[OZAPRS] HF frequency drift reports ...?

Ray Wells vk2tv at exemail.com.au
Thu Jun 30 20:41:51 EST 2011


Mike,

No bother at all and I accept your statement re frequency offset being a 
contributor to a lack of success. Setting frequency is difficult because 
too much reliance is placed on a dial reading rather than a "real" 
reading and some rig owners are reluctance to accept that "their" rig 
may not be on the precise frequency indicated on the dial. As a long 
term (until recently) user of crystal locked rigs such as the Codan, I 
have had no option other than to initially set the crystal frequency 
with a Service Monitor and then fine tune with a waterfall display. 
User/potential users should be guided in the use of a waterfall display 
that gives an immediate (when signals are present) indication of 
frequency setting. Perhaps the aprs web page should contain such 
information.

I do accept the improved technology of the smart modem but I can't 
accept that older technology won't do the job most of the time.

Regards,
Ray vk2tv

On 30/06/11 20:31, OE3MZC Mike wrote:
> Ray,
> Accepted.
> I don't want to discourage anyone from using Hf-APRS - on the contrary.
>
> And to be fair- I just stepped into the discussion, because I saw someone's
> MSG saying that he could not enter the network and was asking for reasons
> (Power, antenna...) and in my experience it is often the frequency that is
> not accurate, if you don't get relayed or gated.
>
> It seems to me that the real reason is the price not technology.
> You are asking a sponsorship, I will see what I can do,
> but I have already donated one unit to ZS and one to V51...
> and I am not earning bonus like bankers-hi
>
> Sorry to have bothered you
> 73
> Mike
>
> -----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 12:16
> To: Australian APRS Users
> Subject: Re: [OZAPRS] HF frequency drift reports ...?
>
> Mike,
>
> In my 13.5 years of running a BBS and in my last two years or so of running
> a HF Igate I have found that for 99% of the time there is no need for an
> expensive replacement for a standard, low cost TNC.
>
> Mobile stations managed to access my BBS with a standard rig/TNC and my
> heard list on 30m aprs is normally filled with stations from all over the
> world.
>
> I agree with Scott that, unless some kind person is prepared to donate
> sufficient smart TNC's to cater for the entire Oz aprs network, let's leave
> the hype alone for a while. All you are doing by promoting the smart TNC is
> discouraging users and potential users who have standard equipment that will
> work just fine nearly all of the time.
>
> My comments are based on practical application over a long period of time,
> not some specification sheet.
>
> Ray vk2tv
>
>
> On 30/06/11 19:31, OE3MZC Mike wrote:
>> 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/rele
>> ases/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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