The schematic for one antenna of the microHAM Double Six and
Double Ten switches is shown right on the web page with both
RF and control. Here is the principle of operation:
In addition to the small control relays for lock-out, the
microHAM switches use two relay contacts between the antenna
and radio. Switches that "cheap out" and use only one set
of contacts generally fail to provide sufficient isolation
between the transceiver and an antenna that is active on
the "other" transceiver - particularly at the 1500 W level.
In addition, the extra relay provides an extra degree of
safety because a single relay failure can not allow the
transceivers to be connected together.
... Joe, W4TV
> -----Original Message-----
> From: firstname.lastname@example.org
> [mailto:email@example.com] On Behalf Of Barry Fox
> Sent: Monday, March 01, 2010 2:40 PM
> To: firstname.lastname@example.org
> Subject: [TowerTalk] Budget 4-Pack?
> I have two HF radios and 4 different HF antennas. I would
> like to use each rig on any antenna, while obviously locking
> out that antenna for the other rig. The commercial products
> 6-Pack, 8-Pack, etc are way over my budget. Anyone have a
> schematic for a "4-Pack" or similar device they would like to
> share? Obviously relays are the way to go, and I can get the
> RF relay switching part of it on paper but
> not the lockout logic. Some sort of electro-mechanical exclusive-OR
> gate array / diode matrix? Anyone been there and done that?
> TNX / 73, Barry - W1HFN
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