Kevin,
Good point about the change in the metering circuit between the Scout and
556. Of course, I had overlooked that. I wonder, do you remember if the
board in your 556 has the cut out for the finals plus heat sink? Or is it a
fully rectangular board. I had imagined they would use the same PCB for
both models, but it does make the 556 a bit more sturdy to have a
rectangular board filling the unused finals space.
I would think they could use final shut down protection on the driver/
final, as well as on the high power final. The simplest would be the use of
a zener to protect against overvoltage on the collector of the driver. I
will have to look up what they do even for the 50 watt module.
Thanks for calling that further difference to our attention.
-Stuart
K5KVH
----- Original Message -----
From: "Kevin Anderson" <k9iua@yahoo.com>
To: <tentec@contesting.com>
Sent: Friday, July 13, 2007 11:09 AM
Subject: Re: [TenTec] Argo 556/Scout modules
Stuart wrote:
In interesting fact is you can remove one 12 volt wire,
and swap one coax jumper, and make a Scout into a 556, 5 watt
radio, very quickly. The 5 watt 556 was just a Scout running
with only a driver transistor and no two transistor final.
The
same modules provide the Band Pass filtering for the output
signal.
I have both a 555 and 556. While what you say is true, there is
actually a production difference between the two radios. I
can't remember which board specifically (I'm at work and the
radios and manuals are at home), but the 556 actually has a
different board in it to make it a true 556. The primary change
on that board is in changing the meter so it reads full scale on
5 watts (i.e., 50 on the meter equals 5 watts).
While I like the 556 I have, and will keep it, the one negative
that I can see when compared to the 555 is that without the
finals of the 555, the driver transistor of the 556, now the
final, has less protection. When it fails, the entire radio
will fail. In return for this loss of protection, the power
consumption of the 556 at full power is considerably less than a
555 turned down to 5 watts.
Cheers/73,
Kevin, K9IUA
--
-------------------------------------
Kevin Anderson, Dubuque IA USA, K9IUA
k9iua (at) yahoo (dot) com
http://postoilgeography.blogspot.com/
-------------------------------------
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