Michael Hatzakis, Jr MD wrote:
> I’ve got a couple of TNC’s and radio’s in my car that I like to
> operate with backup battery after the car’s ignition goes off. I use
> a charging circuit to keep the battery charged when the car is
> running.
>
> This is my problem: when I start the engine, the ignition noise
> causes havoc with the TNC and other digital devices.
Is it "ignition noise" or power glitches?
What brand and model of TNC's are you using?
Because some Kantronics TNC's may use an internal 9V battery as backup,
and prevent the TNC to go nuts with the power glitches. Check the
schematics
of the KPC-3 and KPC-9612.
> I have tried
> chokes, filter caps etc. But the spikes are too broad. I tried a
> timed delay circuit for delayed switchover, but this causes too much
> complexity. I tried using a diode so devices can run on the filtered
> battery voltage while charging from the mains, but the voltage drop
> prevents proper charging.
Did you use POWER Schottky diodes? They have lower voltage drop.
It might be interesting to consider the power on switch of the FT-757,
which uses a
relay actuated by a circuit protected by a diode in series. The relay
won't close with low
voltage or reversed polarity.
> Any other ideas on how I can make this work?
You have batteries, and you should not allow the starter to draw power
from them.
Otherwise, with no batteries, one large ESD (say, 1 farad @ 16 V) might
help. It is what
some people with large audio power amplifiers to have some "local" power
reservoir close
to their monster amplifiers.
But if your problem are power glitches, and might very well be the case,
you should isolate
your radios and TNC's from the main battery during startup.
How is the health of your main battery? Maybe a portable digital scope
hooked on top of it
might reveal what happens during startup...it is just a different kind
of EKG...
Jose, CO2JA
DX Cluster telnet://cluster.dynalias.org
Suggested Calling/Beaconing Frequencies:
All frequencies are USB and assume a centre audio frequency of 1000Hz
(e.g radio dial at 14.077.4 and 1000Hz on your waterfall = 14078.4)
20M: Primary : 14.078.4 Secondary: 14.076.4
30M Primary: 10.142 Secondary 10.144
80M Primary : 3583 Secondary: 3584.5
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