[BC] Old tube kW rigs

[W2XJ]

Prior to the 4-400 designs many transmitters used 833s. The Collins design was robust and got years out of a set of tubes. As you mention, the Raytheon design was also robust. Continental also had a good TX design. Most Gates/Harris gear was crap regardless of tube compliment. I did buy an MW 50 C-3 but that was after Bob Wierather cleaned things up somewhat. You know there is a problem when even the designer (Hilmer Swanson) was upset with the weird things production did.  


   
Sent via BlackBerry from T-Mobile

-----Original Message-----
From: "John Lyles" <jtml at losalamos.com>

Date: Tue,  2 Sep 2008 16:28:59 
To: <broadcast at radiolists.net>
Subject: [BC] Old tube kW rigs


Some of the comparisons of 833A and 4-400A tube rigs here show that we all have diverse opinions. What I offer here is gross simplification, so here goes....There were several variations of tube 1 kW transmitters: the Gates triode boxes, the RCA/Collins/Bauer/McMartian/CCA/Wilkinson/etc tetrode boxes, and stuff that didn't fit into these two categories like the linear amplifiers (RCA and Gates Vanguard), and very old systems like Western Electric (Doherty), older RCA stuff, and whatever I missed.

The Raytheon RA1000, while it was a quad 833 rig, was completely different in design as it had conventional class B pushpull audio, modulating push-pull RF stages. All the rest used parallel RF tubes, with lower plate impedance as the result. Instead of 807s driving the 833 grids, the big RA1000 had 813s in there. It was overdesigned, no value engineering. The RF circuit was all symmetrical with a variometer for the output link to coax.

Gates stuck with a design and repackaged it for many years. The basic 833 design that they used was gutless.

It really makes a difference when hams get these old boxes and try to move them up in frequency. The long straps and wires of the 833 connections, and lack of nearby low L grounding, really limits what can be done with a Gates. Some of the tetrode boxes seem to get pushed to 7 MHz at least.




~_____________________________________________________________________~
The BROADCAST [BC] list is sponsored by www.SystemsStore.com
The Preferred Source For NEUTRIK & SWITCHCRAFT Connectors
Tools & Supplies To Build and Maintain A Technical Infrastructure