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

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Discussion Overview

The discussion revolves around the necessity and specifications of a .1MHz RF choke for the Itty Bitty Radio Telescope, including potential alternatives and clarifications regarding the choke's frequency and function.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant questions whether the .1MHz RF choke is a typo, as they could only find a 1kHz RF choke.
  • Another participant suggests using the 1kHz choke, arguing it may filter frequencies above 1kHz and could be more efficient than the .1MHz choke.
  • There is a proposal to replace the choke with a shielded enclosure for the batteries, which may be more effective, though the participant admits uncertainty regarding microwave circuit issues.
  • A different participant mentions the need for an adjustable choke or tuning coil, comparing the project to a low-frequency ham radio setup.
  • One participant believes the choke should actually be a 0.1mH or 100uH choke, suggesting that the original instructions may contain an error.
  • A participant expresses interest in building the telescope, indicating a desire to use it as a teaching tool for physics students.

Areas of Agreement / Disagreement

Participants express differing views on the necessity and specifications of the RF choke, with no consensus reached regarding the correct frequency or whether the choke is essential.

Contextual Notes

Some assumptions about the choke's function and effectiveness are not fully explored, and there is uncertainty about the implications of using alternative solutions like a shielded enclosure.

Who May Find This Useful

Individuals interested in building radio telescopes, educators looking for innovative teaching methods in physics, and hobbyists exploring RF circuit design.

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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