[OZAPRS] 10MHz HF Gateway -Re: New to list

[Richard Hoskin]

Mike,

>From looking at the data from VK8ZAB-4 and VK6UZ-4, who I believe are
both
running SCS modems, I'd have to agree that they do a better job of
decoding
300bd HF signals than the MFJs etc.

However we do have a good collection of HF gates on the East Coast that
may
help compensate for the slight frequency inconsistencies.

If the SCS TNCs were a bit cheaper I think they would be a lot more
popular.

Cheers
Richard
VK3JFK

> -----Original Message-----
> From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
> Behalf Of Mike Zwingl oe3mzc
> Sent: Saturday, 8 September 2007 7:52 AM
> To: Ray Wells; VK / ZL APRS Users
> Cc: Friedrich Berrer; hf14.schiller at eduhi.at; Alan (VK8ZAB)
> Subject: Re: [OZAPRS] 10MHz HF Gateway -Re: New to list
> 
> Hi Ray, hi all,
> just to state once again: I am not selling any TNCs and I am not in any
> way
> related to SCS.
> I just had the luck to travel VK6/VK8 and V51 during past years and
using
> such a DSP-TNC in practice.
> 
> I agree with many arguments you mentioned: phase distortion at 300baud
fsk
> is a problem and modern trx are much better than older ones, without
high
> stability TXO.
> However, my experience is that you easily get mislead by the digital
> readout
> of syntesized radios. In most cases if your display reads 10.151,00LSB
you
> will NOT exactly hit the international APRS qrg and subsequently you
will
> not be decoded by PK232 or MFJ or Kantronics or Soundcard, etc...
> Of course you can correct that by undergoing some tests with
> ECHO-digipeaters
> on the band.
> There are other traps in the firmware of modern TRX that might make it
> difficult for users:
>  many trx can adjust a frequency offset to make the voice audio sounding
> more high to improve modulation for dx....
> 
> So to make the long story short: I accept that you think you dont need
> simultaneous decode in a 800Hz channel, but lets agree that it is a
> helpful
> improvement of HF-APRS in 300Baud FSK especially for gateways.
> 
> All the above did not even adress the advantages of using RobustPacket
> mode
> (RPR, OFDM) instead of 300FSK.
> OFDM helps to solve phase distortion problems and multi path, since bit
> duration time is much longer(20msec vs. 3msec). RPR uses 8 carriers with
> abt. 50baud each, and efficient encoding with FEC and random
interleaver.
> Here is some example from Africa: During 7 weeks in V51  I transmitted
my
> posit alternating 300FSK and RPR (same qrg and same number of packets at
> time, same trx, same antenna)  and had two gateway stations in ZS1 (Cape
> Town) to receive:
> ZS1TX in 300FSK received and decoded 141 posits in 7 weeks,
> ZS1AAZ in RobustPR received 1647 posits in same period.
> 
> So I know that good old proven technology is still doing the job, but
> there
> is new technology that does it even better, and thats what amateur radio
> is
> all about, isn't it?
> No worries.
> tnx fer reading
> vy 73 de Mike
> oe3mzc
> ex vk3fpf
> 
> PS: some snapshot from the HF-APRS QRG in Europe- see I-GATEs having
> frequency offset from +50Hz to -50Hz , some users are +171Hz off:
> * %m
> DIRECTLY RECEIVED HF-PR STATIONS:
> F6DDV-4 -9 Hz, EA6XQ-3 -18 Hz, RELAY +6 Hz, UA1ATI +12 Hz
> SL5ZL -25 Hz, DF4FO -25 Hz, DF4FO-3 -25 Hz, F5KCN-3 +43 Hz
> OE3MZC-4 +0 Hz, WIDE +0 Hz, WIDE4 +50 Hz, EA6XQ-5 +0 Hz
> G0JXN-10 +9 Hz, HB9MM-4 +9 Hz, F6DDV +0 Hz, F5ZQB-3 +50 Hz
> WIDE3 +0 Hz, F6KCF-10 +0 Hz, G0IQK-10 -25 Hz, F6KOB-4 +25 Hz
> OZ4DX -43 Hz, EA6XQ-1 +0 Hz, EA6AFM +0 Hz, OK2PEN -28 Hz
> EC2A-1 +25 Hz, EB2EMZ-8 +25 Hz, W1ON -6 Hz, OE3XMU-4 -15 Hz
> DL1HXB -25 Hz, OE3XMU -9 Hz, AA1XD -25 Hz, W1JMC -50 Hz *
> OE3WTS-15 +171 Hz, SP9UX +59 Hz
> 
> 
> ----- Original Message -----
> From: "Ray Wells" <vk2tv at exemail.com.au>
> To: "Mike Zwingl oe3mzc" <oe3mzc at oevsv.at>; "VK / ZL APRS Users"
> <ozaprs at aprs.net.au>
> Sent: Friday, August 31, 2007 4:26 AM
> Subject: Re: [OZAPRS] 10MHz HF Gateway -Re: New to list
> 
> 
> > Mike Zwingl oe3mzc wrote:
> >
> >>Gday,
> >>just one comment on HF-APRS Gateway operation:
> >>in practice it is not the signal to noise ratio that decides about
> decode
> >>or nodecode of an APRS beacon on 10Mhz.
> >>
> > I've only been on HF packet for about 8 years so I guess I've still
got
> a
> > lot to learn about it.
> >
> > The two most significant things that affect the ability to decode HF
> > packet are:
> > 1. Noise
> > 2. Phase distortion. Yes, even with just 200Hz shift it can be a real
> > problem. It's more of a problem than noise at my QTH.
> >
> > There is no doubt that a rig that drifts will cause problems, but with
> any
> > modern synthesised rig the stability is excellent and unliley to be a
> > consideration. Even my 23 years old Kenwood TS430 (which I'm currently
> > using for the 30m gate) is more than satisfactory. I know the
reference
> > crystal is off by a100Hz or so but that's another issue that I can
> easily
> > resolve when the need to do so gets to the top of my priority list.
> >
> >>More important is to use a TNC that allows some frequency drift, like
> the
> >>DSP-TNC from SCS.
> >>The DSP-TNC is currently the only hardware that will simultaneously
> decode
> >>several APRS signals at same time in a 800Hz wide channel!
> >>So the frequency offset of a mobile station can be plus/minus 400Hz
and
> >>still have successful decode on 10.147,6 USB (10151LSB)
> >>See the result at VK6UZ-4 and VK8ZAB-4, Fritz and Alan are using these
> >>TNCs.
> >>Most other TNCs/Soundcards require 30Hz accuracy in frequency, which
is
> >>almost impossible to achive.
> >>www.scs-ptc.com/datasheets/scs_datasheet_tracker_english.pdf
> >>vy 73 de Mike
> >>oe3mzc
> >>ex VK3FPF/8
> >>
> > And how many are going to spend big money on another TNC when what
they
> > use works fine. We all know that Pactor-II is better than 0k3 packet
but
> > at near $2000 in Australia for the controller it would want to be.
> >
> > VK6UZ and VK8ZAB are seeing lots of travellers in outback Australia,
> > that's true, but have a look at where the travellers are, and then
> > back-track to when they  were closer to stations in the eastern states
> and
> > you'll see that other stations got hit more often. It's a matter of
> > distance and propagation, not frequency drift in a mobile.
> >
> > Far from being almost impossible to achieve, modern rigs easily
maintain
> > 30Hz acuracy, and better.
> >
> > I've had my TS430 in Central Australia on some of the most horrenous
> > tracks you can imagine - try the flint country from the vk4/vk5
border
> up
> > onto the Lamamour Plateau in South Australia, or the potholes and
> > corrugations on the Birdsville Track just prior to it being graded. At
> no
> > time did I detect the slightest stabilty problems, and I spent a lot
of
> > time listening to  both amateur and broadcast signals  (in SSB mode)
> while
> > mobile.
> >
> > On could be forgiven for thinking that you're selling those TNC's??
> >
> > Ray vk2tv
> 
> ----- Original Message -----
> From: "Ray Wells" <vk2tv at exemail.com.au>
> To: "Mike Zwingl oe3mzc" <oe3mzc at oevsv.at>; "VK / ZL APRS Users"
> <ozaprs at aprs.net.au>
> Sent: Friday, August 31, 2007 4:26 AM
> Subject: Re: [OZAPRS] 10MHz HF Gateway -Re: New to list
> 
> 
> > Mike Zwingl oe3mzc wrote:
> >
> >>Gday,
> >>just one comment on HF-APRS Gateway operation:
> >>in practice it is not the signal to noise ratio that decides about
> decode
> >>or nodecode of an APRS beacon on 10Mhz.
> >>
> > I've only been on HF packet for about 8 years so I guess I've still
got
> a
> > lot to learn about it.
> >
> > The two most significant things that affect the ability to decode HF
> > packet are:
> > 1. Noise
> > 2. Phase distortion. Yes, even with just 200Hz shift it can be a real
> > problem. It's more of a problem than noise at my QTH.
> >
> > There is no doubt that a rig that drifts will cause problems, but with
> any
> > modern synthesised rig the stability is excellent and unliley to be a
> > consideration. Even my 23 years old Kenwood TS430 (which I'm currently
> > using for the 30m gate) is more than satisfactory. I know the
reference
> > crystal is off by a100Hz or so but that's another issue that I can
> easily
> > resolve when the need to do so gets to the top of my priority list.
> >
> >>More important is to use a TNC that allows some frequency drift, like
> the
> >>DSP-TNC from SCS.
> >>The DSP-TNC is currently the only hardware that will simultaneously
> decode
> >>several APRS signals at same time in a 800Hz wide channel!
> >>So the frequency offset of a mobile station can be plus/minus 400Hz
and
> >>still have successful decode on 10.147,6 USB (10151LSB)
> >>See the result at VK6UZ-4 and VK8ZAB-4, Fritz and Alan are using these
> >>TNCs.
> >>Most other TNCs/Soundcards require 30Hz accuracy in frequency, which
is
> >>almost impossible to achive.
> >>www.scs-ptc.com/datasheets/scs_datasheet_tracker_english.pdf
> >>vy 73 de Mike
> >>oe3mzc
> >>ex VK3FPF/8
> >>
> > And how many are going to spend big money on another TNC when what
they
> > use works fine. We all know that Pactor-II is better than 0k3 packet
but
> > at near $2000 in Australia for the controller it would want to be.
> >
> > VK6UZ and VK8ZAB are seeing lots of travellers in outback Australia,
> > that's true, but have a look at where the travellers are, and then
> > back-track to when they  were closer to stations in the eastern states
> and
> > you'll see that other stations got hit more often. It's a matter of
> > distance and propagation, not frequency drift in a mobile.
> >
> > Far from being almost impossible to achieve, modern rigs easily
maintain
> > 30Hz acuracy, and better.
> >
> > I've had my TS430 in Central Australia on some of the most horrenous
> > tracks you can imagine - try the flint country from the vk4/vk5
border
> up
> > onto the Lamamour Plateau in South Australia, or the potholes and
> > corrugations on the Birdsville Track just prior to it being graded. At
> no
> > time did I detect the slightest stabilty problems, and I spent a lot
of
> > time listening to  both amateur and broadcast signals  (in SSB mode)
> while
> > mobile.
> >
> > On could be forgiven for thinking that you're selling those TNC's??
> >
> > Ray vk2tv
> 
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> Ozaprs mailing list
> Ozaprs at aprs.net.au
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