[TowerTalk] Dummy Load power resistors...questions!

[n0tt1 at juno.com]

OK, thanks Jim,

Interesting why Bendix would call this thing (in part) a
"modulator"...nothing
in there to modulate a RF signal that I know about....just a high power
50-ohm dummy load.

73,
Charlie, N0TT

On Sun, 28 Jun 2020 20:04:01 -0700 jimlux <jimlux at earthlink.net> writes:
> On 6/28/20 7:32 PM, n0tt1 at juno.com wrote:
> > Thanks to Jim and Chuck!
> > Definately non-inductive for this application, but the power 
> rating
> > is, I don't know.  I know it was used at a 5KW AM radio station 
> for
> > some testing.  I should have mentioned that the glass tubes look
> > like common florescent tubes....white in color with no hint of 
> carbon,
> > etc.  I would do some more examination but I sure don't want to 
> risk
> > breaking one of them.  They are now back in their case, sealed by 
> a
> > "jillion" screws!!!
> > I looked at 
> > 
>
https://theelectrostore.com/content/datasheets/kanthal_globar_resistors.p
df
> > Doesn't appear to be anything similar in appearance, but like Jim 
> said 
> > there's
> > lots of area for cooling.  It could be that there's something 
> inside the
> > tubes which can't been seen.
> > Unfortunately I threw away some electronic industrial catalogs 
> from the 
> > late 1960's
> > era.  Oh! BTW, this dummy load was made by Bendix and it's called 
> a
> > "Dummy Load Modulator".  Not sure what the "modulator" reference 
> means.
> > I do have photos if anyone wants a look.
> 
> 
> probably either an AM transmitter or radar transmitter.
> 
> The modulator in a radar transmitter is the thing that generates HV 
> pulses of the correct length and voltage.
> 
> The modulator in a AM transmitter is an audio amplifier that puts 
> out as 
> much audio power as used in the RF.
> 
> 
> 
> 
> > 73,
> > Charlie, N0TT
> > On Sun, 28 Jun 2020 12:01:58 -0700 jimlux <jimlux at earthlink.net 
> > <mailto:jimlux at earthlink.net>> writes:
> >  > On 6/28/20 11:43 AM, n0tt1 at juno.com <mailto:n0tt1 at juno.com> 
> wrote:
> >  > > Hello everyone,
> >  > >
> >  > > I recently aquired a "commercial" dummy load that I'm sure 
> will
> >  > handle
> >  > > more than 2kw.
> >  > > There are 12, 600-Ohm resistors in parallel that measure 
> 50-Ohms
> >  > with a
> >  > > Ohmmeter.
> >  > > The resistors look like frosted glass tubes with metal end 
> caps.
> >  > They
> >  > > measure 9.5" in length
> >  > > and 1" diameter.  The number stamped on the ends is E9935R 
> and
> >  > their
> >  > > vintage is late 60's.  A Google search for that exact number
> >  > turned up
> >  > > nothing.
> >  > >
> >  > > Question:  Does anyone know the power rating of these 
> resistors
> >  > and
> >  > > what type of resistor are they?
> >  >
> >  > They might be non-inductive power resistors from Carborundum 
> corp
> >  > (now
> >  > part of Sandvik, as I recall). I've got a bunch of them, 
> although
> >  > mine
> >  > are grey or brown.
> >  >
> >  > They could also be a thin film resistor deposited on a ceramic
> >  > substrate. Same idea - lots of area for cooling.
> >  >
> >  >
> >  >
> >  >
> >  > >
> >  > > I have photos.
> >  > >
> >  > > 73,
> >  > > Charlie, N0TT
> >  > >
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