[AMRadio] need help

John Coleman ARS WA5BXO wa5bxo2005 at pctechref.com
Wed Oct 19 09:31:25 EDT 2005

Depending on how critical your rice box is about having a pure 50 ohm
load on it and the amount of voltage required at the grids of the
amplifier, you may want to use a small tuner between the two but nearest
the amp. If a less critical amount of match is required a balun or .25
wavelength 75 ohm ooaxial cable match might be used.


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Edward B Richards
Sent: Tuesday, October 18, 2005 10:27 PM
To: amradio at mailman.qth.net
Subject: [AMRadio] need help

Hi, you guys who are better educated than I. I want to drive a linear
amplifier with a rice box that requires a 50 ohm load. The linear amp
uses an input to a 170 ohm, 80 watt swamping resistor to ground, then
through a .001 mfd capacitor, then through a VHF parasitic suppressor
consisting of  4 turns of wire around a 47 ohm resistor, to the grids of
a pair of parallel connected 4-400A tubes.

What I need to know is the impedance of the input. Is it close to 50
or do I need to use a matching network between the rice box and the
linear amplifier. Thank you.

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