This Is The End

Ladies and Gentlemen,

It is with great regret that I must announce the end of this blog.

As many of you have noted from past activity; as soon as I got in to ham radio, the updates to this site practically stopped. Was it because ham was sucking all my time? Not at all; it was more due to the fact my interest in the RTL-SDR setup had faded. Sure, I still hooked it up from time to time; I wasn’t as interested in DXing with it as much as I was fooling around with my ham equipment. I also somewhat realized that while coming up with cool tricks to do with he RTL-SDR gathered attention; I don’t think anyone really cared about just what I could or couldn’t DX with the dongle and Ham-It-Up. I reached a “wall” so to speak after just a few months; I wasn’t really reaching out and getting any new signals that I hadn’t already discovered.

I never did this site for anything other than self-satisfaction and boredom, though I’d be lying if I didn’t admit I had a glimmer of hope I might be interesting enough to pick up some sort of sponsor; I wasn’t going to make it that obvious or try entirely too hard to gather one. Sure, I wrote a couple of things that got picked up along the way; but I didn’t have the drive or the knowledge to push things further. I built mostly off work other people had done; I apparently just put the pieces together. Sure, some things have changed since then, and I didn’t bother to keep up once I got my ham license. There were many many updates to SDR#, some awesome plugins got released that, among many things, made doing things like SCA reception possible with just two copies of SDR#. But I never got around to doing anything about it; I kept saying “I’ll do it later” as I fiddled with antennas and VHF FM.

A little over a week ago, things changed dramatically. Jumping on a good price, I became the owner of an ICom IC-725 HF Transceiver. As I entered the world of HF, I soon left my VHF FM gear in the dust as I began bouncing signals off the ionosphere and making direct contacts with people hundred and thousands of miles away.

More importantly was the impact of the IC-725 to my SDR setup; it made it completely redundant. While I enjoy SDR, and I see it going in many places; I realized the RTL-SDR with an upconverter is not the viable radio it could be; and just pales in comparison to the IC-725. The dynamic range is really rather lousy; and the upconverter yields quite a bit of loss on the signals that hit the antenna. Seriously, the SDR stuff is just absolutely fantastic; the ability to see your spectrum as well as the complete flexibility in what modes you can decode with the ability to record IF’s is what I think I will miss the most. But, in all honesty; compared to a real radio, the RTL with an upconverter doesn’t stand a chance. IF you stick some pre-selection and more RF front-end tuning on it; you’ll drastically improve it’s performance. The best I ever had it perform was when I connected it to a crappy AM receiver; but even then, the loss through the upconverter still yielded sub-par performance.

It’s a fun toy; but that’s actually all it is, a toy. The dongle was never designed to be picking up weak AM mode signals on any frequency it seems. I knew this going in, but it’s only recently become clear that no matter how much you think you can make it perform like a better radio; it’s still just a toy.

So my RTL-SDR adventures have, for the most part, come to an end. I recently sold my upconverter as I no longer needed it; if I’m going to listen to general shortwave broadcasts or DX anything, it will be with the ICom. While the panadapter aspect is a lot of fun; the Icom has proven I don’t actually need that for effective DX. Granted, I can use a lot of lessons I learned from observing the RF spectrum in a waterfall; with those lessons in mind I can function without it. I can also, which I’ve tried; can tap the first IF stage of my ICom unit, which runs at around 70mhz, if I want or need panadapter function. I actually have quite a bit of work to do in that area.

So, to all the RTL-SDR users; I wish you the best of luck and fun in your adventures. But it is time for me to hang it up; to move on to “bigger and better” things as they say. While trading in 2mhz of waterfall for a simple dial and S-meter might seem like taking a step backwards; the dynamic range of the 725 and not dealing with 8-bit I/Q and spurious signals from overloading feel like a step forward. It’s literally the difference between say a $20 HF radio; and a $200 HF radio.

I will still be around however; and I have no intentions of taking the content of this blog down..as long as I keep a backup of the wordpress install; I’ll be able to move it around to new machines in the future. You can find me on Twitter, QRZ, or maybe any number of the other ham websites; just search for my callsign: KM4JOJ. And if you see me out on the air; feel free to say hello.

73 all,
-Jay/KM4JOJ

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Sorry bout the downtime, and lack of posts…and not upgrading.

Well…a lot has changed since March the last time I checked in. Let’s get caught up:

March 29: Took my exam and passed Elements 2 and 3; walked out of exam session with a General class ticket.

April 8: Officially became KM4JOJ at around 1pm. Ran outside with HT, realized I was right and I’d hit nothing from the house

April 12: Built 3-element yagi for working satellites. Fustrated with my QTH, coax, and antenna.

April 15: Got new low-loss feedline rather than 40 year old RG-58/U

May: Nothing happened. Really, nothing.

June: Bought some 1/2″ O.D copper pipe and built a SlimJim antenna, hoisted it 35ft up a tree. Also installed PL Tone Encoder to Kenwood 2m FM rig. Finally… I could hit lots of stuff.

Today: Logged in to blog for first time in well over 2 months.

I honestly haven’t done much worth writing about. You can get most of the news from rtl-sdr.com. I haven’t done much DXing since I’ve had my ham license…I’ve been too busy tinkering with that.

Oh well, I’m not taking the blog down. The articles I wrote are hosted here. I was down for a couple of days because some nasty thunderstorms took the power out and it was a day or two before I could get the server to boot back up. At least now I know what stops it from booting.

I’m also going to start another page that’s ham-radio related, km4joj.is-a-ham-op.net

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Decoding DGPS with SpecLab, RTL-SDR, & SDR#

Last night I figured out how to decode DGPS signals with the wonderfully free SpecLab. Even though SpecLab can be tricky to use, the setup for DGPS isn’t too horrible and I’ve covered how to do it. If you’re just interested in what you get out of the signals, I have a page with a beacon almanac and a few minutes of a datastream.

Soon, I’ll sit down and start compiling DX Logs of beacons. This is making constructing a more proper LW antenna looking like a requirement.

But yes, make sure to check out the article if you want to know how.

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Differential GPS Beacon Decoding

So I got around to looking up how and what can decode DGPS signals. I believe Sigmira is able to do it; sadly it just crashes whenever I attempt to load it. Some of the other methods looked pretty complicated.

I did however find a program called DSC Decoder which came with a 21 day trial, which would at least get me going to see how feasible it is to decode the signals.

Now, I’m not 100% sure exactly what I’m looking at; I’m still reading stuff on the DGPS format and what exactly the messages are DSC Decoder is spitting out at me. I have no idea what the raw data looks like; I can’t seem to get it from this program (nor would I really understand that either.)

However, I have been able to decode four beacons that are located near me. They’re not the greatest for weak-mode, but I was able to get some data out of a very weak one and some distorted data out of a few others. This machine is pretty noisy in Longwave, so the other might do better.

Either way, it’s somewhat exciting to be able to find something down there that’s not encrypted.

dgpsdec

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Differential GPS Signals

I’ve spoken before about the issues I have with my power supplies and SDR. It’s common knowledge that most SMPS (swiching-mode power supplies) produce sometimes very excessive amounts of RF; both ambient and within the power they generate. It make sense since most of these operate using high-frequency switching.

When I got my SDR, I started seeing these spikes at around 300khz in LW; I largely ignored them because I assumed it was probably power-supply noise. As far as I knew; the only thing in that region were NDBs, which just broadcast an amplitude modulated Morse code (rather than the standard CW mode as hams on HF). The more I listened to it, the more confused I was. I chalked it up to possibly noise or some kind of odd data mode thrown out by the government.

I was close.

Last night while down in the LW band checking out the NDB selection for the evening; I came across those same signals…and I was running on battery mode. It was clear the signals weren’t spurious, but deliberate. I listened to them for a while…it was very clear this wasn’t random..but was some sort of data.

So I made a recording and posted it to the IRC room I hang out in; and someone did confirm that it was in fact some kind of data mode. I got to looking and discovered that NDB’s were the only thing in that region; that differential GPS existed. A little bit of searching and I soon confirmed not only it was DGPS; but also found a list of stations and frequencies, along with the baud-rates at the USCG website.

For those that don’t know, DGPS is an auxiliary signal that a GPS receiver can use to “hack” the incoming GPS signal to give it much better accuracy; on the order of 6 to 10cm accuracy. These signals are in fact not encrypted and if you have a receiver compatible, you can use this yourself. The Cost Guard operates a national network of DGPS stations; many places being within range of a few of them.

So, that explains the odd junk I’ve seen around 300khz for the last 4 months. It’s a government signal, but it’s not top-secret encrypted military stuff. Below is a screenshot showing two of the strongest DGPS stations; as well as an audio recording of one made in USB mode. The one in this recording is the DGPS beacon out of Annapolis, MD; the strongest one I receive. There’s also another good list (that I found while writing this) at the DXinfoCentre (which reminds me, I’ve never made a page of links to resources for this stuff, I’m lazy).  A quick search shows it’s possible to decode them; so I may have to give that a try later. Till then, here’s a screenshot and audio recording (USB mode) of the signal.

dgps

 

 

I’ll get around to updating my Cuba receptions later on tonight; there’s a bit of data I have to pour through and about 45 mintues of IQ recordings I have to export to audio and edit down.

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Hello Cuba!

Maybe it’s the recent solar storms, but I decided to shut down the RFI-emitting laptop and hook the dongle up to the one that makes a more acceptable amount of noise. Boy, was it weird.

Now to be honest, I have no idea what kind of toll my longwire took over the winter; for all I know it could be internally broken in a few places and not the full length anymore. I don’t have an easy way of telling, so at some point it is going to get replaced. I did notice slightly different than usual reception in the shortwave bands; which I’m not sure is the odd propagation, or a involuntarily shorter antenna. I heard a lot more traffic on 41m than usual.

So, back to the AM band. The noise floor with the other laptop down in AM is much lower; partially because it actually has a working battery and I’m running the HIU from a quicky DIY 5v linear regulated power supply. The behavior once skywave started coming through seemed expected at first; but then didn’t. There were a number of stations I was hearing on skywave I usually didn’t; and the usual hangouts in the neighborhood came in…then went out. WFAN 660 out of NYC usually blasts the hell out of me; swamping what I can get of WSM 650’s upper sideband; but it was just barely there.

People, I didn’t even see any HDRadio sidebands!

Here’s what I was hearing, an excess of Spanish stations where I hadn’t heard any before. Usually, there’s some faint CKLW down under some HDRadio noise; but tonight there was no noise and no CKLW, just something in Spanish.

I jumped to the lower end of the band, and there on 530 AM I heard “Beautiful Music”, not quite as horrible and generic as Muzak; but all instrumental covers of tracks in that style. I had no clue what it was…so I started looking. My first instinct was Canada; as I’ve picked up some pretty weak stuff from that direction, plus there’s no commercial broadcast in the US on 530khz. There were about 5 stations licensed on that frequency; and out of the 4 that had any information, none of them fit the description. I came to the conclusion it had to be this little 50 watt station near International Falls. I just had to prove it. I’d seen the a station in Cuba on the same frequency, and did in fact hear some Spanish faintly in the background. It was looking more and more like a 1000+ mile 50 watt skip.

But then I heard an announcer with the music that wasn’t another station come in and mention Cuba. Of course, that’s when I looked up Radio Enciclopedia and found out that; yeah, it did broadcast pretty much what I was listening to. There were a number of threads of people talking about it, mostly from the southern states mentioning picking it up. I made I/Q and audio recordings of some of this stuff; I’ll fire up the other laptop tomorrow, copy all them over, go through any notes I hopefully left myself; and get some samples and more info up tomorrow.

I scanned the lower range again and discovered a couple more stations out of Cuba coming in, as well as a news station out of the Orlando area. There was nothing impressive low-power wise out of anything I picked up; but it was interesting that it seemed most of my reception was coming from the south. I’m thinking it could be from the solar storms we’ve had within the last week or so…but I haven’t really kept up with what that’s doing. I’ve been way too busy studying for my ham stuff.

Which, by the way…is getting closer and closer. With just 10 days till the exam; I’ve seen 100% of the questions for the technician pool at hamstudy.org and had an aptitude of 86%. I’m not sure exactly how the aptitude is scored; but it’s more than enough to pass the exam. I’ve taken 12 practice exams since Feb, usually in chunks with weeks apart, and my lowest score has been 29.

Now, I’m going to cram for the General. My plan is to do like I did before, go through all the questions and take practice exams. I can review which questions I’ve missed. This helps the aptitude as sometimes the first time I’ll see a question is the practice exam.

I’m pretty sure I can do it. The general questions started out pretty tough; but they’re starting to click. At around 30% in, I took, and passed, a practice exam.

I’m not going to go for the Amateur Extra though…that’s just too intense for me right now.

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New SDR# Plugins & What I’ve Been Doing

Happy March, I guess. We just got over a free visit from the Arctic, lots of snow on the ground and single-digit temps; followed by warm temps and lots of melting.

I got an email from the SDR# Yahoo group about two more plugins from Vasili; digital IF filter as well as a new Audio Processor.

After translating the page; the plugins are said to replace both the ZoomFFT as well as the Digital Audio Processor. The Digital IF filter does greatly extend what ZoomFFT gave you; but the biggest advantage is it incorporates a notch filter that can be set by simply clicking on the IF window. The asymmetrical filtering from ZoomFFT remains the same; this adds in-window options. This far, it replaces the IF portion of ZoomFFT as well as the Notch Filter.

AudioProcessor is said to replace the Digital Audio Processor plugin; but not so much. Yes, it allows you to do a bandpass on the audio, and it lets you adjust this in the audio spectrum window. It however does not replicate the inversion or de-emphasis that was in DAP; the de-emphasis worked well on the few AM stations around here that broadcast music in addition to a wider-than-expected bandwidth; plus it actually makes AM sound normal at any bandwidth. It will probably replace DAP for most of your needs; although I’ll still keep it installed.

The only function you lose entirely by dropping ZoomFFT over these two plugins is the FM MPX spectrum. I have no idea who else besides someone like me would need this; I happen to enjoy looking at the spectrum level when fine-tuning a station or seeing if it runs SCA.

Still, these are awesome plugins from someone who has developed many great plugins for SDR#; and for most of you they will probably replace ZoomFFT and DAP entirely.

 

As to what I’ve been doing aside not DXing and not updating the site; I’m working on becoming a ham. Back when I got my SDR I quickly settled back in to listening to hams now that I had SSB capability, and it quickly made me question why I wasn’t on the band talking back to them; aside from that messy morse requirement that used to exist as well as the perceived cost of equipment. Things have changed a lot since I last looked at it; mostly the cost of getting started. Sure, used equipment was around 15 years ago; but I wasn’t too setup for buying a lot of stuff on eBay. But the price on VHF equipment has tanked; $30 will get you a respectable HT unit, brand new. So, that’s where most of my time has gone lately; I’ve been studying the technician and general exams; as well as doing all kinds of research on radios; mostly on the various antenna options and connectors used on various things.

I already ordered my radio; it’s set to arrive in a few days. I’m set to take the test and pass the technician exam; I’m just working on learning general.

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Decimation Drivers Are OK & AM Daytime Snowstorm DXing

Hey guys,

I’ve been sitting around most of the morning, watching it drop some serious snow on my area and playing around with the SDR. I’ve been trying to determine what, if any, snow has on groundwave coverage. That also begs the question as to if the falling snow has any effect or the existing snow on the ground.

At the very least, a few weak stations from the 12/31 DX log are more identifable; such as WGOP. Back in 12/31 I remember barely being able to tell what was on it. Today, it’s different; it’s noisy but it’s actually quite intelligible. I’ll make a DX log for it later. I’m wondering if the snow is having a positive effect on DXing. But WGOP out of Pocomoke City, MD; with a whopping output of 500 watts and a distance of 119miles. 119 miles?!? That’s almost as far as I got with WRDU on FM, and it was putting out like 100kW! Gotta love that groundwave coverage of the AM band! – Full detailed page and audio samples will come later; as well as additional stations I find while the snow continues to fall.

I also have been playing around with the decimation drivers some more; and should probably retract my whole “they’re bunk” statement. The improvement is *very* subtle, but I did in fact notice noise-reduction produces better results when having decimated. Having messed with digital audio, I do have a basic idea of how this stuff works; so hearing an improvement in NR performance is either improvement there, or just a byproduct of smaller bandwidth. If anything they do make the signals MUCH easier to find in FFT thanks to the increased resolution. So, they are in fact worth running from a DXing standpoint.

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The Abscence, LW DXing, and Pirates…aargh!

11 days without a post or update? Yes. Let me explain.

I run this site as a hobby; I make absolutely nothing in the form of any compensation from doing so, that part should have been clear. Being so, when life gets busy, it gets pushed to the back burner.

My DXing habits are…strange. I will jump feet first in to it for a week at a time, then kind of back off. I actually don’t often sit and do purposeful DX logs; that should be obvious by the few numbers of them I have.  So much of what I get on MW is the same old stuff; I actually only go look for stuff when propagation is good.

But, as I said; life had to re-prioritize this to the bottom.

Part of what I’ve been doing the last week and a half is fighting interference. As I mentioned in the past, the 8-bit resolution of the RTL-SDR is a huge hindrance; so the lower you can get your overall noise floor, the better. This is practically impossible with an old laptop with a very noisy power supply.  In fact I may have mentioned the sheer lack of the 3 – 4 MHz range with my main machine; and I’ve come to the conclusion if I want to do some serious DXing; I need to do it with the laptop that has a working battery. The amount my noise floor lowers is AMAZING with that thing on battery.

This holds especially true for longwave; where my floor drops close to 40db and all the spurious junk disappears. How much of an improvement is this? On a good day I could log maybe 3 or 4 NDBs in the Longwave band. Today, I logged 11. In no particular order:

  • GIW
  • CLB
  • DAA
  • EZF
  • GTN
  • DC
  • BDB
  • MSQ
  • CGE
  • RNB
  • NHK
  • APG

No real great distances, maybe one or two hundred miles for GIW; although that’s not broadcasting on the frequency the database said it was. I did once log a beacon that identified as New Orleans; I just don’t remember where it was and it didn’t appear on my logs.

I also jumped on to shortwave before shutting that machine down and looked for some pirates. Of course, unlike any kind of licensed broadcast you have no clue where these are coming from. I made some I/Q of these on the other machine; but the quality was pretty low due to some really weak signals. Channel Z was making what seems to be it’s weekly appearance on 9650khz, and a station identified as WMID was playing some really funky stuff on 6925. After WMID signed off, WEAK Radio was coming through; not sure if it was just swamped out by WMID or if it started after WMID; but it was unusual in that it was a USB transmission where most pirates stick with AM.

We’re getting in to the home-stretch of winter, in a couple of weeks the propagation will begin to change and we’re going to be in store for all new DXing…or a total lack of it.

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Decimation Driver Debunked – Shoutcast Back

Turns out you shouldn’t get too excited about the decimation feature of the new driver. I tested it yesterday; I was amazed by the pretty FFT visuals you now had in the waterfall; a lot more detail and looked like less noise.

Sadly; it doesn’t actually help matters any.

Basically what this driver is doing is moving the existing decimation from before the demodulator to before the FFT. This makes the FFT look pretty; but it doesn’t seem to help reception that much. The stations that were quite noisy before are in fact still just as noisy. This bit of information came from someone who’s really close to SDR# development. Of course, there is some debate as to whether there’s an improvement over combining filtering. But I have to say there doesn’t seem to be. You can find the signals better; but it doesn’t seem to actually improve the SNR a whole lot.

The only real advantage to these drivers are the gains settings; which you could get from the gains mod. So there is still a reason to use this driver. But the decimation feature isn’t exactly that magic improvement we want. We’re still *very* limited by the 8-bit ADC in the unit.

In other news; the shoutcast server is now running on a different local machine; so you won’t get errors when trying to connect or find out it’s status just because the SDR machine in the shack decided to reboot.

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