An amazing observation was made here this morning!!!! I tried a more traditional H&P idea but retained my 24 MHz oscillator and reduced the chips down to the 74HC74 and the 74HC4060 with a 1.7 to 2.5 MHz VFO tuned circuit wired to pins 10 and 11 on the 74HC4060. So the VFO was built up into the chip with no problem really.
I modified the entire view of how these chips are used in the files on the Internet. Maybe others have this scheme working; I don't know but it is sort of an advanced scheme which I will get the circuit diagram of to you all soon. Now its really simple, just a few extra pin connections between the two chips and thats all. I used two 1N4007 diodes for Varicaps to a 10K resistor of the voltage control loop, to two 1000uF electrolytic and then a 1k resistor to pin 5 of the 74HC74 and there is another coming of the pair of capacitors of 2k to pin 10 of the 74HC74. I use the two halves of the 74HC74 for dual comparison with a time base signal and the divide by 16 bit signal from the 74HC4060 that is compared; while I use the lesser bit of pin 1 of the 74HC4060 to strobe the memory of the 1st halve of the 74HC74. I figured also that mixing this lesser weight bit into the scheme would give me perhaps a source to beat or heterodyne with the mix to obtain smaller increments in tuning for small locks. And the other halve processes the signal more to give me a sort of push and pull on the diodes (hence two control signals to the paralleled up diodes). This makes the VFO more stable and makes it lock up every few hertz. I can't believe it!!!! It only makes a maximum correction of about 5 Hz per second at most and always comes back to the center frequency. Steps can range from 1 to 3 to 5 hertz at any given second. I suspect that the phase noise is truly small. A more stable VFO made of better parts than I have laid out on the bench in the open with the Variable capacitor off to the side all loose and unshielded from electrical fields in the room and heat and all needs to be eliminated for a better device but at present the model in its un ideal ugly form is performing way beyond what it seemed it would at first. I happened then on the idea of a mixing scheme to use more of the inputs to the 74HC74 and more of the available outputs of the 74HC4060 for more comparison to over come my high time base reference which at its fundamental does not give allot of small spaced frequency locks. The scheme now can tune in increments smaller than I was achieving using the standard circuits in the files with the 24MHz clock. And it releases itself easily which I think is due to the strobe cycles, quickly upsetting and releasing the lock when it is tuned away from center frequency. But small increments are the amazing thing. The circuit diagram will be sent out to Arv as quick as I can draw it up and then we'll get it in the files. I am now shocked and I do believe now as I once suspected that this can be used with SDR receivers. I just had to learn about it and see it for myself to know. And how to achieve it was beyond my understanding but now I have done it and seen the truth of it. I realize you can not have capacitors on the voltage line to the diode when designing them for locking up. You have to tinker with them till the H&P pulls the VFO like it should to over come the VFO drift and then when the VFO is following or tracking the H&P you can later add the caps to slow down the bounce around and jitter. I did not think I was going to use two 1000uF caps but thats how it came out to be in the end. Two 1N4007 diodes seem to slow the whole motion down more as I began to study how this thing was rolling around the band seeking a place to lock. I just noticed that it skipped a step and stopped about 6 Hz up and stayed there. (I'll check this to see if the locks are every 6 Hz?) I noticed also the things that cause it to skip steps are power line fluctuations and transients such as when an air conditioner compressor comes on. Power regulation and filtering as well as proper shielding then seem to be the answer. It appears then that things switching on and off locally can be the source of loosing a step in the oscillator tracking. ka9rza _____________________________________________________________________ PrivatePhone - FREE telephone number & voicemail. A number so private, you can make it public. http://www.privatephone.com 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/
