Hamfest find

[Mike Kelly]

Wandering around a Hamfest yesterday I spotted this U.S. Signal Corps. IS-89 RF current meter. I recognized it as being a antenna current meter for the BC-191 transmitter, for $2 how could you leave it on the table. My BC-191 is a long term project, spares are handy.

Very much a 1930's era mobile army transmitter, the 191 was big, heavy and crude but at the time, the U.S. army 'modus operandi' was, in order to get the message through - keep it simple with loads of power. I find it hard to believe the 191 were kept in production right up to 1945. With a BC-191 set up in your vehicle, the current draw from the battery system was around 50 Amps ! And, the genemotor or dynamotor supplied 1000V at 350ma, no second chances if you manage to touch that !

A good history of the BC-191 https://aafradio.org/garajmahal/BC-AA-191.htm

The hefty 211 Triode tubes as used in the BC-191 are now sought after by the audio Hi-Fi crowd, the price for these tubes has skyrocketed to silly levels. Demand for audio tubes in general is to the point where they are now being manufactured in China. The older brands like the G.E. 211 tube can reach prices over $300 U.S.

New 211 tubes are currently being made in China are available on Epay

https://www.ebay.com.au/itm/26555200...CABEgJomPD_BwE

A history of the 211 tube , the author writes that the old original brands are far superior to the current Chinese repro tubes on the market.

http://vinylsavor.blogspot.com/2012/...-211-vt4c.html

[Philliphastings]

Hi Mike,

If I went to a Hamfest these days I’d spend all my money !

A portion of my military radio gear is now part of a Museum in Western Australia but I’m still collecting and restoring.

I read recently that Russia may be a viable source of replacement valves. A couple of years ago I bought a box of toggle switches which fitted perfectly in a ex Army truck I was working on.

Cheers

Phill

[Mike Kelly]

Originally Posted by Philliphastings

I read recently that Russia may be a viable source of replacement valves.

Cheers


Phill

Yes, the russkies kept vacuum tube technology in service long after the West had gone over to solid state technology. https://www.milkenreview.org/article...n-vacuum-tubes

The article doesn't mention Eimac , this San Francisco company was founded by two hams in the 1930s, it is now only a shadow of its former glory days, but is still filling a small niche market, making tubes for US military radar systems and radio broadcasting. The local ABC FM transmitter here on Mt. Tassie has Eimac tubes fitted !