[K6BW] Fw: Terminal Node Controllers

Tue Nov 3 12:42:59 EST 2009

Hi Jay,

My apologies for the delayed response.  Activating the Winlink 2000 RMS
node, tending to CERT Radio politics and building a West Marin repeater site
have taken time recently.

Thank you for the reference to the kc2rlm website.  I took a look, and have
emailed a couple of MARS members who might have more direct experience than
I.  The program has been around since 2003 and suspect that if there were
any 'meat' in it, that we would be using it.  Some of us in MARS have been
looking around for just such software.  Of course it is possible we have
overlooked this resource.  It looks like it will interface only to specially
configured programs, perhaps that has been one limititation.  At any rate,
it looks interesting, but will await their response before commenting
further.

With respect to Part 97, I thought that specific mode regulation had been
replaced with bandwith standards, notably 3 KHz on HF.  I could be mistaken,
but regardless of regulations, phase and fading sensitivity restrict packet
use on HF below 30 MHz.  One can hear packet signals, particularly on 40
meters, but other digital modes are more popular and are more efficient.
9600 baud is practical on VHF, but perhaps limited to the range you
describe.  I don't as yet have experience with 9600 baud, perhaps that may
change if we emplace a VHF Winlink 2000 RMS at Hamilton.

High power 802.11 amplifiers are readily available, if expensive.  Price
seems to increase geometrically with increase in transmit power.  The cost
is no doubt understandable when considering power-bandwidth requirements.
Quite a bit of mileage seems to be available using very low power, however.
We are transiting 2.5 miles with 1/2 watt (500 mw) in our test link.  The
return signal is 3 watts, I believe.  Unfortunately our experience with the
link has been affected by an unreliable connectection to the Internet on the
other end and it has been difficult to develop a good sense of how well it
really works.

Hope to see you this evening at Hamilton.

Sincerely,

Bill
hbco2 at sbcglobal.net
415-456-4481

----- Original Message ----- 
From: Jay Hubert
To: k6bw at mailman.qth.net
Sent: Wednesday, October 28, 2009 8:32 PM
Subject: [K6BW] Fw: Terminal Node Controllers

Bill,

Thanks for the phone discussion today.  I looked at the APRS link you
provided below. While APRS definitely requires a good TNC, I am not sure
that high baud is really an issue for many APRS operations (although some do
operate at 9600 baud).

Look at http://www.kc2rlm.info/soundcardpacket/6modes.htm  The box at the
top of the page indicates that the sampling rate of most sound cards limits
their data throughput to a maximum standard baud of about 19.2 k. This site
seems to have a useful discussion of what it takes to operate at 9600 baud.
Interestingly, some of the links point back to Steve Waterman whom you
mention in your note.  Other links point to some East Bay users. However,
the kc2rlm site is very much committed to and supportive of AGWPE software.
While AGWPE may be the best solution, I would like to have that confirmed
somewhere else.  One of the other comments at the bottom of the page
indicates that at 9600 baud, 10 W transmit power, and with a good antenna,
one might expect a range of about 10 miles.  Marin's geography might limit
range more than that in some places.

I have attached the CFR part 97 rules that clarify packet transmission
speeds.  In summary:

Band                baud    bandwidth kHz
Below 10 m           300          1
10 m                1200          1
6m, 2m             19.6k         20
1.25 m, 70 cm        56k        100
33 cm and above   no limit   no limit

Part 97.309 also clarifies that unencrypted digital protocols are
acceptable, provided that the "technical characteristics have been
documented publicly...for the purpose of facilitating communication."

I appreciate your comment about the 802.11g standard for wireless
networking.  The standard uses spread spectrum transmission at 2400 GHz. The
standard channels fall entirely within the 13 cm amateur band. As near as I
can tell, unlicensed users of the 802.11g transmitters are restricted to 250
mW. The power limitation does not seem to apply to FCC licensed amateurs. Of
course, there could be interference issues because there are many other
users in this band.  However, it seems to me the implementation of 802.11g
at higher power would really be home brew.  Is anyone doing that?

I met a guy in West Marin who has a T1 line that he parcels out to
subscribers who link up to him via radio. I can't imagine that 250 mW is
enough to reach his distant subscribers. I wonder what they are using and
what kind of data rates they get.

Let me know what you think.

Jay
415.457.3914

----- Original Message ----- 
From: Bill Smith
To: jayhubert at comcast.net
Sent: Wednesday, October 28, 2009 8:39 AM
Subject: Re: [K6BW] Terminal Node Controllers

Hi Jay,

An APRS website has a list of equipment which might be useful for you to
review.

http://info.aprs.net/index.php?title=Hardware

I was speaking with Steve Waterman K4CJX a Winlink 2000 expert last night
and he strongly recommends 9600 baud packet.  He mentioned all the current
radio models support 9600 baud (it used to be a real project to tap into the
discriminator and modulator circuits to tease a radio into 9600 baud
operation).  He did mention a MFJ KISS-mode only TNC (didn't mention the
model) as an inexpensive modem option.  MFJ equipment carries a "reputation"
so would look carefully in that direction before taking any steps.

I am really not familiar with current TNC products, especially concerning
9600 baud operation.  A HF (short-wave frequencies) Winlink 2000 RMS node
has just been installed at Hamilton and once it settles down we will be
turning our attention toward installing a VHF RMS node.  As mentioned, Steve
strongly suggested use of 9600 baud with Winlink and from what I can see of
throughput, would very much agree.  Just what equipment will be needed to
support the VHF node is yet to be determined.

I'll try to reach you by telephone to discuss further.  Or, if you have a
chance, give me a call.

Bill
415-456-4481

  ----- Original Message ----- 
  From: Jay Hubert
  To: k6bw at mailman.qth.net
  Sent: Wednesday, October 28, 2009 10:02 AM
  Subject: [K6BW] Terminal Node Controllers

  I would like some local input on selecting a terminal node controller to
use primarily for emergency packet communication.  I expect to use a laptop
(netbook) with a dual band mobile transceiver (Kenwood TMV71E, 144/440 MHz).
I want to be able to connect to local WinLink nodes.

  I realize there are lots of choices, but cost, size, and the need for 110
ac power work against the most powerful and flexible TNCs from Kantronics,
Timeware, RIGblaster, and Pactor.  They also seem to be overkill for my
primary EmComm application. That seems to narrow the choices down to the
RIGblaster Plug and Play, SignaLink USB (contains its own sound card), and
AGWPE Pro (software only).  Roughly speaking, these are all $100 solutions.

  Am I on the right track? What is your experience? What packet modes are
most likely to be used locally? Does anyone have a specific recommendation?

  73 de K0OLK
  Jay

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