Monday, May 18, 2009

First QSOs - 10W low power test, 30W SSB

With the R8 finally operational and connected to my IC-7800, it was time to properly commission the 7800 and start to open the envelope of the radio-antenna combination, not to mention time to start getting to know this monster rig.

The MFJ 259B analysis demonstrated that the antenna was basically functioning on all bands (despite the non-optimality of 10m), but it's another thing to see what it will do bringing in signals and usefully radiating the power fed to it. For reasons of curiosity, low-power requirements and relative simplicity w.r.t. radio configuration, I decided to try my hand at a PSK31 QSO to christen the HF station.

The 7800 has an RTTY and PSK31 terminal built right into its operating software, so there's no need to set up any esoteric computer connections, nor install/learn any other software. While the 7800 software environment for these purposes is quite simple by the standards of the latest PSK/digital mode software, it certainly covers the basics. Beyond straightforward typed transmission and reception on a given centre frequency, the radio software adds a simple 8-message memory facility. It also takes advantage of being tightly integrated in the radio by adding frequency lock-on features for RX and TX (known as AFC and NET modes, respectively). Presumably the integration must also extend to nicely tuned modulation, for a clean PSK signal - something that would otherwise need to be configured to achieve the proper modulation drive from an external AFSK audio signal.

Before setting out for a QSO, I edited the 7800's 8 message buffers to serve roughly for CQ, end of over, brag and signoff messages. A lot of PSK31 computer software seems to support message macros, complete with substitution for the other station's call, operator name etc. The 7800 does not have such a facility, presumably partly because without a mouse interface, the operator workload would be too great to set values for these elements in mid-QSO (most software simply has you click on pertinent pieces of received text to set these). Nevertheless some automated messages are useful, and you get to program the keyboard's F1 through F8 keys accordingly.

Having done basic prep, I hit the 20m waterfall, and found a little space for my CQ call. After only 2 automated CQ calls, I managed to 'scare up' a Minnesota station, KX0O, who I worked for a very brief QSO (I was interrupted by the XYL, so had to cut it short!). Still, the signal reports were 599 in each direction and I had my first BPSK31 contact under my belt!
All in all, my first experience of working PSK 21 was very pleasant. Using the mode is a quite a visual experience - the bandwidth being small enough to allow you to easily scan over many ongoing calls/QSOs and quickly move potentially interesting signals into the waterfall passband to investigate them. As mentioned, the 7800 has an excellent features (AFC and NET) to snap to the nearest strong signals, and holding down the appropriate function key, fully tunes the radio to the signal centre for the best possible copy. Working PSK31 for the first time unsurprisingly required more thinking about procedure than I'm sure it takes with practice, and I had to refamiliarise myself with some CW abbreviations to boot. In the heat of the 'battle' one is (overly) conscious about pauses, and because the radio is also new, I did not use the pre-programmed messages at all aside from the CQ call in this first QSO, nor any subsequent ones so far. No doubt, I will experiment with these over time and get them configured exactly how I want them - including some partial messages that require manual entry of the other stations details with the automated parts.

With some early PSK success, I increased the power a little to 20W and worked some other stations. At this power, my computer speaker system noticeably reproduced the "thrum thrum" of the PSK waveform - suggesting either poor electromagnetic immunity in its amplifier, or transmission along the mains. At this point the 7800 case is not separately earthed, so this seems like a good thing to try. PSK of course drives the transmitter at essentially 100%, so the effect is likely to be more noticeable than equivalent power 'average' SSB.

Finally, I decided to try my hand at 20m SSB with about 30W of power dialled in. The band was pretty noisy, but a number of stations were audible coming in from about a 1200 mile radius SSE to SE, from the US. Using the 7800's spectrum scope, I found a station calling CQ, and managed to work K6AER very successfully for a very pleasant 40 minute QSO, with a good report (he was coming in at 599+20dbs!). The computer speaker system seemed quiet while operating SSB (and I had compression off, so average power would be way down from 30W).

All in all, a very pleasant Victoria Day long weekend of playing radio and finally getting to play with (and learn) some of the 7800's features - including use of passband filters, notch filter and Noise Reducer, all of which worked amazingly well. The Digital Selector feature remains a bit of a mystery and will need some more experimentation to find when it can help pull a signal out of noise (I couldn't make it seem to improve matters, but that might be because it is mutually exclusive with the preamplifier).

As well as messing around with the radio, I got set up with eQSL ready to work the world!

My new Ham 'career' is shaping up nicely :-)

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