[Amps] Question on Ameritron amp wattmeter circuit

Guillermo nagato at arnet.com.ar
Mon Feb 10 20:27:54 EST 2003

	You may find that the center or pass through conductor in the toroid is
shielded, to avoid electrostatic coupling with secondary's transformer
and give a better higher frequency response.

Best regards
Guillermo - LU8EYW.

Floyd Sense escribió:
> Many thanks to all who replied on this question.  I adjusted the trimmer cap
> for minimum reflected power on 28 MHz, and it definitely was out of
> adjustment.
> I finally located my 1975 edition of W6SAI's "Radio Handbook".  He discusses
> the bridge circuit in detail and then goes on to describe the
> "reflectometer" circuit, which is  the scheme used in the Ameritron.  In the
> final paragraph, he explains how to adjust the capacitor in question.  It's
> interesting that in his reflectometer the toroid goes over a piece of coax,
> and also used a cylindrical can over the toroid as a faraday shield.  I
> suppose those precautions would make the sensor more frequency independent?
> In the Ameritron, the toroid simply surrounds a single unshielded conductor
> running from the T/R relay to the RF output connector.  I note quite a
> difference in power readings between the internal wattmeter and my external
> wattmeter on the higher bands.
> K8AC
> ----- Original Message -----
> From: "Floyd Sense" <sentek at sprintmail.com>
> To: <amps at contesting.com>
> Sent: Thursday, February 06, 2003 7:53 PM
> Subject: [Amps] Question on Ameritron amp wattmeter circuit
> >>snip<<
> > The question is: what is the function of the caps connected between the
> > center tap and the primary conductor?  I assume that the adjustment has
> > something to do with the calibration of the forward/reflected power
> meters,
> > but don't know how it comes into play.  There's a pot to ground connection
> > in each of the legs to calibrate the meters with.  Perhaps this variable
> cap
> > is used to correct the power reading at higher frequencies?
> >
> >>snip<<
> > K8AC
> >
> >
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