[Milsurplus] [MMRCG] GO-9 Progress Report. 4 Nov 19, First Contact

[Ray Fantini]

Going to assume that the TBW and the GO-9 are just about the same radio except that the TBW was intended for field use and includes suppressor modulated AM. On my TBW I found that the output tank was well designed and as long as the grid of the PA was not hit too hard it would easily put the 2nd and third harmonic at least forty five to fifty dB down. For what I had assumed a transmitter designed for feeding high impedance loads would do into 50 ohms it was not half bad.
The original specifications were 2.0 kV at 165 mA for an indirect power of around 300 watts and figuring most class C amplifiers chug along at least 70 to 80 percent let's just say for fun 75% that would give you around 225 watts.

1.4 kV @ 175 mA =225 watts, lets figure 80% efficient is just under two hundred watts. Westinghouse or whoever built that one over designed the output tank and antenna tuner to the extent that that radio can take that power level and then some all day long. Although there may be some issues banging the tube that hard. Just looked at the RCA manual and it says that in class C CW service you should run it at 2.0 kV plate, 600 volts max G2 with a recommended maximum plate current of 175 mA that gives a input power of 350 watts! Watch out though, this is the CW rating and the class C high level modulation drops down to just 1.6 kV, also watch that control grid drive because it looks like 20 mA may be max at that plate voltage and from what I recall the IA will develop tons of grid drive.

Like I said before, do not think you can kill a 803 but maybe if you try you can be an example for all of us!

Ray F/KA3EKH

-----Original Message-----
From: Kenneth G. Gordon <kgordon2006 at frontier.com> 
Sent: Tuesday, November 5, 2019 1:01 PM
To: Ray Fantini <RAFANTINI at salisbury.edu>; MMRCG at groups.io; milsurplus at mailman <milsurplus at mailman.qth.net>; David Stinson <arc5 at ix.netcom.com>
Subject: Re: [Milsurplus] [MMRCG] GO-9 Progress Report. 4 Nov 19, First Contact

On 5 Nov 2019 at 8:21, David Stinson wrote:

> I ask because I don't
> believe my test equipment.  Even the venerable 803 isn't going to be
> 90+% efficient as a Class-C amp, so I think both my scope and 
> 90+wattmeter
> are lying to me.

Well, the 803 is a darned good tube, but you're right: it cannot be 90% efficient in any class. 
As far as your wattmeter is concerned, remember that it measures total power output, including that from any harmonics. That may be part of the problem.

Otherwise, I suspect operator error. ;-)

Ken W7EKB