Channel 5 signal quality

[chicky]

ok cheers...I'll try a few things this weekend and see if it makes any difference.

Can you recommend a better amp, by the way...both masthead and standard ariel amp if you don't mind.

 

[spiney]

Hang on a bit ......

The most important bit is the aerial. If you're having problems, that's the bit that should be replaced!

Masthead amps in no way "improve" the signal! What they're supposed to do is compensate for cable losses. If you fit one, then it should go on the aerial mast, in which case - since going onto the roof - you might as well just upgrade the aerial instead!

Masthead amps can be useful for digital tv, if you want to avoid a "too big" aerial on the roof (eg, dat75), but it's much better to get a better aerial.

See: http://www.megalithia.com/elect/tinkercurse.html .

Note that, for digital tv reception, the connecting cable is just as important as the aerial, replacing older "UHF only" coax with newer satellite grade will make a difference, independently of any aerial change.

 

[chicky]

Hi Spiney....I get your point.

It's just that rolfw said the amp I'm using isn't much cop so I thought it might be at least worth considering replacing it with a better one if the cost wasn't too much.....save me from splashing out on a new ariel. I was weighing up £20 (new amp) v £100+ (new ariel - fitted by a pro) - that's all. If a new amp didn't do the job then it was only £20 wasted - I just thought it was worth a go.

I do understand what you're saying and appreciate the help (and rolfw too). I'm going to switch to the better ariel this weekend and see if that changes things.

C

 

[spiney]

The thing to do is look at the error rate reading. I'm not familiar with your pc card, but fairly damn sure it must have this facility!

see: http://www.megalithia.com/elect/aerialsite/dttpoorman.html .

 

[chicky]

Actually I tried to see if I could find out the signal strength and quality last night and I must say the software was a bit lacking.

I couldn't find any signal check utility with MediaPortal but the shipped Hauppauge software did give an overall signal strength reading for the card (rather than for each channel) and it came in at about 40-45% (that's a guess as it was a gauge reading). I certainly wasn't a high signal.
I didn't even see a reading for signal quality or error rate so I really don't know - unless there's some software out there that can measure this.

 

[rolfw]

I've recommended putting a masthead amp on the downlead of the good aerial (not the bad one), the one that does receive all of the multiplexes well. It doesn't need to go on the mast, although the closer the better, but I have used them to great effect four or five metres from the mast to facilitate a split to two or more locations.

The digital signal is not as fragile as was originally suggested and below threshold signals from an aerial can be quite effectively amplified to above threshold levels, without the predicted very high bit error rates.

Yes, of course a new high gain aerial is the best solution, but even that may still need amplification when it is required to feed more than one outlet, so trying a masthead and splitter on the good aerial is a lower cost alternative.

 

[spiney]

Yes, Rolf, completely agreed, but that's not what I said !

1) An amplifier will always increase the ber. There are no exceptions.

2) If you're splitting the cable, then that's effectively the same as cable losses over a long distance, in which case a masthead amp may well help (with cable losses, a lower signal level goes into the receiver, so a worse snr comes from that, which is why a low noise masthead amp helps, as you know of course, but many people won't!).

3) If possible, a better aerial is always preferable, since, whatever signal you get from it, that's the best you can possibly have, there's no way of "improving" it!

OK, I'm not trying to be awkward (honest!), but I believe it's important that the principles are well understood, otherwise it becomes "fiddling about".

(added) For anyone that's still interested in what Rolf and I are "arguing" about - and not bored silly by this discussion! - then here's a Cisco guide to the general principles, specifically in cable systems, but these principles are universal:
http://www.cisco.com/en/US/products/hw/cable/ps2209/products_white_paper0900aecd800fc94c.shtml .
Note particularly the formula for cascaded amplifiers, which shows why the 1st amp in any "chain" - here, the masthead one - must have the lowest noise figure, and be as near as possible to the signal source.

 

[Saturlight]

Channel 5 started over ten years ago, and yet it's still a snowy analogue picture in Newcastle, the north east.

I think they have abandoned the idea of improving the signal, as it's all going digital anyway, with S88 and Freeview. ;)

 

[spiney]

Yes!

Ch 5 analogue didn't fit into the existing UK tv frequencies plan, so had to be "squeezed in somehow", in addtition to all that VCR re-tuning (remember that?).

Which meant, sometimes the signal was weaker anyway, and the signal might be out-of-band of existing aerials.

Note that, there's no direct connection between this and the digital version reception, 2 entirely different things!

Sorry if I seem to be aurguing with Rolf, when what you really want is practical advice.

Anyway, enjoy This Island Earth!