cancel
Showing results for 
Search instead for 
Did you mean: 

De-Coupling an old Valve type TV

Community Veteran
Posts: 17,880
Thanks: 1,644
Fixes: 19
Registered: ‎06-11-2007

De-Coupling an old Valve type TV

I use a Eddystone 840C short wave radio to receive CW/RTTY. and HF FAX .... and also SSTV ...
This morning I was attempting to receive an SSTV signal from Basingstoke, when my missus decided to put the big TV on, in the next room, to entertain the GGDaughter... The resulting "mush" completely wiped out the reception of the SSTV signal.  I vaguely remember something from my past, when this kind of interference happens, it is necessary to "de-couple" the TV Power plug from the main ring circuit.... BUT... I can`t remember how to do it...or what components to use....
can anyone point me in the right direction, to see if I can minimise this interference, Perhaps I need to de-couple the Eddystone, my Laptop, and other stuff too?  Any advice and instructions would be much appreciated.
11 REPLIES
pierre_pierre
Grafter
Posts: 19,757
Registered: ‎30-07-2007

Re: De-Coupling an old Valve type TV

how about a ferite ring? - very common in the CB radio days
another one but more expensive is a something like a transformer with a capacitor couple, but never used one
a good source of these odd items is  http://www.keene.co.uk/
198kHz
Aspiring Champion
Posts: 3,492
Thanks: 423
Fixes: 11
Registered: ‎30-07-2008

Re: De-Coupling an old Valve type TV

Interesting, shutter. Were you still receiving the signal on the HF rig, and the interference blanked out the SSTV screen, or was it the actual HF signal that was lost? If so, what band/frequency was it?
Doesn't sound like a mains problem to me.
Remember you are unique - just like everyone else
Community Veteran
Posts: 3,366
Thanks: 15
Registered: ‎06-04-2007

Re: De-Coupling an old Valve type TV

'de coupling' is simply a term used to describe a capacitor which will pass the signals you want to filter out to ground. You would likely want to place this capacitor across the output DC side of the internal power supply used by the Eddystone. Try 10 or 15uF to start.
--
3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
Community Veteran
Posts: 6,735
Thanks: 12
Registered: ‎02-02-2008

Re: De-Coupling an old Valve type TV

Was the interference constant or just for a while at switch-on, which could be the degaussing circuit?
Big old CRT TV's use a lot of high-power, high-voltage and high-frequency components, so almost inevitably chuck out a LOT of RF interference as they age so as above, the mains wouldn't be my first suspicion.
Community Veteran
Posts: 17,880
Thanks: 1,644
Fixes: 19
Registered: ‎06-11-2007

Re: De-Coupling an old Valve type TV

OK... for those interested,.... The received frequency on HF is 3781 kc/s  and when the TV was switched on, the signal was lost in the "mush"  created by the TV... As the TV is in another room, about 14 feet distant from the HF receiver, and a brick wall between..... the HF receiver aerial is a long wire, dipole 34 feet each leg, running at bungalow rain gutter height. (North South). and the "lead in" is tv coax about 100 feet, which does not run anywhere near the TV aerial lead in..... So , I am convinced that the "mush" is being transmitted along the ring main (either live, neutral or earth , or even any combo !)... and back into the HF receiver...
Received frequency is 3781 kc/s
SSTV program is Easypal 
TIme of transmission is 07:40A daily
PNnewbie
Rising Star
Posts: 271
Thanks: 4
Fixes: 1
Registered: ‎04-07-2008

Re: De-Coupling an old Valve type TV

I know this thread is getting on a bit but just in case someone's still reading it... Smiley
This ‘mush’ or ‘hash’ can be radiated from the television via either the mains wiring or via the television antenna.
Remove the television aerial plug from the back of the television whilst both the television and the Eddystone are running and if the ‘mush’ is still present then it is being radiated through the mains wiring.  If it disappears then it is being radiated from the television via the aerial.
Electrical suppressors are obtainable that can be fitted between the television and the power socket.  These essentially route interfering signals down to earth.  They can have the additional advantage that they can suppress interference already on the mains wiring that could interfere with the television.
If it appears that the interference is being radiated from the aerial the cable can be wrapped around a ferrite core or ferrite rod.  This is very much a hit and miss exercise.  If you know a local ham you may be able to ‘borrow’ some ferrites to try out.  You could also pick his brains – we do try and be helpful wherever possible !  Wink
Incidentally it may be worth wrapping the television’s mains lead around a ferrite before you spend any money on a suppressor – might just help.
Good luck…
John
Community Veteran
Posts: 17,880
Thanks: 1,644
Fixes: 19
Registered: ‎06-11-2007

Re: De-Coupling an old Valve type TV

Thanks for the continued interest !.....
Problem solved....
how.? ... Easy....  Cheesy
Moved house,
took the old VALVE TV`s  (central heating ) to the British Heart Foundation shop, (who have since sold them on!)...
Regretting selling the Eddystone but have replaced it with an ICOM IC-R71E   
and
Bought two new flat screen freeview tv`s !...
Probably a bit drastic, but it works ! ! .  Grin
Moderator
Moderator
Posts: 27,084
Thanks: 1,796
Fixes: 146
Registered: ‎14-04-2007

Re: De-Coupling an old Valve type TV

Interesting spec on the R71E.
Careful when changing the battery backup.

Customer and Forum Moderator. Windows 10 Firefox 62.0.3 (64-bit)

Community Veteran
Posts: 17,880
Thanks: 1,644
Fixes: 19
Registered: ‎06-11-2007

Re: De-Coupling an old Valve type TV

Error 404

I know about the memory battery ..... getting it changed soon !..
(tks om 73 de Gerry)  Wink
Moderator
Moderator
Posts: 27,084
Thanks: 1,796
Fixes: 146
Registered: ‎14-04-2007

Re: De-Coupling an old Valve type TV

http://www.rigpix.com/icom/icr71aed_manual.pdf

Customer and Forum Moderator. Windows 10 Firefox 62.0.3 (64-bit)

Community Veteran
Posts: 17,880
Thanks: 1,644
Fixes: 19
Registered: ‎06-11-2007

Re: De-Coupling an old Valve type TV

Error 404 (again)
But ... don`t worry strat..... I already have the PDF for the manual !..  Wink