Bernd Maestling wrote:
> ok, so far so good.
> The RX-module won't work. The PLL don't lock, L1 voltage is low
> (0,16V) and on TP12 I have about 433MHz (also near the VCO).
> The TCXO is working ok.
>
> 73
> Bernd
> DM5BM
To receive at 431 the VCO will need to be at 431MHz-45MHz(1st IF) or
386MHz. It was built to go from 395MHz to 440MHz. This may be below what
the VCO will tune without adding some capacitance. First try adjusting
the trimmer capacitor to the lowest frequency you can. If this is above
386MHz, you will need the extra capacitance to get the VCO into the
correct range. Look in your manual near the back at the parts list for
the VCO for the differences between range C and range D. There are a few
capacitors and one resistor that are slightly larger on the D range. You
can either parallel some small chip caps or replace the current ones
with the new values. The coaxial resonator is also longer, but as you
are only going down to 431 the current one may be long enough.
Try adding 1.5 pF across C7 on the RX VCO.
Once the VCO is going, you may find the helicals need to be lengthened also.
Ed Yoho
WA6RQD
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