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[aprssig] FREQ Object Formats

Bob Bruninga bruninga at usna.edu
Mon May 7 21:32:22 UTC 2012


Ron, thanks for your examples...

From: Ron Stordahl [mailto:ron_n5in at yahoo.com] 

> Here is what I am transmitting for frequency objects 
> which work with the TM-D710A North American version:
>;444.80TRF*111111z4807.60N/09610.63WrT156 + R15m

But, "works" is debatable.  The "+" is not part of the spec.

> The " + " is required, otherwise the D710A does not apply any offset on
UHF.

The D710 needs +500 which is the correct way to do the +5 MHz offset.  The
fact that a bug in that radio might be seeing the + and then not
understanding the following 3 bytes and just defaults to the 5 MHz is just
luck, not part of the spec.

> For VHF I transmit:
> ;146.85TRF*111111z4804.29N/09606.79WrTOFF - R40m
> For VHF ' - ' is not required, 

Since it is not in accordance with the spec, it just adds confusion and a
perpetuation of non-spec compliant packets on the air.  In North America,
the standard for 147 MHz repeaters is +600KHz offset and 146MHz and below
have -600 KHz offsets.
 
> I am including [the -] to be congruent with the UHF version, 
> which isn't much of a reason I will admit.  I could instead 
> include the offset as +500 and -060 respectively, but since 
> these repeaters use the standard offsets I don't.

Exactly. All of the APRS radios that have the auto-TUNE/QSY function will
use the standard at least on 2 meters and the Yaesu I think does it on both.
But my recommendation is to not transmit the offset in North America on VHF
and to always include the +/-500 on UHF.

> As a check I looked at the first 10 VHF and 10 UHF frequency 
> objects I came across on APRS.FI and only 2 VHF and 1 UHF 
> frequency objects were compatible with the D710A.

Yep, I agree, most FREQ objects on the air are wrong.  SO I am so glad we
are gifinalluy getting everyone's attention.

Bob, WB4APR



________________________________________
From: Bob Bruninga <bruninga at usna.edu>
To: 'TAPR APRS Mailing List' <aprssig at tapr.org> 
Sent: Monday, May 7, 2012 1:59 PM
Subject: Re: [aprssig] FREQ Object Formats

> And a close second... is people transmitting a
> frequency OBJECT with the SAME frequency duplicated 
> in the comment of the object. 

That is simply wrong.

> According to the spec (which I'm hoping to change), 
> this second frequency is the RECEIVE frequency.  

But only for CROSS Band or odd-splits.

> I'd like to see the receive frequency always require 
> the FFF.FFFrx and allow the (albeit redundant) specification 
> of the primary frequency in both the object name and 
> position beacon since that's how most of the world is doing it

Then they are doing it wrong.  A complete waste of bandwidth when the
comment text is supposed to convey additional USEFUL information.  Typicaly
the extra bytes should be used for Weekly NET times and monthly Meeting
dates as provided in the spec, not a dublication of the freq which is
already in the packet.

> The current spec at http://www.aprs.org/info/freqspec.txt says:
> If both the object name and the comment contain a frequency, 
> then the name is considered the transmit frequency...
> and the frequency in its comment text is its split receive frequency.

Notice the key word "split" which does not refer to standard offsets.
"Split" only refers to non-standard splits and cross band repeaters in the
context in which I wrote it.  Maybe that needs to be clarified?

> #2) best thing we can do is NOT TRANSMIT ANY OFFSETS IF THE OFFSET IS
> STANDARD.

> This only works, IMHO, if there's a world-wide standard.

But, it does *not* need to be worldwide.  It only needs to be LOCAL.  All
radios sold in areas that have 600 KHz splits all do 600 KHz splits.  All
radios sold in areas that do 500 KHz splits, do 500 KHz splits.  And QSY
Tuning of an APRS radio to a local object is entirely a local process.

> I believe I've read that there is no standard for 70cm repeaters

In the USA, the standard is +/- 5 MHz.  And it amazes me that people feel
the need to indicate MINUS offset when the repeater is above 445 MHz where
the offset can ONLY be MINUS.  And to indicate + offset below 445 MHz where
the offset can only be + or it interferes with the band  plan.

> sake of easy, GLOBAL, interpretation of offsets, I'd propose 
> that we recommend explicit offset transmission.

Not needed in 99% of the cases.  So it is wasteful use of bandwidth.

> The issue with offsets is that some people are beaconing 
> +n.nM to get a MHz offset when the spec says +nnn is in 
> 10KHz units... [there is no] mention of +n.nM (+0.6M for 
> instance) in the specifications...

If people simply followed the spec, everything would work.  And if Kenwood
would implement standard +/- offsets on 70 cm then all our problems would go
away.  Except for the MAJORITY of digipeater manually prepared frequency
beacons that are incorrectly formatted.

Bob, WB4APR



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