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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