Authored by VE3EFJ
18.10 B LINE TRIVIA
The following appeared on the Drake User Group in July:
Wed Jul 2 18:14:13 1997 ;p.I am not a Drake expert, but in selling, owning and repairing Drake gear since the 1-A, I have had quite a few discussions with Drake service over the past 40 years. Yikes! The transceive system used in the 4A and B lines relies on the relative stability of the carrier oscillators in the receiver and transmitter. Somewhere in the life of the A series, Drake began color coding the carrier oscillator crystals in an attempt to match their frequency vs. temperature characteristics. There were at least three color coded sets of crystals. Red, Blue, and Green. There may have been others, but I have owned all of the above. The serial numbers marked on the rear of the receiver and transmitter each end in a letter, R, B, or G. There is also a color stripe of paint on the crystal under the chassis. For best temperature tracking, you need to have the same "color" crystal in both the receiver and transmitter.
I am not absolutely certain about the following, but to the best of my recollection the Red crystals were a positive TC, (increase in frequency with increase in temperature,) the Blue were approximately zero TC, and the Green were negative TC. I think this information came from Drake some years ago. IF this is true, the worst "mixed" case would be a Red/Green pair, with a Red/Blue or Green/Blue better. Obviously, a matched pair is the optimum, but we don't always have that choice these days. Many years ago, when I first ran into this situation, I was able to exchange a crystal for the receiver in my pair with Drake. I had a Blue/Green set, and exchanged the Green for a Blue at no charge with Drake. SO.... Don't rely on the letter on the serial number. You may get the receiver I modified, or one of the many others that were probably similarly done. Look at the color stripe on the crystal to be sure.
Maybe we could start a "color exchange" via the Drake list !!
The C-Line of course eliminated this problem by patching the two oscillators together, enabling a sort of phase lock between them.
Hope this helps.
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