[OZAPRS] HF frequency drift reports ...?

Thu Jun 30 19:31:38 EST 2011

Hi Ray,
all,
I appreciate the discussion on this topic and accept your opinion.
It is fair to say, that you can use a modern synthesized rig for Hf-APRS, of
course,
But your statement also confirms my findings: you need to be within
plus/minus 40Hz- let's say 50Hz ok...
depending on signal/noise ratio, signal levels and other distortion from
230V/50Hz..
If you doing at home, you can use a soundcard with waterfall display or
other means of tuning, no problem.

If you do mobile out in bush things are much more complicated.
Assume you use a TinyTracker or Opentracker and a FT857 or similar.
The frequency in display will often be more than 100Hz offset from real
channel and the only way of tuning is to use the ECHO- command in the
digipath - which requires a laptop to change settings when driving again...
And considering drift caused by temperature changes in car you might add
another variable to the equation.

However it would be much easier for mobiles if more I-Gates would have
800Hz"wide band" receive capabilities...10times better.
I think there is not just the SCS DSP-TNC that can do this, but also some
software for soundcard from G4hyg
http://www.crosscountrywireless.net/aprs_messenger.htm
but I am not sure...

Just for records: I am not related in any way to SCS, but using such a
device for years on Gateway OE3YCB-4 and OE3XUR and comparison to old type
Packet-Tncs is obvious.
http://www.scs-ptc.com/downloads/pscproject.2008-09-29.7249707140/releases/1
.0/scs-datasheet-tracker-english.pdf 
I have crossed Australia and Africa in 4WD using HF-APRS...so some level of
experience ...not just "hot-air" -hi

Vy 73 de Mike
VK3FPF/OE3MZC

-----Original Message-----
From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
Behalf Of Ray Wells
Sent: Donnerstag, 30. Juni 2011 10:35
To: vk2io at amsat.org; Australian APRS Users
Subject: Re: [OZAPRS] HF frequency drift reports ...?

All,

I believe my HF rig has done a dummy spit with regard to frequency. I've not
logged anything since Sunday - been too busy to do daily mheard checks.

Overall this concern over frequency accuracy is nothing but hot air. As
someone who has used HF packet for near 14 years (mostly as a BBS), all I
can say is that for most of the time the frequency accuracy of the average
synthesised amateur rig is more than accurate enough to achieve excellent
results.

Whilst the benefits of an expensive modem that tracks frequency cannot be
denied, such a unit is not necessary for good HF packet performance.

Historically I have used a waterfall display to "net" my radio and that
method returns excellent results. Like others on this forum I seriously
doubt the frequency that's being used by VK3MY - I have always observed it
to be lower than other stations by about 40Hz. I net to the average and,
despite VK3MY being about 40Hz low I logged 2100 packets from him in seven
days. So much for the 10Hz frequency accuracy requirement suggested in this
forum. I've found that +/- 20Hz is good enough and, if signals are clean, up
to 50Hz error will work.

If I get a chance I'll switch from the FT747 back to the TS430 over the
weekend.

Ray vk2tv

On 30/06/11 14:01, Gerard Hill wrote:
> Hi Terry,
>
> I would not be too concerned. Frequency reports in the list do not 
> seem to expire, so they'll stay there until reset. I think the list 
> was reset or is not being transmitted at the moment because the beacon has
stopped.
>
> Sending the report is a good idea - thanks VK6UZ! Its an automated 
> system though so you need to do your own verification. For example, I 
> am sure that VK2TV-4 is not 143 Hz low. Other entries in the list are, 
> as far as I can tell, reasonably accurate with a slight tendency to 
> report too low a frequency.
>
> Oh and Dave, I miss VNG too. Used to use 7.5 MHz reference a lot.
>
> Cheers ... Gerard, VK2IO
>
> On 30/06/2011 1:23 PM, Terry Neumann wrote:
>>
>> It doesn't take a lot to confuse me these days. OK I'll admit it. I 
>> am confused by the list of stations Mike has copied below.
>>
>> I've checked for myself and that's more or less what the site is 
>> delivering in real time at this moment.
>>
>> My station is one of those listed with today's date. It hasn't been 
>> on HF APRS since I returned from our Flinders Ranges trip over a 
>> couple of weeks ago:
>>
>> http://aprs.fi/?call=vk5atn-15&mt=m&z=11&timerange=86400
>> <http://aprs.fi/?call=vk5atn-15&mt=m&z=11&timerange=86400> gives the 
>> true picture. It's in the shed with the HF rig off and the 20 metre 
>> whip on the bar. (I just checked)
>>
>> So why is it appearing in the lists for today? And all of those going 
>> back over the past day or so?
>>
>> Simple answers only please - type slowly .......
>>
>> Puzzled 73
>> Terry
>>
>>
>> Date: Wed, 29 Jun 2011 13:37:07 +0200
>>> From: "Mike Zwingl oe3mzc"<oe3mzc at oevsv.at>
>>> Subject: [OZAPRS] QRG drift HF APRS
>>> To: "Australian APRS Users"<ozaprs at aprs.net.au> 
>>> Message-ID:<00ed01cc3650$e08f6800$cda8a8c0 at WORKSTATION>
>>> Content-Type: text/plain; charset="iso-8859-1"
>>>
>>> see how all stations on 10Mhz are drifting offset in QRG:
>>> http://aprs.fi/?c=raw&call=vk6uz-4
>>> It is not the absolute but the relative value to each other that 
>>> makes the problem in decoding hf-aprs sigs.
>>> (values after callsigns is given in Hz)
>>>
>>> 2011-06-29 11:24:57 UTC:
>>> VK6UZ-4>APU25N,TCPIP*,qAC,T2AUST:=3211.17S/11604.17E&HF-IGATE
>>> 10147.6USB Perth
>>> 2011-06-29 11:29:01 UTC: VK6UZ-4>APRS,TCPIP*,qAC,T2AUST:>dF (Hz):
>>> WIDE1 +100, VK2GKA-15 +50, VK7BW-15 +50, VK8ZAB-4 +25
>>> 2011-06-29 11:29:02 UTC: VK6UZ-4>APRS,TCPIP*,qAC,T2AUST:>dF (Hz):
>>> VK4UN-4 +62, VK5ATN-15 +65, VK5LY-15 +43, VK4KWI-15 +75
>>> 2011-06-29 11:29:02 UTC: VK6UZ-4>APRS,TCPIP*,qAC,T2AUST:>dF (Hz):
>>> VK2AJ-15 +50, KF7EU-6 +25, ZS6SS-3 +62, VK2TV-4 +143
>>> 2011-06-29 11:29:02 UTC: VK6UZ-4>APRS,TCPIP*,qAC,T2AUST:>dF (Hz):
>>> VK3DHI-15 +68, VP8DEU +43, VK2DQC-15 +81, VK4DMI-4 +96
>>> 2011-06-29 11:29:02 UTC: VK6UZ-4>APRS,TCPIP*,qAC,T2AUST:>dF (Hz):
>>> VK4HW-15 +46, VK4VP-15 +25, DL8RCB-3 +100, IW2GOB-10 +100
>>> 2011-06-29 11:29:02 UTC: VK6UZ-4>APRS,TCPIP*,qAC,T2AUST:>dF (Hz):
>>> VK4KMR-15 +46, F5LDS-4 +112, VK2SX-15 +50, LA4FPA-15 +87
>>> 2011-06-29 11:29:02 UTC: VK6UZ-4>APRS,TCPIP*,qAC,T2AUST:>dF (Hz):
>>> VK7DIK-4 +40, VK3MY-4 +65, VK3BZQ-9 +37, VK5LY-4 +43
>>> 2011-06-29 11:29:02 UTC: VK6UZ-4>APRS,TCPIP*,qAC,T2AUST:>dF (Hz):
>>> VK4UN-15 +43, VK8LM +50, VK5LY-6 +50, VK3BDG-9 -18
>>>
>>
>>
>>
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