Stargazing Is a .1MHz RF Choke Necessary for the Itty Bitty Radio Telescope?

AI Thread Summary
The discussion centers on the necessity of a .1MHz RF choke for the Itty Bitty Radio Telescope, with participants questioning the specified frequency and suggesting alternatives. One user proposes using a 1kHz RF choke, which may effectively filter higher frequencies, while another suggests constructing a shielded enclosure for the batteries as a potential solution. There is also speculation that the original instructions may have contained a typo, with some believing the correct specification should be a 0.1mH choke instead. The importance of the choke is emphasized as a means to prevent battery clips from picking up ambient microwaves. Overall, the conversation highlights various approaches to addressing the RF choke issue in the context of building a radio telescope.
redguy12
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I'm putting together the Itty Bitty Radio Telescope. In the instructions (see: http://www.aoc.nrao.edu/epo/teachers/ittybitty/procedure.html), it says to use a .1Mhz RF Choke. I have been unable to locate this particular frequency, as the only one I have been able to locate has been a 1kHz RF Choke? Can anyone help me? Was it a typo or do I actually need a .1MHz RF Choke?
 
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I can make the following suggestions:
*Try the 1kHz choke... it should filter all frequencies above 1kHz so may be even more efficient then the suggested .1Mhz choke.

*Check around the web for designs for home-made RF Chokes.

The point of the choke is to prevent the battery clips from acting as an antenna picking up ambient microwaves (i.e. nearby cell phones etc). So...

*You may be able to replace the choke with a shielded enclosure for the batteries. In fact this may work even better but I'm not up to speed on microwave circuit issues (only broad theory) so can't say for certain. Try finding an aluminum enclosure with a coax junction which will hold your batteries.
 
Thanks, have you built this type of radio telescope already?
 
redguy12 said:
Thanks, have you built this type of radio telescope already?

No but it looks interesting. I've bookmarked the link and may try it this summer.
 
you need an adjustable choke [tuning coil]. i haven't built one of these things either, but, it is little more than a low frequency ham radio with a funny antenna and extra shielding.
 
I'm new to the forum having I stumbled upon it looking for add'l info on the IBT. I believe the choke you are looking for is a 0.1mH or 100uH choke. I think the information published on the 'How to build' sheet was in error.

I'm a physics teacher looking for some new ways to excite the students. I think working with a radio telescope will help in the understanding of the EM spectrum and provide a different way of doing physics in this area We'll see.

Take care,

Sean
 

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