I WAS TOLD THAT THIS FM TUNER HOOKED UP TO A OLD AM RADIO WILL TAKE UP TO 10 MIMUETS TO WARM-UP AND THERE'S DRIFTING. IM TALKING ABOUT AN PILOT FM T601 TUNER.
I HAVE AN OLD DEWALD AM/FM AND I DON'T NOTICE THAT.

Lots of people make lots of radical claims about tube radios, like that they're inferior, the tubes burn out a lot, and that they need like 5 or 10 minutes to warm up. A typical radio takes about 15 seconds to warm up. Some with 2.5 volt tubes can start operating in as little as 6 seconds. Most AC radios take about 10 seconds, possibly a little longer. Most AC/DC radios take about 15 to 20 seconds, possibly longer. Battery radios often take less than a second to start operating, when run on batteries. 6 volt vibrator sets are the exception, and should take about the same time as any AC set.

As far as stability is concerned, you can expect your most stable operation after about 10 minutes. This is especially critical with FM, but also holds true with AM. It is somewhat annoying that the push buttons on my auto radio don't tune in the stations properly on really hot or really cold days. I see to it that the push buttons are set only after about 10 minutes of operation, and that really doesn't solve anything anyway. I have to fine tune each station when I tune it in with a push button just about every time, so I just expect to do so. Some of the better radios do not drift much. My auto radio is a Zenith, so I can't say that Zenith always makes the most stable radios, though this radio also operates in the most severe conditions. I once owned a 1951 Zenith consol with FM. The AM was almost as clear as the FM, and the FM was extremely stable. It had no automatic frequency control selection, and the stations never drifted. The best components are selected to off-set one another, or to not drift much in the first place. My DeWald BT-100 television (RCA 630TS chassis) has a special condenser in the horizontal oscillator that looks like any other condenser. However, it is actually two units in one. There is a larger unit and a smaller unit. They parallel eachother, and the smaller unit is selected to drift in exactly the opposite direction of the larger unit so that the horizontal oscillator is fairly stable. The rating of the condenser is actually .015 MFD (or some odd number like that...I forgot exactly.....I think it actually had 4 digits to the right of the decimal). RCA claims that you need to readjust the horizontal hold over and over again as the set warms up if this condenser is replaced with a conventional one. I find that I have to readjust the horizontal hold once or twice even with this condenser, but I assume that it helps somewhat. I cannot expect to have a perfectly steady and centered picture until after at least 10 minutes of set operation. Also, without an automatic frequency control, I can expect to readjust the fine tuning control several times during the set's warm-up.

Thomas