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RE: LF: Re: Static effects

To: [email protected]
Subject: RE: LF: Re: Static effects
From: "Talbot Andrew" <[email protected]>
Date: Wed, 20 Jun 2001 10:43:58 +0100
Reply-to: [email protected]
Sender: <[email protected]>
But much better still a bleed choke, making sure the inductance is high
enough not to affect the matching.  A good choke would be made from a
ferrite core and as it is not carrying any power a smaller core can be used
than would be the case for a matching transformer.  Make sure there are
enough turns to not saturate the ferrite with the highest RF voltage
present.  Saturation was almost certainly the case in an earlier posting
where a choke 'got hot'.
Use the formula    Vrms = 4.44.F.N.A.B   to calculate the Minimum turns
needed on any given core, using a B of around 0.1 Tesla for a good safety
margin.   All non-gapped ferrites designed for SMPSU transformers will have
more than enough inductance - up in the tens to hundreds of milli-henries -
when wound with enough turns to satisfy this equation.

Andy  G4JNT

-----Original Message-----
From: Tom Boucher [mailto:[email protected]]
Sent: 2001-06-20 08:40
To: [email protected]
Subject: Re: LF: Re: Static effects

Dave G3YMC wrote:
>If you feed your antenna, as many do, via a matching transformer (3C85 core) >then the >antenna and the line to the tx/rx will be automatically grounded. Another >advantage
>of this method of feeding antennas.

Well I do Dave but I have rather an odd T/R relay arrangement based on
single pole on/off relays which I had available. This means that when Tx supply is switched off, the antenna is connected to neither transmitter
nor receiver.

I didn't fit a bleed resistor as Andy suggests because I figured it
would have to dissipate a fair bit of power unless it was a high value, however even a high value will be adequate to discharge any build up of
static, I guess.

73, Tom

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