[TMC] Sideband Exciters

[John Vendely]

Yeah, that would suggest there was indeed a production SBE-2A--yours 
would be the first I've ever heard of.  There is a nameplate included in 
KIT-248, but it looks like it like a "this equipment modified by 
KIT-XXX" type of thing, not a replacement front panel nameplate.  These 
were stick-on foil labels often seen on TMC equipment with factory or 
field mods...

73,

John K9WT

On 8/28/2021 11:49 AM, triodes wrote:
> John Vendely, my SBE-2A has the factory ID plate affixed to the front 
> of the unit,  and clearly states Model SBE-2A.
>
> 73,
>
> Bruce, W2XR
>
>
>
> Sent from my Verizon, Samsung Galaxy smartphone
>
>
> -------- Original message --------
> From: John Vendely <jvendely at cfl.rr.com>
> Date: 8/28/21 11:41 AM (GMT-05:00)
> To: tmc at mailman.qth.net
> Subject: Re: [TMC] Sideband Exciters
>
> Ya got me curious about the purpose of KIT-248, a substantial
> modification of the exciter which includes, among other things,
> replacement of transformers and installation of a special network
> (NW-127).  Yer right, it definitely affects much more than the RF output
> power; there also appear to be mods to the 17 kc and 287 kc oscillators,
> and the balanced mixers in the upconverters.  A nearly complete
> realignment of the exciter is required.
>
> Two things about the documentation for TMC's modification kits which
> always bothered me are evident here.  They often do not state the
> purpose of the mod or provide a schematic showing the overall changes.
> One would expect a schematic addendum for insertion in the manual after
> updates.  They give good, detailed installation instructions, but it
> often requires considerable scrutiny and reverse-engineering to
> determine the purpose.  My guess is that KIT-248 fixed a number of
> extant problems, including reducing spurious emission levels.
>
> There doesn't seem to be a SBE-2A manual.  So, did TMC ever produced an
> SBE-2A, or did it exist only as the result of this modification to
> existing exciters in the field?  The reason I suspect this is that, by
> 1966, TMC offered the SBE-3 (and SBG) with 3 kc BW sideband filters, a
> superior design which would have obsoleted the SBE-2...
>
> 73,
>
> John K9WT
>
> On 8/28/2021 9:50 AM, John Poulton wrote:
> > If you want the gritty details of converting and SBE-2 to a -2A, see:
> >
> > 
> https://tmchistory.org/tmc_drawings/drawings_db/s/s-docs_900-999/s_952.pdf
> >
> > which details the procedure.  Irritatingly it doesn't say *why* you 
> might
> > want to make these changes!  The parts list runs for 2 pages, and 
> includes
> > mods to wafer switch S106, so I think it's more than just power output..
> >
> > 73, John K4OZY
> >
> >
> > On Sat, Aug 28, 2021 at 3:38 AM Robert Downs via TMC 
> <tmc at mailman.qth.net>
> > wrote:
> >
> >> I have many of the TMC manuals.  There are actually two possible 
> reasons
> >> for the "A" suffix on the SBE-2A.  The first was the addition of an 
> ALDC
> >> (Automatic Load Drive Control) mod for the SBE-2.  But the slightly 
> later
> >> one and more likely the reason for the "-A" was a kit of parts to 
> optimize
> >> operation at about 250 mW PEP output (the SBE-2 was rated at up to 1 W
> >> output).  The kit consisted mostly of resistors of slightly different
> >> values from those in a stock SBE-2.
> >>
> >> Robert Downs
> >>
> >>
> >> -----Partial Original Message-----
> >>
> >>>> ________________________________
> >>>> From: BERMAN <triodes at optonline.net>
> >>>> Sent: Friday, August 27, 2021 2:52 PM
> >>>> To: Meir Ben-Dror WF2U; Nick England
> >>>> Cc: George W1LSB via TMC
> >>>> Subject: Re: [TMC] Sideband Exciters
> >>>>
> >>>> Meir, thanks for the input on the SBE-series of exciters.
> >>>>
> >>>> I have a model SBE-2A (not SBE-2) exciter integrated within my
> >> GPT-750. Do you (or anyone else here) know how the SBE-2A differs 
> from the
> >> SBE-2 or the later SBE-3?
> >>>> I ask this as I was unaware that the SBE-3 and later variants were
> >> less of "a pain in the neck" when compared to those units that were 
> of the
> >> earlier pre-SBE-3 design.
> >>>> 73,
> >>>>
> >>>> Bruce, W2XR
> >>>>
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