Posts Tagged ‘SDR’

CommRadio CR-1a another SDR that looks interesting

I have never really spent much time on the Software Defined Radio arena, but the more I keep loo at them they are becoming so interesting. The CommRadio CR-1a communications receiver is a true SDR (software defined radio), but does not require a computer. Enjoy the benefits and performance of state-of-the-art SDR, but in a conventional radio package.

 

As much as I hate to say, it might be time for me to make a purchase and spend some time playing with these. I really like the size of the rig in comparison to the SunSDR2 (http://nicktoday.com/sunsdr2-sunsdr-mb1-transceivers-software-defined-radios/). Hard to tell until I see them both in person.

 

Full story: http://nicktoday.com/commradio-cr-1a-another-sdr-looks-interesting/

Video of busy 70 cm ISM band due to car key fobs

The audio in particular should make it clear how busy the frequencies around 433.92 MHz are:

Data recorded from an RTL-SDR USB dongle with the SDR# program using the Apowersoft Free Online Screen Recorder.

Related posts:

Not so busy 70 cm ISM band

Yesterday’s post entitled “Car keys in the 70 cm band” showed a very busy band around 433.92 MHz with up to 10 simultaneous transmissions. That snapshot was taken on a Sunday afternoon at 16:32 local time. Here is a much less crowded snapshot taken with the USB SDR-RTL dongle under the same conditions as the previous blog post. The difference is that this is from late Monday night at 23:34 local time:

Press image for a larger view

There are only three bursts of about 1 second length here. This shows that the activity in the band varies a lot and in my mind strengthens the case for believing that the main contribution is from car keys. But of course, one cannot be certain without decoding the bursts. That is possible for weather stations, as shown by Gough Lui in the article “RTL-SDR: 433.92Mhz ASK/OOK Decoding of Various Devices with rtl_433“. The bursts can easily be heard if the receiver is set for Wide FM, as shown in the settings of SDR# in the image above.

Thanks to all viewers who have made the former blog post the most popular on my blog for this week. Thanks also to the RTL-SDR blog which gave it publicity in the blog post “Looking at the 432 to 438 MHz ISM band“.

Related posts:

Car keys in the 70 cm band

The 70 cm amateur band covers from 432 to 438 MHz in Norway and radio amateurs have primary status. Secondary users are among others remote controls for keyless entry systems for cars since it is an ISM (Industrial, Scientific, Medical) band also.
I wanted to see how much traffic the secondary users generate. I used my RTL-SDR dongle with RTL2832U and R820T chips that I bought on Ebay for less than 10 US$ almost a year ago. The antenna was a roof mounted HL-B61N vertical (1.7 m long). This is the output of the SDR# program:
Press image for a larger view
It is clear that this band is pretty busy! No wonder that amateur repeaters have had to move their input frequency away from this frequency range. 
The waterfall covers 10-12 seconds and there are up to 10 transmissions simultaneously. The nominal frequency is 433.92 MHz and there are emissions from 433.75 – 434.05 MHz. I live in a suburban area with about 1 million people, but I imagine that I only pick up a small part of the remotes in this area since the car key transmitters are very weak. Anyway it demonstrates both the versatility of the cheap software defined receiver dongle, as well as how busy the band is. 

Related posts:

Where to find the $20 Software Defined Radio?

A while back I wrote a blog post about the availability of $20 software defined VHF/UHF radios in the form of re-purposed USB digital television dongles.

Now-days, with the improvements in software and documentation, the hardest part is finding the right dongle. What you order from EBay, and what you receive, can be two different things and only some of the dongles are suitable for use as VHF/UHF software defined radios.

So, I was pleased to see that at least one hobbyist electronics supplier has sought out and supplies a suitable device for SDR at a fair price :

Adafruit has available the USB dongle and “antenna” suitable for experimentation for $22.50, not far from the EBay (direct from China) price.

Click here to go directly to the product page: Software Defined Radio Receiver USB Stick – RTL2832 w/R820T

No, I didn’t receive a free evaluation unit and I don’t work for Adafruit … I’m just glad to see these useful devices available from a local company with an increased chance of you “Getting what you paid for.”

Adafruit also helpfully stock the adapter cables to convert the less common MCX antenna connector into the much more common BNC connector: MCX Jack to BNC RF Cable Adapter

Show Notes #113

Episode #113 Audio (Listen now!):

Topics
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More Topics
Announcements
  • Next LHS Live our special guests will be Richard & Brady from the LowSWR podcast
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Outro

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Music

LHS Episode #113: Eye to the QScope

Logo_Qscope_mYes, that's right: It's another brand-new episode of Linux in the Ham Shack! We know it's been a while since your RSS feed has been filled with the joy of our show, but we're back and aiming to stay on track (now that Richard is safely tucked into his cardboard box again). In this action-packed installment, your hosts discuss promoting Linux in the classroom, a wedding interrupted by a radio transmission from above, WA0EIR's updated suite of Open Source ham radio tools, and a novel analytics tool for hams called QScope. See you all down the dial very soon!

73 de The LHS Guys


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