TV Attenuators

[jj4091]

I have just come across these for the first time for sale at S/fix & wondered what sort of problems would be experienced with a TV that you would need to fit one of these. A wikipedia search explains that they reduce signal gain, but I was always under the impression that the stronger the signal the better, as far as TV reception was concerned.

 

[ninjacat]

Too much signal will cause problems by overwhelming the reciever. Most noticible if you live near a transmitter. An attenuator will solve this (if you know how much to attenuate it by or get a variable attenuator).

 

[jj4091]

What sort of indication would you get picture or sound wise & how would you knowhow much

 

[ninjacat]

As I understand it, normally a TV ariel installer will have an (expensive) meter that tells him/ her the signal level for a given frequency/ frequencies. They may also use local knowledge.

edit - things like these http://www.swires.com/

 

[GaryB]

What sort of indication would you get picture or sound wise & how would you knowhow much

The indication is different depending on whether it's analogue or digital TV.

For analogue TV, it can vary but it's normally feint horizontal flickering lines or horizontal herringbone or diamond shaped patterning. There are usually no effects on the sound.

For digital TV, the effects of overloading are very similar to those of insufficient signal - intermittent sound dropout and random blocks of noise in the picture. In extreme cases the picture can freeze completely.

Knowing how much attenuation to use is easy if you have a meter but without one it's usually trial and error. Start with 3dB and work up from there.

 

[jj4091]

Thank you that is very useful information

 

[ericmark]

If like me you live near a Welsh transmitter and an English transmitter you need to use a high gain aerial to be directional to block out Welsh transmitter and also you attenuate, but to receive the English transmitter you use high gain aerial.

Without the attenuator one tends to have two of many channels where same is transmitted by both English and Welsh transmitters.

With Analogue one could select manually which you wanted but with Digital many receivers don't have the ability to select which you want so when paper says channel 30 it may be 140 on your set because so many duplicate channels.