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Registered Member #3925
Joined: Fri Jun 03 2011, 10:50AM
Location:
Posts: 121
hi,
is it possible to tune the frequency of this? the variable cap only seems to vary the output power, not the frequency... im curious as to how one can reply to a cq call when ye cant tune the transmitter xD
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
I think Steve meant that the crystal frequency can only be pulled to a small degree by means of a variable trimmer capacitor in series with the crystal. At 3.5MHz, you may be able to pull the frequency upwards by a few kHz, which can be useful to avoid interference by strong stations. By contrast, adding a parallel capacitor will pull down the frequency by a small amount.
Attempts to pull the crystal frequency by more than a few kHz will usually result in instability.
In solid-state transmitters, crystal pulling is usually achieved by varactors.
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