Interference from mobile phone masts.

Rippy

Has anybody experienced interference on terrestrial reception from phone masts?
I have seen it all to often lately at different sites.
What they have in common is athey are all within 0.5 km of a mast and all having to use high-gain masthead amps.
Iterference can range from black lines on pic. to total breakup on some or all channels.
Interference is worst at the higher frequencies
I have found the best way to counter this is to use a sat-combiner (usually used to combine satellite with terrestrial onto one cable) as a low-pass filter between the aerial and the amp.
Most cases it works very well.
The point is,I think the moile phone companies should be paying for this, not the customer. Anybody tried getting them to
1/ admit responsibility
2/ Pay up!

byte

I can't say I've come across any homes with that problem, though I probably will soon.

Kudos on your method of getting rid of the problem though. That piece of info could prove useful in the future.

As for the operators admitting responsibility, I doubt it very much.

Ulsterman 1690

Why should the mobile companies have to pay ?

The "Interference" you are experiencing is caused by the poor design of your masthead amplifier and/or TV which is unable to seperate out an RF signal transmitted on a totally different frequency

What about all the shortwave radio listeners in your area whose listening is being disrupted by timebase oscillator radiation from YOUR poorly designed TV should THEY be banging on your door looking for compensation

Of course the mobile phone company may agree to provide you with a filter as a gesture of goodwill (If you ask nicely) but they are not obliged to

watty

Generally contact the producer of interference. Transmitter operators are almost obliged to check out the problem. They may suggest your equipment is at fault of course.

Comreg is avenue of last resort. If you have evidence you did contact an operator (of anything), and evidence of a problem they will investigate.

Rippy

I agree in part Ulsterman, it's a pretty poor show that triax ( or any other manufacturer AFAIK ) do not actually have a low pass filter in their range as that would be tantamount to admitting there was a problem with the selectivity of their amps. By the way, even the so-called "grouped" amps seem as prone to this as the wideband stuff.
As for the phone operators, with the huge opposition they get to masts being sited in any residential area, (despite everybody wanting good phone coverage in these same areas)if the press picked up on them 'causing TV interference(sic) and leaving residents to pick up the bill!......Very bad PR indeed.

Ulsterman 1690

it's a pretty poor show that triax ( or any other manufacturer AFAIK ) do not actually have a low pass filter in their range as that would be tantamount to admitting there was a problem with the selectivity of their amps

There should be low pass filtering as well so that they dont get "interference" from TETRA or 430MHz ham shuff

Of course few manufacturers will produce quality filtered and screened amps when there are so many cowboy installers out there prepared to penny pinch by using inferior alternatives :mad:

lawhec

Problems of interference to TV reception from mobile telephone masts are not recent. I remember hearing back in the 1990's of people who had satellite TV (analogue at that time) whose reception was being wiped out regulary on some channels. Turned out that they were sited very close to GSM900 base stations, signals from these base stations were entering into the co-ax between the receiver and the LNB which would then interfere with received satellite signals that were down-converted by the LNB into the 900MHz range. Better (double) screened co-ax cured most problems (CT100 cable etc and the like) but in some cases triple screened cable was necessary.

Recently trouble has been caused by the siting of TETRA masts and their operations. These lie at frequencies just below the UHF TV band. Problems became fairly widespread especially in areas which were close to such masts (which output more power than mobile phone base stations) where viewers had Group A or wideband aerials that were vertically polarised and had masthead amps. The interference given on an analogue display was given the name "Tyre marks" because of their pattern. Antiference I believe developed notch filters to help installers combat the problem while in some cases double-shielded coax, shielded masthead amps etc. also helped.

In the OP case it is not necessarily the fault of the mobile phone companies provided that they stick to the guidelines of their licence. The problem is more likely, as Ulsterman has pointed out, to be down to something working below par. This could include using wideband unshielded amps, dodgy co-ax or a lack of selectivity or poor front-end of the tuner in the TV. Any new installiation of a terrestial TV setup should at the minimum use RG6 or even better, CT100 cable and if a masthead amp is needed, make sure it's shielded and grouped if necessary. For DTT when it eventually comes (and hopefully it won't be that long now) preventing interference to the signal will become just as important as its strength, and take that from those who've been dealing with DTT signals for a while now.

Rippy

Northern Correspondent wrote:

Recently trouble has been caused by the siting of TETRA masts and their operations. These lie at frequencies just below the UHF TV band. Problems became fairly widespread especially in areas which were close to such masts (which output more power than mobile phone base stations) where viewers had Group A or wideband aerials that were vertically polarised and had masthead amps. The interference given on an analogue display was given the name "Tyre marks" because of their pattern. Antiference I believe developed notch filters to help installers combat the problem while in some cases double-shielded coax, shielded masthead amps etc. also helped.

QUOTE]

I read recently that the Gardai are going to phase in a TETRA system in the near future. I expect to see more "tyre marks " than race day at Mondello Park as soon as testing starts. Northern , have you used the Antiference filters and how well do they work?
As for DTT, surely not an issue for years yet!

lawhec

Rippy wrote:

Northern Correspondent wrote:

Recently trouble has been caused by the siting of TETRA masts and their operations. These lie at frequencies just below the UHF TV band. Problems became fairly widespread especially in areas which were close to such masts (which output more power than mobile phone base stations) where viewers had Group A or wideband aerials that were vertically polarised and had masthead amps. The interference given on an analogue display was given the name "Tyre marks" because of their pattern. Antiference I believe developed notch filters to help installers combat the problem while in some cases double-shielded coax, shielded masthead amps etc. also helped.

QUOTE]

I read recently that the Gardai are going to phase in a TETRA system in the near future. I expect to see more "tyre marks " than race day at Mondello Park as soon as testing starts. Northern , have you used the Antiference filters and how well do they work?
As for DTT, surely not an issue for years yet!

TETRA is to be an EU wide standard for communication amongst emergency services so if the Gardai haven't already started using it, they will soon. There was a case where TV reception in Dungannon was being interfered with because of a new Tetra mast in use by the PSNI in the town. Haven't used these notch filters from Antiference yet, I don't do many installiations myself, more from personal experience and helping friends and family, and thankfully most of these tend to be in "quiet" areas where manmade noise is few and far between. I would expect these filters to work in a similar vein to CB notch filters that have been common in the past.