[Top] [All Lists]

[TowerTalk] New designs for 4 squares

To: towertalk <>
Subject: [TowerTalk] New designs for 4 squares
From: "Lux, Jim" <>
Date: Mon, 27 Jun 2022 11:13:38 -0700
List-post: <>
With new, inexpensive VNAs, I think it would be interesting to start looking at redesigns of the typical 4 square control box.

At a simple level, keep the same phase shift network (Collins hybrid), but add relays to allow measuring S11 of each element and Sx1 mutual coupling.  Sure, a problem that causes mismatch to dump power into the dummy load will catch some faults and if you have remote power metering on the load (a temp sensor might work). But a full 4 port measurement may be more useful.

I can see two ways to do this.. one is to keep the VNA in the shack, and run a second coax line back for the other port.  The other is to remote the VNA (which typically has a serial over USB interface).

There are some tricky aspects - you probably can't use a SPDT on each element to switch the element to the hybrid or the VNA, because the isolation across a single relay isn't good enough (cheap VNAs have a max of maybe 0dBm - I'd want to see 70-80 dB isolation to avoid destroying the VNA). And I've just now started to think about how to arrange the relays (it would be nice to be able to detect failures in the dump load and the hybrid as well.

You might be able to just provide the ability to short/open each element and make all your measurements through the hybrid. There's already a bunch of relays to switch the directions.


TowerTalk mailing list
<Prev in Thread] Current Thread [Next in Thread>
  • [TowerTalk] New designs for 4 squares, Lux, Jim <=