[Boatanchors] Re: Boatanchors Digest, Vol 40, Issue 3

[Roger Basford]

Hi Dave & Guillermo,

Thanks for the info and suggestions. It looks like the project should be an 
easy one, I think the design I saw previously probably incorporated some 
sort of SWR sensing, I don't need that. I've also been sent an article 
written by G4DDI giving details of toroids and sources.

Thanks again to you both,

73,

Roger/G3VKM


----- Original Message ----- > Date: Thu, 3 May 2007 10:38:28 +1200
> From: "Dave Brown" <tractorb at ihug.co.nz>
> Subject: Re: [Boatanchors] RF current sensor
> To: <boatanchors at mailman.qth.net>
> Message-ID: <0e8b01c78d0a$9b139650$7900a8c0 at athlon1200>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=response
>
> Roger
> It certainly would be OK.
> Put as many turns as you can easily- number of turns not critical in
> your case as calibration is not an issue- on the toroid and load the
> winding with a shunt resistor. A series diode from one end of that
> winding to the meter and a cap across the meter (say 0.1 uF) with the
> other end of the winding going to the other meter terminal. Add series
> resistance between diode/cap junction and meter terminal if needed -
> maybe a pot- and/or juggle the shunt resistor on the toroid winding to
> get whatever reading you want on the meter.  The toroid is threaded
> onto the conductor you want the current indication from, of course!
> The resistor values to use will depend on the sensitivity of the
> meter movement and the rf power in use- all values non critical in
> your (uncalibrated) case.  Try 4k7 across the winding for starters
> (assuming say 100 watts rf) and maybe a similar value pot to set the
> meter reading as required.  Be aware that the reading will be
> frequency dependant-you can reduce this effect by keeping the shunt
> resistor across the winding as low as possible.
> 73
> Dave, ZL3FJ
>
>
> Message: 7
> Date: Wed, 02 May 2007 19:52:16 -0300
> From: GGLL <nagato at arnet.com.ar>
> Subject: Re: [Boatanchors] RF current sensor
> To: boatanchors at mailman.qth.net
> Message-ID: <46391620.7080503 at arnet.com.ar>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> May I add something?. The readings will be more accurate at higher
> frequencies if you put a faraday shield between the conductor and
> winding (sort of coaxial cable, center hot, shield to ground AT ONLY ONE
> end) to diminish capacitive coupling.
>
> Best regards
> Guillermo - LU8EYW.
>
>




-- 
No virus found in this outgoing message.
Checked by AVG. 
Version: 7.5.467 / Virus Database: 269.6.2/787 - Release Date: 03/05/2007 14:11