Masthead amplifier confirmation

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kingzzz69

24 posts

Geek

#83350 14-May-2011 17:59

Hi, just confirming I'm in need of a masthead amplifier. Currently have a gizmo aerial with the UHF gain kit. Can get dvb-t freeview fine with no splitter. 2-way splitter is %95 fine with the odd pixelation in one of the rooms (probably due to a longer cable run). Wanting to split more (6way) and have no signal after that.

I need an amplifier right? if so, 25db enough? or go for the next one up. Was looking at getting one of these. Any recommendations on better amplifiers?

Thanks

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481 posts

Ultimate Geek

#469123 14-May-2011 18:21

kingzzz69: Can get dvb-t freeview fine with no splitter. 2-way splitter is %95 fine with the odd pixelation in one of the rooms (probably due to a longer cable run). Wanting to split more (6way) and have no signal after that.

It certainly sounds like a good quality amplifier would help, however ...

kingzzz69: Currently have a gizmo aerial with the UHF gain kit.

I'm not familiar with the Gizmo aerial, but "with the UHF gain kit" makes me wonder if you could get a higher gain UHF aerial to start off. Its always a good idea to get the best signal possible from your aerial first, and then amplify that if necessary.

Again I'm not familiar with Johansson amplifiers. I use a Kingray which I'm very happy with, and Kingray amplifiers do have a good reputation.

EDIT TO ADD:
The approximate loss when splitting a signal is 2 way = 4db, 4 way = 8dB, 6 way = 10dB, 8 way = 12dB.
Of course longer cable runs introduce some further losses, but not nearly as significant, so the splitter loss should help determine what power amplifier is required.

There is some useful information on splitters, amplifiers and aerials on this website.

illicit

553 posts

Ultimate Geek

#469125 14-May-2011 18:23

I'd recommend this

kingzzz69

24 posts

Geek

#469127 14-May-2011 18:44

Deev8: I'm not familiar with the Gizmo aerial, but "with the UHF gain kit" makes me wonder if you could get a higher gain UHF aerial to start off. Its always a good idea to get the best signal possible from your aerial first, and then amplify that if necessary

Thanks for the info, Yea the aerial is not the best, I think maybe 10db gain total (UHF) with the gain kit. We have other analog tvs in the house so still need normal VHF signals too.

kingzzz69

24 posts

Geek

#469128 14-May-2011 18:49

Hmm another option, could get a UHF aerial only and attach it to the same pole and use one of those 2 into 1 combiner things.

webwat

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#469187 15-May-2011 00:56

Your splitter might specify its insertion loss, but I imagine between 9dB-11dB. Add to that the attenuation of your longest coax cable and any other devices you have in the system, and thats how much power you need to boost the signal by (since your aerial seems to pick up enough signal for 1 TV). I guess 20dB to 24dB like this might be plenty, unless you have really long distances.

Time to find a new industry!

Deev8

481 posts

Ultimate Geek

#469300 15-May-2011 14:56

At UHF TV frequencies cable losses for decent quality RG6 cable should be a little less than 2dB per 10m. Add in 10dB for your 6-way splitter, and some additional loss for all the connectors between aerial and TV, and a 24dB amp should be plenty powerful enough.

Do yourself a favour and use F Connectors for everything but the actual connection to the TVs, and do look into getting a better aerial to improve your signal to noise ratio.

cldlr76

289 posts

Ultimate Geek

#469718 16-May-2011 15:51

Do the signal strength and quality numbers give any indication of your ability to split. I'm about to split mine. I've got a signal feed going to my Sony TV that shows strength as 100 and Quality as 56 and I'm hoping to eventually split it 4 ways.

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richms

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#469725 16-May-2011 15:59

Masthead amplifiers are not made for driving many TVs, they have a lower total power output than you need to split many ways, they are made to bring a low level signal up to be able to drive down a cable, and are generally used only when you have exhaused all the options for putting a decent antenna in.

The gizmo is about as far from a decent antenna as you can get without resorting to a coathanger.

You want a distribution amplifier that you put inside and can output over 110dB - most mastheads struggle to get near that without massive distortion which will kill the digital signals and make diagonal lines appear over the analog stuff.

IMO, sort your antenna out with the biggest that you can fit, then see if you need an amp. They generally only make things worse unless you can get it filtered etc. I had to get an overpriced diplexer here to stop all the RT stuff getting in via the antenna and causing digitals to pixleate and the analogs to get swirly patterns over them. Single TV and no amp was fine.

Also if the cables are genuinly long, you may want to get an amp with gain compensation in it. There are external things that do it as well but they only attenuate. One of those and a second amp sorted out the problems with all the upper UHF;s looking like crap in the garage which is on the end of about 25m of cheap nasty coax.

Richard rich.ms

Brunzy

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#469783 16-May-2011 17:43

richms: Masthead amplifiers are not made for driving many TVs, they have a lower total power output than you need to split many ways, they are made to bring a low level signal up to be able to drive down a cable, and are generally used only when you have exhaused all the options for putting a decent antenna in.

The gizmo is about as far from a decent antenna as you can get without resorting to a coathanger.

You want a distribution amplifier that you put inside and can output over 110dB - most mastheads struggle to get near that without massive distortion which will kill the digital signals and make diagonal lines appear over the analog stuff.

IMO, sort your antenna out with the biggest that you can fit, then see if you need an amp. They generally only make things worse unless you can get it filtered etc. I had to get an overpriced diplexer here to stop all the RT stuff getting in via the antenna and causing digitals to pixleate and the analogs to get swirly patterns over them. Single TV and no amp was fine.

Also if the cables are genuinly long, you may want to get an amp with gain compensation in it. There are external things that do it as well but they only attenuate. One of those and a second amp sorted out the problems with all the upper UHF;s looking like crap in the garage which is on the end of about 25m of cheap nasty coax.

+1
But also, if you dont know the S&Q readings
you are"*rinating in the breeze"

kingzzz69

24 posts

Geek

#469933 17-May-2011 04:23

something like this would be ok? http://www.trademe.co.nz/Electronics-photography/TVs/Cables-aerials/auction-376766264.htm

plus this http://www.trademe.co.nz/Electronics-photography/TVs/Cables-aerials/auction-376359698.htm

to combine it with my current antenna so can still get analog stuff

richms

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#470107 17-May-2011 14:10

Yeah, to be honest any money you are spending on combining the antenna would be better off put towards a digital box tho, since its so much better and switchoff is getting close.

Richard rich.ms

Deev8

481 posts

Ultimate Geek

#470172 17-May-2011 17:00

richms: You want a distribution amplifier that you put inside and can output over 110dB - most mastheads struggle to get near that without massive distortion which will kill the digital signals and make diagonal lines appear over the analog stuff.

I really think that 110dB amplification would be over the top for someone who is happy they have an adequate signal when their aerial is connected directly to a TV, but now wants to split that signal 6 ways!

richms

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#470175 17-May-2011 17:08

Not amplification, the max output level. That is really low on the cheap amps and then they overload and end up with crap allover the top of other crap, so when you autotune you get about 6 versions of each channel on various places and them all ontop of eachother etc..

Richard rich.ms

webwat

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#470285 17-May-2011 21:47

richms: Not amplification, the max output level. That is really low on the cheap amps and then they overload and end up with crap allover the top of other crap, so when you autotune you get about 6 versions of each channel on various places and them all ontop of eachother etc..

So output power is measured in dBm, whereas the relative loss/gain of each component is dB, but awkward to measure signal strength at the amplifier without tools anyway. We know one link is ok without a splitter, so the amp must compensate for 10dB loss of inserting the splitter plus any longer cables. End result should be the same if you get that good aerial.

Time to find a new industry!

richms

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#470288 17-May-2011 21:50

I always get the dBm and dBuV mixed up, too many measurements.

Richard rich.ms

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