[Elecraft] Fwd: Re: RFI in audio chain

Sun Nov 22 21:06:40 EST 2015

CC FYI Bill...........very good results.....

Phil

> *From:* Phil Anderson <aldenmcduffie at sunflower.com>
> *Date:* Sunday, November 22, 2015 7:59 PM
> *To:* Jan Ditzian <ditzian at windstream.net>
> *CC:* Elecraft at mailman.qth.net, Phil Anderson 
> <aldenmcduffie at sunflower.com>
> *Subject:* [Elecraft] RFI in audio chain
> 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
> email: aldenmcduffie at sunflower.com
>
>
>
>
>
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> *From:* John Kramer <jkramer at iafrica.com>
> *Date:* Sunday, November 22, 2015 5:36 PM
> *To:* Jan Ditzian <ditzian at windstream.net>
> *CC:* Elecraft at mailman.qth.net
> *Subject:* [Elecraft] RFI in audio chain
> Jan
>
> The easiest, quickest and cheapest method is to wind yourself an "ugly 
> balun" in your coax cable line.
> It must be located OUTSIDE your shack to choke the common mode 
> currents from entering the shack.
> Wind about 15 - 20 turns of your coax on a 6" PVC pipe. This will give 
> you about 2500 ohms choking
> impedance.
>
> If there is still RFI getting in the shack, then purchase a commercial 
> choke either from
> http://www.balundesigns.com/model-1115d-max-choking-1-1-balun-1-54-mhz-5kw/ 
>
> this will provide about 10 - 12 000 ohms of choking impedance, or buy 
> one from
>
> http://myantennas.com/wp/product/cmc-130-3k/
> This one will give from 12 000 - 15 000 ohms of choking impedance.
>
> These common mode chokes merely get plugged inline in your coax cable. 
> Always better to locate
> them outside the shack
>
> 73
> John
>
>
>
>
> On 23 Nov 2015, at 1:02 AM, Jan Ditzian <ditzian at windstream.net> wrote:
>
> I have a problem that appears to be changing, but I could use some 
> help. The problem is RFI in the audio input (microphone input) when I 
> use my vertical antenna on 40 meters. Here is a rundown of what has 
> happened:
>
> I have a 67-foot elevated vertical that I can use on 80 and 40, and it 
> works fine on CW. However, on SSB, both bands, there clearly is 
> feedback; there is no feedback on the other bands where I use a C3 
> yagi. Initially, the feedback was so bad that the rig would go into 
> oscillation, and I had to turn the amp to standby.
>
> I recently purchased the new KSYN3A and decided to install it. I 
> replaced the K3 with my IC-730 backup, using the hand microphone that 
> came with the 730. The 730 did not have any RFI. I finished the 
> modification and returned the K3 as the operating rig. Now, the RFI on 
> 40 seems to have diminished substantially or disappeared, but it still 
> happens on 75/80. However, it seems to be much less there as well. I 
> do not suspect that the KSYN3A had anything to do with this, but 
> perhaps I tightened connections better when I returned the rig to 
> service. I also redid some ground connections.
>
> The microphone for the K3 is an Audio-Technica that works well 
> everywhere else. It has a long cord, though. I put a few toroids on 
> the cord near the microphone connector and that has possibly reduced 
> RFI a little, but it is still there.
>
> Is there a possibility that a bypass capacitor is bad, or has someone 
> else had the problem and solved it externally to the K3? For instance, 
> has anyone found that a long string of ferrite beads has cured this 
> problem?
>
> Despite decades of operating, I am hardly a troubleshooting hotshot, 
> and I would appreciate guidance.
>
> Thank you,
>
> Jan, KX2A
>
>
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