Faulty TV aerial distribution amplifier?

[Dave Fawthrop]

| >>>

| >> I mostly did my testing using a portable TV in the loft, firstly plugged | >> into a spare output, and then having unplugged all the other outputs. | >> Didn't seem to make much difference. I don't think I tried it in every | >> one of the outputs, though. What causes shorting? (Just occurred to me | >> that as my aerial is in the loft, a storm seems an unlikely reason??) | >

| > Shorting could be caused by nailing through a cable, or a crap connector | > at one end (or a fault in a TV/VCR Etc.) | >

| > If you tried a few, with all other outputs disconnected, it sounds like | > the unit has failed for whatever reason. | >

| > Do you have a mast head amplifier too (another box of tricks, usually | > right next to the Ariel)? | >

| > Sparks... | >

| Not sure about the masthead, will check it out when I can, won't be for a | day or two though. But as I said, the picture is fantastic when I simply | bypass the amp unit. Thanks for your help thus far, I'm inclined to try | replacing the amp box.

If you do IME one with "F" connectors is much better than the normal TV connectors, and if you end up changing coax, use Satellite grade, with copper foil and copper braid which is IME much better.

[Andy Hall]

Along these lines, you can get distribution amplifiers with a number of built in outputs on the box and a high level output.

This be connected to passive splitters (very inexpensive - about £3) perhaps located closer to several sockets on the ground floor or first floor. The advantage is shorter and easier cable runs.

[dave stanton]

Mainly RF power devices, not small signal amplifiers.

Dave

[Harry Bloomfield]

Frank Erskine presented the following explanation :

You will only find this in the high power devices where heat needs to be got out of the device quickly - transmitters, not in small signal amplifiers such as the item in question.

[John Laird]

[scratches head]

I'm still trying to work out how a simple question like "are these tiny" led off so quickly into a discussion about dangerous chemicals...

(Don't worry - I'm not new to Usenet :-))

[Timbo]

OK so I'm planning to buy a new TV distribution amplifier. Can I get a little help?

My existing one (assumed faulty) boasts a frequency range of 40-900MHz. Maplin have a 6-way and an 8-way model (nos YZ86T and KR20W), both with a frequency range of 47-230MHz.I've seen other models on ebay quoting near to the 900Mhz top end. a) is the much lower top end of the range on the Maplins a problem for TV signals? I'm afraid I've no idea whether it's important or not. b) the two Maplins models are the same price - is there any reason not to simply buy the 8-way one?

Any advice appreciated.

[Frank Erskine]

You'd do best if you avoid one that covers around 170 MHz if you live anywhere near a main road. Most taxi radios operate around the

160-170MHz range; if they "key-up" anywhere near your sensitive amplifier you'll very likely get breakthrough, or at least overload of the amplifier causing all sorts of problems. If you want really reliable reception of _TV_ and aren't interested in FM or DAB reception via the same amplifier, get one which operates on UHF only.

[John Laird]

That sounds like the FM range. It doesn't even get into the TV band, which would be a slight problem if it was indeed all the unit could manage ;-) A minute's Googling turned up the spec for the UHF range as 470-862MHz. That's fine.

Probably not. My own amp is looking a bit iffy, but I wasn't keen on what seemed to be the somewhat high gain quoted on the Maplin units - they claim

12dB per output. Fine if your signal is somewhat weak, but if you are distributing the signal (as I do) from the digibox and VCR chained together, then each of these has in turn typically added a small boost already. My Taylor unit says 2dB on it - it's basically just distributing and only amplifying in the sense that 8 outputs from 1 input does require amplification. There have been times when I have found a 6dB attenuator on the amp input has reduced some noticeable noise and visible artifacts.

[Timbo]

Thanks for the reply. See my reply to the post above!

[Timbo]

I wish I knew how you found that out in 1 minute's googling - I've hunted high and low and can't find it - any google tips?

Meanwhile I went to Maplins and bought a slightly different model (it's what they had in stock) the L24AG, which is one of those ones with a digital by-pass. Anyway, I've plugged it in and now my picture is near PERFECT on all TVs. So the old amplifier was faulty for whatever reason.

Incidentally, this model has a gain of 6dB on each output. I'm distributing the signal from the loft, near the aerial. I don't know about this digital by-pass thing as we have cable TV.

Thanks everybody for all the help.

[John Laird]

I happened to know it was branded SLX (as I'd looked at them in my local maplin). Second link under "SLX 6-way amplifier specification" got me the info you needed. Always give Google a selection of words to go on. Specification was probably the key here.

I have Google's Toolbar loaded into IE and Firefox. Search engine is set to google.co.uk as this nicely pops up results with the additional "Search UK pages only" button. Not fool-proof, but pretty reliable.

When looking for prices, I usually add VAT into the search string.

Apart from that, practice is the key. I have misspent a lot of time online ;-)

[Rob Morley]

Search for uhf-tv frequency-range on google.co.uk, selecting "pages from the UK"

[Timbo]

Thanks. I think you were quite lucky with that one, though! Other search variants don't find that site.

I too use the Google toolbar in the way you do. Nice idea about VAT for prices.

The 6dB box I've bought is certainly doing the business for me, no idea whether 12dB gain would have caused any problems.

[The Natural Philosopher]

Beryllium.