Jim,
You'll see I said "it's about stopping the ladderline, and more
importantly the coax, from becoming part of the radiating structure."
The reason I suggest that CM on the coax is more problematic is that in
most installations the coax ends up in the shack/house close to all the
noisy/RF-vulnerable equipment, whereas the ladderline is likely some
distance away.
73,
Steve G3TXQ
On 03/02/2011 16:36, Jim Brown wrote:
> On 2/3/2011 12:28 AM, Steve Hunt wrote:
>> As you realise, adding a choke to the G5RV is not primarily about
>> improving the match or saving dB - it's about stopping the ladderline,
>> and more importantly the coax, from becoming part of the radiating
>> structure.
>>
>> Chances are the coax comes very close to equipment in the shack/home
>> that is susceptible to RFI, and that generates noise on RX; it probably
>> then connects directly to the household mains earth. You don't want it
>> becoming a part of the antenna!
> This is exactly right -- except that common mode current is equally
> possible, and equally undesirable on parallel wire line as compared to
> coax, BECAUSE of the noise coupling issue, AND to prevent the feedline
> from radiating TX RF where it is more likely to couple to your
> neighbor's stereo rig, AND to prevent it from conducting common mode
> current to the shack, where it excites Pin 1 Problems.
>
>> Varney didn't have that problem - no PCs, digital 'phones, plasma TVs
>> etc in his shack when he developed the antenna
> Right!
>
> 73, Jim Brown K9YC
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|