The AM Forum

I just won an Eico 722 on ePay -- paid way too much but at least I can add it to my 720.  A friend of mine said his 722 has a lot of drift.  Is this common with 722's?  If so, any suggestions?  I had one years ago and didn't notice a problem on CW.  I'm trying to head off what I've heard when mid state stations heterodyne against ongoing QSO's here in the NE and they start off really high like 1 KC and drop down to zero at the beginning of every transmission

Al

Hi Al..jeez you woulda thunk someone could answer that..not sure i can buuuttt..there is an article/posting on E-ham..at the Elmers section under Eico 722 vfo..looks like possibly the same questions or near to what you're asking..2 pages of answers so maybe that will give you a clue..i wish to God i could put in a linky but my extreme limited knowledge of putors won't allow for that..Good luck Al..my 3885 xtal is on it's way!    73 de DAVE

Thanks for the tip Dave -- I'll check it out.  My friend Paul WB2SKC at work who also owns a 722 has a few ideas. If I come up with something I'll post it here.  One thing that has to be done is to see if it is purely a thermal problem -- ie: if it goes and goes in one direction and never stops (maybe slows down) then maybe the NPO caps are either the wrong value or  not working.  If it goes up and down, maybe the voltage regular tube on the screen of the osc might be suspect.  Maybe even a zener diode could be used there to stiffen up the supply.

It has the potential of being a nice detective effort.  When I get mine I'll start messing around with it and see what gives.  Yet another problem is if it drifts going from Tx to Rx each time -- that might be something heating up when the cathode of the osc is grounded for Tx.  Guess it means stay tuned.  Tim HLR noticed some drift in his 722 too

Al