Softrock Lite II for 500kHz and 136kHz

Your intrepid, no expenses spared blogger wanted to try an SDR on 500kHz. Being a big spender and having some PayPal bonus vouchers to redeem I splashed out and purchased a Softrock Lite II 80m Kit, it cost me £4 that !!

Jim Moritz published the details for converting the old Sotfrock Lite to 500kHz and 1softrock-lf36kHz, there is not a lot of difference so I reckon that it should be OK.

 

The main difference is the lack of divide by 8 so a 2MHz Xtal will be needed for 500kHz, as for 136kHz we must experiment.

First step for me was to build and test on 80m, my other SDR is 40m TX/RX so 80m would be a nice band to keep available. Hmm, I suppose I could spend another £4.

srockii-view

I must say it performs very nicely on 80m although FULL band coverage still needs one more Xtal than the 4 I have.

srockii-btm

Well I spent the other PayPal voucher on a 9m glass fibre pole so I followed my original idea of making the Softrock Lite II 80m easily changeable to 500k and 136k.

First of course we need changeable, plug in Xtals, no problem. The Oscillator/Buffer has a bias change for the lower frequencies, 2 resistors need to be removed and another added. I mounted those on spigots for ease of removal. The other changes in this department are added capacitance, this can be added to the rear of the board.

 

The front end is the other change, we must built an LPF which will be too large for the board so this will be separate, this feeds the input transformer which must replace the 80m component.
To achieve this easily I have provided tabs to mount L1 and T1 for ease of swapping.

srockii-filter

It won’t be a luxury band switch job but at least it’s not butchery. Now I need to find a source of 75 material toroid cores.

srockii-xtal

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4 thoughts on “Softrock Lite II for 500kHz and 136kHz

  1. What! you deserted it and put your faith in satellites just wait till there’s a darned good solar flare, them ships will be bumping into each other.

    Seriously I read a BBC report recently, cheap GPS jammers available on e-bay made ships on the English South Coast think they were in Cyprus. A professor did a test from the coast at Gravesend.
    Bring back Loran, I knew we would miss it on Top Band when it went.

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  2. I don’t believe there are any ships.
    I put my name down for a captain’s job and haven’t heard a thing.

    You know the most popular car on the market at the moment? Its the Morris 1000. I’ve had my order in for 30 years and I’m still waiting.

    I still think the RN has the best navigation system, they use terrestrial TV signals to guide them around the coast.
    It only gets worse…..
    M

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