Kevin, K3ox wrote:
"I had a R4C many years ago, and found that much (not all) of the filter
blowby in this rx was actually signal leakage around the filters. So I
spent an evening with copper pc board and shield material and empirically
found where the shields "needed" to be."
==========
One of the first things I noticed with my new R-4C in 1973 was
significant filter blowby. I also added shileding in strategic places to
significantly reduce it, but I couldn't completely eliminate it.
My R-4C had the Sherwood 125 Hz filter in it, but none of the Sherwood
mods. During 160-meter CW contests, IMD was quite noticeable with it.
Had I known about the improvement made by the Sherwood mods, I certainly
would have incorporated them.
In 1980 I replaced the Drake C-line with a Kenwood TS-830S which was
better than the unmodified R-4C. IMD was still noticeable, but not as
bad. In other respects the TS-830S receiver was great, and gave me 160m
DXCC #55 in 1984.
In 1998 I finally replaced the TS-830S with a Yaesu FT-1000MP. IMD on
the MP is still noticeable from time to time, even less than the TS-830S,
and is never really a big problem. The MP's noise floor was improved by
about 4 dB when I added the INRAD front-end mod.
73, de Earl, K6SE
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