Notes from the Shack - ARRL June VHF Contest

June is a great time for 6m, with Sporadic E openings occurring from time to time. So far this year, despite spending a good deal of time listening - or in the case of JT65 mode, watching, I've had very few contacts. Getting Guadeloupe, a new country for me on 6, out of the blue was a nice surprise though. New countries don't come too often for me on 6, and this one was my fifth, although one of them has not confirmed yet.

This being my first VHF contest, I didn't know what to expect. I was hoping that there'd be plenty of stations to choose from, although my home-made loop antenna at 20' isn't exactly world class. Before the contest I decided to resurrect my Softrock IF Lite SDR receiver to drive a spectrogram - or panadaptor if you prefer that term. This goes into a newly acquired 192KHz bandwidth USB audio interface for display using the SDR Sharp software. The Softrock is now in a project box purchased at Dayton, with a 1/4" stereo phone plug for the audio interface, a BNC connector for the IF cable, Power Poles for the 13.8 VDC input and a power switch. The receiver draws very little current but now that the station has battery backup it's best to eliminate even small current drains.

Initially, SDR Sharp showed many spikes in the signal of up to about 25db, and also a hump of about 25db for 3KHz on either side of DC. Neither of these are desirable. A clip-on ferrite on the cable between the receiver and the audio interface reduced the spikes to less than 10db which is a lot better, but the DC hump was still there when the contest started. That will have to be investigated another day, and hopefully it will be solved in time for Field Day. Even with these limitations, though, the spectrum display proved to be very useful in the contest.



The above photo is before the choke was installed. Below is how it looks after installation. As you can see it made quite a difference.



Only one contact was made on Friday evening, which was with John VA3JI, at a distance of about 10km. I heard C6AT in the Bahamas as well, and he copied part of my call before fading away forever. That was the only Sporadic E activity heard the entire weekend.

In the end, there were 5 Canadian stations and 3 US stations in the log, all but one using CW, including Mike VE3FGU up in Keswick. The 3 US stations were all in New York, which surprisingly is a new state for me, most likely courtesy of tropospheric scatter. One of the New York stations was in my own grid square, and all the Canadians were there or in FN04, but the other two New York State stations were new. So in total my log showed 8 stations worked with 4 multipliers for a whopping 32 points. The great thing about a low score is that I have a very good chance of beating it next year!

VE3UBL/B, our local 6m beacon, was a constant companion on the spectrogram. The morse code could be read directly from the display. All the contacts were found using it. I found it to be about as sensitive as my ears, but searching the band was way faster visually. The next thing I need to work on after getting rid of the hump is calibration of the display against the K3 so I can read the frequency directly instead of just having a relative indication. At $25 for the kit and $10 or so for parts to mount it is a much less expensive option that the $1,500 or so for the Elecraft P3 (yes, it's cheaper than that, but with US dollars, shipping, HST and the fact that I'd be compelled to buy the external monitor option, it would be about $1,500 by the time it was installed in the shack, plus another $200 for a dedicated monitor).

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%.

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.