Re: 75ohm Impedance question K3S and Antenna side.

Posted by ae4pb on Mar 31, 2020; 6:06pm
URL: http://elecraft.85.s1.nabble.com/75ohm-Impedance-question-K3S-and-Antenna-side-tp7659364p7659387.html

The 200' run is Cable TV hardline (1/2") 75 Ohm, that's where the UnUn would go (maybe).

Jerry Moore
Cell: 803-431-1870

-----Original Message-----
From: Victor Rosenthal 4X6GP <[hidden email]>
Sent: Tuesday, March 31, 2020 1:58 PM
To: [hidden email]; [hidden email]
Subject: Re: [Elecraft] 75ohm Impedance question K3S and Antenna side.

I don't think you need a unun because the additional loss due to SWR running RG/6 at 2:1 is only 0.381 dB, and the unun itself would certainly have some loss.
But the loss in 200' of RG/6 even at 1:1 is about 2.9 dB! That is almost half your power. RG/8 would have only 1.9 dB loss, and with a probable SWR of about 1.5:1 you would have a total loss of 2.2 dB.
Even better would be Belden 9913 or similar coax, which would give you a total loss of 1.6 dB.
All these facts and more are available at <https://www.qsl.net/co8tw/Coax_Calculator.htm>

73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 31/03/2020 19:39, [hidden email] wrote:

> I'm about to pull the trigger on a Hustler 6BTV (6-Band, 80, 40, 30,
> 20, 15,
> 10 meters). It will be temporarily installed (with radials) about 200'
> away from my house. I'd like to run CATV "hardline" but I'm not sure
> how to get a
> 2:1 UnUn with a wide enough bandwidth on the antenna side (the
> impedance with 60ish radials should be in the 35ohm range). In
> addition I believe I will be ok on the RIG side to just connect RG6
> (75ohm) to the hardline and direct to the rig since my K3S can match
> the impedance. Is this essentially correct and is there a better way
> to do this? I'm trying to minimize losses for the distance run and still have a decent transmitted signal.
> Thanks in advance.
> Yeah, I should know this stuff but I can't know everything 100%.
>
> 73 es
> De AE4PB
> ..
>  
>
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