On Sat, 26 May 2007 06:24:03 -0600, M. Todd Miskel wrote:
>Is it inherant that a hot front end like Orion is just more
>sensitive to RF, or has TT missed the ball somewhere in
shielding
>the Orion?
Most "RF in the shack" has a "Pin 1 problem" as the root cause.
I haven't looked at the Orion, but my Omni V has a pin 1
problem. My FT1000MP (which drives a Titan 425) has a pin 1
problem that causes RF feedback distortion on 15M SSB with a
dipole that is 150 ft from the shack! I've tamed it with 7 turns
of the mic cable around a #31 2.4 inch toroid (FT-240). A #43
toroid would also work on 15M.
For a detailed rundown of "the pin 1 problem," see
http://audiosystemsgroup.com/RFI-Ham.pdf
The link below shows how to test for RF susceptibility due to
pin 1 problems.
http://audiosystemsgroup.com/AESPaperNYPin1-ASGWeb.pdf
I used my HP 8657A to test my FT1000MP. It showed susceptbility
at the mic jack just above 75M and around 15M. To do the test, I
drove the shield contact as described in the paper, and listened
to my radio on another receiver. The test is pretty simple. You
modulate the RF generator with 1 kHz AM, and tune the generator
over the range of interest. If you hear 1 kHz in the transmitter
output, you have a pin 1 problem.
73,
Jim Brown K9YC
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