On Sun, 10 Aug 2008, raypsi wrote:

I guess what I really wanted to do is make a PA
for all bands with a plug in PCB. That would have
the right size coils etched into it for each band.
So when I change bands I would just unplug one
band PCB and plug in another PCB for the band
I want. Rather than a band switch that would arc
out. Or a roller inductor that I would have to turn
to the right number of turns to get to the band I
want. Alot cheaper to plug in PCB's than the
price of a band switch with lots of wires
or roller inductor.
This would eliminate trouble switching to 10
meters with a band switch I suspect.

I'd use an edge card connector to plug the coils/PCB
into and out of an edge connector.

Well you wouldn't be changing bands with the transmitter
going. So in that regard, plug-in coils, bandswitch or
jumpers are about the same.

People like switches so they don't have to turn off their
transmitter (to ensure not dangerous voltages) reach into their
transmitter and plug in coils. If you have to reach in,
at least some of the other possibilities are viable.

Your edge connector may introduce problems of bad contacts.
If you have to run current through them, bad contacts will
not be a good thing.

And I'd add that a large inductor may not be feasible etched
on a circuit board. The only times I've seen coils etched
into circuit board have been when the coils are low inductance,
the sort of values you'd see at VHF and UHF. Making a coil
large enough may result in way too big a plugin board.

You haven't really specified, I don't think, whether this
is a tube or transistor transmitter. In the days of tubes,
the transmitters were narrow band. With transistors, they've
generally been broad band. So with transistor transmitters,
the bandwitching has been about switching in bandpass or low
pass filters for each band, and since the broadband transmitter
has 50ohm output impedance, the switching is relatively easy.

Michael VE2BVW