Author Topic: Weird Happenings  (Read 3759 times)

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Offline Dawn

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Weird Happenings
« on: 26 Oct 2009 at 12:57 »
Hi my name is Dawn, I'm new to the Forum but not new to the club.  I'm the writer of Lincs/notts news.

I have a strange happening to report.  

One of my section members gets himself into trouble with his neighbours every time he runs his Duggies (both pre & post war).  What happens is that something to do with the old engines blacks out the TV screens of his neighbours TV's, but not his.  He lives on the edge of a transmitter area (he thinks) & has noted that his TV aeriel points in a different direction to the others.  When a friend calls round on his Dragonfly the same thing happens too!.

Has anyone heard of this happening before & more importantly (before he gets evicted by the neighbours) does anyone know of a cure?

Please let me know & i will pass on your advice to him.

Dawn.


Offline kmd

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Re: Weird Happenings
« Reply #1 on: 26 Oct 2009 at 14:15 »
Hi Dawn

You can get Clip on Ferrite RFI / EMI Filter for Noise Suppresion of electrical interference.
This unit just clip onto the TV Aerial lead.
They cost about £5 depending on make.

Regards
Kevin

Offline Dawn

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Re: Weird Happenings
« Reply #2 on: 27 Oct 2009 at 08:58 »
Thanks for that.  I will pass that message on.

However we were looking for something to perhaps put on the bike as that would be cheaper than kitting out the whole street with things to stop their TV's going on the blink. 


Offline eddie

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Re: Weird Happenings
« Reply #3 on: 27 Oct 2009 at 12:32 »
Hi Dawn,
               This problem seems to be a symptom of the 'digital age'. Our old TV is fine when receiving an analogue signal but the picture breaks up or freezes when receiving a digital signal via a set top box if someone goes up the road on a 'twist and go' scooter. I have put it down to the unscreened ignition system as the problem does not occur with cars with the ignition shielded under the steel bonnet.
                          Regards,
                                   Eddie.

Offline Mikerobe

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Re: Weird Happenings
« Reply #4 on: 01 Nov 2009 at 01:45 »
Hi,

I hope the ferrite filter suggestion works although I have a suspicion it might not. If the interference is being picked up by the TV aerial then putting a ferrite around a screened TV downlead my not be terribly effective.  However fitting a band pass filter in series with the lead may be more successful. I found the following on another forum (http://www.digitalspy.co.uk/forums/showthread.php?p=3900193) do take note of the marginal signal strength comments though:-

" I have the same interference problem as you do, and I have improved this greatly for little money or effort. I have a Nokia 221T freeview box in a poor signal area (<33% of maximum of the Nokia signal strength meter). I used to get brief screen freezes and sound dropouts and popping when a light switch was used, my boiler ignited (it is a modern one with no pilot light so it self ignites using a spark), if a car or moped went by, fridge door opening etc etc...

Now I get only occasional pixellation and the odd sound dropout but no screen freezes and sound popping is rare (which is nice as it is annoying).

How did I do this 'magic'? I simply fitted an inline RF coax passive bandpass filter. You lose some signal level (about 5% of the signal meter scale which might be a problem if you are in a marginal signal area), but happily interference is only a small issue for me nowadays. Light switches, fridges etc are no problem at all, and only some vehicles and my shredder can cause interference but it is much less frequent and severe than before. It has transformed my viewing experience. My shredder is still bad (but improved) but that is to be expected.

I got it from www.cpc.co.uk, the part number is "APFILTER"
(Mikerobe: http://cpc.farnell.com/_/filter/high-pass-interference-filter/dp/APFILTER?Ntt=APFILTER) and it costs £3.055 plus vat and postage(Mikerobe: they have gone up a bit since). Obviously, I can't guarantee it will help anyone, but it really has helped me greatly. You just plug it inline with your aerial cable at the point where you connect the aerial lead into your freeview box.

I am also about to replace my cheapo loft aerial with a "DX8W" aerial from Antiference (about £26 from CPC, small acceptance angle, large forward gain, large front to back ratio, has a PCB balun and is only about 1m long so it will fit in my loft or won't blow about that much on your roof (which could give me signal dropouts as I am in a weak signal area with a small acceptance angle aerial).

I am also replacing my coax with the "100" type (mine is DS100 but I think it is the same as CT100). This is the 'double insulated' type which means it has a braided screen (like the cheapo stuff has), but it also has a solid foil which should give much better screening. I believe that the braid gives less than 85% coverage (I've also read it is nearer 65%), so I am hopeful that the superior screening area (100%!) will remove the rest of the interference(!). There is less attenuation in this cable also (compared to 'low loss coax'), but I don't see that as a great factor since my cable run is only about 10m (although I am in a weak signal area so you never know...!).

I have read elsewhere that people have tried pointing their aerial a little upwards, and I can well believe that that can help for some people."


I also found this rather useful PDF about selecting spark plugs for Vespa and Lambretta scooters which might help explain the issue some. Apologies for the tinyurl but I couldnt find  a better link from google http://tinyurl.com/yzw2ho6

I Quote a portion here:-

"To make matters worse, many of the spark plugs being sold today have been designed for modern and not vintage engines and are fitted with an internal resistor that actually reduces the voltage to the spark plug and so reduces the spark size. The main purpose of this resistor is to reduce RFI (Radio Frequency Interference) and so protect modern vehicles electronic devices, such as engine management systems, inbuilt mobile car phones, GPS systems, TVís etc, which your typical vintage scooter is probably not and never will equipped with."


So that may in part explain the lack of RFI from modern vehicles and greater prevalence on older ones. The others, I suspect, being:-  the use of Electronic ignition systems rather than points based systems and the fitting of suppressor caps and suppressor capacitors to ignition coils, alternators and any other electric motors (http://www.indiacar.com/infobank/car_radio.htm). I suspect points may well make more interference across a broad spectrum of frequencies. I am sure everyone at some time has suffered crackles and buzzes on their radios when things like the contacts on the relays on their central heating boiler start to get old and warn.

I am not sure what remedial measures one might be able to take on a vintage bike. For the reasons stated in the Scooter document I dont suppose suppressor caps are feasible and neither would be the appropriate plugs. Let alone the aesthetics of fitting non standard caps. I am not sure what the situation would be with suppression capacitors. I will try and find out more from someone I know who knows more about this than I.

Mike 8-{>