Solid State Radios

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An Improved Superhet for WRMI reception

This, hopefully, will be a "new and improved" version of the simple superhet for reception of WRMI that was previously shown here.

Improvements will include wider range frequency coverage, better image rejection, and improved selectivity, achieved principally by changing from a single down conversion to an intermediate freque3ncy of 455 KHz, to a dual conversion up converting to 10.7 MHz as the first intermediate frequency.

With the use of a simple low pass filter as the front end, reception from the broadcast band to seven MHz or so should be readily accomplished. Images will be in the range above 22 Mhz so unlikely to present any issues, and a crystal filter at 10.7 Mhz will establish the initial selectivity ahead of the second IF.

Construction has begun. The Front end filter, mixer, and second conversion local oscillator are complete.

A TDA1072 again is used as the main device of the…

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w5jag

6 days ago

Some more work - the back end is mostly done; I removed most of the leaded components that were bugging me and kept only those that were needed to skywire across the board. The advantage of this is that SMD parts can still be placed underneath the skywired part, and that occurs in several instances here.

While the front end is mostly 0805, the back end around the TDA1072 is mostly 0603 for no particular reason other than that I could. The 0603 helps get more parts under a skywired component, but otherwise really doesn't save any space on this type of board.

It has been tested and is functional. Not necessarily optimized yet, but all circuit blocks appear to be working nominally.

I am not yet decided on what type of VFO / Display I will use, and where to place the audio amplifier that still needs to be built.

At some point, I will make a complete schematic for the RF board, but the TDA1072 is basically the data sheet.

Win W5JAG

June 30, 2025

A pocket size pulse counting FM radio

Some years ago I designed a descrete FM radio which at the time I sold as a kit, which gave a respectable performance and thought it would make an interesting post.

In the next post I will give all the details of the original kit.

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w5jag

February 24, 2025

another KT0936 DSP radio -

Props to Larry for introducing this chip - I had not heard of it before.

The performance is considerably better than I had expected.

A couple of clips are attached - one a local FM station, the other WRMI Miami - with a clip lead for an antenna .....

The headphone output is driving the simple vacuum tube amplifier described in another thread here on the Radioboard.

I'll fill in some of the details on my build in some subsequent posts.

73,

136 Views

LarryDee

Sep 29, 2025

W5jag< I wanted to let you know personally that Wix, the platform we use for RadioBoard, is phasing out the old Forum feature. Starting October 15, 2025, no new posts can be added there, and on March 1, 2026, the Forum will be gone completely.

The good news is that all of our discussions, posts, and members will move over to Wix Groups, so nothing will be lost — it’ll just look a little different. I’ll make sure the transition is smooth and will share updates along the way.

Thanks for being such an important part of the RadioBoard community — I really appreciate your contributions!

Best,Larry