Carl and the group, When the Scout was designed, there were 3 terminal regulators that required a larger differential of voltage to regulate stability, than the low drop out regulators that came late
Author: geraldj@isunet.net (Dr. Gerald N. Johnson, electrical engineer)
Date: Fri, 01 Nov 2002 17:42:00 -0600
Why should the PA draw MORE current on low voltage? If its being driven for all the impedance matching transformer can do, then the load line resistance is constant with supply voltage and the curren
Right, right Jerry, on PA, I was not thinking of that; I am not sure what I meant. Doing two things at once here! Hi! If they already have the LDO's then, there is just a lower limit at 12! I know my
Author: geraldj@isunet.net (Dr. Gerald N. Johnson, electrical engineer)
Date: Fri, 01 Nov 2002 19:22:27 -0600
Its easy for a bit of excess voltage drop in fuses and back panel connectors (I seem to recall some comments in the past about those back panel connectors being a real problem in some Scouts) to drop
My Scout came from the factory with a low dropout regulator. I think that it is a 2940 chip which drops out at 11 V. Is there a 10 V regulator with a lower dropout than that? 73,
Author: geraldj@isunet.net (Dr. Gerald N. Johnson, electrical engineer)
Date: Mon, 04 Nov 2002 20:14:27 -0600
What is the lowest voltage your "low voltage" scout will run on? 73, Jerry, K0CQ -- Entire content copyright Dr. Gerald N. Johnson, electrical engineer. Reproduction by permission only.
Mine starts to drift at 11 volts or less. I think inside, a number of the circuits run on an 8 volt bus, which seems to jibe with your observations about voltage regulators. My Scout is fine at 12 vo
Author: geraldj@isunet.net (Dr. Gerald N. Johnson, electrical engineer)
Date: Mon, 04 Nov 2002 22:39:40 -0600
Then those Scouts that drift at 12+ volts could be helped by changing to that LM2940 chip. Maybe in Mouser, 511-L4940V10 for 10 volts output. To replace LM7810 in TO-220 package. 73, Jerry, K0CQ -- E
Last night I set down with my Scout schematics and found they do have the low drop out LM 2940 in mine, (some 7 plus years old). Mine does not drift at 12 volts, (and I know of none that do). Down ar
I think that the 2940 regulator needs 11 V minimum, but there are lots of places for voltage drop ahead of the regulator: The power cable, fuse and fuse holder, power switch, power connector, and the
Author: geraldj@isunet.net (Dr. Gerald N. Johnson, electrical engineer)
Date: Tue, 05 Nov 2002 20:51:09 -0600
The classic LM7810 needs 2 to 2.5 volts minimum drop. When the input voltage gets too low, the regulator acts as a constant voltage drop, so any ripple on the input shows on the then unregulated outp
Good thoughts Bob, on added loss areas for the Scout power. I usually use larger wire than any supplier uses for transceivers. Kenwood is the only one usually adequate to my preferences. 73, Stuart K