|
Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
|
Thread Tools |
6th Sep 2008, 10:28 am | #1 |
Retired Dormant Member
Join Date: Aug 2008
Location: Bellac, 87. France.
Posts: 357
|
Aerial capacitor
On my Defiant M900 the aerial capacitor is 200pf. Is a modern replacement resembling a lentil good enough or should I be looking for something more rugged as I live in an area where lightening strikes are very common.
Last edited by humphrey; 6th Sep 2008 at 10:35 am. |
6th Sep 2008, 10:48 am | #2 |
Rest in Peace
Join Date: Oct 2006
Location: North Wiltshire, UK.
Posts: 638
|
Re: Aerial capacitor
I think I would be inclined to use a good quality silver mica cap, commonly 500volt working, in that position.
Ian |
6th Sep 2008, 2:21 pm | #3 |
Hexode
Join Date: Jun 2008
Location: Burnham on Crouch, Essex, UK.
Posts: 391
|
Re: Aerial capacitor
If the aerial is struck by lightning, would any capacitor actually make much of a difference? I've never actually seen a TV or radio hit directly, but would think that the power there would destroy any capacitor (and quite a lot else!)
|
6th Sep 2008, 3:43 pm | #4 |
Retired Dormant Member
Join Date: Mar 2007
Location: Skelleftea, Sweden
Posts: 250
|
Re: Aerial capacitor
as lightning can bridge few hundred meters of air easily a few mm of plastic is neither here nor there. it is more a way to prevent static to get in (generated from wind...)
|
6th Sep 2008, 3:45 pm | #5 | |
Nonode
Join Date: Jun 2005
Location: Western Lake District, Cumbria (CA20) - UK
Posts: 2,136
|
Re: Aerial capacitor
Quote:
Direct strikes on radio aerials are not common though. I've never seen a radio after the aerial has been struck but I have seen several TVs completely destroyed that way - insides completely vapourised and much damage to house wiring. Of more concern is a nearby ground strike which will produce an electric field for a considerable distance. In that event a suitably rated capacitor of good quality and suitable rating might provide some protection. The most common form of lightning protection was to use a spark gap on the aerial lead-in with a connection to a good earth. I don't know how effective they were though. Regards, |
|
6th Sep 2008, 3:54 pm | #6 | |
Dekatron
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,684
|
Re: Aerial capacitor
Quote:
It may even be better (on the HF bands anyway) to use a 'static leak' inductor mounted permanently between aerial and earth, as used on some HF transmitters.
__________________
Regds, Russell W. B. G4YLI. |
|
6th Sep 2008, 4:47 pm | #7 |
Dekatron
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,684
|
Re: Aerial capacitor
Another use for a neon lamp?
__________________
Regds, Russell W. B. G4YLI. |
6th Sep 2008, 5:13 pm | #8 |
Nonode
Join Date: Jun 2005
Location: Western Lake District, Cumbria (CA20) - UK
Posts: 2,136
|
Re: Aerial capacitor
Yes, I've seen neons used in these applications.
The loop aerial I'm building at the moment has one across the input to the loop amplifier. Regards,
__________________
Brian |