what makes radios drift from the proper tuning?

[micky]

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.

[Mike]

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.

>

[trader_4]

Usually the tuning issue is mostly with weaker stations. If the issue is just using it as a source to make it look like someone is home, unless the radio is a real POS, you;d think that you could tune it to a strong local station and it would work. I certainly had all kinds of radios over the years that stayed tuned to all kinds of stations AM and FM without a problem. Micky is in MD too, right? Should be plenty of local, strong stations.

[micky]

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.

[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.

[Rod Speed]

micky [e-mail] 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.

[Mike]

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.

[Clare Snyder]

Likerly a resistor or capacitor in the tuning tank circuit or PLL is temperature sensitive causing the drift

[rbowman]

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

[Ralph Mowery]

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.

[micky]

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.

[Fox's Mercantile]

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

[Rod Speed]

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.

[devnull]

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

[makolber]

To OP

find an FM radio with an AFC. Tune it to a strong station. The AFC should keep it tuned in good enough to make sound.

or just leave it on 24/7 when you are not home

m

[micky]

Good point. But the 3 I have do. I'm not buying another unless I was sure it would get 88.5 and I've tried testing it in the store. Might work there but not when I get home.

Very interesting.

Very interesting.

I may give it a party when it turns 100.

[Mark Lloyd]

[[snip]

I also find that "power amnesia" to be an annoyance. For most of the settings, modern devices use permanent memory. Often, they exclude the "power' switch.

BTW, For TVs, I notice that many smaller ones will remember, and can be used with a timer. Bigger TVs are power amnesiacs.

[Mark Lloyd]

On 2/19/19 8:02 PM, Rod Speed wrote: [snip]

If it doesn't come on after a power interruption, that sounds like a defect (unless this was an OPTION you set). I wish they'd put that information on the box and in ads.

BTW, another piece of useful (but often missing) information is latency of an internet connection. This is often more important than speed.

[Mark Lloyd]

[snip]

I have found this to be true with larger TVs, but not with smaller ones (the largest I have without the problem is 22-inch). However, they don't put this on the box and any salespeople will probably NOT be able to help.

Possibly a very expensive TV might have an option for this.

[Mark Lloyd]

[snip]

Having a momentary switch is not the problem, it's that without power it forgets the setting of that electronic switch.

[snip]