Radio bleed through question

[SpringHeeledJack]

I'm asking this question here primarily because you chaps might have a better understanding of radio transmission and it's idiosyncracies. If this is the wrong forum please move it on to where it belongs :ok:

I was listening to my pocket radio today, to LBC 97.3FM to be precise and was painting some decking in the sun. All well and good, however, I noticed that when I moved in a particular direction in a particular place I was able to listen to the approach frequency at LHR! The radio goes up to 107FM and has an antennae that is boosted by the earphone cord and perhaps the user. I was surmising that the cord was acting as a tuner that was able to jump the range of the radio. Assuming that the LHR frequency is 118.0 to 125.0 somewhere, that's quite a jump from 97.3.....

Anyone care to give an in-depth explanation, apart from that I might be able to start a personal radio station :8


Thanks


SHJ

[Lon More]

Harmonics. Way too complicated to remember all the details after 40 years:)

Buy a decent radio!:D

[SpringHeeledJack]

Buy a decent radio!

How very dare you sir! One has an 'official' BBC pocket radio I'll have you know. Harmonics, eh ? That seems to ring a bell :}


SHJ

[HEATHROW DIRECTOR]

You will probably find that the intermediate frequency of the radio is something like 10.7 mHz. If you double that and add it to the frequency you were tuned to you'll find it comes out pretty close to the frequency you were hearing. Little pocket radios - and many of the scanners so beloved by spotters - are of poor quality and lack "filtering" to prevent such problems. They are wide open to strong signals too. If a police car or taxi drives past you whilst the occupants are using their transmitters you'll probably hear them too, no matter where your radio is tuned.

[RAC/OPS]

And try not to listen to ATC freq's on your FM radio cos it's against the law:rolleyes:

[RJ Kanary]

Also, a well constructed FM receiver will by it's nature be ignorant of VHF- AM Aero transmissions. One that does not possess adequate AM rejection can be easily swamped under an approach path.

RJ

[DenhamPPL]

I presume you live somewhere under the ILS for Heathrow?

Hearing the aircraft calling tower/director (accidently) while listening to LBC was how I first got interested in aircraft when I was a boy living in Fulham. I then went on to work for LBC which is a bit weird:bored:

It can happen even with expensive digital PLL radios as well as cheapo transistor ones.

Certainly helped with my RT for the PPL:ok:

DenhamPPL

[eastern wiseguy]

Certainly helped with my RT for the PPL


Oooerrrr...enter HD stage left:}

[2 sheds]

I presume you live somewhere under the ILS

Explain..?

[SpringHeeledJack]

I presume you live somewhere under the ILS for Heathrow?

Hearing the aircraft calling tower/director (accidently) while listening to LBC was how I first got interested in aircraft when I was a boy living in Fulham. I then went on to work for LBC which is a bit weird

No, not under, but off to the side by a few miles. However, surely the RT wouldn't be more likely to be erroneously heard under the ILS than not ?

That you had the same bleed through listening to 97.3 is strange, though as HD stated it might well be the perfect frequency to correlate with LHR at times. Working for them (LBC, not LHR :}) is pretty weird in a coincidence sort of way though...


SHJ