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TS-940S TX spur @ +/- 910 KHz.

Shockwave

Sr. Member
Sep 19, 2009
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It would appear that some Kenwood TS-940S radios transmit spurs at 910 KHz. above and below the fundamental frequency. If anyone has a 940 and another HF receiver, I'd like you to run a quick test. Transmit an AM carrier on any HF band and check the second receiver for a spur at +/- 910 KHz. from the frequency on the 940 display.

I've tested 3 radios so far and they all have this problem although, the strength of the spurs varies from one serial number to another. The problem seems to be in the 455 KHz. carrier unit because the second harmonics have not been properly filtered out. In the event anyone else notices the same problem, I'm currently experimenting with a 910 KHz. trap to kill these spurs.
 

The same problem is also spotted at +/- 455 KHz. Indicating that frequency needs more filtering after it goes through the next mixer.
 
Problem solved. Unless you install the optional AM filter in the 8 Mhz IF strip, all of the mixer harmonics are allowed to pass right through the final amp. That fixed the AM spurs but there isn't even an option to install a crystal filter for FM.
 

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