Josh – Page 9 – Joshua P. Luben

February 1, 2015December 12, 2015

Maxpedition Triptych

One of Maxpeditions new product offerings right at the end of 2014 was the Triptych line of personal organizers. Various re-sellers were preselling them and I waited three months to get one. Just checking Amzon, there is only one listed: Triptych Organizer, Black – PT1181B

This organizer has a handle, two side pockets that are big enough for pens, a phone, and a pocket folder, but nothing larger. I purchased the large model because inside pocket is big enough for a notebook and an iPad Air, or alternately a tablet and a solar panel. I purchased a discounted Poweradd 7W solar panel and it fits nicely with my iPad.

The downside with an organizer like this is that I keep trying to put too much stuff in it. With a notebook and a tablet, there is no place for my keys. I had my keys jangling around on one of the shoulder strap loops on the end, but I hate having my keys jangle.

MSRP is $59.99.

January 11, 2015January 12, 2015

Pcduino Cluster Part 1

I used to do a lot [more] HPC software development when I had access to the Penguin cluster at a previous place of employment. The cluster was a full upright rack full of nodes.

As I get more into node.js (and some other stuff: you can do MPI in python), I decided to build a small cluster for development purposes. After my really good initial experiences with a pcduino3, I decided to use the pcduino3 nano instead of raspberry pi’s. The pcduino3 has a lot more power than the rpi and you can find it for about the same price if you shop sales (checkout LinkSprite).

With the proliferation of cheap gigabit switches and high amperage multi-port USB chargers (like the EZOPower 96 watt 8-Port) you can build a fairly affordable low end cluster that is not very big.

January 3, 2015January 4, 2015

Hiking King Mountain in the Tillamook State Forest

On the tail of end of New Year’s break, my friend James and I decided to hike something in the coastal range. We decided on King Mountain as it a bit longer in length than the nearby Elk Mountain. This hike is five miles round trip with an elevation gain of about 2500 feet. Portland Hiker’s provides excellent documentation and links to maps.

We had excellent weather the Saturday we went hiking (going early in January). There was some mud in a few places and snow patches at the top. With no wind, the temperature was easily ten degrees lower at the top. The trail does not get rugged until the last half of a mile. At some points the trail is mostly loose rocks. Take walking poles and be careful of your balance.

December 27, 2014December 28, 2014

Working SI5351A Breakout Board

After Jason NT7S wrote about the SI5351A clock generator, I purchased several of his Rev B designed prototype boards by Oshpark (Portland local–yeah!). I spent quite a few hours getting these things to work. The SI5351A is a msop footprint. Mounting this chip turned out to be a very tricky exercise. Every time I thought I got all the pins correctly soldered, I would go back and check with a DMM and find one that was not actually conductive.

There are a few other tricks to making the NT7S board work correctly:

Read Jason’s documents. He has written a lot of documentation and everything is there you need to know. You just to need read it thoroughly. I did not and it took hours of troubleshooting to figure out what he already documented.
Pay attention to Jason’s notes about using an ECS crystal. Pins 2 and 4 are connected and will short Vdd to ground.
The SI5351A chips I got from Mouser use the I2C address: 0x6F
Capacitor C3 on the output of the LP2985 is required to get the 3.3 volt output. Omitting it will cause the local supply voltage to be around 4 volts.

If you want a general purpose SI5351 to play with or for simple non RF purposes, the Adafruit breakout board (PN 2045) can be purchased assembled for cheaper than I can buy the parts. The NT7S board is thought out and more agile. It has better mounting holes, configurable I2C pull ups (I really appreciate this), provisions for VCXO and isolation transformers.

I really appreciate the work that Jason has put into characterizing this device. He single handed opened the doors for a lot of people to start using this device and it’s become the talk of QRP-L, EMFRD, and SolderSmoke.

(please excuse my horrible soldering job. I had to cannibalize some SMD parts from an ActionTec router)

December 27, 2014

Git Backup Script

I run a local git repository on the server located at my house. Here is the latest backup script that I use to archive the git files.

#!/usr/bin/python
#
# This script dumps a git repo to flat files and ftp's these
# files to another network device.
#
import os
import datetime
import ftplib
import sys
import traceback


def main():
    if 5 > len(sys.argv):
        print("Usage: gitBackup <host> <user> <pwd> <remote path>")
        return
    
    host = sys.argv[1]
    user = sys.argv[2]
    pwd = sys.argv[3]
    remotePath = sys.argv[4]
    
    #
    # export the svn data to a compressed file
    #
    dToday      = datetime.date.today()
    strFileName = "git_backup_%s" % dToday.isoformat()
    
    strCmd = "git bundle create /tmp/%s master" % strFileName
    os.system( strCmd )
    strCmd = "git bundle create /tmp/%s.all --all" % strFileName
    os.system( strCmd )
    
    
    os.system("tar -cvzf /tmp/%s.tgz /tmp/%s.all /tmp/%s" % (strFileName, strFileName, strFileName))
    
    #
    # send the svn archive to our backup server
    #
    try:
        s = ftplib.FTP(host, user, pwd)
        s.cwd( remotePath ) # "/Josh/backups" )
        strFilePath = "/tmp/%s.tgz" % strFileName 
        f = open( strFilePath, "rb" )
        s.storbinary( "STOR %s.tgz" % strFileName, f )
        f.close()
        s.quit()
    except Exception as e:
        print("FTP error: %s" % str(e))
    
    #
    # cleanup our temp file
    #
    os.system( "rm /tmp/%s" % strFileName )
    os.system( "rm /tmp/%s.all" % strFileName )
    os.system( "rm /tmp/%s.tgz" % strFileName )
     


#
#
#
if "__main__" == __name__:
    try:
        main()
    except:
        traceback.print_exc()
        
#
# EOF

December 25, 2014

KI0BK Low Loss PWRGATE

My parents gifted me a KI0BK PWRGATE. This little unit is compact and cost efficient.

December 25, 2014December 25, 2014

HF Radio Prototype Platform

Now that I have some vacation time, I’ve been working on my radio prototype platform. The long-term purpose is to provide a place to work on the software filtering algorithms. I added an audio stage to prototype using a MAX2726 5th order filter. Using a 68pf external capacitor, I get nice roll off about 1.2khz.

December 25, 2014

More tools for Xmas vacation

I’m super excited to add the miniVNA to my toolbox.

December 22, 2014December 22, 2014

HF Gain of the SMA3107 MMIC RF Amplifier

I found these surface mount rf amplifier’s on Mouser. They have no minimum stated frequency floor but are documented to work up to several (2.8) ghz. They are available for about USD$0.52 in individual quantities. The package is listed as MCPH6. The pins are closer than a SOP23. I was able to get it on an Adafruit SOP23 breakout, but it was very careful work.

I measurement the voltage gain at from 20mhz and down. The gain drops as the frequency drops. I found that SMA3107 is not really linear until about 3.2mhz. Somewhere below that it looks like some oscillation is occurring.

December 22, 2014December 22, 2014

Acrylic under table shelf

Built a very simple acrylic shelf under my GeekDesk to put the USB hub and NUC on. This keeps the wiring on my desk to a minimum. I used the nicer Kreg 1″ pan head screens. If time was not always an issue, I would paint the oak spacers black to match the rest of the desk.