I’ve got a co-co antenna, F to coax adapter on the bottom. Coax to the house, Coax to SMC adapter to the pigtail to the dongle… i figure I need a length of cable with smc connectors on each end to go from the coax-SMC adapter, filter, filter to pigtail. Any other suggestions?
Not much else you can do really other than reduce the number adapters to the minimum. I have mcx to SMA (to the filter), sma to F type up to antenna, F type to N type male into the FA antenna. The adapters introduce loss. Others here can far better comment and gauge the loss effects on the adapters, but I never liked having more than I needed (if any).
SMC connector? Did you mean SMA or MCX? I think I fooled with SMA connectors in a previous life somewhere.
Correct… SMA… typo…
First, my setup: FlightAware 6db antenna, up 25ft AGL, 50ft LMR-400, N f-f adapter, 10 ft LMR-240 N male to SMA male, FlightAware 1090 filter, SMA-MCX adapter, NooElec NESDR Mini+ Al: 0.5PPM TCXO, USB into the RPi2.
Anomaly 1:
Once I had replaced the NHP-1000 filter with the FlightAware 1090, my reception shot up immediately, in number, reports, and distance, but which was still primarily in the <60 mile range (only 5% in the 60-120, 3 total in the 120-180, and zero above that). Then it started to decline. I checked the connections - everything seemed okay. And my reports were still up from the pre-FlightAware filter install.
Anomaly 2:
On Friday afternoon I checked my PiAware map/log. It showed twenty plus aircraft, and as I was watching, one by one they disappeared until it wasn’t seeing any! Then the number slowly returned, but distances were limited to <40 miles, number of aircraft were 5-10, and many were without positions. There wasn’t a thermal problem (I had the A/C running). Unplugging and reattaching the filter into the SDR showed no change. Waiting a couple of minutes before plugging it back in saw an improvement, but still the distances were limited. Was it the SDR itself, or was something else swamping it?
Anomaly 3:
On Saturday 8/29, my neighbor and I had the 40 ft (µ metal?) Brazilian Pepper Tree on our property line (to the SW of my house) trimmed about 50%. Much more open air (and my house got immediately hotter). After the clean-up, I went into the house to check e-mail, and checked the PiAware map/log. My jaw dropped. Suddenly I was seeing out to over 200 miles to the west and literally all directions had improved.
Now I’m seeing over 300 miles to the west. I have not touched a thing! I am stumped, but happy. If you go to my page: http://flightaware.com/adsb/stats/user/hoffchas, look at the coverage distribution for the past 24 hours, and then for 8/28. If you don’t want to:
Positions reported by distance on 8/28;
<60 mi 21596; 60-120 mi 1021; 120-180 mi 3; 180-240 mi 0; 240-300 mi 0; 300+ mi 0.
Positions reported by distance the past 24 hours:
<60 mi 35359; 60-120 mi 17062; 120-180 mi 4624; 180-240 mi 909; 240-300 mi 359; 300+ mi 99.
Any ideas?
It’ll be interesting to see what happens when k6rtm sends me the amplifier to try.
Chas AE6FD
I’m going to take mine off for a few days. In reality, my numbers went to crap for typical Sat, Sun readings. Still trying to get some information/answers on the gain setting for the RTL dongle.
Scott
No clue what’s going on – I’m doing surface-mount work tomorrow morning and will get the rework for your LNA done.
But the new numbers look great!
bob k6rtm
My personal opinion is that you’re wasting money putting a high gain commercial antenna inside a window if you are able to put even a simple dipole outside - more so if you can add an amplifier to the dipole (and if it’s out back it wouldn’t be obvious to the Home Owners Association.
You only need a filter if there is a strong source of interference nearby. It’t won’t magically improve a carp antenna or antenna location.
This ADS-B filter is now the “#1 new release in Automotive Replacement Air Filters”. Congrats!
This should look better now I think with the amp thrown on…but tried no filter first… number seems real though well over 3
Statistics: Tue Sep 1 20:44:17 2015 UTC - Tue Sep 1 21:44:18 2015 UTC
Local receiver:
6381633536 samples processed
0 samples dropped
0 Mode A/C messages received
61558303 Mode-S message preambles received
39526247 with bad message format or invalid CRC
21540140 with unrecognized ICAO address
439254 accepted with correct CRC
52662 accepted with 1-bit error repaired
-5.6 dBFS mean signal power
-0.7 dBFS peak signal power
75687 messages with signal power above -3dBFS
Messages from network clients:
0 Mode A/C messages received
49650 Mode S messages received
0 with bad message format or invalid CRC
0 with unrecognized ICAO address
49650 accepted with correct CRC
0 accepted with 1-bit error repaired
541566 total usable messages
18 surface position messages received
55442 airborne position messages received
52879 global CPR attempts with valid positions
almost 14% - need to reduce the signal level to the dongle you might get even more usable messages.
The filter will reduce the level a little, then you need to set the gain on the dongle down.
Thanks for the help. In the mutability set up where gain setting is default max what value do I put in there to reduce the gain. Thanks
MAX is about 49.6
Try using 45 ?
it’s a slow dance – change the gain, restart things, and look at the results a few hours later, hopefully after one of your local heavy traffic periods. I’m still fiddling with gain settings, getting them tuned in.
bob k6rtm
Well I have pulled my gain down to 35 with the filter in…still seeing a factor of around 4 or 5. However since adding the amp with the filter my number of planes seen has gone way up for an indoor install…the amp is a wonderful thing combined with the filter. Later today I am going to try 30 see if I can get the vaule to be sub 3. Thanks for every ones input.
I have 2 independent systems of antenna+coax+dvb-t+rpi.
I have set gain on my both dvb-t dongles to “max” (which means 49.6).
Both systems are identical except antennas.
The antennas of both system are located side by side, horizontal distance about 1 meter, same height, inside my apartment, near a large window.
I have no amplifier and short RG6 coax (15 ft/ 5m).
See the graph of message rate. The red ones show messages >-3 dBFS
SYSTEM 1 of 2 (benchmark/reference antenna)
SYSTEM 2 of 2 (antenna under test)
.
See the graph of message rate. The red ones shows messages >-3 dBFS
Hi ab cd, what are the ratios of the 2 antennas?
100 * (messages with signal power above -3dBFS / total usable messages)
Is there much difference between the two?
[Edit] also what is the Mean Signal Power of the 2 antennas?
Love the wiggly lines, but I don’t know what I’m supposed to look for…
Hi Dave!
**SYSTEM 1 - Cantenna (Benchmark Antenna) **
~ $ cat /var/log/dump1090-mutability.log
Statistics: Fri Sep 4 08:13:08 2015 EDT - Fri Sep 4 09:13:08 2015 EDT
Local receiver:
-13.2 dBFS mean signal power
-0.9 dBFS peak signal power
11290 messages with signal power above -3dBFS
927390 total usable messages
Calculations
100 * (messages with signal power above -3dBFS / total usable messages) = 100 * (11290 / 927390) = 1.217
SYSTEM 2 - CoCo 8 element, originally very poor performance, but greatly improved after adding capacitor (Antenna Under Test)
~ $ cat /var/log/dump1090-mutability.log
Statistics: Fri Sep 4 08:00:19 2015 EDT - Fri Sep 4 09:00:19 2015 EDT
Local receiver:
-15.1 dBFS mean signal power
-1.7 dBFS peak signal power
3647 messages with signal power above -3dBFS
855912 total usable messages
Calculations
100 * (messages with signal power above -3dBFS / total usable messages) = 100 * (3647 / 855912) = 0.426
.
Hi Peter
Read discussions about “messages with signal power above -3dBFS / total usable messages”, but did not fully understand. Decided to take a plunge and explore… 
Does anyone know if Collectd can pull those numbers out of the .rrd files and use them to produce the ratio for graphing?
…Tom