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RF in the shack
#1
I have a bit of an RF issue in the shack. For a demo of the issue, please watch this YouTube video: https://www.youtube.com/watch?v=AMDiHT7BEgg

I'm working with the developer of the CWKeyer product to resolve the issue. At first I didn't think I had an RF issue in the shack. The issue is only on 80M. My shack is on the second floor of my house, aluminum sided. I'm using an end fed antenna that is about 18 feet from the rig but the feed line is about 65' (it goes around the outside of the house then through a window, but the actual antenna feed point is pretty close to the rig). The issue you see in the YouTube video happen when only 10W is used on TX. The end fed is used for 40, 80 and 160M and the rig / antenna works fine other than this CW keyer. I do hear a little "something" in my headset on 80M when I TX but very minor. I have a air core choke at the feed point (5 turns of feedline, about 5 inches in diameter).

I added two additional 14 gauge wires (total of three) from my shack to house electrical ground (about 22 feet away). Looking for ideas to eliminate the RF issue.
I have toroids on everything except the feed line. Would adding a Toroid for choke at the feed point be a good thing to do, or just tossing money out the window?

This is not a show stopper, I mostly work 20m and higher but occasionally want to work 80 and 160 which makes me switch to using the end fed.

Thoughts?

73,
KC1AXJ
73, Steve - KC1SA
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#2
I have an idea. I have some adhesive copper tape for shielding. You can use this to tape down the inside covers of your keyer and then ground to a single point to reduce external noise/radiation.

I suspect your antenna has a strong lobe in the direction of your keyer position. Shielding may alleviate this.

LMK if you want to try this.

Either that or try changing the decoupling capacitors C3 & C5 on the paddle inputs.

They are .01uF. You could try scoping these points while transmitting phone on 80M to see if it's being induced in the paddles.
K1RCT - Rob
W1NRG Station Activities Manager
Home Email

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#3
I changed the counterpoise a bit today and that helped matters. The counterpoise was nearly on the ground so I guess it acted more like a single radial rather than a counterpoise. Lifting the counterpoise to about 10 feet did change the characteristics of the antenna (had to re-tune the the TX) and now I can TX to about 75W without causing interference while on 80M, but now my 160M band is wacky now for interference. I guess that is a characteristic of end-fed antennas. I spoke with KZ5R (BalunDesigns) and said a 1:1 balun near the shack (not the feed point of the antenna) will do the trick. That's my next step.

What's really 'cool' about this rf issue is that I tie the shack ground (now improved with three 14 gauge wires fed to the house electrical ground) to the keyer and fire up the rig and transmit on 80 or 160m, that will cause the keyer to go bonkers. Just ground, no other connection (the keyer is battery operated). At least with no ground I can operate 80m provided I keep the power low.

(11-25-2015, 03:16 PM)KC1ACN Wrote: I have an idea. I have some adhesive copper tape for shielding. You can use this to tape down the inside covers of your keyer and then ground to a single point to reduce external noise/radiation.

I suspect your antenna has a strong lobe in the direction of your keyer position. Shielding may alleviate this.

LMK if you want to try this.

Either that or try changing the decoupling capacitors C3 & C5 on the paddle inputs.

They are .01uF. You could try scoping these points while transmitting phone on 80M to see if it's being induced in the paddles.
73, Steve - KC1SA
Reply
#4
(11-24-2015, 08:39 PM)KC1AXJ Wrote: Thoughts?

73,
KC1AXJ

Could it be a ground loop someplace? I found a few times that ungrounding the offending accessory actually cured the problem.

Also your items should not be chain linked together with ground. Each one should have it's own ground going to the ground point.

Al
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#5
What a crazy hobby we have!
K1RCT - Rob
W1NRG Station Activities Manager
Home Email

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