DAB Aerial.

[pwdrive]

Hi David, yes I understand the dipole stuff, but the link you referred to highlights the point I was making, it starts off by saying a "choke balun" is not a balun but then gives construction details for a "choke balun" and calling it a "choke balun" a better less confusing name would be an antenna feed line balance choke as this would put it's description a bit more into context.

Most of the better quality receiving antennas I have seen for VHF that use a coax feed have a balun fitted either 1:1 or 4:1.

Lawrence.

[pwdrive]

""I know the TV aerial has blown a bit off its correct alignment and at the w/end the reception seemed to go off a bit and today I couldn't get a thing on it - I suspect it's down to a tree coming into leaf""

Hi Joe, if I remember I will take a photo of our aerial for digital tv......and post it on the forum.

Lawrence.

[pwdrive]

As per my previous post, the aerial has been in that position for about 3 months, I had to take it down for some house maintainance, haven't got round to putting it back yet....

Lawrence.

[Joe]

It shows what a Dark Art it is in that what shouldn't work does and what should doesn't.

- Joe

[pwdrive]

Hi Joe, the day I took that aerial down was a busy day, come 7pm we were having our grub and realized that I hadn't put the aerial back up, tried the TV and it worked on all channels so there it has stayed, just sheer laziness on my part, we are near the edge of St Austell bay, the transmitter is at Caradon hill, we are part way down a valley so no direct line of site, I doubt I would get a decent picture if it was still the old analog transmissions.
Did you manage to find a way of connecting an external aerial to your DAB radio? Maybe reverse engineer the front end RF stage and fit a coax socket.
When I first saw the picture in your first post I was a bit confused by that aerial design but I get it now, the striping of the outer insulation on the bottom half of the dipole could be to serve as a permanent indicator as to where the choke needs to be wound, I can't think of any other other reason.
Aerials can be a bit of a dark art, there is a lot of tosh on the internet written about them and a lot of tosh discussed about them on the amature bands.

Lawrence.

[Joe]

I had a go at connecting the co-ax inner to the rod and the screen to the power ground but it seemed, if anything, worse. I can't do much without a diagram and as it's SMD would be restricted anyway.

I've just been making a better coupling coil which seems more efficient and the next thing will be putting the aerial in the loft. Even if it's no better it'll be out of the way. At least there's nobody to complain about me making holes in the ceiling.

   

- Joe

[pwdrive]

Hi Joe, I presume that the telescopic aerial is not the unscrewable type with the F connector?

Lawrence.

[Joe]

No such luck - it was a 99p wonder off e-Bay. It's branded Asda so I can';t even find a user manual never mind the techy stuff. It was sold as Not Working but all that was up was an o/c speaker.

I've tried the aerial in the loft and it picked up NO signal. This wasn't wasted effort as, as the cable was now there, I stuck a pair of PoundLand 'bunny-ears' on it which is giving hiss-free stereo on VHF on my workshop hi-fi. That has both 75Ω and 200Ω inputs.

- Joe

[pwdrive]

That's all avenues explored then Joe, all I can suggest is to whip the back off find the common signal rail (-ve/chassis/earth etc) and wire that to the outer of a suitable coax connector, telescopic aerial to the center of coax connector.
Good luck whichever way.

Lawrence.

[Joe]

Things are developing.

I rigged a TV up and found that the FreeView box wasn't receiving a signal at all.

While in the loft I found another, Philips, one I didn't know I'd got. This is currently scanning and seems to be finding stuff. This is taking much longer than the orginial 'Bush' one does so maybe it'll work.

- Joe