[mythtvnz] Tinfoil madness

[Brett Miller]

Dylan Hall wrote:
> Before I get into the detailed response, it's been pointed out that
> it's rather poor form to attach images to messages like this, rather I
> should have included a URL to the image. Sorry for my spammer like
> behaviour :(
>
> On Thu, Nov 5, 2009 at 8:11 PM, stuart <stugo at xtra.co.nz> wrote:
>>
>> 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?
>
> The signal remains the same, just the BER and bad blocks varies.
>
> The UPS in question is a fairly flash (but elderly) unit that does the
> whole regenerate the power thing, and just to be sure I ran the tests
> twice, once with the UPS connected to the mains, and once running on
> battery. This didn't seem to make any difference.
>
> I brought one of these (http://jaycar.co.nz/productView.asp?ID=QP2000)
> yesterday and tested a bunch of power points around the house
> including the power strips with the server/UPS connected. Everything
> appears fine :)  I also verified that all my RCD's work :)
>
> I removed the cover from the fuse box (at the suggestion of another
> electrical in the know person) and eyeballed all the ground and
> neutral connections to look for obviously loose connections or
> blackening/scorching. I didn't go as far as sticking a screw driver in
> and tightening everything. I feel thats a job for someone qualified :)
>  I didn't find anything to concern me.
>
> Dean suggested: "What happens if you remove the foil, but earth the
> antenna, cable shield and the splitter?" - Anytime I remove the foil
> from the USB sticks the BER rises and it becomes erratic. I tried
> earthing the splitter housing but this didn't make any difference.
>
>> 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.
>
> I have a basic digital multimeter and a rather elderly oscilloscope so
> any instructions that don't involve my wife claiming on my life
> insurance would be appreciated :)
>
>> 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 think you've hit the nail on the head. I have a new bit of data from
> last night. The signal levels on all three transponders dropped around
> 1-2% last night due I think to some very misty weather. During this
> time all three transponders experienced higher BER and bad blocks to
> the point they were unwatchable.
>
> This evening the mist is gone and the levels are back where I expect
> them.
>
> This suggests to me the signal is just too weak if such a small drop
> is enough to tip it over the edge.
>
>> 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.
>
> I'm in the Johnsonville (Wgtn) area, at the foot of Kaukau. I'm very
> close to the transmitter, but thanks to a lump in the hill don't have
> line of sight :(
>
> It's roughly the same size/shape/style as the neighbours but I get the
> strongest signal pointing it a slightly different direction than
> everyone else (maybe 15 degrees).
>
> My plan at this stage is to borrow a Fluke cable tester we have at
> work (it does cat5/6 and I think coax) and just verify I haven't
> munted one of the cables, for example failed to connect the shield
> correctly.
>
> I'm also going to pick up a masthead amp. I'm looking at either
> http://www.freeviewshop.co.nz/kingray-24db-shielded-digital-mast-head-amplifier-p-482.html
> or http://jaycar.co.nz/productView.asp?ID=LT3270 . Hopefully this
> isn't throwing good money after bad :)
>
> The Jaycar unit is a little cheaper, but for some reason the pictures
> of the Kingray unit convey a sense of quality.
>
> Thanks for everyones comments so far :)   I'll do some more tinkering
> and report back next week.
>
> Dylan
>
>
Dylan,
Top marks for experimentation.
GME Kingray product is much better than Jaycar.
Jaycars prices are not always so sharp.
Can not beat signal strength from the source or antenna, does your antenna 
have enough gain ?

Your hill will complicate the alignment as UHF is line of sight.
All coaxial cable has loss no matter how good it is & as you said "failed to 
connect the shield correctly" could be your problem.

Problem with normal television RF cabling methods is that there is no 
galvanic isolation thru' normal splitters & sometime you need to use DC for 
power & control.
Maybe you can buy a fully isolating splitter, would be easy to make if you 
can get the appropriate connectors.
I have never seen this part but I have not had to look.

Masthead amps are good to compensate for cable length & splitter loss.
Digital TV was meant to be more immune to noise/interference but this was 
just an excuse to make the tuner more cheaply.

Cheap & old PC SMPS are prime candidates for noise generators as are 
electronic ballast fluorescent lights (energy savers).

Does your laptop with USB tuner work sitting next to basement PC ?
With PC connected & not ?

Remember that your scope is a single ended input device, the impedance to 
GND thru' probe ground clip is low.
The scope GND is connected to power lead earth.

Different earth currents in diff parts of the house is unavoidable due to 
our MEN power system & increasing amount of SMPS equipment.

Brett.