Wideband noise on 6 meters

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  • Updated 5 years ago
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I was just playing around with my 6700 and 0.13.10 and listening to 6 meter beacons. When I heard one, I would tune another transceiver to the same frequency to see if I could hear it. Each transceiver was using its own separate antennas. By accident, I tapped the CW key and I noticed that after the short tone was sent and while the 6700 was still hanging in semi-breakin, the noise floor of my other transceiver jumped up about 10 dB. Being curious, I enabled the MOX to see what would happen. Every time I would enable the MOX, the noise floor on the other transceiver would raise up about 10 dB. When I stopped MOX, it would drop back down. Understand, I was not transmitting, I was just enabling the MOX. I was running both transceivers off the same linear power supply. I changed that and ran each transceiver off its own supply and nothing changed with the noise. I tuned around and the noise was evident from about 38 MHz up to about 65 MHz. It was greatest between 50 and 52 MHz, then it dropped significantly. Any ideas?
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Tim K8XS

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Posted 5 years ago

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Greg - K5GJ, Elmer

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Tim
I haven't seen this. I've escalated to Engineering to see what's up. Tnx for your patience! 73, Greg -K5GJ
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Greg - K5GJ, Elmer

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Tim:

Sorry for the delay but it's been pretty hectic around here with all the software testing....

I took the time this morning to set up and test your Wideband Noise report on 6m. I'm using a FLEX-6700 at 100W fed into a Steppir at 50'. 30 feet away I have a 6m Dipole at 5' above the ground connected to a FLEX-6500. To make it "worst-case", I pointed the beam at the dipole and turned up RX Pre-amp on the 6500 to +20dB.

TX on 50.125
50.145MHz - OFF -112.7, MOX -109.3, TUNE (100W) -106.0
50.200MHz - OFF -112.0, MOX - 110.0, TUNE (100W) -106.8
50.500MHz - OFF -111.0, MOX - -110.6, TUNE (100W) - 110.
52.00MHz - OFF - 111.0, MOX -111.0, TUNE (100W) -111.0

Based upon this quick un-scientific test, there is some close in noise associated with the transmitter but it drops quickly as expected. We weren't able to discern any broadband noise pedestal as you described.

Would you mind describing your test setup in detail and I'll do what I can to duplicate it.

If I can't duplicate it here, it's possible there is some issue with your radio. In that case I'd like to move this to a Zendesk ticket.

Tim, thanks for the help in investigating this.

73,
Greg - K5GJ