The following is a response I received from Trimble, regarding
intermittent problems with the Terra 760D tranceiver installed in
my Europa.
It may be of some relevance to all of you with Terra kit in composite
aeroplanes. It does support a previously aired theory, and there is
indeed a section in the installation manual, as the respondant states.
My regret is that I wish I had known this before purchasing the equipment.
Perhaps it offers some hope though, if someone can figure a way to fit a
42inch ground plane inside the fuselage.
Perhaps, I should have bought an AWACS !
Alan
cc:
Subject: RE: Unreliable Terra TX760 transceiver.
Mr. Stewart
Unfortunately without an adequate ground plane the 760 will not work, hence
your "aircraft orientation" symptoms, this is due to loss of omni due to
lack of a ground plane.
As stated in the 760 install manual paragraph 2.3.3, "a minimum of a 42'
diameter circle with the antenna at center" is required.
Also the base of the antenna must be bonded to the ground plane.
There may also be leakage at the coaxial connections, the coax connection at
the rear of the 760 mounting tray and at the antenna should have a minimum
of dielectric exposed, too much exposed dielectric and the RF energy will
short to the coax shield and thus you have no transmission range and your
audio will sound weak and garbled to the tower or receiving station.
Regards,
Tech. Support
EMAIL: aerospace_techsupport@trimble.com
> .
>
>
> -----Original Message-----
> From: Alan Stewart [SMTP:Alan.Stewart@marconi.com]
> <mailto:[SMTP:Alan.Stewart@marconi.com]>
> Subject: Unreliable Terra TX760 transceiver.
>
>
> Dear Sir/Madam,
>
> I own and operate a Terra TX760 tranceiver in my Europa composite kitplane
> here in the United Kingdom.
> The Terra Radio is unreliable on transmit. Sometimes I can transmit up to
> 30 miles or more, on other occasions, selected destinations have
> difficultly picking up my transmissions from less that 100 yards ! Often
> this improves dramatically when the aircraft orientation changes. The
> destinations are frequently high quality airway radio equipment. (e.g.
> London Information)
> The equipment is useable, but unreliable. I know of many others with
> similar problems with their Terra equipment.
> Do you offer a solution to this problem ? I am aware that because my
> aircraft is plastic, it is difficult to offer a wide 'ground plane' for
> the antenna.
> However, my wide band Icom A20 handheld transceiver does not suffer any
> problems
> !
>
> Thanks in advance for any service solutions you may offer.
> Regards,
> Alan Stewart
>
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