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To All from PA0SE
A simple system combining the
flexibility of a VFO with the stability of a quartz crystal is a V FO + "Huff
and Puff" frequency stabiliser. This device frequency-locks the VFO to the
nearest one of a series of frequencies that increase in steps of for instance
32Hz and are derived from a crystal.
Take for instance a VFO in the 8MHz range and a stabiliser with
32Hz raster. When divided by 64 down to 136kHz the frequency steps become 0.5Hz.
After manually tuning the VFO the frequency creeps towards the nearest
raster point which is never more than 0.25Hz away and it stays
there.
When a crystal at room temperature is not good enough a TCXO could
be used.
The "Huff and Puff" system was designed by the late Klaas
Spaargaren, PA0KSB and described in many articles in among others RadCom
and Ham Radio. Also in my copy of the fifth edition of Pat
Hawkers Amateur Radio Techniques and possibly in later editions as
well.
Mike, G3XDV, publications manager of RSGB, can no doubt tell you
more about this.
I use a "Huff and Puff" stabiliser on the VFO of my valved HF-band
transmitter and it functions exactly as expected. I would certainly add one to
the 8MHz VFO of my LF-band transmitter if I were to use QRSS. For normal CW the
VFO in itself is stable enough.
73, Dick, PAoSE
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