Re: [ATM] Radio astronomy sorry if OT

[Dominic-Luc Webb <dlwebb@canit.se>]

On Tue, 5 Oct 2004, Bob May wrote:

> The C-Band TV dishes are, in the 8' size, giving about a 2 deg. beamwidth at
> the 4.5GHz.  This means that at the 1.3GHz or so it will have about 6-8 deg.
> of beamwidth which will be quite sufficient to fine Jupiter if you are smart
> about it.
> Bob May

Bob, you're a smart guy, but I worry you misunderstood me. I think the
Jupiter listening activities happen well below 1 GHz and more like low
MHz (sorry I cannot be more specific, not my subject). Given what
people normally actually use for Jupiter listening, that 8 foot
dish would be ackward. I meant that for other amateur radio astronomy
efforts, which occur for instance around 1.2-1.6 GHz, the poster's
8 foot dish seemed quite appropriate. One of his questions was whether
it could be used for any kind of radio astronomy, and of this I am
quite certain the answer is "yes". Of course, one can (and pros with
massive radio scopes do) listen to Jupiter at higher frequencies, but
the basic amateur stuff is KHz to certainly below 40 MHz. Think about
it a couple seconds... you can pick it up with a regular stereo tuner.

To those interested, read up on Jupiter listening. There is a lot on
the Net about this and be forewarned that it is not adequate to
merely point a directional antenna in the direction of Jupiter when
it is over your head, although I once inadvertantly picked it up.
One thing not mentioned on the Net, to my knowledge, is that
Jupiter broadcasts over a large range of frequencies that pass
into some HAM radio, commercial and government reserved bands that
are often strong enough to contaminate even a well made rig with
a directional antenna. Part of the trick will be to identify a
quiet band in your area and consider the exact type of signals
(i.e., bandwidth, sidebands, etc) for your data acquisition.


Dominic-Luc Webb

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