Re: BFO oscillator level

[Marteinn Sverrisson]

Thanks Don and Jack for the info,

Don,
I did ground Xtals X3 and X4 at the base (they where grounded on the top),
flush cut all leads on the mixer and if amp circuits. No change.

Both LSB and USB lit 1 led when I turn the K2 on, and then after abt 5
min, then on USB the second led will turn on, but on LSB no change.
Maybe this indicates a bad IC, either the mixer or if amp?

Jack,
I guess that not all K2 are born equal, as you mention the BFO
leakage varying up to 10dB, between rigs. Probably some 602 and 1350 have
better (higher) revese isolation than others.

This BFO leakage is not a big issue for me, just a little annoying.

thanks and 73, Matti
--
   Marteinn Sverrisson    TF3MA
          Langitangi 2    Internet: tf3ma [at] raunvis [dot] hi [dot] is
        270 Mosfellsbær   http://www.raunvis.hi.is/~tf3ma
               Iceland
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[Don Wilhelm-3]

Matti,

I do not believe there is any indication of a bad IC.  The display is
digital, and if the level is somewhere above one bar, but not quite 2 bars,
there is an indecision point.

I would expect all the indications point to BFO leakage.  As Jack pointed
out, all K2s have it, and some at a higher level than others.  Evidently
your leakage is greatest into your KSB2 board, and on USB, there may be a
little bit more BFO voltage, hence more leakage.  While you could take steps
to equalize the USB and LSB BFO levels, is there really any need to do that?
Since normal band noise is normally greater than the leakage signal, your
best solution may be to ignore it and set the S-LO menu parameter so no bars
occur in USB, then set S-HI to illuminate the last bar.  If you have an XG1
or XG2 (or other source of a 50 uV signal), you can check the S-9 level and
refine the S HI parameter if required.

The BFO implementation in the K2 is a VXO, and the operating levels can
change as the frequency of the crystals is pulled.  If you want to
experiment, I would suggest you obtain several sets of BFO crystals and
check the operation of each set to see if the levels can be equalized.

The other factor is the BFO alignment for the filter that you are using.  If
he USB filter is aligned so there is greater low frequency audio content
than the LSB filter, you would expect more BO feedthrough because the BFO is
aligned closer to the IF filter center frequency.  Set the filters/BFOs for
an equal response on LSB and USB before attempting to adjust the S-meter
parameters.

73,
Don W3FPR

> -----Original Message-----
>
> Thanks Don and Jack for the info,
>
> Don,
> I did ground Xtals X3 and X4 at the base (they where grounded on the top),
> flush cut all leads on the mixer and if amp circuits. No change.
>
> Both LSB and USB lit 1 led when I turn the K2 on, and then after abt 5
> min, then on USB the second led will turn on, but on LSB no change.
> Maybe this indicates a bad IC, either the mixer or if amp?
>
> Jack,
> I guess that not all K2 are born equal, as you mention the BFO
> leakage varying up to 10dB, between rigs. Probably some 602 and 1350 have
> better (higher) revese isolation than others.
>
> This BFO leakage is not a big issue for me, just a little annoying.
>
> thanks and 73, Matti
> --
>    Marteinn Sverrisson    TF3MA
>           Langitangi 2    Internet: tf3ma [at] raunvis [dot] hi [dot] is
>         270 Mosfellsbær   http://www.raunvis.hi.is/~tf3ma
>                Iceland
>

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