a Pigtail sometimes is a Pig a.k.a. message-rates


#1

just to let others know.

today i did some testing with about 6 dongles. while the differences between the dongles (3 nooelec and 3 rtl-sdr.com) are small i stumbled over something i couldn’t believe. i have lots of pigtail-cables sma/sma and sma/mcx - all nearly identical looking and about 10-15cm long. but there are reasonable differences in message-rates (about 200/sec). with the same setup and dongle i can get 1.300 or 1.500 msg/sec depending on pigtail. and no - not a question of gain and attenuation. this was my first thought - so i tested this too - but no - some pigtails are pigs …

maybe you should check your pigtails too :slight_smile:

cheers
tom


#2

If the impedance is not correct, there will be reflections of the signal at every discontinuity. Since the pigtail is very sort, the attenuation of the reflected signals is almost zero and timing is very close to the actual signal.
Two reasons why it would give a lot of collisions and errors in decoding.