[mythtvnz] Tinfoil madness

Sat Nov 7 04:01:15 GMT 2009

If you measure between the earth and the neutral at the power point on 
the ohms scale it  should be as close to 0 ohms.
 This would prove that you have a good connection at the sub board and 
main board with out springing for anything flashier.
 I noticed that you mentioned RCD are the at your board, just curious as 
this gives me a idea of the age of you house wiring.
Stu

Brett Miller wrote:
> 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. 
>
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