The radio telescope project has begun. Today I ordered a 20 MHz receiver from Radio Jove.  While we wait for that to arrive we have to source an 8 channel Analog to Digital Converter (ADC) for the data feed into RadioSky-Pipe.  RadioSky has run out of ADC’s, but they recommend Kitsrus out of Hawii.  

We have three surplus computers I bought from work.  Have to pick one and get an operating system (Windows 2000, probably, though Linux is a possibility), a monitor, and a keyboard. 

The biggest issue is the recommended dipole antenna. The kit specifies an East/West 23′ 3″ ft dipole with a 32 ft footprint, is ca 10 ft high, and uses guy wires to stabilize it. Sounds like a trip hazard and a target for vandalism to me.  In that vein, I have been looking at alternative antenna configurations. The folks at Radio Jove are reticent to recommend one, presumably because it is a step away from simplicity for classroom use.  That’s fine. I’m an experimentalist.

One problem with moving away from the dipole antenna design is the unwieldy half-wavelength dimensions. While the dipole eats up real estate, it is structurally simple.  One interesting design is the Moxon antenna.  This antenna uses a bent driven element with a bent reflector element.  Most people use it with the elements in the horizontal plane, thus picking up horizontally polarized signals.  While this makes sense for communications, I’m guessing that the 20 MHz signals from the sun and Jupiter are probably not significantly polarized.  

The Moxon is significantly more directional than a dipole with a front to back ratio 15 to 20 db.  This means that it must be pointed at the radio source for maximum gain.  But its directionality also confers some rejection of terrestrial signals from other directions. From what I can tell, the gain from this design with its reflector element is on the order of 5 db.  This is higher than a dipole but lower than a multi-element Yagi.

We’ll get some baseline experience with the recommended antenna and then begin to look at other configurations.

In my view, one can never know too much about electronics.  This site has some interesting circuit animations.  Cheers!