Subject: [Boatanchors] FS: EF Johnson 250-39 Electronic T-R Switch _______________________________________________________
This little unit that Bob has is a really useful item for boatanchor users. I have two of them, one hooked up to my Viking Valiant, the other is a spare for the moment. A perfect use for these little guys is full break-in cw -- before I got the Valiant I used a Gonset GSB-100 with a Hammarlund HXL-One amplifier and the TR switch -- again, worked great. And yes they have a little gain. You can make yours have more gain by increasing the number of turns in the secondary of the little ferrite core "receiver output transformer" inside the unit. The little units do make a surprising amount of heat, which is why Johnson put them in TVI-proofing metal housing with lots and lots of holes for air circulation. And using the 6BL7 is important -- there are "same base pinout substitute tubes" that're easier to find, but the voltage rating(s) of the 6BL7 mandate it for use with high power. Whomever has a use for it and gets it should be well please. I'm extremely pleased with mine ! Mike/ K5MGR __________________________________ Mike Langner 929 Alameda Road NW Albuquerque, NM 87114-1901 (505) 898-3212 home/home office (505) 238-8810 cell [email protected] _______________________________________________ Boatanchors mailing list [email protected] https://puck.nether.net/mailman/listinfo/boatanchors
