The Radio Gods seem to be steering us toward Double Sideband. A few days ago I got an e-mail from Alain F4IET. We had him on the SolderSmoke blog two years ago, talking about his French backyard pandemic Field Day. His recent e-mail reminded me of his very fine homebrew DSB transmitter, which is his only rig and with which he has worked the world.
The rig is named for the fellow -- Robert F6EUZ -- who is Alain's teacher from the local radio club.
Alain's rig was shown to the world in the G-QRP club's Winter 2020 issue of SPRAT (SPRAT 185). Once again, let me note: If you are not subscribing to SPRAT, you are just WRONG. Join G-QRP and start receiving SPRAT: http://www.gqrp.com/join.htm
Alain gives some nice shout-outs to Pete N6QW, Charlie ZL2CTM, and Basanta VU2NIL, all of whom provided advice and counsel on this project. So think about it: the Master Robert rig was built in France under the guidance of a French Elmer, with advice from hams in the U.S., New Zealand, and India, and was featured in journal of the British QRP club. That, my friends is the International Brotherhood at its best.
As I read about Alain's rig, I found myself thinking about the Direct Conversion receiver projects underway around the world. The Vienna Wireless Society's Maker Group, is, for example, building a simple DC receiver. It would be relatively easy to pair up a rig like the Master Robert with a DC receiver (the VFO could be the only stage common to both transmit and receive) to make a simple phone transceiver. That kind of rig was my first phone transceiver. Alain reports that he is currently working on a second version of the Master Robert. It will be a transmitter-receiver (TRX) and will be used in SOTA operations.
Alain's description of his transmitter is a lot of fun: http://www.f4iet.fr/mdwiki/#!master_robert.md
I especially liked his comment about how the other phone stations never knew he was on DSB: http://www.f4iet.fr/mdwiki/#!dsb.md I had similar experiences out in the Azores with my DSB rigs.
Here is Alain's main page: http://www.f4iet.fr/mdwiki/#!index.md
Alain's QRZ.com page: https://www.qrz.com/db/F4IET
Here is the Master Robert schematic from GQRP: http://www.gqrp.com/Maestro_Robert_Cct.pdf
Here is a link to the 76 DSB posts on the SolderSmoke blog (keep scrolling down!):
And the DDS VFO from Leon @ ozQRP ... another talented member of the prestigious IBEW.
ReplyDeleteHi Bill - Alain's Double Sideband Rig looks like another fine project. And yes, Direct Conversion is in the air. I don't want Pete to take the blame for my shortcomings, so you should know that the VWS Direct Conversion rig is actually not an N6QW design - although all DCRs share a simple architecture - mix RF to audio and amplify! The VWS DCR was designed by me and Mike, KD4MM. It is a bit of a "stone soup" design - a little from here, a little from there. We paid particular attention to the audio stage where nearly all of the gain is. Mike and I designed an audio LPF using Elsie. We borrowed the audio low noise amplifier from the EMRFD High Performance DCR, but we added gain control to both the LNA and final LM-386. The mixer stage is a homebrew diode ring double balanced mixer. The BPF(s) are link coupled double tuned circuits designed by me using the guidelines in SSDRA. The RF amplifier is another W7ZOI, Wes Hayward design from SSDRA. The VFO is an Arduino / SI-5351 which borrows heavily from many sources but was written by me, and at least one of our members is working on a PTO for the VFO. We've focused on helping the Makers understand and characterize all of the stages, and I have learned a bunch in the process. We've tuned the stages for what we think is the best audio with good rejection of nearby signals. It sounds great and is fun to listen to. With various screw-in BPFs I've put it on 80, 40, 20, and 17. The whole project is documented on the VWS Maker groups google drive - the link is here: https://drive.google.com/drive/folders/1J2lQS1M0BfoU7Bc22d--1-LscD0VSU6x?usp=sharing
ReplyDelete73 and happy 4th,
Dean
KK4DAS
Thanks Dean. Pete has designed so much, I naturally find myself attributing all new rigs to him. As you say, the structure is the same for most DC receivers. 73 Bill
ReplyDelete