[TenTec] OT: Question to the group

[Paul Christensen]

Rick,

Nice discussion on your website.  I'm presently using a symmetrical switch-L tuner at my home QTH.  It's mounted outside the shack in a pressurized NEMA enclosure.  A 1:1 choke is placed on the input.  A pair of vacuum relays switches a motorized vacuum relay either side of a pair of ganged, motorized tape inductors.  In retrospect, I would not have used the C switching arrangement to cover both Hi-Z and Low-Z line terminations.  Doing the math, there's almost never a resulting line input Z of less than 50-ohms when using full size antennas at least a half-wave in length -- no matter the line length.  If the resulting line input Z is less than about 30 ohms, it's an antenna I don’t want in the first place.  The only exception being a mobile antenna.  So, done again, that arrangement would be eliminated saving on cost, complexity, and loss.

The tuner works well but not as efficiently as a link-coupled tuner.  However, out of convenience and due to home RFI considerations, I decided to use this design.  With so many home appliances using switching supplies and noisy microprocessors, it's difficult to use balanced feeders through a house or apartment today.  Line balance is one thing, but these lines cannot completely cancel RFI coupled on receive from various directions.  Transposition blocks may help as used in the olden days.  

A remote-controlled link tuner would by my Holy Grail, but the mechanical complexities start getting in the way of improved efficiency.  To do it right would require separate link coils moved on a rotating turret.    

I would much rather deal with slightly higher tuner loss (under some matching conditions) when  compared to resonant antenna coaxial line loss.  The primary benefit being all-band operation and a very simple antenna feed.   Here, a 600-ohm feeder never breaks its connection: the transmission line wire simply turns at the feed point to form the antenna.  It truly is a zero maintenance antenna -- the only maintenance needed if the wire actually breaks.  With this feed, one never has to worry about moisture ingress, UV destruction, etc.   

Paul, W9AC