The Huff-Puff technique is a method of stabilising the frequency of ordinary L-C VFO's. Most VFO constructors will have experienced great difficulty obtaining a stable frequency, at least without careful attention to temperature compensated capacitors etc. The Huff-Puff approach was pioneered by the late Klaas Spaargaren PA0KSB, and results in a rock-stable VFO effectively locked to a crystal-derived reference frequency. Over the years several magasine articles have appeared describing both the original circuit and subsequent enhancements. Some of the articles are reproduced here, along with details of my own Huff-Puff projects, and an article sent to me by Olivier F5LVG about his Simple Frequency Stabiliser.

Huff & Puff Reference Library A collection of articles for download in Adobe Acrobat (.pdf) document format, containing every Huff Puff article I have been able to find, dating back to the first mention of PA0KSB's new idea in RadCom July 1973. With thanks to the Radio Society of Great Britain (RSGB) for permission to reproduce articles from Radcom, the society's monthly journal; and to the American Radio Relay League (ARRL) for permission to reproduce articles from QEX, the Forum for Communications Experimenters. Read more...

Magnetically-Coupled fast Huff & Puff stabiliser I built this stabiliser mainly based on the circuit of Chas Fletcher G3DXZ, in RadCom's TT column, September 2000, but with a few changes. In particular, my circuit uses "Magnetic coupling". I decided to use this method after correspondence with David White WN5Y, who had the idea of applying it to Huff & Puff stabilisers and whose work inspired my mine... Read more...

Minimalist 1, 2 and 3-chip VFO + Stabiliser designs A selection of minimalist Huff & Puff projects: 2-chip combined VFO + Stabiliser; 3-chip combined VFO + Stabiliser + Frequency counter; and amazingly, a 1-chip Huff & Puff stabiliser! These designs represent such a massive simplification compared to existing designs that I hope they will be more accessible to a larger number of builders...Read more...

All-valve Huff & Puff stabiliser (under construction) I am attempting to build an all-valve VFO, Huff & Puff Stabiliser and Frequency counter. The timebase will be an 8KHz crystal, followed by three phantastron divider stages to get a 10Hz timebase. The frequency counter will consist of three stages of trochotron decade division and three dekatron dividers. The outputs will be latched by an array of cold cathode discharge tubes and displayed on nixie tubes. Read more...

Partial construction of Fifth-Method stabiliser A long time ago I started making the "Fifth-Method Stabilised Oscillator" as described by the original Huff Puff man himself, Klaas Spaargaren PA0KSB in RadCom March 1991 (see below). My efforts are pictured here with parts of the circuit diagram... Read more...

A Simple Frequency Stabiliser, by Olivier F5LVG Olivier Ernst, F5LVG sent me the following article about his simple frequency stabiliser, built according to the original Huff Puff theory (as opposed to the more complex "Fast" method). He used ordinary diodes as varicap diodes, a zener for the main VFO tuning and a red LED for the stabiliser correction... Read more...

Huff & Puff Stabiliser Frequency Simulator I wrote a rather basic Java simulator for Huff & Puff Stabilisers in January 2001. The simulator is very far from perfect but it is capable nonetheless of revealing some interesting insights. I also ran an experiment, using the simulator, to investigate the effect of mark/space ratios other than 50%. Read more...

Huff & Puff Stabiliser Ripple Simulator In June 2000 I wrote a simulator in Visual Basic to investigate the effects of the number of shift register delay stages in "fast" stabiliser designs, on the maximum stabiliseable drift and resulting output frequency ripple. This simulator can also examine the "classic" stabiliser method by setting it to a single delay stage. The results are revealing! Read more...

"Fast" Huff & Puff calculator by John VK6JY In June 2000 I wrote a simulator in Visual Basic to investigate the effects of the number of shift register delay stages in "fast" stabiliser designs, on the maximum stabiliseable drift and resulting output frequency ripple. This simulator can also examine the "classic" stabiliser method by setting it to a single delay stage. The results are revealing! Read more...

Huff & Puff Stabilisers on the Web

huffpuff/fast.html Magnetically-Coupled fast Huff & Puff stabiliser by Hans Summers, G0UPL
http://oernst.f5lvg.free.fr/oscil/stab/stab.html A Simple Frequency Stabiliser by Olivier Ernst, F5LVG
http://www.pan-tex.net/usr/r/receivers/elrstbzr.htm A unique magnetically-coupled stabiliser by David White, WN5Y
http://homepage.tinet.ie/~ei9gq/stab.html Eamon Skelton EI9GQ's PIC-controlled stabiliser
http://www.qsl.net/it9xxs/frmain.htm Another stabiliser, by Giovanni Mazzola, IT9XXS
http://members.ziggo.nl/cmulder/ksbstabi.htm Carel Mulder PA0CMU's stabiliser design, from PA0KSB's improved version, 1996
http://www.qsl.net/om3cph/counter/lcd/contribs/pic_flck.htm Osmo OH6CJ's PIC Frequency Counter with Frequency Lock function
http://home.kpn.nl/brink120/huf2.htm Ron PA2RF's "Fast" type minimalist Huff Puff stabiliser
http://www.cumbriadesigns.co.uk/x-lock.htm X-lock stabiliser kit by Cumbria Designs
http://www.aholme.co.uk/Stab/Stab.htm CPLD (programmable logic) "Fast" stabiliser design by Andrew Holme