Internal FM aerial query

[ARW]

Brilliant.

Thank you

[jkn]

Somewhat OT, but also somewhat germane...

Quite some years ago I made a large FM antenna for use with the (insensitive) Leak Troughline tuner I had recently bought. It was a design I got from the 'net, and was square, about a yard on each side. I made it from some small diameter copper pipe I had knocking around for other purposes.

The 'novel' thing I remember about it was that the copper was shaped into two turns of a 'square spiral' - that is, the copper first went round the overall

1yard outline, but you then turned it to form a smaller square of .. perhaps a quarter of that dimension?, inside the larger square. It might be that this gave some impedance conversion, I didn't need a balun IIRC.

The antenna worked very well (we are a fair distance from the transmitter). I gave it away some years later in a clearout, but I remain curious about the design. I've done a search of the (much larger these days) internet, but I cannot find the design I used for this. Does it ring any bells with anyone?

Thanks, J^n

[The Natural Philosopher]

'Folded dipole' might net you a picture.

IME the key to good signal is simply 'area covered'. The tricks to match the impedance get you a tad more, but a Very Long Piece Of Wire will often knock the socks off anything else.

RF fields are 'watts per square meter' - more square meters = more watts.

All these 'amazing pocket sized aerials' are crap in the end. We barely got usable signals out of ferrite rod aerials in AM radios back in the day.

[Dave Plowman (News]

You listen to R3? Respect.

[jkn]

No, it was nothing like a folded dipole

[Andrew]

I've realised that my 'new' Denon M41DAB mini hifi picks up DAB signals tolerably well in my upstairs 3rd bedroom/office that faces North using the supplied T aerial when it is hung vertically from the ceiling, but R3 is now only 160Kbps. I'm sure the last time I used DAB to listen to R3 it was on 320Kbps. When was it downgraded ?.

[Andrew]

"The moor is covered with moss-peat to depths of up to 12 feet and masses of this unstable material had to be cut away to expose firm ground in which to bed the foundation and stay-anchorages."

Well that would need a public enquiry and years of delays by the greenwashies if was done today :-(

[Andrew]

Not this one was it :-

[charles]

Mine shows 192k.

[williamwright]

Luckily my amnesia as made me forget that. Otherwise I'd be upset.

Bill

[williamwright]

It doesn't sound like a folded dipole.

Once a non-resonant end-fed aerial exceeds a small number of wavelengths the extra length thereafter adds nothing. As an example consider a 10 metre wire feeding a UHF TV set. That won't work any better than a 50cm wire.

That's debatable. I used to listen to Luxy on a home made radio that used a ferrite, as a kid.

Bill

[williamwright]

That was in the days when the BBC used to pay people to play about with aerials and then spend weeks writing it up. The whole thing is very derivative; much inspired by virtually any standard antenna book of the time.

Bill

[Mark Carver]

I've still got the pages I photocopied from my local library's copy of Gordon J King's 'Practical Aerial Handbook' in the 1970s.

[Mark Carver]

It was never 320 kb/s (no domestic receiver can support that anyway)

R1,2, and 4 were at 192k, and R3 was 256k from 1995 until about 2001

You're both right. R3 sometimes drops to 160k to accommodate 'pop up' stations

[ARW]

You would not believe how many metacarpals and phalanges I have broken when an apprentice has tried to change the radio station on the van without asking.

[ARW]

Remember it's your turn to pay next time:-)

[The Natural Philosopher]

From your description it was a folded dipole, just folded up in a different to normal way.

Think origami = folded paper.

[ARW]

[Tim Streater]

Luxury. I had to mend the wartime Ministry of Supply radio that had been consigned to the attic, when I was a kid, in order to learn about the H Samuel Ever-Right watch.

[tony sayer]

I suspect it was a "cubical quad" not normally used for VHF/FM reception these days;!...