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SoftRock v6.0 Software Defined Shortwave Receiver for the 80m/40m Bands

I have bought a SoftRock receiver kit from in the UK. A few days later the nicely packed kit lay on my desk waiting to be assembled. Assembly was no problem except for a blind via hole which took me a little while to locate. Then the board looked somewhat like this:

Since I am curious and I have a nice homebrew vector network analyzer I decided to analyze the frontend filter:

A numerical analysis with APLAC showed that the filter is nicely designed, maybe a bit narrow to cover the 40m band:

Then I disconnected the secondary windings of the transformer and connected the filter to the networkanalyzer:

Looks like simulated, also a bit narrow on the upper side.

Of course, the RX doesn't terminate the filter with 50 Ohms. To see this effect, I measured the transfer function of the filter at T1 terminal 1 with a high impedance probe:

Obviously, due to output mismatch the filter transfer function gets quite a bit distorted. A negative loss here doesn't mean power gain. This only shows the effect of voltage transformation at the high impedance probe. Thru calibration was performed at a 50 Ohms termination.

After so much analysis I wanted to HEAR something. A first test on 80m was quite impressive.

For a second test I replaced the original crystal by a 16 MHz type to be able to receive a DRM transmission on 3.995MHz, wich worked extremely well with never seen before 30dB signal to noise ratio. I used the freeware DREAM which supports IQ signals.

The same input signal on the other sideband looks like this:

The DRM signal is perfectly suppressed by the software image reject  process.


A wonderful piece of technology with wide potential for experiments. Highly recommended!

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