what makes radios drift from the proper tuning?

what makes radios drift from the proper tuning?

I have radios that I tune and after they play a while the tuning needs to be adjusted.

This is common, I assume.

What is happening? Does the vibration make the variable condenser shift a little bit? Or do the parts get warm and some value changes?

Is this more common in AM than FM? or vice versa? FM has AFC but iirc AM doesn't have that.

I am going away for a while and I want to use timers to turn on lights and also a radio, but some radios get so far out of tune, even when I don't touch them, that almost nothing comes out, and I'd like the radio to continue to play the station clearly.

I can't use radios with electronic tuning because with a timer that turns the power off and on, when it comes on, the radio doesn't start until someone pushes a button.

Reply to
micky
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Yep, that's a problem. But you can't do much about it.

You could leave the electronic tuning radio on all the time and use an external speaker switched by the timer.

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Reply to
Mike

** Its far more common with FM than AM and with tube sets compared to transistor.

It results from the local oscillator ( LO ) changing frequency with rising temperature after the set is switched on and begins to warm internally.

The culprits are the tubes or transistors plus low value capacitors used in the LO circuit.

IME transistor AM radios barely drift at all unless part of a receiver ( tuner - amp) that that heats significantly.

.... Phil

Reply to
Phil Allison

So are you saying that AM is worse than FM, because AM has no AFC?

Or AM and FM are both a problem?

Maybe for next time. I don't have one of those.

Reply to
micky

I didn't pay much attention until just now, but I think the common one was 88.1, which is pretty strong. I'd leave one radio on and even in the length of time it takes to take a bath, 30 minutes, the sound would get gnarled.

On my 250 dollar radio, 88.1 in Baltimore got lower in volume about a year ago, and 88.5 which is all the way in DC is now louder and probably more clear. (But that one has electronic tuning, have to push a button to get sound.)

BUT, none of the radios I actually use except the car radio can get

88.5, because it's all the way in DC. Yet on the good radio it comes in better.

I guess I figure that if it drifts on a somewhat weak station, it will drift on any station. Is that where AFC will make a difference? On FM only but not AM? (and with enough time it will drift so far it won't sound like a radio station.)

Yes, just for making noise it doesn't have to be a station I would actually listen to. It could even play hiphop. it's a pain for testing however, having to listen to some of that.

Reply to
micky

Do you have a TV with cable access ? If so, does the cable service have music only channels ? Our Xfinity/Comcast does.

Have your timer turn the TV on/off. Leave cable box set to music channel.

Reply to
""Retired"

Any or all of the above.

Reply to
Sjouke Burry

micky wrote

The thing that does the tuning moves physically. That's only with the old radios tho, not modern digital ones.

No it isnt.

Shouldn't do unless is much looser than it should be.

Again, it shouldn't happen with a well designed radio.

In theory its more likely with AM.

That's sort of true.

They arent all like that. Just replace the radio with a better analog one.

Reply to
Rod Speed

No, I'm not saying that. I'm saying that, if all the devices you have to make noise are insufficient, you need different devices. Fixing ANY of them is gonna be far more time consuming than obtaining a speaker or mp3 player or a computer that can turn itself on whenever you program it...like all of them do...somehow.

Turn on the mp3 player and let it loop 24/7. The switched lights should be sufficient to fool anybody who'd be fooled by such devices.

Reply to
Mike

How old and crappy are your radios? Have you made it up to a superheterodyne or are you still in the regenerative era?

Reply to
rbowman

Me, I'm still waiting to upgrade to using a stainless steel razor blade for mine...

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Reply to
danny burstein

Usually AM will be worse because there is no AFC. Most FM radios will have AFC.

Just turn the radio on and let it play for half an hour before putting it on a timmer.It may come on off frequency ,but as it warms up it should drift to the station.

Reply to
Ralph Mowery

This is not as bad as some seem to have gleaned. This method will work, I just wanted to shorten the time it would take me to find the right radio, the right AM or FM band, and a a good station

No, I don't.

It doesn't have to be music. Burglars don't know my tastes. It just has to be a radio or tv station.

BTW, I've been on 3 trips in the last 2 years totaling 160 days and no one has bothered my house at all. I just want to keep it that way.

If the timer provides power to the TV, someone has to press the TV's on/off button.

Thanks.

Reply to
micky

Digital radios won't work here. They all afaik have a separate momentary-on on/off switch.

I thought I had at least two radios like this.

It doesn't seem to be loose.

I wasn't there when they designed it. ;-)

That's good to know.

I know some radios have an AFC switch, so you can get weak stations that are close to strong stations, but if there is no AFC switch, I thought all FM radios have AFC anyhow.

BTW. that reminds me of another example of drifting. My Hallicrafters short-wave (plus medium and long wave) radio made in the 30's I got from my cousin around 1958. A couple times I heard TV sound on it, even though TV sound in the 50's and until digital is supposed to be FM and the radio was AM. Nonetheless, I turned on a TV and found the channel it was receiving.

And I had to retune every 5 minutes or so to a constantly higher frequency. Finally after an hour or two, I reached the end of the band. IIRC I switched to the bottom of the next higher band but I couldn't find the same transmission.

Yes, the thing was 30 years old but it was certainly well-designed. I still have the radio and I've only had to replace the AC filter capacitors. Everything else still works, even though it's about 85 years old now.

I've bought 2 or 3 radios in the last couple years, but in order to get

88.5 in DC in the kitchen, without having to turn on the wireless speaker from the computer. (no, for others who suggested the computer, I'm not going to run the computer for 24/7 for 12 weeks when I can just run a radio 3 or 4 hours a day. I've been plugging and unplugging a couple of them making sure which one will stay on the frequency it's set for, but this takes a lot of time and the questions were designed to speed things up.)
Reply to
micky

Hallicrafters radios are notorious for drifting. It's almost a trade mark.

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Reply to
Fox's Mercantile

Not all of them do, most obviously with car radios.

Looks like you have fluked a couple of duds. None of my analog radios do that.

Normally the analog ones do, not needed with digital ones.

Yeah, you can decode FM with an SSB receiver.

Likely it was an intermodulation that you were receiving and the signal it was intermodulating with was what was drifting that dramatically.

Yeah, very decent designs.

Yeah, they do last well.

Reply to
Rod Speed

My 1930s regen doesn't drift after half an hour. But don't look at it sideways.

NT

Reply to
tabbypurr

AM receivers can receive FM due to a phenomenon called slope detection. It's hardly ideal but can be done. If they can tune to the right frequency.

NT

Reply to
tabbypurr

Life is a constant battle of keeping burglars out of my house and democrats out of my paycheck. Democrats suck!

Reply to
devnull

Depending on the vintage of the device:

Heat and vibration are the primary culprits. Followed by temperature differ ences - that is, on a battery set or a low-volt portable tube set, heat fro m the electronics is not a factor. But a 10-degree change in ambient temper ature can cause drift.

Then, of course, it can be changes in the time-of-day and environmental eff ects, local sources of interference and similar. At our summer house, FM is problematic during the day (we are in a valley with at least two mountain ridges between us and the nearest transmitter), but crystal clear at night from several stations. Yes, I know FM is line-of-sight, I am only reporting what is the actual case.

"Modern" Digitally tuned devices should not drift at all. And perhaps you s hould target such devices for your needs while you are away.

Peter Wieck Melrose Park, PA

Reply to
peterwieck33

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