Thursday, January 19, 2012

21cm Line Downconverter Testing

This project is the heterodyning downconverter I have designed and assembled for radio astronomy purposes. It will be used to convert 1420Mhz Hydrogen Line reception from my 10' dish and feedhorn / LNA assembly down to a more manageable frequency of 100Mhz or so. It consists of a mini-circuits mixer along with a Z-Comm VCO for the LO. This particular VCO has a frequency range of 850Mhz to 1600Mhz, ideally covering the 1420Mhz band. A few mini-circuits low noise mmics are used for amplification along with a mini-circuits low pass filter to filter out the original LO and source frequencies.

Last week after returning from vacation I received my downconverter boards and started assembly. Here is the final assembled downconverter ready for testing:

This downconverter as I began testing has excellent performance. I need to do some further testing and measuring to calculate its noise and gain, but I have been very pleased so far. Because of the flexibility of the VCO, I have had some fun during testing downconverting and also upconverting various frequencies around, the following video show upconversion of FM bands to 900Mhz: