From: jl@glen--canyon.com   
      
   On Mon, 5 Jan 2026 08:56:35 +0000, liz@poppyrecords.invalid.invalid   
   (Liz Tuddenham) wrote:   
      
   >I am looking for a device that can be placed across the centre of a   
   >dipole aerial tuned to 150 Mc/s, so as to short-circuit it at about 200   
   >c/s.  The impedance at that point is around 75 ohms, so 5 ohms would be   
   >as good as a short and 500 ohms would be as good as O/C; therefore the   
   >maximum capacitance of the O/C device would have to be around 2pf.  The   
   >power level is negligible - probably microwatts.   
   >   
   >The control signals could be any convenient voltage but they would have   
   >to be isolated from the RF, either by a choke or by some other form of   
   >galvanic isolation.  As the switching frequency is so low, I had even   
   >wondered about a cheap photovoltaic panel illuminated by a few LEDs.   
   >   
   >Does anyone know of a suitable device, especially one with built-in   
   >isolation such as a high-side driver for power control?   
      
   Are you making a switchable reflector?   
      
   People make isolated mosfet gate drivers with built-in dc/dc   
   conversion, but they will have oscillators inside so may be emi   
   hazards.   
      
   You could use my dual optoisolator totem-pole thing with a battery,   
   driving a fet or phemt.   
      
      
   John Larkin   
   Highland Tech Glen Canyon Design Center   
   Lunatic Fringe Electronics   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)