tried

Many times. USAF does this each time they launch a new GPS satellite, to
check out all the kit in a "high-res" view before they switch it on for
general use. They used to use an antenna at Camp Parks in the California
central valley. When that one was being overhauled a few years ago, they
used Stanford's "big dish" for a while. It gives about 60 dB gain at L1,
IIRC.

Hardcore GPS researchers have used that dish and a bunch of others over the
years. If you're interested, contact SRI. They used to charge a couple of
hundred bucks an hour for the Stanford dish.

Hard to use for weather forecasting, though, because you can only see one
tiny chunk of atmosphere at a time.

Cheers!
--Stu

Hi

If you go back into the papers from the early 1980's there is one where they used a high gain antenna and no knowledge of the coding scheme to pull timing off of GPS. I believe it was at White Sands, but that could be wrong.

Bob

On Mar 29, 2013, at 11:42 PM, Stewart Cobb stewart.cobb@gmail.com wrote:

On 3/30/13 5:31 AM, Bob Camp wrote:

One can just run it into a squaring circuit and recover the carrier, for
instance.  Recovering accurate carrier frequency isn't going to help you
navigate a ICBM to a hardened target.  Knowing the P-code is.

Hi

Ahhhh, but they did recover the code in addition to the carrier frequency.  Given enough gain (and thus directivity) they were able to capture the full transmission from a single bird. They could not pull the almanac data off of it, but the sat's orbital parameters are relatively easy to come up with.

If I remember correctly they came up with some pretty impressive timing numbers. The paper didn't mention any navigation results (gee… I wonder why…). It was the first public paper I attended that started chipping away the value of selective availability.

Bob

On Mar 30, 2013, at 10:26 AM, Jim Lux jimlux@earthlink.net wrote: