Texas A&M University W5AC The Texas A&M Amateur Radio Club, College Station, Texas
College Station, Texas, U.S.A. • Brazos County • EM10tp

W5AC - Data Radios 2004

Mike Mertes, KZ5M, has found a supply of data radios that we are converting to 70 cm packet radio use. Below are the latest e-mails on the subject.

Table of Contents:

Background Info

W5AC Meeting Minutes for 2-March-2004
Mike Mertes, KZ5M, discussed his progress in obtaining 
several 440-band UHF data radios for conversion to Ham frequencies and use 
as portable packet stations. These 9600 bps, battery-powered radios would 
be useful to pass traffic in an emergency and would be fun to play with during 
non-emergencies.  Mike found a seller peddling Maxon CP-530s data radios, 
which output 9600 baud on 1 channel at 2 watts on the 400-MHz business 
band and can be recrystalled for use in the 440 ham band. Price and volume 
discussions were still ongoing and will be posted to the W5AC listserv as 
details become available.

11-March-2004 03:05PM
From: KZ5M
Subject: data radio jpeg

I've firmed up the deal on the Maxon data radios. They are in a handy
talkie form factor using a proprietary data connector; however, we are
planning to bend our own enclosures and make the connection using a DB-9
connector. The cost of the unmodified radios are $15 each plus shipping.
The radios we plan to purchase are the smaller of the two radios in the
attachment to this email. The deal is for the Maxon model CP-530.

These radios will have to be modified to be used on 9600 baud and tuned
into the ham band. The seller had plans to do what we are proposing to do,
but wasn't able to generate the support to see it through. So he is
willing to sell us the radios he has collected. Also, he has documented
the modifications necessary to convert the radios for 9600 baud and is
providing a photocopy of the manual.

I believe that we have the interest and the resources available to make
this work.

There will be an additional cost for the TX and RX crystals for these
radios at some point, for they are currently crystalled in the 450-460MHz

Our current plan is to set up a UHF 9600 Baud digipeater using the same
coax, UHF/VHF antenna, and battery backup as the W5AC APRS digi.

Initially this system will provide radio text messaging between our club
members as well as the EOC. Our goal is to ultimately provide a system in
ready reserve for portable emergency text messages. From there, we may
develop additional functionality such as down-loadable weather maps as
well as other things.

There is a lot of potential for a digital radio network, and I would like
to see a healthy discussion going on as we take the first couple of steps.

I'll start collecting money this week from those who wish to be guaranteed
a radio.

If the bandwidth gets to be too much here, we can form up a new list if

73, Mike Mertes /kz5m
Our new radio, at top, in current HT enclosure
Our new radio, at top, in current HT enclosure
16-March-2004 05:18PM
From: KZ5M
Subject: UHF Packet update

I'm sending this to update those of you who following the packet
radio/emergency service thread. As to the discussion on the W5AC 
Monday night 2M net last night, if we start using too much bandwidth on 
this subject, we will move the discussion to a new list. For now, we 
continue to post to the W5AC listserv.

I have contracted to purchase 35 of the Maxon CP-530s handy talky 
radios. The owner is the president of TAPR and will include directions for 
opening them up for 9600 baud (and higher) packet. The radios are similar 
to the DM-530s which are a "full blown" data radio... or referred to as a
telemetry radio. They come with an external mic/speaker connector and 
a place for an internal batter. Our plan is to remove the radios from 
the handy talky case and mount them in to a smaller aluminum box. Kevin 
has expressed an interest in using my sheet metal brake to make the 
boxes. Power out is 2 watts as they are.  This should be enough for what 
we are doing locally. If we need more, this power level is good for 
driving most external amplifiers.

We are still working on options for which TNC will be the cheapest 
and work the best. With our initial plan, we are going to stick with a 
TNC-2. It seems as though TNCs can be found at swap meets in the $20-$40 
price range.  There are 9600 Baud modems (add on boards) for most TNC-2 
clones out there. Information can be found at:
http://www.tapr.org/tapr/html/F9600.html The cost of the 9600 baud 
modem board used to upgrade a TNC-2 is $80 (without a membership discount 
from TAPR.) $72 with a membership.

I checked with Bomar Crystals today and for 20 radios, they will 
charge $10 a crystal. Since each radio will need 2 crystals (one ea. for 
TX and REC) that brings the cost of crystals to $20 for each radio. That 
will bring the total cost for each radio to about $40 by the time we add a 
bit for shipping, a connector, a sheet of aluminum and a few circuit 
parts. The lead time on the crystals will be 3 to 4 weeks once ordered. We
haven't chosen a frequency yet.

I plan to purchase the radios in the next 4 or 5 days.  That would 
give me some time to raise the money and get a firm head count.

Now is the time to let me know how many radios you want to play with.

Mike /kz5m

31-March-2004 12:05PM
From: KZ5M
Subject: Data Radios
Hello Guys,

I've got the data radios on the way, and I'm sorry I haven't posted more
info about this, but I've been very ill this last week. I'm doing well
enough to post a quick update here.

I have PDF files of the schematics, alignment and parts breakdown manuals.
I can forward copies to those that request them. I'll see if we can't post
them to a section of the W5AC website and maybe do some sort of web log on
this project. I'm also collecting money to pay for the radios, crystals,
connectors and sundry parts. The cost is $40 a radio. The plan is to
remove the radios from their handy case and mount them in an aluminum box
 The circuit mods and alignment will also be
done by volunteers from the data radio project group.

I would like to have money in hand by this time next week to order
crystals. We will have plenty of spare radios, so if you would like
several let me know. I'll email you individually if you have made a
request already. If I haven't contacted you directly by this Friday, and
you would like to get in on this, let me know.

73, Mike Mertes /kz5m

5-April-2004 5:05PM
From: KZ5M
Subject: Packet radio update

We are having W5AC business meeting tomorrow night at 7PM in room 352 just
down the hallway from the W5AC radio room. I'm planning to collect money
for the radios and parts to modify them for our use. The cost is $40 for
each radio. James Nabors has offered to buy for one for the club. (thanks
jim) The data radios have arrived and I'll bring some samples to the club.
I'll also bring some other hardware and have a discussion on our progress
and plans.

At the meeting tomorrow night, I suppose we will discuss what to do with
the current failure of the elevation rotor. It was heart breaking to have
the computer system working and the antennas tracking the satellites and
then to have the motor go out. We were so close!

I hope to see everyone at the meeting!

73, Mike Mertes /kz5m

19-May-2004 2:43PM
From: KZ5M
Subject: Re: TNC
Hello Randy,

I was just thinking how great it would have been to have everything set
up and going last week when the flood happened. I suppose that was a
reminder of why we are pursuing this.

We had a club meeting last night with a good turnout. We discussed field
day as well as the data radio project. So I'll bring you up to date, and
then post much of the same info to the listserv later today or tomorrow.

Concerning the Data/Packet project, I've lost momentum on it last month
when I came down with a really nasty respirator infection, and have been
set back about 4 or 5 weeks; while I catch back up on all the things that
have piled up. So right now, I'm trading email with our area coordinator
to get our frequency in order. I've set a goal to have the digipeater up
and running at 1200 baud use to coordinate this years Field Day. The last
week I've been working to repair several TNCs to use for testing, and I
haven't been successful with those yet. The Belton swapfest is this
weekend and several club members are going and will be looking for TNC and
battery powered printers. I plan to attend if possible. Also, HamConn is
coming up in Arlington mid June.

So I'm picking up this week on the Data Radio/Packet project where I left
it 4 or 5 weeks ago. I have 3 things to do with it this week. Not in any
particular order... nail down the frequency...  order the crystals...
write up a overview and post to the website....

At the club meeting we brought up the battery backup for the digipeater
and 146.82 repeater. The request has been sitting on a students desk and
will need to be modified and resubmitted to SPO.

I hope this brings you up to date on things. How did you survive the

Mike  /kz5m

10-June-2004 4:06PM
From: KZ5M
Subject: data radio update
To the guys who are interested in news on the 
Packet UHF Data project, Bomar Crystals has the order. The radios will 
transmit and receive on 446.100 MHz.

So far I've found common TNC-2 compatible modems are the AEA PK-80,
PacComm TNC-200, Tiny-2, Spirit and the MFJ 1270 series. All of these 
have a 1200 baud radio modem and 9600 daughter board modems can be 

There are a couple on ebay at the moment.


On Thu, 10 Jun 2004, Randall Hamm wrote:

> Do we need to get the modem of is this just information?


This is just information for now. We will start out at 1200 baud and get
this going. Our goal is to get up to 9600 baud. We can handle much more 
traffic and information at 9600 baud.


6-August-2004 3:56PM
From: KZ5M
Subject: data radio update

When I saw Chris KD5SYI today, I showed him the work progress on the radio
conversions for the data radio project, and he mentioned that he hadn't
heard anything about it on the list recently, and he wanted to have some
more information on the project. So I thought it would be good to pass
this along to anyone else as well.

The hams who have bought into this project:
Kevin Gluek N5TLT
Richard Zimmer W5DZ
James Nabors KD5HRE
Randall Hamm
Michael Baur KD5NPF
Lance Cotton KJ5O
Doug Dornier KD5USF
Steven McClaran KK5QE
Peter Gogas W1AGG
Karl Williams KC5IXX
Tim Scott N5NMT
Chris Williamson KD5SYI
Mike Mertes KZ5M

The guys that have gotten a battery powered printer that I'm aware of are:
Randall, Dick, Kevin, Lance, Doug, and KZ5M. And I'm not keeping track of
who has a TNC already. I think most the guys who have a portable printer
also have a TNC by now.

We have a total of 30 radios involved in the project. Several guys have
purchased more than they need so we have some backups and hardware
available to provide increase the size of the core group as this develops.
I have purchased a few spares which I'll keep in reserve in the event
there is a demand for more rigs.

N5TLT and I met last night to finish the prototype enclosure and trial fit
a radio and mounting hardware, and it looks nice. So today I placed an
order for enough hardware to do the rest of the radios.

The radios will be housed in a 0.028" thick aluminum enclosure that will
measure 2 3/8" wide by 7/8" thick by 4 1/2" long. We haven't formed a lid
for it yet, but that should be a much simpler job when we get that far.

I purchased a good quality manual and schematics for the radios, which I'm
using to work out the wiring and part relocation. I will also need to test
and repair any of the radios that need repair before we do modifications;
as I can find time.

So far the project has met the budget for the radios, but to finish the
job, I'll be slightly over. I still have a few things to order
for the electronics.  We won't be able to reuse the volume or squelch
controls because of the size, but they can be replaced by trimpots, and we
will have to use a low dropout regulator to get the voltage on the radios
down to about 10.8 volts.

The integrated circuit the radio uses for the IF section has an absolute
maximum rating of 12 Volts which isn't going to work directly from a 12V
SLA (nominally 13.8V.) I'll get together with Dick on that to see what we
can do. Maybe we can mount a low dropout regulator inside the radio if
space and thermal dissipations allow.

73, Mike Mertes /kz5m

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