New Technology for 2020 ~ The Homebrew DDC SDR Transceiver

Yes! That is what I said.

"A Homebrew DDC SDR Transceiver"

June 13th, 2020 ~ I have had a response to my inquiry.

Yes indeed there are readers of this blog who are "doing the DDC" thing and I even have some recommendations on different LTC ADC's (perhaps less expensive). 

I will share that model number and a spec sheet later today. This could get really interesting.

The Model # is the LTC2291 @ about $28 from Digi-Key. Still not under $10.

No Op-Amps, Precision Capacitors or Resistors will be involved with this project.

Pete N6QW


Last evening I had an opportunity via Zoom to share some of my homebrew projects with the Cedar Valley ARC located in Cedar Rapids Iowa. What a great bunch of hams -- many are former and current Collins Radio Employees (now a unit of Raytheon).

I was asked quite a few questions: but a couple members pointed a finger at me asking why I was using the front end analog hardware in the three SDR transceivers I built. The burning question how come you are not using DDC? My response was a sort of mumbled, well you really need a board for that as most of the devices are the 48 pin square (looks like SMD) device. So that got me thinking: Pete why aren't you doing that?

A little research turned up a candidate device from Analog Devices (actually Linear Technology a subsidiary --you know the LT Spice guys) called the LT2165. It is a UHF capable ADC and has some interesting specifications ( a lot that escape me). It also has a hefty $82 price tag. No wonder they get $6K for a FLEX6700.

Anyway this posting today is to inquire if anyone is working on a DDC SDR transceiver and secondly about the device itself (anything faster, better, cheaper as a candidate)?

It appears you have a choice of all sorts of outputs and so then the next big question is how you convert those outputs to something useable like modes, waterfalls, spectrum display, band changing etc.

So this may be the latest project for me. I foresee this as much more fruitful and productive effort versus trying to get opposite sideband suppression out of a mystical 6 pole op-amp phase shift network that even when the planets are aligned is maybe 45 dB. 

Stay tuned to this space for the next great adventure.

Pete N6QW

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