First Screenshots with SpectrumSpy + Airspy

Below are some screenshots from my first tests with the new SpectrumSpy application for the Airspy. I have the original AirSpy, not sure if it's considered the R0 or R1. The scan speed is pretty fast. It is certainly a very capable spectrum analyzer. My quick tests show lots of possibilities. My hopes for the future:

• SpectrumSpy gets integrated with SDR# (SDRsharp), allowing some ability to click into a signal from a broad scan.
• SpectrumSpy gets a plug-in architecture that will allow other developers to create new applications.
• Someone writes a Uniden Close Call equivalent, that can quickly pick out nearby signals (those that appear with a threshold (18 db?) above the adjacent noise floor.  (I need to check, I think Uniden's Close Call is 18 dB.
• Ability to get data out of SpectrumSpy similar to rtl_power and rtl_power_fftw

The pictures.  These really need to be seen at full screen to be appreciated.  These are full screen from a 1920 x 1200 (16:10) monitor.

The first image is showing the full range of the R820T tuner in the Airspy from 25 Mhz up to around 1,900 Mhz.  The top shows the spectrum view as you'd expect to see on an analyzer. The waterfall on the bottom is showing roughly 10 minutes of accumlated data.

Note: This is in a somewhat quiet RF environment. In other words, Not NYC!  For test purposes I'm using a small hand-held whip antenna, about 6-8 inch.  The gain is set pretty low.

One of the things I was looking for was how much background noise I have, and on what parts of the spectrum. Looks like there is are a couple of areas with some noise (520 mhz), 260-280 mhz, ...

Next are some screenshots that "zoom in", by reducing the scan range from the full scale using the choices from the menu, which are currently fixed.  These might be editable in the XML config, but I didn't get there yet.

Next up, 1 Ghz. starting from 25 Mhz. so that means centered on 525 Mhz:

Thing to note:

• The waterfall shows approximately 5 minutes of data.  The full bandwidth scan waterfall had nearly double that.  The only factor I changed was the amount scanned.  A 1 ghz scan completes in half the time of the full bandwidth approx 1.9 ghz scan.
• FM Broadcast between 88 Mhz and 2018 Mhz is easier to pick out.
• Problem areas where I'm picking up noise are more apparent.
• The noise at 520 Mhz isn't as constant as it looked.
• The wide scale changes in the waterfall are due to me holding the AirSpy.  There are some shielding problems I need to look into.  The AirSpy R2 has some fixes that my original AirSpy does not.

Now lets look at a 500 Mhz scan:

Things to note:

• Showing 500 Mhz, from 25 Mhz - 525 Mhz
• Note the noise that is generating evenly spaced lines in the 100 - 175 Mhz range.  This is something I'll need to track down.
• One of the strong/constant signals that is visible is NOAA weather radio from Riverhead around 162 Mhz.
• I'm occasionally receiving air band transmissions around 120 Mhz.
• Around 440 - 450 Mhz, I'm either seeing a signal with an image, or I could be seeing repeater activity, on both the input and output frequencies.

Next step down in the menu is for a 200 Mhz scan:

 Things to note:

• 200 Mhz, from 25 Mhz to 225 Mhz, (centered on 125 Mhz)
• waterfall now shows about 2 minutes, since the scan rate has more than doubled by going from 500 mhz to 200 mhz.
• The noise may start around 48 Mhz, and with harmonics/images roughly every 5-6 mhz.

Next, 100 Mhz scan:

Notes:

• Range 25 Mhz - 125 Mhz.
• Waterfall is covering 1.5 to 2 minutes, so scanning 100 mhz is happening pretty quickly.
• Main feature is the FM Broadcast band, 88 - 108 Mhz.
• Air band traffic visible around 123 Mhz.

Next, 50 Mhz:

Notes:

• 25 - 75 Mhz covered
• waterfall now covers only about 1 minute.

Next, 20 Mhz, showing the FM Broadcast band:

Notes:

• 88 - 108 Mhz. centered on 98 Mhz. 
• It's easy to tell which are the strong FM stations in my area.

Lots more to play with.  I have a SpyVerter up converter which will let me do < 30 Mhz, but it wasn't very interesting with only a short hand-held whip.   Hopefully I'll have a chance with a random wire soon.

Please let me know what you'd like to see and any observations you have on these spectrum scans in the comments.


EDIT:

So, I'm happy that I'm able to upload these images to blogspot at full resolution. I need to figure out how to get blogspot to allow clickable thumbnail/full res. images.   I'm going to try this over on Wordpress.com.  I haven't done much with WordPress, but need to get some experience for a work project.

See the WordPress version of this point.   Nicer looking but still no click to full-res version.

What is a dB, dBm, dBu, dBc, (Tutorial Videos from W2AEW on Youtube)

If the concept of decibels (dB) is confusing, this Youtube video from W2AEW has a very clear explanation with a demonstration using a spectrum analyzer:

• What is a dB, dBm, dBu, dBc, etc. on a Spectrum Analyzer?

https://www.youtube.com/watch?v=1mulRI-EZ80#aid=P-LGfIJuuH8

Remember: dB is a ratio of Power levels, so when you need to do a ratio of Voltages, the formula is different.  He doesn't mention that until late in the video.  However, he gives a much clearer explanation of why the formula is different (20 x Log10() vs 10 x Log10()) by doing the
math to demonstrate where the difference comes from.

(Remember P=I x E or P = (V^{^2})/R ?)

There is a table at the beginning of the video of the few things you should memorize both for your amateur radio test and for general use later:

• 3 dB represents a ratio that is a doubling.  Of the two things being compared, one has twice as much power as the reference.
• -3 dB represents a ratio that is a half.
• 10 dB is 10 times greater.
• 20 dB is 100 times greater.

Note: W2AEW has posted a whole bunch of good video tutorials on electronics and radio.

https://www.youtube.com/user/w2aew

A couple that might be relevant to prepping for your General Class amateur radio exam:

• Back to Basics: Voltage and Current in Capacitors and Inductors
• Basics of RF Mixers in Radio Receivers / Mixer Tutorial / Frequency Conversion

I've also found his oscilloscope and spectrum analyzer tutorials to be very useful.  He's very good at explaining and documenting things.  Compared to a normal text presentation, the demonstrations / experiments really drive the concepts home and show that it's possible to try these things for yourself.

Enjoy.

 

Using an Oscilloscope to Check Your (Transmitted) Signal

N2NOV had posted that Tektronix now has a Youtube channel with videos on how to properly use an Oscilloscope.  Many years ago, Tektronix published a good free PDF, The XYZ's of Oscilloscopes. It was
good but a little dry compared to a video presentation.

Well equipped radio operators have a special type of dedicated oscilloscope called a service monitor which allows viewing your transmitted signal, by tapping the radio frequency (RF) from the transmission line. Recently I came across a Youtube video that showed how to build a very simple RF sampling circuit that would allow using a common oscilloscope to monitor the RF output of your transmitter (transceiver).  While this won't do everything that a dedicated service monitor would do, it's a pretty cool way to check your signal if you only have an oscilloscope.  The RF sampler circuit described should be less than $10 in parts.

Personally I find this sort of thing to be very cool.  Even if I had an unlimited budget for buying equipment. I don't have the room to store it in NYC.

• How to Use an Oscilloscope
• Tektronix Youtube Channel
• How to monitor your Ham Radio Transmitter using an Oscilloscope

Note: This will only be useful for monitoring AM and SSB transmissions. I hope to come across something not too difficult to build that would be useful for looking at the output of an FM transmitter like the type most commonly used on VHF and UHF.