UPDATE on today's earlier blog about the Sotabeams filter

Ok, so I just built the filter into a custom enclosure.  Here is what it looks like:

The box has 3 LED indicators and a control knob.  Below is what it looks like inside:

A mass of spaghetti, but all that being said, how well does it work.  Here are my impressions:

1. The audio output with the existing on-board audio amplifier is fairly meek, and almost unusable without external amplification.
2. The external amplifiers that I tried both picked up some noise which I have not determined the source yet.
3. The audio sounds a little hollow, but it isn't a brand new $1000 receiver.
4. With all that being said, the bandwidth filter and the center frequency function as described.  It is a pretty cool little device.

In summary, I really don't see how this is going to help someone working QRP.  Chances are you are going to hear whoever you are working quite well without any filtering.  On the other hand, if you use this filter in a LP or HP situation, then the benefits of being able to control the bandpass is going to have some bang for the buck.  In my 3 quick QSO's on 40m CW,  I was able to reduce the bandwidth in small steps and the received signal was more pleasing to the ear.  The Center Frequency feature definitely moves the hi and low cut quite adequately.  For some reason the direction of the knob feels backwards, but that might have been a wiring error on my part..but I don't think so.

I noticed that one of the chips on the board seemed to run a bit hot, but probably within acceptable limits.

Would I recommend it?  A definite maybe.  If you operate in crowded band conditions, then it could be a real help.  For every day QSOs it might not be necessary and you may not bother to hook it up unless you have a cacophony of signals coming at you on a regular basis.

It was not completely easy to get everything into the small box...mostly that is due to wiring it up.  I would probably build it differently if I do it again...for example, I would want everything mounted on one side of the enclosure to avoid wiring from both top and bottom.

If you decide to build one, let me know how it turns out.  You will need an external audio amplifier to give you more audible output.

73 Mark 4x1ks