QRZ! Ham Radio 7/QRZ Ham Radio Callsign Database - Volume 7.iso/mac/files/p_misc/hispeed.txt

Text File | 1994-11-27 | 21KB | 486 lines

           Equipment Options for Medium to High-Speed Packet

                  Compiled by Barry McLarnon, VE3JF

                       Last update: 2 July 1993


The purpose of the following is to summarize the hardware options
available for constructing medium- to high-speed packet links.  Thus far,
only 9.6, 19.2, and 56 kbps are covered.  This material is intended to be
a useful reference, but I make no claims as to its accuracy or
completeness.  Many details concerning model numbers and prices are
missing, and I have very little information concerning equipment sources
outside North America.  If you have corrections, or suggestions on
additional information to include in this survey, please send them to
[e-mail] (or ve3jf@ve3jf.#eon.on.can.noam).

This material is released to the public domain.  You can do what you want
with it - all I ask is that you retain this notice and attribution if you
reprint it in whole or in part.

Note: unless otherwise noted, prices given are in $US.


Equipment for 9600 bps
~~~~~~~~~~~~~~~~~~~~~~

      9600 bps Modems
      ~~~~~~~~~~~~~~~
The K9NG modem was available for a number of years as a kit from TAPR.  It
set the "standard" for 9600 bps packet operation, but it has now been
replaced by the G3RUH and new TAPR designs.  Among the improvements
provided by the newer designs is full-duplex capability. Even when
full-duplex is not needed on the air, this is a great convenience for
doing loopback testing of the modem.  If you still have a K9NG modem lying
around, though, don't hesitate to try it!

The G3RUH modem is available from several sources:

PacComm MC-NB96 internal modem card ($109) - fits on disconnect header of
most TNCs.

PacComm EM-NB96 external modem ($175) - standalone version of above.

Kantronics DE9600 modem card, similar to the PacComm MC-NB96.

MFJ MFJ-9600 9600 bps modem card ($110), similar to the others.

The new 9600 bps TAPR modem kit ($70).  The new design has all of the
features of the G3RUH, plus a few enhancements.  It is attractive for
repeater use, since it includes provision on the board for bit
regeneration/FIFO buffering ($10 extra for the parts).  The first rev of
the board in 1992 had a few problems, and some mods were needed for best
performance.  A new rev which incorporates the fixes became available in
early 1993.

The G3RUH and TAPR modems can plug directly into a TNC modem disconnect
header as a daughterboard, or be connected externally via a ribbon cable.

DRSI DPK-9600 ($250).  This is a G3RUH-compatible modem and TNC-2 clone
(10 MHz clock) housed in one box.


      Data Interfaces for 9600 bps
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For 9600 bps, the usual interface is a TNC.  If you don't already have a
TNC, it's worth considering a PC bus interface card like the PI or the
PackeTwin.  They are a better investment since they will not become
obsolete if you upgrade to higher speeds than 9600.  In fact, many people
have reported results with TNCs that were much less than theoretical
maximums, even at 9600 bps.  The faster the TNC clock rate the better:
4.9MHz should be considered an absolute minimum.

Ottawa PI board ($120 US, $140 CDN).  It provides a DMA port which handles
56 kbps with ease, even with a 4.77 MHz XT-class machine.  All you need to
add is the cable to the modem.  The main limitation of the board is that
it does not support full-duplex operation, but full-duplex operation is
rare (especially amongst end users).  The PI also supports a low-speed
port (you provide the modem and radio).  The board can be used with any
version of KA9Q NOS.

Gracilis TWIN-1E PackeTwin card ($225).  Like the PI, it provides a DMA
port for the 56 kbps modem and an interrupt-driven port for lower-speed
modems. The DMA port supports full-duplex operation.  The Kantronics 9600
bps modem can be piggybacked on the card.

DRSI PCPA Type 1296 ($290).  An interrupt-driven PC-plugin card with
onboard 9600 bps and 1200 bps modems.


      Radios for 9600 bps
      ~~~~~~~~~~~~~~~~~~~

A standard NBFM radio is typically used.  To interface to the modem, the
radio must have a direct FSK modulator, discriminator output, an IF with
sufficient bandwidth and reasonable phase characteristics, and fast t/r
switching.  Some radios are usable with just a few modifications to bring
out the required signals, others may need more extensive mods such as
adding a varactor FM modulator, and still others are almost completely
unusable due to their IF characteristics or slow t/r switching.  There are
a few radios designed specifically for digital service which require no
mods:

2m:

DRSI offers a "matched set" ($550)  consisting of their DPK-9600 TNC/modem
and a modified Alinco DR-1200T (20W, synthesized).

70cm:

Tekk data radio ($190), 2W output, one channel, crystal controlled
(430-450 MHz).  Available from Gracilis and other sources.  Gracilis has a
package (TWIN-96E) consisting of the PackeTwin card, 9600 bps modem, and
Tekk radio which lists at $520.

PacComm has two packages which contain the Tekk:

PacComm DT-NB96 ($369): Tekk radio and 9600 bps modem housed in one box.

PacComm IPR-NB96 ($499): Tekk radio, modem, and Tiny-2 MK-2 TNC housed in
one box.

Kantronics D4-10 ($359), 10W output, two channel, crystal controlled
(430-450 MHz).  Can go to at least 19.2 kbps.

A large number of amateur VHF and UHF transceivers have been successfully
used for 9600 bps work.  Many commercial FM radios are also suitable;
ironically, the IF filters in these radios are typically 'better'
(narrower bandwidth, steeper skirts) than in amateur-grade equipment,
which leads to inferior performance at 9600 bps (on the other hand, they
also tend to have superior intermod immunity compared to amateur rigs).
The IF stages of most receivers can be broadbanded successfully, but the
degree of difficulty and expense involved varies considerably.

A good source of information on radio interfacing and other topics related
to 9600 bps operation is the "9600 Baud Packet Handbook" by Mike Curtis,
WD6EHR.  Hard copies are distributed with the TAPR modem, and it can also
be found in electronic form on some BBS's.


      Summary: 9600 bps
      ~~~~~~~~~~~~~~~~~
The cost of getting something working at 9600 bps is highly variable.  If
you already had a TNC and a suitable radio plus antenna, it could be as
little as $70 or so (TAPR modem).  On the other hand, you can get a "plug
'n play" package from Gracilis, consisting of a PackeTwin interface card,
DE9600 modem (piggybacks on the PackeTwin), and Tekk radio, for about $500
- just add an antenna.  You should seriously question spending this kind
of money to get 9600 bps, when you could put together a 56 kbps setup for
not much more money (but, admittedly, considerably more effort!).


Equipment for 19.2 kbps
~~~~~~~~~~~~~~~~~~~~~~~

Until recently, operation at 19.2 kbps had not received much attention.  A
major reason for this is that binary FSK at 19.2 kbps cannot be
accommodated by the IF stages of NBFM receivers, nor is it compatible with
the 20 or 25 kHz channel spacing used for FM in the amateur VHF/UHF bands.
On the other hand, it makes relatively poor use of the 100 kHz channels
typically allocated for 'wideband' digital modes.  However, interest in
19.2 kbps operation has been spurred by the appearance of the Kantronics
D4-10 radio.  Since it contains a varactor modulator, plus a data slicer
following the discriminator, it can be operated in 'raw FSK' mode at 19.2
kbps without additional modem hardware.  All that is needed in addition to
the radio is the computer interface.  A 'souped-up' TNC might work fairly
well, but one of the PC DMA interface boards (or maybe a DataEngine) would
be better.  Running 'modemless' FSK entails some loss of performance, most
notably from the lack of data scrambling, which results in more jitter in
the recovered clock signal and thus higher bit error rates.

Kantronics also offers a 19.2 kbps modem, similar to the DE9600.  The
performance difference between the 'barebones' D4-10 radios and that which
you could realize with the more sophisticated modem has not, to my
knowledge, been quantified.  The GRAPES modem (see below) could also be
run at 19.2 kbps, but it would not be compatible with the Kantronics
equipment (and why would you want to throttle back a modem that can do 56
kbps and more, to only 19.2?).

Some experiences with using the D4-10's at 19.2 kbps, using Ottawa PI
cards and DataEngines as interfaces, appear in an article by John
Ackermann AG9V in the 11th ARRL Computer Networking Conference
Proceedings.


Equipment for 56 kbps
~~~~~~~~~~~~~~~~~~~~~

      56 kbps Modem
      ~~~~~~~~~~~~~
GRAPES (WA4DSY) modem, $250 in kit form.  You also need to provide a box
for it, plus a few interconnecting cables and connectors.  It requires
+/-5V power (about 0.5A @ +5V, 0.1A @ -5V).  This is an RF modem with
input and output (about 1 mW) in the 28-30 MHz band, designed for use in
the bands above 220 MHz (occupied bandwidth is about 70 kHz at 56 kbps),
using standard receive and transmit converters.  The receive and transmit
portions of the modem are separately crystal-controlled, and it can run
full-duplex.  It is not limited to 56 kbps - with suitable modifications,
it can be made to work at 128 kbps or more.


      Data Interface for 56 kbps
      ~~~~~~~~~~~~~~~~~~~~~~~~~~
Ottawa PI card ($120)
Gracilis PackeTwin card ($225)

Both of these cards (see descriptions above) will handle 56 kbps with
ease.

Kantronics Data Engine (need price info).  This is essentially a
higher-speed TNC with two HDLC ports that can reportedly run at 56 kbps,
and an RS-232 port that can run at up to 19.2 kbps.  The standard firmware
is G8BPQ, but there is now also a port of JNOS (JNOS40) by WG7J available.
The DE appears to be more useful as a small standalone packet switch then
as an interface for end users.

Gracilis PackeTen (~$1500?).  This is a full-blown packet switch that runs
a custom version of KA9Q NOS.  It is available in both standalone and PC
bus versions.  If you need more than two high-speed ports (more than one,
if you need full-duplex), then this is really the only choice.


      RF Equipment for 56 kbps
      ~~~~~~~~~~~~~~~~~~~~~~~~
The RF equipment required depends on whether the links are half- or
full-duplex.  There are three basic configurations in use:

(1) Half-duplex point-to-point links

An example is the Georgia backbone network.  The usual RF equipment is a
Microwave Modules (220, 430 MHz) or Sinclabs (220 MHz) transverter.

(2) Full-duplex point-to-point links

Full duplex operation is significantly more complicated, but it is also
highly desirable if you want to maximize the throughput of a backbone
link.  The GRAPES modem is inherently full-duplex, so it is only necessary
to provide separate RF up- and down-converters.  The two channels may be
in-band or cross-band, using either separate antennas or duplexers.  The
only full-duplex point-to-point link I'm aware of is in Chicago - it uses
PackeTen switches and operates in-band in the 70 cm band.

(3) Multiple-access networks with full-duplex repeater

In this case, an in-band or cross-band 56 kbps repeater provides hidden
transmitter-free access to a channel (or rather, a pair of channels) by
multiple 56 kbps stations.  This might just be a LAN for the power users,
but it also is an attractive means of linking a number of network nodes
together, with less complexity than multiple point-to-point links (see the
10th ARRL Computer Networking Conference proceedings for more details). As
in the preceding case, separate receive and transmit converters are used,
usually with separate antennas (in principle, a transverter with "split"
frequency operation could be used, but such things are hard to come by).
The stations in this network do not require full-duplex computer
interfaces, but since the RF portions have full-duplex capability, it
allows smaller txdelays to be used than in the half-duplex case.  It also
allows users to observe the quality of their signals coming back from the
repeater.

The first 56 kbps full-duplex repeater went on the air in Ottawa in
January 1990.  The repeater is cross-band (220.55 MHz in, 433.55 MHz out),
so users must up-convert the modem's 28-30 MHz IF output to 220 MHz, and
down-convert 432 MHz to the 28-30 MHz IF input.


      220 MHz
      ~~~~~~~
      Transverters and up-converters:

Sinclabs ST220-28 transverter ($329 CDN), 15W output.  Sinclabs has
recently withdrawn from this business, but transverters may still be
available from Bob Morton, VE3BFM (Maple Leaf Communications).

Microwave Modules MMT220/28S transverter, 10W output.  Not readily
available new, but watch for used ones on the market.

SSB Electronic TV 28-220/01 transverter ($380), 100 mW output.  These units
have no T/R switching, so that would have to be added externally for
single-channel half-duplex operation.  On the other hand, there are
separate local oscillators provided for the receive and transmit
converters, so this looks like a good choice for in-band full-duplex or
half-duplex split operation.

Hamtronics XV4 transmit converter (kit, $79), 0.5 - 1W output.  The
cheapest alternative, and the power level is adequate if you aren't too
far from the repeater and have a reasonable transmitting antenna.  But you
do need to find someone with a spectrum analyzer to get it tuned up
properly, and some people have had problems taming this unit.


      Down-converters:

Microwave Modules MMc220 (price/availability unknown), 2.8 dB NF.

Advanced Receiver Research (model no., other details unknown).  This unit
is in the $100 range and of high quality, but it really needs a front-end
preamp.  We use one of these converters on the Ottawa 56kb repeater, along
with an ARR preamp.  ARR may be no longer producing the converters.


      Antennas:

You might get by with omni antennas, but multipath can cause poor
performance even when signal levels are high.  Small yagis provide more
margin and help discriminate against multipath.  A typical example is the
Cushcraft A220-7 7-element yagi (about $50).


      430 MHz
      ~~~~~~~
      Transverters and up-converters:

Down East Microwave DEM432 no-tune transverter, 50-100mW output. This is a
3-board set, available in several forms, and there is an optional power
amplifier that provides 15W output.  The local oscillator board normally
has a single oscillator for standard half-duplex operation, but a second
oscillator can be added on the board for half-duplex split or full-duplex
operation.  Some options and prices:

      DEM432B assembled and tested unit, including case, $275
      DEM432B DUAL as above, but set up for dual frequencies, $300
      DEM432K basic kit (no case or connectors), $155
      Second LO kit, $8
      432PA 15W PA, assembled and tested, $180
      432PACK 15W PA complete kit, $135
      432PAK 15W PA basic kit (no case, connectors or heat sink), $75
      Enclosure to house both DEM432K and 432PA, $25
      DEM432-15S complete 15W dual-frequency transverter, $395

Microwave Modules MMT432/28S transverter, 10W output.  Not readily
available new, but quite a few used ones on the market.

SSB Electronic TV 28-432 transverter ($310), 100mW output.  These units
have no T/R switching, so that would have to be added externally for
single-channel half-duplex operation.  On the other hand, there are
separate local oscillators provided for the receive and transmit
converters, so this looks like a good choice for in-band full-duplex or
half-duplex split operation.

Hamtronics XV4 transmit converter (kit, $79), 0.5 - 1W output.  The 432
Mhz version of the unit described above.


      Down-converters:

Hamtronics ($49/$69/$99 for basic kit/kit with box/wired & tested).
Quality of this unit is uncertain.

Microwave Modules MMc435.2 ($115). Current availability unknown.

SSB Electronic K7001-10 ($180). High quality, with a price to match.

There are other sources for units in the $100-$150 range, such as Lunar.


      1.2 GHz
      ~~~~~~~
Equipment for operation of the GRAPES modem at 1.2 GHz and the other bands
above 450 MHz is a problem, due to the scarcity of converters which have
input/output at 28 MHz, not to mention reasonable power output.

      Transverters and up-converters:

SHF-1240(K) "No-tune" transverter board ($149 kit, $189 assembled, from
Down East Microwave): 144 MHz IF (10 mW drive required), 10 mW output.
Also required is the separate SHF-LO local oscillator board ($50 kit, less
crystal; $85 assembled).  A complete transverter (transverter board, LO
board, IF PIN diode switch, packaged in a metal box) is available for
$265.  Note that no RF switching is included, so if you wanted to run
half-duplex, a suitable RF T/R switch or a circulator would be needed.  NF
of the down-converter is in the 4-5 dB range.  Due to the 144 MHz IF, a
separate 28 MHz to 144 MHz conversion stage would be needed.

SSB Electronic USM-3 transmit converter ($210). 1W out (20 mW in).
Requires external LO source (10 mW).  Although normally used with 144 MHz
IF, it reportedly can be tuned for 28-30 MHz IF input.  Housed in a metal
box with BNC connectors.

      Down-converters:

SSB Electronic UEK-3 receive converter ($200).  2.2 dB NF, 20 dB
conversion gain.  The nominal LO frequency is 1152 MHz, for conversion of
the 1296-1298 range to 144-146 MHz.  An LO output port is provided for
driving the USM-3 transmit converter.  Housed in a metal box with BNC
connectors.


      Power amplifiers:

Pauldon (kit, $165): 18W out for 1W in.

Down East Microwave 2318PAM ($205): 18W out for 1W in.  Also available in
kit form.

SSB Electronic PA 2310 ($250): 10W out for 0.5W in (a 20W out version is
$300).


      Antennas:

Although loop yagis are commonly used at 1.2 GHz ($89 kit, $109 assembled
for the 45-element loop yagi from Down East Microwave), a better choice
for linking would probably be the Tonna 23-element yagi (about $70).


      Other Considerations (applies to all bands):

The receive converters have very broad front ends, and some additional
bandpass filtering will often be needed.  A single cavity (or helical
resonator frontend filter, in the case of separate receive converters)
should do the trick in most cases.  There is also a design available for a
homebrew 28-30 MHz bandpass filter for the modem front end.  This might
eliminate the need for a front-end filter, but it depends on your
receiving environment.


      56 kbps Summary
      ~~~~~~~~~~~~~~~
The cost of a 56 kbps station is a bit hard to pin down, given all the
variables.  As an example, we'll consider a station for the Ottawa 56kb
LAN.  The modem kit and a PI board will set you back about $370.  The
rest depends on the choice of rf stuff.  The total will vary from about
$500 to $800.  The "low road" is using the Hamtronics kits and scrounging
up things such as boxes for them and the modem, homebrewing the antennas,
etc.  The "high road" is buying higher-quality assembled and tested gear,
such as the Sinclabs transverter and the MM receive converter.  If you can
find some good used gear, the total should be closer to $650.  Getting on
56 kbps is certainly a more challenging project than plug 'n play 9600,
but the rewards are greater too.


Sources
~~~~~~~

Down East Microwave
RR 1, Box 2310
Troy, ME 04987
207-948-3741  Fax: [phone]

DRSI (Digtal Radio Systems Inc)
2065 Range Road
Clearwater, FL 34625
813-461-0204  Fax: [phone]

Gracilis Inc
623 Palace Street
Aurora, IL
708-801-8800  Fax: [phone]
Email: [e-mail]

GRAPES Inc.
P.O. Box 871
Alpharetta, GA 30239-0871
Email: [e-mail]

Kantronics
1202 E. 23rd Street
Lawrence, KS 66046
913-842-7745  Fax: [phone]  BBS: 913-842-4678

Maple Leaf Communications (Bob Morton, VE3BFM)
R.R. 1
Everett, ON, Canada L0M 1J0
705-435-0689

MFJ Enterprises Inc
PO Box 494
Mississippi State, MS 39762
1-800-647-1800 (order)  1-800-647-8324 (tech info)  Fax: [phone]

Ottawa Amateur Radio Club
Packet Working Group
P.O. Box 8873
Ottawa, ON, Canada K1G 3J2
Email: [e-mail]

PacComm Packet Radio Systems Inc
4413 N. Hesperides Street
Tampa, FL 33614-7618
813-874-2980  Fax: [phone]

SSB Electronic USA
124 Cherrywood Drive
Mountaintop, PA 18707
717-868-5643