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Title: Where do I find shunts for Johnson Transmitters Post by: Knightt150 on July 16, 2011, 02:08:26 PM I am in need of some shunts for a VALIANT and RANGER transmitters. I have looked in mouser but can't find .2021 ohm or .4042 ohms shunt resistors W.W. I think means wire wound on the shematic. The other values seem to be reasonable 2.2, 5.1 ohm the 20 and 3 ohm ones could be purchased from mouser.
John W9BFO Title: Re: Where do I find shunts for Johnson Transmitters Post by: WD8KDG on July 16, 2011, 03:19:55 PM John,
Don't have a parts list close by for the Valiant or Ranger. But, by memory and the Junkston 500, EF Johnson used 5% wire wound resistors. Mouser has 1% wire wound and should have something very close to what is listed in the parts list for the V or R. Craig, Title: Re: Where do I find shunts for Johnson Transmitters Post by: W2PFY on July 16, 2011, 03:54:39 PM I think some people roll their own for these shunts.
Title: Re: Where do I find shunts for Johnson Transmitters Post by: Jim, W5JO on July 16, 2011, 04:14:03 PM If you find a resistor within 10% you will be good to go. Meters of those days looked for 10% accuracy anyway. Mouser does have some 1% WW resistors that are near the values you need. I have purchased from them in past years.
Title: Re: Where do I find shunts for Johnson Transmitters Post by: Pete, WA2CWA on July 16, 2011, 04:20:18 PM From our own archives (Search - meter shunts)
Valiant meter shunt?: http://amfone.net/Amforum/index.php?topic=27987.0 Building meter shunts?: http://amfone.net/Amforum/index.php?topic=26097.0 meter shunts: http://amfone.net/Amforum/index.php?topic=8510.0 Lots of valuable data in our Archives: http://amfone.net/Amforum/index.php?action=search Title: Re: Where do I find shunts for Johnson Transmitters Post by: KM1H on July 17, 2011, 12:33:15 PM The Viking I and II used a combination of commercial resistors and air wound wire shunts.
Carl Title: Re: Where do I find shunts for Johnson Transmitters Post by: gerry_w1id on July 18, 2011, 12:06:16 PM As someone else said, the meter movement probably isn't that accurate to begin with. I would select a 1% WW resistor close to the value listed on the schematic. You can also parallel other resistors with your new shunt to get an exact value. I would avoid any carbon composition resistor or home-made shunt made from copper because of poor thermal performance and unpredictability. However if you insist on winding copper, please make sure you take the resistance of the leads, or clip leads used to make your resistor. 0.2 Ohm sounds like the resistance of a pair of test leads. Some meters allow you to tie the test leads together and hit a reference button to zero out lead resistance.
Title: Re: Where do I find shunts for Johnson Transmitters Post by: KZ5A on July 19, 2011, 09:04:10 AM Mouser PN 588-43FR20E is a .2 ohm, 1%, 3W, WW.
Should be close enough for "government work"......... ;D 73 Jack KZ5A Title: Re: Where do I find shunts for Johnson Transmitters Post by: Knightt150 on July 19, 2011, 03:02:34 PM Thanks for the posts and all the help on this, It is getting kinda hard to see that mouser book anymore. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
John W9BFO |