This is easy to understand with some simple arithmetic (which I think most hams already know, but is worth repeating):
- SNR (signal-to-noise ratio) is proportional to receiver bandwidth, provided that the signal is totally contained within the filter bandpass. Typical SSB transmit bandwidth is 2.4 kHz and CW bandwidth is < 10 Hz. However we rarely if ever use extremely narrow filters in our receivers. We can say, roughly, that the typical ratio of filter bandwidth (in actual use) between SSB and CW is 10. That is, for the same transmitter power the SNR of an SSB signal is -10 db in comparison to CW.
- QRM is another type of noise that affects SSB and CW differently since the activity levels and spectrum are different. In the context of a contest, which can be viewed as a worst-case scenario, we can estimate the number of stations to be twice (2x) the participants in a CW contest. However more spectrum is available (and used) for SSB, being about 2x on 20 meters, 3x on 15 meters and 4x on 10 meters. On 40, 80 and 160 the spectrum is roughly equal.
Try both CW and SSB contests with QRP and you will, like me, discover how true this is. My score in CQ WPX SSB is a great example: 454 QSOs during 18 hours of operation (20.5 hours per rules criteria), despite superb conditions on all bands. The QRM was so fierce that most stations with S9+ signals either could not hear me at all or struggled in the attempt to pull me through. The worst band was 40 meters with just 24 QSOs, only one of those from outside North America.
Let me backtrack a few days to discuss my preparation for the contest. This might seem easy enough since all that's involved is a transceiver, a microphone and a computer. My difficulty was the microphone. There were two particular challenges: compatibility with the KX3 transceiver, and quality.
Elecraft sells a handheld mic for the KX3 that reportedly works well, but that is not an option since a handheld mic is out of the question for contests; you need both hands for typing, tuning and other station operation. When I first got back on the air with the KX3 at the beginning of 2013 I used an inexpensive but reasonably good headset that I had purchased for Skype use (on the left in the above picture). It is comfortable and both microphone and headphones audio quality is not too bad. Importantly, its 3.5 mm stereo connectors are a perfect fit to the KX3.
When my SSB success didn't go so well with my QRP power I flipped the mic out of the way and only used the headphones. That is, until the foam covers over the earpieces shredded. So much for the economy PC headset. In any case the microphone worked poorly with the KX3, being unable to achieve full modulation. There was a compatibility problem, perhaps with the rig-supplied bias via the stereo connector. Fiddling with the KX3 microphone setup options didn't help. More on this below.
I next bought inexpensive headphones designed for use with portable entertainment devices (middle item above). They are lightweight and were passably effective. Since I had decided to forgo QRP SSB I could get by without a microphone.
One major problem with this unit is sensitivity, with the minimum audio gain setting already loud enough for general use. Turning the gain higher was a problem since (as with all modern digital level controls) each succeeding discrete step was too large. There were only about 4 usable settings of the AF Gain control, and no ability for fine tuning. Another problem was audio quality, which is surprising considering its intended use for music. Listening fatigue can set in after a few hours of use on a noisy band.
One last problem is the solid plastic cover over the foam pads. This is good to block ambient sound but bad for comfort. That matters in a contest. Plastic foam is better. (Of course poor quality foam on cheap headsets isn't good, as we have seen.) You can always close the shack door if there's noise from the household. That will also make your transmit audio cleaner since compressors amplify background sound.
Since I needed a headset with a microphone I decided to reach back into relative antiquity. I resurrected my decades-old Heil headset (on the right of the picture). I had no idea how it might fare after over 20 years of storage. My recollection was that it had worked very well for both receive and transmit. The reason I did not press it into service earlier was the connectors: ¼" phones (stereo) and Yaesu 8-pin mic. Since I was considering refurbishing the FT-102 I was saving it for that rig.
With WPX only one day away and no other option in sight I took the plunge and replaced the connectors. As I cut off the old connectors it felt as if I was also cutting off a piece of my past. After, with new connectors attached and tested, I plugged it into the KX3 and had a listen. It was marvelous. Receive audio quality was suddenly crystal clear, much better than either of the other headphones. Sensitivity was just about right, too. It was a joy to tune across the bands. It goes to show that quality does matter, so you should take some care in choosing what you slip on over your ears.
The microphone was a greater challenge. Elecraft had made a KX3 design decision to not support low-output microphones such as dynamics and even some bias-driven PC-compatible mics. In their defense the KX3 was intended for mobile use where a purpose-built handheld mic is most often the correct choice. So that's what they did. As it turns out the KX3 is widely used as a primary home rig, and their owners (like me) prefer to use their existing mics.
One thing I've come to really like about Elecraft is that they do listen to their customers. Plus, there is a lot of flexibility designed into their rigs that can be manipulated with firmware updates. In late 2013 they succumbed and updated the firmware, although they seemed reluctant to do so and continued to flog their own microphone even in the update notice.
This gave me confidence I could adjust the KX3 to support my ancient Heil headset. Here are the steps I went through. Much of it is standard on any SSB rig:
- I first had to configure the "3rd pin" for PTT, mic bias or nothing. I thought about this for a moment until I remembered that the mic predates PC sound cards. It has a dynamic element. I set the pin to "nothing".
- The Heil mic element does not have a flat frequency response. It has an emphasized mid-range that is customized for DXers and contesters. The KX3 has a default mic equalization that boosts the mid-range. I therefore adjusted the KX3 mid-range equalization to flat (+0 db).
- I switched in a dummy load for the transmitter adjustments. Increase the mic gain until the ALC starts kicking when speaking as you would during a contest or in a pile-up (this usually is not a normal speaking voice). Turn on speech compression and increase it until there is a noticable effect but not more than 10 db of compression on voice peaks.
- I did not have time to wire in a foot switch so I was stuck with using VOX. This meant adjusting the VOX controls. I have a long-standing aversion to VOX since I have never found a combination of settings that I like. For contests it is important to set the VOX delay as short as possible or you'll often miss the first part of the other station's exchange. Contesters have fast reaction times and speak quickly, often responding while you're still talking! You can increase the delay for non-contest use.
I picked 17 meters since there are many casual SSB operators to be found there. The first station I ran across that appeared ready to start a new QSO had a British accent. He told the station he was talking to that he was checking to see if the band was open. It was TX6G (Austral I.). No pile-up yet and not spotted on the DX cluster. Thirty seconds later he was in the log. But I didn't ask for an audio report. I was just happy to work him on SSB with 10 watts and a dipole. I then went to 15 meters and did solicit reports from a couple of contesters warming up before 0000Z. My audio was fine.
A couple of hours later the contest started and gave it my best shot. The QRM was fierce and almost no one could hear me. If adversity builds character I became a better person by Sunday evening. In addition to the QRP SSB challenges I mentioned earlier there are others.
- Splatter: It isn't easy to overdrive the modern generation of transmitters, though many seemed to be trying. Those using amplifiers had an easier time achieving this dubious objective. Unless the ALC is compatible and integrated with the exciter it is often easy to overdrive the amp (flat top) and cause splatter. It made for a higher basement noise level on the bands, and thus harder for me to be heard.
- Compression: For some there is no such thing as too much compression. They assume that if there is a legibility problem it's the other guy's problem, not theirs. That it slowed them down and caused many instances of miscopied exchanges (which I witnessed many times) seemingly was of no importance.
- Accents: Compression or not, the diversity of accents for non-English speakers speaking English often made copy difficult, in both directions. That doesn't happen on CW.
- Sloppiness: Let's face it, in every QSO my signal was difficult to copy. Many operators didn't let that delay them. They simply logged whatever they imagined my exchange was just so they could move on and work the next station. They will be penalized during log checking. It is better to say "sorry, no QSO, try again later" as good operators did. That works out better for both of us.
On a lighter note there are some broader benefits to venturing into SSB contests with QRP:
- We fill a psychological need on the other side of the QSO. The DX station who pulls through the weak station feels great satisfaction for having provided a needed QSO to the "little guys".
- If you have sadistic tendencies this is a safe outlet for your darker moods. Think of the pain you're causing to others as they sweat and suffer to pull you through. Focus on Sunday afternoons when the big guns have worked out the band and there are only stations like yours calling them, and they desperately need the points you represent. You can prolong the pain if the QSO is proceeding too smoothly by dialling the power back to 1 watt or less.
- Be proud that you are promoting the state of the art. One of the reasons hams build super-stations with high towers, large antennas, low-noise receiving antennas and superior, feature-rich receivers is so they can work you! This not only spurs innovation, it keeps the amateur radio economy healthy.