HI, I have a problem with my valve radio and I'm finding it hard to explain it. As I tune into a station, a high pitched tone is heard , the tone goes up and down in frequencies as I turn the tuning knob. its hard to enjoy the station when theres a high pitched tone covering the station. is here a fix for this? thanks guys.

Could be heaps of reasons. Is it just this radio that does it?

A bypass capacitor could be missing or faulty. If it contains valves that need a shield, said shield could be missing or disconnected from earth.

Hi Buzzer, does this 'tone' happen on every station?
Fred.

Hi no only on one

Albeit in my case the chief offenders here have and are likely to be non-compliant RFI generating Wireless Internet boxes. These actually transmit a scanning RFI; Not a fixed one.

Anything that scans frequencies rather than has a fixed one. If I need to calibrate an AM radio:
The UPS has to be shut off
The NBN has to be shut off
The computers must be shut off.

Mains has filtering to get rid of RF & lightning surges riding on it, from miles of power lines (rural).

Switch mode powers supplies are a horror and I have sent LED flood lights back for killing all bands including FM. Some electronic lighting ballasts apart form being garbage & not lasting (all in my new house have failed, some inside two years) can also be noisy. Rather indicating we don't need regulatory authorities that are ineffective.

Your clue is to look at anything that scans, like Smart Meters, Scanners and Computers. You can systematically shut some of these things off and another way that often works is the small transistor radio in proximity to the generator of the RFI.

I have had a FAX PSU working near the IF frequency (175kHz) of one of the older radios getting in via the IF.

Unfortunately, to have any hope of fixing you have to find the source.

If the whistle is at around 900-910kHz it might be an image response to a strong local transmitter, if the intermediate frequency of the radio is around 450-455kHz. This would be more likely in 4 valve radios with low selectivity.

It might be useful to know the radio.

Do short out the antenna if its a transformer set and see if it persists. If it does, its liable to be internal and related to new caps, or lead dress.

Many HMV sets IF's are not 455kHz early radios can be 460kHz IF and lower. I have had an STC Autodyne (Screen grid type) with a superheterodyne whistle caused by lead dress & modern caps in the area of the 2nd detector / first audio can get induction & radiation issues from modern caps.

One usually does some probing with chopstick to see if the frequency changes if something is moved slightly.

An oscilloscope is handy here as you can see the wave form & that can tell you what specific type of device creates that wave form.

Hi, what frequency or what is the station call sign.
Fred.

I had a similar problem with a 1940's STC radio I was restoring.

It turned out to be the Goat shields on the oscillator and I.F tubes not making good contact with the chassis ground.

Cleaned the shields and the earthing tabs with some emery paper and problem solved.

Does your radio have tube shields?