K5SDR wrote:
> There has been some discussion today about an ECO that addresses a potential
spur issue on 160m CW on the FLEX-5000. We have developed a hardware
modification to the 160m transmit filter section in response to a half dozen
customer reports of a spur 2.4 kHz above the CW transmit frequency.
> This is only an issue if the station is running "legal limit" power CW on
160m with very large antenna arrays. In the "legal limit" case the CW spur
would still be only on the order of 6 mW (we have measured approximately -53
to -57 dBc), which might be heard by other similar "big gun" stations with
quiet antennas. On 160m SSB or AM it is really a non issue.
While I applaud Flex for finally addressing this issue, there
are a couple of points I'd like to add to the above:
1. I believe the spur is on both sides of the fundamental. At least W5ZN's
definitely was *below* his fundamental when I first noticed it in October 2009.
Joel was calling TX3A up 2.4 kHz and his spur was zero beat with the
DX station.
He was so strong I thought he was accidentally operating out of split mode.
2. A "half dozen reports" is a little misleading in terms of the impact on
others. For someone running legal power to full size antennas, 160 signal
strengths are typically S9+40 (-33 dBm). A 55 dB spur below that would be
~S6 (-88 dBm) on most receivers and about 30-40 dB above the noise
floor. Since
many DX signals on 160 are at or even below the noise floor, a single station
with a spur can cause problems for everyone else on the band. Of course it
doesn't cause a problem for him since he can't hear it while he's transmitting.
If you run full power on Topband, PLEASE make this mod for the sake of
the other hundreds of stations sharing 160 with you.
73, Bill W4ZV
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