K6TU.NET - Propagation as a Service

There are two reasons why I haven't been posting regularly - last year I was asked to step in as Vice-President & Contest Chair of the Northern California Contest Club.  As a club we decided to go all out for the ARRL RTTY Roundup and the members asked for propagation charts to help with strategy and band planning.

I had produced propagation predictions using VOACAP before and so I volunteered to develop predictions for each of the 5 contest bands for a full 24 hours.  Wow!  It took me forever!  VOACAP runs very quickly on a reasonable CPU computer but generating the graphics required a lot of hand manipulation using VOACAP's image generator and Photoshop.  All in all, it took me half a day to produce all the graphics.

The graphics were a a great success and NCCC won the 2012 RTTY Roundup hand down - setting a new record!  The propagation charts were such a success that the club members wanted them for the next contest - that took me about 6 hours to generate.

At that point, I was hell bent on finding a way of automating the entire generation process - that took me almost 2 months of night & weekend coding but by late March I had it done.  Now generating the predictions took less than 10 minutes using the capabilities of my MAC under its UNIX colors!  Then one of the members asked me if I could get the same thing running under Windows...

By the time I looked at all the different packages I had used, I came to the conclusion that what was really needed was a web service.  With a web service, I could remove the learning curve of customizing VOACAP predictions to a level where it would be as simple as filling in a form and clicking a button.  No learning curve, no software to install.

I started work on K6TU.NET - Propagation as a Service web site at the end of March.  I launched the site into a closed beta in September after 6 months of heavy lifting coding and assembling an industrial grade web site.

I'm delighted to announce that the site went live into production this last weekend.  Stop by and take a look what you can achieve at the click of a button - a good way to do that is to visit the Quick Tour page and see the forms and graphics.

Here are a couple of examples to whet your appetite...

This is an example of the regular prediction you can run - this is a screenshot of a single band/hour combination where you can see the predicted propagation by visualizing YOUR signal strength across the world.


And here is an example of the Contest Strategy Prediction - this is perfect for planning which bands to use for either search & pounce or CQ running during a contest.



K6TU.NET supports many different types of propagation predictions and has both free and premium features.  I hope you will stop by and take a look!


Contest Knob – Announcing the Product

Building the Tuning Knob and getting it working was just the tip of the iceberg.  My sense from the beginning was that if I had a need for a contest control for my FlexRadio based station, others would too!  So it didn't take long before I started thinking about taking the tuning knob from a project to a product.

Building a product for use by multiple different people is a very different proposition than simply building a project.  A project just has to work and seldom is the cost a significant issue.  A product on the other hand has to meet a set of requirements from functionality all the way through to volume production.  

Kevin K6TD and I had been through this many times before – both in our professional life developing products for companies we worked for as well as our own company.  Not only do you have to produce a product but you also have to sell it!

We decided to build the tuning knob with product production in mind, get it working, build enough units to prove out the user requirements and then look for someone who would be interested in producing and selling a product.  Fortunately we had a team of people in Steve K5FR, Kevin and I who knew how to do this and moreover, weren't daunted by the prospect of finding a partner.

It didn't take us long to get the first prototype version designed, built and working!  I guess it's deeply embedded in my genes but the thrill of building something and getting it working never gets old.  Assembling the rev A boards was no exception – we built up a handful and starting giving them to folks we thought would give us good feedback.

We sent one of the boards to Greg Jurrens, the Vice President of Sales & Marketing at FlexRadio Systems.  Greg is an avid VHF operator who also likes to operate contests.  Greg used the tuning knob and really liked it – he liked it so much that he called me and asked if we'd ever thought about turning the tuning knob into a product – BINGO! We had our potential partner!

Over the next few months Greg and the team at FlexRadio gave us great feedback on the knob and we began talking about what be necessary for FlexRadio to take on production and sales.  One thing led to another and eventually FlexRadio assigned Graham KE9H to work with us to turn the tuning knob into its final version.

So today I'm delighted to be able to announce that FlexRadio will be releasing their FlexControl product at the International DX Convention at Visalia, California next week!  FlexControl is the product version of the Tuning Knob designed and built by Kevin K6TD and myself with full software support in DDUTIL provided by Steve K5FR.

Gerald Youngblood CEO of FlexRadio Systems and Greg Jurrens have been kind enough to allow me to provide this preview of the product ahead of its appearance at Visalia.  Greg tells me it will retail for $129.95 and will be available for orders & shipment by the time of the Dayton Hamvention in late May this year.

It's been a great journey and we're delighted at the outcome!

Origins & Refinement of the Contest Knob - II

After my experience with the first generation knob, I realized that a complete re-think was needed for a new knob. Ease of use and low cost were critical coupled with a system design approach to get maximum utility out of the solution.

Kevin K6TD and I have worked together for many years – both for the same companies and also with a number of product ideas we'd commercialized ourselves. Kevin is a very successful VP of Engineering and a serious hardware wizard - so I decided to see if I could rope him into a new project. Despite a busy work schedule, Kevin agreed and we started talking about the specification for the new knob.

A simple list of requirements quickly took shape:

  • Cost effective
  • Simple to use
  • Silky smooth tuning (no tuning detents or lag)
  • Compact form factor
  • USB connected
  • Seamless PC side integration

The need for seamless integration on the PC side was a no-brainer – it was a critical element to get that silky smooth tuning experience and part of the system design to eliminate tuning lag. The logical place to provide this was in Steve K5FR's DDUTIL – "the" MUST HAVE for station integration for any FlexRadio owner. You can find Steve's software on his web site.

DDUTIL is an amazing piece of work. Think about all the different elements that make up a modern radio station (amplifiers, power meters, antenna rotators, antenna controllers, switching matrix, filters, multiple software programs…) that need integration. Integration and automation can simplify and streamline operation. Core to this simplification is getting information from the radio to each of the station components – especially frequency information. DDUTIL sits on the CAT control stream provided by PowerSDR and manages the distribution of CAT data to the station components. You can think of DDUTIL as a CAT multiplexor and station component manager.

I got to know Steve shortly after I purchased my Flex 5000 – I'd decided to add an Expert SPE-1K amplifier to the station and wanted to be able to control it via DDUTIL. The Expert amplifier was on the DDUTIL "to do" list and so I emailed Steve to see what he was planning. The reply email came quickly! Steve was ready to go as long as someone could help him debug the implementation. We worked together to get support for the Expert working and during several long phone calls, found we shared a lot of ideas and common experiences – and had a ton of fun working together!

In a quick phone call to Steve I described what I was thinking and got a resounding "I'm in!" – We had our development team up and running!

Kevin started looking for a cost effective replacement for the optical shaft encoder used in the original project. In parallel, Steve and I worked on defining a control protocol between the new knob and DDUTIL. We opted for a simple control set modeled after the ubiquitous CAT format – simple ASCII text commands with a ';' terminator. The spec for the CAT stream quickly took shape and we started thinking about how to prove out the different pieces of the design.

The first step was to find a development board using the same PIC that Kevin had selected as the core of the system. We opted for a development board sold by Futurelec, a company based in Asia – at less than $50, a good basis for the proof of concept (POC) system shown below.

The POC system is simply the development board with a shaft encoder and LEDs mounted on a daughter board. The daughter board connects to the peripheral connectors on the Futurelec board. This enabled me to start developing the software to handle the shaft encoder and the USB port to connect the board to the PC.

The development of the USB software was greatly accelerated by using Ian Harris' PIC PACK library – I covered this in a previous post which you can find here. I quickly got the development board connected to the PC via USB and began implementing the CAT-like control protocol to talk to DDUTIL.

In short order Steve had the basic support for the knob integrated into DDUTIL and had the POC system working as an active tuning knob with DDUTIL. With a little bit of tweaking in DDUTIL we realized we were pretty close to that "silky smooth tuning" effect we were looking for but if you really spun the knob quickly, there was still a lag.

Kevin suggested I implement acceleration detection – change the tuning rate generated by the knob when it was turned quickly. Some thought and basic calculus later, I had this figured out and suggested to Steve that we modify the CAT stream so that the knob could signal that a faster tuning rate was required.

As we were getting this done, Kevin sent the hardware design to the PCB manufacturer and we built up a handful of tuning knobs. You can see this rev A version of the knob below – you can get an idea of scale as the physical knob itself is a little over 2 inches in diameter.

Acceleration detection got us a long way to eliminating the CAT queue but the lag still showed up with aggressive tuning. The challenge was the chain of commands sent to PowerSDR to change the tuning rate – multiple CAT commands to effect a single tuning step – regardless of the size.

Steve had worked closely in the development of DDUITL with Bob Tracy K5KDN who developed the CAT support in PowerSDR. With Bob's help and support from FlexRadio, we were able to get a couple of new CAT commands implemented in the next development build of PowerSDR. This reduced the number of commands needed to tune a step to one. This nailed the CAT queue problem and we got the coveted "silky smooth tuning" we were looking for!

Feedback on the rev A board was positive – we had used the switch incorporated into the shaft encoder to implement a number of different features. We used switch clicks much like mouse commands – single, double and long click. Clicks are detected by the knob and signaled up to DDUTIL so that it can change different controls on PowerSDR.

At the time, Steve was also working with Lee Crocker W9OY to get DDUTIL as the control center for SO2R operation. Lee really liked the idea of the Tuning Knob but said he wanted some additional control switches that could be used with DDUTIL to automate other aspects of station control.

We had decided to spin the PC board to make some manufacturing changes and so it was a logical decision to add three simple push button switches to the hardware. Kevin re-laid the PCB and sent out for board manufacture. The boards came back and we built the rev B version of new tuning knob.

Between us, we built a fair number of rev B units and got them to folks for "real world" testing. This time the feedback was very strong and very positive – we knew we were getting very close to the final solution!

We started the process of getting the tuning knob turned into a product - more on this in the next post…

Adding the auxiliary switches was easy for both hardware and software but I'd made a decision to detect just a simple on/off operation – allowing another three actions to be automated. By now Lee W9OY had his hands on a rev B unit and just like Oliver Twist wanted "More!" – Lee asked for the same kind of click detection on the auxiliary switches as I'd implemented on the shaft encoder switch.

I groaned when I heard this request… since the auxiliary switches had been an afterthought, I'd grafted support for them into the code rather than taking an integrated approach. Supporting multiple click detection on the auxiliary switches required a fair amount of code re-factoring to avoid an even worse "graft" – ok, kludge!

Over Christmas 2010 I finally found time to re-factor the code, document the changes to the CAT stream to allow for signaling auxiliary clicks to DDUTIL and get new code off to Steve.

By late January 2011, we were DONE! Steve added a whole new tab for configuring the knob into DDUTIL and Lee was happy! One of our knob users in Europe took a high place in a major contest and gave the knob the credit for his success.

The journey from concept to product has been very interesting. We started with a distributed development team of three – unique because we've all never met in person. The final version required the collaboration of two more people in different parts of the country… and we've all never met in person or even had a joint conference call together. Email was our primary communication tool and it worked because of a shared vision and mutual respect.

Finally, I'd like to recognize…

  • Kevin K6TD and Steve K5FR – they shared the vision and gave their full support to this project. Without them, the tuning knob would likely never have seen the light of day!
  • Team FlexRadio Systems for their willingness to incorporate changes into PowerSDR that we requested – there aren't many companies that will take this kind of feedback so willingly to heart from their customers!

In the next post, I'll talk about the final steps of the journey…

Origins & Refinement of the Contest Knob – I

The K6TD & K6TU Contest Knob is finally approaching production (no, not giving out the date yet!). So I thought I'd give a little background on how the knob came to be and how it got refined from the original idea to the product version.

My conversion to a radio station without knobs and buttons began in the summer of 2003. I'd changed QTH and finally had enough space to start thinking of serious antennas. However, there was one wrinkle… I wanted to have the antennas located away from the house for aesthetic reasons. Not wanting to pull long lengths of coax, I elected to remote the radio to be close to the antennas. At the time, I chose the black box version of the Kenwood TS-2000 (the TS-B2000) that is completely controlled via a PC – no front panel beyond an on/off switch.

The station setup worked well but I missed the simple process of tuning across the bands – using a mouse wheel didn't cut it with the Kenwood software. So with the encouragement of Kevin K6TD, I set about implementing a PIC based tuning knob. This was my first PIC based project – fortunately both the hardware and PIC software were simple. I built the first generation knob around an optical shaft encoder – I think I paid about $100 just for the encoder itself – a precision unit that produces 1000 steps per revolution. Total overkill but it worked!

The size of the optical encoder drove the selection of the case – for scale, the knob is just over 2" in diameter and the four screws visible in the picture secure the encoder. The case is about 4" wide and 6" or so wide. Looking at it now makes me think of an early 1970's car – big, square and ugly functional.

The PC software wasn't so straightforward – I wrote a Windows program that took input from the knob on a serial port and then faked keystrokes to the Kenwood control program. It worked ok so long as you didn't get too carried away with spinning the knob – the resulting tuning lag was a mess!

I wasn't very active until in the early part of 2009 I decided to upgrade my radio. K6TD was the catalyst for this decision; Kevin had become a serious contester and bent my ear about how much fun he was having especially after a serious station upgrade. Waving a large carrot, Kevin invited me to operate the 2009 ARRL Phone Sweepstakes with him as a Multi/Single station. Years earlier I had been an avid contester and the thought of radio sport got me motivated to improve the station.

By summer of 2009, I'd made two decisions – I applied for a vanity call sign to replace N6TTO (a pain on CW and a mouthful of phonetics) and after much research, ordered a FlexRadio Flex-5000 as the core of a new station. You can read more about that process here on some of the early postings on this blog.

My first serious contest effort with the Flex-5000 was the 2009 California QSO Party – considering low power (100 watts) and limited antennas (an HF vertical and G5RV dipole), I had a blast with about 430 QSOs. It was my first contest using logging software (N1MM) and operating the radio via PowerSDR – so although there were several times I found myself all "fingers and thumbs", I put this down to the learning curve of contest operating.

A few weeks later I found myself at K6TD operating Phone Sweepstakes. Wow! What an experience! Kevin had built an awesome station at his QTH in Cupertino. His home sits on something of a bluff with the ground dropping off in most directions. With a 3 element Steppir at 55 feet, an Elecraft K3 and full legal limit from an Alpha 87a amplifier, we were a serious signal on the band.

Kevin was a very gracious host allowing me first up in the batting order – the initial rates were probably around 100 QSOs/hour and I was having a blast – I was struck by how Kevin had worked to streamline the workflow – the logging program (Writelog) remained in focus the whole time and apart from using the main VFO knob or RIT control on the K3, you didn't have to touch the radio.

As I switched off with Kevin for a break, I realized that I need at least ONE knob to operate my Flex-5000 in a contest and optimize the workflow between radio control and the logging software. The seeds for the next generation tuning knob were planted…

Strange 20m RFI

This morning I noticed a very strange new RFI source on 20m. The signal repeats every 25 KHz across the band (above and below as well) and drift slowly lower in frequency over time.

From my location it peaks towards the North – I listened to one QSO where it was clear the folks on the frequency could hear the signal as well so it's not a local source of RFI.

I've uploaded a WAV file of the signal - click to listen.

You can hear a distinct chirp at the start of each transmission as though this was an oscillator being keyed by turning the power on and off. There are three distinct frequencies that repeat – you can see them in the following waterfall I captured from the Flex 5000.

This is one of the strangest RFI sources I've seen in quite a while… it's a ways away from Woodside I suspect so I'll probably never know what it was…

A broadband contest antenna for 80m

The challenge with contest operation on 80m is finding an antenna that works well over the range 3.50 MHz to 3.85 MHz.

As station enhancements have progressed, my 80m antenna has gone from a G5RV (a total compromise on 80m with tuner use being mandatory), to a homebrew 80/40 "shorty" dipole (good for about 80 KHz on 80).

After hauling the 80/40 dipole up and down for a year to tune it for specific contests, I started looking for a broader band antenna for 80m that wouldn't require a tuner and at the same time was simple to make.

Unusually, I didn't find the solution on the Internet but found a reference in ON4UN's Low Band Dxing handbook (just issued in the 5th revision and a "must have" for the low band operator) to the "80m Dx-Special" designed by Frank Witt AI1H.

The coverage of this antenna in the ON4UN book is sparse but did have a reference to a couple of articles in QST back to 1986 and 1989. Fortunately, as an ARRL life-member, I have access to the online archive of QST so I quickly dug out the articles.

The AI1H DX Special is an 80m half wave dipole that uses a coax resonator as part of the dipole legs. Here's a diagram with the correct lengths (the lengths in some editions of the ON4UN book are incorrect):

From the diagram, you can see three separate lengths of coax are used. The shortest length is used to establish an off center feed for the dipole as part of an impedance match and then crosses-over (coax center->shield, shield->center) at the connection to the longest length which acts as a capacitive section. The remaining length is a shorted stub which acts as an inductive section.

The remaining length of the dipole sections is made from 14ga copper wire. The antenna is fed as a T – in my case using a standard SO239 T connector via a sleeve balun (a length of coax cable that passes through a number of ferrite cores) to choke off common mode currents.

If you have access to the QST archives, you can find AI1H's excellent analysis of the underlying design of this antenna in:

  1. Broadband Dipoles – Some new insights, Frank Witt AI1H, ARRL QST Magazine October 196, pp27-37.
  2. The Coaxial Resonator Match and the Broadband Dipole, Frank Witt, AI1H, ARRL QST Magazine April 1989, pp22-27.

The three sections of the coaxial resonator in this antenna act as a combination of an impedance matching transformer coupled with a resonant LC circuit which broadens the range of operation of the DX Special to an SWR match of better than 1.6:1 across the range of 3.50 – 3.85 MHz. Using the coax as the resonator provides an efficient way to broadband the antenna with minimal added loss – the broadband operation incurs a 1 dB penalty at the band edges, less elsewhere.

Here's the SWR plot captured from the version of the antenna I built and put up.

From the first contacts I have made on 80m using the antenna, it radiates at least as well as the 80/40 shorty it replaced and the amplifier operates happily all the way to about 3.9 MHz.

A couple of construction notes:

  • I built the cross over section of the two coax stubs by simply soldering the coax together crossing over the shields and center conductors. I used 18 ga copper wire to wrap the sections together and then a high wattage soldering iron to make the soldered joints. I used a couple of pieces of a large tie wrap as a mechanical brace across the joint.
  • Don't substitute anything other than RG8U for the RG213. The lengths of the coax stubs are calculated based on the dielectric properties and velocity factors of these cables.
  • Be sure to waterproof the ends of the coax stubs. Water ingress will destroy the antenna in short order.
  • The coax sections add significant weight to the legs of the dipole so provide strain relief on the connectors at the center T. I opted to use crimp PL239 connectors because of their stronger mechanical properties than the solder-on type.

WSPR & HF Propagation

Last year I wrote a series of posts about my WSPR Transmitter - there's a link to the series of posts on the right side bar of this blog.

After running the transmitter for a while, I became really curious about some of the results I was seeing.  This led to another set of posts about using WSPR to compare different antennas back in April 2009.

I ended up creating a presentation about using WSPR together with antenna modelling tools (EZNEC) and HF propagation forecasting tools (VOACAP).  I've since given this presentation a couple of times but never published it on the web.

Last week, Tad Cook K7RA who writes the weekly propagation bulletin for the ARRL included some comments I had sent to him about using WSPR to evaluate current HF propagation by using the spots database on WSPRnet.org.  I'd also sent him a copy of the presentation by way of background.

Tad encouraged me to publish the presentation and also kindly arranged for Carl Luetzelschwab K9LA (who writes the monthly propagation column in WorldRadio) to review the presentation.

I've uploaded both the presentation and Carl's comments to the 'net and embedded them below.

Many thanks to Tad for the encouragement and to Carl for his feedback.


WSPR & HF Propagation


K9LA Comments

FlexRadio 5000 and California QSO Party

This last weekend was the 45th running of the California QSO Party and my second full time effort in that contest.

Last year's effort was my first serious contest with the Flex 5000 and proved out its awesome receiver performance. It also highlighted the need to improve the workflow between the software used to compete in a contest – in my case last year, the N1MM logger and PowerSDR (the software side of the Flex 5000 which does all the real work in DSP software).

The biggest challenge?... changing window focus between PowerSDR (mostly to tune the receiver) and the logging software. Remembering which window had the focus was critical especially since I'd left the keyboard short cuts enabled in PowerSDR. Imagine starting to enter the callsign of a new station, hitting the W key and finding yourself instantly QSY'd by 1 MHz!

I'd returned from a business trip to Asia the day before the contest and hadn't had enough time to test everything out before engaging in the CQP battle. As a result, I had not tested the N1MM voice keyer interfaced to PowerSDR. I'm sure with the right choices of WAV file sampling rate and VAC (Virtual Audio Cable) configuration that it could be made to work – but for me it was a bust.

Rather than call CQ (a few thousand times!), I saved my vocal cords by using the Quick replay function in PowerSDR having captured my own CQ call.

For a low power (100 watt) entry with a HF vertical (R5) and a low G5RV dipole I managed around 430 contacts in an almost full 24 hour effort. I had fun punctuated by some comic moments… for example, finding a VY1 for a much needed multiplier with 15 minutes to go and then doing an instant QSY because of the wrong window focus… I found him again with about 2 minutes to go!

My personal 2009 CQP post mortem had the following highlights…

  • Need a solution to radio control that keeps focus on the logging software
  • Get a working voice keyer integrated with a logging program
  • More power!
  • Better antennas

A few months work fixed the first three…

Window focus – during a contest, the most critical radio controls are main VFO tuning, ability to turn RIT on/off, tune the receiver with RIT and clearing the RIT offset back to zero. I wanted to be able to handle these operations without having to change window focus or use the mouse.

What I really needed was a knob – specifically a tuning knob to accomplish these features.

I teamed up with my friend Kevin K6TD to develop a USB connected knob. We iterated through a hardware test rig which I wrote about back in January 2010, a hardware prototype and finally a "pre-production" version.

Here's a snapshot (iPhone) of the pre-production unit. You can see the sloped front of the case, the three auxiliary switches we added based on initial testing and the three status LEDs. For scale, the knob show is about 2" in diameter and the box occupies a minimal amount of space on my keyboard tray. Rubber feet prevent the unit from moving around as you tune.

The knob integrates to PowerSDR via Steve K5FR's awesome DDUTIL. Thanks to Steve for all his work on DDUTIL in general and for his support of the knob in specific!

With careful system design, the knob provides flawless tuning of PowerSDR with zero tuning lag. The switch on the tuning knob itself (press to click) and the auxiliary switches provide control of many different radio functions such as RIT on/off, RIT clear etc.

Voice Keyer – I wanted voice keyer support integrated into my logging program – the last think I wanted was to change window focus yet again! Fortunately the voice keyer in Writelog works very well with PowerSDR via VAC. At $30/year, Writelog is a great contest logging program!!!

More Power – It was time for a linear amplifier. I wanted an amplifier that could be operated 100% remotely to integrate with my remote located station – all of 300 feet from the house and controlled via Ethernet. I eventually chose an Expert SPE-1K which integrates with the Flex 5000 via DDUTIL (again many thanks to Steve!).

Better Antennas – I decided to finally bite the bullet and put in a tower. I'd done bits and pieces of the planning a couple of years ago including the most important – determining how much work I'd need with the local planning folks at the town in which I live. I started the project in earnest in February of this year and by mid September, I was the proud owner of a 50' tower… all nicely painted green to blend into our semi-rural environment.

Here's a shot of the tower with a Force12 CS3 on top – this together with an 80/40 dipole at 45 feet were my antennas for CQP 2010. The Force12 will come down shortly to be replaced with a Steppir DB-18E.

CQP 2010

This year is the 45th running of the California QSO Party and also the 40th anniversary of the Northern California Contest Club which sponsors the contest. To mark the NCCC anniversary, the club is sponsoring a certificate for anyone who contacts 40 members of the NCCC – no QSL cards are needed, just a log extract file.

During the qualification period (basically October to the end of the year), all the NCCC members add /40 to their call sign when on the air – except when operating in CQP.

I gave the station a test run on Friday afternoon signing K6TU/40 on 20m late in the afternoon. The results were very positive – the new station and antennas were LOUD and I worked 70 stations in an hour without breaking a sweat!

Saturday morning dawned and I was up early – everything checked out and I waited for the start of the contest at 9am PDT. Boom! We were off and running – I ran 100 QSOs in the first hour and proceeded to rack up 1279 contacts in my 24 hours of operating.

The combination of the Flex 500, the tuning knob, amplifier and antennas worked like a charm!

I turned in my best contest effort ever, tripling last year's QSO count and more than tripling my score. I even managed a clean sweep – that was another first for me!

This year's post mortem?

  • I need an exhaust fan for the equipment room. Dumping at least 1 KW of heat into that space for 24 hours quickly raised the ambient temperature and required a careful eye on the PA temperature throughout the event.
  • I need to polish my CW skills – seriously polish! While I can use CW for DX contacts, my speed and comfort level aren't up to a contest with the higher rates and more adrenaline. All but one of the Q's I made this year were SSB – I think I could have added at least another 500 contacts if I'd also operated CW.
  • Human factors are a serious consideration when spending 24 hours butt-in-chair time. I took 5 minute breaks every hour to stretch, walk around etc and this worked pretty well.

All in all, I had a blast.

The Flex 5000 made my weekend – flawless operation, awesome performance and with the addition of the knob, great workflow.



101 uses for an iPhone in Ham Radio

Ok, so this isn't a list of 101 uses for an iPhone in Ham Radio but I bet there are at least those!

In the past I've used a handful of applications to make my life easier such as…

  • AA9PW HamMorse – CW trainer
  • HamLocator – uses GPS/triangulation to give the Maidenhead locator
  • Ham – provides Solar data
  • 3Dsun – great app from NASA that gives STEREO images of the Sun and alerts for coronal mass ejections, flares etc

But today I found a killer app – Clinometer.

I'm in the midst of a serious overhaul of the antenna farm – centering around putting in a tower with a SteppIR DB-18E at the top (we break ground for the foundation on Monday!).

Part of the overhaul is finding a new location for my 160m inverted L to a) raise it up as high as I can and b) put it in a location where I can use elevated radials.

I've got plenty of trees to use as support but how high are they? Enter Clinometer – a $0.99 application for the iPhone that uses the built in accelerometers to measure tilt of the phone.

Here's a screen shot of the application:

Clinometer has a "stability" lock which lets you lock in a measurement once a configured level of stability has been held for 2 seconds.

I used Clinometer by sighting alone one of the edges of the iPhone and capturing the measured angle. Add a tape measure to establish a base line and some simple trig and you've got a measured height.

For $0.99 it's hard to go wrong!

Works like a champ!

Locating Power Line Noise

Just as I was basking in the success of finding and resolving the interference that wiped out 160m and 80m, another source of RFI raised its ugly head.

Power line noise!

RF interference from power lines is caused by arcing as high voltage electricity bridges a gap to a lower "ground" potential on the power pole. Corroded or loose connections, cracked insulators… almost all of the hardware on a power pole can be the source of arcing.

I have an intermittent source of power line noise that affects 15 and 10m, usually in the late afternoon. This appeared a couple of weeks ago as our seemingly endless "wet season" began to show signs of running dry and the weather began to warm up.

The first time I heard the RFI (about S7 without the noise blanker inserted in the receiver) I was able to peak the direction of the noise using my HF yagi. So I grabbed my portable HF radio (an FT-817) and went for a stroll a down the road in the direction indicated by the yagi.

The stroll was short! On both HF and VHF I could easily isolate the noise to one of the poles by my house. But I wanted more! I wanted to figure out where on the pole the interference was coming from – all from the safety of ground level and complete isolation from 13 KV electricity!

Electric arcs generate ultrasonic audio – usually around 40 KHz and so way too high for human hearing. One of my friends, Ira K2RD mentioned that some years back he had started accumulating the part for an Ultrasonic Arc detector that had been written up as an article in the April 2006 issue of ARRL's QST… and would I like the parts???!

The answer was an emphatic – yes please, thank you, I'll be right over! So thanks to Ira, I got a kick start and serious motivation to get going.

I put the unit together yesterday and now just waiting for the RFI to reappear to put the unit together.

Here's a link to the QST article – note that Far Circuits sells a PCB for the design which was the basis of the unit I built. Once I had all the parts together, it takes about 6 hours to build including all the mechanical work for drilling the box, building the holder for the ultrasonic transducer etc.

For the curious… here are some pictures:

View of the parabolic dish with the transducer and mount.

Rear view showing the control box mounted on the PVC pipe

Control box: L-R, Volume, Tuning, Headphone jacks

I decided to add a second head phone jack wired in parallel – this way I can feed the audio from the detector into a video camera or digital voice recorder as a record. I think a short video showing the pole radiating on HF and VHF plus the arc detector makes a pretty compelling collection of evidence to present to the utility company.

My remaining addition to the detector is going to be a high intensity green laser pointer aligned with the focus of the dish so I can see exactly where the dish is pointed – the beam width is pretty narrow so I think I'll be able to isolate to the offending area on the pole with the laser. Thanks to Rick N6RK for this suggestion!