TV Aerial Amplifier

castaway

castaway

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I now have a little gadget that I can plug into my USB port on my laptop which will allow me to watch TV should i wish to (and only for the News and weather of course).

It came with a puny little aerial that doesnt even start to detect a signal but I have got my hands on a Glomex omni directional unit but without the amplifier.

To replace the amplifier with a Glomex item is 59 quid or so and I really dont want to do that.....Of course millions of these for sale on the we but all are for domestic 240v type applications.

Can anyone help me on locating a 12v driven (reasonably priced) one? Or any suggestions?

BTW I've been looking at caravan gear suppliers and they only seem to sell combined aerial/amplifiers.

Thanks Nick
 
What you want is a masthead amplifier. These are powered by 12 - 24v (wide range) either from a distribution amplifier when fitted or a separate mains power supply. Easy to run instead from your boat supply 'cos it's not voltage sensitive as indicated above.

Available from CPC / Farnel - large choice and almost certainly from:-

Maplin
Electrical wholesalers like QVC, TLC and the like
 
You should fit the antenna and try it without the amplifier. it is quite possible that the performance will be adequate.it will save a lot of bother. olewill
 
I had seen these 'masthead amps' and wondered if it would be possible to use one....So do you think I could lead the co-axe from the aerial down to the cabin..into the 'masthead amp' and with a short connection to my TV or laptop..also keeping the power lead to the MH amp short and easy?

Or does the masthead name imply that it has to be mounted up next to the aerial its self..?

Many thanks ..Nick
 
It will probably work in either position and you probably won't be able to see any difference; but the signal to noise is governed by the noise at the input to the first amplifier in a chain and also by the amplifier's internal noise, so the correct place to put it is as near the antenna interface as possible. (Else the "signal to noise" at the receiver input will be lower because any noise picked up in the cable will also be amplified along with the signal.)

Alan.
 
A mast head amplifier is mostly used to improve the level of signal before the signal is diminished by the losses in the cable. At UHF frequencies these can be quite a lot. As Alan says it is important that the signal is not allowed to get too small because it then becomes comparable in level to the natural noise of the amplifier be that the MH amp or the TV s first amp.
So if you put the MH amp at the TV it will be no better than the TV s own first amp whcih is usually quite afequate. (though in some cases it can help) olewill
 
have a look at this thread from earlier this year, (or search for triax)

http://www.ybw.com/forums/showflat.php/Cat/0/Number/1057419/page/0/fpart/3/vc/1

I was considering a Glomex but I bought a Triax UFO aerial after reading Dogwatchs' experiences.

Fitted it myself once the mast was down, (bit difficult threading the aerial cable down the mast, but managed it after a few go's).

Power is applied to a little box which is fitted in the saloon... I dont know if this is the amp, or if the amp is built into the aerial... power must be fed up the aerial somehow, as a little red light comes on on the bottom of the aerial so you can tell it is working... so there could also be an amp up there.

In Glasson Dock, Falmouth Visitors Marina, and a few miles outside the lighthouse off St. David Head, the picture for 5 analogue channels was crystal clear. Didnt test for digital channels as didnt have a box or PC gizmo.

In Bayona, picked up several Spanish channels clearly.

In Lagos I think there are 5 analogue channels, of which 3 are crystal clear, one is OK, and one is very fuzzy.... I think this is due to our position and reflections etc., but I dont know. I've got a DVB gizmo for the PC now, but Portugal doesnt have DVB/digital freeview yet, so it's not much use yet.

Hope this helps a bit

Richard
 
[ QUOTE ]
...So do you think I could lead the co-axe from the aerial down to the cabin..into the 'masthead amp' and with a short connection to my TV or laptop..also keeping the power lead to the MH amp short and easy?

Or does the masthead name imply that it has to be mounted up next to the aerial its self..?

Many thanks ..Nick

[/ QUOTE ]

In case you are confused by the posts following your one to me, just to clarify / or reiterate what other have said:-

You could do what you said (put it by the laptop), but there's no point.
Yes, the amp goes at the aerial end 'cos that's where it works best.

BUT what nobody bothered to explain is that you send the 12-24v DC up the coax cable so no separate power cable is needed. Clever innit?

What you must do is to have / make an "injector" so that the DC only goes up the aerial and NOT back to your pc. This means putting a small capacitor in the signal (centre wire) between the PC and the downlead. The easiest way to do that is to get a masthead with separate power supply and throw the transformer away.

Unless someone here can draw you a circuit with the correct component values.
 
Ahhh...so! the power goes up the co-ax...but in summary what you are saying is that what I want is :

a) the masthead signal amp up the mast and near the aerial.

b) a power supply, presumably this can be mounted somewhere convenient and has a 12v power input, and this will then send the power up the co-ax to the amp.

c) I use the PSU but only for the circuit and chuck out the transformer thus making it a 12v unit rather than 240v ...???

I think I've got it now!

Thanks again Nick
 
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