TX wattage / interference with neighboring TV aerials

[halfwave]

Hi,

Does anyone know roughly how much wattage would be OK to use
so that you do not interfere with neighboring TV aerials.

I ask this as currently my transmitting aerial (as some of you may know
from my previous posts), is in the loft and fed with 1watt. If I go up in
power I am concerned that I may start interfering with the two adjacent
neighbors TV aerials / their TV reception.

My aerial is about about 3 meters away from one neighbors TV aerial
and about 4 meters away to the other neigbours aerial on the other side.
Currently I guess I am not interfering while on 1 watt. But if say I went up
to 7 watt would that start causing problems?

Does anyone know what the safe wattage would be for my situation?
Also is there a way to calculate it, based on wattage v's known distance to
the TV aerial?

Thanks in advance.

[McDonalds]

soon as I turn on freeview dies on my TV on as low as 5 watts with my loft aerial.
though TV downstairs with aerial in garden on pool still works up to around 15 watts if go to 20 to 25 that goes.
it all depends how good the TV signal is to.
also when on 20 watts my stuff starts humming so this why I might change to the half wave aerial soon.
but in the garden the signal is much worse so why my aerial is in loft to as gets out much better in all directions.
my swr goes to 1.3 so least its not doing no damage to my rig.

[teckniqs]

It depends on many different things. There's no way for us to say exactly how much more TX power will affect you.

Sometimes it can be caused by a harmonic and changing the TX frequency solves it, other times it can be a bit harder to resolve with RF power radiating down the TV aerial. If it's one of those Chinese jobbies it's probably a sprog, try changing the TX frequency.

[halfwave]

Thanks for both of your replies.

With out going round the neighbors and asking if they have problems with their TV
I have no way of checking if I am causing interference, unless I buy a TV aerial and
hook it up to see if it affects my TV reception (currently I watch TV through FreeSat
as have no TV aerial).

BTW.
Could my TX cause interference with FreeSat? If so I guess I could then
see if my TV gets interference if I push the wattage up higher. That way then
I could at least work out what max wattage I could use without interference.

[teckniqs]

Thanks for both of your replies.

With out going round the neighbors and asking if they have problems with their TV
I have no way of checking if I am causing interference, unless I buy a TV aerial and
hook it up to see if it affects my TV reception (currently I watch TV through FreeSat
as have no TV aerial).

There's nothing wrong with knocking on the neighbour's door asking them if they are also getting interference and saying you just wanted to check if it was just your TV or if there's a problem in the area - you don't have to blurt out the real reason you're knocking so I expect they'll be none the wiser.

BTW.
Could my TX cause interference with FreeSat? If so I guess I could then
see if my TV gets interference if I push the wattage up higher. That way then
I could at least work out what max wattage I could use without interference.

I don't expect so, FM is VHF and FreeSat is SHF so they are miles apart. Also I'm not sure if buying an indoor aerial for your TV would be a good enough way to check it and good enough to pick up the interference but the neighbour's roof antenna's might...

[Maximus]

Ive seen distribution amplifiers get swamped due to the high amount of rf present.

Also depends how strong the signal is coming from the television transmitter.


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[radionortheast]

it would be really useful if you had your own tv aerial, obviously your tv aerial will problaly be closer than your nieghtbours, you could problaly buy a cheapo indoor aerial, fetch your transmitter aerial, put them afew feet away see what happens, indoor tv aerials are really lousy you might get a bad signal anyway, many people have wasted away messing with them!

as you’ve said you’ve been using your 1w for a year without any problems! and by the sound of it your working on a better aerial system which is the way to go about it other than just throwing watts into the air.

when i had pcs transmitter was runing about 5w, with a tv aerial on the same pole 2 feet away you would loose tv due to how close the aerial was.

remember years ago building 1w stereo transmitter from veronica or nrg, at the time my mum and dad told me there was music coming throught the tv, when i switched to a better power supply went away, really wouldn’t of known!. nrg veronica transmitters could be abit on the effy side, they put harmonics out it would effect my freeview box, if you built them in kits, unboxed pretty sure having a tall heatsink was the perfect wavelenght for uhf..(the output from the aerial was flitered) i would avoid transmitting on frequencies where you would get the herinbone pattern on tv, it was easy to interfere with tv guess its was due to the bandwidth of the signal.

anyway i have no problem with my 3w, thats as close as you’ll get to an aswer, don’t know if theres a way to dial down that power from 7 watts! because i'd hate to say it was ok then something happens.

[shuffy]

You shouldn't do much harm with 7 Watts, but it depends as much on their TV setup as it does on your TX, so you simply don't know. There are a dozen reasons why you might affect a TV with the cleanest rig, and there are a dozen why you might affect your neighbour's TV and not your own. I think the best thing is to do like technics says, put it on air for a week, give them the chance to watch a good amount of telly and tell them you've been getting dodgy reception and ask them about theirs. Then you've got a dialogue going. If you up the power further, they've got a reason to tell you first without suspecting you're the cause. You can then wind it down and ask them if they ever got rid of that problem with their telly.

[halfwave]

Thanks again for all your replies.

I may just test going up wattage in small amounts at a time and see how it goes.

[Steambod]

You shouldn't do much harm with 7 Watts, but it depends as much on their TV setup as it does on your TX, so you simply don't know. There are a dozen reasons why you might affect a TV with the cleanest rig, and there are a dozen why you might affect your neighbour's TV and not your own. I think the best thing is to do like technics says, put it on air for a week, give them the chance to watch a good amount of telly and tell them you've been getting dodgy reception and ask them about theirs. Then you've got a dialogue going. If you up the power further, they've got a reason to tell you first without suspecting you're the cause. You can then wind it down and ask them if they ever got rid of that problem with their telly.

+1. Could be sheer overloading due to the proximity of your tv and tx aerial. Also how good the electronics are in the neighbours tv. I'm lucky that I get on very well with my neighbours, only had one problem with one of them which was a tv in a back bedroom about 7m from my aerial and on higher power they got some pixellation but didn't lose the picture.none of their other tvs were affected. I did a couple of tests with him with varying the power and sussed out what I cold run without problems. Other neighbour whose tv is about 10m away didn't have any trouble at all.