Archive for October, 2016

TR Switches for Vacuum tube transmitter and receiver hook-ups

October 31, 2016

Before today’s modern transceivers,  radio amateurs used separate transmitters and receivers.  They were usually very large,  vacuum tube designs,  developed a lot of heat, and were quite a bit more sensitive to drift, filtering, hum, and adjacent channel interference.

Many amateurs continue to “work” with these designs for many reasons.  If you build a transmitter kit such as we offer on our web site, you have to figure out how to connect it to a receiver and be able to share a common antenna.

It’s really fun to connect it with a ‘modern’ tube type receiver, such as the Collins, Hallicrafters, National, Drake and others.  EF Johnson sold a automatic switching TR switch, model 250-39 which worked very well.  Do a search on the internet for more information.  There are come up  for sale occasionally; be careful – the condition of older equipment is always a concern.

Pastime projects is working on a new TR switch for use between vacuum tube type transmitters and receivers.  “New” is not the proper term, as our design will be very similar to a published design from the 1960’s.  We have a couple prototypes on the bench. We also have a rebuilt Johnson Model for reference.  Watch for introduction on our web page soon.  As always, write if you have comments.  73 Glenn W8JZI  or  pastimeprojects(at)yahoo(dot)com

Just a final thought:  These designs use a vacuum tube as a switch and switching between a low to moderate powered tube type transtmitter and a vacuum tube type receiver is automatic.  Makes for very smooth transition. This is not a mechanical relay system which requires manual switching…