[ARC5] SCR-274N Makes It on ARRL.ORG

[David Stinson]

-----Original Message-----
>From: MillerKE6F at aol.com
>>Subject: Re: [Milsurplus] Re: [ARC5] SCR-274N Makes It on ARRL.ORG
>
>.  In the context of the hay day of command set usage and the state of  the 
>art of TVs during that period and the state of amateur radio prowess in  
>dealing with TVI, the command sets in general even when run somewhere near their  
>rated power were a grand source of TVI....

We seem to be saying nearly the same things concerning this point.
During the "hay day of command set usage,"  most hams did not tune 
them correctly.  As shown by my measurements in 1996-
even at less than rated output, if the rigs were mistuned they had
unacceptable harmonic levels, especially at the third harmonic, 
which would have played the very devil with old-tech televison IFs and tuners.

I have tested many Command Set transmitters in original configuration,
with good original bypasses and good tubes with no grid emission.
I have never seen a single VHF spurious or parasitic,
given my test equipment's noise floor of around -80 to -100 dBm.
However- if you look at the transmitter design,
its evident that running 800-900 volts worth of poorly regulated B++,
which was very common during the time in question, VHF nasties would
be very possible.  Perhaps this is the source of the tales of VHF spurs.

73 Dave S.