Topband: Vertical choke needed?

[Jim Brown]

On 12/31/2020 5:01 PM, Michael Walker wrote:
> Hi Ken
> 
> Chokes at both ends of the feed line are always a good idea.

At the base of the antenna, yes, so that the feedline doesn't become a 
radial. More are probably wasted money. See my latest Cookbook at 
k9yc.com/publish.htm
> 
> I have a similar setup to you but with elevated radials and I have Mix 31 chokes right at the base of the antenna with an UNUN since I am using 75 ohm coax and then more chokes at the antenna switch.
> 
> You can’t use enough chokes.

The only good reasons I've discovered for using chokes on feedlines 
anywhere but at the feedpoint are 1) to break up the feedline into 
lengths that won't be parasitic becoming parasitic elements to other 
verticals; and 2) to prevent noise pickup by a mechanism quantified as 
the Transfer Impedance of the cable, whereby shield current is converted 
to a differential voltage inside the cable.

W3LPL has observed that #2 should not be an issue with coax laying on 
the ground. I am not so optimistic with the CATV RG6 we often use for RX 
antennas, whose shields are VERY flimsy at MF, but I always value 
Frank's observations.

As to chokes at the station -- if they solve problems, they're putting a 
band-aid on badly done (or missing) grounding and bonding. See N0AX's 
ARRL book on the topic, and/or the slide deck for my talks about it.

http://k9yc.com/GroundingAndAudio.pdf

73, Jim K9YC