Aerial help!

Hawki007

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Hi all!

I'm about to upgrade my radio fm and dab from non existant to hopefully useful!

I want to ensure that the TV signal does not drop out, we get loss of signals usually in the summer due to interference!

However, we have a powered masthead amp, connected to an antiference a240 amplifier in the loft.

What I want to do is add seperate dab and fm aerials, omnidirectional fm and a linear dab aerial.

I will have three cables coming into the loft, the amp has a combined fm/dab input and a seperate TV input.

My plan is to get a duplexer to combine fm and dab onto one cable before being fed into the loft amplifier.

Is this correct?

What other considerations do I need? The loft amplifier has variable gain controls on it... Will I need to alter these?

Also, there is an output called 'full' rather than TV 1,2, 3 etc. Is this the one to use as it will send all signals down the cable?

Sorry for all the questions but I have tried to find out as much as possible in advance!
 
Maybe you don’t need an amplifier for FM and DAB. How many rooms do you want to feed?
 
It is just one room for all three signals. Would the amplifier try and boost the dab/FM signal as well as the TV?
 
Try the non-TV stuff without an amp. if you’re only talking about one room. Reception characteristics seem to differ between TV and radio in my experience.

Clem
 
1) Do NOT get the omnidirection FM halo aerial. A vertical dipole if you need omni would be far superior.


Keep each aerial at least one metre from any other aerial. Otherwise the elements of one can interact with those of another with unwanted and unpredictable results.

BTW DAB - for BBC - is designed to provide mobile (car) and indoor aerial reception. External aerials are not normally needed. Omni is usually the best - unless trying for a more distant local ensemble from out of target service area.

FM was designed for 2-3 element directional aerials external and 10 metres above the ground.

You need to determine what stations you need and where they are transmitted from to choose the correct aerial style.

It is technically superior to have separate cables for every aerial to the appropriate tuner. Combiners and de-combiners (splitters) always lose some signal and "every little helps" in some cases.



Summertime interference to TV signals can sometimes be minimised by suitable aerial choice and siting of it. Your location would be needed if advice on that was wanted. Amplifiers can sometimes help the unwanted rather than the wanted and should be used with caution.
 
1) Do NOT get the omnidirection FM halo aerial. A vertical dipole if you need omni would be far superior.


Keep each aerial at least one metre from any other aerial. Otherwise the elements of one can interact with those of another with unwanted and unpredictable results.

BTW DAB - for BBC - is designed to provide mobile (car) and indoor aerial reception. External aerials are not normally needed. Omni is usually the best - unless trying for a more distant local ensemble from out of target service area.

FM was designed for 2-3 element directional aerials external and 10 metres above the ground.

You need to determine what stations you need and where they are transmitted from to choose the correct aerial style.

It is technically superior to have separate cables for every aerial to the appropriate tuner. Combiners and de-combiners (splitters) always lose some signal and "every little helps" in some cases.



Summertime interference to TV signals can sometimes be minimised by suitable aerial choice and siting of it. Your location would be needed if advice on that was wanted. Amplifiers can sometimes help the unwanted rather than the wanted and should be used with caution.
That's great, thanks. Our postcode search states we can't get dab, although a high up aerial should be fine as a portable managed to get a bit of signal at ground level.

In the summer, if I don't use the amplifier as this powers the masthead will this cause other issues or will it just pass this signal through?

Unfortunately I'm in a listed cob house so I'll just have to follow the existing wiring... No room for 3 cables unless I chase the walls (no thanks!)

I could always try using better coaxial if needed with a solid copper core.
 
Mastheads generally need power to work. (Televes DAT/Boss range aerials with built in amps may not).

I can't comment on reception (using prediction tools such as Freeview and Wolfbane) without rough idea of your location. Ideally within 100m or so (school, shop, pub, post office etc.,.)

If outwith the official predicted coverage of DAB (BBC and/or others) then a directional DAB antenna may be advisable? It would also suggest FM is going to be less than easy so directional, too, may be required.

Note a FM-DAB-TV combiner will have an insertion loss of around 1.5dB on each band... So -3dB if using as a combiner and de-combiner. (Triax and Blake masthead unit specs).
FM-DAB combiners are about the same insertion loss if using one input of the distribution amp you have.

It's actually considered a pretty bad practice to cascade amplifiers (add one after another) like you are doing; but is sometimes a necessary evil. At least it only has low gain (8dB) itself but does add 4dB of noise. The UHF signal is already losing something by being combined with the other (unused) input so there will only be an additional loss where you split out to the radios at one location.

Do you have details of the masthead make/model (or even just the nominal gain figure) and the TV aerial in use?

What coax is in use currently. Please don't say copper clad steel externally! :censored:
Foam filled all-copper cables are best (WF100, PF100, TX100, CT100)
 
Mastheads generally need power to work. (Televes DAT/Boss range aerials with built in amps may not).

I can't comment on reception (using prediction tools such as Freeview and Wolfbane) without rough idea of your location. Ideally within 100m or so (school, shop, pub, post office etc.,.)

If outwith the official predicted coverage of DAB (BBC and/or others) then a directional DAB antenna may be advisable? It would also suggest FM is going to be less than easy so directional, too, may be required.

Note a FM-DAB-TV combiner will have an insertion loss of around 1.5dB on each band... So -3dB if using as a combiner and de-combiner. (Triax and Blake masthead unit specs).
FM-DAB combiners are about the same insertion loss if using one input of the distribution amp you have.

It's actually considered a pretty bad practice to cascade amplifiers (add one after another) like you are doing; but is sometimes a necessary evil. At least it only has low gain (8dB) itself but does add 4dB of noise. The UHF signal is already losing something by being combined with the other (unused) input so there will only be an additional loss where you split out to the radios at one location.

Do you have details of the masthead make/model (or even just the nominal gain figure) and the TV aerial in use?

What coax is in use currently. Please don't say copper clad steel externally! :censored:
Foam filled all-copper cables are best (WF100, PF100, TX100, CT100)
Unfortunately I'm just using what was there already!
No idea of the masthead, its a hike up over two seperate floors and a flat roof so only want to do it once!
I imagine the current cables are basic so I was aiming to get a load of HD100 as there is little cost difference for 20m.
 

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