radio keeps going off station

[henrysgarage]

I have an old dial/ mechanical radio receiver that keeps drifting off station and re-tuning it works for awhile. Hope someone can give some insight into this.

 

[laser3kw]

Tube type or transistor?
possibly thermal drift. A component is getting hot and detuning.
Try gently blowing on it with an air gun (with out tweeking the tuner)and see if it try to comeback.
As they get older the capacitors dry out and then they detune. Replacing the caps is the only cure

 

[redpines]

Aliens

 

[Barnabas]

The variable capacitor that does the tuning may need a little mechanical tightening.

 

[Road Wrench]

The old rigs need to be on long enough to reach a stable tempetature, and the temp in the room should be consistent without drafts near the radio. If you are listening to distant am stations in the evening, the frequency can act like it is drifting off when propagation changes, multipath and phase shift will raise the noise floor and temporarily sound like single side band a few khz off (charlie brown teacher) but will come back on frequency intermittently. If it drifts off and never comes back till you retune it is likely temperature instability at the oscillator. Continual tuning in the same direction should indicate its still warming up, but tuning both directions to regain when it drifts I would think is unstable temperature or unstable values in one or more components.

 

[henrysgarage]

Thanks all, I've ruled out aliens but maybe Russians? Transistor type radio and I keep the garage under 60*. I should take the cover off and see how dirty it is inside.

 

[BD1]

I buy radios at garage sales for a couple of bucks . When they start to screw up I grab another. I always set to my favorite station before buying. Sometimes there is a fine line between stations.

 

[MBfreak]

If it is a tube radio on FM , try replacing the local oscillator tube. With age and heat the intertube capacitances may drift , pulling the mixerfrequency and consequently also the station off setting.
If it is a very early transistor FM radio with germanium semiconductors, there is not much you can do than retune the dial.
If it is a bit more modern ( >1966 around) FM radio the quotient detector is feeding a varicap so that when it starts to drift, the closed loop feedback will pull it back to zero offset in the detector, keeping it on station.
An interested old radio nerd will repair it for you.
Please post a pic of the offender.

Ola

 

[laser3kw]

FM radio the quotient detector is feeding a varicap so that when it starts to drift,

kind of related: On the older Motorola's we found that a "crystal" would form on the plates of the vari caps. We would have to periodically go in as maintenance and rock the screw back and forth to break up the coating. Maybe the OP will find a dirt problem when he opens it up. Squirt the varicaps with some electric contact cleaner just cause.

 

[lilredex]

My garage radio, tucked up in the ceiling, is a seventies solid state Pioneer tuner that often drifts off the station. A ladder fixes that.....I just live with it.

 

[MBfreak]

laser 2 kW
I must have explained myself poorly
the quotient detector is feeding a varicap

The varicap I mean is a hermetically sealed diode, reverse biased. It changes capacitance ( 5-30 pF around) based on the reverse bias voltage.

I believe your input relates to the tuning variable capacitor, one section for RF and one section for oscillator.
If that gums up, for sure the tune will sail away. A busy spider, maybe? The survive in the most unusual places,

Ola

 

[Movover]

Caps most likely, they will degrade and dry out over the years then you have unstable voltages causing the drift. They are one of those things that just goes bad with age.

 

[kbs2244]

Wouldn't just leaving it turned on help?

I keep my shop radio going 24/365.
Not for this reason, but because it keeps the chipmunks out.
It seems the voices and music makes them nervous.

 

[lakelandcat]

check your antenna, anything not digital needs a proper antenna.

 

[laser3kw]

I believe your input relates to the tuning variable capacitor, one section for RF and one section for oscillator.

You are correct.
I did confuse "varicap" with "variable tuning cap"
Have to kind of watch terms. Many of us call things the way we are taught. When we here something similar we relate it to what we know.
As far as the "crystal" - it was a real thing (not a spider). Imagine a calcium / lime looking formation. Why it grew where it did? I never heard an explanation ( from the factory)

 

[DFB]

My garage radio, tucked up in the ceiling, is a seventies solid state Pioneer tuner that often drifts off the station. A ladder fixes that.....I just live with it.

Gawd I remember having a Scott tuner as part of my first system back in the late 70's...that thing couldn't hold a station for 20 minutes without drift

 

[dogdog]

The variable capacitor that does the tuning may need a little mechanical tightening.

^^^
I would check this.....

 

[myredracer]

The variable capacitor that does the tuning may need a little mechanical tightening.

And/or it may be clogged with dust and need blowing out. May not have one tho. Could be one or more capacitors that are changing value as the radio heats up inside. On old tube type or early transistor type with discrete components, capacitors are often an issue and may need replacing.

A photo would be nice - just curious to know what it is.

 

[Kevin54]

Get a better antenna

 

[henrysgarage]

Can I just loop a run of wire to get reception?

 

[htmdude57]

What you need to get is a receiver that has a Phase Locked Loop.

 

[James-W]

Just get a different radio. Sounds like what you have is pretty old, maybe you should look into getting a satellite radio. I realize there is a yearly cost involved but they do work well.