The following two steps seem to have solved the problem I had on 75 meters,
at least when running the Orion transceiver barefoot.

1) Ran #12 wire through the 2nd-story window sill and down to a 10 feet long
copper clad ground rod. The length of the wire run is about 15 feet. While
this may seem to be an obvious step, at my previous QTH the use of an earth
ground made RF feedback problems worse on some bands.

2) Installed an Amidon FT-240-77 ferrite toroid as a common-mode choke (11
turns) in the Orion's DC power supply cable and located about 18" from the
Orion. I am using an Astron RS-35A linear power supply (the fan on the
Ten-Tec switching PS was too noisy). The cable run between the power supply
and the Orion is somewhat lengthy because the Orion is connected to an
MFJ-1129 multi-outlet strip.

Step 2 above seems to have also corrected an occasional "flakiness" in the
operation of some of the front panel controls, which I had blamed on
progressive failure of the RIT/XIT encoder. Furthermore, for some
inexplicable reason, the computer problem I had with the USB
connected keyboard has disappeared with the installation of the
Orion's power supply cord toriodal filter!

"Owen Duffy" wrote in message
...
On Thu, 26 Oct 2006 14:06:53 GMT, "John, N9JG"
wrote:

When I operate on 75 meter SSB with my transceiver, my computer beeps and
disconnects/reconnects my USB connected keyboard. Note that I do not have
this problem on 40 meter SSB. My computer is located on the second floor
of
a brick house, and one end of my dipole is about 15 feet from my shack.

From comments made by others, I may have to put RF filters on the cables
and wires connected to my computer. I am contemplating the use of
Amidon FT-240-77 ferrite toroids, which have an I.D. of 1.4 inches and
cost $9 each. If I buy in quantities of 10, is there a cheaper source
for this toroid?

Any comments or suggestions on this problem would be appreciated.


John,

You describe a problem that could be caused / exacerbated by one or
both of:
- lack of electromagnetic compatibility (EMC) of your computer; and
- a hostile RF environment.

Before you lay blame at the computer, it is worth whether the RF field
strengths, and conducted and induced currents and voltages in your
shack are unnecessarily high.

You have give very little description of your antenna, feedline, and
station earth... too scant to analyse and offer much advice.

The hint is there that this problem is evident on 80m, while 40m seems
OK. Why is that?

Is the identified PC problem really a manifestation of a "hot" shack?
Have you conducted any experiments to identify excessive common mode
feedline currents in the shack (the same procedures you might follow
if you got an RF burn from something in the shack)?

Owen

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