[Amps] Band switching

[Peter Chadwick]

Jos asked:
>To avoid using old ledex to swich the tank coil, why one doesn't use
relays or PIN diode ?<

The current is a bit high for PINs - it can easily hit 20amps. The voltage rating needs to be at least twice the HV, so we're talking something like 6kV and 20amps for PIN's or relays.....although it's carrying current, rather than switching current in the relay case. It's instructive to calculate the circulating current in the tank circuit for any given working Q, although the answer can be a bit frightening - certainly tells you why you shouldn't hook up the tank with a bit of 16 gauge tinned copper! This is why you need to cool the tank coil if you're going RTTY or SSTV, and it's a good idea anyway.  So even the old BC375 switches are a bit pushed, although they seem to stand up pretty well.
73
Peter G3RZP