[ARC5] A Chicken Band "Leaner Applefryer" for Our Rigs

[Tim]

Hi Jay - Yes, it is the EB-63 amplifier. It was developed by Motorola as a
test bed for the MRF-455 transistors.  Someone (CCI?) marketed a kit to
build them, supply your own heat sink.  With proper input and output
filters,T/R relay and controllable bias circuitry they work quite well.
2-30 MHz.  I think it was rated at 140  W output.....Mine did...
Tim
N6CC

On Sun, Dec 16, 2012 at 11:36 AM, Jay Coward <jcoward5452 at aol.com> wrote:

>
> Dave and All,
>  There was an article published in Electronic Design magazine about 20+
> years ago for an HF amp useing those MRF 455's.There was a pcb and kit of
> parts available but no heatsink or enclosure. I think it needed around 20A
> @12V for 160W out.
> Jay
>
>
>
> -----Original Message-----
> From: David Stinson <arc5 at ix.netcom.com>
> To: milsurplus <milsurplus at mailman.qth.net>; ARC-5 List <
> arc5 at mailman.qth.net>
> Sent: Sun, Dec 16, 2012 10:31 am
> Subject: [ARC5] A Chicken Band "Leaner Applefryer" for Our Rigs
>
>
> The little RCA AVR/AVT rig is running well
> or hours at a time and I've been using it
> or QSOs and nets, so I've set the vibrator problem
> side for now and am concentrating on something
> that will help with this and several other rigs.
>  will get back to the vibrator... honest (crossed fingers).
> Getting these SCR-183, SCR-288 and Light Aircraft HF sets
> orking is a lot of fun and I've made many QSOs
> ith them "as-is," but there are a lot of times when 3-8 Watts
> in't gonna "cut it."  So I got hold of a Chicken-Band so-called
> 150 Watt, two-pill Leaner" and decided to make
>  "foot-warmer."  The trucker won't miss it.... I hope....
> Very common bipolor P-P amp with a pair of MRF455s.
> his thing is a real "piece of work"   (eye-roll).
> o bias- it ran hard Class-C.
> o base stabilization.  No output low pass filtering.
> ny signal so unfortunate as to find itself forced
> o drive this train-wreck came out
> ounding like a water buffalo gargling Drano.
> The first step was to stabilize the bases and bias the thing linear.
>  used .004 at the bases.  Yes, I know that's alot.
> 'm trading output and drive ease for stability and that settled
> he thing down just fine.
> Next, biasing the thing linear.
> irst thing that had to go was the wienie RFC in the
> ase circuit.  It was like 220 uH and, at 3.9 MC,
> ight as well have been a short.  I replaced that with
>  manly, non-potted, non-ferrited 1 mH CHOKE
> s the Good Lord intended!
> (Everything following bypassed for RF, of course)
> sed a voltage divider down from the +12 V supply,
> 3 Ohms 10 W  and 5 Ohms in series, the 5 Ohm
> onnection point clamped with a power diode to ground
> t one diode drop, about .7 volts and the bias picked-off
> t this point.  This worked, after a fashion.  The amp was
> airly linear and the transistors, being mostly always on,
> ot just a touch warm.   There sure was a lot of  power
> etting wasted as heat in that divider.
> Next I tried an adjustable voltage regulator through
> eries diodes.  Amp looked best at about .9 volts bias,
> ut the transistors were "on " harder and got a little
> armer.  No "scary" warm but still.
> So I tried another divider, but this time with 2-ohms
> efore the clamping diode to provide just a touch more
> orward bias than one diode drop.  That divider still
> ot warm.  Until I touched it during a test and it was cold.
> urned-out my lead that provided the +12 to the divider
> ad fallen-off and the base circuit was self-biasing
> t about 1 volt full drive.  Transistors run a little warm
> ut not alarming and the linearity is pretty good- acceptable.
> nd no heat/wasted power in a divider.
> Here's the circuit:
> http://home.netcom.com/~arc5/AVRAVT/newbias.jpg
> OK, Smart People:  Why is this working?
> My antenna tuner is being my LPF for now.
>  "real" filter set is next.
> 73 DE Dave AB5S
>
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