Hi guys n girls I need your help.

I bought a small hand held tv with built in freeview, my problem is that I can't get a decent signal to watch any channel. The arial Is rather small (about a foot) some I'm guessing that's just not enough for this region?



this is it, I took the back off and found out it uses the F type connection (like the wire from a cable box looks like) . Now what should I do? Buy a larger 1.2m arial with an f connection or will that still not be enough? It will kind of defeat the point of a hand held tv if I have to use a powered f connection boosted arial

Connection:

A longer aerial is unlikely to improve the signal by much as the aerial has to resonate at the correct frequency for optimum performance.

The correct length is roughly just short of 40 cm (quarter wavelength at 800Mhz), at 80 cm (double length) it will actually end up with virtually no signal. This is a bit theoretical and not totally true in practice because there is no "proper" ground plane.

Going further in theory, at 120cm it only works as well as 40cm because 80cm of it will just cancel itself out.

You can get higher gain "rods" that are 5/8 or 7/8 wavelengths long but these need coils in them to shift the phase and stop the cancellation (getting even more techy)

So what should I do then?

I can get all the buts from maplin Liverpool if I need to build it differently ?

Should I just get a F type mains boosted arial instead?

Must be some small battery powered amplified aerials around somewhere (caravan aerials at Maplin?). Most of the mains ones will have a power supply which you could just replace with a battery.

Depends on how portable you want it, a small yagi aerial (even 3 elements) will normally out-perform rod type aerials, but I have seen some amplified twin rods do much better than I thought.

Don't know if you are in Storeton TV transmitter footprint or not, trying to get a decent signal from Winterhill on a portable aerial is a struggle for a lot of Wirral.

Don't get the horizontal loop aerials these don't have a lot of gain as they are designed not to be directional more than high performance, the more directional an aerial is, the higher the gain (just like narrowing a torch beam makes it brighter).

Its not clear in Maplins catalogue which are mains amplifiers and which aren't.

Difficult to tell which small aerials are just gimmicky designs and which are genuinely engineered. Best is to ask around and find somebody that uses one successfully.

When it comes to amplifiers, although saying it has 20dB gain (that is multiplying received power by 100) doesn't mean much if it doesn't have a low noise amplifier, because the noise gets amplified as well.

In other words - suck it and see, take it back if it is useless.

Thanks DD your a top bloke! I will keep you informed on the outcome

Might try these:

mains powered: http://www.maplin.co.uk/Module.aspx?ModuleNo=97986

battery powered: http://www.maplin.co.uk/Module.aspx?ModuleNo=25649

I will have to buy the correct connection for the battery one as it does not specifiy what connection it has

The very best indoor ariel available for Freeview reception, and this is fact not fiction, is http://www.amazon.co.uk/digiTop-Amp...lectronics&qid=1221891996&sr=1-1

If this does not get good reception, no other indoor ariel will give better, and your option will be an outdoor one.

In general, a booster won't do a particuarly great deal for a digital ariel as all they usually do is add noise to the signal (fine for analog, not so for digital).

Tar Matty, I will try out all options

Good find Matt, mixed reviews but obviously works for some. One of the reviewers mentioned the Technika TT-02 from Tesco's as working when that one didn't so might be worth a go.

Don't forget, if you are pointing at Storeton, that transmitter is vertical polarisation so need to turn horizontal aerials on their side. All the big transmitters are horizontal (Winterhill, Moel-y-Parc etc).

Yeah, I can't remember why I came across it (may well have been on the AV Forums), but it's been tested for digital-uk and there is an in-depth PDF report somewhere on the web, and it was found to be the very best indoor ariel. So I thought hmmm, ill bookmark that, may come in handy someday.

Ok been and got a few parts from Maplin today.

First of all I got a convertor to change the F type to a standard fitment.



Then the 2x AA powered Booster with flexible aerial.



Now my signals are pretty good
(TV)

(Radio)


However on the channel I get this

??? it has a good signal but says No signal? It works great when the quality % bar has even a low rate.

If I sit on my bed with it on my leg it works fine and displays all the channels in great quality. but in other places it displays nothing even tho a good signal is present?

why is that and how can I fix it?

You haven't got a VCR or other equipment with a modulator output in the vicinity.

I do have an old VCR under the stairs?

I meant switched on, and giving out a signal that may be blocking the digital signal.

Another possibility is that it is not uncommon for amplifiers to self-oscillate at some frequency as well, try moving the cables or putting aluminium foil round it and see if signal level changes (desperate thoughts!).

not sure if I done this correct lol



The signal is now very erratic

Yeah, it might not like the aerial being so close to the pre-amp, if the aerial picks up any RF leakage from the output then its the same sort of effect as sound with microphones and speakers, loads of feedback (or self-oscillation for a better term).

If the tin-foil makes any significant difference then its a fair indicator that something untoward was happening.

No saying whether a cable between the aerial and amp would help or not, just to give it some distance - if you've got one handy, give it a go, I wouldn't risk buying one just to find out though.

You probably need more aerial, the amplifier can't amplify something that's not really there to start with. Helix aerials are only about the same effectiveness as a quarter wave rod, the advantage is that they are shorter not better performing.

A possible analogy is looking at something through a mist, using a magnifying glass whilst making it bigger, doesn't make it clearer, but if you use three separate cameras in parallel and amalgamate the 3 pictures it becomes clearer.

Have you tried a cheapo set-top TV aerial like they sometimes have in Poundland? They are directional and might make a difference.