General Coverage

[Bob Miller-6]

Hello,

I'm the builder of #4175 and have a question concerning the lower end of the spectrum.  I was attempting to listen for the VFO of the 2N22-40+ that I'm building at 2085-2185mhz.  I don't hear the VFO nor do I hear anything else down there.  I tuned into the AM broadcast band and couldn't hear a single station.  Is this normal for the K2 or do I have a problem?

Thanks,

Bob
WB6KWT
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[Don Wilhelm-2]

Bob,

It is not abnormal - the amount of out-of-hamband range may be slightly
different from one K2 to another.

You may be running out of VFO tuning even though the numbers change.  If you
want to verify, check the voltage at the left end of R30 on the RF board.
If it is less than 0.5 volts or much over 7.5 you have run out of range and
it will tune no further.

73,
Don W3FPR

----- Original Message -----

I'm the builder of #4175 and have a question concerning the lower end of the
spectrum.  I was attempting to listen for the VFO of the 2N22-40+ that I'm
building at 2085-2185mhz.  I don't hear the VFO nor do I hear anything else
down there.  I tuned into the AM broadcast band and couldn't hear a single
station.  Is this normal for the K2 or do I have a problem?



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[Ron D'Eau Claire-2]

That's normal because of the way the dial works.

In normal operation the dial readout is not directly related to the VFO
frequency. It's what the logic *assumes* would be the frequency, assuming
the local oscillator can tune to it. There's no direct measurement of the
local oscillator. The local oscillator frequency is only measured in CAL
PLL.

When you run the CAL PLL, you look up the internal counter to the L.O.
output and the K2 logic  measures the frequency of the L.O. at various
tuning voltage levels. It then creates a "table" of values that says "If a
tuning voltage of 'x' volts is applied to the L.O. tuning, then the receiver
ought to be tuned to 'y' kHz."  And it's that 'y' kHz frequency that is
shown on your dial in normal operation.

Think of it as an old analog dial with numbers written on the face so you
can see what frequency it's tuned to by seeing where the pointer is on the
dial. Running CAL PLL tunes the K2 across the tuning range and "writes"
numbers on the dial at intervals so you can see what frequency you are tuned
into when you are operating.

Unlike the old analog dial, there's no "hard stop" at each end of the range
saying that you can't go farther. It'll just let you keep tuning and tuning
and tuning.

So, if you tune outside the L.O. range, the numbers will continue to change
on the dial, even though the local oscillator can't be tuned to that
frequency.

Ron AC7AC


----- Original Message -----

I'm the builder of #4175 and have a question concerning the lower end of the
spectrum.  I was attempting to listen for the VFO of the 2N22-40+ that I'm
building at 2085-2185mhz.  I don't hear the VFO nor do I hear anything else
down there.  I tuned into the AM broadcast band and couldn't hear a single
station.  Is this normal for the K2 or do I have a problem?


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