The AM Forum

I discovered that a large number of universities, including mine (NJIT) are using the following for creating SDR subsystems that are used in various research and educational activities.

Does anyone on this board have any comments about these:

A) USRP (DDC transmit/receive boards and associated daughter boards)

http://www.ettus.com/index.html

B) GNU (open source software for designing and implementing software defined radios)

http://gnuradio.org/trac/wiki

Stu

Stu,
This is very cool stuff but the price is a lot higher than HPSDR hardware.
Mercury RX is $329 and I think Penny exciter was cheaper. Mercury A/D samples at 122 MHz and the DDC output is around 1/2 MHz if I remember.
I think penny is the same speed. The next module coming is the filters and TR control with a way to pipe in a 100 watt amplifier to cover 160 to 6 meters.
I'm looking at a pair of MRF150s in class A to keep the TX IMD way down.
It would be cool if you could get your hands on the set up and check it out.
At one point the HPSDR guys were looking at hooking up with GNU

Frank

Thanks for the info on these.

I will almost certainly be working on joint projects with people who are using these at NJIT... so I'll post any insights I gain from those activities.

Our plan of record is to purchase several more of these in order to perform some externally-sponsored research on the use of spatial-temporal signal processing to pull signals out of noise and interference.

Maybe some of the results of those projects will be applicable for building a multi-antenna HF receiver that can perform automatic / adaptive nulling of line noise + one or two unwanted co-channel signals.

Stu

Stu,
There is a guy in N.E. if I remember doing 4 softrocks on 160 connected to 4 verticals to phase an RX array. I'll send you the link if I see it again.
You might join HPSDR and ask around. Most of the software guys are glad to answer questions and point you in the right direction. Phil Covington is a great guy. GNU comes up from time to time.

http://161.58.24.223/Phased_Array/slides/Vertical%20Antenna%20Layout.html

Frank

A very interesting "proof of concept" for using inexpensive hardware and free software to build (what could be extended to be) an automatic/adaptive array for nulling out multiple interfering signals.

Thanks!

Stu

Stu,

GNUradio (not to be confused with GNU itself) does not require the USRP. It originally was written to plug into a cable modem/tuner, and it will do that nicely. It will also work directly off your soundcard like any other SDR package will, along with a whole barrage of different harware options. The USRP is the more sensible approach, since it offloads tons of functionality to an FPGA/decimator combination and provides the host processor with more cycles for managing the user interface. The USRP costs more than the HPSDR stuff, but you do not need it in order to use GNUradio successfully.

I mentioned this package to you on the air a while back, but you didn't seem at all interested. I also mentioned it on the board almost a year ago, only to be told that I don't know what I'm talking about, and basically treated like a war criminal for even opening my mouth.

Have fun with it. I'm certainly never going to bring the subject up again.

--Thom
Killer Agony One Zipper Got Caught