Friday, March 18, 2011

First contact

It was a fine afternoon and I needed some exercise so I took the VX-8GR and the Albrecht 10/12m handheld and went for a stroll over Watch Hill. I put out a call on the 2m FM calling frequency and was answered by Jim, G3XPD, a few miles away. I asked if he could QSY to 28.500MHz SSB and he said he could, so I was able to make my first contact with the new radio.

When I first heard Jim call on 10m his audio was clear but very weak. This was puzzling when he told me he was hearing me quite well and was running 100W to my 4W. Eventually I realized this was due to the RF gain setting of the Albrecht. It is accessed via a few button presses, effectively on a menu, so I had left it as it was set by default. This clearly made the gain very low. After winding it up to maximum (see, I'm turning into a CBer!) Jim's modulation was rattling the loudspeaker. No shortage of gain there, for sure.

The receive audio was very clear. Jim commented on some wind noise on my transmissions, which I was able to tame by changing position so the internal microphone was shielded by my head. I didn't ask if he could hear any FM on my SSB modulation and he didn't mention it. That's good, as it suggests the problem isn't noticeable enough to prevent making contacts and there is no urgency to try the modification that is supposed to cure it.

The main problem would seem to be tuning the radio on SSB. The Albrecht AE2990AFS is basically a CB radio designed to work on fixed 10kHz channels, even though it does have dedicated ham band modes. The tuning steps of the radio are 10kHz just like a CB radio. You can press a couple of buttons and select 500Hz steps but you can't tune the band this way. You can tune in 500Hz increments up to just before the next 10kHz multiple then the VFO rolls back to where you started.

There is a clarifier or RIT control which is designed to tune in stations that are slightly off the 10kHz channel. It's range is something like +/- 5kHz so it is quite touchy. There is no centre detent to mark the off position. What this all means is it's quite hard to tune the band looking for signals and if you do tune someone in the chances are you'll call them off-frequency.

A better solution, in my opinion, would be to dispense with RIT and make the clarifier change both the transmit and receive frequency. But if it was possible to do that one wonders why the manufacturer didn't. I imagine that the control works by pulling an oscillator using a varicap diode so there is a risk of making the FM problem worse under the varying load conditions of SSB transmission. But if it could be done without affecting the transmitter frequency stability that would be a mod worth doing.

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