Ron Brink PA2RF has posted his circuit of a H&P controlled 50 MHz VFO he built where he divides down the 50 MHz VFO for sampling by a 74HCT4017 divider and then follows that with a 74HC4060 and then a 74HC164 shift register to complete his HUff & PUFF circuit.
http://groups.yahoo.com/group/HuffPuffVFO/files/PA2RF/fast6m.JPG I will do a follow up on this circuit and try it out myself. My aim and interest is to go ahead and make use of the divided down outputs from the ICs, perhaps down in the 2.5 to 5 Mhz range outputs, where the frequency will be extremely stable by reason of numerous divisions and have some considerable incremental tuning. If the H&P circuit is doing as it should; to control lock positions to +/- 1 Hz then the stability after division will be less than 1 Hz and in non lock positions the output may not change then but by 2 or 3 Hz since there is some control of the random VFO motion exhibited between lock positions. So this then is the ideal scenario for extreme VFO control that can meet stringent stablilty and phase noise as well as jitter requirements. "...The VFO circuit was originally used for a free radio transmitter (88..108 MHz) so getting the frequency back to about 50 MHz wasn't that difficult. The schematic of this VFO could be found on http://www.dsv.nl/~fantasy/schema.htm but I found that this is a dead url now........ ...To make the vfo more or less independent from various output loads and raise the output level I added 2 times a BF494 feeding a 74HCT4017 divider (set to divide by 9, this worked the best for me). Then the signal is fed to the fast H&P circuit described by Miguel PY2OHH (so divider 74HC4040->shift register 74HC164->integrator with 2x 200uF -> 100k -> VFO)......" Ron PA2RF http://home.versatel.nl/laar60 I will get a copy of Ron's circuit diagram for us. But I must seriously redraw it first! After I decipher his hand drawings. Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
