modulation of low power rigs like DX-60

[Barry Anderson]

At 07:38 AM 11/15/97 -0800, you wrote:
>The popular low-power phone/cw rigs of DX-60 / Knight T-60 (etc.) vinage
>were AFAIK not plate-modulated.  I was wondering -- what was/is the
>advantage to the modulation methods used in rigs of that genre, opposed to
>plate modulation??

There was only ONE (1) reason ... it was cheap to implement. Frankly, it had
a very mushy quality to it and was eaten alive during high noise/QRM
conditions. The AGC on the receiver pumped up and down, with the receiver
gain either too high or too low. Nasty stuff!!
>
>Was there some preferred aspect to the screen modulation (or whatever it
>was)...?  Is it not as "good" as plate modulation, and if so, why not?  Was
>the modulator-circuit more or less just thrown into a basically cw-novice
>transmitter, to allow for merely adequate voice capability (for novices
>eventually upgrading to general class)?

 The above is true. It made a CW rig work on AM. Some of the better, cheaper
rigs used a method of modulation called Heising or Choke modulation. This
was close to plate modulation in quality. The only trouble with this type
modulation was  you could never reach 100% ... but it sounded GREAT
otherwise. The Globe Scout series used this type of modulation.
>
>Thanks for any comments...
>
>JWG
>
        73 Joel & DX

Barry
Barry Anderson K3SUI
Frederick, MD
banderso at eni.net

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