[Yaesu] FT-1000D Intermod

[James M.]

I've discovered something about my so-called "intermod"... One "spur" I
get about 9.4 khz above a strong (S9+30) AM broadcast signal (when on
LSB) seemed to be audible on both sides of the null point, i.e seemed
like I was getting a beat note as I tuned on either side of its freq.  I
then discovered that I could also change the frequency or beat note of
this "spur" by adjusting either the SHIFT or WIDTH control.  Its beat
note would change in about 100 hz steps with the detents on the shift or
width controls.  This spur is apparently some mixing between the strong
signal and the shift/width frequency control inside the radio!!!!  This
only happened when using 2.0 or 2.4 khz filters.  Couldn't hear it using
250 or 500 hz filters.   Any ideas guys?

Jim N4BE


sellington wrote:
> 
> Thanks to all who responded.  Sorry I didn't think to point out that, yes,
> the noise blanker was off.
> 
> I made some more measurements last night, and it looks like the problem
> may be high order spurious responses within the roofing filter passband.
> I applied a single input signal of about 10 mV (-27 dbm), and found some
> spurious responses only about 50 dB down.  Depending on the precise
> frequency, the spurs were 500 to 1000 Hz from the signal.  Their strength
> varies linearly with input, so they're not intermod products.  They tune
> faster than normal, so must be related to VFO harmonics.  In some cases
> they have a strange slow beat note, which could be what sounded like
> intermod.  I don't know the cause yet, but there's something strange
> happening.
> 
> 73,
> 
> Scott  K9MA
> 
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