how do I pick up milsats UHF?

[baj6974]

I have a BC 898T and interested in knowing if it is worth trying to monitor or not or if a majority of it is encrypted? What type of antenna would I need taking into consideration being in an apt. ground floor? What else would I need ie amp,pre-amp,etc......

I'd also be interested in Marisat and Fleetsatcom, chance any of these being in the clear or analog? Do I program the uplink or downlink ? Please tell me to where a newby can understand...Thanks in advance for your input....

[mancow]

First of all, the novelty of just hearing it aside, it's really not worth it in my opinion. It has been years since I heard a legit clear transmission. The rest is just digital hash with foreign pirate banter back and forth.

If you are in a bottom apartment you may be out of luck anyway unless you have a window facing the South. I just depends on how much structure is around you.

I have sucessfully heard them on nothing more than a whip antenna on a hand held but for anything reliable a yagi antenna is a good thing. A decent preamp helps too. A regular 220 mhz ham yagi would probably be close enough to work or you could just make one yourself. It doesn't need to be elaborate. My first one was a home made 5 element mounted to a camera tripod for aiming and worked very well.

I wish I had proscan several years ago when I caught the only interesting transmission I ever heard on that band so I would have had it recorded. Two guys with middle eastern accents were talking about aiming an antenna. One kept giving the other instructions to fine tune the position. The guy at the antenna must have been in an awkward position and started whining to the other one about his leg and how it's sore from trying to do what ever it was he was doing. It was definitely strange and kind of comical.

[w8jjr]

Most of it is encrypted now. But there was a time when you could hear the whole war playing out
Including High VIP conversions.
But if you want to try it here are some antenna plans.

The antenna I used was a 12 turn axial mode helix...Like some of the TV trucks have. The preamp was a a 20Db gasfet from Advanced Receiver Research. The receiver was a Yaesu FRG-9600. The helix antenna is VERY easy to build.

The following dimensions will give you about 16Db gain over the entire 242 to 270Mhz Milsat band:

Diameter of the helix - 14 inches
Circumference of helix - 45 inches
pitch or spacing of turns - 11 inches

If you're within 10% of these numbers it'll work fine.

The helix element can be constructed from refrigeration type copper tubing, 1/4 inch diameter.

The reflector can be anything from chicken wire
If you make it square, it should be .8 to 1.0 wavelengths on a side...so 45 inches will work well.

The polarization is Right Hand Circular.
If you're standing behind the antenna, at the feedpoint end, the turns of the coil should spiral away from you in a clockwise direction. The nominal impedance of the antenna is around 140 ohms. To get a good match to 52 ohm coax, make the first quarter turn at the feedpoint end run parallel to the reflector at about 1/8 to 1/4 inch spacing from it. This will act as an impedance matching transformer and give you a pretty good match.

DO use good low-loss coax. Belden 9913 will give you the best results.

This antenna has a beamwidth of 30 degrees and is VERY broadbanded. Be sure to use a non-conductive boom...hardwood works, fiberglass works much better. PVC tubing has too much sag.

Some of the milsat signals are strong enough to copy with only a ground plane or discone antenna.

[prcguy]

I think 16dD gain for a 12 turn is a bit optimistic but its still a great antenna for UHF satcom. You can cut the length in half and make a 5 to 6 turn helix and if you have a short feedline and sensitive receiver like the old RS PRO-2006 or PO-43, a preamp is not usually required.
You have to be very patient and persistent to hear anything in the clear these days. The Brazilian pirates are still there and I heard aircraft talking to McMurdo South Pole in the clear not long ago.
prcguy

Originally Posted by w8jjr

Most of it is encrypted now. But there was a time when you could hear the whole war playing out
Including High VIP conversions.
But if you want to try it here are some antenna plans.

The antenna I used was a 12 turn axial mode helix...Like some of the TV trucks have. The preamp was a a 20Db gasfet from Advanced Receiver Research. The receiver was a Yaesu FRG-9600. The helix antenna is VERY easy to build.

The following dimensions will give you about 16Db gain over the entire 242 to 270Mhz Milsat band:

Diameter of the helix - 14 inches
Circumference of helix - 45 inches
pitch or spacing of turns - 11 inches

If you're within 10% of these numbers it'll work fine.

The helix element can be constructed from refrigeration type copper tubing, 1/4 inch diameter.

The reflector can be anything from chicken wire
If you make it square, it should be .8 to 1.0 wavelengths on a side...so 45 inches will work well.

The polarization is Right Hand Circular.
If you're standing behind the antenna, at the feedpoint end, the turns of the coil should spiral away from you in a clockwise direction. The nominal impedance of the antenna is around 140 ohms. To get a good match to 52 ohm coax, make the first quarter turn at the feedpoint end run parallel to the reflector at about 1/8 to 1/4 inch spacing from it. This will act as an impedance matching transformer and give you a pretty good match.

DO use good low-loss coax. Belden 9913 will give you the best results.

This antenna has a beamwidth of 30 degrees and is VERY broadbanded. Be sure to use a non-conductive boom...hardwood works, fiberglass works much better. PVC tubing has too much sag.

Some of the milsat signals are strong enough to copy with only a ground plane or discone antenna.

[baj6974]

Originally Posted by mancow

First of all, the novelty of just hearing it aside, it's really not worth it in my opinion. It has been years since I heard a legit clear transmission. The rest is just digital hash with foreign pirate banter back and forth.

If you are in a bottom apartment you may be out of luck anyway unless you have a window facing the South. I just depends on how much structure is around you.

I have sucessfully heard them on nothing more than a whip antenna on a hand held but for anything reliable a yagi antenna is a good thing. A decent preamp helps too. A regular 220 mhz ham yagi would probably be close enough to work or you could just make one yourself. It doesn't need to be elaborate. My first one was a home made 5 element mounted to a camera tripod for aiming and worked very well.

I wish I had proscan several years ago when I caught the only interesting transmission I ever heard on that band so I would have had it recorded. Two guys with middle eastern accents were talking about aiming an antenna. One kept giving the other instructions to fine tune the position. The guy at the antenna must have been in an awkward position and started whining to the other one about his leg and how it's sore from trying to do what ever it was he was doing. It was definitely strange and kind of comical.

Thanks for your input...I'll give it a try. What about Inmarsat comms....would those be more interesting, encrypted?