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The first design for the Huff & Puff stabiliser was published in 1973 by the late Klaas Spaargaren, PA0KSB. This was what I call a 'crystal clock' or 'type 1' stabiliser.
In 1996 Klaas published his VFO derived clock ('type 2') version. The type 2 has a considerably stronger lock at VFO frequencies below about 40MHz, though it suffers from the disadvantage that the step height is not independent of VFO frequency.
The third main development was in 1998 when QEX magazine published my 'Fast Huff & Puff' stabiliser design (thanks to Klaas and to Pat Hawker, who first published the circuit and an outline of its operation in 'Technical Topics', for their encouragement).
The 'Fast' design was derived from a close analysis of Klaas' earlier models.
The Fast-mode Huff & Puff stabiliser extracts information from the D-Type output by XORing a previous output with the current output.
The 'fast' architecture can be applied to either type of stabiliser and can greatly improve lock strength.
If your Huff & Puff doesn't stabilise your VFO immediately on switch-on, or if it ever needs to be reset - then replace it with a fast Huff and Puff. It is very simple to modify an existing 'old' type H&P to the fast configuration. You just have to add a shift register, an XOR gate, and increase the clock frequency.
How does the Fast Huff and Puff stabiliser work?
The Fast-mode Huff & Puff is quite simple, actually simpler to construct than previous versions.
As usual with all H&Ps, the digital mixer (D-type gate) provides a squarewave whose frequency is an indication of "where you are" within a particular "lock".
The output of the digital mixer is "counted" for a fixed length of time ("counted" in the sense that only the first and last bits of the count are stored and used).
The first and last bits of the count are compared by an XOR gate.
If the first and last bits are the same the vfo frequency is regarded as being in "region 1", and the VFO is sent up in frequency.
If the first and last bits are different the vfo frequency is regarded as being in "region 2" and is sent down in frequency.
This results in the vfo hovering around a particular vfo frequency.
To improve performance, you can, if you wish, have several (or many!) counts are in process at the same time.
This contrasts with earlier H&P designs in which you were limited to having a new count starting only on the completion of the previous count, and is the origin of the descriptive term "fast".
Having several counts going on at the same time is achieved by storing the first bit of each count in a memory (typically in a shift register) until the the final bit for that count is available.
DOWNLOADS
If any of these downloads don't install or don't work then please let me know. Hit "E-Mail enquiries' above and send me a mail.
Any other comments welcome.
1) Fast Huff & Puff simulator program
Download Fast Huff & Puff simulator program (1.5Mb)
Set your own parameters and watch a simulation of the fast Huff & Puff in action
Notes:
The program is a tidied-up version of the software I used to develop the fast H&P. Sorry, no 'Help' file is included as yet.
Besides being interesting to watch, the program will tell you the maximum drift a stabiliser with given parameters can handle so you can optimise the stabiliser parameters.
This version (13 March 2009) uses better graphics (gdi+) compared to the previous version (gdi), and has some errors corrected
Please let me know if the new graphics doesn't work for you!
This version can be relied on to get the green lines showing the step boundaries in the right places.
It is also better at wider step H&Ps.
If you want to use it but already have the previous version installed, then simply install over the previous version.
When the install program asks if you wish to abort the install, just click "No" and then when it asks "Are you sure?" click"Yes".
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2) Visual Aid 1
Download Fast Huff & Puff visual aid 1 (1.5Mb)
Shows waveforms at outputs of D-Type latch, shift register and XOR gate for variable VFO frequency and number of shift register stages.
3) Visual Aid 2
Download Fast Huff & Puff visual aid 2 (1.5Mb)
This little program (Visual Aid 2) is meant as an aid to understanding the way that the initial and final bits of the count can be used to stabilise the vfo.
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