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ZL3AI > APRDIG 08.03.04 12:06l 245 Lines 9528 Bytes #999 (0) @ WW
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Subj: TAPR Digest, Mar 06, 1/4
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
TAPR APRS Special Interest Group Digest for Saturday, March 06, 2004.
1. RE: TNC-2 and MFJ-1270 performance
2. Tracker RF susceptibility
3. RE: TNC-2 and MFJ-1270 performance
4. RE: TNC-2 and MFJ-1270 performance
5. Re: Tracker RF susceptibility
6. Re: THE FEEDBACK PROPOSAL
7. Re: THE FEEDBACK PROPOSAL
8. Re: TNC-2 and MFJ-1270 performance
9. RE: TNC-2 and MFJ-1270 performance
10. RE: TNC-2 and MFJ-1270 performance
11. RE: TNC-2 and MFJ-1270 performance
12. RE: TNC-2 and MFJ-1270 performance
13. Re: TNC-2 and MFJ-1270 performance
14. Re: TNC-2 and MFJ-1270 performance
15. Re: [aprsspec] Destination Addresses for Wx Stations andDigipeaters
16. On Star
17. Re: THE FEEDBACK PROPOSAL
18. Another WIDE7-7...
19. RE: On Star
20. Tigertronics TM-1 Pinout
21. Re: Tigertronics TM-1 Pinout
22. RE: TNC-2 and MFJ-1270 performance
23. Destination Addresses thd7ag + gps
24. D-Star ICOM network
25. Re: D-Star ICOM network
26. DSPs
27. RE: Destination Addresses thd7ag + gps
28. Re: D-Star ICOM network
29. Re: TNC-2 and MFJ-1270 performance
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Subject: RE: TNC-2 and MFJ-1270 performance
From: "Scott Miller" <scott@3xf.com>
Date: Fri, 5 Mar 2004 20:59:33 -0800
X-Message-Number: 1
Lots of good info, Mark - thanks. I'm torn between trying to keep the
design as simple, inexpensive, and flexible as possible, and trying to get
the best possible performance. I think the XR2211 might meet my original
goal for a receive-capable tracker, but it might not be adequate for other
uses. I may just use the 2211 for this version, and work on a DSP-based
design later when I've got time to learn that stuff.
>In an ideal world I would use a disk less computer running dos or Linux
>with Digi-Ned with KPC-3 quality decoders that was FIXED in KISS mode.
Definitely the preferable choice. I've got a Soekris single-board computer
here I was setting up as a test platform for exactly that. If I make a
digi-capable tracker device, it'd be mostly intended for fill-in use in
remote spots with solar power.
>PS for testing of decode performance I have two files on my web site. Both
Thanks, I'll check those out. I can do a fair amount of tweaking in Sound
Forge to change pre-emphasis levels for testing. Unfortunately I don't have
a lot of radio test equipment.
Scott
N1VG
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Subject: Tracker RF susceptibility
From: "Scott Miller" <scott@3xf.com>
Date: Fri, 5 Mar 2004 21:34:52 -0800
X-Message-Number: 2
I'm working on a problem with my prototype trackers and I'm hoping someone
can give me some advice. When running high power (5 watts) with the antenna
within a foot or so of the device under test, I start getting some weird
effects.
I'm familiar with basic electromagnetic compatibility design rules -
decoupling, minimizing current loop areas, and so on - but what I know is
mostly geared toward reducing noise within and between boards, not dealing
with several watts of RF in close proximity.
My most immediate problem is how to trace what's happening. As soon as I
get the 'scope probe close to the transmitter, it starts reading something
like 100 volts DC. Makes it hard to see what's going on. Suggestions,
anyone? I'm pretty sure I can get a handle on the problem if I can get some
real readings.
Scott
N1VG
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Subject: RE: TNC-2 and MFJ-1270 performance
From: "Stephen H. Smith" <WA8LMF2@aol.com>
Date: Fri, 5 Mar 2004 21:42:08 -0800
X-Message-Number: 3
Scott Miller wrote on 3/5/2004, 8:59 PM:
>I can do a fair amount of tweaking in Sound
>Forge to change pre-emphasis levels for testing. Unfortunately I
>don't have
>a lot of radio test equipment.
>
>Scott
>N1VG
Your're up in the Vandenberg AFB area aren't you? When you are ready to
do some performance shootouts, I could take a ride up there with my
IFR-1500 service monitor. {I'm in Pasadena and could always use an
excuse for a trip to the SBA/Lompoc area) I've fed Mark's packet test
signals into my 1500's external FM mod input in the past with great
success.
On another subject, I thought the Paccom and the MFJ 127x were virtually
identical -- basically copies of the TAPR standard board with minor
changes. (I've never actually seen a PacCom)
[Mark] What do you attribute the superior performance of the PacCom to?
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
Ham Radio/Mobile SSTV page: http://members.aol.com/wa8lmf/ham
APRS Stuff
http://members.aol.com/wa8lmf/aprs
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Subject: RE: TNC-2 and MFJ-1270 performance
From: Dale Blanchard <wa7ixk@earthlink.net>
Date: Fri, 05 Mar 2004 22:17:54 -0800
X-Message-Number: 4
> (I've never actually seen a PacCom)
>
>[Mark] What do you attribute the superior performance of the PacCom to?
>
>My Pico- is very consistent in losing its settings. Makes it unusable.
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Subject: Re: Tracker RF susceptibility
From: "Stephen H. Smith" <WA8LMF2@aol.com>
Date: Sat, 6 Mar 2004 01:33:28 -0800
X-Message-Number: 5
Scott Miller wrote on 3/5/2004, 9:34 PM:
>My most immediate problem is how to trace what's happening. As soon as I
>get the 'scope probe close to the transmitter, it starts reading
>something
>like 100 volts DC. Makes it hard to see what's going on. Suggestions,
>anyone? I'm pretty sure I can get a handle on the problem if I can
>get some
>real readings.
You've got to get the live antenna away from the stuff being tested (or
run the radio into a dummy load)!
RF is getting around the 100:1 attenuator in the probe housing and is
then saturating the 1st amplifier stage (transistor, FET, op-amp, etc)
of the scope's input amplifier. It doesn't take much stray nearby RF to
overcome the few tenths of a volt bias on the typical semiconductor
input stage. The amp then gets driven alternately into cutoff and
saturation on every RF cycle. The net is to rectify the RF and create a
DC offset that shows up as a false indication of 100s of volts. Either
there is a lot of capacitive coupling around the attenuator resistors in
the probe, or the cable is picking the RF downstream from the probe head.
You could try to stop RF currents from following the probe cable by
taking the BNC plug off the end, stringing a bunch of ferrite toroids
with an id of 1/4" on the cable, and then re-attaching the BNC connector.
This is why we RF guys prize and hang onto classic 30-year-old
vacuum-tube voltmeters! Even several volts of RF entering the meter
along with millivolt DC levels isn't enough to overcome the 10's of
volts of negative bias on the grid of a vacuum tube. [ For anyone under
40 or so, grid of a tube = gate of a mosfet ] Since the device never
gets driven into cutoff or saturation, RF just doesn't affect it! The
inertia of the mechanical meter movement simply ignores Mhz AC signals
overlaid on low level DC ones (if they get through the limited bandwidth
of the meter's amp in the first place). I have made DC level
measurements in in finals of live 100 watt transmitters with my
venerable EICO VTVM with no problems.....
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
Ham Radio/Mobile SSTV page: http://members.aol.com/wa8lmf/ham
APRS Stuff
http://members.aol.com/wa8lmf/aprs
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Subject: Re: THE FEEDBACK PROPOSAL
From: db2fm <db2fm@jfsattv.de>
Date: Sat, 6 Mar 2004 12:06:58 +0100
X-Message-Number: 6
I think one thing is overseen in all the proposals:
I found out that most people using excessive pathes here in Europe don't
care about the APRS-IS. They say that IS is not ham-radio.
So any feedback on the APRS-IS will never reach them!
(All statements are my personal experiences out of many conversions in
trying to convince 'long-path-users' to shorten their path!)
73 de Juergen DB2FM
P.S. In my opinion the only point, where you can solve the problem is
at the digipeater. The use of inteligent software like Digi_Ned
that shortens pathes automatically will gain a benefit.
When 'lonp-path-users' see, that theit pathes are shortened anyway
they do not use anymore, them sooner or later.
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Subject: Re: THE FEEDBACK PROPOSAL
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Sat, 06 Mar 2004 09:54:31 -0500
X-Message-Number: 7
>>>Steve Dimse <k4hg@tapr.org> 3/5/04 8:15:13 PM >>>
>Just to be clear, the most important part of my proposal is this:
>My personal take on things is that almost all of these issues can and
>should be handled by Elmerish contacts between local hams.
I agree 100%. But we have been saying that for 12 years now and we still
have the status quo.
I'm not saying my proposal was good or should be done, I only offered it as
a possible additional means to focus on the bad paths and try to find a way
to feedback to those users. Feedback on RF does not work. So FINDU seemed
the next best alternative.
I'm finshed with this idea. Clearly it didnt resonate with you.
Bob
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