With up-conversion I am basically shifting the lower HF frequencies into a range that the SDR dongle can see. In this case with a 7MHz base frequency into the up-converter, the SDR will see it as 32MHz.
https://www.amazon.com/RTL-SDR-Blog-RTL2832U-Software-Telescopic/dp/B011HVUEME/ref=sr_1_4?ie=UTF8&qid=1504202463&sr=8-4&keywords=rtl+sdr |
Using what I had laying around, I found a 25MHz crystal so I made a crystal oscillator and buffer going into a double balanced mixer. This is all built into an Altoids container with a pigtail of RG-174 to go to the SDR reciever and a BNC for the antenna connection. The setup runs on a 9 volt battery.
Some images follow of the up converter below as well as a couple test videos of reception.
Transformers wound on binocular cores from science and surplus. -AC9LF |
Oscillator and buffer circuit with 25Mhz crystal. -AC9LF |
Double balanced mixer added with 9V connector. -AC9LF |
I put a simple low pass RC filter at antenna end with the cut off at about 30Mhz the values were 22ohms and 220pF respectively. I might change this to a better LC type filter later. Initial testing seemed promising with a small ~2 foot antenna hooked up as you can see in the short video below.
This first video is of a couple AM stations on the up converter.
This next video is of some SSB on 40 meters.
I may edit this with a schematic later. I don't have anything scratched down right now.
Crude up-converter doing its thing. -AC9LF |
I used Cubic SDR and Ubuntu Mate for the PC side of things.
Edit: 10/09/2017 schematic below.
https://drive.google.com/file/d/0B-GeQSy2vlYfSjMxVUM4ZWYzUTQ/view?usp=sharing
SSB reception with magnetic loop antenna attached.
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