Freeview Zinwell Momentary Freeze.

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theoldfarter

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Topic # 18233 3-Jan-2008 08:42

I've got a Zinwell "Freeview certified" decoder. From time to time the image will freeze for a second.
I've got the latest firmware that's available downloaded from the satellite.
I believe the Zinwell can overload easily.

I'm told that the easy fix is to put any size splitter between the end of the cable from the dish and the set top box.
I did that & it worked.
With & without splitter: signal quality shows as 100%.

Without splitter: signal strength shows as 84%.
With splitter: signal strength shows as 80%.

The splitter I used is one for the VHF/UHF frequency's, goes up to 900MHz (one I borrowed)
I believe I ought to use the correct type of splitter.

Four questions:
1. What are the reasons, if any, for not using the VHF/UHF splitter?
2. What is the correct frequency range of splitter, that I should get?
3. Should I go for an in-line attenuator, rather than a splitter, if so, what Db?
4. What is the optimum range for the signal strength, of this Zinwell box?

Happy New Year.

Trevor

cyril7

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Reply # 102639 3-Jan-2008 09:01

Hi, and welcome to GZ. To answer your questions

Using the VHF/UHF splitter that is not rated beyond 900MHz means you have no idea what it does in the satellite L-band (950-2050MHz) so you place a whole lot of unknowns into an already unkown problem.

The Satellite LBand IF is 950-2050MHz.

A LBand rated 2way splitter will offer rougly 5.5dB loss at around 1750MHz, so yes a DC pass attenuator of 5 or 10dB would be better but are hard to find, and there is nothing really wrong with using a splitter as an attenuator.

The Zinwell box does not have a good reputation, it suffers from over sensitivity, and dodgy firmware and appears to put out lots of spectral rubbish on the RF antenna port, personally I would never buy one there are plenty of non certfied boxs from the likes of Strong and Topfield that are superiour in every way and cost less to boot.

I understand that the Zinwells are about 5-10dB over sensistive based on tests done by others using calibrated signals to assess performance. Obviously each unit will be slightly different. The quality is unlikely to change as once a reasonable C/N is achieved the decoder is fully satisfied, however the signal level could be dropped significantly and the quality never budge. Obviously if you overload the tuner intermod will work against you also as you have found.

I would get yourself a proper rated 2way splitter, they are only $12-15 at DSE, just make sure you connect the STB via the DC pass port. A normal STB is designed to have a signal acceptance range of around 40-85dBuV so quite a range(40-50dB), so you could try a 4way splitter (11dB loss) and pull the signal further into the safe zone without compromising operation.

Cyril

theoldfarter

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Reply # 102648 3-Jan-2008 09:37

Thank you Cyril, for such an informative reply.

I belatedly realise that I should not have bought the Zinwell.
I knew nothing about satellite gear when I did & after reading various forums, I would have bought differently.
Alas, I'm stuck with it & can only try to get the best from it.
With people such as yourself, willing to freely advise, we, with limited or no knowledge of satellite technology, can hope to steer clear of 'dodgy' stuff in the future.

Trevor

theoldfarter

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Reply # 103515 8-Jan-2008 09:49

I contacted the shop I bought it from & informed them of the problems I was experiencing.
They contacted Next & was informed to swap it with one from a new batch that is available.
I rang Next & asked if the replacement unit addresses the freezing & was told yes!

I installed the replacement & can report that there is no more freezing.

The signal strength now shows as 79% (no splitter used) (was 84% on old unit)
The signal quality shows 100% (after allowing for unit warm-up)
Before the unit warmed up, the signal quality would fluctuate on a few channels, between 97-99%.
I don't know if the fact that it is a completely overcast day, with some rain, could be partly responsible but after 1/2 hour, all channels were at 100% quality.

The old unit used H/W v1.0
S/W v6.0
August 20th, 2007
There was no update available from the satellite.

New unit has same H/W version.
S/W v6.5
November 30th, 2007

cyril7

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Reply # 103520 8-Jan-2008 09:59

Good to see you got it all sorted.

Cyril

richms

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Reply # 103713 8-Jan-2008 23:26

You wont get a great deal of attenuation from a splitter if the other ports are not terminated, quite important on satillite since the modulation isnt designed to handle reflections like dvb-t is, and the signal will reflect from the unused ports mismatch. Not usually a problem unless there are a few 10s of meters of cable hanging off it however.

Richard rich.ms

cyril7

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Reply # 103730 9-Jan-2008 08:00

A Hills brand splitter as measured with my LBand test meter at 1156MHz (ie 12456MHz Mux) shows that terminating and not terminating one port makes around 0.5dB difference in level, ie around 4.5dB with no other port terminated 5.0dB with it terminated. As compared to a straight F-F coupler.

Ideally adding a potential reflection source is not good, however I have never noted any change in the BER with no line length attached, start adding more than 3-4meters of unterminated cable and things start to change.

Cyril

richms

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Reply # 103817 9-Jan-2008 15:02

Thats interesting, in previous testing at a former employer we saw a small dip on the spectrum with connecting a splitter inline (1-1.5), and then when a load was connected to the other port, thats when it dropped down by about 5dB's

Richard rich.ms

cyril7

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Reply # 103854 9-Jan-2008 17:46

Will redo the test when I get a chance.

Cyril