[Motorola] PT 400

[npalex at bellsouth.net]

Spencer,
Although I can not help you with a manual for the PT 400, I note that several of your responses have made suggestions on sources.  I did want to make one correction in the comments made regarding the transistor line-up in the PT-400.  Although his caution in powering the unit from an external supply is always a valid concern, and being aware of the polarity is a caution when supplying power to any electronic device.  

The PT-400 was an expansion of the portable "PACKSET" line of products of the mid 1960's.  As stated in the comments it has the circuits of the PT-300 and the HT-200DEN series radios.  The correction is in regards to the transistor line-up which was "silcon" based devices.  The predecessor to the DEN, was the DCN series which had germanium based transistors.  The HT-200 DEN series of products was all silcon based, and utilzed a unique "lay down" or "cord wood" component placement.  The purpose of the design of the DEN series was cost reduction, increased TX PO, improved reliability by employing "silicon" transistors and the stacked cordwood design.  The PT 300 DEN replaced 6 germanium devices in the PA of the DCN version with a single RCA silcon stud mounted device, more power (now 5w) and much lower cost and improve ruggedness.   The PT-400 was more the extension of the power craze of the 60's and feature another RCA device that could produce up to 15w, but reasonable or practical battery power was the limitation.  

It was a game of one-up's manship, primarily based on a horsepower race that was prevalent in that era, not only in cars, but two-way radios.  As a design engineer in Portable products at the time it was a period of virtually unlimited expansion as new and better semiconductors and other components where appearing almost weekly.  Lower cost, better reliability and performance were the incentives that prevailed.  I should include "Competition" as one of the key drivers as well.  

I had to look at  some of my patents for the HT and PT products issued in the 60's to peg the period of development.  I do recall the first public showing of the first HT-200 "DCN" model was in October of 1962 to the US Forestry Service.  That service and the railroads were the primary customers for the later release of the PT series PACKSETS.

Have fun with your PT-400's and you might find that the PA in that unit can become a compact 10w amplifier module that can be seperated and used independantly.  One of its features is a built-in SWR network that produced a control signal to cut back on the drive if a poor load was encountered.

73,
Norm W4QN
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Message: 1
Date: Sun, 03 Dec 2006 01:15:09 +0000
From: "Spencer Sholly" <kb5wqw at hotmail.com>
Subject: [Motorola] "Lunchbox" PT400
 
> Howdy!
> 
> I am new to the list.  basically, I just have some questions about the 
> PT400.
> 
> I obtained a couple of  these radios a while back & have put them up.  I was 
> curious if anybody has a source for owner's manual or schematics.  These 
> seem to have been set up for 2M operation.  I don't even know if they work.  
> The replacement batteries are like 135 bux apiece.  I can't spend that much 
> to find out the radios don't work.
> 
> Any help would be appreciated.
> 
> TNX es 73,
> 
> +++++++++++++++++++++++++
> Spencer G. Sholly <><
> KB5WQW
> Killeen, TX
> Our Church
===========================================================> 
> There is a different battery box for these which uses just a bunch of D
> cells, ..............
> 
> The radios can be tested by using just an external power supply, but be
> careful because they use Germanium PNP transistors and the polarity is
> backwards from what you think.  They expect about 14 volts.
> 
> The PT400 is basically a PT300 with an added-on transmitter power amp to
> give about 10 Watts, and the addition of a metering socket panel.  The nicad
> battery box has contacts on the outside end to allow dropping into a charger
> rack, which is not featured on the PT300.  The majority of PT400's seem to
> have been sold to the US Government.  The PT300 is actually an HT-200
> Handie-Talkie in a lunchbox housing with a power amp to give 5 Watts on
> transmit.  And, finally, the PT200 is just an HT200 in a lunchbox.
> 
> If you do some searching on the net, someone somewhere had a schematic of
> the battery box and the power wiring on his website, I just don't recall
> where I saw it.
> 
> 
> Geoff
> WB6NVH>