Power levels too high?
 

I have just had a powered booster fitted by a VM engineer to solve a TV problem and I think it has made my signal strength too high. Anyone care to comment.

Downstream Channels
Lock Status Channel ID Frequency Modulation Rx Power SNR Pre RS Errors Post RS Errors
Locked 42 307000000 Hz QAM256 8.5 dBmV 33.6 dB 491 0
Locked 40 291000000 Hz QAM256 9.2 dBmV 32.5 dB 4498 0
Locked 41 299000000 Hz QAM256 9.1 dBmV 33.2 dB 1028 0
Locked 43 315000000 Hz QAM256 8.3 dBmV 33.3 dB 852 0
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Upstream Channels
Lock Status Channel ID Frequency Modulation Tx Power Mode Channel Bandwidth Symbol Rate
Locked 2 27400000 Hz ATDMA 35.5 dBmV 16QAM 6400000 20480 Kbits/sec
Unlocked 0 0 Hz Unknown 0.0 dBmV Unknown Unknown 0 Kbits/sec
Unlocked 0 0 Hz Unknown 0.0 dBmV Unknown Unknown 0 Kbits/sec
Unlocked 0 0 Hz Unknown 0.0 dBmV Unknown Unknown 0 Kbits/sec

Re: Power levels too high?
 

Do you now your levels beforehand? This could be important?

What internet effects are you experiencing?

What you have now is high power boosting noise as well as signal. The SNR should ideally be above 34.5 dB. I would be unhappy about this. Most people are in the 37-40 dB range and you are entitled to be too IMO.

You could get a 10dB forward path attenuator from eBay and see what that does. But the SNR is what also concerns me. If it was low before, then VM need to look into it (though they'll claim it's in spec); if SNR has dropped from before then something has induced noise since the HDU was fitted.

Let us know.

Re: Power levels too high?
 

Thanks for that.
I have not got a before reading unfortunately. But from memory they were roughly the same. As to effects the only thing that seems to have changed is my download speed. It seems to have dropped about 20 Mbs to around 80 Mbs

http://www.amazon.co.uk/Apple-Compon...6501227&sr=8-1 is this what you think I need?

Re: Power levels too high?
 

That's exactly what you need to bring the power level down to the ideal 0 dBmv.

BTW you can check your pre-HDU power level by disconnecting the HDU from the incoming line, attaching the SH to that incoming line (hopefully you have the old splitter) and doing the upstream/downstream measurements and sepeed tests again.

Of course you have to be sure that your speed tests are not being conducted at times when you could expect doffeent results.

Re: Power levels too high?
 

you dont need a hdu, your upstream is low and your downstream is high. if its a high frequency issue then a thicker drop cable should have been booked. the next tech will probably remove it

Re: Power levels too high?
 

I can't see it being a high frequency issue. The OP could tell us the distance from home to street cabinet as a further pointer to the HDU question. Remember it was his TV signal that needed boosting in the opinion of the attending engineer.

What's your take on the SNR, JB? I know it's at the low end of being in spec, bu his noise is beig amplified.

Re: Power levels too high?
 

the superhub is very generous with the snr, a vmng300 would show 30db

Re: Power levels too high?
 

So what to do about that? 30 dB is not good.

Re: Power levels too high?
 

another visit im afraid, snr is a horrible fault for a tech to get as we dont have proper tools to measure it. usually its a loose f or a network fault

Re: Power levels too high?
 

A loose F would likely yield low DS/high US power; not always but usually.

That visit needs to be by someone other than a regular field engineer because, as you say, SNR is a horrible fault. Much of it can be diagnosed from the centre, by Level 2 for example, the rest by a network engineer.

Re: Power levels too high?
 

I just spoke to VM after losing connection and they did something. I now get the following.

Locked 43 315000000 Hz QAM256 6.9 dBmV 41.9 dB 561 0
Locked 40 291000000 Hz QAM256 7.7 dBmV 42.0 dB 426 12
Locked 41 299000000 Hz QAM256 7.5 dBmV 42.4 dB 457 0
Locked 42 307000000 Hz QAM256 7.1 dBmV 42.1 dB 455 0
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown

Re: Power levels too high?
 

nice, still dont need the hdu

Re: Power levels too high?
 

Thanks. Still ordered one as a possible experiment.

Re: Power levels too high?
 

JB means the HDU that the engineer fitted to boost TV power.

VM didn't do anything except reboot your SH. It picked up a different primary downstream channel. I suspect the fall in power level is due to the external temperature rising.

The rise in SNR is significant here. Watch that and let us knows if it goes off again and what the external circumstances were. Maybe something dried out in your external wall box, or at the drop point.

Re: Power levels too high?
 

Thanks for that. I don't appear to have an external wall box. The cable comes from a run going up the side of the building which is a block of flats. I just have a metal box inside with main cable entering and three outputs. Internet and two TV boxes Tivo and SA.

Re: Power levels too high?
 

If you get a chance, it's worth tracing your cable back to its source inside the block to see if that's a rats' nest. If it is, anything can happen. You's see splitters on splitters and JB can tell you what that means. On the other hand, it might be perfectly OK.

The cable to the block will come from a street cabinet, prolly sitting in the sun. That would account for the power level fall and if I'm right, it'll rise again this evening. Keep us posted.

Re: Power levels too high?
 

The power actually dropped slightly after dark.

Re: Power levels too high?
 

So there's a highly local situation, it seems; like in the block. As I said it'll be worth tracing your coax to see what state the block's box is in.

Re: Power levels too high?
 

I fitted a 10Db Forward Path Attenuator and now get the following. Are these power levels still ok.

Downstream Channels
Lock Status Channel ID Frequency Modulation Rx Power SNR Pre RS Errors Post RS Errors
Locked 43 315000000 Hz QAM256 -4.3 dBmV 41.4 dB 98 0
Locked 40 291000000 Hz QAM256 -3.4 dBmV 41.4 dB 22 0
Locked 41 299000000 Hz QAM256 -3.6 dBmV 41.8 dB 40 0
Locked 42 307000000 Hz QAM256 -4.1 dBmV 41.8 dB 46 0
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Unlocked Unknown 0 Hz Unknown 0.0 dBmV 0.0 dB Unknown Unknown
Upstream Channels
Lock Status Channel ID Frequency Modulation Tx Power Mode Channel Bandwidth Symbol Rate
Locked 1 35800000 Hz ATDMA 40.5 dBmV 16QAM 6400000 20480 Kbits/sec
Unlocked 0 0 Hz Unknown 0.0 dBmV Unknown Unknown 0 Kbits/sec
Unlocked 0 0 Hz Unknown 0.0 dBmV Unknown Unknown 0 Kbits/sec
Unlocked 0 0 Hz Unknown 0.0 dBmV Unknown Unknown 0 Kbits/sec

Re: Power levels too high?
 

Those levels are OK. Does it perform OK now?

Re: Power levels too high?
 

So you've got a powered booster to amplify the signal then a attenuator to lower it? Just be done with the amplifier

Re: Power levels too high?
 

Even though the recieve levels are better the upstream TX Power should not have been attenuated, so something is still not quite right. After having another look, you were originally locked onto 27.40mhz but since the levels have been adjusted and HDU fitted it's now locked onto 38.50mhz with a 5dB variance so could well be incorrect return levels in the network?

Re: Power levels too high?
 

Higher frequencies don't travel as far.

Re: Power levels too high?
 

It's nice to know that people on this forum are so helpful.
If I turn that off I lose my TV. I could always remove the attenuator. I suspect it does not help much either way. The only problem that seems to occur is worse ping and jitter but that has been more of a problem for a couple of weeks.

Re: Power levels too high?
 

yes if its off the tv goes off but if its replaced with a splitter it would be fine

Re: Power levels too high?
 

The amplifier was fitted because my TV signals were a bit low and I was losing HD channels especially in the evening.

Re: Power levels too high?
 

Higher Frequencies attenuate more depending on cable type and the length of the cable, at 30mhz RG6 Loses 3.84dB @100m, so the difference between 27mhz and 38mhz would be small, say 0.50db if that, not 5dB.