QRP kits: Audio response
Many people who’ve used an ATS-3 mention the receiver characteristics of this amazing little riglet. The typical refrain is “signals seem to just pop out as I tune the rig”.
That certainly is the case and it is an amazing characteristic, especially given its size. To a lesser extent the same can be said for Wilderness Radio’s SST.
More years ago than it seems, the ARRL made a posting to QRP-L asking if any QRPers would be willing to send their kit-built rigs to their lab so that measurements could be made and reviewed in an upcoming article in QST. You can read/download that article here as a pdf file.
But back to the ATS-3…
A few weeks ago I used Spectran and a signal generator to measure the audio response (for a given change in RF input) of my K3 and figured, as long as I have everything set up for that, why not measure the other QRP rigs I have to see how they compare.
I’m paying more attention to steepness of the skirts rather than overall bandwidth:
Click for larger
As expected, the results agreed with what I hear as I use these rigs – there were no surprises. But it is interesting to note the similarities of this specific characteristic between the tiny little ATS-3A with Elecraft’s flagship.
The results of the other rigs measure can be seen here. I’ll eventually add the KX1…currently awaiting the arrival of a small part to repair its DC connection.
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Themocracy
John – I’m quite surprised by the narrow bandwidth of the SST. While that kind of filter response might be great during contesting, wouldn’t it be a bit narrow under regular conditions? I’ve had people call me several hundred hertz away from my frequency. I’m wondering what your take is on that.
Yes, it is narrow for general operating and is more appropriate for contesting – an endeavor this rig wasn’t designed for. My guess is that a pre-Elecraft N6KR was using those kits he designed back then (Norcal 40, SST, Sierra, etc) as learning platforms for himself as a designer as well as offerings to the QRP community that would not otherwise have been available.