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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