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RF Signal level Tester


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I'm guessing you're talking about an analogue TV signal.


Any time I've had to do this I've borrowed an aerial tester from my mates in the AV department at work. Basically, you plug it in, dial up the frequency, and read the signal level of the video channel off a meter.... Tune it in 6MHz higher, turn on the speaker, and you should be able to hear the audio...


It's a specialist tool, but something every TV aerial installer should have. I'd be tempted to just pull the cables, terminate, and see if it works. If not, give a friendly TV installer a call, and offer them a few beers or similar for some "consultancy", or a loan of their meter :-)



Related story: We needed to install a new aerial at work, to feed a DVB-T receiver. The imminent winter olympics and world cup are, of course, completely unconnected with this requirement.


We already had some old RG6 cables running from our department up to the roof. Not ideal, but we thought we might as well try them, rather than running new cables.


So my mates in the AV department specified one of CPC's finest aerials, a masthead amp, remote PSU, and a bag of F connectors.


The aerial arrived. On the large side - resembling a christmas tree. Mounted it on an existing pole on the roof, and ran 10m of CT100 to a nearby plant room. There, we installed the masthead amp, and connected to the old RG6 downleads.


We didn't have the meter at this stage, so pointed the aerial roughly in the same direction as the one on the building across the road.


Down below, we connected everything up, and plugged it into the receiver - a DVB-T card in a PC. Turned it all on, and..... nothing.


So we re-checked all the connections, to make sure we hadn't shorted screen to signal, and all the usual stuff. No joy. We eventually gave up, and arranged for the experts to come over the following day with the meter.


Plugged the meter in, and discovered the incoming signal was about 100 times STRONGER than it should have been, and the receiver was saturating! So, reduced the gain on the distribution amp to minimum, added various attenuators, and it all worked perfectly!



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Does anyone know of a cheap Rf signal level tester other than an expensive spectrum analyser so I can test each socket? other than lugging a TV round.

Depends on your definition of "cheap"


I've got a Sadelta TC 402 D TV signal strength meter which is designed for the job, think I got it from CPC but it doesnt appear to be there anymore. It wasn't "cheap", as in a few tenners, but it was "good value" in that it's saved both my ass and lots of time.


When you get your meter, put in its box a selection of adapters, a photocopy of the page of the Maplin catalogue that shows all the TV frequencies and a map of where the transmitters are, and write on the map http://www.kat5.tv/taboo.html which leads you to a calculator you can use to find free channels to put modulators on so that you don't get cross-channel modulation a/k/a interference.


(update) And while I think on, so it seems this is in the future tense - use good quality cable (CT100 min), use a launch amplifier to get the signal strength waay up (if combining multiple sources mix and equalise them prior to amplification), CATV splitters and taps to get the signal back off, and attenuators to drop levels down to something a telly will accept, and the F connectors must be crimped not screwed or you'll be back every other week. And apologies if I'm teaching my grandma to suck eggs :P

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One other quick question, any idea what the ideal strength actual is for a d0mestic TV?

The range is often given as 1-50mV, which is 50-94dbuV. When I used to live in Croydon I got 98dbuV off the aerial, which was line of sight to Cryst0l 7alace! I used to aim at somewhere round 70dbuV (4mV) coming out to the telly, good signal but not likely to overload anything. Its about what comes out of a VCR.


Obfustication to prevent :P finding us and thinking we might know something about tellys ;)

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