[OZAPRS] test drive
vk2tv at exemail.com.au
Sun Apr 27 08:18:28 EST 2008
Michael and others,
You've raised something I've been wondering about since I installed
vk2rmc-1. In voice repeater days we tended to work around a 25 W mobile
as being "the standard" but what is that "standard" for aprs.? One reads
about users with hand helds, and possibly (hopefully!!) an exteranal
antenna on the car.
I tend to think that 25W mobiles may not predominate in aprs,
particularly when one reads of the integrated trackers with their low
power transmitters. There's not much point planning coverage with every
one a 25W mobile if a significant number use less than this.
The FM828 seems to predominate at repeater and aprs sites, and why not,
it's a trusy, reliable workhorse, and receiver sensitivity, at about
0.25uV, isn't too bad either. The receiver has good performance
characteristics at busy sites. The tx output is 25W. That combination is
a good match to a 25W mobile. However, to "match" that receiver to a 5W
aprs station requires that the rx be about 6dB better, or 0.12uV. A
decent pre-amp can provide that lift but can create its own new
problems, especially at a high density site with loads of RF flyng about.
I've been doing lots of site coverage plots and have used 25W as the tx
power. Given, however, that an aprs digi is more about hearing than
being heard, perhaps the plots should be done at 5W, or maybe 10W as a
compromise, to provide a more realistic result.
Michael Brown VK2ZEN wrote:
> Oh dave dave dave, with just 5 watts your making shots in from
> Clarencetown, thats utterly exceptional. Previously we were sending
> 30 watt vehicles north and there would be nothing at all after
> Grahamstown Dam, and they'd go totally patchy after just the Hexham
> bridge. That is seriously stunning what you have been able to do with
> 5 watts.
> You are the first to test north since the RTZ digipeater has been
> installed on Mt Sugarloaf. Well done and thank you muchly for the test.
> More tests going north would be greatly appreciated by anyone, the
> more power the merrier.
> Be,seeing you.
> Dave Walmsley wrote:
>> Apart from issues with dropouts, looks like coverage dies outside
>> ----- Original Message ----- From: "Dave Walmsley"
>> <dave at hunterlink.net.au>
>> To: <ozaprs at aprs.net.au>
>> Sent: Saturday, April 26, 2008 11:14 AM
>> Subject: [OZAPRS] test drive
>>> I'll shortly be driving to Dungog, with the Foxtrack feeding a 5W
>>> Alinco HH and a 1/4 wave on the car roof. Be interested to see how I
>>> get out and what the coverage is.
>>> Ozaprs mailing list
>>> Ozaprs at aprs.net.au
>> Ozaprs mailing list
>> Ozaprs at aprs.net.au
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