advice on televes dat 45 aerial

[jacko]

hi
picking up some local digital terresstrial channels with a televes dat 45.
normally good signal and picture,signal 60 percent and quality 70-90 percent.
occasionally throughout the day the signal quality drops to 10 percent and
i lose the picture.is there anything i can do to boost the signal a bit. in a previous thread i read Rolfw mentioned that you can change the balum for
an amp. i was thinking of putting an in-line amp in the coax.any help appreciated.

 

[rolfw]

If your signal is dropping to that degree, then an amp will probably make no difference, it may well be that you are suffering from an interference source. One of the most common is Amateur Radio, CB can also cause problems, but the latest is the Tetra mast, there are now purpose made filters for it.

 

[jacko]

thanks Rolfw for the reply,
i¨m living in tenerife and the signal is being transmitted from an island
23 miles away.it seems the only thing that affects the signal is the haze
off the sea at certain times of the day,especially when its very hot.
my mate had the same problem with the same aerial and somebody
fixed it for him by fitting an in-line filter (about 1 +1/2 inches square )
in the coax just behind the receiver.but i cannot contact him at the moment
to find out where he got the filter from.sorry i don¨t know the difference
between a filter and an amp.any suggestions please.

 

[Llew]

thanks Rolfw for the reply,
i¨m living in tenerife and the signal is being transmitted from an island
23 miles away.it seems the only thing that affects the signal is the haze
off the sea at certain times of the day,especially when its very hot.
my mate had the same problem with the same aerial and somebody
fixed it for him by fitting an in-line filter (about 1 +1/2 inches square )
in the coax just behind the receiver.but i cannot contact him at the moment
to find out where he got the filter from.sorry i don¨t know the difference
between a filter and an amp.any suggestions please.

This sounds like tropospheric interference.
If the signal strength drops for a considerable period during the day, particularly at this time of year, it could be channels from another station causing the interference, maybe an analogue one.
You would need to know its identity in order to obtain the correct type of filter, but if it is close to any of your DTT channels, you might need a tunable notch filter to eliminate the offender.
If all channels are affected, the tropospheric effect is probably attenuating the signal, and a filter would be of no use. An amplifier may give you problems if there are any interfering signals caused by this effect

Llew

 

[jacko]

hi Llew,
thanks for the advice.
i know a little bit about sats,but i¨m a complete newbie to
aerials and componants.do you know where i can do a search
to look for this tunable notch filter,as the only thing i have
found at the moment are adjustable attenuators,and i don¨t
know what purpose these serve.thanks

 

[Llew]

hi Llew,
thanks for the advice.
i know a little bit about sats,but i¨m a complete newbie to
aerials and componants.do you know where i can do a search
to look for this tunable notch filter,as the only thing i have
found at the moment are adjustable attenuators,and i don¨t
know what purpose these serve.thanks

There is some stuff on this site covering aspects of TV interference :-


http://www.wrightsaerials.tv/articles.html

As for obtaining an appropriate filter, it might be best to enquire locally of an aerial installer.Taylor Bros. of Oldham UK do them but might be trade only.

Llew

 

[rolfw]

The margin rising device for the DAT45 may help, it certainly isn't expensive, but if you say that your friend had a filter fitted and it solved the problem, then that is what you should be aiming for.

An Amplifier will amplify the signal, but amplify noise as well, whereas a filter will as it suggests filter out unwanted transmissions on different frequencies, which may be causing interference or attenuation to the required signals.

High output VHF signals are renowned for causing upset to their higher frequency UHF neighbours.

There are some nice combined units now, which serve as an amplifier and Filter/channel equaliser, but the price is prohibitive for anything other than large commercial applications.

 

[jacko]

thanks both for the replies,
i think i¨ll try the filter method first,as soon as i
can contact my mate.