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RShiner
Posted: Mon May 23, 2005 11:24 am Reply with quote
Joined: 11 May 2005 Posts: 6
I just got my new Toppy and scanned for channels to find it will only get mux 1 & B!

Before buying I borrowed a Bush DFTA3 to check I would get a good signal and found I got everthing just fine except mux A that was a bit patchy which I didn't mind. The signal levels, below, don't look too bad to me but can anyone tell me whats is the minimum level required. I can't believe that the toppy can't find a signal that a cheap Bush box can!

Mux 1 Signal 71% Quality 97%
Mux 2 Signal 70% Quality 80%
Mux A Signal 67% Quality 60%
Mux B Signal 68% Quality 95%
Mux C Signal 67% Quality 67%
Mux D Signal 61% Quality 80%

Has anyone else found the toppy tuners to be so weak?

Just to fill in a bit more detail I have a 13-15dB aerial, can't get close enough to get the exact details, with a 24dB masthead Amp pointing at Sutton Coldfield, 50 Miles away! Ridge Hill is my closest transmitter but I can't get a signal from it because of a large hill in the way. This was the setup used to test the Bush, and provided good analogue signals too. I added an old Maxview SB2 booster splitter to feed the toppy and still only got Mux 1 & B, the quality is perfect! without the splitter the signal and quality drop and the picture becomes patchy.

Any help or advice would be good. I don't to return the toppy but If the opinion is that even with a bigger aerial I won't get a good enough signal I will have no choice!

Thanks,
Roland
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malc
Posted: Mon May 23, 2005 1:38 pm Reply with quote
Frequent contributor Joined: 08 May 2005 Posts: 1380
Try this signal predictor and see what it gives you. For me it predicts 29dBuV field.

I've just replaced my aerial with a Treves DAT75, plus MRD (intergral amp). Cable run to TV is satellite cable. I get 75% signal, 99% quality on my toppy. Sky travel channel is 99% signal strength. The PSU for the MRD comes out with 2 feeds which nicely matches the toppy's needs.

I tried a friend's freeview box with my old aerial (18 or 21 element AFAIR, singal, not a triple like the DAT75). Feed was standard coax. I couldn't get all channels on that box, hence the aerial upgrade. And if you going to upgrade go for the best is my view. Very Happy
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RShiner
Posted: Mon May 23, 2005 2:24 pm Reply with quote
Joined: 11 May 2005 Posts: 6
It gives me 7dBuV Shocked Not good!

I'm not sure that even a Dat 45 or 75 with MRD will get get that figure high enough will it? From what I've found the toppy needs 20 - 30dBuV minimum.

I think I may have to stick to a Bush box. Crying or Very sad
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malc
Posted: Mon May 23, 2005 7:10 pm Reply with quote
Frequent contributor Joined: 08 May 2005 Posts: 1380
Don't get confused between the predictor values and toppy input levels. The predictor is dBuV/m (I missed /m on my figure, should have been 29dBuV/m). That is the field at the aerial.

According to Google, the input level formula is:

Vr = FS + Gant - N/10 - 18

Vr is the received signal voltage (pd) into a matched 75 ohm load in
dBuV,
FS is the signal field strength in dBuV/m,
Gant is the antenna gain in dB relative to a half-wave dipole (dBd),
N is the (European) TV channel no. (21<N<69).

For me, Fs=29dBuV/m, Gant=19+13 (DAT75 + MRD), N=65 (Highest channel), this gives 36.5dBuV

I thought I was fringe at 29dBuV. Freeview vs postcode lookup on the freeview site says I can't get freeview. Does it say the same for you?
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RShiner
Posted: Mon May 23, 2005 7:55 pm Reply with quote
Joined: 11 May 2005 Posts: 6
Yes the freeview site says I can't get any reception but it also assumes that my aerial is pointing at Ridge Hill.

I'm not to good with Aerial and deciBels but I think I understand what your saying.

Using your formula I get:
FS = 7
Gant = 40 =15 (Aerial) + 25 (Masthead Amp)
N = 5.5 = 55 / 10

VR = 23.5 dBuV

I'm not sure how the splitter fits into this as it doesn't have any spec on it but I guess it may be up to 10dB. Would I also have to deduct something as the signal is split? It would appear that a max VR would be 33.5 dBuV

What I don't understand here is that my aerial + amp seem to have a higher power output than your DAT75 + MRD. Have I misunderstood this or would I get less signal strength if I had the same system as you?

Thanks again,
Roland
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malc
Posted: Tue May 24, 2005 12:39 am Reply with quote
Frequent contributor Joined: 08 May 2005 Posts: 1380
Passive splitters drop 12dB if resistive about 9dB if they have a transformer. An ideally splitter has to drop 6dB in volts, which is 3dB in power, since it shares the power between two inputs.

But you say the splitter is a booster so I assumed it's powered. In which case it probably has gain too.

In general the bigger the aerial the better. You can't keep amplifying the signal as you're just adding more noise. A bigger aerial will give you a higher signal to noise ratio (SNR) to start with. Amplify that and the signal goes up but so does the noise, plus the amplifier adds some noise too.

I would have thought, all things being equal, that you could compensate for the lower threshold of the toppy by more amplification. Assuming of course that the toppy and bush have similar SNR requirements. That is, bush's 60% quaility is the same SNR as toppy's 60%.

It can't hurt to have a better aerial. Whether it is enough I don't know. The DAT75 is best you can get AFAIK. And of course you'd want to use good satellite cable, not TV coax, for the aerial downlead. I take it that your current aerial is a single and not a triple like the DAT?

Looking at the Bush figures I wonder if they don't show a low SNR. I get 75% signal and 99% quaility. I seem to remember when setting it up that the quaility was still high even when the signal dropped (as the aerial was turned). You seem to have much lower quaility figures suggesting a lower SNR. But then, given your low field that is to be expected.
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RShiner
Posted: Tue May 24, 2005 9:50 am Reply with quote
Joined: 11 May 2005 Posts: 6
I think the real problem here is as you suggest that even though my signal level is ok because I have to amplify the signal so much to get it the signal quality just isn't good enough. The toppy seems to need a signal quality of about 95%+ and I don't think any amount of further amplification will produce this. I asked a local aerial fitter if he thought a DAT75 would provide the extra quality needed and he felt it unlikely considering I have such a low signal level to start with. He has come across other freeview boxes in the past that also needed a very high quality signal and said the best option is to find another one that isn't so fussy!

Looks like I'll have to give up digital dream for now! Unless I can find another PVR I like that would work with my signal. Roll on 2010!

Thanks for your help malc.

Roland.
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malc
Posted: Tue May 24, 2005 12:23 pm Reply with quote
Frequent contributor Joined: 08 May 2005 Posts: 1380
I think I'd agree with the fitter. You're starting from a very low level. The predictor said I could get freeview with a good aerial. I'd tested it with my old aerial (not with a toppy though). So for me it seemed a good risk to go for a better aerial.

Seems that your only current option would satellite and rip-off $ky Sad . Typically UK has non standard satellite allowing a rip-off monoploy.
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RShiner
Posted: Tue May 24, 2005 1:50 pm Reply with quote
Joined: 11 May 2005 Posts: 6
I used to have sky but canceled it a few years ago, I just got fed up with the same old rubbish! I used the sky box for the free channels until recently when the processor finally over cooked, a common problem with the Panasonic DSB30! Maybe I'll get it fixed or as I said before just get another cheap Bush freeview box! I never thought I'd be praising with a Bush badge on it!
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malc
Posted: Tue May 24, 2005 4:38 pm Reply with quote
Frequent contributor Joined: 08 May 2005 Posts: 1380
I used to have $ky too. Got fed up with high cost low quality, plus I found out about these unlimited DVD offers. Cheaper than sky, better quality, more choice, in fact there isn't a down side. When I cancelled even the bloke at $ky admitted he was on this too Wink

I was thinking that toppy do satellite PVRs, but of course not $ky or the free channels. Or perhaps that has changed? BBC has gone free to air so I think any digital receiver can pick that up now. ITV is still free to view I think i.e. you need a $ky card and $ky box.

Of course your bush box is one answer but it's not a PVR. There are more PVRs in the pipe-line (I think bush are bringing one out) so perhaps wait and see is the best course.
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RShiner
Posted: Tue May 24, 2005 5:03 pm Reply with quote
Joined: 11 May 2005 Posts: 6
I've seen new 'no contract' sky boxes for about 100+ and a freesat card, for BBC 1,2,3,4 etc and ITV, C4 & Five, is about 25. But the problem is with the free channels on sky that other than the main channels there is nothing worth having, it's all shopping and text in quiz stuff. I really wanted freeview because it has E4, soon, and even Men & Motors looks like it would have the odd car or bike program I'd enjoy and later in the year More4 sounds like it could be good.

I think I'll have to look at other PVR's and see of they would work. The Inverto might be ok but it doesn't have the extra features I want that the toppy does! As you say there are supposed to be more PVR's in the next few months so maybe I'll find something there. But I bet I won't be able to code TAPS for it though. I was looking forward to that. I think I'll have to go snooping on digital spy and see what I can find out.
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Darkmatter
Posted: Wed May 25, 2005 12:30 am Reply with quote
Forum moderator Joined: 21 Mar 2005 Posts: 1237
If you do decide to keep your aerial, keep an eye on Mux D ? it?s slightly out-of band for an old analogue aerial of the type recommended for your area. From your list, Mux D has the lowest signal strength, yet it?s transmitted from Sutton Colefield at a higher power than any of the other mux?s.

It?s always difficult to advise someone is planning on an aerial upgrade, malc seems to have covered all the bases, focus on picking up as much of the signal as possible, and minimise the losses on the way down to the TV set ? big aerial, good quality cable, appropriate amplification. It may be worth your while posting on Radio and Telly forum. Although, you?ll probably get the same response ? for a weak signal area, with minimal stray RF, the DAT series aerials complete with MRD are well though of.
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shetenyi
Posted: Wed May 25, 2005 9:19 am Reply with quote
Joined: 13 May 2005 Posts: 10 Location: Gloucestershire
I spent a frustrating evening with my new toppy grappling with a weak signal. Took some advice, bought some good quality cable and a splittter rewired from the ariel right back to the toppy. Problem solved.
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