Notes from the Shack - March 2014

Contesting isn't for everyone, but when we talk about ARRL Field Day as an emergency preparedness exercise it isn't just about establishing long distance communications in the face of widespread disaster, but operational readiness and reliability. As the recipient of the Coffee Pot Award for my first shot at being a band captain, I've seen how important it is to have a solidly reliable setup.

Mazes of Software

Over the holidays I used Ham Radio Deluxe to participate in a few phone and RTTY contests. The last of these was the RTTY Roundup, and 30 minutes into the contest I was so frustrated with HRD I quickly installed the N1MM logger, MMTTY and 2Tone. Setup took less than an hour and the result was a much better QSO rate, easy identification of dupes (for non-contesters, this is slang for duplicate contacts, not for operators who are easily hoodwinked), and flagging of multipliers. The sudden increase in efficiency let me log more contacts in the dozen or so hours operating the contest than in 24 hours of Field Day - not necessarily an apples to apples comparison but still encouraging.

In conjunction with N1MM I used HDSDR to find signals using a Softrock Lite II connected to the IF of my K3. HDSDR can't control N1MM directly and rather than try to hack a solution while the contest was running I didn't use it for rig control. This resulted in a fair amount of knob spinning to tune in signals but as they were so close together it wasn't a big deal even at the dial's most precise (i.e. slowest) setting of 200Hz per turn. The IF output is picked off prior to the radio's crystal filtering stage, so the narrowest filter (250 Hz) can be used to feed the RTTY decoders while still being able to see a 100 KHz wide swath of the radio spectrum.

The default display in the MMTTY and 2Tone RTTY programs is amplitude over frequency rather than a waterfall. In general I keep the filter narrow (250Hz) and it's more like regular tuning than just clicking the mouse on the signal you want. What the programs lacked in point-and-click was made up by the better decoding accuracy, integration with the logger (worked call signs display in grey, new ones in blue, and multipliers in red, based on the rules of the contest), and fine tuning ability. Using two different decoders at once also helps to figure out the message when there is noise, interference and fading as they use different decoding algorithms. N1MM supports up to 4 decoders at a time which can be used to "vote" for the right interpretation.

I'm still working on finding the best way to integrate all the software without having them fight over the control ports and audio interface. LP-Bridge is a way to have two programs share the same serial port but it's a hassle managing all the layers of software, and is reputed to have performance problems as well as some restrictive licencing.

For non-contest operation, N1MM is usable but not ideal. It doesn't like to flip modes nor can it log modes that aren't supported in the Cabrillo format (JT65 and JT9 for instance, which I frequently use). So I set out in search of a better way, which will be the subject of a future post.

The Bottom Line

I'm not a competitive contester (yet), but using N1MM has transformed the contest experience. By using a footswitch and mounting the microphone on a boom for the January 18th North American QSO Party, it left my hands free to work the radio and the keyboard.

With that in place, the logging process didn't slow down the QSO rate and the number of contacts per hour has gone up substantially. With ARRL Field Day only 5 months away, the job now is to perfect the digital operation and reach the goal of doubling last year's score.

Postscript

I should hope that every club member who uses simplex communications, whether on HF or VHF, has signed up for Logbook of the World. While signing up isn't the simplest of tasks, setup is getting easier and uploading logs is simplicity itself, especially with a good logging program LoTW accepts both ADIF and Cabrillo files, typically used for general and contest logging respectively. I have noticed that contesters are much more likely to load their QSOs into LoTW, as are digital operators. The confirmation rates have been pretty good. Excluding the contacts from the 80's that I transcribed from my paper logbook and uploaded, the percentage confirmation is 59%.

The FT5ZM DXpedition

This DXpedition to Amsterdam Island has been showing up frequently in the spotting networks a lot lately. A lot of spotters have one complaint or other, about the FT5ZM operators or callers' bad behaviour of one type or another. So far, I haven't heard them well enough to try to call in the pileup - if I hear them at all.

When I saw an RTTY spot I though I might have a chance. I flipped over to the frequency but couldn't hear or decode anything, but I knew exactly when they were transmitting because they were operating split frequencies, and so the pileup would all transmit across a very wide spread of frequencies in synch with each other. Here's what it looked like.



The panadapter software isn't synched with the radio so while it appears to be on 10m it was actually on 20, but it was something to see this 40kHz-wide pandemonium break out every time FT5ZM called QRZ.

Notes from the Shack - February 2014

I was going to write about some complex logging software topics this month, which I'm sure everyone was looking forward to, but the arrival of a little device based on an Realtek RTL2832u chip changed my mind. I purchased the device from NooElec in the US for $17.95, plus $4 shipping (although I will confess to buying a bunch of accessories as well, more on that in another post), and it arrived at my office less than two weeks later. I have since seen similar units for less than $15 with free shipping to Canada. It looks like a large USB memory stick but has an antenna port on the side and comes with a small vertical antenna and a remote control.

The chip was designed for consumer use in Asia for receiving digital TV broadcasts on a computer supporting both demodulation and the USB interface. It is useless for that application in North America as we use different standards, but the same device works great as a simple Software Defined Radio receiver for approximately 25-1750 MHz.

Setup had a few tricks. I found the information I needed on the web which included using a non-standard USB device driver. The trick for that is to disconnect the computer from the Internet during installation so that the standard driver isn't automatically installed. If the standard driver is installed accidentally then it can be removed using the Windows control panel.

Just before I left work on January 29th, I downloaded everything I needed and on the train ride home everything was installed and working, including my long time favourite SDR program, HDSDR. On the way home I tuned in some mobile radio (couldn't tell who it was) and Pearson approach control. The next morning I was listening to local FM stations (the FM bandwidth is variable from 192KHz to 0), VE3YRC repeater and 2m, a local 6m repeater, and the Toronto Island Airport control tower. Not bad from the aisle seat of the GO train using a 4" long antenna and my shoulder as a ground plane.

If your transceiver has an IF output and upconverts to a high frequency IF (i.e. more than 25MHz) you can use the device plus software as a low cost panadapter. If, like mine, your transceiver has a lower IF frequency then there are inexpensive upconverting devices based on an open source hardware design available that will bring the IF frequency into an appropriate frequency range, as well as designs available for DIY on the web. The Ham-It-Up and the like can of course also serve as a standalone MF/HF receiver.

HDSDR went into a bit of frenzy when I accidentally tuned it out of the range of the RTL2832u (0 Hz, actually). I sent a report to the program's author, Mario, in Germany and within an hour or two he replied suggesting I install a different DLL to control the local oscillator frequency which fixed the problem. Other than that, there are no serious problems with the program or the device.



Steve VA3SRV has also been using something similar with the SDR# program. I noticed on the NooElec web site that a download package for SDR# and all the required drivers is available as a single ZIP file, which should make installation even easier.

From Steve's experience and observations of my own I wonder how many images I'm seeing. For $17.95 you're not getting a professional grade communications receiver and poor image rejection is a known "feature" of the device. A broadcast FM station was showing up quite strongly in the 10 metre band, for instance, and I see all kinds of signals in the 2m metre band, although those might explain why I see frequent desensing on my HF rig as they are very strong. In fact, this gadget may help me get to the bottom of the various RFI problems I see on HF.

This screen shot shows CHFI coming in a bit weakly.



HDSDR will display between 100Khz and 3MHz of spectrum centered around the frequency you choose. The entire 10m band can be viewed at once, for instance, or most of the 6 or 2 metre bands. It handles AM (including single sideband phase-locked to the AM carrier), FM, SSB and CW demodulation. With a virtual audio cable (or by feeding the demodulated audio output into another computer) it will drive all the various digital mode programs around, like MMTTY, FLDIGI, DM780 and FreeDV.

If you're looking for a way to tune in the 6 metre net, this little device will do just fine, attached to a suitable antenna for your QTH. It will also work with the 1.25m, 70cm, 33cm and 23cm bands, plus a whole lot more. If you want an way to try out SDR software without having to make a big investment it is also for you. Pretty good value for the cost of a couple of pints.

73,
Chris VE3NRT

Notes from the Shack - January

Elecraft makes a fine panadapter for my transceiver. Everyone I know who owns one tells me how helpful it is. One day I'll surely plunk down the $1K or more ($700 US as a kit plus shipping and HST, plus another $270 for the hi-res display option not including the additional monitor) to get one, but I thought in the meantime I'd try out the $21 Softrock Lite II IF kit. (Either way you need the KXV3A option on the K3 transceiver to be able to get at the 8.215MHz IF output).



Both setups work by analyzing the IF output of the transceiver and displaying a portion of the band. The P3 displays up to a 192KHz-wide segment of the band centred on the tuned frequency. The Softrock will do the same with a 192KHz audio interface, but mine is only 96KHz so that's all I get. Elecraft says that a wider slice is going to be available with a future firmware upgrade but that was more than 16 months ago. Mind you, there's a little device called a RTL 2832u which is wideband VHF/UHF SDR receiver that costs around $20 and doesn't require a sound card. It doesn't tune the HF bands so it's been used along with an upconverter (or with a radio that has its IF on the VHF frequencies) to provide a 2MHz wide display. Maybe the P3 may have to wait a little longer.

Construction and Setup

Building the Softrock took about 10 hours, not including a case for which I still need parts. I'm a relatively slow builder I suppose but it worked first time. There are only two relatively simple toroid transformers to wire up, which compared to the Softrock RX-TX I built a year ago was trivial. There are a bunch of surface mount parts - 10 tiny capacitors and 3 integrated circuits. These were installed with a regular fine-tipped temperature controlled soldering iron with very thin solder. It is fairly simple to do. Just apply a tiny bit of solder to one of the pads and then tack the part onto the PC board on that pad with the iron. Then run around and solder the rest of the pins (quickly!) one at a time. I had to redo a pin here and there after inspection and/or power-on tests.

Once built, there are 3 connections to make. It requires the same ~12v power as the rig, a (well-shielded) connection to the rig's IF output, and a stereo connection to the audio interface. Stereo is an absolute requirement for software defined radio to provide image rejection around the Softrock's local oscillator (LO) frequency. The LO is tuned 23KHz below the K3's IF so that it doesn't feed back into the transceiver. The kit comes with no connectors or box, so right now that's patched together and those parts are on order.

Software Setup

Once the Softrock's audio is getting into your computer, you need software to interpret it. There are tons of options, like PowerSDR (a free version of the Flex Radio software), Rocky, etc., but right now my favourite from my RX-TX operating days is HDSDR, although I might revisit the others to see how well they work with this setup. All of these programs are free downloads. Installation and setup of HDRSDR is relatively easy. It needs to be told about the audio interface, and there is a special setup screen for the receiver front-end. That is where all the main adjustments take place.

The Softrock's oscillator is not going to be exactly 23KHz from the K3's IF frequency. Mine was just under 1300Hz off. Furthermore, there are different offsets for each mode, so CW is different from SSB and AM. The exact numbers were determined by experiment, lining up the sound of the signal with the display. Once this alignment is done, you can identify signals visually on the program's waterfall display, tune them in with a single mouse click, and then use the mouse wheel or direct frequency entry to fine-tune the signal either by ear or with the waterfall display. This is excellent for zero beating a CW station quickly to an accuracy of a few hertz.

Because both the IF and the Softrock frequencies are fixed, HDSDR tunes by changing the transceiver's frequency. How is this done? Well the easy way to run the rig control portion of Ham Radio Deluxe. HDSDR can control the frequency and mode of HRD. It also supports a free library called Omni-Rig which I haven't tried (yet). So tuning the radio becomes a point and click operation on the programs waterfall display.

Operation

The tuned frequency appears around 23KHz to the left of the centre on the display for reasons mentioned earlier. So on my setup I see about 1/4 of the display below the radio frequency and 3/4 above it. With a 48KHz (vs. my 96Khz) audio interface it would on the extreme left of the display, which I'd find very annoying. Even with the 96KHz audio it is still a bit frustrating that there's not more displayed below the tuned frequency.

On December 28th I used it for the RAC Canada Winter Contest on SSB. It was very effective. Instead of just scanning across the band with the tuning knob I could QSY directly to any signal, judging strength by the intensity of the display. Often I could see who was calling CQ by the regular timing of signals on the waterfall. Fine tuning can be done either with the mouse or the tuning knob. The other thing that works well is using it to find a free spot to call CQ.

99% of my operation has been using the audio from the radio and HDSDR as a tuning aid, but HDSDR can also be used to demodulate the signals, which can then be listened to directly or fed into some type of digital program. I didn't find this necessary but for something like Digital Radio Mondiale where the bandwidth required exceeds the capability of the transceiver it would work fine. I used it a bit for the alignment of frequency offsets in the various modes and you can really notice the delay going through the computer.

Snags

There are some quirks that take some getting used to. The biggest was the effect of changing the filter settings on the K3. On CW for instance the filter centre frequency is 600Hz. Changing this shifts the entire waterfall on HDSDR by the same amount, as the K3 actually changes its local oscillator frequency rather than moving the filter frequency, which makes sense because it uses fixed-frequency crystal filters. So I've found that it is best just not to change the centre frequency of the filters.

One thing that is going to drive me crazy is the radio control. Don't get me wrong it works great, but the big challenge is getting all my favourite software to work with it. As long as I can go through Ham Radio Deluxe or Omni-Rig everything is fine, but not everything works with HRD or Omni-Rig. In particular, I wanted to try the N1MM logger because the HRD logger just doesn't cut it for my style of operating. The N1MM logger wants to control the transceiver directly but it doesn't share. Some hams are using LP-Bridge to allow multiple controllers for the K3 which looks promising but it has prohibitive licence terms (even though it is free) and several additional layers of complexity. It also crashed my computer when I tried it with Ham Radio Deluxe.

In summary

This little project has cost me about $40 so far ($15 was for a cable at the local music store) and I will need to invest another $15 or so in putting it in a case. Naturally it would have cost more if I'd needed to buy a sound card to go with it. For that small investment this is definitely a keeper, but it won't be long before I try the RTL 2832u with an upconverter.

73,
Chris VE3NRT.