Too Much Signal?

[energysolutions]

Hi,

I have installed a DVR and some cameras which work fine, I also have added a modulator which feeds into the TV distribution system to enable the occupants to quickly check for visitors from the comfort of their sofa via the TV system

The aerial is routed through the modulator and continues on the rear of the Sky box, where it can be viewed on the screen of the TV in that room

The combined signals (Sky, Regular TV via the aerial and CCTV) are then sent back up to the distribution equipment and fed around the house - It is after the distribution equipment that the fun starts

The picture is poor with lots of ghosting. I believe this is due to too much signal caused by the 10dB gain that the amplifiers add, question is how do I counteract this without upsetting the TV pictures?

I am currently using this modulator which has no gain adjustment:

http://cgi.ebay.co.uk/RF-MODULATOR-SCART-O...p3286.m20.l1116

Would I be better using this modulator with adjustable gain?

http://cgi.ebay.co.uk/RF-Modulator-CCTV-DV...id=p3286.c0.m14

Or is there another product/method I should be looking at to cure my woes?

Thanks in advance!

[Guest anguscanplay]

what channel have you got the mod set too?

[energysolutions]

what channel have you got the mod set too?

I have tried various different channels, (21,22,29,37,44,48,57,69) and while some have an impact on the quality pre amplifier, (at the main TV) all have been plagued with ghosting after the signal has passed through the amplifier to the rest of the TVs

Thats why I reckon a modulator with gain adjustment may be worth a shot, I hope to be able to reduce gain and in turn reduce ghosting on the pictures at the amplified TVs

Any thoughts?

[Guest anguscanplay]

I have tried various different channels, (21,22,29,37,44,48,57,69)

Any thoughts?

dont they all have broadcasts on those channels - remember you need to be one plus clear of other stations - have you had a perfect signal just connected locally?

[Barsnake]

Some of you may find this page helpfull

http://www.dtg.org.uk/retailer/tx_m.html

[Doktor Jon]

RF was never my forte, but I would imagine if the problem sits with an excess of signal, then perhaps a simple plug in attenuator or preferably a step adjustable attenuator, would help to reduce the problem down to a manageable level

Just a thought ....

[Guest anguscanplay]

its more likely not enough signal than too much

what are you using to boost the signal from the TV to the dist.?

[energysolutions]

its more likely not enough signal than too much

what are you using to boost the signal from the TV to the dist.?

If I test the picture as it enters the Modulator it is fine, it is also fine when it reaches the main TV (pre amplification, where the Skybox etc is located), the signal (along with Sky and regular TV is then returned to feed the distribution equipment via "RF2" on the back of the sky box - after it has passed through the distribution equipment (which has 8dB of gain added) the picture is ghosting at any of the other TV locations in the property

The booster/distribution amp (existing) is:

http://www.tracsat.co.uk/catalog/aerial-amplifier-p-289.html

Thoughts please............................

RF was never my forte, but I would imagine if the problem sits with an excess of signal, then perhaps a simple plug in attenuator or preferably a step adjustable attenuator, would help to reduce the problem down to a manageable level

Just a thought ....

Hmmm, This sounds like it may be the answer

Does anyone know which model/type would be best suited?

Would this be fitted inline with the aerial (worried about doing that in case it interferes with TV pictures) or inline with the CCTV feed (is this possible)?

dont they all have broadcasts on those channels - remember you need to be one plus clear of other stations - have you had a perfect signal just connected locally?

Yes - Picture at Main TV (pre distribution) is pretty good

[arfur mo]

Yes - Picture at Main TV (pre distribution) is pretty good

my experience is if you reduced the signal this often indicated by ghosting, loss of co;our resulting in a pasty image. where if too much signal is present which overdrives the inTv input, images which will be very contrasted and bleached out but also ghosted.

as all is well until you place the modulator in-line then i'd assume the problem being the modulator is supplying to much or to little signal, so a coup;e of possibles for you -:

1) the aerial system may be the active type with a built in mast head amp combined within the distributor, if you insert modulator directly from the aerial before the upper bit of the samp this may overcome it as if you get between the mast head and the distributor this cause's big problems

2) the modulator unit may have an internal link which act's as a 'load' resistor, i have used one make where they have this in place by default, but with no documentation on it .

if so the existing distributor is the 'load' so having that resistor in place on the modulaor efectively doubles the load

tbh your often better off fitting a 'V combiner' (SystemQ, Maplins, RS), where the the original signal is fed into one side of a 'V' and the aerial into the other. then if the modulator dies in a thunderstorm it don't kill all the Tv in the home .

regs

Alan

[Guest anguscanplay]

if so the existing distributor is the 'load' so having that resistor in place on the modulaor efectively doubles the load

tbh your often better off fitting a 'V combiner' (SystemQ, Maplins, RS), where the the original signal is fed into one side of a 'V' and the aerial into the other. then if the modulator dies in a thunderstorm it don't kill all the Tv in the home .

regs

Alan

that was going to be my next question - what are you using to COMBINE the signal, not one of the crappy V adapters surely LOL, all they do is block the supply and stop the mast head amp. from working, leaves you with virtually no signal once its gone through two more boxes and back upto the loft which then gets amplified and causes ghosting

everytime we have done this its had to be

arial - masthead amplifier - modulator - combiner - sky box - amplifier - dist

the RF2 signal out of the sky box isnt the most powerful thing in the world, so theres nothing lost by boosting the signal on its way to the loft