Date: Sun, 02 Jan 2000 11:26:09 -0800
From: Bob Chesley <rchesley@soca.com>
Subject: Re: Transmitters and Antennas
To: Greg Nelson <gregsays@swbell.net>
Cc: All Lancair enthusiasts <lancair.list@olsusa.com>
Reply-to: rchesley@soca.com
Message-id: <386FA651.4C0AB1B7@soca.com>
References: <386F433F.9C35A8EE@swbell.net>
Mime-Version: 1.0

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Greg,
    I agree with your comments on the advantage of handhelds and AOA.
    I'd be interested in how you have yours hooked up. FYI, I have mine
connected to a separate dipole, a foil strip, to increase the bandwidth
slightly, that is inclined at 45 degrees on the rear baggage bulkhead.  The 45
degrees gives me 0.7 of the correct polarization for both the com and nav
functions and operates well.  My figures are at the hanger, but the VSWR is
pretty good across the band, 1.5 - 2.5 as I recall.
    Although I have the handheld audio wired into an auxiliary input in the
back of my Terra COM, I can't use it because on handheld transmit the RF
saturates the Terra and the receiver audio is off for about 20 seconds until
some rc circuit drains down.  The Terra COM intermittently does the same thing,
which means that it is not reliable either.  I can use the handheld as an
independent unit, but cockpit noise has has made that difficult.
    My troubleshooting the Terra has been a painful process.  Thrimble, which
bought Terra, has tested the unit and says it is fine.  They don't have a clue
about the RF saturation I'm talking about, but I have seem it on numerous
occasions in ham radio rigs that were not well shielded.  It will work on the
test bench for me, and after I put it back in the tray and test it on the
ground.  But when I fly, the unit fails.  I've checked grounds, replaced in-line
BNC connectors and measured SWRs during xmit.  Figuring that RF was getting into
the Terra unit somehow, the last time I flew I clipped the three aux inputs
(VOR, glide slope and handheld) and the four external wires that go to pots on
the panel that control volume and squelch for Terra's internal intercom.  For
the first time in several months I did not have a communication failure, which
could confirm my diagnosis (or could be the intermittent factor).  I'm currently
recuperating from back surgery and haven't been able to take the next step and
start restoring inputs... or putting in a separate intercom or, heaven forbid,
an audio panel.  By the way, for others with Terra, the audio quality improved
considerably when working without the aux inputs.
    My displeasure with the Terra unit(s) has another facet.  I wonder if anyone
else has had this beef with Trimble.  I bought my Terra units (COM, VOR,
xponder, encoder) at Oshkosh in 1994, when they were making a pitch for the
homebuilders market by offering a three year warranty that was to start with the
date of the airworthiness certificate.  Trimble claims they have NEVER heard of
such a warranty or had anyone come to them with such a claim.  I have confirmed
their warranty policy with the former Terra President and have a letter from
his, then, Vice President of Marketing stating that they were indeed offering
such a warranty.  I'm still working on Trimble, but wonder if anyone else has
had a similar experience.

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