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[aprssig] How About 40M APRS (aka TONE PAIRS, Out-Of-Band etc)

Ray Wells vk2tv at exemail.com.au
Tue Jun 3 09:04:16 UTC 2008


And don't forget that a "common" suppressed carrier dial reading is only 
"common" if we use a "common" tone pair. With so many different tone 
pairs in use there is no "common" dial reading, only a starting point. 
Forget about what the dial says (within reason) and tune for what works 
with your combination of rig and TNC.

The widespread use of HF radio in Australia for outback communications 
has resulted in lots of surplus transceivers that are USB only, this 
being the commercial standard, although most manufacturers had a PCB 
position for the LSB filter as well,  which was seldom used.

Ray vk2tv

Ray McKnight wrote:

>Well, the "indicated dial frequency" is a serious point of debate!
>
>Depending on your particular radio, it may show one of several things.
>
>You NEED TO READ YOUR MANUAL TO DETERMINE EXACTLY WHAT YOUR DIAL SHOWS!
>
>For instance, in my FT-1000D, there is a switch, located underneath an
>Access plate on top of the radio, that allows you to select several
>different tone pairs.  The switch position affects ONLY THE DISPLAYED
>FREQUENCY, not the actual transmit frequency.  If I recall, there are
>Maybe 3 selections, 1600/1800/2100 to correspond to the various TNC's
>Available that were popular at the time this radio was designed (KAM,
>TAPR, AEA, they all have different tone pairs).
>
>I believe there is even a switch position that DOESN'T SHOW OFFSET.
>
>SO... your dial can show whatever the designer intended.
>It doesn't necessarily show carrier frequency, or packet offset
>frequency,
>WHO KNOWS???  Check how your radio is set up, and what the options are,
>and
>What your TNC tones are, and do the simple math.  IF YOU SET YOUR RADIO
>TO THE WRONG SETTING, NOT CONFORMING TO YOUR TNC'S ACTUAL TONE PAIR, THE
>DIAL FREQ MAY BE TOTALLY WRONG, AND YOU'LL HAVE NO CLUE.  Of course, for
>This whole thing to work, you have to know exactly what YOUR tones pairs
>
>really are!
>
>And this affects your ability on most radios to transmit on 10.103MHz.
>THE TRADITIONAL CONVENTION FOR DIGITAL MODES IS ALWAYS LSB.
>But this has been lost because most modern radios automatically select
>USB for upper bands.  It may be necessary to adjust your operation to
>USB and "tune down" to adjust for your tone pair if your radio's CPU
>"thinks" it transmitting out of band.  Or visa versa...
>
>-----Original Message-----
>From: aprssig-bounces at lists.tapr.org
>[mailto:aprssig-bounces at lists.tapr.org] On Behalf Of Dave Baxter
>Sent: Tuesday, June 03, 2008 1:11 AM
>To: TAPR APRS Mailing List
>Subject: Re: [aprssig] How About 40M APRS
>
>  
>
>>The indicated "dial frequency" on SSB is the suppressed carrier
>>    
>>
>frequency.
>  
>
>>The suppressed carrier frequency is NOT transmitted. 
>>    
>>
>
>Point of technicality....   Your "Suppressed" carrier IS still
>transmitted!   Maybe (hopefully!!) many dB down on the wanted sideband
>signals, but it is still there.  If you have some 40dB suppression, &
>many "Amateur" rigs when more than a few years old are not even that
>good!  Just tune around 40m or 80m on a Sunday and listen..
>
>
>
>
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>
>  
>





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