[Elecraft] EARC End Fed 6-40 question (Was Re: cobweb antenna)

[Jim Brown]

On 5/31/2013 12:35 PM, Jeff Ellis wrote:
> Will adding a number of ferrite on the feed line help choke the RF? Will winding the feed line around a tube to make an air choke work? I guess that one is cheep enough I should just try it. Buying 10 or more ferrite to clamp to the line costs more;)

Wrong approach to chokes.  Study http://k9yc.com/RFI-Ham.pdf  and all 
the Power Point on Coax Chokes at http://k9yc.com/publish.htm

> What about using a longer feed line? I really don't want to add a counterpoise and the instructions said it does not need one. I could use the 30' antenna wire it came with if that is going to help. I would not think so since its resonate on so many bands and tunable on the others.

I don't know what antenna you're talking about, but ALL end fed wires 
and nearly all verticals need some sort of counterpoise, regardless of 
what someone trying to sell you their antenna tells you to the contrary. 
It's simple physics.  The fact that you don't have one is probably why 
you have "RF in the shack" -- the return current for that wire has 
nowhere else to go except back down into your rig.

Also, an antenna that ends in the shack will usually put a lot of RF in 
the shack if it's working well as antenna. That's its job -- it's 
INTENDED to radiate, and any antennas near it (your USB cable, other 
computer cables, audio cables to the computer, mic cables) will act as 
receiving antennas, and the received RF will be coupled into equipment 
by Pin One Problems (improper termination of cable shields). The 
solution is to choke those unintentional antennas. Again, see the RFI 
tutorial.

Another issue, if you're using a K2, is that the serial cable that was 
built from instructions (and the parts provided) used parallel 
conductors rather than twisted pair.  That was a VERY poor design choice 
-- parallel conductors are very susceptible to RF and other noise, and 
twisted pair inherently rejects RFI and noise.  That's why CAT5/6/7 
cable is twisted pair.

73, Jim K9YC