[Milsurplus] AN/SRT-4A Marine Transmitter

[Kenneth G. Gordon]

On 16 Aug 2018 at 9:53, Richard wrote:

> After a bit of thought I've resolved to restore it to original 
> condition.  The 807 oscillator only passes 18 to 20 ma, so if regulation 
> is needed it can be easily done with VR tubes or a handful of Zeners.  
> Looking back, many "surplus conversions," and changes, were ill-advised 
> to downright destructive.

You will get zero argument from me on that issue!!!

IMHO, MOST ham-mods were never well thought-out and actually make the involved 
equipment work WORSE afterwards.

Any "upgrade" to older gear (should one feel so inclined) must be cogitated on for months 
and every possible event and effect, foreseen and unforeseen, taken carefully into account. 
Terman's is a valuable resource for this.

The OT weren't stupid.

I will venture this, though: beam-tubes do NOT make good oscillators. There is much too 
much inherent coupling between the cathode and/or grid, and the plate, essentially 
bypassing the screen grid, if there is one. I could never understand why those were so often 
used. If one "needed" a tube the size of the 807 for an oscillator, the much better (as an 
oscillator) 837 should have been used....like the Navy used in so many transmitters.

Although the plate dissipation rating of the 837 is about 1/2 that of the 807, in oscillator use, 
that doesn't matter.

The 802 (almost impossible to find any more) is also an excellent oscillator tube. And the 
6AG7 is most certainly a far better oscillator tube than a 6V6 or even the 6L6.

The Navy even used an 860 as the VFO in at least one transmitter. The 803 would make an 
excellent oscillator/VFO tube, in fact, although it is kinda big. :-)

No beam-tube should ever have been attempted to be used as an ECO. Period.

Ken W7EKB

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