Eric Greenwell wrote:
Udo Rumpf wrote:

It's possible you have a problem not related to the voltage; e.g.,
maybe the voltage is dropping well below the 11.8 volts when the
transmitter is keyed, or the radio is not functioning within
specifications.
Eric Greenwell


I have a 720A Dittle radio
Power requirements;
Receive .1 - .4 amps
Transmit (tone) 1.4 amps (.8 amps unmodulated)
The 11.8 volts I was referring to is before transmit.
If I remember correctly when the battery is fully charged
and I hit the transmit button the voltage drops from 12.7 to 12.2.
Udo

With the battery run down to 11.8 volts, measure the voltage right at
the radio connector while keying the transmitter for 5-10 seconds. If it
drops more than it does when the battery is fully (or nearly so)
charged, the problem might be the battery.

However....
I found a German manual for the ATR720A (and ATR70C in English) on the
Filser site (I think they took over the radios from Avionic Dittel). The
specifications don't make any mention of what voltage range the radio
will function over, so I suspect 12 volt battery operation wasn't on
their minds when it was designed. This appears to be an older design
radio, and likely is one that would benefit from 14 volt operation.

Absolutely true. But if you look hard enough, you'll see Filser claims
10.5 to 16 volts as an input voltage range for this radio. The same or
better as the current generation of super radios, which according to the
experts on RAS, supposedly were redesigned to work on lower voltage.



So, if it's not the battery, your choices seem to be a modern radio
(like the Walter Dittel FSG 2T I mentioned) or going to a 14 volt
battery pack. Or waiting till you get closer to the airfield to make
your call :^)


Or, he could get three or four large 12 volt batteries, and keep switching
between them, like a lot of people do. Certainly works for a while.
Particularly if you swap out batteries every year or two so you're using
only really fresh ones.

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. 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.


-Dave