[TowerTalk] swr 75ohm

[Edward Mccann]

FYI, the Sark-110 also allows selection of feedline impedance, and the ability to display resonance and SWR and other parameters of interest.

 Great user support. Check out Melchor Varela or Sark-110 on Google for examples. You-tube demos describe ease of operation. In my opinion the most advanced of its ilk, before leaping into two-port land.

Ed McCann
AG6CX


Sent from my iPhone

> On Jun 7, 2019, at 12:04 PM, Jim Brown <jim at audiosystemsgroup.com> wrote:
> 
> SWR on a transmission line is determined by the match between the load (the antenna) and the line. Most SWR meters are calibrated to 50 ohms, so will give an incorrect reading. Among other things, this will show resonance at the wrong point. So to find that resonance, you want to set the meter to 75 ohms if you're using RG11.
> 
> On the other hand, power amps are designed to work into a 50 ohm load, and some (especially solid state amps) will reduce power to protect their transistors if the match is poor.
> 
> I feed my high dipoles for 40 and 80M with RG11 to reduce line losses, and use matching networks to make the power amp happy.  I use stubs for this, but most hams use an antenna tuner.
> 
> 73, Jim K9YC
> 
>>> On 6/7/2019 3:09 AM, Kostas SV1DPI wrote:
>>> read SWR referenced to 25, 50, or 75 ohms. VERY useful if you want to find the resonance of a high dipole fed with RG11. Used it five times this week to do that.
>> 
>> Hello Jim
>> 
>> Can you explain it better? If I use rg11 (75ohm) coax to connect the dipole, do I need to switch the analyzer to 75Ohm? If I have it to 50ohm what do I count?
>> 
>> ...73 de Kostas SV1DPI
>>  (One of SZ1A-EP6T)
> 
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