Re-purposing DreamCatcher 2.03 and SDRx boards:


#21

I don’t think I was able to find Skyterra-1. It’s further west on the equator from Inmarsat 4-F3, but not enough to reduce the signal strength of signals from that satellite. Maybe I was hearing both of them or just I $-F3.

Or … It might be broadcasting on LHCP. I did not flip-over the brass plate on the patch antenna’s driven element to look on the other circular antenna polarity.

–Konrad, WA4OSH


#22

Well, on to more interesting things… Can we hear Ku band with a raw feed horn in the Seattle area? Hmmm. I don’t have my Standard and Universal Ku band feedhorns yet… What about the feed horn that’s in this little 18 inch RV antenna?

So let me explain the picture… In the background is a Winegard 18in RV antenna. I took the feedhorn and clamped it with my Velleman circuit board clamp and then fed the RG-6 coax to (a shameful mess of) adapters that convert F to N and N to SMA. And the SMA connector goes to the RF+DC side of a Mini-circuits 15542 bias tee, which I supply with 12 volts (all of this is not shown in the photo). Then the RF side of the bias tee connects to the SDRx, which you can see is plugged-into my Linux Skywave laptop. The feedhorn is aimed towards Galaxy 28.

So what do I get? Well, take a look at this picture first.

Interesting to say the least, but not what I had expected. The whole lower L-Band from about 900 MHz to about 1750 MHz has complex OFDM-like carriers on it, spaced about every 2.4MHz.

OK … what’s going on here? The first thing to realize is that there is actually a third kind of Ku band LNB that is used in North America. Shame on you Wikipedia, you forgot all about this. It turns out that the Winegard antenna is made for DirecTv, which uses circular polarization and not linear polarization. It uses a different LO, aparently 10,600 MHz, if I have figured it out right.

I’m still not sure what I’m really looking at. I’m still learning more and these experiments are helping me uncover more about satellite communications. Maybe some of you guys with the years of satellite experience here can throw a few hints?

I’m still waiting for the FTA Standard and Universal LNBs I bought… and eventually the DC3.

–Konrad, WA4OSH


#23

Just dropping this here along with all the other GPS talk earlier: https://github.com/jks-prv/Beagle_SDR_GPS

The KiwiSDR says it uses an on-board GPS to adjust its clock. But unlike every other radio I’ve ever seen with a GPS in it, this isn’t using a dedicated GPS chipset. Yes, it’s got a Skyworks front-end chip, but beyond that it’s all software. (Some of which runs in an FPGA, but still.)

I haven’t dug too deeply into it, but I think all the pieces are there.


#24

There is existing open source software for GPS and other navigation systems here:


Probably that is what they are using inside. The “GPS on RTL SDR” code is.


#25

All seems overkill for GPS based clocks to use software and sdr on the dc. GPS chips with serial out can be plumbed into the highly stable gpsd to pull pps pulse to sync realtime clocks in addition to the actual GPS timestamp. No need to reinvent it…


#26

Why not buy an HP frequency synthesized sig-gen? They’re only $1000.00 used. Mine’s good up to 1.2 GHz. I never expected to play with 23cm Ham Radio at home. Here I am playing with microwave frequencies on a budget.

The initial question was … what could you do to re-purpose a DreamCatcher or SDRx board. What could you do with it? I merely put up a few ideas.

Myself said…

Sure, you can buy a 10MHz 1PPS GPS Disciplined Clock or even a Rubidium standard on Ebay for around $100.00 You can even buy an HP435B power meter (without the sensor) for $25.00. It has a stable 50MHz reference oscillator in it. But how do you calibrate its frequency? There’s no need to reinvent any of this stuff.

Sometimes, it is cheaper to simply buy things from E-Bay and stack a whole bunch of appliances together. Sometimes, the point is to learn something and figure out how to make something rather than just buying the appliance.

For me, there are all sorts of uses for a stable 10 MHz source. Using that 10 MHz frequency input into a referenced synthesizer, you can generate frequencies up to 4 GHz fairly accurately, but it would be a multiple of 10 MHz. This would make a nice marker so you know where you are receiving with an RTL-SDR.

–Konrad, WA4OSH


#27

I use my Dreamcatcher (on Armbian) now with rtl_tcp on my LAN Network.
Most of the time it is connected to my DIY QFH on the Roof to autorecord Weathersatellites or the ISS (International Space Station) as you can see and hear in the video below.

I also tested running spyserver and got it running on the Dreamcatcher, but it is not optimized at all and loads the CPU to around 85% at 900mhz bandwidth of the SDR when using Full_IQ. Any other mode loads the CPU to 100% so the stream is not useable. So rtl_tcp is the best choice here i would say.

regards,
Manuel


#28

I found the same thing in testing sdrdaemon on the Dreamcatcher, couldn’t keep up with sending the IQ data at real-time over UDP. rtl_tcp seems to work well for me, regardless of sample rate too. I was also able to get OpenwebRx running on it, but csdr is using too much CPU, not sure I can optimize the compile further, need to check what the SoC supports for off-loading floating point calc’s, can only get 1msps and 1 user. Even openwebrx running on (yes, ON) a PlutoSDR can handle 1 user at almost 2 msps and 3 users at 600ksps when csdr is compiled with neon and softfp support, but that’s with the dual-core ‘hack’ enabled, without it, its useless. :slight_smile:

Would love to hear what others are using this hw for as well!


I am confused with components of complete kit
#29

I am bummed I only used my kit for Outernet a few times, I am a relative novice at hacking and stuff of this nature but I would like to be able to re-purpose my gear for something…just need a little help. I am in the North-east USA.


#30

So what was in your kit?
What receiver did you get?
What antenna did you get?

Since you are obviously a ham, I have a couple of ideas…

Konrad, WA4OSH


#31

It was exactly a year ago, I bought it off the Outernet store…the L-band antenna, CHIP, and I guess it runs Skylark?


#32

So it sounds like you got an SDRx board. Did you get an active antenna or the passive patch antenna?

You can run your SDRx usb “dongle” into a laptop running Windows or Linux. Use one of the many programs to snoop around and decode some of the stuff that’s out there.

We have a Ham Band in the middle of the L-Band at 23 Centimeters.
1240-1300 MHz: CW, Phone, Image, MCW, RTTY/Data.

if you are near New York City or Newark, NJ, take a look around in the ham band and see who is out there. Here in Seattle, I’ve found a bunch of people doing analog amateur-TV, a couple of D-Star repeaters, some people playing on CW and SSB. 1296.1 is a great USB frequency.

I’ve played around with LoRa on 915 MHz. But Outernet has gotten me interested in running LoRa on 1.2 GHz.

–Konrad, WA4OSH


#33

Here are some pictures to help identify what you have:

This is an SDRx:

This is a DreamCatcher 2.0

This is the passive patch or air-gap antenna

This is the active or ceramic antenna

–Konrad, WA4OSH


#34

Thanks for all of the ideas. I have the patch antenna. I am about 25 miles east of NYC. My club has a 1.2GHz repeater on 1288.0, it doesn’t get much use though.


#35

What are you using to hold the patch antenna in that picture?


#36

It’s not my installation, but that of someone on this forum.

It looks like a cellphone holder. I’ve used a Velleman circuit board holder. I’ve built a waterproof enclosure out of a lunch tub. There are all sorts of ways the patch antenna can be mounted. Look for ideas on this forum.

–Konrad, WA4OSH


#37

1288.0000 - NY Glen Oaks W2VL 136.5 Queens 2008/02/16

Wow … an FM repeater on 1288. This is wide-open for a project!

Is the 1.2GHz FM repeater linked?
As a project to get more people interested in 1.2 GHz, could you suggest a simple project of building an FM receiver for the repeater to monitor it?

You can make your own patch antennas.
LNAs for 2GHz are cheap.
RTL-SDR dongles work great. They’re cheap.
We all have computers.

There’s software galore for decoding RTL-SDR data for FM. Is the repeater linked to the other repeaters? For example is your 220 repeater linked to it? If you buy an inexpensive 220 radio, you can key-up and transmit on the 1.2 GHz repeater. Now with the very simple RTL-SDR receiver, you can hear the repeater.

Wow … More use of your 220MHz and your 1.2GHz repeaters!

How about data?
How about using the repeater for Data? Would you allow more than just voice on it?
What if you could decode the data being sent? And talk about it on 2M?

We have nets here in the Seattle area devoted to sending various protocols over a repeater. You can send pictures, packets, try exotic modes, even compressed video etc. all over the 1.2 GHz repeater that you guys already own.

Hmmmmm?

–Konrad, WA4OSH


#38

Follow-up project idea…
What could you do with a 1.2 GHz up-converter?
A cheap 2 meter, 220 or 440 FM radio board to drive it, and a 1W amplifier behind it?

You need to quit playing with appliances and have fun with ham radio – experimenting and making things again.

–Konrad, WA4OSH


#39

Hi K2EPM,
this one is mine, this is a tablet car holder, fit nicely with the RTL-SDR V3 + LNA underneath with a tie-rap.

It still running through the window for L-Band as INMARSAT STD-C EGC receiver, work great.

Have a good one.


#40

Users following Immarsat C and F, SafetyNet C, Mini C, Fleet 77, Swift 64 and Classic Aero may be interested in the change in satellites
Or as they call it… migration starting in april 2018

see the user migration guides in
https://www.inmarsat.com/support/i-3-to-i-4-services-migration/