[TowerTalk] 80m loop idea

[Brian Smithson]

Hi all!

A while back I posted a question asking for suggestions for covering the 80m
band between two towers broadside to EU about 160-170' apart. I neglected to
include the tower height (70' each) but I got lots of good recommendations.

I recently purchased EZNEC3 and it is pretty slick. I've come up with what
seems like a very workable plan for a vertical 80m loop tuned for 3.8 with
switchable stubs that come off the two bottom corners sloping back to the
towers that bring it down to 3.53 when they're connected. I get about 
100KHz 2:1 bandwidth at both frequencies.

I'm trying to work out the details of actually switching these stubs in/out
and the control line and I wonder if this makes any sense. What I thought
I could do is use the control line for the relay itself as the stub on each
corner. When power is applied to the relay, it switches the stub _out_ and
the loop is tuned for 3.8. When no power is applied the relay switches the
stub _in_ and the loop is tuned for CW. One of the control lines is also
the stub that is connected to the loop when the relay is not energized.

	Loop corner ----o\
			      \o--+-- to 1/2 of control lines ---- CHOKE ---
				    |
				Xo--+
	     Relay coil-> Xo----- other control line --------- CHOKE ---

To work, the stubs need to be a certain length, but the control line wants 
to go all the way to the shack. Can I put some kind of inductor on the 
control line that passes DC but blocks 80m making it think the line ends
at the right length? The control line then serves triple duty - controls
relay, acts like stub when switched in, and supports lower corner.

Does this arrangement even make sense, or should I just put in control lines
seperately?

TIA,

-Brian n8wrl

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