David Kinsell wrote:

The FSG 2T very specifically says don't try to transmit with less
than 11 volts, so I think that would be an expensive option that
really wouldn't help out.

Contrary to what Dave writes, here is what the FSG 2T operation manual
says on page 50 of the FSG 2T Installation and Operation manual,
available on Wings&Wheels or Dittel's web site:

6.13 Emegency Operation

Without degradation the FSG 2T can be operated on a dc source between
11 Vdc and nearly 9 volts. This however will NOT reduce the TX
output level, RX sensitivity, and audio output power, due to internal
supply regulation. Below 11 volts the dc indicator flashes
continuously as low supply warning. Since the current drawn from the
battery will increase with lowered Dc supply voltage, the automatic
shut-down will speed-up.

If the supply voltage drops below 9 Vdc the FSG 2T swithces OFF
itself. This automatic feature avoids battery damage due to deep
discharging, even if the radio is left switched ON for months! This
is true for all types of 12 Vdc batteries.

If the battery recovers and voltage exceeds approximately 10.5 Vdc,
the radio returns to operation with the last used setting.

The above clearly shows why pilots have good experiences with Dittel
radios operating on 12 volt battery systems.

I suppose he could get a new Becker, but it's supposed to have have
at least 12.4 volts. Wonder where all these new super-radios are
that people keep talking about???? When you look at the facts, they
just turn out to be figments of some rather active imaginations.

I think I have found the explanation for the super-radios that we have
today. I stumbled across this reference recently:

Here’s the operating voltage matrix right out of DO-160 . . .

Voltage Category B

Maximum 15.1
Nominal 13.8
Minimum 11.0
Emergency 9.0


Modern avionics should operate over the voltage ranges cited for each
category of performance commensurate with the applicable system
voltage.

The table shows operation from 11.0 volts to 15.1, with emergency
operation down to 9 volts, essentially what the Becker and Dittel radios
(and probably others) specify. My short Google search for the standard
came up with an index

http://www.tuvamerica.com/industry/a...ce/emctest.cfm

and this

http://www.aeroelectric.com/articles/do160.html

that shows this specification is just one of many in the standard. I
don't know when the standard came into being, but I'm guessing it (or
the rationale behind it) is what drives manufacturers to produce radios
with a wide voltage tolerance. It's been around for a long time, as the
Dittel FSG 60 manual (March 1981) references the standard.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA