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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  2 comments for “QRP kits: Audio response

  1. August 22, 2011 at 10:47 pm

    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.

    • August 23, 2011 at 6:02 am

      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.

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