The schematic shows a 7805 regulator for the logic board. The minimum
voltage for the 7805 is 7 V, so it should be OK.
The RX/control board uses an LM 2940, which is a low dropout regulator.
However, it is prone to instability under certain conditions, according
to the data sheet. The regulated output to the RX/control is 10 V and
the minimum input is 11.5 V, so a weak battery plus a little voltage
drop in the power cable can spell trouble. Increasing the value of C22
(33 µf. The data sheet specifies 22 µf minimum, with low ESR, and no
maximum capacitance limit) may help.
It is also important to reduce voltage drop in the power cable and
connector. Make sure that the power connector pins and sockets are clean
and tight. Also, replace the spring-loaded in-line fuse holder with an
automotive blade type.
I usually run my Scout at 30 W output and have had no problems running
it on battery power. A 7 Ah gel battery will run it for a couple of
hours. For longer duration, I use an automotive jump starting battery.
I did have a problem once with a corroded crimp connection on a power
cable that caused a voltage drop which sent the Scout VFO drifting
several kHz down the band.
I can try an experiment with a variable supply and listen with a
separate receiver to see if the CW note gets chirpy at lower voltages.
73,
Bob WB2VUF
On 4/28/2015 12:44 PM, Rick - DJ0IP / NJ0IP wrote:
Bob, I was a business manager, not an engineer.
One of the things I learned how to do in business school was to use my
resources and to delegate. (hi)
I already have the designer of that radio looking into it for us and he is
usually very good at solving problems like that. He's as stubborn as me,
but smarter.
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Katz Ajamas
Sent: Tuesday, April 28, 2015 6:37 PM
To: Discussion of Ten-Tec Equipment
Subject: [TenTec] Rick's Scout and Low Dropout Reegulators
Dear Rick,
Have a look using the search term, "low drop out" regulator. Mouser and I'm
sure the others have a wide selection. Specs are much better than the old
three terminal jobs.
73, Bob ah7i/w4
------------------------------
Message: 8
Date: Tue, 28 Apr 2015 16:12:51 +0200
From: "Rick - DJ0IP / NJ0IP" <Rick@DJ0IP.de>
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Subject: Re: [TenTec] OT: Anyone used LiFePo technology yet for
portable operations?
Message-ID: <011a01d081bd$6a6b18b0$3f414a10$@de>
Content-Type: text/plain; charset="us-ascii"
I just had an email with the OM who designed the Scout.
He is no longer with Ten-Tec, but I'm sure many of you know who he is.
He agreed that a lower loss regulator would help and he promised to
take a look at it.
Perhaps he will suggest something.
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
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