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ZL3AI > APRDIG 07.04.07 06:06l 257 Lines 9166 Bytes #999 (0) @ WW
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From: ZL3AI@ZL2BAU.#79.NZL.OC
To : APRDIG@WW
Message: 8
Date: Wed, 4 Apr 2007 18:31:23 -0400
From: "Stephen Brown Jr" <stephen.brown75@gmail.com>
Subject: Re: [aprssig] Deviation meters
Scott, if you engineer this one yourself, I think you should proudly
proclaim it the "Open Deviator"
*snicker*
73's
Stephen
K1LNX
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Message: 9
Date: Wed, 04 Apr 2007 15:58:08 -0700
From: "Stephen H. Smith" <wa8lmf2@aol.com>
Subject: Re: [aprssig] Deviation meters
scott@opentrac.org wrote:
> I'd like to be
>able to point people to an affordable option that's somewhere between the
>extremes of 'service monitor' and 'set it by ear'.
The peak voltage seen at the receiver discriminator is proportional to the
transmitted deviation (at least as long as you don't deviate beyond the RX
passband). On any radio with direct discriminator access, such as through
the 6-pin mini-DIN data/packet jack, a deviation meter could basically be a
calibrated AC millivoltmeter. I envision something like a microcontroller
with an A/D input driving a multi-segment bargraph LED via multiple single
bit output lines. If you want to get fancy, one could have a
RED-YELLOW-GRN -GRN-RED sequence to corrrespond to 1 through 5 KHz peak
values.
Calibrating this device to the output of a particular radio's discriminator
output would be fairly easy. While receiving a constant unmodulated
carrier, switch the radio up or down 5 KHz. The resulting constant voltage
change on the discriminator output is the same as the peak voltage change
would be under 5KHz peak deviation with audio.
One could have a cal program similar to the config program for an OpenTrack
or TinyTrak that would prompt the user to first switch the radio up 5 KHz
to read the delta in discr voltage. It would then prompt the user to press
"-" or "+" until the top LED in the display just lights up, establishing a
multiplier constant for the value read from the A/D converter.
If you plug this device into a "DC-to-light" radio like an Icom 706, FT-100
or TS-2000 or a VHF/UHF multibander like a D700 (all have the direct
discriminator data/packet connector) one could read deviation on any band.
Of course, one could just connect a peak-reading AC voltmeter to the packet
jack after determining what DC voltage is created by tuning 5 KHz off
frequency.
--
Stephen H. Smith wa8lmf (at) aol.com
EchoLink Node: 14400 [Think bottom of the 2M band]
Home Page: http://wa8lmf.com --OR-- http://wa8lmf.net
NEW! World Digipeater Map
http://wa8lmf.net/APRSmaps
JavAPRS Filter Port 14580 Guide
http://wa8lmf.net/aprs/JAVaprsFilters.htm
"APRS 101" Explanation of APRS Path Selection & Digipeating
http://wa8lmf.net/DigiPaths
Updated "Rev H" APRS http://wa8lmf.net/aprs
Symbols Set for UI-View,
UIpoint and APRSplus:
------------------------------
Message: 10
Date: Wed, 4 Apr 2007 19:37:08 -0400
From: "Robert Bruninga" <bruninga@usna.edu>
Subject: RE: [aprssig] Deviation meters
>one for sure! I have 2 radios going full time with
>packet/aprs and just set them both till "they worked", it
>would be better to use a meter to set it more accurately.
Tongue-in-cheek:
Setting by ear is easy. Listen to your packets, then turn the TX deviation
down until you don't hear distortion. Then turn it down some more. Then
turn it down some more. Then turn it down until the tone sounds pure and
clean, NOT a BRAPP!. Then turn it down some more. Then turn it down some
more.
Then one might start getting better success rate out of their packets..
Hi HI
Bob, WB4APR
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Message: 11
Date: Thu, 5 Apr 2007 11:07:50 +1000
From: "Richard Hoskin" <vk3jfk@amsat.org>
Subject: RE: [aprssig] Deviation meters
Scott,
Here we have a packet on-air deviations test device.
It's a TNC that measure and reports back to you your deviation when you
connect to it. It also produces an MHeard list with a deviation columb.
I think it uses a function in NETROM that was available if you provided
additional hardware and tapped the discriminator of the radio.
Cheers
Richard
VK3JFK
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Message: 12
Date: Wed, 4 Apr 2007 23:33:44 -0500
From: "Alan P. Biddle" <APBIDDLE@UNITED.NET>
Subject: RE: [aprssig] Deviation meters
Scott,
Back in the Dark Ages, about 15 years ago or so, TAPR produced a very nice
deviation meter kit. It plugged into a VHF-UHF scanner which RS was making
at the time, but could be made to work with other radios with possibly some
changes in the programming. I still have mine, and it is absolutely
necessary for setting deviation at 9600 baud. It could probably be done
even simpler with today's generation of chips.
Alan
WA4SCA
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Message: 13
Date: Thu, 05 Apr 2007 17:16:28 +1000
From: Ray Wells <vk2tv@exemail.com.au>
Subject: Re: [aprssig] Deviation meters
'Scott Miller' wrote:
>>Audio drive to the transmitter play an equally, and maybe more,
>>important role.
>>
>And this is really what I'm hoping to come up with a tool to set - i.e., set
>your tracker/TNC to calibrate mode (alternating tones) and set the audio
>drive level to get appropriate deviation. Assuming the transmitter's not so
>out of whack that at 3.2 kHz deviation it's clipping the high tone already.
I wish you success. Such a tool will be greeted with much enthusiasm.
>>More important is having the transmitted amplitude of the two
>>tones in
>
>You're preaching to the choir. =]
But it's amazing how many are not in the choir!
>Of course, as long as we've got D700's
>and such out there, there's no getting around the fact that some stations
>will transmit with no pre-emphasis. I made a point of adding a pre-emphasis
>circuit to my T2-135 board, since the DR-135T doesn't provide pre-emphasis
>on the TNC input (not the one from the internal header, anyway). I may add
>a jumper on future versions to bypass it if needed, though.
It certainly complicates matters when mixed standards are employed on
the same network.
>>In the absense of a service monitor or oscilloscope, and if a simple,
>>peak reading device is used, adjust the audio drive until the desired
>>level is achieved, then back it off just a tad.
>
>This is what I've encouraged users to do. Still, it'd be nice to have a
>small board that'd give you at least a basic indication that you've got it
>set right, even if it wasn't very sensitive and required the radio to be
>tuned to a known frequency. I've got an Agilent service monitor, myself,
>and it's wonderful for checking my relative tone levels and deviation, but
>even used and several years old it was more than $3,000. I'd like to be
>able to point people to an affordable option that's somewhere between the
>extremes of 'service monitor' and 'set it by ear'.
Like yourself, I have a service monitor, a Motorola R2400, but we're
amongst a lucky minority.
I think that an oscilloscope is the most useful tool one can have for
making audio adjustments, and with software scopes available, such a
tool is within the reach of most. If one can monitor a "known"
transmitter (or transmitters), it's fairly elementary to adjust one's
own. Such a method does not return a precise deviation result but it's a
whole lot better than guesswork.
Ray vk2tv
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Message: 14
Date: Thu, 5 Apr 2007 02:40:07 -0700
From: "Ray McKnight" <shortsheep@worldnet.att.net>
Subject: RE: [aprssig] Deviation meters
>Like yourself, I have a service monitor, a Motorola R2400, but we're
>amongst a lucky minority.
>
>I think that an oscilloscope is the most useful tool one can have for
>making audio adjustments, and with software scopes available, such a
>tool is within the reach of most.
>
>Ray vk2tv
The sad reality is that 90% of US Hams are not accessing APRS via RF, but
the Innerdnet. Yes, simple basic test equipment is useful for setting
things like deviation. Most Hamfests *used* to have test benches set up to
do stuff like that.
In the US, the vast majority of APRS Hams are No-Code Technician's, and the
use of o-scopes and service monitors is well beyond their level of skill.
If they won't invest in a VHF radio/TNC, why bother with test equipment?
Sadly, 99.9% of Hams are more concerned with the number of minutes in their
cell phone plan, not their deviation on APRS. Find a way to make their
cell phone work better and they'll pay attention.
This is why not a single solitary APRS message was sent from downtown New
Orleans over the sole surviving Digi during the aftermath of Hurricane
Katrina. And that Digi was up at like 550ft!
So as an Emergency Service, Amateur Radio might as well be a drum and smoke
signals...
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Message: 15
Date: Thu, 5 Apr 2007 06:54:13 -0700
From: "'Scott Miller'" <scott@opentrac.org>
Subject: RE: [aprssig] Deviation meters
Well, I think at the very least I'll make sure the next T2-135 board has an
ADC connection to the discriminator. With a little bit of calibration,
it'd turn a DR-135T into a deviation meter, with remote measurement
capability.
Scott
N1VG
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