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[aprssig] Re Net28

Dave Baxter dave at uk-ar.co.uk
Mon Jun 14 12:55:51 UTC 2010


Hi.

The actual tone freq's from the TNC do not matter, be they 1600/1800 or
2100/2300, 2400/2600 or whatever, the shift is still 200Hz, the only
reason you need to know them (what *Your* kit is using) is to adjust
your radio's dial frequency, so the RF frequencies used are the same as
everyone else.   Just because one person is using one set of tones, does
not matter, so long as you know what yours are, to tune to the correct
Dial freq' for the RF frequency used.

It would make more sense to use USB on 10m, as others have said, most
Ham kit will default to USB if they do not have a specific "data" mode,
and much ex commercial (and some military) kit just will not do LSB at
all.  (At least, often not without a lot of hassle.)

Much digi mode computer software will do all that for you, so long as
you tell it what the rig dial and sideband settings are, or you let the
software control the radio.  Job done.

I believe the convention used to be, to quote the 'Mark' state (idle)
frequency as the reference freq' at RF, and if the shift was Up or Down
for the 'Space' state.  (The RF frequency shift, not the Sideband mode.)

In any case, I was under the (mistaken?) impression, that much of HF
APRS used a PSK type modulation, where the USB/LSB problem does not
exist, as it's the changes of phase that convey the information, not
relying on discrete frequencies and shifts.

Or did I skip something, again......

73.

Dave G0WBX.



> -----Original Message-----
> From: ke7xo [mailto:ke7xo at cox.net] 
> Sent: 13 June 2010 18:57
> To: TAPR APRS Mailing List
> Subject: Re: [aprssig] Re Net28
> 
> I own two KAM XL's and they default to 2100/2300 for 300 baud 
> packet, NOT 1600 and 1800.
> 
> Richard
> 
> 
> 
> On 6/13/2010 7:29 AM, G0JXN Jim wrote:
> > Hi Guys
> >
> >
> >
> > Stephen, I am of course aware that USB is used for phone 
> above 10MHz 
> > but was under the impression, perhaps wrongly, that data 
> was specified 
> > as a LSB frequency. But no problem, the 300bd KAM tones are 
> 1,600 and 
> > 1,800 Hz, so centre frequency 1,700 Hz. For USB move the 
> dial setting 
> > down twice that figure:-
> >
> >
> >
> > 28.140 MHz - 3,400 Hz = 28.136,600 MHz.
> >
> >
> >
> > For PK-232 (AGWPE, the free one) subtract 510 Hz, i.e. 
> 28.136,090 MHz.
> >
> >
> >
> > 73
> >
> >
> >
> > Jim, G0JXN/MB7UXN
> >
> >
> >
> >
> >> Stephen, WA8LMF Wrote:-
> >
> >> I think you should consider expressing the frequency in 
> question in 
> >> terms of it's USB equivalent.
> >>
> >>    * LSB operation is almost unheard of on 10 meters (at 
> least in North
> >>      America).
> >>
> >>    * All radios default to USB mode on this band. Many 
> require multiple
> >>      button pushes or menu levels to switch to the non-default LSB.
> >>
> >>    * Nearly all  commercial, marine, and military-surplus 
> SSB radios
> >>      (that hams sometimes acquire second hand) ONLY operate on USB.
> >>
> >>
> >> Or better yet, specify the actual RF mark/space freqs so 
> that users 
> >> with devices that have odd tone pairs such as the 
> TigerTronics TigerTrack
> >> (1100/1300 Hz audio tones),   or fully variable tones 
> (such as the MixW
> >> soft modem on packet),   can calculate what RF freq [USB 
> or LSB] to use.
> >>
> >> Note further that the paid-for "Pro" version of AGWpe can use 
> >> standard KAM tones (1600/1800).
> >>
> >> Stephen H. Smith    wa8lmf (at) aol.com
> >
> >
> > _______________________________________________
> > aprssig mailing list
> > aprssig at tapr.org
> > https://www.tapr.org/cgi-bin/mailman/listinfo/aprssig
> >
> 
> 
> 
> 



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