Group A aerial advice for Palace with a problem on Ch22

Hi All,

Wrote on this NG a while back re problem i am having with Ch21/22
(pixellation) on either Palace or Reigate. My installer originally used
a WB aerial, replaced this with DAT 45 (another WB) to no avail.

Followed the advice here to go Group A, which makes great sense for
Ch22.

He's installed a Unix 52 Group A.

STILL got pixellation just on the ITV channels, although less bad. I've
suggested to him he tries a Blake Cat 1 DMX10A, as aside being Cat 1,
it's better gain at low end.

BUT this is based on my inquiry, not expertise!!!! Would any of you
have more specific advice. I don't want to fall into the trap of just
going for more gain if this isn't the cure. This REALLY is driving me
mad.

BTW, a masthead preamp of variable gain makes no difference: eventually
overloads and i lose everything. It's not TETRA either.

If anyone's curious, or needs the detail, i can give you the
post-viterbi bit error ratio etc.

Thanks!!!!

wrote in message
oups.com...
Hi All,

Wrote on this NG a while back re problem i am having with Ch21/22
(pixellation) on either Palace or Reigate. My installer originally used
a WB aerial, replaced this with DAT 45 (another WB) to no avail.

Followed the advice here to go Group A, which makes great sense for
Ch22.

He's installed a Unix 52 Group A.

STILL got pixellation just on the ITV channels, although less bad. I've
suggested to him he tries a Blake Cat 1 DMX10A, as aside being Cat 1,
it's better gain at low end.

BUT this is based on my inquiry, not expertise!!!! Would any of you
have more specific advice. I don't want to fall into the trap of just
going for more gain if this isn't the cure. This REALLY is driving me
mad.

BTW, a masthead preamp of variable gain makes no difference: eventually
overloads and i lose everything. It's not TETRA either.

If anyone's curious, or needs the detail, i can give you the
post-viterbi bit error ratio etc.

Thanks!!!!


If he is a member of CAI he should sort that for you no problem without you
having to do his job for him. I would get two medium gain grouped aerials
and combine them before using a preamp. That might be best to give a decent
signal on the two groups if you see what I mean. I wouldn't bother with
fancy high gain aerials because if you need that then alignment is critical
and the slightest movement will knock your picture off. Most gain figures
are invented anyway, especially for Televes aerials.
How about a log periodic with mast head preamp, that might solve the
problem - or two combined before a preamp?

I live 18miles from my nearest TV transmitter and the ITV channels are
transmitted at a much lower power and the aerials are lower down the mast.
I used various aerials from cheap 18 element, Grid type, and more expensive
ones. The best thing I did was to get two aerials called Philex Megaboost
in a sale in B&Q for £14-99 each. They are log periodic with preamps, coax
etc. I combined the outputs from the mains units and it works great. It
takes a bit of experimenting sometimes. They just sit about a foot apart on
the mast horizontaly polarised.

Best of luck! Digital has a lot to answer for, it's either on or off,
nothing inbetween.

Thanks Jim.

Palace is 22-34. so would a pair of dissimilar aerials be necessary?
BBC is very strong at 25, and Sky/UKHistory also fine at 34, as is Five
at 32.

Can you help me understand how the performance of a pair compares with
a single higher gain?

Thanks

Here's an interesting thought: before i embarked on this sorry journey
i had a pair of old Group A aerials on the mast. They were one above
the other, a foot or so apart, but NOT electrically connected. Would
this have any impact, +ve or -ve on performance?

wrote:
Here's an interesting thought: before i embarked on this sorry journey
i had a pair of old Group A aerials on the mast. They were one above
the other, a foot or so apart, but NOT electrically connected. Would
this have any impact, +ve or -ve on performance?


That's how the aerials are mounted on tenements roofs here in Edinburgh:
each flat has it's own aerial, so, you have up to 5 aerials on the same
mast, less than a foot apart. So, I hope there's no -ve impact!

wrote in message
oups.com...
Thanks Jim.

Palace is 22-34. so would a pair of dissimilar aerials be necessary?

All of CP's output fits in Group A. Why would you need dissimilar aerials?

BBC is very strong at 25, and Sky/UKHistory also fine at 34, as is Five
at 32.

Can you help me understand how the performance of a pair compares with
a single higher gain?

Not my field, but I imagine that the angle of acceptance would be reduced
and the two aerials will reinforce the desired signals.


--
MESSAGE ENDS.
John Porcella

wrote in message
oups.com...
Here's an interesting thought: before i embarked on this sorry journey
i had a pair of old Group A aerials on the mast. They were one above
the other, a foot or so apart, but NOT electrically connected. Would
this have any impact, +ve or -ve on performance?


Aerials close together detune each other, or so someone here wrote some
years back.


--
MESSAGE ENDS.
John Porcella

Not my field, but I imagine that the angle of acceptance would be reduced
and the two aerials will reinforce the desired signals.

Isn't this in the field of Bill Wrights pair of aerials side-by-side to
reduce ghosting? You orient them to optimise direct-line gain whilst
minimizing off-direct? Bill published an article on it which might be
available off his website.

Paul DS.