Monday, December 23, 2013

Poor Hams Scalar Analyser (PHSNA)


While working on some HF bandpass filters a few months ago I decided I needed a smaller test Instrument. I came across the PHSNA group on Yahoo groups who were using a cheap $5 AD9850 DDS module from China and an AD8307 Power detector controlled by an Arduino to make a Scalar network Analyser good to 35MHz or so. It sets the output frequency of the DDS, measures the signal with the AD8307 and sends the dBm value and frequency to a PC where the data can be captured and graphed in Excel or similar
Luckily a PCB was available for the DDS carrier board and the RF detector.  Their were two versions of the DDS board. One used the widerband ERA3 amplifier, the other used a discrete 2N5109. All the components were available from Mouser. The PCBs took around 1 hour to build. To provide extra screening the Detector PCB was enclosed in a tinplate box. The following show the two units in the enclosure and the Amplifer/Interface board with the DDS PCB. Yes the PCB has been modified as the onboard filter has incorrect values. The components have been removed and an external filter fitted. The Arduino is mounted under this PCB The unit is powered from 13V supplied  by the DC power connector on the Arduino, ensuring the amplifier stage has full output.








I found a W8DIZ 15m bandpass filter that I had built from the kitsandparts.com kit to try the PHSNA on. First I connected the dds output directly to the detector input and recorded the power 17 to 26MHz. I then put the filter in line and again swept 17-26MHz and recorded the power. Using excel I plotted the difference between the two sets of readings and plotthed the filter characteristic:-



Not bad for $50

Sunday, December 22, 2013

Stratodean Balloon Ascents



While looking for data on the Ublox GPS unit on my Arduino GPS shield I came across the Stratodean website. They use the unit for their helium Balloon ascents from the Forest of Dean. They have some very impressive videos of the ascents which landed in Milton Keynes and South Wales. The whole design and building blog makes very interesting reading

Saturday, December 21, 2013

Amplifier for the Kanga/M0XPD DS shield

It was time to look at an amplifier for the Kanga DDS shield . I found their "Sudden TX Shield" on the web site. This would have worked fine but would have taken a couple of weeks to get to Texas and would have cost 24.95GBP plus 20GBP shipping. A homebrew amplifier was needed. 

According to the M0XPD blog the Sudden shield is based on the G-QRP-Club Sudden Transmitter. The manual is available at http://www.gqrp.com/Sudden_TX_Kit_manual_40m.pdf . The junkbox had some 2N3904, 2N3906 and 2N5109 and I also had some plugin bandpass modules from my G0XAR Ulimate 2 Beacon transmitter. A visit to Radioshack produced some double sided PCB (Note it is not glass fibre PCB,  if you try to cut it with tinsnips it will crack in random directions) to build it deadbug style. The trackes were made with a scalpel and steel ruler.

Initially the amp was tried on 30m with a 2N3904 and a 2N5109. 1mW input produced over a watt of output from the LPF but driving it from the DDS shield gave just 100mW. Looking in the modamp box I found some MSA0385 which would produce 10mw output with 20dB gain. I added this to the PCB and found it had too much gain when driven by the DDS shield so an 7dB attenuator was added to the input. The "gain" preset on the 2N3904 allowed the output to be set from -10dBm to +32dBm which peaks at 0.5A at 13V. The 2N5109 got very warm but W5LUA provided a top hat heatsink from his collection on a recent visit

With the amplifier running 200mW the MEPT has been seen all over the USA when transmitting on the Alexloop



Saturday, December 14, 2013

Kanga/M0XPD DDS shield




While in the UK last time I bought the "Kanga / m0xpd DDS Shield" DDS shield that fits onto an Arduino Uno. It uses one of the $5 chinese AD9850 DDS modules as the RF generator along with an 16x4 LCD with IIC interface and rotary encoder. Using the Occams beacon software of M0XPD I turned it into a trimode QRSS/CW/WSPR beacon as described at http://m0xpd.blogspot.co.uk/2013/10/occams-beacon.html. It took around 30 minutes to build the shield and I stacked it on a genuine Arduino Uno. I only had a 20x4LCD so the sketch needed modifying to accomodate its layout. It did  not have an IIC interface but they were available off ebay for $6

The M0XPD sketch needs modifying to accomodate the WW2R callsign. As suggested in the sketch I used the 'WSPRcode.exe' programme available from G4JNT web site to generate the WSPR code. Unfortunately the output format cannot be "cut and pasted" into the sketch and after numerous failed transposition attempts I looked for an alternate method. Luckily I remembered the W3PM "WSPRMSG.EXE" programme at http://www.knology.net/~gmarcus/ which allows cut and pasting the output directly into the sketch

An issue with the software is that the timing is derived by counting the processor clock which runs at 20MHz. Using the default timing count value (60000) WSPR decodes stopped after 40 minutes as the WSPR transmission start time had drifted out of acceptable range. By measuring the time delta over 10 cycles,  (monitoring the output on the ANAN-10 and Argo software), the correction factor was calculated and used (60127) This stopped the time drift issue for the time being.

As the Beacon has no idea of clock time the Arduino is reset at the start of an even minute and starts its internal clock from there. This is a little tricky but after practice i could get the start within 0.5S.

Obviously these issues could be eliminated by using a GPS receiver to get accurate timing. M0XPD has been looking into this,  but while waiting for the result I have started looking at the code W3PM used in his Arduino beacon shield.

The final issue was the frequency of the DDS clock oscillator. This is nominally 125MHz which is the parameter used by the sketch. However my WSPR transmissions were initially outside the range of the WSPR decoding programme.  The value had to be adjusted to get the output frequency correct as measured on a GPS locked counter. Initiially I also had drift issues (df=2 on WSPR) but by putting a tent (a towel!) over the dds board to stabilise the temperature the issue went away

Note the shield only produces -12dBm so it would be hard to spot if transmitting into a non optimum antenna, The AD9850 DDS produces output all the time, unlike the AD9851 the AD9850 has no provision to mute the RF output. A keyed amplifier will need to be the next project

Thursday, December 12, 2013

Nexus 7 2013 Upgrade




I have had a Nexus 7 (2012) for around a year and use it much more than my IPAD. When I saw that there was to be an updated version with front and rear cameras and an audio jack that supports headphone and microphone (like the IPAD does) I thought of getting one. The list price was $229 for the 16GB WIFI version was offputting, so I decided to wait until the "Black Friday" (the day after thanksgiving) Sales period. In actuality I did not have to wait that long as I encountered a good deal the previous Wednesday.and ended up buying one for $189.99 shipped.

It took 2 weeks to be delivered due to the post sales bottleneck!  When I opened the package, the first thing to be noticed was that it was thinner and lighter than the previous version. When powered up the display was also crisper being 1920 x 1200 resolution compared to the previous1280 x 800. 

As advertised the 4 pole audio jack worked with my Ipad headphones on Skype. No more shouting at the tablet. This is promising improvement when using FLdigi app where previously you had to hold the tablet near the radio speaker which was prone to background noise.

There is no HDMI output on the Nexus 7 2012. However reading the online reviews of the 2013 model it has a slimport jack on the bottom (looks like a microusb connector to me) and an HDMI adaptor can be bought. Searching on ebay I found one for $18. I did make sure i got one where you can charge the Tablet with a monitor hooked up. This works well and allows videos to be played on the living room large LCD TV.




The only wish list item I would like is a microsd slot to extend the storage, however I can use it with the RAVPOWER WIFI disk as previously mentioned which ups the storage to 500MB. 


Sunday, December 1, 2013

Building a USB Powermeter


Although I can control the ANAN-10 remotely over the internet I cannot monitor the output power via the computer.  PowerSDR has a "forward power indication" but it isnt actually measuring the power at the ANAN-10 PA output! I could buy a minicircuits PWR-4GS USB power meter at $900 but I needed a cheaper option.

Searching the internet I came across a design A very simple to build, menu driven RF Power Meter, based on the AD8307 log amp by Loftur TF3LJ. It used a Teensy++  micro available at www.pjrc.com and a 16x2 LCD display. I already had a Teensy++ board and a 16x2 backlit LCD. All I needed was the AD8307. I while ago I had tried to build the W7IEQ SWR/Power meter published in QST Jan 2011 which used two AD8307, a PIC and an LCD. It was a disaster and I never got it working mainly due to software bugs which never got fixed in the code especially the version hosted on the ARRL website. I threw away the main PCB and box but kept the 30dB directional QRO coupler and the 4 PCB with AD8307 and BNC input connectors.


Modified AD8307 RF detector PCB
It did not take many minutes with a Scalpel to modify one detector PCB to match the TF3LJ detector circuit
The Teensy was mounted on a stripboard with a plug and socket , the whole unit was mounted in a 5x3x2" box.
Teensy++ Processor
The whole device is powered through the mini USB connector on the Teensy++. Programming was also done through this connector using the Arduino IDE v1.05 and the PJRC Teensy plugin. (note the plugin  wont even install with later Arduino IDE versions eg V1.5.2. Calibration was easy and requires 2 known signals 30 or 40dB apart. I used -12dBm and -42dBm available from my LPRO101 10MHz Rubidium.
Innards of completed meter

The meter also enumerates as a serial port on a computer and can be made to continually output a power value in Watts at 4800Baud using the $pcont command:-

0.000000000328
0.000000000311
0.000000000287
0.000000000272

more detailed information can be obtained on a 1 shot basis using the $ppoll command:-

Power (inst, pep, avg):
 286pW, 1.84nW, 1.04nW

This allows remote monitoring.
Total cost (with new parts) would be around $75

The meter measures from ~-70dBm to +17dBm thro 440MHz. It has provision for 3 calibrations (eg HF, VHF, UHF) to accomodate calibration issues over that range  I also found the -40dB tap flat through 500MHz shown on the TF3LJ site but originally published in the W7ZOI power meter addendum article. With this I can measure up to 200W and I can have the power meter read directly as I can enter the 40dB offset

I thought of building 2 units one for forward power one for reverse power. Then I spotted that Loftur now has a Power and SWR Meter with bargraphs, using 2x AD8307 design on his website using a 20x4LCD and a Teensy++. I can see one getting built, especially as I already have two AD8307 PCB!





Thursday, November 28, 2013

Portable display for the Beaglebone Spectrum Analyser


Finally got round to trying to put the 7" LCD display in a case. Went to the local Radioshack and found they had  Project Enclosures (8x6x3") as part number 270-1809 for $9. The display was mounted in the base of the unit after cutting out a hole just big enough for the display area. The interface board was mounted on the bottom wall with the connectors showing through a hole cut in the box "lid". The switch PCB was mounted on the right side wall. Currently the switches are pressed with a paperclip until i can find some real switch caps. Took about an hour with a drill and file without a vice to hold it in on the apartment balcony! Good exercise after the Thanksgiving Turkey!






The beaglebone black spectrum analyser is now portable!

AlexLoop Walkham Arrives

After 5 months of inactivity I decided I needed an HF antenna that fitted on the apartment Balcony which I could use on Transmit. I had looked at the Buddipole but it was too large. I saw the Alexloop a while ago which covers 7 to 30MHz, but shipping from Brazil was prohibitive. Recently it was reviewed in QST from which I learnt there were 2 USA distributers. Problem solved. I ordered the Alexloop Walkham from Gigaparts (as shipping was free) on Oct 16. Enquiring Nov1 I was told that they were on backorder but I should get it by Thanksgiving. Nov 11 I went chasing the order and was told it was delivered by UPS on Nov 12. After some detective work I discovered that it was in the Apartment complex management office, locked away securely, so I recovered it.

It came well packed in a box inside which is a laptop sized fabric case with all the parts held firmly in place.

The central mast comes in 3 sections which push together. The loop is plugged into the two connectors. The coax and coupling loop are integrated into the mast. It assembled in under 2 minutes. Alex suggest standing and holding the loop, allowing ease of retuning and operating with the other hand. Didnt sound much fun to me! A visit to the local hardware store produced a length of half inch of plastic pipe which was cable tied to the balcony railings and supported the antenna:-


I had a listen during CQWW CW and heard lots of stations including 10m Europeans.  Changing bands is not easy, as i have to go out on the balcony and tweak the tuning capacitor while watching the swr meter 10m away. The knob is not calibrated ! The rig is fed by 10m of RG174 thin coax as it is the only cable that will fit under the balcony door jamb

Today I left it transmitting on 30m DFCW QRSS. Even at 3mW it was visible in Florida at the W4HBK grabber



My ww2r signal is at the bottom

Sunday, November 24, 2013

President John F. Kennedy Memorial Concert

The past week Dallas has been remembering the 50th Anniversary of the assasination of JF Kennedy. On Nov 22 the City of Dallas declared a holiday and there was to be a downtown Memorial. This was severely disrupted by Heavy rain and high winds, cancelling the outdoor concert

While travelling back from work Friday night I came across a replay of a piece by Walter Cronkite assembled ten years previously for the 40th anniversary on KERA 90.1MHz. Of particular interest was listening to the Air to ground Communications on HF SSB between Air Force One, the Federal Council (inbound from Hawai and Washington) . Previous experience listening to 20m SSB did help. I did find a copy of the programme, and transcription at http://keranews.org/post/walter-cronkite-assassination-john-f-kennedy

As part of the Memorial Activities DSO held three concerts  entitled "President John F. Kennedy Memorial Concert"  for which we managed to get tickets for the Nov 24 Performance. The concert opened with a commissioned work by CONRAD TAO The World Is Very Different Now. The piece was a bit nondescript, but scenes from the period were projected on a huge screen over the orchestra which were very interesting. Next was SIBELIUS Violin Concerto with the Soloist Joshua Bell who was brilliant and highlight of the concert. After the Intermission MILHAUD Murder of a Great Chief of State was quickly followed by BEETHOVEN Symphony No. 3, Eroica which was well conducted at a faster than normal by Jaap Van Zweeden

Monday, November 11, 2013

ANAN-10 Signal Overload

 While looking at signals on 474.2kHz using the ANAN-10 and the Clifton Labs Active antenna I noted that the A/D overload warning in PowerSDR would come on often. I hooked up the ANAN-10 and used the KISS wideband view to see where the big signal was. The answer was "in the medium wave broadcast band. The loudest station peaked -27dBm into the transceiver in the daytime. Looking on the Spectrum Analyser one can see the lots of broadcast stations below 1MHz (nightime view)

I then remembered,  that to protect my K3 from a very local broadcast station on 1.7MHz, I had built a 1.7MHz Highpass filter. It didnt take long to find it in the storage unit, so I put it in front of the ANAN-10. Overloading went away. I also looked on the spectrum analyser:-


Everything below 1.8MHz has gone.

Curious,  I went to the Apache-labs web site and looked at the specification of the ANAN-10. Whereas it has LPF after the PA to comply with spurious emissions, it has NO filtering in front of the receiver which is broadband 10kHz-55MHz. May be time to look at some BPF for it! The only good thing about the lack of filtering is that this is fine for running the DL3HVH CUSDR32 software which allows same time monitoring of 5 bands (160 thro 10m) off a sngle antenna.

Sunday, November 10, 2013

ANAN-10 as a Transverter Driver

While aligning the G4DDK 4m Xverter, one thing I did discover on the ANAN-10 was that the output from the Xverter port is not vey clean.

Initially I set the output power on the power meter to 5mW (7dBm). I then hooked it up to the spectrum analyser  At  +7.8dBm at 28MHz from the XV port 2f was -24dBC, 3f was -20dBC. :-



I then backed off the output ~3dB to 5dBm and things improved dramatically. 2F was over -45dBC, 3F was -28dBC



The moral is;  dont push the PA on the Hermes board and always use a 28Mhz LPF.  To be safe the transverter was left set for 3dBm drive and an LPF will be built:-





2F is -48dBC, 3F is -32dBC.  For the record PA gain is set for 43.0 in power SDR and the xverter output coupling  was set to -19dB by choice of resistor values on the PCB (My hermes board came from TAPR which did not have the resistors or connector fitted for the transverter output). My setup was assembled shortly after ANAN-10 was launched. It used the Hermes board from TAPR and the PA board/Case from Apache-labs. The completely assembled version was on back order. The antenna port and the TX output port on the Hermes board are left unterminated which should make no difference as the PA is disabled but still providing a load.

G4DDK Nacton 70MHz Transverter

While over in England a month ago I managed to get one of the Beta short kits for Sams new 70/28MHz Transverter, the subject of his talk at the RSGB HF Convention in mid October. It is also described here. The hard to get components Sam supplied,  but the rest were all obtained from Mouser electronics

Took a couple of evenings to build and align. Interfacing with my Anan-10 SDR was easy as the xverter has split 28MHz input/output. Output was measured at 21dBm and the gain was 16dB, very much to specification.

I had hoped to put it in a German tinplate box to shield it from the Amplifier module but it is too small. Will have to rethink the housing.

Next task is to build an amplifier to provide sufficient drive to drive my 300W solidstate amplifier for the band.







Friday, November 8, 2013

7" LCD Display for the Beaglebone Black Spectrum analyser

I had been looking for a 7" display to use with my Beaglebone Black spectrum analyser for a while. The recommended 800x480 resolution LCD7 is still unobtanium. Searching ebay I saw many 7" LCD kits (ie uncased) with HDMI/VGA/2 composite inputs running off 12V, so I ordered one for $50.


It took just 10 days from ordering for it to get here. It was VERY well packed in bubble wrap. It powered up fine and displayed VGA from this laptop, composite video from the RPI and HDMI from the BBB with no issues. Just need to find it a case to protect it

This display system doesnt have the high resolution needed for some projects but will work fine as a portable monitor.  For a higher resolution small display for the RPI/BBB  I have signed up for the kickstarter project hdmipi-affordable-9-high-def-screen-for-the-rpi

Friday, November 1, 2013

WWVB reception on 60kHz

Having built the WA1ZMS loop, I was intrigued to see how low in frequency it would work without retuning. The lowest frequency signal I could think of seeing a signal was WWVB on 60kHz so i set the ANAN-10 to that frequency



There was a good signal and it did what WWVB should do (there is no voice or cw id on WWVB)

I then searched the internet for a decoder. There were a lot of hardware decoders but very few that could decode audio input to the soundcard. I then found clock1.1 from F6CTE which was easy to install and has a choice of time signals it can decode:-


One point to note is that after being installed the programme auto launches into a calibration routine for 3 minutes during which time there is no spectrum display. Make sure the frequency matches the frequency of the incoming audio tone. The following shows a complete time sequence reception:-



Admittedly this solution is not the most cost effective. Last year I picked up an Oregon scientific WWVB clock, with LCD display and alarm functions for $1 from the local charity shop!

Wednesday, October 30, 2013

Building a 477kHz receive loop





With the approach of the winter LF season it was time to look at building an LF receive antenna to put on the apartment balcony. My attention was drawn to the design by wa1zms A Simple Loop Antenna for 500 kHz. It looked straightforward to build. The half inch wood was available at the local hardware store. The hard question was how to cross the wood at the centre. Luckily Bob WA5YWC stepped in and milled the crossover portion to be a snug fit, solving that issue. Each arm had 8 holes (for the 8 turns of wire) spaced at 0.5". The two arms were secured with a brass screw to allow dismantling

I had found some 10/46 Litz wire on ebay. It soon became very apparent that this was too fragile to use as it snagged and broke with ease. A further internet search revealed a supply of the more robust 10/26 Litz wire from scotts electronic Parts It was not cheap but it would do the job. The wire was mounted on the frame easily and terminated with two brass nails. I measured the inducance and found it was 65uH, meaning around 1700pF would be needed to resonate the loop at around 475kHz. This value was soldered across the brass pins.


A visit to the local emporium produced all the components for the preamp including a box and stripboard. This was assembled and attached to the mast with adhesive backed velcro and a 9V battery attached. . I hooked it up to the ANAN-10 and took a listen around 475kHz.  but I noticed that the PowerSDR software was indicating an A/D overload. The preamp was acting as a wideband power oscillator! I re-examined the wiring finding a couple of extra short circuits which were fixed. Reconnecting it to the receiver I could hear the WG2XIQ on 475.7kHz and the antenna showed the expected very sharp nulls

131028 0152  25  -7  0.3   0.475663  WG2XIQ EM12 30
131028 0156  24  -8  0.5   0.475663  WG2XIQ EM12 30
131028 0200  23  -9 -2.0   0.475663  WG2XIQ EM12 30
131028 0208  10 -21 -1.4   0.475663  WG2XIQ EM12 30
131028 0212  10 -21 -0.3   0.475663  WG2XIQ EM12 30
131028 0216  11 -20 -0.2   0.475664  WG2XIQ EM12 30

Wednesday, October 2, 2013

Beaglebone Black Spectrum Analyser




I had seen Stephen Ongs youtube video and decided to give it a try. I followed the detailed instructions at  http://robotics.ong.id.au/2013/08/25/viewrf-rtl-sdr-spectrum-analyzer-for-bbb-software/ (remembering to include the "opkg install libusb-1.0-dev" mentioned in the comments) and it worked first time! I used a monitor not the LCD-7 Display ($150 if you can get them!)

I did not need to expand the file system to increase the available space to the full 8GB. When installed it only used 44% of the around 2GB available

The display (like the RTL-SDR dongle) has a bandwidth of ~2MHz but a 2GHz spectrum analyser for $65 one cannot complain

Tuesday, October 1, 2013

BeagleBone Black Ubuntu 13.04 with desktop... FAILURE!!

Flushed with success of getting Ubuntu 12.4 working with a Desktop I decided to see if Ubuntu 13.04 would work with a Desktop

I downloaded ubuntu-raring-13.04-armhf-3.8.13-bone20.img from http://circuitco.com/support/index.php?title=Ubuntu_On_BeagleBone_Black#Main_Process unzipped it and wrote the image to an 8GB microsd card using win32diskimager programme on my windows machine

The microsd booted and gave me the ubuntu 13.04 welcome and login prompt. which resulted in the Ubuntu command line prompt. I expanded the file system using the instructions at http://www.armhf.com/index.php/expanding-linux-partitions-part-2-of-2/ to maximise the space available for the desktop. another

sudo apt-get update
sudo apt-get install ubuntu-desktop

and off it went installing again.  Four hours later I came back and saw the install was finished and rebooted the BBB and up came the familiar Ubuntu desktop and login prompt. However the mouse cursor was violently twitching and the desktop background flickering. I typed in the password, moved the mouse and the BBB froze and all the blue LED stopped flashing. I powered off the BBB and repeated the process and it still twitched and froze when the mouse was moved. Think I will stick with 12.04 desktop!!

Monday, September 30, 2013

BeagleBone Black Ubuntu 12.04 with desktop... SUCCESS!

A while back I put aside my BBB as I could not get a stable Desktop under Ubuntu see here

I thought by now software may have stabilised and decided to have another attempt

First thoughts went to flashing the onboard EMMC on the BBB board with Ubuntu and running it from there. I  found a suitable image https://rcn-ee.net/deb/flasher/raring/BBB-eMMC-flasher-ubuntu-13.04-2013-09-27.img.xz downloaded it and put it on an 8GB microsd card. Put it into the BBB slot and power it up while holding down the boot switch (the near the hdmi connector) till the blue lights start flashing. Then wait. When complete all 4 blue LED will come on and stay on
Remove the microsd card and reboot. The BBB will start running Ubuntu. At this point I  had to edit /etc/networks/interfaces to set up my static IP for the home network. I could then do

sudo apt-get update
sudo apt-get install ubuntu-desktop

Went away, when I came back 2 hours later there was an out of disk space message. The 1.9GB of EMMC was not enough!

I reverted back to debian by flashing the eMMC with the image "BBB-eMMC-flasher-2013.06.20.img.xz" from http://beagleboard.org/latest-images. This was put on an microSD card and the BBB powered up with the boot button pressed. Wait till all 4 LEDS are on to show it is finished. Note you cannot flash EMMC if you are running the OS on the EMMC.

I decided to use 12.04 LTS as it was more mature. I downloaded ubuntu-precise-12.04.2-armhf-3.8.13-bone20.img.xz from http://www.armhf.com/index.php/boards/beaglebone-black/#precise unzipped it and wrote the image to an 8GB microsd card using win32diskimager programme on my windows machine

The microsd booted and gave me the ubuntu 12.04 welcome and login prompt. I expanded the file system using the instructions at http://www.armhf.com/index.php/expanding-linux-partitions-part-2-of-2/ to maximise the space available for the desktop. another

sudo apt-get update
sudo apt-get install ubuntu-desktop

and off it went installing again.  Four hours later I came back and saw the install was finished and rebooted the BBB and automatically displayed the familiar Ubuntu desktop with no flickering or Instability. Success at last!


Saturday, September 21, 2013

PAC-12 Antenna

Antenna in use at rear of apartment block

I spent some time looking for a cheap antenna for portable expeditions. The wire in the tree is OK but not repeatable. Looked at the buddipole but that needed a support mast and $250.

A while ago I built my Version of the NJQRP PAC-12 antenna which was now in England. Decided It was time to build another one

Most of the items needed were available by walking to the local hardware store and Radioshack. The whip section was the one I got from Buddipole, strengthened with the ferrules I bought from them at Hamcom

I made a couple of alterations to the original design, mainly in the way of interfacing the UHF connector to the antenna using an electrical conduit boxes.

Full details of how i built this one will be on my web page shortly. The parts including a new whip cost $45
Feed point

15m with radials

15m coil


Friday, September 20, 2013

$1 GPS Receiver

Looking through the parts box I came across the Airlink Communications  CDMA C3310 vehicle tracker bought for $1 which was used to provide position updates derived from GPS over the CDMA Phone network and had supposedly a GPS receiver. Time to investigate

 In true ham spirit the covers were  removed first.After I opened the box I found a Verizon CDMA phone module and a GPS. On the back panel was a 9 pin RS232 serial connector a connector for GPS antenna an antenna connector for a CDMA antenna and a 12V power connector. I hooked up a computer to the serial port an active GPS antenna to the GPS port and 12V to the power conenctor and waited. Nothing came out of the serial port, however after a while the GPS lock LED on the front panel did illuminate. Time for a web search.




Luckily I came across a document on the unit which I have put on my web site.  raven-cdma-airlink_document.pdf  From this I learnt that by connecting a terminal emulator to the serial port at 1152000 baud and issuing an ATGPS1 command I could get GGA RMC and VTC NMEA strings out of the unit every second. Unfortunately I could not find a way of making the unit remember that setting when it was power cycled. I searched with a logic analyser but could not see a 1PPS signal which was not surprising as the application does not require accurate timing

 I think with a tweak to my GPS LED clock code, originally designed for Motorola GPS boards I could turn it into a GPS clock, so the $1 is not wasted.




Saturday, September 14, 2013

RAVPOWER WIFI Disk





I have been looking at ways to extend the memory on my 16GB Ipad. Cloud storage is all well and good if you can see the cloud, on a lot of occasions I cannot.

Searching the internet I came across a RAYPOWER Wifidisk. Title is a bit misleading as it doesnt actually have any storage space onboard.  It is about the size of a 2.5" external hard drive case. which is good considering it has an onboard 3AH battery that can be used to power the device and if needed the IPAD.

It can be used as a private WIFI network but can be used, at the same time as a WIFI Hotspot to connect via your wifi router to the internet. It has a socket for an SD/SDHC memory card that fits flush to the case (unlike the RPI) and a USB 2.0 socket into which a USB memory stick or USB hard drive can be plugged in. A microusb socket is provided for external power

Searching EBAY I found one for $44 shipped. I also ordered a 64GB SD card on ebay from
sirdouglash. The WIFISD Unit arrived and powered up fine but when the SD card arrived it proclaimed it was a 1MB card despite my best efforts to persuade it otherwise. The seller refunded the cost of the card but wasted a week of my time.

Today I went to microcenter as they had Sony 32GB SD cards for $24 so i bought a pair and installed one in the WIFIdisk

There is a windows utility that can be used to set up the unit called Mobilefun. I installed it and connected the unit via the USB cable to the computer and set up name password and how to connect to the Internet via my WIFI Router, I also installed some MPG4 and .wav files to test streaming

I installed the free Airstor app on the Ipad and directed the IPAD to connect to the WIFISD device shown in my available wifi signals. Doing this allowed me to play audio and video files and I could still connect to the Internet

Next it was the turn of my Nexus 7 Android device. The Free "Airstor for Pad" app was found in the Google store and installed. I again connected to the WIFISD device shown in my available wifi signals. Doing this allowed me to play audio and video files and I could still connect to the Internet.

As  a final experiment I plugged in my 500GB hard drive into the WIFISD and managed to stream video to the ipad. Not being an SSD not sure how long the battery would last though.

Monday, August 26, 2013

Fort Worth Nature Centre and Refuge

While in Fort Worth for the FTWSO concert series I looked for a place to go exploring on the Sunday Morning. Searching the internet I came across the Fort Worth Nature Center and refuge http://www.fwnaturecenter.org/ which had some creatures, scenic drives and trails. It is off the Jacksboro highway, NW of downtown Fort Worth.

Having paid my $5 admission i made straight for the Visitor centre. I did two walks centred there Caprock at 0.5 miles and Limestone Ledge at 0.2 miles. They also have two owls in the refuge, both hit by cars, a greater horned owl and a barred owl


I then drove to the boardwalk which is supposed to be a walk over the marshes over Lake Worth. Unfortunately it being August in Texas it was completely dry with no water in sight



The car park (EM12GU) was quite empty so a wire was thrown into a tree and the KX3 activated. A couple of stations were worked in the KS QSO party on 20m 1548 NoU/ALL 1549 W0U/SHA but the bands were quite dead and it was way too hot to operate from a car for any length of time.
The final visit was to the road named "Buffalo drive". Unlike earlier, when driving to the visitor center on this visit there were plenty of brown buffalos and also the rarer white ones

 By now it was noon and time to head for lunch and then to Bass hall

Sunday, August 25, 2013

Fort Worth Symphony "From Russia with Love" concerts





While listening to the local classic FM station on 101.1MHz  on the way to work last Monday I heard adverts for a three concert series this weekend entitled "From Russia with Love" by the Fort Worth Symphony Orchestra. They normally do a series of three concerts on a theme as an intro to the concert season; this year the three were dedicated to the memory of Van Cliburn who died earlier this year

A total of Six pieces all by Russian composers with three piano pieces played by Cliburn 2013 medalists and three russian Symphonies; not to be missed, so tickets were purchased. $18 each for the 3 concerts in the centre of the lower mezamine

I drove the 47 miles to Fort Worth direct from work on friday evening and even had enough time for banana spring rolls desert in PF Chang 3 blocks from the concert hall in the usual pre-concert ritual.

Friday night started with a eulogy to Van cliburn which was inaudible due to the bad PA audio (still) in the Bass Hall  The first half  had Beatrice Rana, the 2013 Silver medalist (wearing a silver sparkly dress as a reminder?) playing Tchaikovsky’s Piano Concerto No. 1. . The first movement was a bit slow and she was overpowered by the orchestra at times but very enjoyable. Her encore was the Schumann-Liszt composition, Widmung. The second half was the FTWSO playing Tchaikovsky’s Symphony No. 4. Fort worth star telegram review. One other feature  of the Bass hall is a Starbucks across the road in the Barnes and Noble bookshop which serves coffee until midnight, you dont get that after theatre in Malvern!

Saturday night had Italian pianist Alessandro Deljavan a 2013 semi finalist (rumoured not to have progressed further because of facial/body contortions while playing!) playing Rachmaninoff’s Piano Concerto No. 2  in the first half which was a very different interpretation than normally heard . . His encore was the Chopin’s B minor Etude which was stunning. The second half was the FTWSO playing Tchaikovsky’s Symphony No. 5 underwhelmingly.  Fort worth star telegram review.

Sunday afternoon  had Sean Chen, the 2013 Third place playing Rachmaninoff’s Piano Concerto No. 3. in the first half (same piece he played in the Cliburn final 11 weeks previously).  His encore was a mystery until afterwards due to the awful pa system in the Bass Hall (just as bad as during the Cliburn competition)."Chen turned to two violinists and two cellists in the symphony and asked each of them to play a note of their choice. He then returned to his piano bench and did about three minutes of improvisation on those four notes."  A first for Bass hall!. The second half the FTWSO playing Tchaikovsky’s Symphony No. 6 (Pathetique) which was well played but the most memorable part was the raspy sounds produced by the horns   Fort worth star telegram review.

The east angel on the front of the Bass Hall.  They were hewn from solid marble in California then shipped to Texas. The head fell off the first one to arrive and had to be remade from scratch and reshipped

53 mile drive back to the apartment; an enjoyable weekend!

Sunday, August 4, 2013

RPI R820T RTL2832 SDR Server

As a way of keeping an eye on conditions i have taken to installing the rtlsdr dongle out on the balcony hooked up to a 50MHz dipole and using the Dell laptop as a display sitting on a chair. The weather in Dallas has returned to Summer normal about a week ago after having a week of mainly rain so 100degrees F plus is now the normal. Too hot to sit out on the balcony and look at the bands, There had to be a better solution

Searching the Internet I came across a page by EB1HBK "Receptor SDR remoto con Raspberry Pi"
on how to set up a raspberry pi as an RTLSDR remote server. The pages are in Spanish but despite having had my Spanish corrupted by Mexican Spanish I managed to work it all out and get it up and running

The RPI sits out on the balcony with RTL-SDR and power supplied through the USB hub from a 5V 4A PSU acting as a server. It is connected  via an ethernet cable to the router. The server can be started remotely using SSH through the Putty programme

The laptop in the airconditioned apartment runs sdrsharp. In SDR Sharp the device is set to "RTL-SDR TCP" with the IP of the RPI (192.168.1.64) and the default port of 1234

Sunday, July 28, 2013

Infrared decoder Project


As is quite common nowdays , our TV does not have speakers, the received audio has to be sent to an external audio Amplifier. When playing back video files on the PC it also needs to send audio to the same amplifier resulting in the need to rearrange cables behind the TV when wanting to swap over. There had to be a solution

I took a look on ebay.com whereas HDMI switch boxes were available boxes to switch Left and Right Audio on Phono jacks were rare and expensive

I wondered if I could use the TV remote and build a decoder to switch between the 2 sources. As I had a couple of Arduino Unos, bought when on offer at radioshack, they seemed an ideal candidate

Searching the internet I came across some web pages at adafruit.com that would be useful. A walk to radioshack (I am now only 300 yards from one now) procured the necessary IR detector.It was hooked up to the arduino and the software loaded from http://learn.adafruit.com/ir-sensor/reading-ir-commands. I pointed the IR remote that came with my RTL2832 TV dongle at the decoder and saw the pulse codes. The software allows the pulse codes to be recorded.  and placed in the file you can use as a reference to switch arduino outputs. I choose the red button to choose TV as source and Green button for Computer.

Next a 6V DPDT relay was found in the junk box and mounted on an arduino protoshield board. The relay was switched with a 2N7000 FET from the arduino output. Two LEDs were added in software and hardware to show the audio source. The whole assembly was mounted in a Diecast box with a hole filed out in the front panel to allow the IR detector to be mounted.




The arrangement worked fine but I kept losing the RTL2832 controller, which was small. I decided to use two of the spare buttons on the existing IR controller, Not hard, all I had to do was record the pattern and put it in the lookup file

A useful afternoons work!