I was emailed by a few people off list that are interested in the
Mode-S/ADS-B code. I am still working on it.
I got the DPD Productions antenna just before Thanksgiving, but it was
too windy to put up right away. Sitting on the first floor in the
middle of a wood frame house, the antenna was picking up aircraft from
40 to 140 miles away depending on direction. I could not see low
altitude aircraft to the south of the nearest busy airport, which is
eight miles south. 44 feet above the ground on my roof is a different
story and I can see aircraft from 150 to 210 miles depending on
direction. Although the DPD antenna is higher gain, I do not get the
same level of interference as the colinear. The DPD antenna is suppose
to be a narrow bandwidth antenna. I tried the wideband preamp with the
DPD antenna and had the same problem with the noise floor rising and
I bought a SBS-1 last week. It is a commercial Mode-S/ADS-B receiver
that is smaller than the USRP. The sensitivity seems slightly better.
It could handle the wideband preamp better with just a slight decrease
in range. I am currently working on providing a port 30003 compatible
output for my receiver. Then I can use Planeplotter and can compare my
code to the SBS-1.
My nearby major airport has a ASDE-X system for monitoring aircraft and
vehicles on the airport surface. It appears they are installing an
ADS-B Multilateration system as I get a couple of the sensors. They use
DF18 (Non-Transponder Extended Squitter) and just send an ID and
Multilateration status. Two of them ID as STEST123 with the category of
Fixed Ground/Tethered Obstacle. The third recently appeared with an ID
of PTEST123. The SBS-1 also picked up the IDs so it can decode at least
some DF18 formats.
I want to do a UAT receiver and was planning a trip to Philly to look at
the TIS-B/FIS-B ground segment transmissions. I got a surprise when I
found out the New England area has TIS-B/FIS-B services. Someone did a
demo of a receive only system. The TIS-B service only transmits if
there is a ADS-B aircraft using UAT in the area. Being able to receive
TIS-B would be good because it includes non-ADS-B aircraft. There is
also cross-linking of UAT and Mode-S so ADS-B aircraft on Mode S ADS-B
should show up on UAT.
It is an iPhone application using a separate UAT receiver costing $1100.
I looked at the 978 MHz UAT frequency and think I see the signal but it
does not completely match up with the specifications. The system uses
slightly over 1 megabit per second FSK with a over 600K shift. I see
what looks like the mark frequency, but instead of the space frequency I
get another signal at the center frequency (978.0 MHz). If I use a
simple PLL FM detector flow graph with a scope sink I do see what looks
like a bitstream. The current plan is to get my laptop updated and
setup, then go mobile. I suspect there is a transmitter at a nearby