On 2/8/2021 4:19 PM, JOE MIXSELL wrote:
Wonder if anyone has seen this behavior and if so what might you have
done to eliminate it. Set up is TS 590, MFJ 1204 and HP labtop. Cabling
supplied by MFJ with the 1204 unit. Antenna is ground mounted vertical
about 35 to 40 feet from shack. For a power out level of 25 watts or
less the transmitter seems to function normally but at a higher level
the output from the transmitter is irregular, varying rather than a
steady output level. I'm believing that there is some RFI
susceptibility in the 1204 itself or the cabling. Has anyone seen
something similar and if so what did you do to eliminate the problem.
Lots of study material on my website about curing RFI. First, study this
one about bonding, and do it in your station.
http://k9yc.com/GroundingAndAudio.pdf
Second, use ferrites on cables connecting equipment in your shack as
described in this tutorial on killing RF noise. The document is geared
to killing RX noise, but the same Laws of Physics apply to receiving
interference.
http://k9yc.com/KillingReceiveNoise.pdf
Third, look at your vertical. Is it one that requires radials? Does it
have resonant radials for every band? If it doesn't, or if it doesn't
have enough, the vertical will use your coax shield as a radial, putting
RF in your shack.
And finally, use this Cookbook to build a common mode choke to be
installed at the base of the vertical. This will keep RF off of the coax.
http://k9yc.com/2018Cookbook.pdf
73, Jim K9YC
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