A few thoughts on heat tests and heaters

[Bill Layer]

Hey David,

>With high-power radar, it is better to use physical waveguides than 
>coaxial cable.  Waveguides are sealed metal channels whose physical 
>dimentions are the same as one wavelength of the RF being carried - 
>makes for a very low loss situation.

Ok, I'm familiar with the waveguide principle.

>Only problem is that condensation kills the efficiency.  The 
>waveguides are filled with pressurised Nitrogen ( a PSI or two above 
>ambient ) and baked - silica gel removes the moisture and a pony 
>bottle of N2 gas keeps any pinhole leaks from causing problems - 
>positive pressure...

How interesting.

>Obligatory audio information:
>
>During WW2, the frequencies of RADAR were much lower and the
>wavelength for the waves were about the same as the wavelengths
>of sound waves in air.  There was a line of loudspeakers ( Karlsen? )
>developed after WW2 that essentially took broadband RF antenna
>designs and tweaked the impedences a bit to match a physical speaker
>instead of an RF waveguide.

Hmmm. Could this be the highly-touted 'Carlson' enclosure? The Carlson
features a strange front aperture, with a rougly logarithmic-curve shape.
It is driven by a 15" Jensen or Altec co-axial driver, the number I cannot
remember.

Pretty cool item, but honky as heck. Not nice listening, and I'm comparing
it to my JBL 4311 monitors (which have a serious 'reputation for
coloration' of their own).

>Very very high effeciency.  Frequency response was not linear but 
>nothing else was at that time either so it didn't matter.
 
Amen. Beat the band with 2 watts. So is anyone interested in building a
really simple, but nice sounding micropower OTL? 1 watt of screaming direct
coupled energy.


Bill Layer
Sales Technician
<b.layer at vikingelectronics.com>

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