Hello Dick,
I get
+17dBm out on 137kHz now.
There are a lot of harmonics in the
(unfiltered) output; especially the 3f, 5f, 7f etc.
So, at least I am producing a signal on 137kHz
(and maaaaaaaaaaaany other freqs) now.
At this point I am not sure what to
do.....filtering or not??
I suppose I get these harmonics again in later
(driver) stages so, maybe better to
do it at the
end.......... No need to filter the drive signal if
you are using a class-D amplifier (in fact it is best to drive a class-D
amplifier with a quare wave).
A 2 or 3 stage low-pass filter at the PA output will get rid of the
harmonics, a high-Q antenna will even improve that.
How to
key is the next question.
I want to leave the VFO on all the time for
better stability.
The 4060 will be switched off in RX situation,
to aviod having a signal on 137kHz,
and in my receiver blocking the
RX..........
I did some tests with the keying circuit used
by OM2TW and DF3LP/DJ1ZB in their designs
using 2 stages with BC549, from which the first
one is switched in its emitter.
However, this did not work fine.
I was able to key, but the output level was
much lower then it's input, and the level of
harmonics etc where worse, compaired to the
input signal of the circuit. Best thing to do is to
key the PA somewhere. Dave (G3YXM) has a nice design that provides really
"soft keying". I do key a G3YXM-like PA at the input and have
had any complaints about key clicks so far.
73, Rik ON7YD
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