Dual UHF (H&V) aerial setup query?

Westford

I'm replacing some aerial equipment, and was looking for some general advice on best equipment & best practice. At the moment there are 2 UHF aerials in place. One taking the Irish channels from the Clermont Carn transmitter (52,56,66,69 Vertical) & the other taking the UK channels from the Divis transmitter (31,27,24,21 Horizontal). The reception of the UK channels was never perfect, but now it has degraded to an unwatchable level. Since both of the aerials have some wind/storm damage, I planning on replacing both, with a Group C/D & a Group A high gain antennas. There seems to be ghosting on the UK channels, so I'm hoping to get a decent length Group A antenna (was looking at the Triax UNIA 100A). While the mast is in an elevated position, my main problem is that I have a longer than normal cable run tot he house. I plan on replacing the cable as well. So any advice, recommendations, or pointers on antenna's, masthead amps (I guess I need a good UHF, with 2 inputs), or loft distribution boxes, would be greatly appreciated.

Mayo Exile

Where are you living exactly? Sounds like the northeast judging by your current aerial setup. For Dundalk Town, the usual setup is a vertically polarised group C/D aerial for C.C. and a horizontally polarised Group A aerial for Divis. A masthead amp is required for Divis. Run the cables for these aerials to a group A, C/D combiner allowing throughpass for the power to the Divis aerial masthead amp (group A). How long is your co-ax in place? Probably degraded due to the weather at this stage. For the long cable run use good quality "copper on copper" (CT100) co-ax cable. Will reduce loss and interference.

See Ulsterman 1690's thread on why you need good quality co-ax:

http://www.boards.ie/vbulletin/showthread.php?t=264065

P.S. As Paddy C says below it gets more complicated for DTT reception if you want that! You might be needing Group W (wideband) aerials then.

Rick_

TG 4 is on 68, not 69. Not that important, but I just thought I'd point it out .

Also, are you looking to receive Freeview as well from Divis? Can you currently get Channel 5 on CH 37 from Black Mountain? The combining of two aerials down the one lead usually requires some channel numbers to be blocked out or lowered in strength, so this may cause problems, especially if you intend on receiving Freeview from Divis in your set-up. A neighbour of mine had the set-up you require installed and although he received the 8 analogue channels in good quality, Freeview wasn't such a success as he could only receive 2 of the MUX's because of the equipment the instaler had to use to make the analogue channels work fine.

The full CH number list you want to receive (UK Freeview included):
21, 23, 24, 26, 27, 29, 31, 33, 34, 37, 48, 52, 56, 66, 68

Hell, if you wanted to receive the DTT trails from CC as well then you will have all these!:
21, 23, 24, 26, 27, 29, 31, 33, 34, 37, 48, 52, 53, 56, 57, 60, 66, 68

lucernarian

Those Triax Unix100's are hefty aerials. Are you certain that the ironmongery is up to the task??

What mayo exile said, was the gist of it. I don't know of what amps to use in particular. I suppose, go for ones with low noise values and screening if possible. I'm not sure about what sort of gain you would need. You'd need to tell us whereabouts you're from and even then it's a guess. For Divis, it's probably a case of the higher, the better.

Interference with the muxes by Irish transmitters could be a big problem. I'd say that's why Paddy C's neighbour could only get 2 muxes.

Westford

Thanks for the correction on TG4 ch.
The location is south Monaghan.
Ok....so I'll need a (A) / (C/D) signal combiner or diplexer.
And a mast-head amp (only for the Group A antenna for Divis) ....I'm guessing the higher the gain the better.
And a loft TV distribution amp.
Anything else?
I shouldn't need any mast-head amp for the Clermont Carn C/D aerial....Right?
I'd estimate that the cable run is about 40m-50m.

Regarding the Q, about Ch5 from Black mountain.... Not tuned at the moment.
Good point on the other channels Paddy C. However at the moment the preference would be to have a good reception for RTE 1&2, TV3, TG4, BBC 1&2, UTV, and Channel 4. For this reason I'd rather go with group specific aerials with a good gain, rater that a wide-band aerial, with a lesser performance. At least for the Divis antenna.
For this one I was looking at a Triax (UNIA 100A)....17dB gain, with 100 elements, and a reception angle of 11 degrees. Is this over-kill, or is there a slightly cheaper alternative.
Any other good sources for such equipment (other than cponline).

lucernarian

What's your Irish channels like at the moment? Does the Clermont Carn aerial have a masthead amp?

byte

What aerial do you have in place for Divis at the moment?

Personally, I don't like Triax UNIX 100's. They're far too weak for their size, and not fond of windy weather. I'd opt for the more robust Hirschmann equivalent (can't think of model now). Mast would need to be a minimum diamater of 2". How long do you intend for the mast to be?

As already said, good quality copper-on-copper cable.

If your RTE/TV3 signals are not being amplified by a masthead amp, I'd suggest using a Group A masthead amp with variable gain. The likes of Triax for example, have a Group A amp that can be varied from 24dB to 34dB gain.

You'll also need, of course, an A/E diplexer, with power pass allowed on the A side.

watty

I found a pair of Blake 18 elements stacked performs better than Triax Unix100

Westford

I didn't put the current equipment in place, so I'm not sure of the details. The mast is about 3" or 4" tubular steel....About 20' in height, mounted on the equivalent of a 3 storey building.
Resonably sure that the current aerial for CC does not have a mast head amp. Any particular benefit to opting for a variable gain amp, over a fixed high gain unit? Interesting comments on the Triax Unix 100's....

byte

20 feet high? On a 3 storey house! :eek:

Well, I sincerely think you shouldn't put up a Unix100. Though it's up to you. Better than the Hirschmann, would be an Antiference XG21, dunno how easy they are to get, but they are fairly more expensive. However, they are very robust.

If you do go down the route of a UNIX100, I recommend you tape up or cable tie the cap for where the cable is connected to the dipole. Should do so for any aerial, as the caps can blow off, and when it does, you gradually wave goodbye to signal, and probably amp also if cable is airspaced.

I suggested variable gain amp, incase a fixed high-gain amp ended up overloading. With variable, you can adjust if signals start oscillating.

Rippy

byte wrote:

If you do go down the route of a UNIX100, I recommend you tape up or cable tie the cap for where the cable is connected to the dipole. Should do so for any aerial, as the caps can blow off, and when it does, you gradually wave goodbye to signal, and probably amp also if cable is airspaced.

Second that! Triax dipole caps are crap. There are loads off around here and I find them a great source of income.:D
I use Triax myself but cable tie them all. No one else seems to bother.