At my second house, I have no way of listening to CW or SSB, unless I hook up my homebrew 20 meter SSB transceiver, or my FT-817 transceiver, so I’m thinking I might try to build a simple communications receiver to solve this perceived problem.
My first receiver build was a direct conversion (DC) receiver, that did not work very well, but motivated me to learn how to build better superheterodynes. I’ve attached a copy of the magazine article for that first receiver. So, I’m thinking I might have a try at another DC receiver. These seem to be the new state of the art as SDR receivers.
As with the general coverage broadcast receiver, commercial off the shelf parts will be used if there is an advantage to do so, and the cost is reasonable. My goal will be realized with a simple kitchen table receiver that works well for its intended purpose and can be used on a daily basis. A secondary goal is to make it a true kitchen table receiver, by doing all construction at my second house on the kitchen table, with no resort to any of the tools / equipment in my ham shack. A multi band receiver would be nice, but probably is not essential, at least at first.
I have an extra working QRP Labs VFO left over from the development of my 20 meter SSB transceiver, so it will probably be used for frequency synthesis, at least in the early stages of development, if not permanently.
This will be an experiment / work in progress sort of thing, sharing time with a couple of other projects I want to do. My simple SSB transceiver took three years to satisfactorily complete, and the simple general coverage broadcast receiver took another year after that, so those are the sort of time frames I operate in when tinkering / experimenting with stuff.
73,
Win W5JAG
I think this is the keeper VFO configuration.
Installed here is a "0-55 MHz DDS VFO" as widely advertised on eBay and AliExpress for very reasonable prices.
They are built around an Analog Devices DDS chip, so the output is considerably cleaner than the Si5351 devices. The clean output, and programmable offsets, will make construction of a companion transmitter, if I decide to go there, considerably easier.
Output is slightly more than the Si5351 devices, being about +10 dBm; I have not adjusted the attenuator on the mainboard. I think the AD831 mixer is okay with the higher LO level.
These are quite nice devices, and really give a homebrew radio much of the feel and features of a store bought radio. They are quite feature rich, including band switching, memories, RIT, dual VFO's, offsets for proper SSB and CW, multiple tuning steps including variable rate tuning, and quite a bit more.
The display is very legible - when RIT is activated, the frequency offset is displayed in the upper right corner of the display.
Here, as in my 14 MHz SSB rig, the VFO is paired with a nice Bourns detentless rotary encoder to give a store bought radio tuning feel. Unlike my SSB transceiver, here I have used the onboard switches, which required the use of a smaller tuning knob. On my SSB rig, I used outboard switches which allowed me to use a much larger tuning knob on the same vertical height panel. This is easy to do, as all of the switches are brought out to the XH connectors on the back of the DDS, for easy connection of outboard devices. These VFO's are also capable of direct frequency entry with a key pad. On the SSB rig, you can see the four most important switches brought out to the right of the display, and a blue 1602 LCD is swapped for the stock yellow.
Out of the package, there are a few mods that need to be made to make these devices work optimally. They are delivered with absolutely zero documentation. I believe the origin of these devices is an Indian amateur, I have attached a PDF that gives enough information to set up and operate these devices. It shows everything but the hookup of a key pad.
This is really turning out to be a nice little kitchen table communications receiver. It exceeds my expectations for the project.
73,
Win W5JAG
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