signal@houxf.UUCP (J.BODDIE) (10/01/84)
Thanks to everyone who responded to my question about VXOs. Here are some results: First, I added a series inductor with the xtal and variable capacitor. This did not help at all. In fact, the FT-243 xtals seemed to be have trouble oscillating at the extreme tuning range (still about 1 KHz). Following a recommendation to try xtals in the HC6/U package, I called JAN Crystals Co. Their "technical person" said that there was no difference in the cut of xtals in either package and could not guarantee that one would work better than the other for this application. I decided to see for myself by ordering two xtals in an HC17/U package (same as HC6/U but with pin dimensions compatible with the F-243 socket). Success! These xtals could be pulled about 4 KHz without a series inductor. I am hopeful that the inductor will extend this somewhat. For your information, my QRP rig is based on a series of articles in 73 Magazine. I would recommend this circuit to anyone interested in building such rigs because it is simple, has fairly high output power (8-10 W), and all of the parts except for xtal and variable capacitor are available from Radio Shack. The inductors are made by removing turns from R.S.10 and 100 uH chokes. The articles are as follows: Feb. 81 - 80 & 40 m VXO transmitter. Feb. 82 - VFO for above. I tried this, but it was chirpy and coupled power supply ripple very well. May 82 - 20 W amplifier. Probably not worth the effort for only 3 dB. Jan. 83 - 20 & 15 m versions. July 81 - Companion receiver. I don't know anything about this. Mar 83 - VERY IMPORTANT. Corrections to procedure for making the inductors from R.S. chokes. Even with the limited tuning (1 KHz) and a dipole, I have worked about 15 states and the U.K. over a 1-2 month period. Thanks again, Jim Boddie NG2J houxf!signal