[Elecraft] RFI in audio chain

Sun Nov 22 20:59:16 EST 2015

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

> Jan Ditzian <mailto:ditzian at windstream.net>
> Sunday, November 22, 2015 6:32 PM
> In response to the balun recommendation from several hams, I apologize 
> for forgetting to mention that the vertical has an "ugly balun" both 
> at the antenna and near where the feedline enters the house.
>
> Part of the reason I put the question to this group, after first 
> thinking that the amps group could help, was the fact that the IC-730 
> shows no RFI, while the K3 shows extreme RFI.
>
> Thanks,
>
> Jan, KX2A
>
>
>
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> John Kramer <mailto:jkramer at iafrica.com>
> Sunday, November 22, 2015 5:36 PM
> 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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>
> ______________________________________________________________
> Elecraft mailing list
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> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to aldenmcduffie at sunflower.com
> Jan Ditzian <mailto:ditzian at windstream.net>
> Sunday, November 22, 2015 5:02 PM
> 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
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to aldenmcduffie at sunflower.com
>

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