Robb,
I have worked on a DX2547 that belonged to a friend and I reduced the frequency drift by 7-10x. It is a very long story but I recognize exactly where in the process you are because I was there myself. The radios frequency is basically temperature dependent, to put it another way. I didn't know what all the talk was over the years on the internet about "drift" since I never owned a Galaxy, and the SSB rig I've used the most over the last 21 years is a Cobra 146 (if it drifts, I can't tell whatsoever--clarifier never ever moves). Anyway, after experiments and measurements it was obvious: ambient temp up=frequency down. I went through many drawing board ideas and thoughts but the answer was in my 1995 Handbook. Also, you'll see it in different web pages usually by hams trying to stabilize an old rig or some homebrew vfo they built. Google: "A Look at VFO Drift in the MFJ QRP-Cub." Also have a look at WA0ITP's book "Crystal Sets to Sideband" chapter 10, which is online in .pdf at the qrparci.org website.
In a nutshell, what I found was that the drift is most likely being caused by a change in permeability of the slugs in the tuning coils. This was found experimentally after reading of the possibility. At any rate, the solution is far more important than the cause of the problem. Galaxy, IMO, put SOME temp compensation in the radio with the UJ caps but not enough. Why did they stop where they did? Because: 1.the first thing everyone does when they open the box is unlock the clarifier. 2.charlie only requires .002% freq. accuracy (that's 540Hz at 27MHz, yuk!). 3. you never get more in a cb than absolutely necessary, and that's industry wide historical practice. Therefore, I INCREASED the compensation by replacing caps that drifted more than the uj's in order to counteract the inherent drift in the radio. It took a very long time to arrive here but: I replaced C130 with a 22pf P3K(n1500) and replaced C281 with 3x 33pf caps: 1@ uj (n750) and 2 @ R3L (n2200). That last one gave a "custom" TC and they were installed in the original location, plus in the unused j28 & j29 positions. The drift went from approx. 400-450Hz between 65-90F down to approx. 40Hz over that temp range. The owner finally got it back and was tickled to death over it. The caps came from Mouser, about $2 actually. I never got around to writing up what I did, so when I saw your posts (and heard you on the radio discussing it!) I wanted to share it with you. There's a bit more so email me. Out of time for now. 73 and good luck.
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