Saturday, January 31, 2015

RTL R820T on RF Analyzer App and Galaxy S5

RF Analyzer app Galaxy S5

Ubuntu 14.04 LTS - Howto setup NTP working with GPS

I've been wanting to rely less on having Internet access with the "Driveby System".  There's a long way to go on that front yet.  However, today I was able to leverage two things I already had installed to accomplish a simple task.  The two computers I used in this system do not use a battery backed-up on board clock.  Which has meant that I required internet access to global time servers in order to set the clocks accurately.  

"Driveby" requires that all systems use as close the same time as possible, because in my case the GPS lat/long's are being recorded on one server, while the RTL noise floor reading are being logged on another server.  In order to line them up properly (to know where a noise floor reading came from accurately) the two system clocks must be in sync.

So today I finally got this setup and working properly on the GPS connected server following the directions noted in the link above.


The next task is to get the Odroid to use the TK1 (the one with the GPS/NTP setup now) as it's NTP server.  Thus keeping the two systems in time sync.

UPDATE this is completed, and working.  Both servers time are being kept in sync using NTP and the TK1 is getting it's time from the GPS.  Case close.  Whew...VERY cool!  And fairly simple.

SERVER (GPS attached) SIDE /etc/ntp.conf

pool iburst

driftfile /var/lib/ntp/ntp.drift
logfile /var/log/ntp.log

restrict default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery
restrict mask
restrict -6 ::1
restrict mask nomodify notrap

# GPS Serial data reference
fudge time1 0.9999 refid GPS

# GPS PPS reference
server prefer

fudge refid PPS

CLIENT SIDE /etc/ntp/conf
(Similar to the installed version with one line change)

driftfile /var/lib/ntp/ntp.drift
# Enable this if you want statistics to be logged.
#statsdir /var/log/ntpstats/
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable
# Specify one or more NTP servers.
# Use servers from the NTP Pool Project. Approved by Ubuntu Technical Board
# on 2011-02-08 (LP: #104525). See for
# more information.
# Use Ubuntu's ntp server as a fallback.
# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify nopeer noquery
restrict -6 default kod notrap nomodify nopeer noquery
# Local users may interrogate the ntp server more closely.
restrict ::1

Thursday, January 29, 2015

MFJ-5008 - Followup

The MFJ-5008 (purchase here) (view my photos here from a prvious post) has proven to be a solid bit of gear.  I had my suspicions when I bought it as to whether it would even work.  However, it works, and works very well!  I have used it while wearing a pair of Beats "Solo" headphones and seems to work well with them.

One of the things I'm trying to work out now is how to record the audio from a location to later analyze it.  I found an app that runs on my Android Smart Phone that should do the trick.  However, I also needed a USB sound card (dongle) that will plug into an OTG cable from the phone.  I bought on this week for about $7.00 on Amazon that is known to work with the app I'm going to try first.  The app cost almost $7.00 on google play.  SO for about $14.00 US I have a nice audio recorder (that also has a built in gps, and camera :-).

All very useful tools for recording the location of power line noise.

The idea is to setup the phone's app and the usb sound card, and connect the sound card to the audio output of the  MFJ-5008 to record the sound of noise.  

Once I have that recorded, I should be able to compare the noise signatures between what I'm hearing at home vs. what I recorded.  They won't be exactly alike...but should help in locating offending poles.

The important thing I'm trying to accomplish with all of this is to identify the noise sources I'm hearing from home and get ONLY those fixed.  That way my problem goes away, and the power company isn't chasing every single noisy bit on their system.  While they're not supposed to be creating this noise, I can't very well have them productively resolving MY ISSUES by fixing every single issue THEY HAVE.  I just need the ones I'm hearing fixed.

Anyway, I just wanted to post a bit about my next phase of plans with the MFJ-5008.

Now that I know most of the really noisy locations in town, I'd like to 'go out on rounds' and check them every day for say 2 wks and make recording of them...combined with weather data I believe that should prove to be quite useful and show more than due diligence on my part to getting this problem resolved.

I would like to mention also that so far it's been almost 2 weeks since I first sent my request to Ameren UE requesting a ticket and reply from them regarding what I knew about the local power line noise and so far I haven't had a single reply from them.  

I will try to call them on the phone in my next round of attempts.  If that fails to get a ticket number, I will send them registered (return receipt letters).  One way or another I'll get their attention.  There are a LOT more options if that doesn't succeed.

The last time I did with with Ameren they replied within 24 hours and had a truck out at my house.  This time seems different so far.  SO we'll see.

Friday, January 23, 2015

New Pole Found Ameren 570032

Found this pole buzzing on AM 1700 , as well as 50.1 144.2 and 432.1 mhz.
The street lamp is barely glowing and its dark out now for one hour.
Ultrasonic detector buzzes when spot on the street lamp.

Wednesday, January 21, 2015


Nice Power Line Noise Visualization - HackRF, SDR#, VAC, and Spectrum Lab

I wanted to get a real nice noise signature of the Power Line Noise issue here.  What I ended up doing was to use a Windows 7 machine (for a change).  I used the following:

  • SDR# 'sdrsharp'
  • HackRF One
  • Spectrum Lab
The newer SDR# includes and Audio FFT however, I'm unable to resolve how to alter the bandwidth of it down to < 1 Khz in audio frequency.  It seems STUCK at 0-18Khz or so.  This is too wide to be able to really see the 60hz spike and it's harmonics of 120hz 180hz, and so no.  They just don't even register in it's FFT for some reason.  SOOO....

Since the built-in Audio FFT doesn't resolve down to < 1Khz I setup trusty Virtual Audio Cable (I use line 2 for this, because other software I use uses Line 1 already).  So this pipes the AM audio out of SDR# via Virtual Audio Cable (Line 2) and then I setup Spectrum Lab to listen on that same VAC line.

Turns out this is PERFECT.  It's as good, but even better in that there's a TON I can inside Spectrum Lab, like line graphs, alerts, etc...for monitoring over long periods of time.

So here's a screen shot of Spectrum Lab (v2.78b25) setup to use VAC Line 2 (noted above) as well as SDR# below it.  

Look how simple it is to ID the 60 hz audio and it's harmonics.  Um....schweet.

(click to see larger)

I tried using GNURADIO and it's Audio Source, but damned if I can't figure it out on Windows.  It's fairly simple on Linux, but Windows is a different animal with GNURADIO.  Kinda of a let down.  It'd be nice to create flow graphs from my fancier/faster Windows machine that I could port over to my Linux machine and vice-versa but that's not happening.

Here's a few more views of that Spectrum Lab can do:

Tuesday, January 20, 2015

Driveby Code to be released on GIT HUB

When I first wrote the "Driveby" code I had in mind that one day I'd like to share it with others.  I realize that sometimes all it takes is a working example of an idea for others to move forward and even better a first revision.

With that in mind I'm planning to release my code for the Driveby System in the coming weeks.  Yes weeks (maybe longer) it depends on how much other work I'm involved with how much free time I get.

Bottom line is that this code needs to be a bit better organized is all.  My plan is to create some configuration files or a GUI to edit them so that folks can just download, configure and play.  My current system uses TWO computers so I'll need to setup some options where this can all be run from a single box or many boxes as in my case.

So that's what I'm thinking.  I'm all about sharing information with others and collaboration whenever possible.  It's pointless to reinvent the wheel over and over most of the time.  So that's why I'd like to share what I've done.  And that obviously includes the code.  Such as it is.

More on this as it moves along and becomes more available soon (I hope).

As of 2015-01-27 I've started on the process...

So as promised above, I've begun the process of generalizing the code I have written for "Driveby".  This will probably take some time...maybe longer than it should.  Please realize I work a full time job as well as doing this stuff on the side as a hobby.  I stand by my promise to release this code however.  I could release it as is, but I suspect folks would be struggling too much with trying to work out configuring it all.

My hope is to create a single config file that has all the needed site specific requirements.  

I may also modify the code a bit from how it is now to make it easier to change frequencies of interest.

2015-02-03 I'm about 3/4 of the way completed with this

I'll post updates HERE as they become available.

2015-02-08 Code released here.

So this isn't for the plug-and-play crowd.  It's not really production ready either.  However, it does function.  As you've seen in previous posts on this blog.  There will be site-specific issues YOU WILL HAVE TO FIGURE OUT.  There is no installer script, this is what it is.  My personal working/functional code that I use for Driveby System.  Use it at your own risk, make you own efforts to use it yourself.  I'm not a code babysitter, and I won't hold your hand to make it work for you.

If you know how to program in PHP, and know enough about Linux to Admin it, you should do ok.  A fair amount of knowledge with PHP, HTML, Javascript ARE required if you need to make changes to how it works.  That too is ON YOU.

Think of this as a starting point that was more than I had available when I started this.  

Thoughts on the next bit of test equipment I'd like

Now that I'm just waiting for some small handheld antenna's in the VHF/UHF range to arrive.  I've been thinking how nice it would be to use an Android device that has RF Analyzer installed on it.  This is a VERY COOL app that'll run on Android and connect to RTL SDR, or HackRF One (I have both and have tested it with both, and it seems to work excellent).  

Here is a video of what I'm talking about.  

It's just a quick view of how well this works.  What I'm doing is using a small whip antenna that is good for 50, 144, 432 Mhz on a HackRF connected to my Android phone and running RF Analyzer @ 44.25 Mhz listening to AM Mode and the source of my nearby Power Line noise.

With the combination of being able to take video's, and photo's and being able to use the GPS and RF Analyzer all in one device (well two if you include the RTL or HackRF)...pairing all these tools up to be used as a portable RF noise sniffer, and recording device seems like the next logical step.

  • RF analyzer paired up with a portable Arrow antenna and a HackRF to visualize the noise, as well as listen to it!  (YES the RF Analyzer app now can demod the audio, AM, FM, WBFM, SSB etc).
  • Photos and video from the Android Camera (gps linked)
  • On board GPS
On thing I've noticed about the HackRF is that holding it snug against the back of my Galaxy S3 increases the noise floor a fair amount.  So it's well know (I think) that the HackRF's case which is crap for RF shielding.  So I'll probably build a little Copper Clad PCB box to wrap around it or use some copper tape!  LOL

Anyway I'm envisioning all of this equipment mounted to the back of the VHF/UHF antenna, and while on site at a known noisy location all of this combined could help document a problem area.

The biggest issue I've had in the past with Power Noise tracking is the part where you need to document things each time.  With enough detail to be useful in debugging a problem.  Using all of this combined would make is as simple as waving your arms around with the gear doing all of the recording and minimal interaction required on the part of the user at the time.

This is also important from a safety standpoint.  For example you could actually be looking where you're about to plant your feet, or on coming cars, or big dogs, or downed power lines :-)  All kind of important!

The last time I'd used RF Analyzer it didn't include demodulation of the audio.  NOW it does and it CLEARLY works wonderfully!  Especially in AM mode which is helpful in power line noise hunting.

More to follow on this as soon as I've been able to video the operation of this...shouldn't be too long, I'm just waiting for my other android to charge up :-)

Monday, January 19, 2015

Next Steps - After locating a noise source

Now that the "Driveby" system seems to be catching things fairly well simply by driving around, the next steps are to:

  1. Stop and get out of the vehicle when I encounter a spike.  And have a good visual of the area - if possible.  Take some pictures, and note things like weather conditions (skies, wind, temp, humidity), and note the pole number (if there is one).
  2. Get out a VHF/UHF antenna and swing it back and forth, up and down, and all around the suspected site to try to get a closer indication of the problem source.
  3. Get out an Ultrasonic Parabolic dish and hunt around the area detected by steps 1 and 2 above.  With this type of device very often it's possible to narrow down the offending source to within about 12 inches.  Depending on the dish, and specs of the device. 
In order to accomplish steps # 2, and 3 above I've ordered these items.  
  • An MFJ-5008 - "Ultra-Sonic Receiver W/Parabolic Reflector, 40-kHz, Portable, 9-Vdc" which can be found here and HERE - While this device doesn't have many if any reviews on it that I've been able to find, it's price-point as an entry level ultrasonic dish for this purpose seems like a good place to start.  (Even though I don't like a lot of the stuff MFJ sells, some of it is absolutely perfect for a given task, and I'll give them the chance on this one).  There are others like the one Midnight Science makes called an RX-3.  But it's a bit over 2x the price I'm paying for this one.  And has semi-mixed reviews.
  • Arrow II Hand Held Portable, Item# 437X14
  • Alaskan Arrow Satellite Antenna with Split Boom and Duplexer, Item# 146/437-14WBP
  • Male SMA duplexer instead of BNC, Item# MALESMADuplexer
So the idea behind these added items will be to narrow down 'to the device on the pole' I hope...or at least within a few inches of the source.  A lot of these power line noise tech's that power companies use are semi-mediocre at what they do.  Some are EXCELLENT.  But what I'm trying to do is provide them with as much information as humanly possible in order to insure that they actually FIX the problems I'm aware of and that care causing such devastation on 50 Mhz Ham Radio here.

I do reasonably well on 50 Mhz here in Missouri.  However, I *KNOW* that folks are hearing me that I'm not hearing due to this local noise problem.

Anyway, I just wanted to post about the next round of items I'm intending to try to use and why.

Power Line Noise - 50 Mhz

(click to see larger)

Now I know what I'm looking for I see this 'signature' and stronger versions of it all over the place on the radio.

Note the 60 hz, and stronger 120 hz, and subsequent 60 hz increments.  These are a well known 'signature' of the North American (US anyway) 60 Hz AC Power Line Noise.

Below is a much stronger version of this down around 44.4 Mhz.

(click to see larger)

Sunday, January 18, 2015

Ameren UE Utility Power Pole 572795

Pole 572795 is now a prime suspect in my search for local Power Line Noise.  It seems to be emitting huge amounts of RFI between 44 and 51 Mhz.  See my recent post about this HERE.

I reran the Driveby System today (yeah, I need to come up with a better name than this!) this time I replace the 49 Mhz scan with 44.252 Mhz.  By the way, this noise source peak migrates it's primary frequency during the daylight hours about 200 Khz.  This morning when it was < 35 F outside it was around 44.485 Mhz and at the time I reran this test today in the afternoon around 4:30pm it was around 44.252 Mhz.

I'll update this post shortly with new Driveby System Maps that this round replaced 49 Mhz with 44 Mhz.  This made a HUGE difference in the end-resulting map, and seriously pinpointed the power pole noted above.

So it seems that the key at least in this case so far was to use a wideband pan-adapter to hunt for a massive spike noise source.  Once I did that I was able to easily identify the pole(s) I now now about.  Incidentally these poles are between 600-700 ft from my home.

In this particular case it appears that there are also some SERIOUS safety concerns.  The primary ground line has been severed about 1.5 ft. above the earth...and the wire coming down from the negative neutral AC line is simply dangling in the air a prime target for any middle-school kid to grab hold of it (because they're stupid).

Innovantennas HZE-LFA - Lo Band off the back

I was reminded today that some yagi antenna's at 50 Mhz (and probably other frequencies) exhibit a stronger LOWER resonance off the BACK of the yagi than off the front if the frequency you are trying to hear is lower than the yagi is actually resonant at.

For example years ago we used to use listen to 45 Mhz video from New Zealand by turning the 50 Mhz Yagi's we used to 180 degrees of the direct azimuth.  In other words, the back end of the beam was pointing towards New Zealand when listening for 45 Mhz TV video.

Today I experience this same phenomena and remembered "Oh yeah, I've seen that before!"

In this case I'm using my 10 Element LFA Yagi and was listening to BOTH 50 Mhz and 44 Mhz at the same time.  I noticed that when pointed directly at the noise source I was hunting that the 50 Mhz graph I was watching was very high.  But the the 44 Mhz was at least 4-5 db lower!  Doh!  I rotated the antenna 180 degrees and lo-and-behold the 44 Mhz came up and the 50 Mhz dropped.  (Just like the days of old).

Just thought I'd mention this in case anyone ever wonders the same thing, or is trying to figure out a similar issue, or maybe just to remind MYSELF !  

Take Care, and be careful out there!

Driveby System - 44.485 Mhz

This morning I was hunting around for the source of some power line noise that plagues me while I was still at home (before taking the Driveby System back on the road today).

Above is a video of what I 'finally' found.  (not sure why I didn't really search for this years ago).  Anyway I use HDSDR at home as a "pan adapter" for my large radio which is connected to my 57 foot long 10 element 50 Mhz yagi.  I've been hunting for a way to be certain that the noise I'm hearing *IS* power line noise.  One way I've read about is to analyze the AM audio and look for FFT spikes that are relative to 60hz increments.  So this would mean that you would see (possibly) 60hz, 120hz (definitely), 180hz, 240hz and so on when you analyze the audio from the AM signal.

Well guess what?  I already had been using a tool that could do this "HDSDR".  So with the pan adapter setup I use for my large ham radio the 9 Mhz IF output to a Nooelec "Ham It Up" HF to 125 Mhz up-converter.  Then I configure HDSDR to look at -134 Mhz.  Which puts me zero beat on the frequency in HDSDR that I'm trying to SEE visually.

Anyway...long story short.  I found something very interesting this morning.

Between around 44.235 Mhz and 44.6 Mhz (the best centered freq seems to be 44.485 Mhz) there is an EXTREME signal LOADED with power line BUZZ/HUM.  Looking at the Audio analyzer in HDSDR (lower FFT display on my screen in the video) you can CLEARLY see the 120hz, 180hz, 240hz .... spikes.

Knowing the actual center frequency of the Arcing noise source REALLY helps!  With that information I can program the frequency into and RTL or my Walkie-Talkie like HT (VHF/UHF handheld radio) capable of AM, FM, WFM reception.

I'm planning today to use the 49 Mhz RTL graph and mapping to be re-coded to use 44.485 Mhz.  because of what I've found this morning.  After I've mapped that all out I'll present it here as an update to this blog entry.

This signal is approximately in the 300-335 degree azimuth from my tower.  Here is a map of that area.

Also see a followup remapping post HERE.

(click image to see larger)


After driving around with just my HT radio and a tiny whip antenna I'm pretty sure I've spotted the worst of my noise sources.  It's located just behind a local middle school.  And the source pole was actually within about 6 feet of where I suspected the noise has been coming from.  As noted earlier this morning (see red line above map).

This map shows the location of the pole which you can see via satellite image.

(click image to see larger)



Um 2x WTF !!!  Notice the school, Notice the Fence, Notice this dangling Loose Ground wire is within reach of any stupid Middle-School Child that reaches for it?

Now check this out! Driveby confirms!

Saturday, January 17, 2015

rtl_fm receives "AM" also (and others)

"rtl_fm -M am -f 50.5e6 -r 12k -g 39.2 -E edge -A fast | aplay -r 12k -f s16_be -t raw -c 1" (without the quotes)

Starts up like this on my Ubuntu 14.04 LTS Laptop:

Found 1 device(s):
  0:  Realtek, RTL2838UHIDIR, SN: 1.3-56.3

Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
Tuner gain set to 38.60 dB.
Tuned to 50764000 Hz.
Oversampling input by: 42x.
Oversampling output by: 1x.
Buffer size: 8.13ms
Exact sample rate is: 1008000.009613 Hz
Sampling at 1008000 S/s.
Output at 24000 Hz.
Playing raw data 'stdin' : Signed 16 bit Big Endian, Rate 12000 Hz, Mono

underrun!!! (at least 258.228 ms long)

And sounds just about as good as my AM receiver does for picking up Power Line noise with almost no impact on CPU load.  I can barely detect it frankly.

I will probably attempt to add this into the Driveby System's Web GUI control panel so that I can have some preset's to switch to on various bands at the click of a button.

Driveby System - Possible NW source detected

2015-01-16 @ 4:30 pm CST 


  • winds calm (0-3 mph)
  • temp about 55F
  • skies clear and sunny

Yesterday I was out testing some tweaks to the Driveby System and after a long drive-test I came across an area that was causing the noise floor to rise considerably on both 50 Mhz and 144 Mhz.  From what I know, this is usually a good sign that there is a power line noise arcing source nearby.

It so happens that this location also coincides with an azimuth where I have noise from my home location.  The Azimuth I had previously noted on this blog was between 315 and 355 degrees from my tower.  After reviewing this test drive this morning I checked the Azimuth of this location using Google Earth's "Measurement Tool" and the Azimuth from my tower is almost exactly 335 degrees which places this noise source smack in the middle of where my large yagi at home had indicated there was a strong noise source on 50 Mhz.

This direction is particularly problematic when I'm attempting to talk to Japan,China,Korea on 50 Mhz in the summertime.

Here you can see the area I'd previously mapped out as a likely problem area from home.

I've marked the Azimuth and distance using Google Earth's Measurement Tool.

(click on the image to see a larger version)

Here is an audio recording of what it looks and sounds like from home.

And here is the mapped data from the Driveby System showing where is spotted high noise floors on 50 and 144 Mhz.

(click on the image to see a larger version)

And here is the graph showing the noise at this exact location.

(click on the image to see a larger version)

Driveby System - Inverter Noise

If you want to just skip to what I've decided on this is it:  (update 2015-01-20 this item has shipped and I'm awaiting it's arrival!)  I can't wait to see how this affects the Driveby System.

Problem Solved (I think)

2015-01-22 the DCDC-USB-200 has arrived.  I am feeding it with just about 14vdc and the DCDC regulator is working!  The whole assembly is also about 1-2 lbs lighter after removing the AC/DC supplies and replacing them with the DCDC.  

Systems are up, and happy (amazing little device!)  WAY more power available then this system will ever require I suspect.  

Here are some pictures of the swap-process I did and some results:

If you still wanna read why please feel free to continue.

The Tripplite PV375 when turned on even with nothing connected to it generates a butt-ton of RFI on 50 Mhz, I didn't check other bands but I suspect there is some there too.  In yesterday's drive test I used a Yaesu VX8 to monitor 50.485 Mhz "AM" mode.  As soon as I turned on the inverter I notice a huge amount of RFI into the little handheld radio.  At the time it was running on it's own internal battery and connected to the new external radio point off the Big Box's 8 port splitter which is fed from the Discone antenna feeding the Driveby System.

So .... This is something I was afraid of when I decided to try to use a 13.8vdc to 120vAC inverter to power the system.

So now I need to go back to the drawing board in order to provide regulated 12vdc and 5vdc.  It's important that whatever I use is as highly regulated to 12.0 - 12.3vdc and 4.95 to 5.15vdc so that the motherboards I'm using are happy.

When I first was thinking about power requirements for the Driveby System I thought I would need about 8-9 amps @ 12vdc.  Turns out that even with 6 internal fans, 1 Nvidia TK1, and 3 USB hubs all running off the 12vdc rails all of that only draws 2-3 amps.

The 5vdc is only running the Odroid XU3 and that only draws < 1 amp.

So the problem here is how to get a regulated 12vdc and 5vdc from a voltage that can fluctuate between 12.3 and 15v and is nominally around 13.8v.  When I was spec'ing things out for 8-9 amps @ 12vdc this was  fairly difficult to find an off the shelf regulator at that high an amperage.

I'm sure some SMART folks out there think resolving this would be easy.  But I've been finding it difficult so far to 1.) find an off the shelf solution or 2.) find a design I could build.

My requirements for the Driveby System appear to be:

  • 12vdc regulated @ 4-5 amps (to have a bit of buffer over the nominal 2-3 amp requirement) that can run off 11-15vdc from the vehicle.
  • 5vdc I can resolve by using a 12vdc to 5vdc converter that I already have if I can get a regulated 12vdc source

Friday, January 16, 2015

Driveby System - Added Spare external RF SMA port

I wanted to be able to sample or listen to the same Antenna connection that the 8 RTL's have access to.  SO this meant bring the 8th splitter port out to the front face of the Big Box that everything resides in.  Here's a pix of the now three front SMA ports on the Big Box for the Driveby System.

Right to left so far:  The red cable is a network cable to the Laptop used as a system GUI.  The left SMA connection goes to the L10 GPS antenna.  The center is the new external sma port that comes off the 8th (spare) splitter port and is used for an external radio.  Anything that can receive RF can be used there.  In this case I'm just going to use a little Yaesu VX8 set to "AM" mode on 50.485Mhz to listen for 50 Mhz Power Line noise. (this seems to be a good frequency for hearing it well).  The right SMA connector is goes from the 8-port splitter to the main 25-1300Mhz Discone RX Antenna.  Btw this is a new one I just got to replace the older one I use the last time I drove around.  That older one was in a slightly sorry state.  The newer one is a D-130J from Diamond Antenna.

Here's a pix that show the 8-port splitter I've been talking about internal to the Big Box you see above.  It's the grayish box with marker noting -9db of loss.  The top right most port is the one that is running to the new external SMA connector.  

When not in use I place a 50ohm dummy load terminator on the external sma connector.  This is supposed to keep things happy in the splitter.

So this new external port can also be used with another RTL and something like GQRX which I've also tried to do.  This works pretty good!  However, the low-end Asus X551M laptop I'm using for this project about maxes out it's dual core cpu when I do this.  I'd much prefer to use GQRX and an RTL than the Yaesu VX8 for listening/watching the band.  However, this is a limitation of the laptop I'm using.  I could probably run GQRX just fine with the Chrome Browser accessing the noise floor readings and doing the map visibility at the same time, but it looks like it takes the CPU right up to 100% and stays there pretty much.  I don't want to compromise my GUI view by pegging the CPU with the grqx software, so for now I'll just use the little VX8 to listen to the AM audio as noted above.  I'm sure it'll be fine, as this is what I've used in the past.  The down side is that I don't have the spectrum display and waterfall that GQRX provides.

One day I'll get a fancier laptop, but this is the only real reason I would need it at this point so there's no real drive for me to upgrade the one I have.

Thursday, January 15, 2015

Driveby System - Concentration Areas

I've marked out some likely areas related to various noise problems on 50 Mhz here.  I suspect I may have found a few already on my first drive-test, however, I have a LOT More work to do on this.  I plan to drive the areas noted in the map below VERY slowly a few more times.  I need some high wind days to drive test as well.  Some of the time wind impacts Power Line Noise issues around here.  So windy condition drive tests in the Orange areas of the map are a must.  The area marked in yellow denotes some sort of wireless device that floats around inside the Ham Radio band on 50.000 to 50.300 Mhz and tends to hang around between 50.070 and 50.170 Mhz.  It's about 30-50Khz wide FM which I can actually demodulate and hear quite easily with a wide band filter.  It shows up easily on my Pan Adapter for my 50 Mhz radio.

Here's the Map:

Some of these area have already shown up on my Driveby System GEOTAGGED map noted below with orange markers.  I've made some tweeks to the system so that these areas hopefully will show up better.