r00t.cz

Page: Sats.Navid - Last Modified : Sun, 12 Feb 12

So here we have yet another Iranian satellite:

UHF downlink parameters     Frequency: 465 MHz Modulation: 2840Bd on FM (for recording, discriminator out. required) Data Coding: SYNC + Manchester encoded data bursts SYNC sequence: 000001010000110011011111 Frame: 24(SYNC)+1728bits(MANCHESTER encoded) Coding: Possible 32bit block code (27 words in a burst)

Comments:

1. Signal was heard just once with enough strength for decoding. Next passes were much weaker and currently no signals were heard from Navid for few days. (Thanks to Kodar for recording and info)
2. Burst data is manchester (biphase) encoded, however SYNC sequence is NOT!
3. Frame contains some changing data, arranged in 32bit blocks. Entire frame structure:
   
   ^{Data portion of frame after manchester decoding (864 bits)}
4. There is one bit always "0" in 32bit blocks, as you can see here:
   
5. No ASCII messages this time, but frame contents changes in time. Also no obvious frame or time counters.
6. More info will be added in case this satellite is heard again.