OT: Elecraft Relays for BC-Band Energy-Reject Filter

[Darrell Bellerive]

I am building a BC-Band Energy-Reject Filter as described in the 1990 ARRL
Handbook and February 1978 QST for an old SW receiver. This filter, designed
by Ed Wetherhold, N3NQN, offers about 60 db of rejection of BC band signals
yet will still pass 160 meter signals with an insertion loss of only 0.8 dB.

I would like to use the same latching relays that Elecraft uses in the K2 to
switch the filter in and out.

I wonder what the isolation is for these relays at MF/HF frequencies. The
relays used by Elecraft (Omron G6HU-2) are DPDT and a single relay could
switch both input and output, but I am concerned that the isolation between
the input and output would be comprised by the proximity of the input and
output connections and contacts.

I could also use one relay at the input side of the filter and another relay
at the output side of the filter which should have better isolation.

Please email me your comments. Thanks!

--
Darrell Bellerive
Amateur Radio Stations VA7TO and VE7CLA
Grand Forks, British Columbia, Canada
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[N2EY]

In a message dated 11/16/06 1:54:47 PM Eastern Standard Time, [hidden email]
writes:


> The
> relays used by Elecraft (Omron G6HU-2) are DPDT and a single relay could
> switch both input and output, but I am concerned that the isolation between
> the input and output would be comprised by the proximity of the input and
> output connections and contacts.

My guess is that the the isolation would be compromised, particularly where
you need it most.

> I could also use one relay at the input side of the filter and another
> relay
> at the output side of the filter which should have better isolation.
>

Two relays is definitely the way to go. Since the relays are DPDT, use one
pole to switch each end from the filter input to a piece of coax bypassing the
filter, and use the other pole to ground the center conductor of the bypass
coax when the filter is selected. That way the coax has a harder time acting as a
path around the filter.

73 de Jim, N2EY
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