Testing a car aerial

Did this just effect the LW/MW reception or did it also peak up the FM reception?

In message , Johny B Good writes

Just LW/MW. As you probably know, to make the input tuning track with the LO, you peaked up the signal near the HF end of the MW. The trimmer had decreasing effect at lower frequencies. The FM would have been a different part of the circuit.

Ah some kind of money making scam then. Anyone remember those trap in the window aerials so loved by car thieves? Brian

The ones I encountered peaked medium wave, had little effect on long wave, and had no effect whatsoever on FM. I used to peak my radios for the HF end of medium wave because that's where Caroline was!

Bill

No.

Bill

Thanks for that extra info, Ian.

That's just about what I was expecting. Obviously, they don't use a 'VHF section' on a common tuning coil but a completely seperate front end tuned more conventionably with its own tuning capacitor. I guess the screened cable must simply be used as a Hi-Z co-ax for the VHF band signals.

No - sound engineering reasons.

I have a Ford 6000CD in my 55 Focus. Radio reception is variable no matter where I am, even in high signal areas. I blamed the aerial, but no, it appears this range of radios have an inherent fault which shows as weak signals - Google it!

I am based within sight of the Sutton mast + M6J7

Dave

Remember reading somewhere just how little makers spend on OEM car radios. Probably why DAB took so long to arrive, given it was designed to improve mobile reception.

The instructions invariably told you to adjust the trimmer for a peak in volume of a weak station at approx 200 meters.

I remember my father's (later my) 1989 Bluebird having instructions in the manual on trimming, it was something like removing the radio from the dash, tune to a weak MW signal near 1000khz, and adjust a screw until you got the loudest signal.

Can recall having to do it on my 87 Metro which had a very dodgy radio - was one of the base models that didn't come with one as standard, and the aftermarket fit was a very cheap and nasty one!

James

The radios I used to get from the dodgy man on the market didn't come with instructions!

Bill

I realise that you are probebly referring to a time before anti theft codes, but I have often wondered what is the point if any market trader with a laptop can re-write the NVM.

No need on anything other than the newest stuff; there is freely available software that can identify the code from the serial number.

Chris

On some of the up-market vehicles the car 'talks' to the EMU checking the radio model and serial which is coded into the EMU against the data provided by the radio unit. It will not work without a handshake from the EMU rendering it useless to any thief - not that the scroat would know that!

My fairly expensive aftermarket Blaupunkt unit takes an SD card. If it is powered down totally, you need to use the supplied card to initiate it. After initiation, that card can be removed, and stored safely. It will play MP3 etc files recorded to an SD card using that slot - or will also record from the radio to a blank one. All in all pretty clever.

I remember using Radio Luxemburg for this. 208 metres or 1440 kc/s I beleive.

No, quite wrong. Luxy was on 208.4m.

Bill

Marketed as "Fab 208".

Reception in the UK relied on reflection from the Heavyside layer and the reeived frequency varied a lost as a result.