[Heath] SB-200 and AM

[Kenneth G. Gordon]

On 19 May 2018 at 20:15, jerrylofstead at bellsouth.net wrote:

> AH HA.  Ididnt realize that...  I used that for several years.  I also used screen mod.  before i 
> could afford a BC191 mod.  transformer.  Only used surplus eqpt for my early years.

So have I, Jerry. :-)

BTW, in my personal opinion, Controlled-Carrier AM has a lot to recommend it, although it 
does have a fault or two.

I'll list some of the reasons I think it is an excellent method.

1) It requires no "heavy iron" to implement it. It requires as few as 2 tubes. The circuit is 
actually very simple. I like "simple".

2) Its output characteristics make it very suitable for driving almost any linear amp.

3) If you as the user very carefully zero-beat an SSB station with your "carrier", that SSB 
station seldom realizes you are on AM. Using VOX or some rapid TX/RX method, like a 
foot-switch, makes this even more "friendly".

4) The circuit takes up very little chassis space and can be incorporated into many simple 
transmitters.

5) It can be made to sound very good.

As far as I'm concerned, the only real "fault" with it is that it isn't "efficient", but in our case, 
using simple transmitters like the DX-35, 40, 60 and others, followed by a linear amp, this 
makes any loss of efficiency in the modulated stage completely unimportant.

FYI, many years ago, in Montana, I had a Globe King 500 transmitter, which I outfitted with 
a foot-switch. I would routinely check into the "local" SSB net with it. I used the transmitter's 
VFO as my "BFO", turning the receiver's BFO off, to zero-beat the SSB stations, tuning 
them in with the VFO so they sounded natural before I keyed up. I would then turn the 
reciever's BFO back on.  

I used the foot-switch to rapidly switch from TX to RX and back, so it sounded sort of like I 
was using VOX.

It was weeks before someone called me after the net and told me, "Ken, you have an awful 
lot of carrier in there.", I replied, "Boy! I'd BETTER have!" and laughed.

He then came back with, "You mean you're on AM?!?!?!". I just laughed again. No one else 
ever bothered to ask me about that again. ;-)

vy 73

Ken W7EKB



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