[Johnson] Questions about the E.F. Johnson Courier Amplifier

[Guy Olinger, K2AV]

It is a single ended grid driven pair of 811A's with a neutralizing
capacitor and all that.

It will run either in class C for CW or class B for SSB/AM. Covers 3.5
to 30 MHz continuously.

It has a tuned grid circuit. Knob is on the front panel and checking
the peak is part of the tune-up for each QSO.

You can record the settings and tune it by the numbers. Bandswitch and
four knobs. The pi net tuning cap and coil are ganged together on the
large control and continuously tuned across the range. The loading Cap
is a seven position switched coarse, and a continuous fine in
parallel.

It has no ALC and you must reduce drive on most rigs. It is a good
match for a Ranger on CW (single mildly driven 6146) which has about
the right amount of power to drive it to full output in class C. It
puts out about 350 watts with about 450 watts plate input. Something
like 70-75% efficiency with a good pair of 811's.

In Class B, I was able to get almost 300 watts out driving it with my
12 watt Elecraft K2.

It is not really suited for AM linear following the Ranger, which
would need to be cranked back to 8-10 watts out to keep from clipping.
(In comparison, the Ranger at full output AM easily drives my AL1200
to max legal, 1500 watts AM peak and 375 watts idle carrier.

All switching must be done externally on an unmodified Courier. No ALC
unless added later on.

Only about 400 of these made.

I have one to go with my Ranger.

One of these days (months, years?), I'm going to build an external
keying/switching circuit with pin diodes, etc, to run full QSK with
the Ranger, the Courier and my 75A3. That would be including keying
shaping, switchover delays and RX muting & AGC clamping to make it
sound good in the RX.

Hope that helps,

73, Guy


----- Original Message ----- 
From: "Sherrill E. Watkins" <SEWATKINS at dgs.state.va.us>
To: <johnson at mailman.qth.net>
Sent: Monday, June 14, 2004 4:06 PM
Subject: [Johnson] Questions about the E.F. Johnson Courier Amplifier


Gentlemen: Can someone kindly inform me if the Courier Amplifier is a
grid driven or a cathode driven design? Does it use a tuned input
circuit? Does the Courier also incorporate an ALC circuit? I really
appreciate all the very informative comments I have received from the
members of this list! Thank you in advance! 73 - Sherrill E. Watkins,
K4OWN .