Coaxial Collinear Antenna for ADS-B Receiver.

The original antenna obtained with the ADS-B receiver AirNav( RadarBoxPRO is so great product that it is hard to build a better home made omnidirectional antenna with a higher gain than the original one. During my almost one year period of experiments with various types of antennas I built only one which fulfilled this expectation – it is the coaxial collinear antenna.

Concept of construction.

 

The main component for the building is a 75 Ohm coaxial cable used for the satellite TV or 50 Ohm coaxial cable. Another components are a connector type F or SMA, insulating tape, PVC pipe with the outer diameter 12 mm and suitable end-seal for this pipe. The necessary tools are the caliper, sharp knife, scissors, glue for PVC and the ohmmeter. The basic element of the coaxial collinear antenna is coaxial cable (Figure 1) with the length calculated from the wave length of the ADS-B signal.

 

The wave length of the signal is

lambda = c/f

where is velocity of the electromagnetic signal,
in the vacuum, i.e. c = 300 000 [millions meters per sec],
is frequency of the ADS-B signal, i.e. f = 1090 MHz,

so that wave length lambda is 275 mm.

 

The length L of the basic element is the half wave length reduced by the velocity factor of the coaxial cable (the velocity of the electromagnetic waves in the coaxial cable is lower). I used the 75 Ohm cable RG-6U/32FD with the velocity factor 0.85 and 50 Ohm cable Tri-Lan 240 with the velocity factor 0.83 and I used the same element length for both cables, i.e. L=0.5*275mm*0.85=116 mm.

 

The basic element of the antenna.

 

Figure 1 The basic element of the antenna.

 

The basic elements are connected to the chain in which the outer conductors and inner conductors are counterchanged between two adjacent elements (Figure 2).

 

Coaxial collinear antenna.

 

Figure2 Coaxial collinear antenna.

 

Such assembled elements are still the coaxial line. This line is connected to the receiver with the balanced input 50 Ohm impedance. My experiments indicated that it is beneficial to connect outer and inner conductors on the opposite end with the 75 Ohm or 50 Ohm to preserve the VSWR near 1.

 

Construction of the Antenna.

 

I recommend to have the inner element conductor longer about 50 mm (Figure 3) on both sides than the part with the outer conductor to enable good contact with the outer conductor of the adjacent element and also make assembled elements rigid.

The basic elements before connecting.

 

Figure 3 The basic elements before connecting.

 

Insert the small tape piece between two elements before connecting them.

 

Connecting of the basic elements.

 

Connecting of the basic elements.

 

Connecting of the basic elements.

 

Figure 4 Connecting of the basic elements.

 

(Video file of the basic elements connecting for the AVI files player.)

 

Check connected elements with the ohmmeter before final assembling because there are many possibilities to make short connection between conductors and it is a problem to find such a connection if antenna is finally assembled. It is comfortable to begin assembling from the first element with the balance resistor and check if there is 75 Ohm or 50 Ohm between conductors.

 

The assembled antenna is terminated with the “F” or SMA connector and inserted into the PVC pipe.

 

Assembled antenna.

 

Figure 5 Assembled antenna.

 

The 16 elements antenna fits to the 2 m long pipe, 8 elements fits to the 1 m long pipe. The “F” or SMA connector is fixed with the insulation tape and PVC glue to the pipe.

 

Fixing of the antenna F connector.

 

Figure 6 Fixing of the antenna F connector.

 

The opposite end of the pipe is covered with the end-seal.

 

End - seal of the pipe.

 

Figure 7 End – seal of the pipe.

 

Antenna is used in the vertical position due to the polarization of the ADS-B signal.

 

Antenna mounted on the mast.

 

Figure 8 Antenna mounted on the mast.

 

Connection of the feed line.

 

Figure 9 Connection of the feed line.

 

Lightning and Static Electricity Protection.

 

There may be applied four barriers against lightning and static electricity between antenna and input of the ADS-B receiver.

 

The first barrier is PVC pipe by which is collinear coaxial antenna covered. This barrier avoids mainly damage caused by discharging of the static electricity of the body of the person who manipulates with the antenna, but also is the barrier against lightning.

 

The second barrier is lambda/4 protection stub (Figure 10).

 

lambda/4 protection stub.

 

Figure 10 lambda/4 protection stub.

 

View of the lambda/4 protection stub.

 

Figure 11 View of the lambda/4 protection stub.

 

The stub is a coaxial line with the short connection on the end and is connected to the feeding coaxial line via “T” element of the “F” connector on the opposite end. Its length is velocity factor*lambda/4 = 58.5 mm. Due to the theory of the coaxial lines such stub is parallel resonant circuit, i.e. its impedance is very high for the frequency 1090 MHz. For higher or lower frequency the impedance is very low. More ever, the end with the short connection may be connected to the earth and by this way drain out static electricity. Using of such stub doesn’t cause the significant decreasing of the antenna gain.

 

The third barrier could be the signal amplifier. I used the usual TV antenna amplifier with the frequency range from 47 MHz until 862 MHz, gain 20 dB and impedance 75 Ohm. Except amplification of the signal the amplifier will become with high probability “the victim” of the lightning and such damage is easier replaceable and is not expensive as is the ADS-B receiver replacement. The amplifier is very useful for the fourth barrier 75/50 Ohm transformer (the more details below). The apparently not sufficient amplifier frequency bandwidth is not important. The ADS-B frequency 1090 MHz is only 26,5% higher than the highest amplifier TV working frequency, but it doesn’t mean that it is really the highest frequency which can be transferred and amplified by it. If we assume that amplifier is first order dynamical system with the decrease -3dB at 862 MHz, the decrease at 1090 MHz would be only -4 dB, i.e. your amplifier doesn’t have gain 20 dB, but “only” 16 dB.

 

The fourth barrier is 75/50 Ohm transformer (Figure 12).

 

75/50 Ohm transformer.

 

Figure 12 75/50 Ohm transformer.

 

View of the 75/50 Ohm transformer.

 

Figure 13 View of the 75/50 Ohm transformer.

 

It consists from the two parts, each is coaxial collinear antenna. The first collinear antenna is built from the 75 Ohm coaxial line and is balanced with the 75 Ohm resistor, the second collinear antenna is built from 50 Ohm coaxial line balanced with the 50 Ohm resistor. They are applied to themselves as close as possible with the mutual half element shift. The signal from the 75 Ohm part of the transformer is transferred to the 50 Ohm part very effectively without galvanic connection. More ever, the 50 Ohm receiver input is matched to the 75 Ohm circuit of the antenna or amplifier output, there is not combination of the 75 Ohm and 50 Ohm lines and loads. The small loss of the signal power caused by this transformer can be compensated by the amplifier.

 

The Results of the Tests.

 

I have tested coaxial collinear antenna with the 16 elements in the four configuration. The tests were made in the position N 49.1421, E 20.2404 on the piedmont of the hill Slavkovsky stit (High Tatras in Slovakia) on the altitude 950 m over the sea. Before the tests the 24 hours polarogram of the original antenna was measured. The feed line was long approximately 5 m.

 

The first configuration.

 

ADS-B receiver was connected to the coaxial collinear antenna, the lambda/4 protection stub was applied (Figure 14). The test was running 24 hours without interrupt. The weather was fairly well with blue sky and sun shining, without clouds, rains or storms, with slight wind, temperature varied in the range from 12 until 24 deg C .

 

First configuration - coaxial collinear antenna connected to the ADS-B receiver via lambda/4  protection stub.

 

Figure 14 First configuration – coaxial collinear antenna connected to the ADS-B receiver via lambda/4 protection stub.

 

Polarograms of the original antenna and the coaxial collinear antenna - the first configuration.

 

Figure 15 Polarograms of the original antenna and the coaxial collinear antenna – the first configuration.

 

The second configuration.

 

ADS-B receiver was connected to the coaxial collinear antenna via 75/50 Ohm transformer, the lambda/4 protection stub was applied (Figure 16). The test was made 6 hours without interrupt. The weather the same as was during the first test.

 

Second configuration - coaxial collinear antenna connected to the ADS-B receiver via lambda/4  protection stub and 75/50 Ohm trasformer.

 

Figure 16 Second configuration – coaxial collinear antenna connected to the ADS-B receiver via lambda/4 protection stub and 75/50 Ohm trasformer.

 

Polarograms of the original antenna and the coaxial collinear antenna - the second configuration.

 

Figure 17 Polarograms of the original antenna and the coaxial collinear antenna – the second configuration.

 

The third configuration.

 

ADS-B receiver was connected to the coaxial collinear antenna via amplifier, the lambda/4 protection stub was (Figure 18). The test was made 24 hours without interruption. The weather was the same as during the first test.

 

Third configuration - coaxial collinear antenna connected to the ADS-B receiver via lambda/4  protection stub and amplifier.

 

Figure 18 Third configuration – coaxial collinear antenna connected to the ADS-B receiver via lambda/4 protection stub and amplifier.

 

Polarograms of the original antenna and the coaxial collinear antenna - the third configuration.

 

Figure 19 Polarograms of the original antenna and the coaxial collinear antenna – the third configuration.

 

The fourth configuration.

 

ADS-B receiver was connected to the coaxial collinear antenna via amplifier, the lambda/4 protection stub was applied on the input of it, the 75/50 Ohm transformer was applied between amplifier and receiver (Figure 20e). The test was made 12 hours without interrupt. The weather the same as during the first test.

 

Fourth configuration - coaxial collinear antenna connected to the ADS-B receiver via lambda/4  protection stub, amplifier and 75 Ohm/50 |Ohm transformer.

 

Figure 20 Fourth configuration – coaxial collinear antenna connected to the ADS-B receiver via lambda/4 protection stub, amplifier and 75 Ohm/50 Ohm transformer.

 

Polarograms of the original antenna and the coaxial collinear antenna - the fourth configuration.

 

Figure 21 Polarograms of the original antenna and the coaxial collinear antenna – the fourth configuration

 

Some Final Conclusions.

 

1 – It seems that the optimal configuration is fourth. The polarogram indicates high sensitivity. The triple protection barrier against lightning and static electricity decreases probability of a damage.

 

2 – The experiments of the coaxial collinear antenna with the 8, 16 and 32 elements indicate that the amount of elements over 16 doesn’t bring significant effect on the antenna gain but the length over 2 m becomes not acceptable. The good compromise is 12 elements antenna – its gain and length 1.5 m are acceptable.

 

3 – The optimal installation of the antenna is on the non conducting elastic mast.

 

4 – The mechanical performance of the antenna is very simple and elegant. Its shape makes it proof against strong wind.

 

Appendix after one year of experiments.

 

I have tested antennas with the 8,12 and 16 elements and have found that more than 12 elements don’t bring significant change of the polarogram. From the mechanical point of view the optimal antenna is with the 8 elements – it fits to 1 meter long tube.

 

The terminal resistors are not mandatory to achieve high sensitivity of the antenna and good transfer of the 75/50 Ohm transformers – their ends could be opened. However the resistors are useful for the monitoring of the conductivity of the antenna and transformer elements and also for discharging of the inducted static electricity.

 

As optimal configuration has been found the following:

 

Optimal configuration

 

Figure 22 Optimal configuration – coaxial collinear antenna connected to the ADS-B receiver via lambda/4 protection stub on the amplifier input , amplifier, lambda/4 protection stub on the amplifier output and 75 Ohm/50 Ohm transformer.

 

Amplifier is situated as near to the coaxial collinear antenna as is possible. First lambda/4 protection stub is on the amplifier input, the second on the amplifier output.  This part of the antenna is situated outdoor on the mast and is connected with the indoor part with the feeding line. Indoor part consists of 75/50 trasformer and ADS-B receiver. Such configuration has good gain and the polarogram is similar to one  on the Figure 15. The main advantage of this is the robustness against static electricity inducted on the antenna.  Lambda/4 protection stubs are not grounded not to provoke direct lightning strike into antenna. The 75/50 Ohm transformer and indoor environment separate the ADS-B receiver from the outdoor danger of static electricity and lightning.

 

This configuration is working safely during storm without freezing or damage of the ADS-B receiver. Also outdoor amplifier on the mast is safely protected thanks to lambda/4 protection stubs.

Dusan Balara
balarad@balarad.sk

KN0CK HF Converter Rev. 4 is Released!

The complete Rev 3 KN0CK HF Converter has sold out and been discontinued. That’s okay, though, because it’s been replaced with the KN0CK RTLSDR for HF Revision 4! This model incorporates a lot of the feedback from the community about the old stack – especially the expanded tuning range, since the new model can now upconvert from the 6m band (54 MHz) versus 30 MHz with the previous model. It’s even smaller and still manages to be easier to manufacture, too, and it retains the core Mini-Circuits pre-amplifier and 120MHz local oscillator frequency.

 

Receiver Closed Up

 

Receiver Opened Up1

 

It’s a pretty great performer, too.

 

NAVTEX 9.0 MHz

 

It’s available for sale over at Easy-Kits for the same price as the Rev 3 converter.

 

If you’re more of a DIY type, you can also purchase one of the remaining unmounted Revision 3 Bare Board to build into its own enclosure or attach to a dongle you already own if it fits in the case. 

Via: http://blog.kf7lze.net

Embedded rtl-sdr setup: RTL-SDR + OpenWRT = OMG!!

1.
To see in the new version of the osmocom rtl-sdr package http://sdr.osmocom.org/trac/wiki/rtl-sdr the new TPC version, I decided to try to realize my idea about a small embedded rtl-sdr setup.
The basic idea was to run the small rtl-sdr util on a small embedded box connected with the dbv-t dongle at near the antenna, and transmit the data on ethernet connection. The more processing and vizualization can be continue on the desktop/laptop machines.
To this setup I choosed my old small linux box, the NSLU2. It has 2 USB conncetors, network connection, and, more than 2 years ago I installed on it a Debian lenny version, on a 4 Gbyte pendrive.
The running version of linux:

LKGE25945:/home/src# uname -a

Linux LKGE25945 2.6.26-2-ixp4xx #1 Thu Nov 5 05:37:51 UTC 2009 armv5tel GNU/Linux

That time was used as a test setup for a “navigation computer” for a small boat, intelled on it a meteo software, gps and aprs daemon, a Blitzortung lightning detection client, and more. The summary of this can be read here: https://sites.google.com/site/nslu2navigation/
That time I installed on it the development packages, a “native” gcc compiler, to compile source packages directly on it.
Now I tryed to install on it the rtl-sdr software too:
The steps I used:

1. The dependency of the rtl-sdr is the libusb 1.0 version. I didnot find binary package to this armel architecture, I downloaded the source, and compiled it. This was standard procedure with the configure, make, make install commands.

2. On the osmoscom git repository, I didnot find a downloadable compressed (source) package, it can be access only through the git clone mechanism. On my NSLU2 I havenot git installed. I made the git clone on my desktop, and tar-zipped on it, and after I moved the fresh distribution package to the small box with wget.

3. The rtl-sdr packege offers two different way to configure and compile:
a. use the cmake. I tryed to find the binary for debian package to the armel architecture, it seems, it was, but now the repositories are empty for this old debian packages.
b. use the autotool. It run on my NSLU2, I choosed it. It is important to use the -i option, because without it send only errors connected to some m4 macro incompatibilities. I used this command, proposed here: http://sdr.osmocom.org/trac/wiki/rtl-sdr
autoreconf -i
after this you can use the standard method to configure, make and make install (if you would like).

4. to run the tcp version, I use this command:
LKGE25945:/home/src# ./rtl_tcp -a 192.168.1.77 -f 433920000 -s 400

The -a parameter is the IP address of this NSLU2 on my local LAN, I use the default port, which is 1234.
I used the 433.92 MHz ISM band for test, because there is nearby outside, a wireless temperature sensor, it sends a short strong signal at every seconds, usefull for test. Finally I choosed 400 ksample for digitization speed. I used the small GP antenna, found in the package of the dvb-t dongle. I dont apply the rtl_tcp file dump feature.

5. When started the rtp_tcp program, it recognized the dvb-t dongle, and start to listen to the default port for a client connection. It send this mesages on an ssh terminal:

LKGE25945:/home/src# ./rtl_tcp -a 192.168.1.77 -f 433920000 -s 400
listen addr 192.168.1.77:1234
Found 1 device(s).
Found Fitipower FC0012 tuner
Using Terratec Cinergy T Stick Black (rev 1)
Tuned to 433920000 Hz.
Tuner gain set to 5 dB.
listening...

6. On the desktop machine I made a simple gnuradio block to make connection to this small server, and receive this TCP stream.
It contains only a TCP source block, and a WX Waterfall/scope or FFT block to receive/visulaise the data stream.

7. If I start the desktop client machine this gnuradio block, on the server you can see this messages:

client accepted!
ll+, now 1
ll+, now 2
ll-, now 0
ll+, now 1
ll-, now 0
.......
.......
comm recv socket error
Signal caught, exiting!
worker socket error
Signal caught, exiting!
all threads dead..
listening...

You can see on this messages, sometimes the server drop the connection, and restart to listening mode.
Practically you need a permanent ssh terminal to monitoring the state of the client.

Conclusion:
Dont wait to much miracles from such a small setup, but its working:
On a small  embedded linux box you can compile and run an easy way the rtl-sdr software, specially the tcp version of it, and you can use this setup as a remote sdr receiver and TCP server. Ofcourse, on your embedded box you need at least min one USB connector to connect the rtl-sdr comaptible dvt-t dongle.
Not all the tryed gnuradio sink blocks were working at the same way. Sometimes the server dropped the connection to the client.
It seems, it need more works around this setup to get a stable version of it.

On the picture you can see my first, temporaly setup of the embedded rtl-sdr server, running on NSLU2 box.
You can see on the NSLU2 box the connections:
Top white cable is the ethernet LAN cabel. The small black box is the pendrive, holding the OP system.
The next small box is the dvb-t dongle, connected to a tv cabel to the Turstain antenne, working on 430 MHz.
The bottom black cabel is the power connection.

Here is the gnuradio block to test the TCP connection:

 


Mon Apr 30 10:03:50 CEST 2012
Janos Tolgyesi
hg5apz (at) gmail


My first notes about this topics are here, mainly in hungarian:
https://sites.google.com/site/myrtlsdr/
Jegyzetek az rtl-sdr-el valo ismerkedesem tapasztalatairol


2.
Wed May  2 11:50:08 CEST 2012

Following the propose of the Admin on the rtlsdr.com site,
( http://www.rtlsdr.com/, used this nice illustration,
http://www.rtlsdr.com/wp-content/uploads/2012/04/83c67deea9c15e306c4786ebee92d4a42ee38073_large1.jpg )
I reconfigured my basic setup, with more Tux support: this is a “near-movable” version, with wifi connection.

The Tux supports the wireless access of the embedded rtl-sdr server:

 

I said, “near-movable”, because in this moment I didnot deal with the batteries powered solutions for the used small devices, but the connection to the embedded rtlsdr receiver was realized on wireless connection, used an old trick, how can bridgeing two parts of a wired LAN segments into one…
Originally I used this bridgeing to built “wireless cluster”, if you search on this idea, you can find this, now never accessible server/link: http://157.181.66.70/wmlc/english.html. This was my server, and this was my web page, I have a local copy of it, I put here two pictures from this publication, clarifying, how I realized the wireless connection of a distributed, virtual machine. It seems, now the problem is similar… Ofcourse the “real” solution would be to build the rtl-sdr utils into an openWrt, and use only one box to serve the “remote sdr receiver”, based on dvb-t dongle.

The remote connection:
My NSLU2 has only 2 USB connectors (maybe can extend it?) and I used one for the system software, connected on a usb pendrive. I use the second usb connector to connect the dbv-t dongle for the sdr receiver. Maybe can use another wifi-dongle to build wireless connection to this box, but now I doesnot try it: The small embedded box has its limitation with memory and the cpu power, to serve the high speed data transmission, maybe not the best idea to put top of this to serve the local wireless connection.
Here is, where come up the old idea, to bridgeing the two segments of a local lan  into one with two wireless AP.
I use two Micronet SP918BK modells:
http://members.chello.hu/b.globekom/micronet/

This small, cheap AP-s have the so called AP Bridge Point-to-Point Mode. This mean, based on this configurations, the two AP-s accept data transmission from the pearing device, based on the mutually used/configured MAC addresses.
This two pictures quoted from my old web page:
1. Setup and testing the minimal “segments” of this lan.

2. The configurations details used two cheap Micronet AP-s for this bridgeing.

The basic check of this “extension”, it you can access the NSLU2 from a machine, sitting on the directly connected wires segment of the LAN.
In my example:
the router,s IP address: 192.168.1.1
the test (desktop machine) 192.168.1.110
the A participants AP of the bridge: 192.168.1.101
the “remote”, B participants AP of the bridge: 192.168.1.100
the NSLU2 box, with rtl-sdr server: participants 192.168.1.77
(in my actual configuration the client is another desktop, running on it ubuntu, its name is ubu10, IP address is 192.168.1.114
The first test to access the remote rtl-sdr server from the first desktop machine:

[root@centos5 ~]# ping 192.168.1.77
PING 192.168.1.77 (192.168.1.77) 56(84) bytes of data.
64 bytes from 192.168.1.77: icmp_seq=1 ttl=64 time=9.28 ms
64 bytes from 192.168.1.77: icmp_seq=2 ttl=64 time=8.93 ms

--- 192.168.1.77 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 8.936/9.109/9.282/0.173 ms

Ok, its working, but it put some small more delay into the connection, comparing to the direct wired access…

In the next stepps I used the previous commands, to start the rtl-sdr server with the tcp version of the utils:

LKGE25945:/home/src# ./rtl_tcp -a 192.168.1.77 -f 433920000 -s 400
listen addr 192.168.1.77:1234
Found 1 device(s).
Found Fitipower FC0013 tuner
Using Terratec NOXON DAB/DAB+ USB dongle (rev 1)
Tuned to 433920000 Hz.
Tuner gain set to 5 dB.
listening...

and I used on ubuntu the same gnuradio blocks, to test the connections, and the receive conditions at the remote dvt-t dongle.

On the picture you can see the two small boxes, working together to serve the remote dvb-t dongle:
One is the Micronet AP, it has its own 2.4 GHz antenna, and connected to the NSLU2 with a small piece of TP network cabel, (with the two black ends at the connectors). This small cabel represents the “remote wired segment” of my LAN. The NSLU2 carries the dvb-t dongle, it has its own antenna too, at the top of a small piece of antenna “boom”.

About the performace:

In this moment I dont able to say too much about this: the original, wired setup produced unwaited interrupts in the data transfers, sometimes it dropped the connection. Maybe you can improve this situation, for example to use the Trottle block from the gnuradio block sets…
The wireless segment in the local lan causes another unshure situations, depending of the 2.4 GHz propagations on the local conditions.
Another issues the interferences between the two radio systems: the wireless AP transmit on relative high power, near the sensitive wideband receiver, representing the tuner in the dvb-t dongle.


Here is a short part from the network monitoring between the rtl-sdr server and the gnuradio client, running on desktop: It can be help to calculate the possible transmit speed.

0:05:06.691011 IP 192.168.1.77.1234 > ubu10.49839: Flags [.], seq 3400577:3402025, ack 1, win 2896, options [nop,nop,TS val 226695 ecr 121448], length 1448
10:05:06.692587 IP 192.168.1.77.1234 > ubu10.49839: Flags [.], seq 3402025:3403473, ack 1, win 2896, options [nop,nop,TS val 226695 ecr 121449], length 1448
10:05:06.692705 IP ubu10.49839 > 192.168.1.77.1234: Flags [.], ack 3403473, win 2761, options [nop,nop,TS val 121462 ecr 226695], length 0
10:05:06.694217 IP 192.168.1.77.1234 > ubu10.49839: Flags [.], seq 3403473:3404921, ack 1, win 2896, options [nop,nop,TS val 226695 ecr 121449], length 1448
10:05:06.695886 IP 192.168.1.77.1234 > ubu10.49839: Flags [.], seq 3404921:3406369, ack 1, win 2896, options [nop,nop,TS val 226696 ecr 121450], length 1448
10:05:06.696200 IP ubu10.49839 > 192.168.1.77.1234: Flags [.], ack 3406369, win 2761, options [nop,nop,TS val 121463 ecr 226695], length 0
10:05:06.697674 IP 192.168.1.77.1234 > ubu10.49839: Flags [.], seq 3406369:3407817, ack 1, win 2896, options [nop,nop,TS val 226696 ecr 121450], length 1448
10:05:06.697788 IP 192.168.1.77.1234 > ubu10.49839: Flags [P.], seq 3407817:3407873, ack 1, win 2896, options [nop,nop,TS val 226696 ecr 121451], length 56
10:05:06.697864 IP ubu10.49839 > 192.168.1.77.1234: Flags [.], ack 3407873, win 2761, options [nop,nop,TS val 121463 ecr 226696], length 0
10:05:06.725398 IP 192.168.1.77.1234 > ubu10.49839: Flags [.], seq 3407873:3409321, ack 1, win 2896, options [nop,nop,TS val 226702 ecr 121454], length 1448
10:05:06.761895 IP ubu10.49839 > 192.168.1.77.1234: Flags [.], ack 3409321, win 2761, options [nop,nop,TS val 121480 ecr 226702], length 0
10:05:07.158920 IP 192.168.1.77.1234 > ubu10.49839: Flags [.], seq 3409321:3410769, ack 1, win 2896, options [nop,nop,TS val 226745 ecr 121454], length 1448
10:05:07.159048 IP ubu10.49839 > 192.168.1.77.1234: Flags [.], ack 3410769, win 2761, options [nop,nop,TS val 121579 ecr 226745], length 0
10:05:07.160590 IP 192.168.1.77.1234 > ubu10.49839: Flags [.], seq 3410769:3412217, ack 1, win 2896, options [nop,nop,TS val 226745 ecr 121454], length 1448
10:05:07.160637 IP ubu10.49839 > 192.168.1.77.1234: Flags [.], ack 3412217, win 2761, options [nop,nop,TS val 121579 ecr 226745], length 0
10:05:07.162232 IP 192.168.1.77.1234 > ubu10.49839: Flags [.], seq 3412217:3413665, ack 1, win 2896, options [nop,nop,TS val 226745 ecr 121454], length 1448
10:05:07.162284 IP ubu10.49839 > 192.168.1.77.1234: Flags [.], ack 3413665, win 2761, options [nop,nop,TS val 121580 ecr 226745], length 0

 


Modification of the rtl-sdr dongle to the direct sampling receive

Here is the description of this small modification:
http://cgit.osmocom.org/cgit/rtl-sdr/commit/src?h=steve-m/direct_sampling
Steve said, it need to connect a long wire to the 1 or 2 pin of the rtl2832 chip, and can use the modified rtl-sdr tool to tune below 30 MHz.
In my first version of the parctical modification used a 2 pin connector. The first pin I soldered on the back side of the PCB, to the GND point of the covers of USB connector. The second pin is on the top side, and I conected it to the 1.-th pin of the rtl2832, when it connected to the smd capacitor.

After a little modification you can close the original plastic cover again:

Wed Jun  6 10:15:14 CEST 2012
t.janos


Osmocom rtl-sdr running on raspberrypi:

raspberrypi working as an sdr server

This is my first test on raspberrypi with the runing osmocom rtl-sdr utils, specially the rtl_tcp server.
The command, starting the server:

root@raspberrypi:/home/pi/rtlsdr/rtl-sdr/build/src# ./rtl_tcp -a 192.168.1.111 -f 433900000 -g 1

It found the connected rtl-sdr dongle, and start to listening:

Found 1 device(s).
Found Fitipower FC0013 tuner
Using Terratec NOXON DAB/DAB+ USB dongle (rev 1)
Tuned to 433900000 Hz.
Tuner gain set to 1.000000 dB.
listening...

The client runing on the same lan, on the ubuntu, the gnuradio 3.5 version, with a simple receiver block, consistst of a tcp receiver module and a WX GUI Waterfall Sink module.
When start the receiver, the server on raspberry send this message, and start to send the data:

Use the device argument 'rtl_tcp=192.168.1.111:1234' in OsmoSDR (gr-osmosdr) source
to receive samples in GRC and control rtl_tcp parameters (frequency, gain, ...).
client accepted!
ll+, now 1
ll+, now 2
ll+, now 3
ll-, now 0
ll+, now 1
ll-, now 0
….
….
….

But shortly it hung up, with this error messages:

comm recv socket error
Signal caught, exiting!
worker cond timeout
Signal caught, exiting!
all threads dead..
listening...
Use the device argument 'rtl_tcp=192.168.1.111:1234' in OsmoSDR (gr-osmosdr) source
to receive samples in GRC and control rtl_tcp parameters (frequency, gain, ...).

On the gnuradio waterfall gui we can see the data transfer, but without any received signal.
From this error messages it seems me, it need some network analysis to explore the error sources.
rpirtlsdr.jpg:
On the picture you an see the attached rtl-sdr dongle and the network cabel, to connect to my local network.
Near the SD card there is the usb cabel, power the rpi unit and the dongle.

Via:  https://sites.google.com/site/embrtlsdr/

Ham Radio Linux LiveDVD Ver. 14 supports RTL-SDR, HackRF and more

live_dvd_gnuradio
Andy, amateur radio operator KB1OIQ, has released the Version 14 of his Ham Radio Linux LiveDVD containing programs focused on amateur radio and SDR operations.

This is a remastered version of Ubuntu Linux. As of version 13, there are 32-bit and 64-bit versions available, as well as an image for the PengPod 1000.

This version contains a lot of amateur radio software including Fldigi, NBEMS, Gpredict, earthtrack, xcwcp and qrq, XLog and cqrlog, flrig and grig, xnec2c, fl_moxgen, aa-analyzer, owx, VOACAP, glfer, Xastir, gqrx, gEDA, and more!

Version 14 adds GNU Radio Companion, quisk, direwolf, linamc, FreeDV, wsjt-x, and Micro-Fox 15 Config (GPL), and many updates.

Recommended system requirements are a 1GHz CPU and 512MB memory at an absolute bare minimum (gqrx will require more – about twice as much).

Links to the ISO downloads can be found on Andy’s Sourceforge page.

Via: http://dangerousprototypes.com