Aerial signal and multiple (digital) cards

[wannabepvr]

Had a hard day yesterday. Thought I would add a second tuner to my system to make life easier - Not likely! After many hours I finally worked out the problem.

I now seem have too many devices attached to my aerial and the resulting signal seems to be dropping below some magic threshold on the digital tuners. The result for the record is: jerky image - MPEG artefacts and audio drop out.

I guess I shouldn't be surprised there are 3 TVs, a VCR, 3 tuners, and a STB on the line. All want a share of the signal strength.

You are generally not recommended to add amplifiers or boosters for digital reception. So how does everyone else attach multiple tuners to the one aerial. Spitters, custom short cables, shielding, etc..

Has anyone else had problems?

Who said "you can never have too many tuners"

[herbs]

My aerial feeds 7 items, 5 of them are digital. I split the signal two ways then add boosters to the splits. 1 booster feeds 3 digital cards, and 1 analogue. The other booster feeds a digital set top box, digital card and a analogue card. I don't have signal problems, although I do get break up occassionaly on the pc's due to noise from inside the pc.

[dazzyb2k3]

My main aerial is already split three times before it comes downstairs into the PVR, at this point I then run it into a 6 way gold distribution splitter from these guys:

http://www.philexproducts.com/aerials_bo...ables.html

This supplies the signal to my 5 X DVB tuners and the TV without any problem. I've been carefull to use high quality double screened cables. You shouldn't have a problem using a booster/splitter so long as you have a good quality (allbeit weak) signal. The problems arise when you try to amplify a 'dirty' signal.

Some DVB cards also require a much stronger signal than others. I once had real problems when using a Nebula card in a multi tuner setup. The card worked fine on it's own but soon as you split the signal it gave me no end of stuttering and hiccups. You should get yourself an amp and see how it goes, they're fairly inexpensive and it might just do the trick!

[wannabepvr]

Thanks guys.

I didn't really realise how little signal I had left until I though about all the splits.

[djtaylor]

There isn't a problem amplifying as long as you do it right!

The correct way is to put a distribution amp at the aerial or near to.

I have a low noise 4 way masthead amp (but in the loft because that was easier to do). It has a 10dB output gain on each and that takes 50m before you're back to the original signal level.

On this basis, that means that if your typical run is 25m then you *should* in fact split in order to get back to the same signal level as the aerial is receiving. Thus the 4 way amp, with each leg driving a 25m length actually drives 8 tuners.

The wrong way to do it, is to take a long aerial downlead, feed it into a plug in amp, then run off that. You should always amplify to overcome the cable loss, not try to amplify it at the other end as then you amplify noise.

David.

[djtaylor]

Thanks guys.

I didn't really realise how little signal I had left until I though about all the splits.

Every time you passively split two ways, you reduce the signal by 3dB, that's half.

David.

[Cyb]

As well as amplifying at the source as djtaylor mentions above the other thing that made a difference for me is replacing downleads with decent quality co-ax, CT100 standard here in the UK.

This article has examples of different cable types and the relative losses for each.

[wannabepvr]

Thanks all.

Took a simple approch and put in a booster-splitter. Instantly everything worked.

My set top box has a signal strength bar and this jumped from ~60% to ~95%!

This multiple tuner thing is great! Hopefully no more missing the end of one show to record the next on another channel.