<3A31C5EE.8493D923@att.net> <020501c061a8$177ad5e0$7cd9243f@fkxug>
<3A33B58A.7556@ames.net>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: owner-tentec@contesting.com
Precedence: bulk
X-Sponsor: W4AN, KM3T, N5KO & AD1C
Actually, the Scout does have an LM2940-10 regulator for the PTO, which
should have adequate headroom. The regulator should be good down to 11
V. The Scout owner's manual specs an operating range of 12 to 14 V.
If the input voltage drops too low, the PTO goes unstable and starts
drifting and you may experience FM modulation when operating SSB.
I plan to do a test someday to see exactly at which voltage this occurs.
I had the problem myself when operating off a car battery. I later
discovered that a crimped power connection that I had made had corroded
and come loose in the engine compartment. Now I solder all lugs and
cover them with shrink sleeving or RTV. I also made sure that the ground
connection was solid. In short, every effort must be made to assure
mininum voltage drop in the cables and connectors.
Another solution to the portable power issue would be to get a 12 V gel
cell and then add an additional single cell to provide 14 V. Single 2 V
gel cells are available. 14 V is still low enough to be charged by most
solar panels. One manuafacturer (I think it was Gates) at one time
offered a portable 14 V battery pack, but I believe that most of the
commercially available packs are 12 V. Still, if you need power in the 5
amp-hour range, the additional cell appears to be economical. Mr. Nicad
http.www.batteriesamerica.com offers a 5 amp hour single cell for
$ 7.95.
73 all,
Bob WB2VUF
"Dr. Gerald N. Johnson, electrical engineer" wrote:
>
> Sounds to me as if the Scout has a 7810 or LM340-10 regulator for the
> VFO. That regulator needs about 2.5 volts headroom input to output to
> maintain regulation. Very likely the TO-92 version 78L10. I have no
> Scout and no scout manual to see. Perhaps that regulator could be
> replaced by a LM2937ET-10 or LM2940-10 or a series resistor and a TL431
> family programmable zener diode. The LM29xx family works with down to
> 0.6 volts drop, the TL431 would work lower though a bit less efficiently
> than the series regulator. The TL431 programmable zener diode is a far
> better regulator than any plain zener diode.
>
> 73, Jerry, K0CQ
--
FAQ on WWW: http://www.contesting.com/FAQ/tentec
Submissions: tentec@contesting.com
Administrative requests: tentec-REQUEST@contesting.com
Problems: owner-tentec@contesting.com
|