[TenTec] Rick's Scout and Low Dropout Reegulators

[Rick - DJ0IP / NJ0IP]

Bob, I THINK YOU JUST NAILED IT!

THANK YOU.

I will swap the capacitor you referred to.
Gotta find a place to buy one, first.  I live a couple hundred miles from
the nearest ship.

I already built my own power cable and use the Airpax 9A circuit breaker.
I have planned to only run 25 to 30w.  Not more.

I ran my Argonaut 509 and 405 amplifier at this power level for nearly 20
years.  It saved current drainage from my motorbike's battery and I found
that with a good antenna, I could work the world with it (in CW of course).

In fact, I found that with 10w CW or 30w SSB, I had no problems working
efficiently with it.
CW would still work "OK" (not great) with 5w, but SSB was a drag at that
power level.

So in summary:
 > Replace C22
 > Run short, fat battery cable
 > Solid connection to fuse or circuit breaker
 > Use LiFePo battery

and I'll be in business.

If you got a couple of hours out of a 7Ah GEL, I should be able to get 5 or
6 hours out of a 12A LiFePo.  And that will be more than enough.

So I am 2 steps away from operation:

1.  Prepare all of the above
2.  Ready boots, start walkin'
(hi)

73 - Rick, DJ0IP
(Nr. Frankfurt am Main)

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Bwana Bob
Sent: Thursday, April 30, 2015 3:50 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Rick's Scout and Low Dropout Reegulators

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 at 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 at DJ0IP.de>
>> To: "'Discussion of Ten-Tec Equipment'" <tentec at 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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