[Elecraft] RFI in audio chain

[Bob McGraw - K4TAX]

There is nothing better than "doing it right"!  Great job Phil.


73 Bob, K4TAX


On 11/22/2015 7:59 PM, Phil Anderson wrote:
> Hi Jan,
>
> I'm guessing, as several others have discussed using a balun at the 
> base of the vertical, that the problem is interference running on the 
> outside of the coax feed. I'm using a STEPPir vertical for 40 through 
> 10. I tried several baluns with no satisfying success. I then decided 
> to build a SPGS (single point grounding system) on the outer wall next 
> to my shack in the back yard. My SPGS is enclosed by DX Engineering's 
> "Grounding and Utility Encloser," (DXE-UP-2P)  and I installed in that 
> three ALPHA-DELTA lightning arrest (surge protectors) (for three 
> different antennas, one being a Beverage), and a CONTROL LINE 
> PROTECTOR, (DXE-IS-RCT), that protects my Steppir vertical antenna 
> control system. In addition to that I ran #6 copper to the house 
> utility box ground (from the antenna ground) AND  (perhaps most 
> important) ran three ground rods spread out (at twice the length of 
> the 8' rods) and connected all of that to the vertical grounding plate 
> (of the SPGS box) The important thing is that I did not use #6 wire 
> from the vertical to the SGPS box; instead, I used 2 inch wide copper 
> strip that is bonded to the rods with copper plates and connections at 
> each end of the run. The 2 inch copper strip is then attached to the 
> SPGS 14 x 14 plate  (with another ground rod) just outside the house. 
> THE THEORY IS THAT THE WIDE STRAP PROVIDES FOR A VERY LOW RF IMPEDANCE 
> AT THE FREQUENCY OF OPERATION. This substantially shunts off any 
> interference returning on the outside braid of the coax from the 
> vertical. In addition on the inside (at station) I ran a strip of the 
> 2 inch copper along the back of the station table and then smaller 
> braided strap from the copper strip to each major piece of equipment 
> on the station (a reverse V from the SPGS if you will) : DELL OPTIPLEX 
> COMPUTER (station computer), two 19 in flat screens, my fully loaded 
> Elecraft K3 with P3 WinkeyerUSB, and Astron switching supply.
>
> The result was immediately apparent: the spikes I had been receiving 
> that were spaced up and down the 40 through 20 bands as noted on the 
> P3 panadapter where now completely gone. An added surprise was that 
> the noise floor even went down a bit (and I live two blocks from a 
> shopping mall!). Prior to this large station upgrade  - inside and 
> outside the house - I would even see interference on the 19 inch 
> screens - that is now gone too.
>
> If you like I can send you more detail on what I did, including 
> pictures. I've only been testing it for a week so may find some 
> glitches....but so far very happy.
>
> 73 and good luck. Phil Anderson, W0XI, Lawrence, KS