Aerial question/quiz

[Keithstv]

Here's a simple little quiz.

These aerials were installed a few years ago, I assume after the houses they are on have been refurbished. They look good don't they but what is wrong with them?

The houses are located in Boothtown, just outside Halifax, on the A647 heading toward Queensbury and Bradford.

Keith

[AlanBeckett]

The one on the chimney is vertically polarised, the other 4 are horizontal, but they're all pointing in the same direction.
Who's right?

Alan

[Yorkie]

The one on the chimney is vertically polarised, the other 4 are horizontal, but they're all pointing in the same direction.
Who's right?

Alan

I guessed it was the polarisation Al, but I hadn't spotted the smaller one on the chimney, so that was well spotted! (I should have gone to Specsavers!). Presumably the one in the chimney is correct as Keith asked "what's wrong with them" not wrong with "it"?

[pwdrive]

The one on the chimney is vertically polarized and a low gain job, also it's pointing in a different direction to the other four, hard to say without knowing the transmitter arrangements in the area. Low power vertical polarization was mainly used for relay transmitters in poor reception areas, the four horizontally polarized ones look more like high gain jobs. Maybe they switched from relay transmitter to main transmitter after the digital switchover.

Lawrence.

[Steve_P]

Too low down.

Digital TV is very intolerant of multi-path interference - ghosting on Analogue, Nothing on Digital. The roof behind will reflect the signal back onto the aerials, and although they are not pointing towards the roof, there will be enough multipath to affect reception.

Cheers,

Steve P.

[pwdrive]

The location of our aerial is a hangover from when I did the roof and it had to be taken down, at present it's on the ground outside pointing upwards into inter stellar space, amazingly all channels are received ok. I did post a picture of it somewhere on the forum but I can't find it.

Lawrence.

[pwdrive]

Maybe the local vertically polarized relay originally used does not carry all the channels now available from the main transmitter (PSB only?) hence the higher gain wideband aerials could be directed to the main transmitter in order to get full channel coverage. Don't know for sure as all my TV days were pre digital and 4 channels only.

Lawrence.

[Joe]

If you want to know how NOT to do it see: http://www.aerialsandtv.com/cowboyslocker.html

The whole web-site is worth a look.

- Joe

[pwdrive]

That's a good website Joe, bodge aerial riggers.....when I was an apprentice BBC2 was just coming out and I was sent out with an areal rigger as a gopher, he used to wire up the aerial, open the loft hatch and throw it up into the loft dart style, if the signal was bad he would then flog them a preamp....

Getting back to the photo, apparently there is a relay transmitter at Halifax but it does not transmit all the MUX's, only three out of the six, details are on the website you posted.

Lawrence.

[Keithstv]

Youre getting there. It is to do with the polarisation.

The nearest main transmitter is Emley Moor and there is a relay in Halifax.

You're quite right about most relay transmitters only transmitting 3 of the multiplexes, PSB1, PSB2 and PSB3. Although some of the higher power ones such as Keighley and Idle round here do transmit all 6 multiplexes.

I admit to making one error in the photo I only spotted the aerial on the chimney after I'd posted it. I thought that would be a giveaway.

Anyway I'll let it run a little longer.

Keith