sat monitoring

[kma371]

I want to get into mil-sat montoring. The setup I have is a discone and a 996. Can someone help me out on what I would need in addition to what I have and provide me with a list of freqs I'd be able to monitor from California?

Thanks.
Bill

 

[ka3jjz]

Go see the new Space and Satellite monitoring forum. Pay attention to the Inmarsat thread.

Good satellite tracking software like SatScape is also a must. We have a couple of useful links on the Satcom wiki page.

73s Mike

 

[qc]

hers some sites that has some information on Satcom http://www.uhf-satcom.com/ and this one sells antennas http://www.time-step.com/products_inmarsat.htm

 

[prcguy]

The general freq range for UHF military satellites is about 245 to 272MHz FM and searching in 5KHz steps will land on all frequency plans. Most in-the-clear stuff I hear is between about 260 and 265MHz and 99% of all UHF satcom is encrypted but you will hear various groups pirating the satellites and speaking Spanish or Portuguese. There is some occasional brief testing in the clear and the ultra rare cases when US personnel come up in the clear by mistake. I use a tunable receiver (Icom 7100) and search in AM mode, which is easier to uncover signals than searching in FM. At best a Discone will be frustrating as most signals will be extremely weak and you will miss a lot of potential comms. I have used yagis, crossed dipoles, helix and every kind of military satcom antenna and my best luck is with a home made “egg beater” antenna designed for amateur satellite work. I scaled the dimensions for UHF satcom freqs and with a pre-amp at the base, it gives great signal strength and doesn’t need aiming. You would have to be an experimenter and handy with tools to whip one up but I could probably locate the dimensions if you are interested.
UHF mil satcom is geostationary and I don’t know why someone would need a satellite tracking program as mentioned in another post. Good luck, it’s very satisfying to catch a signal that has come from so far away.
prcguy

 

[FrankJ]

I've heard some of the Spanish speaking pirates in the 260 Mhz range using just my Realistic PRO-43 and a 220 Mhz Ham band rubber duck antenna!


Frank
(PRO-2004, PRO-43, BC780XLT, Grove Omni-II, various rubber ducks)

 

[K0ATC]

PRCGUY has it nailed, i've been listening for years though I do use a directional yagi. I'll have to try the egg beater, didnt think the signals would be strong enough. Do you use a preamp with that? Anyways it can be fun but I would recommend a stand alone reciever for just milsat. Comm's are few and far between and you dont want to sit there all night with the only receiver you have and hear nothing. Mine was always hooked to my sound card and recorded. Good advice prcguy.

 

[prcguy]

I need pre-amp in my setup because there’s 75ft of coax feeding the egg beater. With a very short coax run it should work fine without a pre-amp. I lucked out and found a surplus satcom pre-amp mounted in an outdoor NEMA enclosure with a 240 to 270MHz input filter. When properly assembled, the egg beater is RHCP and the main lobe is supposed to be from near the horizon to 45-50deg or so, just perfect for my location. A yagi, Discone or other linear polarized antenna will loose about 3dB right off the bat due to circular/linear polarity issues. Somewhere on this forum I posted a pic of my tower and you can see the egg beater with the pre-amp box right below it.
prcguy

 

[K0ATC]

Sounds good, i use a crossed yagi so i dont loose too much in reguards to circular polarizaton. I do not use a preamp, but have a run of LMR-600 so loss is not so much an issue. Sounds like a nice setup, i'll have to look into it, it would be nice if i did not need to point the antenna. I have built egg beater antennas before, i used them for WX sat.