Has anyone used a VNA to set up taps on an amplifier tank circuit or
used one to set up taps on a coil in a transmatch? Maybe a small
capacitor on the anode lead instead of the finals to match capacitance
and then measure from the output of the amplifier with antenna relays in
"on" position. (no other power to the amp
I am thinking that the caps can be set to expected mid band capacitance
for each band. Then work on the inductor taps to get the plate impedance.
Or should I just measure the inductor and make the taps based on the
inductance measurement? It seems that if the tank circuit parts were in
place the taps would be more accurate.
I am looking for a tutorial for non engineer types. (tards )
or a simple explanation. Step by step would be nice.
This is the hard part about making an amp? right? I mean besides the
drilling and metal cutting, and locating parts. Maybe others might be
helped as well by a good explanation.
Jim n2go

"James Skalski" wrote in message
news:gQ88f.5702$0V6.3968@trndny06...
Has anyone used a VNA to set up taps on an amplifier tank circuit or used
one to set up taps on a coil in a transmatch? Maybe a small capacitor on
the anode lead instead of the finals to match capacitance and then measure
from the output of the amplifier with antenna relays in "on" position. (no
other power to the amp

You bet Jim, ONLY way to do it! Put the tube in the socket, place a 1/4 watt
resistor plate to ground of the value of your plate load, stick the VNA on
the output port (Refl mode) and tune for maximum return loss. You should
readily get 40 dB to 50 dB, log the settings and you're all tuned up. (Don't
forget to pull the resistor before you apply power, although if you do, it
will remove itself in short order.)

You can measure the caps and place tap on the inductors where you get return
loss or measure the inductor and tune the caps for RL. Use the data in the
handbook for expected values for the plate load resistance transformation
and whether it's a Pi or Pi-L network.

Regards
W4ZCB

I have used a MFJ259 antenna analyser to set up amplifier tank circuits,
with the valves (tubes) left in place (but obviously without any power
applied to the unit)
Also antenna matching units ( I prefer NOT to use the word 'tuner') can be
set-up very easily with the above instrument.
I consider the MFJ259 an excellent instrument for radio 'amateurs' ,
suitable for lots of applications.

Frank GM0CSZ / KN6WH

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Has anyone used a VNA to set up taps on an amplifier tank circuit or used
one to set up taps on a coil in a transmatch? Maybe a small capacitor on
the anode lead instead of the finals to match capacitance and then measure
from the output of the amplifier with antenna relays in "on" position. (no
other power to the amp
I am thinking that the caps can be set to expected mid band capacitance
for each band. Then work on the inductor taps to get the plate impedance.
Or should I just measure the inductor and make the taps based on the
inductance measurement? It seems that if the tank circuit parts were in
place the taps would be more accurate.
I am looking for a tutorial for non engineer types. (tards )
or a simple explanation. Step by step would be nice.
This is the hard part about making an amp? right? I mean besides the
drilling and metal cutting, and locating parts. Maybe others might be
helped as well by a good explanation.
Jim n2go