[Amps] Input Impedance of GI-7BT Triode

[Steve Thompson]

On Sunday 14 September 2003 08:55, Mike Tubby wrote:
> The easiest thing to do would be:
>
> a) to guess
> b) take it to a friendly RF engineer who has a network analyser

A network analyser won't help without some messing, the measurement needs to 
be done at full drive level.

You can feed the amp through a ATU, tune for best match, then put 50 ohms on 
the transmitter end of the ATU and measure the impedance looking into the 
amp. end - that will give you the conjugate of the tube impedance.

Steve
>
> > I have recently completed converting an MLA-2500B to use the GI-7BT
>
> Triodes.
>
> > Thanks to a lot of hand holding by Lawson, W4EMF!
> >
> > Now, I am building WD7S's great little TU-7B tuned input board to allow
> > driving the amp with a modern tranceiver which does not have an
>
> auto-tuner.
>
> > I am wondering how to determine the input impedance of these tubes. 
> > Plate voltage is around 2300v.  I have the data sheet, but am not seeing
> > any reference to the input impedance since this is a tube designed for
> > pulsed microwave service.
> >
> > Any help would be much appreciated!
> >
> > 73 Kevin K7ZS
> > Portland, Oregon
> > k7zs at earthlink.net
> >
> >
> >
> >
> >
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