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ZL3AI > APRDIG 04.08.06 09:16l 260 Lines 9512 Bytes #999 (0) @ WW
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From: ZL3AI@ZL2BAU.#87.NZL.OC
To : APRDIG@WW
Message: 6
Date: Sun, 30 Jul 2006 19:10:28 -0700
From: Ben Jackson <ben_at_ben.com>
Subject: Re: [aprssig] Need help testing 30m HF APRS in the Northwest
On Sun, Jul 30, 2006 at 09:18:11PM -0400, Stephen H. Smith wrote:
>
>The actual mark and space frequencies for 30M HF APRS are 10.149.2 and
>10.149.4.
Yes, I'm doing direct FSK at 10.149.200 and 10.149.400.
>Because of the very narrow receive passband of most TNCs
>on 200 Hz shift on HF, you MUST be within 10-20 Hz absolute of the
>correct frequency on transmit.
Well, the transmitter and receiver have to agree within about 20Hz.
How do HF gates generally maintain that <2ppm accuracy?
It may be that a mobile HF APRS beacon is impractical. If so, I'm
learning it the hard way.
--
Ben Jackson AD7GD
http://www.ben.com/
------------------------------
Message: 7
Date: Sun, 30 Jul 2006 22:29:41 -0500
From: Glenn Wiebe <ve4gn_at_mts.net>
Subject: Re: [aprssig] Need help testing 30m HF APRS in the Northwest
Nothing seen here.
73 de Glenn...VE4GN
------------------------------
Message: 8
Date: Sun, 30 Jul 2006 21:11:33 -0700
From: "Ray McKnight" <shortsheep_at_worldnet.att.net>
Subject: Re: [aprssig] Need help testing 30m HF APRS in the Northwest
Well, the *actual* frequencies of HF APRS are subjective. There's the
10.151MHz we all know and love, but that is actually never what you tune
your dial to, *usually*.
I hear several claiming an *exact* or actual dial readout to use. This is
bunk. Every radio/TNC combination can be different. Your problem of not
getting to a DIGI might be either: not being on the correct frequency, or
not having sufficient radiated signal
To determine how your radio/TNC display your actual transmitted frequency
you need to know: what your TNC tone pairs are - MOST tnc's are different!
How your radio handles the display, if it has a "digital" or "packet" mode
that attempts to add/subtract the *assumed* TNC tone from the center
frequency.
As an example, my FT-1000D has several different settings to adjust the
displayed dial freq to try and match the sideband offset of various TNC's.
If I have that set incorrectly my dial freq could be several hundred Hz
off. It also has a true center freq mode, so I can simply do it myself
knowing what the offset is.
On HF, your radiated output can be almost NOTHING, even with hundreds of
watts, but in your case with only a few watts you need to make sure you're
getting out! If your antenna stinks the output power is meaningless. You
can load up a light bulb and the transmitter might be perfectly happy but
no one except your next door neighbor will hear you.
You've made no comments as to what your antenna is and how it's mounted.
Make SURE you're on freq first, then work on the antenna issue.
For all digital modes in the USA, LSB is the standard, BUT most rigs will
not be happy with that since the offset will SEEM to place you outside the
band edge and the rig's CPU will prohibit TX. So you can still go USB and
subtract to get where your dial needs to be.
With only a few watts you SHOULD be getting out most of the time, even with
poor propagation these days, so I'd guess you're not on freq or the antenna
isn't doing it's job.
What TNC did you say you had and what's the tone pairs?
And you rig?
------------------------------
Message: 9
Date: Sun, 30 Jul 2006 21:32:05 -0700
From: Ben Jackson <ben_at_ben.com>
Subject: Re: [aprssig] Need help testing 30m HF APRS in the Northwest
On Sun, Jul 30, 2006 at 09:11:33PM -0700, Ray McKnight wrote:
>You've made no comments as to what your antenna is and how it's mounted.
It's an L-shaped dipole, indoors. It's not quite half wavelength, more
like 48% since I couldn't tune it when it was exactly 1/2. The L points
southeast, which is probably the worst direction based on known digis.
It's tuned with a modified Z-match using a "red LED SWR bridge".
>What TNC did you say you had and what's the tone pairs?
>And you rig?
It's all home built. The idea was to create something very simple for
APRS use only. It's a VCXO at 25MHz - 14.85MHz (SA602A) (both crystals
available at Digikey). The output of that is buffered by a 74HC240
inverter and that drives 4 other inverters. I've used that output
directly (about 400mW w/8V into the '240) and used that to drive an
IRF510 with up to 12V input.
(yes, there's an output low pass filter)
>Make SURE you're on freq first, then work on the antenna issue.
I used a signal generator to zero-beat WWV at 10MHz and used that to
calibrate a frequency counter. I've even swept about 100Hz at 10Hz
increments (constant 200Hz mark/space interval).
--
Ben Jackson AD7GD
http://www.ben.com/
------------------------------
Message: 10
Date: Mon, 31 Jul 2006 00:46:31 -0400
From: "Stephen H. Smith" <wa8lmf2_at_aol.com>
Subject: Re: [aprssig] Need help testing 30m HF APRS in the Northwest
ben_at_ben.com wrote:
>On Sun, Jul 30, 2006 at 09:18:11PM -0400, Stephen H. Smith wrote:
>
>>The actual mark and space frequencies for 30M HF APRS are 10.149.2 and
>>10.149.4.
>>
>
>Yes, I'm doing direct FSK at 10.149.200 and 10.149.400.
>
>
>>Because of the very narrow receive passband of most TNCs
>>on 200 Hz shift on HF, you MUST be within 10-20 Hz absolute of the
>>correct frequency on transmit.
>>
>
>Well, the transmitter and receiver have to agree within about 20Hz.
>How do HF gates generally maintain that <2ppm accuracy?
>
>It may be that a mobile HF APRS beacon is impractical. If so, I'm
>learning it the hard way.
It's quite easy for any modern HF transceiver with a TCXO master
standard for it's synthesizer to maintain +/5 Hz or better indefinitely
on mid HF freqs. For old mechanical VFO rigs like TS-820s or early
synthesized rigs, fugetaboutit !
I have no trouble using my Yaesu FT-100 with the optional hi-stability
standard as a mobile APRS tracker on 30M. [The FT-100D has the
high-stab osc as standard equipment.] Any recent rig such as an
IC-702, FT-897, etc with it's high-stab option will have no problem.
If you are doing direct FSK of a simple crystal osc rig, put the crystal
in a oven, let it reach a stable temp for a few hours and then calibrate
it.
In the constant room-temp environment of my house, I am using a Kenwood
TS-50 with standard osc as an HF monitor/igate. It has stayed on freq,
as verified against my IFR-1500 service monitor (good to about 1 Hz at
HF) for almost two years now without tweaking.
--
Stephen H. Smith wa8lmf (at) aol.com
EchoLink Node: 14400 [Think bottom of the 2M band]
Home Page: http://wa8lmf.com
NEW! JavAPRS Filter Port 14580 Guide
http://webs.lanset.com/wa8lmf/aprs/JAVaprsFilters.htm
UI-View Misc Notes and FAQ
http://webs.lanset.com/wa8lmf/aprs/UIview_Notes.htm
"APRS 101" Explanation of APRS Path Selection & Digipeating
http://webs.lanset.com/wa8lmf/DigiPaths
Updated "Rev G" APRS http://webs.lanset.com/wa8lmf/aprs
Symbols Set for UI-View,
UIpoint and APRSplus:
------------------------------
Message: 11
Date: Mon, 31 Jul 2006 09:02:37 -0400
From: "Robert Bruninga" <bruninga_at_usna.edu>
Subject: Re: [aprssig] Need help testing 30m HF APRS in the Northwest
Ah, I missed that!
Yes, I am all for experimenting and hearing a digipeat is the best way to
know it is getting out. As long as it is a limited operation. I saw the
receommendation to use ECHO without those caveats and I think everyone
agrees it is not a good idea for routine operations.
On the other hand, it coiuld be argued again, that ECHO which can cause
multiple digipeates and then collisions, will not be decodable in response,
so nothing will be seen. Might be better to have the intended recepient
callsign for the digipeat and then only one station (the desired one) will
digipeat and he will get a good signal.
Bob
------------------------------
Message: 12
Date: Mon, 31 Jul 2006 09:14:03 -0400
From: "Robert Bruninga" <bruninga_at_usna.edu>
Subject: Re: [aprssig] Need help testing 30m HF APRS in the Northwest
>>On HF, The recommended path was always
>>VIA GATE,WIDE and now that should be VIA GATE,WIDE1-1.
>
>GATE,WIDE1-1 is like saying GATE,RELAY.
>Is that really what you intended?
>Or would did you mean GATE,WIDE2-1?
Yes, either or both. WIDE1-1 is equivalent to WIDE2-1 since it is simply a
single hop. And a single hop is all that we ever want to see on VHF after
coming through a GATE from HF to VHF.
Why a single hop? Because in an APRS national network, point-sources of
injected out-of-area-packets must be managed at the LOCAL level. IE, in
the own-backyard of the source. This same thing holds for IGates and any
other PC that decides to inject out-of-area-packets into his local network.
I wish everyone would do their network planning this way. This way, the
QRM from such injections only affects the "local" area of the source, and
the LOCALS can go put pins in the guy's coax if he is messing up the
network.
But if he is 100 miles away and QRMing half of the state, but he lives in a
rural area with no-one nearby to go pound on his door, then the problem
festers for months if not years.
So, best to keep injected packets LOCAL. If that does not cover the
desired area, then add *another* injection point over where it is needed.
SOmething like that anyway...
That is why I think that ALL IGates should only use a SINGLE hop for their
APRS-IS==>RF packets..
Bob, WB4APR
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