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October 8th 03, 01:40 PM

(John Sandin) wrote in message ...
Regarding the 3-watt transmitter I'm building (and having trouble
with), here's an update.
....

john,
a receiver will probably report all the harmonics of the crystal. so
that is not really a big deal. almost all the harmonics will also
sound pretty powerful and equal to each other in the HF receiver
because the recevier's AGC will boost the lowering outputs to a higher
level.
the output at 3.5mhz can be easily explained by a receiver shielding
deficiency. what i would really suggest to you is to TAKE CHARGE. i
mean, figure out exactly what is going and how.
do you have access to an oscilloscope? a single oscilloscope trace is
really worth a thousand blind trails. failing which,
i suggest that you should first make yourself some test instruments. i
would highly recommend a wavemeter. it requires about 5 components (a
couple more if you want to build a GDO-cum-wavemeter). A single coil
should cover most of the HF band of interest to you. then ...
rebuild the transmitter from scratch, keep everything at 50 ohms
impedance. refer to EMRFD for guidlines. then ...
don't push too much gain in each stage. It is actually easier to debug
and build a transmitter with more stages having lower gain than trying
to push maximum out of fewer components. finally ...
shoot for about 7 watts of output. An 80 cent IRF510 should easily
give you that much. use the wavemeter and the a power meter to measure
the harmonic outputs. But frankly even if you are pushing out 50% of
the energy in fundamentals, then political correctness aside, you
should be able to make contacts. QRP of single watters are best left
to old war horse like W7EL. it is tough for a novice to get through on
a single watt being rock-bound.
i would also suggest that you hook up with a ham down the block to be
able to monitor your signal. then another across the city ... then
another across the state...
- farhan