LIVE test beta version
Antenna Analyzer V1
I read an article by K6BEZ in which he took on the challenge of making an analyzer for 25 dollars.
This seemed like a good project to me. I decided to replace the pc with an arduino with readout.
My first version consisted of a classic LCD screen and some switches for operation.
The software worked, but the measured values were not correct.
After the necessary frustrations I found out that the output voltage of the DDS module was too low. So I had to look for amplification.
That's how I ended up with the version of DK2JK. It uses a two-stage transistor amplifier.
I made a test print. In the meantime I had also decided to replace the screen with a TFT touch screen.
In your local electronics store you can buy most of the supplies, but on the “chinese internet market” this can be done much cheaper.
Look out for an arduino mega, dds module with ad9850 and a 2.4” or 2.8” tft arduino uno screen on ebay or aliexpress. This costs about 20 euros. Count on at least 3 weeks delivery time.
The schedule:
I designed a print for this and distributed it to the builders (+/-45).
The working principle is fairly simple. The arduino controls the dds generator. The 2 transistors amplify this signal that is sent to the measuring bridge.
The 2 voltages are measured (forward and reverse). Via the diodes and the opamps, the voltages are converted into a direct voltage that can be measured by the arduino.
The swr is calculated with the following formula: VSWR = (FWD+REV)/(FWD-REV).
This is quite correct for values around 50 Ohms.
Testing with a resistance of 25 or 100 ohms gives a reading of 1.8 instead of 2.
I haven't been able to figure out how this happened yet.
The use is very simple.
By pressing the screen you can change the frequency , band and step.
Each time you press band you jump to the next band.
If you press scan, you will get a graph of the swr progression starting 200 kHz lower than the set frequency.
I have made software for different screens. You can request this via the contact form.