CC FYI Bill...........very good results.....
Phil
*From:* Phil Anderson <[email protected]>
*Date:* Sunday, November 22, 2015 7:59 PM
*To:* Jan Ditzian <[email protected]>
*CC:* [email protected], Phil Anderson
<[email protected]>
*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: [email protected]
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*From:* John Kramer <[email protected]>
*Date:* Sunday, November 22, 2015 5:36 PM
*To:* Jan Ditzian <[email protected]>
*CC:* [email protected]
*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 <[email protected]> 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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