Tuesday, January 27, 2009

My CW genes

If I have even a little talent for CW it's due to my genes. This is my grandfather, George E. Good, who was a telegrapher for the Soo Line Railroad.

I still have my grandpa's bug - a 1917 Vibroplex. I sure wish it was in this photo, but I just can't seem to see it.

I wonder how big a deal it was for grandpa to give me his bug? It would have been around 1976-1977. At first, I thought maybe telegraphy had been long gone by that time, but this post says "and I had just begun as a small boy to recognize Marshfield's call letters of "SF" when the Soo Line pulled out all the Telegraphs in the early 1970's. " I can't help but wonder how big a deal it was for him to give me his bug? It certainly meant a lot to me, and it got a lot of use in my novice/general shack in the late 1970s.

Thanks, Grandpa!

P.S. If any blog viewers can identify the equipment in this photo, I'd love to hear from you.

Blissful silence - Is the noise finally gone?

I don't want to count my chickens before they're hatched, but I haven't experienced the 80/40M noise problem since a few days ago. Maybe it's gone?

Interestingly, the same day that I stopped hearing the noise, I visited my neighbors and checked in with them about any RFI they'd been experiencing (their living room is about 40 feet from my G5RV). I'd operated in the NAQP SSB contest the day before, and they noted that they'd heard some RFI coming out of their subwoofer ("it sort of sounded like Vietnamese").

I explained that I'd been operating using a different transmission mode called single-sideband, and that the sound they'd heard was probably me. I also explained that there were some things they could do to eliminate the problem, especially reducing gthe length of cable going to the subwoofer, using some sort of twisted-pair cabling, and using some special devices (RF chokes) to eliminate the interference. I gave this speech a bit half-heartedly, since they're renting while their house is being renovated, so they'll be moving out in a few weeks anyway.

Now, these are really nice people, and have been great neighbors, so I decided to mention to RFI coming from(I think) their garage - who knows who's going to move in next? And if the noise-generating device is part of the rental, now would be a good time to figure out where it is so I can contact the property owner about fixing the problem.

The reaction was very positive; I was invited to look around, inside and out, and I looked for possible RFI sources. While walking around, I described the problem I was having, the hours I heard the problem (about 1600-2300 local time) and made a point of explaining that I could hardly hear anything on my radio while the noise was happening.

I didn't see anything obvious, so I explained that, if the subwoofer RFI was a problem, I'd solved a similar problem with my son's stereo, and I'd be happy to advise them on a solution, but more likely, it wouldn't be much of a problem before they moved back into their remodeled house.

Now, a week later, I've not heard any significant noise problems on 80 or 40 in the evening hours. Last week, I had a very pleasant experience operating in the CQWW 160 CW contest. And tonight, when I tuned around 160, 80, and 40M, the highest noise level I saw was S4-S5.

It could be a coincidence, but I suspect my talk caused my neighbors to turn off some piece of electronic equipment that was radiating noise. I need to check in again and see if this is the case (and thank them!).

CQWW 160M CW Contest - every day is Field Day at KM6I

This last weekend was the CQWW 160M CW Contest. I was fighting a nasty cold, and wasn't planning on operating, mostly because I had no antenna for 160. However, I started to feel better on Saturday afternoon, so when I had an hour to myself, I measured 132 feet of 18 ga wire, launched a line into my Ginkgo tree, and hauled up an inverted L (well. the shape is more of a "C", but whatever). The highest point is about 40 feet, and the end slopes down to about 10 feet.

After the kids went to bed, I was still mostly awake, so I played for about 2 hours, took a break, and finished with another 45 minute stint. All S&P, I made 80 contacts in 2 3/4 hours (79 after my duh! dupe - thanks AD7AF for being nice, just logging me, and moving on). That's about 29/hour, which is a personal best for me from this QTH. No DX other than a KL7, but it was pretty easy to work stateside, and I even picked up a few new states for WAS.

Monday, January 26, 2009

Frequency-based aural separation for CW


For the last few months, I've been lusting after an Elecraft K3 HF Transceiver. Besides its excellent receiver performance, one of the features that I'm intrigued with is the diversity receive capability. If you add the KRX3 subreceiver module, you get a complete, no-compromises second receiver in the box. The diversity receiver feature allows you link both receivers together so they track the same frequencies, and you can connect different antennas to each receiver; presumably, you'd do this with different antennas with different receive characteristics (you can also run both receivers independently if you want). When a signal fades in one antenna, it might be increasing in strength in the other antenna. For those of you who have 802.11 access points in your house, that's why there are two antennas on the back (I don't think there are two separate receivers in the AP - they probably do some trickery to automatically switch antennas as needed, but you get the point).

That's all very interesting, but what's very cool is that the Elecraft engineers opted to put a very capable DSP unit - the human brain - in this loop, by allowing the user to put the two receivers' outputs into opposite sides of a stereo mix. Although I've never experienced this myself, since I don't (yet) own a K3, I've heard that the signals seem to "float" in the stereo field as they become more or less audible in each antenna/receiver combo. If you want to hear it first hand, listen to the samples on N1EU's web site.

If you're just interested in being able to copy a weak signal, I suppose a mono mix would have been fine. But I'll bet there are some real advantages under crowded band conditions where the human brain is able to use that stereo field separation to "sort out" the desired signal from the undesired ones. Maybe the fact that the desired signal is floating between the operator's ears in a slightly different way than the interfering signal would allow copy with the dual receiver system when it would be impossible with a single receiver.


So that got me thinking (always a dangerous thing). Is there a way to use DSP technology to separate CW signals, without separate receivers, by frequency and spread them out across a stereo field, such that an operator can get better copy than s/he could listening to the signals in a mono mix? In other words, can someone "lock on" to a CW signal better if that signal is separated from interfering signals in the stereo field?

My first thought was "certainly someone else has thought of this." And part of my reason for posting this on my blog is to see if anyone else has. I didn't find anything with the obvious Google searches, but maybe someone can point me to something...

My other thought was "why bother - with modern rigs with good roofing filters and high-quality DSP, you can dial the bandwidth down to 50Hz with no filter ringing." That's a great answer if, say, you're chasing DX and you're interesting in listening to exactly one signal at a time. But in contests, you get called off-frequency. Or, if you're a DX station, and you've got a pileup of 100 stations calling you, you probably don't want them all exactly zero-beat on you (or on your advertised split frequency) - you'd never be able to sort them out. You might be using a filter of 500, 800, or maybe even 1800 KHz to widen the net.

An experiment

I don't have any direct experience with digital signal processing, but in a previous life, I was an orchestral trombonist and also dabbled with computer music applications. One application I was familiar with that would do the job here, and wouldn't require me to learn all about DSP, was an app called PureData, or pd. pd allows you to graphically build sound processing structures, and it is free.

The basic idea is to take a monophonic input signal, and feed it into a parallel set of hi-Q bandpass filters. The output of each filter is then sent to a specific position in the stereo mix. So, for example, any CW signals of 400 Hz might end up all in the left channel, while signals of 500 Hz would end up in the center of the mix, and signals of 600 Hz would end up in the right channel.

I also recall reading that the Elecraft engineers incorporated a bit of delay into their diversity receive feature. Although I had no idea why that was important, I built the capability into my pd model, and as it turns out, it just doesn't work without it. Maybe a blog reader can explain that to me. In order to get things to "spread out" in the stereo mix sufficiently for my ears, I needed to add a delay of 0 to 10 milliseconds to the various bands.

300 Hz - Delay 0 ms - Pan hard left
350 Hz - Delay 1 ms
400 Hz - Delay 2 ms
450 Hz - Delay 3 ms
500 Hz - Delay 4 ms
550 Hz - Delay 5 ms
600 Hz - Delay 6 ms
650 Hz - Delay 7 ms
700 Hz - Delay 8 ms
750 Hz - Delay 9 ms - Pan hard right

So the interesting parameters here are likely:

- The number of bands
- The bandwidth of each band
- The assignment of each band to a position in the mix (do they smoothly transition from low to high = left to right, or does the spectrum "circle around" multiple times with increasing frequency?)
- The amount of delay
- The distribution of delay times (e.g. is each adjacent band close to the delay time of its neighbors, or is it far away from them?)

How's It Sound?

I know by now you're curious what this all sounds like. So here's an example. The audio was recorded on my rig during the recent CQWW 160m DX Contest. It's one minute long, and I had the 500 Hz crystal CW filter turned on. I chose this one minute of audio because there are a few stations fairly well spread out.

Audio Clip - no processing

Audio Clip - stereo separation processing enabled

My Verdict

To be perfectly honest, I'm not sure I can copy the weak stations any better with the processed audio better than the unprocessed audio. I'm curious if you have the same experience.

I do have to say that I think the processed audio is a bit easier to listen to, and I wonder if it might reduce operator fatigue over a long contest weekend.

Further Experimentation

The parameters of this experiment really ought to be played with more, either by me, or someone who has more experience than I do with DSP technology. I don't understand how the delay affects the stereo spread, nor do I know how to measure how well the bandpass filters in pd are actually working.

What do you think? Please share your ideas in the feedback link for this post.

Thanks and 73!


Tuesday, January 13, 2009

80M Inverted-L

The other night I launched a tennis ball into the same tree my 40M vertical is in, and pulled up a 66-foot wire to use as an inverted-L on 80M:

(can't see it? ha!)
I've "repurposed" the feedpoint of my 40-m droopy radial vertical - the 40m vertical element is still in the tree, just not attached, in case I want to switch back.
So the radial field is the same one I used for the 40 vertical - 6 runs of #18 wire buried in the front yard, asymmetrically (tunneling under the street = not recommended).
My initial observation: this thing is great at receiving the local noise generated from my neighbor's garage. For example, on 3530 kHZ:

Noise floor, noise off, G5RV: S2
Noise floor, noise off, inverted-L: S9

Noise floor, noise on, G5RV: S5
Noise floor, noise on, inverted-L: S9+10dB

My guess is that the inverted-L is just a generally better antenna, so it's just doing a better job of picking up signals, including local noise.

The neighbor garage noise sounds like this. It's pretty regular, in that the time between bursts, the duration of the bursts, and the very loud noise at the end of each burst repeat consistently.

It's odd that the G5RV is much closer to the noise source, yet receives about 30-40 dB less signal. One significant difference between the antennas is their polarization. Could polarization account for that much difference? I doubt it... there must be something else at work here.

Update: 01/15/2009: my first QSO on this antenna was DS1REE in Seoul, South Korea, at about 5am local time.

Monday, January 5, 2009


I put in about 9 hours playing in the ARRL RTTY RU this last weekend. It was a lot of fun. The results:

40M: 103 QSOs, 29 states/provinces, 5 countries
20M: 16 QSOs, 7 states/provinces, 1 country

I spent a lot of time at the beginning trying to get my 500 Hz filter in the FT-857D working with RTTY. Although I did get things working during the previous Thursday night's NCCC practice, I just used the standard 2.1 KHz filter. That really, really, didn't work during the RU. Strong signals within the wide passband would cause the AGC to kick in and the signal I was trying to copy would go away. I suppose I could have played around with disabling the AGC and riding the RF gain, but it seemed to make more sense to just use the 500 Hz IF filter.

The problem I had was that the passband of the 500 hz filter seems to be centered around 800 hz (a typical CW sidetone/beat frequency), even if you're in LSB or DIG mode. However, MMTTY sends a default mark tone of 2125 Hz. So the filter wasn't passing the frequencies the demodulator was looking for. I was able to change the mark frequency in MMTTY to 915 hz which was within the narrow passband, and I was able to decode signals with no problem, even with W6YX hammering away a few KHz away.

However, once I made that change, I couldn't work anyone, not even local stations that really should be hearing me. I was definitely putting power to the antenna, and I could hear myself on a portable shortwave receiver, but no QSOs.

I finally reconfigured MMTTY to use the other sound card in my computer for output, so I could listen to it, and I discovered that, although I'd changed the receive mark tone to 915 Hz, MMTTY was still transmitting with a 2125 KHz mark tone (see - my music degree comes in handy from time to time!). No wonder I wasn't making any contacts. No matter what I set the frequency to in the MMTTY preferences, the transmit tone didn't change.

What I didn't realize is that I needed to also set the HAM default setting values (directly below the receive settings) - those set the transmit values. As it turns out, I tried clicking on the NET button during the contest, and that solved my problem, since it locks the transmit frequency to the receive frequency. The names of those functions (HAM, NET) don't make much sense to me, but I'm a RTTY noob.

On the RF side, I continue to be impressed with how well my tree-mounted wire vertical works. Of course, I am only able to compare it to my G5RVjr, but I made a lot of S&P contacts on my first call, and worked some JAs and China with no problem. In terms of performance/cost, I'm happy.

On another note, NCCC member Ed Muns, W0YK went to Aruba and operated P49X for the RTTY RU. Ed made - get this - 3,214 contacts in 24 hours. The mind boggles...

Thursday, January 1, 2009

QSL cards

Call me old-fashioned, but I really love it when I get a QSL card that is unique - maybe the card has some interesting information about the operator, or a picture of the operator/shack, or something about the operator's QTH. My current QSLs are boringly generic. I'd like to do better on my next batch. But what to put on the card? How about the things I appreciate seeing on cards I receive:

A photo of the operator and his/her station:

Information about the area in which the station is located. Although I didn't know it at the time, Halle-Neustadt is a planned community built in East Germany in the 1960s:

Something interesting about the town/city: one of the QSLs I have from the 1970s is from a ham in the town where the Czech composer Bedrich Smetana was born (Smetana wrote "The Moldau" and "The Bartered Bride" among other works):

And then, there are the low-budget QSLs which have a sort of endearing quality:

This one is kind of interesting - it's a Hollerith card! I haven't checked if the punched data has anything to do with my QSO - I suspect it does, since the printed labels appear to have been computer-generated. This is pretty impressive, as the QSO was made in June 1977!

Which bands first?

Sitting down and thinking about my planned contest efforts, I realized that it's probably going to be to my advantage to first concentrate on building antennas for 40 and 80 meters. Since in most contests I'll be operating in the evenings/early mornings, after the kids are in bed, effort spent on antennas for 20/15/10 meters will be largely wasted except in contests I'm focusing on and have pre-arranged for daylight operating time.

Given that, it seems like I would benefit from a set of antennas that offer both reasonable low-angle radiation and NVIS performance (for close-in stations). If I can somehow fit a 40/80 meter vertical, along with a low dipole for those same bands, that seems like an effective set of antennas for contesting in the hours of interest.