[mythtvnz] Tinfoil madness

[stuart]

Hi Dylan
 I will throw in my two cents worth in. First I do not have any Sat gear 
set up, must get round to it.
But I am a sparky so I will throw in some ideas.
 As has been pointed out a multi meter with some testing info would 
help, a ups even a interactive and not a double conversion type will 
probably not sort out a grounding or earthing fault.
 The think that leaps out is that the is no problem when isolated from 
the mains, on battery. But I do have a question, does your signal 
improve or do they remain the same?
If it remains the same I would try a get that up, I may be wrong but I 
thought that getting it around 70% or above would me preferable.
I can give you instructions on how to test you earthing at power point 
and gear to a ruff level with out spending heaps of money on special gear
 but you will need at least a cheap meter.
One last thing  as I do not now the area you are in, but is the actual 
aerial actually the correct one for the area, A electrical supplier like 
Rexel, usually will be able to check, I noticed that one I had was 
different from the neighbors and was the wrong type.
Stu

Dylan Hall wrote:
> Let me begin with the mad picture, then explain how I got there (see 
> attached).
>
> The only way I can get reliable reception with the TVNZ and Mediaworks 
> transponders is to wrap my USB sticks with tinfoil and ensure that 
> tinfoil is connected to the casing of the RF splitter. The tinfoil 
> can't cover the fly leads from the USB sticks, and it can't contact 
> with the shield of the USB connector.
>
> Let me start from the beginning....
>
> I decided to have a go with DVB-T for freeview. I got a pair of USB 
> sticks. I didn't want them in the lounge where I have existing RF 
> outlets so I installed a splitter in the basement and added 23m [1] of 
> good Quad shield RG6 cable to extend the aerial connections into my 
> computer room at the other end of the house.
>
> This almost worked. I had good TVNZ and Mediaworks, but the Kordia 
> transponder was breaking up, regular blocking etc.
>
> I had a play with tzap to try and get an idea of what's going on.
>
> I was getting a signal strength of 45-50%, with a low BER and no 
> uncorrected blocks for TVNZ and Mediaworks.
> I was getting a signal strength of 35-42%, with a moderate BER and a 
> small number of uncorrected blocks for Kordia.
>
> I decided it was time to audit the whole aerial/cabling/splitter 
> setup.  The UHF aerial on the roof was small, rusty, and using the 
> cheapest nastiest cable. The VHF/UHF combiner was full of corrosion 
> and a spider colony. The cable from the combiner to the basement was a 
> little nasty.
>
> I replaced the UHF aerial, the combiner, the cable to the basement, 
> and the splitter in the basement (with a splitter with the right power 
> pass options should I need to add a masthead amplifier later).
>
> At the end of this exercise the signal strength seems to have dropped 
> slightly, but it's now the same for all the transponders (approx 45%).
>
> If I plug the pair of USB sticks into my laptop they both work fine, 
> low BER, no uncorrected blocks.
>
> If I plug them into the backend PC it goes nuts. Sometimes they work. 
> Sometimes one stick works, the other fails with a high BER and lots of 
> bad blocks, and sometimes both sticks fail, again with high BER and 
> lots of bad blocks. More confusing is the failures are with the TVNZ 
> and Mediaworks transponders. The Kordia one is perfect.
>
> I went through all kinds of exercises, changed the splitter, changed 
> the cables, added a powered usb hub, tried different usb ports on the 
> backend PC. At one point during the process I convinced myself the 
> problem was RF interference from the backend PC so started playing 
> with bits of tin foil. I eventually settled on the madness described 
> at the beginning of this email which works rather well!
>
> Does anyone have a sane explanation for the issues I'm seeing?
>
> I have a number of theories...
>
> 1. The signal strength is too low and it only takes the slightest bit 
> of interference/noise to push it below the working threshold and fail.
> 2. There is a nasty source of interference in/near my house.
> 3. Something electrical, ground loop, noisy power, etc... Laptop 
> running on battery is happy, PC running on mains sad. Added an online 
> UPS to the mix but this didn't help.
>
> I see a number of things I can do now:
>
> 1. Make myself a hat from the left over tin foil and hope I get a 
> moment of clarity.
> 2. Accept the status quo, it is working after all, I just don't 
> understand why.
> 3. Futz with the antena setup further, mast head amp, new UHF aerial 
> closer to the PC, professional installer.
> 4. Buy a PCI/PCIe based tuner and hope it works better.
>
> Any ideas/comments/etc greatly appreciated.
>
>
> Thanks,
>
> Dylan
>
>
> [1] In case people don't know, most cables (RF, cat5/6) had printing 
> on the casing every meter. Somewhere buried in the writing is the 
> number of meters left on the reel. If you can find the writing closest 
> to each end of a cable you can subtract the two values and determine 
> how long your cable is :)
>
>
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