Improved NOAA-19 Reception

Improved NOAA-19 Reception

This week, my ebay ordered RTL2832U based USB digital TV receiver dongle arrived! I’ve been working through a bit of a cold, but that wasn’t going to stop me going down to the garage and having a play. I was too excited at the possibilities!

With no time at all I had my RTL-SDR solution up and running with SDR#. All that was needed was a custom driver install and then a couple of very minor mods to SDR# and all was working. Other than that, I connected the antenna socket out via my access panel to the Diamond X-50 on the roof. Before I knew I had local WFM radio stations playing on my computer.

The main purpose though for even trying all this, was the hope that it’d improve on my weather satellite reception as per my previous attempt. My thinking was that the main limiting factor was the narrow bandwidth of my receiver.

With using an SDR setup, I should be able to have as wide a bandwidth as needed (and more if wanted). However it required one extra bit of software, and that was a virtual audio cable to route the audio out of the SDR software into the audio in of WxtoImg. For this I chose VB-Audio Virtual Cable. It’s free and couldn’t be easier to use.

NOAA-19 @ 0446 UTC - Both Channels

NOAA-19 @ 0446 UTC – Both Channels

After getting past some recurring computer freezes (think I need to rebuild my PC) I was able to play with an initial pass to play with some settings. But before even changing anything things were looking drastically different. Then on turning the gain in SDR# up full and increasing the AF Level slightly things were looking (to my eye) perfect!

So with all trimmed and ready to go, I  keenly awaited 0446UTC for the next NOAA-19 pass. The results were amazing – the best by a long shot that I’ve every received. These can be seen in the first NOAA-19 image with both channels,  and you’ll notice only a few spots of noise which I believe was mainly due to physical obstruction.

To consider this was achieved with essentially a $25 receiver and some free software is amazing. Considering further I’m still just using the Diamond X-50 and haven’t even bothered to consider the circular polarisation. And further, this was from the West were I do have far less of a view – South/East is the preferred approach.

With that success, what now? Well, I’ll keep trying some more receives (hopefully my PC will stop freezing) and I might try some of the other SDR# features/plugins so that I can attempt to switch frequency for each of the three active NOAA satellites. That way I can aim for a full set of images!

Further, I’m also interested to see how some of the other SDR software offerings go and then I can also start to look at all the other possible items to receive out there – considering this dongle (with the FC0013 chip) covers from just below 30MHz to just up over 1Ghz. So many options! Oh, and then there’s the idea of an upconverter for all the offerings below 30MHz!

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SOTA Australia – VK1NAM Blog

Summits of the Air seem to have really kicked off with a gusto in Australia, and it’s great to see. I’m really looking forward to when VK7 is up and running – if only I had more time to help with peak identification. In the meantime, I’m reading the yahoo group and will hopefully get my home 40m antenna up so that I can at least do some ‘chasing’.

Out of all this activity the dedicated SOTA australia blogs are starting to come about. One that I’ve found very impressive is that of VK1NAM. It seems highly active with lots of photos, maps and details. I recommend having a look over at:

http://vk1nam.wordpress.com/

YouTube: Transistor Tutorials

Found some nice transistor tutorials by AllAmericanFiveRadio that seem to be reasonably well put together.

First is one on some biasing basics:

And another still a bit on biasing, but more so on small signal amplification:

One thing I took from this was that it’s good to just get out there an experiment with transistors. It’s one thing to first learn all the theory, but sometime some good ol’ hands on can be useful. I need to go and have a play.

Another CPO: Cheaper Beeper

I’ve been busy plugging away at my DDS/Arduino/VFO for 630m (more on that later), however yesterday I came across a neat little circuit for a code practice oscillator.

Cheaper Beeper CPO

Cheaper Beeper CPO

I’ve still got my previous CPO, however the simplicity of this one appealed to me. It’s two transistors, two resistors and a capacitor. All on a small piece of perf board.

In the image above, you can see the 9V battery connector. At the bottom are the two wires for audio out. And then in the middle there will be two more wires for the cw key. My plan it to mount it all in a small box with two 3.5mm mono ports – one for audio out and one for the key. That way I can either feed the audio into my computer for practice or into a speaker.

Close-up

Close-up

I’m thinking I may still build another CPO yet, as I really would like one with a sine wave – the square wave is a bit harsh and annoying. Plus, one with a sine wave I could wire into my FM rig for some code sending practice – if I find someone else so equipped. (I think sending the tone of these guys over the air would probably drive me and my practice partner nuts – not to mention anyone listening!)

Anyway, if you’d like to build one of these little guys yourself, the instructions can be found online here at the ARRL website. However, a word of caution.

There is a minor error in the schematic. If you’re rushing through trying to build the thing up quickly after work it may bring you unstuck – as it did to me. The PNP transistor in the schematic is marked as a 2n3904, however it is in the parts list as a 2n3906. Now a quick check would show that the correct one is the 2n3906, but if you just look at the schematic and go barging in blindly, well it wont work.

Anyway, enjoy! If you build one up send me a photo! 🙂

Sacrificial transistor - should've checked.

Sacrificial transistor – should’ve checked.

YouTube: 4-bit Computer

This is an interesting and informative video on a home built 4-bit computer using discrete components to demonstrate the theory.

It’s presented at a rapid pace, so it’d be great to pause and take bits in and really understand them. But I’ll add that to the list.

Enjoy!

Dongle SDRs

With my recent attempt at NOAA weather satellite reception, I’m keen to get a receiver that has support for WFM. Having such would in theory allow me fair better reception – as APT uses 32kHz bandwidth and then there’s also doppler shift to accomodate for (which WxToImg does itself, if you’ve got enough bandwidth). Currently, my Yaesu radios only have support for NFM on 137Mhz and thereby only around 9kHz bandwidth.

A solution for this would be an SDR receiver that covers VHF. There’s been a lot of coverage in magazines lately (namely Silcon Chip and Practical Wireless) on the use of DVB-T/DAB+ dongles for SDR. With these being so cheap (delivered from eBay for ~$30), this definitely looks like a good starting place. If you’d like to know more on this, than simply look up RTL-SDR or start at http://www.rtl-sdr.com/.

However, for it’s price the FUNcube Dongle really appeals compared to some other dedicated SDR offerings. With LF to UHF coverage it’d be great for both work in the 630m band as well as most other amateur bands, and then also for doing weather satellites. (Unfortunately the RTL-SDR idea will only provide for VHF and UHF, however it also about  20% the price).

Here’s a nice video on the FUNcube dongle:

But that said, as a starting point the RTL-SDR (especially at it’s price) will be where I’ll start with attempting to improve my weather satellite reception. And hopefully in the future, I’ll grab a FUNcube dongle. I found these two videos interesting for a comparison of the two options:

Part 1:

Part 2:

The Reverse Beacon Network

I remember a few years back hearing about the Reverse Beacon Network in a presentation given at CRARC. At the time I recall it seemed interesting, but then I was sidetracked by something else before I looked into it.

More recently I heard it mentioned in a discussion around (I think) the QRP Hours Contest on vkzlqrp mailing list. That got me thinking more and so I started reading and pondering.

RBN Home Page

RBN Home Page

The RBN is a simple idea, but like many simple ideas it’s a great one. People run their receivers (ideally SDR ones for wider bandwidth coverage, but even just a normal SSB receiver) feeding their input to their computer as they would for digital modes. Then they run CW Skimmer which monitors for CW signals – and specifically CQ calls with a callsign. Once these are detected, another piece of software (the RBN Aggregator) is used to feed these into the RBN network.

The ultimate result of all this, is that you can jump on a band of interest and send out a CW CQ call and see where in the world you’re making it to. Not too different to WSPR, however using an actual mode that you also use for QSO’s. Indeed, even people with no interest in RBN will still be detected just as a matter of using CW. In affect, it’s an automatic spotting database for CW.

So having my Softrock sitting around not doing much, I wondered about the potential of setting up and giving this a go. I still don’t have my HF antenna in place, but I do have my mini-whip. It seemed like a possibility.

I looked into CW Skimmer more and it looked straight forward enough. The only problem is that it’s commercial software. That is, after a 30 day trial period you have to pay – and not just some spare change. But at least with the 30 days I could see how it was and decide whether I wanted to do this long term and if so then consider paying. I do however, mean to do more of a search to see if there are any alternatives – but so far it seems not (and that’s possibly why there’s far fewer listeners on RBN than WSPR).

After downloading CW Skimmer and having a play, the following night I downloaded the RBN Aggregator and went about setting them up in unison. It was pretty straight forward, although the Aggregator has  changed it’s UI since the instructions on the website, and I did change a field only to find it would hang. But if I had of gone with the defaults it would have been a pretty simple affair.

VK7IS RBN Spots

VK7IS RBN Spots

To my amazement, in no time at all I was loading spots up to RBN. Albeit, I did have a couple of hiccups.

Firstly, my I/Q settings for my Softrock were back to front in CW Skimmer – so all my initial spots were around 7080kHz rather than 7010kHz. Secondly, I now know my Softrock is about 200Hz off, but I was able to fix this by adjusting the centre frequency in CW Skimmer.

Now, all appears to be going well. So the details of my setup are:

  • Receiver: Softrock Lite II (40m) – Listening to 96kHz with Audigy 4 sound card
  • Antenna: Mini-whip
  • Software: Windows XP SP3, CW Skimmer and RBN Aggregator

If you’d like to, you can view my spots on RBN. Hopefully I’ll be running for at least the next several days – depending on what else I’m doing. And whether I’ll do it long term, I’ll need to ponder whether it’s worth paying for CW Skimmer.

As you may see, I’m currently the only station listening from VK and there’s only one over in ZL. It’d be great if there were more down our way. I know of one other in VK1, but he’s currently moving house so is temporarily offline. I encourage people to give it a go – especially when you’re setup’s not in use.