[OZAPRS] TNCs & Power disruptions (was Problems with APRS in SEQld)

[Richard Hoskin]

Gday,

We've done a lot of experimentation with the MFJ TNC, UIDIGI and power
fluctuations.

The bottom line is;

The MFJ dose not tolerate brown-outs or relatively slow supply voltage
dips
or rises. If the power is cut off sharply then it will not corrupt the
TNCs
ram.

The MFJ -Needs- protection against power fluctuations whether you have the
backup battery jumper in or not. We have found that with no backup battery
jumper the TNC can still lock up, however is happens much less than with
the
jumper.

To solve this problem we have installed 24Ah SLA batteries at most of or
digipeater sites to supply power to the TNC & Radio.

The battery sits across the power supply via a couple of diodes and light
globe which is used for charging. The digi will normally last for about
24hrs when the mains power fails. All sites with this installation have
the
backup battery jumper in place as it makes the TNC more reliable for
holding
parameter changes.

To ensure the batteries are not damages all sites run a Low Voltage
Cut-out.
This is either a stand-a-lone DSE/Silicon Chip kit or SiteAlert.

With these sites we have never experienced a TNC lock-up.

We have tired and do run 2 digis with very large capacitors across the TNC
power supply to add filtering to the supply and there is no back up
battery.
These 2 TNCs have no backup battery jumper installed. This has been of
limited success as one TNC (VK3RLE-1) recently failed due (we think) to
power supply related issues.

I believe that the Tiny2 is less susceptible to dirty power.

That's our experience.

Hope it helps.

Cheers
Richard
VK3JFK

> -----Original Message-----
> From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
> Behalf Of Dave Ingram
> Sent: Thursday, 18 October 2007 12:28 AM
> To: VK / ZL APRS Users
> Subject: Re: [OZAPRS] Problems with APRS in SE Qld
> 
> Andrew Rich wrote:
> > And what gets me is this.
> >
> > Those owners of the offending digis have installed UI-DIGI.
> >
> > Which has a remote function. You can change the parameters remotely.
> >
> > They stick until you have a power bump.
> 
> Which is happening quite a lot these days with the storms. I don't know
> what
> backup power is setup at the digis, but a UPS (even the $100 DSE ones)
> might
> be a good investment.
> 
> Most outages are 20 seconds when the 11kV feeder has auto-reclose. If
the
> wires are on the ground, the lights stay out, but if the problem is a
> lightning strike, windborne debris or wildlife then the 20s pause is
often
> long enough for the problem to go away or fall down.
> 
> 
> Dave.
> --
> David Ingram (VK4TDI)
> Real email: dave at ingramtech dot com
> Brisbane, Queensland, Australia
> http://www.ingramtech.com/
> MGRS: 56J MQ 991583    Maidenhead Grid Square: QG62lm
> _______________________________________________
> Ozaprs mailing list
> Ozaprs at aprs.net.au
> http://aprs.net.au/mailman/listinfo/ozaprs

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