB DX activity on Top Band !
>
> Anyway . . . hope to work some of you in the Contest this weekend. (Had to
> put my antenna back up yesterday, as it came down in the Gales we had over
> here !)
>
> 73 Roger G3YRO
>
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> Reflector
>
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Topband: Cheating etc

[Roger Kennedy]

Personally, I don't really care what anyone else does !

I achieved DXCC on 160m many years ago . . . and stopped even counting new
countries once I had worked over 200.  (it used to be really hard, as so few
Countries were licensed for Top Band, but these days almost everyone is)

I KNOW I worked those stations . . . but never bothered collecting QSL cards
or applying for some piece of paper to put on the wall. To me it's about the
SATISFACTION of having achieved something.  

In fact - as I've stated before on here - I'm really not bothered about
working somebody in a rare country . . . it's working ANY distant station on
Top Band that gives me a buzz . . . and regardless of how many times I've
worked that station before.

The same goes for Contests . . . decades ago I used to actually enter Top
Band contests . . . but it really holds no interest for me having hundreds
of quite easy contacts hour after hour . . . I now just come on to try and
pick out the DX stations in-between all the strong Europeans (again, a
unique problem on 160m, as there is no Skip) - THAT to me is an achievement.

Again, I am not bothered about the people using their Computer to have
contacts . . . it would never interest me in a million years, as I feel
there is no operator or equipment skill involved, so zero satisfaction.  But
hey, if it floats some people's boats, that's up to them.

The only thing that DOES bother me is when people stop coming on Human-based
modes on 160m because they think the only activity is on the Computer modes
!  

If more people make an effort to come on the band (instead of complaining)
there WILL be more CW & SSB DX activity on Top Band !

Anyway . . . hope to work some of you in the Contest this weekend. (Had to
put my antenna back up yesterday, as it came down in the Gales we had over
here !)

73 Roger G3YRO

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Re: Topband: RG-179 Coax

[Jim Brown]

On 2/13/2020 11:40 PM, W0MU Mike Fatchett wrote:
I am making some receive antennas and the coax will be for the choke 
that goes through a torriod.


As Mike understands, RG6 doesn't work. See pages 3 of 
http://k9yc.com/2018Cookbook.pdf


73, Jim K9YC
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