Signal Quality

[hugson]

I've had my T2 (with 3 tuners, including USB) since January. I've always had somewhat poor reception, with signal strength never more than 72 and quality around 60 (so often Channel 10 is almost unwatchable, and many recordings produce errors when saving in VideoRedo). On Friday night all signals collapsed, rendering the unit almost useless. So, on Saturday, I decided to investigate, and in the process redid all the tuners by connecting all 3 directly to my antenna amplifier (and during this process, I noticed the aerial connection to the wall was half out of its socket!).
But the difference is extraordinary. Tuners B and C give signal strength and quality of 99 on all channels, while Tuner A gives 74 and 99 (I do wonder why Tuner A gives inferior readings). I get no pixellation whatever on any channel.
This begs the question of why the supplied antenna A to B connector is so thin, as I imagine this contributes to the poor signal quality I was experiencing. Or am I barking up the wrong tree?

[MrQuade]

This begs the question of why the supplied antenna A to B connector is so thin, as I imagine this contributes to the poor signal quality I was experiencing. Or am I barking up the wrong tree?

The poor quality picture and signal values would have been due to the antenna cable that was half connected at the wall. Did you try going back to your original antenna connection arrangement and re-test the signal levels for comparison once the wall connection was fixed?

The signal strength by itself is not really that important a figure. The quality is the important one, and if you are seeing 99% on that now, then there is absolutely nothing wrong. The signal level is only really useful as a indication of how strong a signal each tuner is receiving relative to the other tuners. In fact, you should be keeping an eye on any time you see signal levels that are pegged at 99%, as it could mean the signal may be approaching a level that is *too* strong and may be over-driving the tuners (which can then impact your signal quality).

[peteru]

The "thin" looking loopback cables are the high quality ones. They have all-metal connectors and high density shielding braid. The "thick" black loopback cables you often see are the cheap and inferior ones.

[BigbobOz]

I replaced my T3 with a T4 in the same location and the reception has gone from the 90s to the 70s or worse. I put it down to the A-B cables but have been too lazy to swap them over to check.

The new versions look like good quality but I thought the shielding needs to be spaced from the core? Read that somewhere a long time ago...

[MrQuade]

The signal strength values you get from the T3 are not directly comparable to the readings you get from the T4. The number is just an indicator and does not represent an actual real world value.

The fact that the T3 measures 90 and the T4 measures 70 did not necessarily mean that the T4 is less sensitive.

[BigbobOz]

Possibly true but I should have added that the T4 gets frequent picture break ups vs the T3 only on stormy and rainy nights

[prl]

... The new versions look like good quality but I thought the shielding needs to be spaced from the core? Read that somewhere a long time ago...

Yes. But they are indeed coax cables. Just thin ones.

[BigbobOz]

I get that but why aren't long cables made this way? Hell all coaxial cables?

[MrQuade]

I get that but why aren't long cables made this way? Hell all coaxial cables?

Because they are fragile and can't be run for any significant distance. You'll notice that many coax cables are mostly inert material for both insulation, protection and strength.

[BigbobOz]

According to the coaxial wiki page, the diameter of the shield is a direct factor on it's performance
https://en.wikipedia.org/wiki/Coaxial_cable

The technical details are way beyond me but the diameter is a factor in it's performance but length is also a factor, so for short leads the smaller diameter may be acceptable...

[prl]

One of the main characteristics, the characteristic impedance, is proportional to the log of the ratio between the diameters of the inner and outer conductors. So yes, size is important there, but it actually depends on the ratio of two sizes.

It's also dependent (mainly) on the dielectric constant of the material between the inner and outer conductor, so the same geometry can have different characteristic impedance.

[peteru]

While the science behind RF signals can be complicated, the answer in this case is simple.

The original thick cables as used on the DP-Series were not good enough for this particular model of tuners. When working with the tuner module manufacturer on pre-production samples, they recommended switching to the thinner cables. As soon as that was done, reception issues that were of concern disappeared.

Ergo, the thinner cables are better for this application.

[bpratt]

I upgraded to a T4 from a P2, and have noticed signal quality is an issue, and have posted about it before in these forums.

I was getting told there's nothing wrong with the T4, and that it is all to do with my feedline and aerials here, so I accepted that as being the story.

Recently I plugged in my P2 aerial in from the out on my T4. No issues at all with reception on the P2, yet issues with Ch7 breaking up and poor signal quality as shown on the T4.

So I am now thinking the DVB tuners on the T4 are a bit on the dodgy side of things.

[MrQuade]

I was getting told there's nothing wrong with the T4, and that it is all to do with my feedline and aerials here, so I accepted that as being the story.

I don't think that there is anything wrong with your T4 per-se, just that the model of tuners in the T4 are probably a bit more sensitive to signal/noise than those on the T3 and evidently the P2.

The main point of this particular thread was initially that the actual signal readings that the T4 gives back are not comparable to the readings you see on other STBs. The performance of the tuners can be assessed by the integrity of the picture you are receiving. I know that my own antenna feed is pretty poor, and I get occasional pixelation with my T4, and less on my T3, so I guess that your experience is similar.
(the other point made in the thread is that the passthrough cables supplied with the T4 are actually quite good)

I'd still be guessing that your antenna feed is probably marginal as far as the T4 tuner performance goes, and is causing the T4 tuners to struggle where the P2's are still working fine. If you were to improve the signal to the T4, its tuners probably wouldn't have an issue.

[IanB]

bpratt,

You may have the beginning of the failing tuner regulator issue. There are 2 regulators each supplying a pair of tuners.

Test each tuner individually, select each tuner in turn as the preferred tuner in the setup menu.

Directly connect the tuner under test to the antenna feed, do not connect any of the loop through cables at this time.

Observe the signal quality and strength for all the broadcasters. Watch and listen for stream corruption bursts in both the video and audio.

All 4 tuners should show similar performance. If 2 are obviously erratic compared to the other 2 then you need to get your unit repaired.

[bpratt]

You may have the beginning of the failing tuner regulator issue. There are 2 regulators each supplying a pair of tuners.

Test each tuner individually, select each tuner in turn as the preferred tuner in the setup menu.

Directly connect the tuner under test to the antenna feed, do not connect any of the loop through cables at this time.

Observe the signal quality and strength for all the broadcasters. Watch and listen for stream corruption bursts in both the video and audio.

All 4 tuners should show similar performance. If 2 are obviously erratic compared to the other 2 then you need to get your unit repaired.

Interesting, when I get a chance I'll give that a test out and see what I can find.

This has been a problem since I bought my T4, so nothing new.

[bpratt]

I tried it out last night, and Tuner B is a real problem... pixelate video and broken up audio.

I wish I had've been told to try this out when the T4 was still under warranty, because this was an issue since day one with it.

[prl]

I tried it out last night, and Tuner B is a real problem... pixelate video and broken up audio.
...

Just tuner B or all the tuners from there down the antenna loopthrough? If it's all the tuners B-D, it may be a problem with the A-B loopthrough cable.

[MrQuade]

I wish I had've been told to try this out when the T4 was still under warranty, because this was an issue since day one with it.

You may have some luck there considering that you have a record of it being a problem when it was in warranty.

[bpratt]

I tried it out last night, and Tuner B is a real problem... pixelate video and broken up audio.
...

Just tuner B or all the tuners from there down the antenna loopthrough? If it's all the tuners B-D, it may be a problem with the A-B loopthrough cable.

Aerial plugged directly in to the back of it, no loop through cable.

[martbd]

I've got the same issue with ABC, but when bypass T2 & plug the directly into a rooftop antenna the problem goes away.

[Sir Lancelot]

Hi All.

Re signal quality and tuners. If you read the item under T4 behaving like a twin tuner in General Topics you will find more on this sunject.

Regards
Lance

[MrQuade]

Re signal quality and tuners. If you read the item under T4 behaving like a twin tuner in General Topics you will find more on this sunject.

I don't know if there is an relevant info in that thread. The "twin tuner" thread is about the T4 losing two of its tuners entirely, whereas this problem is about poor reception from a particular broadcaster.

[prl]

I don't know if there is an relevant info in that thread. The "twin tuner" thread is about the T4 losing two of its tuners entirely, whereas this problem is about poor reception from a particular broadcaster.

Martbd's tuner issue was also posted in a separate topic, Tuner in not working on ABC. I suggest that discussion of martbd's tuner problems be continued there, where Grumpy_Geoff has already requested some more information.

[Sir Lancelot]

Hi MrQuade.
I read this in IanB post earlier.
You may have the beginning of the failing tuner regulator issue. There are 2 regulators each supplying a pair of tuners.

But this is similar to what I have had with one of my T4's. I had intermittent problems and sent the box for repair. It came back with report that there was nothing found wrong with it (after $99.95). Less than 2 months later tuners A & B have failed completely. I have asked to have it repaired at no cost to me.
I do know when there is something wrong with my equipment.

Regards
Lance

[Sir Lancelot]

Hi again.
I forgot to say that the original problem was that like hugson I had failure on various Channel groups. One day it could be ABC, another day (often lasting several days) Prime7, and so on. It seemed like this was the beginning of a failing tuner regulator.
I hope that this may help someone with maybe this problem.

Regards
Lance