Post B7M9xAdLtIC3izq3V2 by vxo@digipres.club
 (DIR) More posts by vxo@digipres.club
 (DIR) Post #B7M9x39JiZ0cVojTDE by vxo@digipres.club
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       thinking again about the Altronic Soda Dummy Loadjust a big unhinged bizarre buddyhttps://altronic.com/products-dummy-loads-leak-detectors-power-measurement-resistors/dummy-loads/soda-rf-dummy-loads-40000-seriesbut how weird is it? oh you're in for a treat.
       
 (DIR) Post #B7M9x3PGlFllJICD4q by arrjay@tacobelllabs.net
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       @vxo is this like a “shit we had to dump transmitter power somewhere” kind of…thing?
       
 (DIR) Post #B7M9x4aeMQT0ysWoSG by vxo@digipres.club
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       so what this insane thing is doing is that it has a large soda solution tank (the huge hopper piece you see in the product photo) and it circulates this solution into a resistor chamber where, somehow, the RF input is coupled into the soda solution and actually uses it as a resistor.a conditionally acceptable resistor.the solution temperature must be maintained at 75 degrees C for it to come up at the desired resistance.a plate heat exchanger is also in the loop to cool it back down
       
 (DIR) Post #B7M9x64opkC3ajeQ7M by vxo@digipres.club
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       it has large outdoor heat exchangers and a glycol loop on the outer liquid loop of the system.that soda solution resistor is hilarious though. what is the input mechanism? I'm guessing galvanically coupled with some kind of electrode plate. the diagrams make it look like it's got a cone shaped outer chamber
       
 (DIR) Post #B7M9x7hqm70ce4v6au by vxo@digipres.club
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       next time I'm at the tower I should get a picture of the old 1970s looking water load we use as a doorstop. it's a big gray painted misshapen traffic cone looking thing.the conical form factor is a clever complex impedance matching measure; a lot of Bird's oil filled dummy loads in the 500-10000 watt range have a conical metal thing surrounding the resistor with big oil flow openings in it for this purpose. it looks like the world's messiest ice cream cone.
       
 (DIR) Post #B7M9x9CjCnIpI8NHMW by vxo@digipres.club
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       what, you don't eat your ice cream with your hands up there?we do down here!! this is dark RF magic zone! we do what we damn well please down here. impedance? it's whatever the hell we want to, we made it complex! voltage? yes. current? yes. extreme pickiness over materials? we don't like our food to touch. no wait, we do. fnord.
       
 (DIR) Post #B7M9xAdLtIC3izq3V2 by vxo@digipres.club
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       there is a very clear and always active pipeline between any question of high power RF engineering and fnorda lot of DC power -> MAGICAL DEVICES -> fnord
       
 (DIR) Post #B7M9ypiubcqFS4ERxw by vxo@digipres.club
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       @arrjay exactly! these big mammas are usually used to allow transmitters to be brought up for testing and maintenance without going into the antenna, in the case of high powered (500KW not being uncommon!) shortwave broadcast facilities
       
 (DIR) Post #B7M9ypvJrUla4Y2MIy by vxo@digipres.club
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       @arrjay in my corner of the world, high powered UHF television, continuous impedance and low stray inductance/capacitance are important in the load, so we tend to have these liquid cooled loads. they are freakishly small for being, say, 80KW units. they require 10+ GPM of glycol or water flow or bust.oh i mean it when i say bust, they'd just SNAP AND DIE without coolant
       
 (DIR) Post #B7M9yrwSMEreKeaIM4 by vxo@digipres.club
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       @arrjay I've read about some transmitter facilities having these water cooled loads, with "open loop" cooling-- aka, tap or well water from the site water supply is piped through the load to a drain, and how no one thinks anything of that until that one time water pressure is lost and a water pressure interlock switch way upstream in the control ladder kicks everything off air and won't let it come back to play
       
 (DIR) Post #B7MA0n1BdQM7dmiFkW by astraleureka@social.treehouse.systems
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       @vxo @arrjay can you elaborate on "snap and die"? I imagine all that energy with no cooling is gonna melt or otherwise destroy something in the load, but what happens after that? my mind goes to the movie-trope of "there's an overload building up and it's gonna explode" but ... maybe?
       
 (DIR) Post #B7MA0nNsH4VIm9KN72 by vxo@digipres.club
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       @astraleureka @arrjay it'd be the resistor cracking or otherwise degrading from extreme heat, followed by a hilariously expensive eruption of plasma as it arcs over