> Marv says:
>
> > A rotating contact arrangement driven by small motors?
>
>
>
> I'd go for a solenoid driven system as being potentially cheaper, as
> probably easier. If the moving contacts were the input and output of the
> section, the bypass could be matched.
>
> ____
> | |
> B C
> In-------- ---------out
> A-----B
>
> The in/out could be parallel, as in the open frame style relay,
> andarranged to make a slab line that was matched when closed. Although I
> doubt the mismatch will be noticeable even at 30MHz. As the application
> sees a fair amount of RF power, is silver plating really necessary?
I use conventional relays in my "line stretchers". They are perfectly
fine up to 30 MHz, if you select relays with short internal leads.
You can use an open-frame relay and cut the armature wires off the
normal tabs. Just mount the relays on a PC board or copper sheet
and bring the leads out back, with the relays all next to each other.
The flying lead from one armature connects to the adjacent relay.
You might have to capacitor-compensate the relays at the 30 MHz
end of things to keep the "bump" down, depending on the relay, or
use a "sandwich" of another board on top as a groundplane to
establish an impedance of 50 ohms in the system.
I'm building a system now for receiving antennas, and will use
"BCD" line sections to get every couple degrees from 0 to 358
degrees. 0-178 is taken care of with delay lines, while the
remainder is accomplished with a 180 degree inversion of the
output.
73, Tom W8JI
w8ji@contesting.com
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