[TowerTalk] Toroid Core Material Selection

[Tom Rauch]

> BTW, my homebrew project is a pair of relays to switch two
antenna
> connections in the shack.  The design bandwidth for these
two antenna
> switches is 1.8 to 450 MHz.  A friend with a spectrum
analyzer measured some
> crosstalk between the SO239 connecters and suggested the
toroids be inserted
> in the dc lines to each relay to improve isolation.
Insertion loss was also
> measured to be about 3 dB at 500MHz.  This is not
acceptable so I am looking
> for better relays.

Keith,

If you are only switching two ports to a common 500 MHz
should be easy.

In all the switches I've designed, I've NEVER had to bypass
or filter coil leads. That tells me you have a layout or
relay selection problem.

Capacitance across contacts limits port to port in a good
design, and with a wise selection of conventional relays the
system should have less than 1/2 dB loss at the upper end
and a worse case crosstalk about -50dB at the high end.

73 Tom