TV reception not very good and channels not tuning in?

[carlsbergy]

Hi all,

I have recently replaced my TV aerial which snapped from old age with a 48 element wide band TV aerial. I used a LABGEAR DVB signal finder and found the lights will not go past 50 (first LED), which I did not find improved the picture as I originally put the aerial up with out the signal finder! aerial is pointing in same direction as other house aerials. The Mast aerial then goes into a TV booster (in the loft) and then to 4 x separate TV around the house.

The problem I have is that channel 4 has ghosting, on a freeview TV set not all the programs tune in, and some freeze for a second sometimes and then resume to normal. The TV set the furthest away from the booster has a worse picture.

Any help would be appreciated.

Thanks

 

[ericmark]

Forget how many elements what's the DB gain? Aerials were banded and as such had a fair bit of gain for relative short aerial. The broad band aerial is however not very good at either bringing in distance signals or rejecting un-wanted signals. All they do is present a good surface area to wind and demonstrate how good their harmonics are as they vibrate.

A 12 element band B has 12.7db gain 48 element Wide band has 11.5 to 15db gain so in real terms it is only as good as old 12 element type. And it is 1/3 longer then old type.

Much depends on location but in many areas there is no longer any need for wide band aerials now we have lost analogue and we can go back to cheaper shorter aerials of yesteryear.

Mast head amps do work well. That may be cheapest option. Rubbish in give rubbish out so amps with lengths of coax between them and aerial are never as good as those right by aerial.

 

[carlsbergy]

Thanks ericmark, I have that aerial you have the link to from TLC, Can you suggest a mast head amp? or am I better off replacing the aerial for a different type?

 

[ChrisFrost]

Have a look at this

 

[ericmark]

There are 100's of aerials main thing is look at db gain. I have made many aerials and all are a trade off in some way or another. Met one guy who had 9 x 14 foot yagi beams all linked together with a rotator with azimuth as well as direction and he bounced VHF signals off the moon to USA. But the frequency used was very tight and to use multi-aerials like this for TV with such a wide band is near impossible.

For TV I just used a cheap aerial and routed cable into loft where it is then amplified before it is sent to main TV. Here video and sky channels are added and it then returns to loft. Through another amplifier and then to three bedrooms kitchen and dinning room. It works well.

But I am sure if I moved house I would end up with something different. For transmitting I use a HB9CV (Call sign of guy who designed it) and this has just two elements but both are driven and it does as well as many 8 yagi element beams.

The article refers to the log-periodic again more driven elements but I have no idea as to patten or gain and as well as trying to amplify incoming signal you are also trying to attenuate unwanted signals and some aerials have a lot better rejection than others.

So just because it works well on one house does not mean it will work well on another. So I am loathed to recommend any aerial as it is so dependent on local conditions.

One can get surprising results moving an aerial just a few feet and not always up.

Over the years I have really had some fun. Made aerials from 300 ohm ribbon cable and celotaped to window. I sent messages all over Hong Kong with that. I was in 23rd of 32 floors in block of flats. However on the house most people don't like going up and down a ladder and altering their aerial. First I would look at where it is mounted and see what may be in the way. Trees. Power lines etc. I would try moving it to different place. Likely try loft as easy to get to. Plus amplifier. But it is unlikely a new aerial will improve things. Most areas 12db is enough. Could be water in coax. Or poor quality coax.

You have a meter have you tried at aerial and TV and seen how much you have lost? What cable have you used. I only use Sky cable or better.

 

[ChrisFrost]

Get the right aerial for your transmitter area and surrounding conditions. What band do you need. Are you on a main transmitter or a repeater. How close is the transmitter. Has your area switched to digital yet. Do you live in a built up area or with trees causing reflections.

Once you have the right aerial, and its polarised correctly and aligned properly then you can deal with any band filtering (if needed) and the signal level if it needs modifying. Just remember, too much signal can be as bad as not enough.

 

[ericmark]

Unless you lived right under the transmitter I would think it would be very hard to get over driving of front end of modern TV set.

I did look on my TV instructions to see max signal and nothing is stated neither is the minimum although I know when the digi-box was replaced by the digital TV we were able to receive freeview much better. Since we used Sky I have never changed aerial for main TV.

On analogue there was no indication on TV as to signal strength but with digital in tuning menu it allows one to monitor signal strength and quality with two bar graphs for each channel.

Most of the channels on my TV show around 3/4 full or more on both but S4/C which comes in on side of aerial shows red and about 1/8 of way across but still works fine.

Had not considered this until "ChrisFrost"'s post but of course looking on TV would be best option. If strength is OK for signal is poor then one is looking for interference and an aerial with some rejection may be required but if strength is down then booster or bigger aerial is required or the feed wires are damaged or not good enough quality.

Digital signals are weaker than analogue and so any losses in coax will have more effect.

Since change over signal strength here is much improved. However they have swapped channel numbers that many times it had become silly and I stopped watching terrestrial TV. It has one program only that I watch. "Yesterday" was called "UK History" it needs paying for with extra package on Sky but free on freeview so is only channel I ever use freeview to watch. And it is only on during the day switches off in evening. So don't think I would go to any lengths to repair anything needed for freeview.

 

[carlsbergy]

Thanks guys, will start with aerial