"audible" pilot tone

[Phil Y]

Anyone know about tuners ?

Just by chance, last night, I switched my bat detector on while listening to the radio. There was quite a pronounced output at (no, I can't hear that high) 19KHz which I assume is the pilot tone. It was a lot louder on the right channel than left.
Is it normal for the pilot tone to be coming through like this or does it suggest something wrong with my tuner ? It sounds fine as far as I can tell.

I have no idea how loud it actually was as my bat detector is not calibrated for level in any way.

Phil.

[John Caswell]

Hi Phil,
Well normally there is a 19kHz filter somewhere in the way. What type of decoder is it, discrete, chip or what.

John

[Phil Y]

Hi John,

The decoder is a small PCB with a TDA1005 chip. I think it may be the Mullard LP1401. Tuner is Troughline 3.

Phil.

[John Caswell]

Hi Phil,
There is probably a small R/C filter in there, so I doubt you can do anything. There is nothing amiss with the tuner, I guess it is just the decoder. Are you able to beg,borrow, or steal another one to try out.
If it is not noticeable leave well alone.

John

[Phil Y]

Hello John,

I was not especially worried, as I say, I only detected it by accident. Just curious really. I don't listen to a huge amount of radio, well not on my HiFi at least. I don't think I know anyone with a different decoder to try.

One thing that has come back to me, my first cassette deck, a cheap Akai, had a switchable MPX filter for recording from radio. It must have been a known issue for them to include a filter.

Thanks, Phil.

[John Caswell]

Hi Phil,
Yes quite correct, as the 19kHz tone could interfere/ "beat" with the bias oscillator, when in record and give some very strange results.

John