XPost: rec.radio.amateur.moderated
amateur radio - Hackaday
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Boat Anchor Twins Get a Little Digital Help Staying on Frequency
Posted: 11 Mar 2022 08:00 AM PST
https://hackaday.com/2022/03/11/boat-anchor-twins-get-a-little-digital-help-staying-on-frequency/
In the ham radio trade, gear such as the old Drake units [Dr. Scott M.
Baker] has in his radio shack are often referred to as boat anchors. It
refers to big, heavy radios that were perhaps a bit overengineered compared
to the state of the art at the time they were designed, and its actually a shame that the name has taken on something of a pejorative connotation,
since some of this gear is rock solid half a century or more after it was built.
But older gear is often harder to use, at least compared to the newer
radios with microcontrollers and more stable oscillators inside. To make
his 1970s-era Drake Twins setup of separate but linked receiver and
transmitter a little more fun to use, [Scott] came up with this neat
Raspberry Pi-based DDS-VFO project to keep his boat anchors afloat.
Compared to the original mechanically tuned variable frequency oscillator
in the Drake receiver, the direct-digital synthesis method promises more stability, meaning less knob-nudging to stay on frequency.
The hardware used for the DDS-VFO is actually pretty simple just a
Raspberry Pi Zero W driving an AD9850-based signal-generator module.
Sending the signal to the Twins was another matter. That was done by
tapping into the injection cable linking both units, which meant a few
circuit complications to deal with signal attenuation. [Scott] also added amenities like a digital frequency display, optical encoder with
crank-style knob to change frequency, and a host of Cherry MX keyswitches
for quick access to different features.
From the look of the video below, the Twins are now rock-solid and a lot easier to use. This project is loosely based on a recent panadapter project [Scott] undertook for the receiver side of the Twins.
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