April 2013 Archives

Linux Ethernet Card Probe Order

With PCI ethernet cards, probe order is no longer important, so what Linux has gone to is reordering the user-apparent device from the original device. If you use either of these methods listed on a single ethernet card, the other ethernet cards will change name to ethX_renamed, so it is important to list all ethernet cards in the system at that time.

In the event that a CentOS, RHEL or Oracle Linux system doesn't probe Ethernet cards in the order desired:

a) edit /etc/modprobe.conf and add:

alias netdev-eth0 eth0
alias netdev-eth1 eth1
alias netdev-eth2 eth2
alias netdev-eth3 eth3

Or B) create a file in /etc/modprobe.d/ named "<something>.cfg" containing:

alias netdev-eth0 eth0
alias netdev-eth1 eth1
alias netdev-eth2 eth2
alias netdev-eth3 eth3

Reorder the Ethernet cards as required (netdev-ethX is the actual Ethernet card, ethX is the system named device). Check /etc/sysconfig/network-scripts/ifcfg-eth?.cfg for mentions of hardware addresses.

Set ONBOOT=no for Ethernet cards not used on boot or deactivated.
HWADDR may be commented out, but should be set to the correct address for the Ethernet card.


Smith Charts

Yea, though I walk through the valley of impedance mismatch, I will fear no VSWR: for thy Smith Chart are with me; thy Xc+Xl and thy 0+j, they comfort me.

Current Mirrors






APRS Resources

AGWPE: soundcard packet, AND a TNC multiplexer. You can chain multiple TNCs together running XKISS/G8BPQ KISS over serial and make them available to AGWPE aware programs such as YAAC, etc:


http://www.qsl.net/lu7did/ (turn on Javascript for menu)
LU7DID has written Digiplex, which:

Digiplex is a multi-purpose routing engine aimed to work with the AGW Packet Engine by SV2AGW.

Some of it's features are:

  • A cross-band AX.25 L2 Smart Digipeater (SMART).
  • A NETROM router (ROUTE).
  • An APRS enabled digipeater (APRS).
  • A high performance router with hop-to-hop ack (DIGIPLEX).

It's intended to interoperate with other network infrastructure components such as NETROM nodes and digipeaters present on your LAN but based on other platforms.

Also it features other functions such as Telnet remote access, a build-in Web server, the capability to define "managed applications" to be accessed thru it and more...

The program is in the process to be developed with upgrades being continually released as part of the beta process.

You could also see the documentation directly, or could also get the most updated version of Digiplex here.

YAAC, Yet Another APRS Client

Supports serial, KISS, AGWPE, GPS (NMEA-0183), and APRS-IS TCP/IP connections
Can function as a view/messaging terminal, uses OpenStreetMaps (http://www.openstreetmap.org/) for mapping support; can also act as an IGate and/or Digipeater.

Like Shuttle Radar Telemetry Mission (SRTM), it's a good idea to set aside some time and disk space to download everything and then copy over what you need or want. YAAC takes a while to import the maps, and there are several gigabytes of maps available at OpenStreetMaps.

Tracker3 (previously OpenTracker3/OT3m):

Per http://wiki.argentdata.com/index.php?title=Tracker3:
It is based on the Freescale MCF51JM128 microcontroller, with a 32-bit ColdFire CPU core running at 48 MHz.

The Tracker3 supports talking directly to the Garmin nuvi 350 using the Garmin Data Cable / FMI from Argent Data Systems; it doesn't require a GTRANS cable to do so. However, it's best to get/build the dual serial cable to take advantage of the capabilities of the Tracker3; then the FMI cable can be attached to the GPS and the remaining serial port used for KISS interfacing to a PC. The Tracker3 can operate as a digipeater concurrent to most other tasks. However, remember that at some point you will run out of MHz to spare if you turn everything on.

Using the Tracker3, it is possible to build a combined Digipeater and IGate. If the PC should fail, the Digipeater (Tracker3) will continue to run without it. This also lowers the overhead for the PC, as it does not have to monitor and repeat every single packet coming in the serial port.

Motorola Systems 9000 Siren Transistors

HLN1184 / HLN1185

HLN1184 uses a 949.2 bps data stream to talk to the radio; the HLN1185 uses a 9600 bps data stream. The HLN1185 uses a differential communications scheme similar to RS-422 but closer to RS-485. The difference is an added differentially signaled "BUSY" line, which is used for arbitration between devices on the bus; the bus (Systems 9000) is used half-duplex, so a sending unit can sense a collision and resend. Kinda like ethernet implemented over 9600 bps serial....

HLN1185: 4.9152 MHz CPU clock 9600 bps; bus+, bus-, bus busy, CSMA/CD
HLN1184: 3.8888 MHz CPU clock 949.2 bps; bus+, bus -, CSMA/CD

NPN: 2N5302 / Motorola 9698 / 48-869698 / 48-00869698 / 4800869698

PNP: 2N4399 / Motorola 8243 / 48-80182D43 / possibly 4880182D43

If you're looking for this information, you're welcome.

If you're just wondering, they are:

Max Vce: 60V
Max Ic: 30A
Max Ib: 7.5A
Typical DC gain: 15
Small signal gain: 40


Datasheets from some archive site; Syntor X9000 Siren/PA Manual from Repeater-Builder.

Local copies:
Motorola 2N4399.pdf
Motorola 2N5302.pdf

If you want more information about Motorola Systems 9000, search Motorola's patent portfolio at Google Patents.

High Altitude Balloon Resources

Here's a list of high-altitude ballooning resources for hams and others:


Bill Brown, WB8ELK

Amateur Radio High Altitude Ballooning
ARHAB, a hub site http://arhab.org/

Beyond62 -- recently sent a GoPro Camera up

N1VG sent up a balloon and documented it:


http://diydrones.com/forum/topics/gps-module-for-high-altitude?xg_source=activity GPS and other caveats mentioned in the comments.

GPS, or crossing the 60kft limit:

http://www.byonics.com/tinytrak/gps.php GPSs for sale at Byonics
https://www.argentdata.com/catalog/index.php?cPath=23 GPSs for sale at Argent Data Systems


The WhereAVR

Arduino TNC:

TinyTrak3 (TT3):
A small PIC device for taking GPS data and turning it into packets and audio that connects to an existing radio.

TinyTrak4 (TT4):
An updated version of the above with more features, and features yet to be added.

A single device that contains the transmitter and tracker portion; just add GPS.

A similar tracker to the TinyTrak3.

A similar tracker to the TinyTrak4; with a GTRANS cable can communicate with the GPS, but with certain firmware just the data cable (Mini-B) is needed to communicate with a Garmin nuvi 350.

The Trackr3 line is capable of a lot, as is the TT4. However, the nuvi 350 is not recommended for high-altitude work. The nuvi 350, OT3, and data cable make an excellent mobile tracking station, however. The nuvi 350 must be powered through a cradle. The cradle has a mini-USB connector on the back of it which must be attached to power; the data cable connects to a USB port on the side of the GPS.

Cheap Chinese Handheld Radios:


There are other thins to think about, such as insulation, RADAR reflectivity, battery temperature, etc.

As temperature goes down, battery capacity drops as well. Therefore more batteries may be needed, or the batteries may require additional insulation. Several sheets of thick polystyrene may be formed into pouches and placed over the battery pack. Alternatively, one could wrap the battery pack in several Ziploc-style freezer bags. Attempting to heat the battery pack would be complex, and require a method of applying the heat while monitoring the temperature to prevent cooking the batteries. Also, one must remove all of the insulation from the batteries during charging or the heat will damage the batteries.

For weight reasons, Lithium Polymer (LiPo or LiPoly) batteries are recommended.

For ruggedization and thermal extremes, soldering all connections practical is recommended as well.

All About NiMH Batteries


Everything you ever wanted to know about NiMH batteries but didn't even know what questions to ask.

First, there's the Wikipedia page on NiMH batteries:


Then there's the 2011 Panasonic Handbook on NiMH battery charging, use, and discharging. This is an excellent resource I highly recommend you read if you have an understanding of electronics and own anything with NiMH batteries in it:

http://industrial.panasonic.com/eu/i/21291/Handbook2011/Handbook2011.pdf [Local copy]

Energizer has some guidance as well, but I feel like the Panasonic Handbook is a better, more informative document.


Microchip has a reference design for a NiMH charger chip they manufacture:


And Freescale has a design using a microcontroller as well:


Due to self-discharge, the battery naturally loses charge over time. It is recommended that the battery be charged at least once a year to prevent cell voltage from dropping low enough that either electrode switch polarity. 

In short, most manufacturers recommend a terminal voltage of 1.0V to 1.1V, but not to discharge to lower than 1.0V per cell. Panasonic suggests that when more than six cells are in a pack, the lower voltage requirement may be moved down slighly; this results in a terminal voltage of 10.8V for a five-cell pack with a nominal voltage of 12V. Conveniently, they also recommend to stop charging when the voltage per cell is at about 1.4V, which works out to 14V for a 12V pack.

The absolutely critical part of using NiMH batteries is charging. The batteries must be charged with a slow, constant current source; rapid charging requires the use of temperature sensors to prevent damaging the cells. Trickle or float charging is verbotten (forbidden)! A typical controlled charging cycle is sixteen hours long or longer.

Despite the above attractive voltages which might convince a person to use a common automotive charger or a 13.8V float charger, the NiMH battery requires the current, not the voltage to be more carefully monitored.

Because of the above mentioned self-discharging behavior, this may be exploited to cyclically and "lightly" charge the battery. Top-off charging is not recommended. Duracell has provided guidance that a C/300 charging rate may be used to prevent voltage loss due to self-discharge. The author recommends a cyclical method of charging to compensate for self-discharge.

Finally, remember that when combining strings of battery packs, balancing resistors should be used, and if possible, each string should be charged independently of the other strings. This prevents one battery pack from becoming the recipient of excessive charging currents, should a battery fail in the pack. In large packs, the heat involved may cause a fire.

Packaging materials should be resistant to strongly alkaline solutions; nickel and stainless steel are recommended, but not brass or copper.

One should not solder directly to a NiMH battery. Use nickel strips spot-welded to the battery. Spot-welding limits the amount of heat the battery is exposed to in that operation.

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This page is an archive of entries from April 2013 listed from newest to oldest.

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