A few thoughts on heat tests and heaters

[Bissell, Harry]

The "Carlson" (Karlsen?) enclosure actually works well over the frequency
range intended, but like the exponential horn, it has to be REALLY BIG.
Really big was required when a high power amp was 15 watts or so. (Really
big is still better... Size does matter :-) Harry

> -----Original Message-----
> From:	dave.halliday at greymatter.com [SMTP:dave.halliday at greymatter.com]
> Sent:	Thursday, January 28, 1999 1:02 AM
> To:	synth-diy at mailhost.bpa.nl
> Subject:	Re: A few thoughts on heat tests and heaters
> 
> >>I saw a schematic on a radar transmitter for a air traffic control
> >>tower.. it had a seperate schematic for nitrogen lines.. nitrogen is the
> >>only way to cool without condensation supposedly..
> >      
> >     So was that an immersion system then? A pure liquid nitrogen bath
> would
> >     certainly be anhydrous... Or was the nitrogen used in another
> manner?
> 
> 
> 
> 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.
> 
> 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...
> 
> 
> 
> 
> 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.
> 
> Very very high effeciency.  Frequency response was not linear but 
> nothing else was at that time either so it didn't matter.
> 
> 
> 
> 
> 
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