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Basic functionality example

A project log for Microwave Transmitter

30 - 6000 MHz synthesizer with power amplifier

PeroPero 08/11/2017 at 11:012 Comments

Verifying that all components are working properly enables me to run the first functional test of the MW transmitter - frequency synthesis. In the repo, there is "Basic" example that configures MAX2871, attenuation, filter and ADC for RSSI detectors (even though the latter ones do not work, presumably). 

The configuration is set as follows:

I intentionally set the DIVA so high so that I can measure the output frequency with my RTL-SDR dongle. With 5 dBm there should be no problem detecting some signal. 

The "Basic" example makes user choose register content readout and turning on/off the RFOUT. 

However, things didn't go as planed. Good things first: there was some output, and I could control it (turn it on/off) with my program. Bad things: The signal was very low, way below the expected 5dBm level. And it was also very wideband and filled with spurious content. Here's an example screenshot from RTL-SDR that runs  "spectrum analyzer" program. 

I cannot say that the basic functionality test has been passed, so the further investigations and debugging must take place. I'm just not sure where to start looking from. Is the MAX chip configured poorly (it shouldn't be, I used configuration from datasheet example) or do I get some terrible damping from my circuit?


Discussions

Tegwyn☠Twmffat wrote 08/14/2017 at 11:55 point

Surely the main thing is that you've got a result? I'd be very pleased with this given the complexity of the project.

The green text shows a max of 24dB.

Is the datasheet example tuned to a particular frequency band? Does it work better on some frequencies than others?

  Are you sure? yes | no

Pero wrote 08/14/2017 at 14:40 point

I don't know how to be happy with only that... i've seen projects, including yours, way more complex to be working more decently. 

I didn't try many other frequencies, since my test equipment is limited to very low bands. What I care the most is to find out where is the damping biggest in my circuit board. 

  Are you sure? yes | no