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[aprssig] mobile antenna for D7?

'Scott Miller' scott at opentrac.org
Wed Mar 14 19:59:29 UTC 2007


I wasn't aware of the D7 issue, but I know the Alinco DR-135 tends to get
some noise on the speaker from the GPS serial data.  There's definitely some
crosstalk going on.

Don't forget that even with low-speed serial data, you can have fast slew
rates.  A MAX232 will slew from -6 volts to +6 volts in about 1 microsecond.
I wonder if adding some capacitance to the line would help... just dampen
the slew rate out until it's just good enough for the RS-232 receiver in the
radio to work reliably.

Scott
N1VG

> -----Original Message-----
> From: aprssig-bounces at lists.tapr.org 
> [mailto:aprssig-bounces at lists.tapr.org] On Behalf Of Mark Earle
> Sent: Wednesday, March 14, 2007 1:24 PM
> To: TAPR APRS Mailing List
> Subject: Re: [aprssig] mobile antenna for D7?
> 
> Tyson S. wrote:
> > One thing to keep in mind is that NMEA data entering a D7 
> from the cable will degrade your reciever. There are various 
> web sites that explain how you are usually transmitting 
> better than you think while mobile. But I use a regular dual 
> band antenna on my truck with an adapter from SMA to BNC and 
> it works pretty good.
> > 
> 
> 
> Huh? I'm not trying to pick a nit, but low speed serial data causes 
> receiver degradation how?
> 
> What do you mean degradation? Reduced sensitivity? Reduced 
> selectivity? 
> Intermodulation distortion? Overload?
> 
> 
> 
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