For the first time in a couple of years, I got all my equipment back online in the WSPR mode. I used to run WSPR primarilly with my little Yaesu FT-817, but this time, I chose to go ahead and use my ICOM IC-735, which isn’t a really all that great at WSPR-ing: it is, after all a rig capable of a full 100W output, and even on its lowest power setting should beam out 10W of power. I’ve also suspected that in comparison to the receiver in the FT-817, it’s a bit deaf: it simply can’t hear weak signals.

Last night I left it simply listening on the 30m band. In previous attempts at WSPR, I could expect to hear signals from a couple of dozen different stations. In the last four hours, I’ve gotten two: NM7J in New Mexico and JQ2WDO in Japan. I think it’s a receiver/antenna issue, since I’m not seeing signals in the waterfall which aren’t being decoded: I’m simply not hearing them.

I’m going to move my monitor up to 20m for the day, and see how that works. But I think some antenna testing and maybe trying my trust FT-817 in its place would be a good way to proceed.

Lots of people have said that RTL-SDR dongles that they have been receiving don’t have ESD protection diodes on the antenna inputs, which makes them susceptible to damage, particularly when you hook larger, gain antennas to them. I had read many notes about the EZTV645 that I bought which indicated didn’t have the BAV99 diodes. I took it for granted that mine wouldn’t. But today, I decided to lever it open (it’s really easy, just stick a thumbnail underneath and pop it open). Here’s what mine looked like inside:

The little protection diode is there, right below the antenna connector. Cool.

I did some other testing with the standard antenna, since I didn’t have the appropriate adapter to really try it with anything else. It picks up fairly strong signals, like this recording I made of the nearby NOAA weather radio station on 162.425Mhz:

NOAA Weather on 162.425

I did a few tests. I unscrewed the tiny antenna from its base, and.. the signal was about the same. That suggests to me that the feedline is probably just about as good an antenna as the “antenna” proper. I pondered for a moment, and then attached an 18″ piece of wire to the base of the antenna mount. This should be about 1/4 wave at 162Mhz. The signal was about six db stronger, with fewer drop outs. Next project: to build some real antennas. High on my list are antennas for the 2M hand band, the 1090Mhz ADS-B aircraft telemetry band, and the 137MHz satellite transmissions. Stay tuned.

Just a brief note: this website has some pretty extensive pictures of the inside and outside of the same model of RTLSDR dongle I bought. It also shows that it does not have the ESD protection diodes in place, so it’s possible you could fry the tuner input by having a static discharge directly hit the input on the tuner chip. I’m pondering trying to get some BAV99s and install one anyway, but I also noted that many others are instead recommending getting this model from NooElec instead. They advertise that they use the R820T tuner, and have the ESD antenna protection in place. I do wish they used SMA connectors instead of MCX, but adapters are fairly cheap. I ordered one just to do some comparison testing.

I’ll let you know when it arrives.

I’ve already got a couple of software defined radios: a nice SDR-IQ from RFSpace which covers up to 30Mhz, and an original Funcube Dongle Pro which covers from 64Mhz to 1700Mhz. I like both, but I must admit: they were fairly expensive. Still, in some ways they have spoiled me for conventional receivers in at least one way: they allow easy exploration of the RF spectrum. Just tune through the bands, looking for signals, clicking to tune. Awesome.

But I’m always on the lookout for cheap gadgets, and there is a recent crop of USB gadgets which (while not specifically designed for radio experimenters) have been recently adopted to put a software defined radio within the reach of many more experimenters. These come in the form of “DVB/FM receiver dongles”. Originally designed to allow you to tune in FM radio and DVB-T (the European standard for terrestrial digital TV), but with the right software can be hijacked and use as a more general radio exploration gadget.

I’m just at the beginning of my exploration of this stuff, but here’s what I’ve done so far.

First of all, I ordered one of the dongles. You should be able to get one for about $20 or so. I chose to get one from Deal Extreme, an interesting Chinese exporter. Based on some misinformation, I chose this EZCAP EZTV645, which was $19.20 shipped. Note: I do not recommend this particular radio. You can probably find a better one. I was misinformed into believing that this radio contained the “Elonics E4000 tuner”, which is generally the preferred tuner to use. Other good tuners are apparently the R820T. This one contains an FC00013, which certainly works, but is generally considered the least desirable and has the smallest tuning range. It would also be good to get one which has a standard MCX antenna connector, to make it easier to replace the absurdly comical antenna that it ships with.

The easiest way for many people to get started on Windows is likely to download SDR#, an open-source C# software defined radio program. On Windows, I recommend downloading the sdr-install.zip file, and using it to fetch all the goodies you need. You’ll then need to run “Zadig” (also downloaded) to install the right drivers, but I followed the instructions, and it worked fine, with one minor caveat: I have a Windows 8 laptop, and the drivers that you need to install are unsigned, so they can’t be installed unless you boot the Windows 8 machine in the special mode that will allow you to install unsigned drivers. Annoying. If you’ve never had to do it before, you can just google for the instructions, I fused this page as a guide, and it worked fine.

I haven’t had much time to play with this yet, but SDR# seems very nice (it also supports my SDR-IQ and Funcube Dongle, so I could in theory use it for all my SDR needs). Here’s a quick screenshot of it tuning an FM station:

You can clearly see the FM signal as well as the Radio Broadcast Data System (RBDS) which the receiver can also use to decode sogn titles and the like. Pretty neat.

One thing that sets these cheap dongles apart from the Funcube Dongle and the SDR-IQ is bandwidth: you can actually set this dongle to receive up to 3.2M samples per second, which means you can decode signals which are too wide to decode on the other radios (like DVB-T) or can search huge sections of spectrum at a time.

I haven’t had much of a chance to do more with this radio yet, in particular, I’ve only used it with its pathetic antenna inside my stucco-house and at work inside a metal framed building, where none of my HTs work very well either, so I don’t know of its sensitivity. But I’ll try to keep you all posted.

The other day I was in Ham Radio Outlet, and while strolling around I noticed a new VHF book published by the RGSB. And for some resaon, it made me think: I’ve got three different dual HTs, and an FT-817 which can work on 2m/70cm, why aren’t I doing more on VHF/UHF? I had a lot of fun operating via AO-51, AO-27 and SO-50, as well as the various APRS satellites, but except for SO-50, those have all gone black, and Fox isn’t due for a few months yet. I haven’t found repeaters to be very interesting overall: the sort of abstract social nature doesn’t seem all that exciting, and they represent little in the way of technical challenge. I like the idea of meteor scatter: I’d need to upgrade some equipment and build some antennas, but that seems reasonable. 2M weak signal SSB is probably something that would only pay off mobile (my home location is in a bit of a valley) but has some construction opportunities in it (antennas and the like). I’ve recently heard of coming Digital TV downlinks from the ISS, but haven’t got a clear idea of what hardware will be needed for reception.

I thought I’d toss is out to my readers: are there any VHF/UHF activities that you are participating in or would like to? I suspect that there are people who would like to have some new ideas, either because of limitations of their license class or their home situation, which may not favor large antennas. I’m also interested in hearing about any Bay Area groups who may do unusual activities on VHF+ frequencies.

This weekend was kind of a loss for computer/geek/rc airplane/ham radio, but it was off the charts fun for me and the missus. We did an unplanned day trip up to the Napa valley on Saturday, and then when I realized that I had left my lucky hat at restaurant, returned on Sunday to retrieve it, and ended up having a great brunch at Brix (yum) and then took a tour of the Bale Grist Mill.

The Bale Grist Mill is a fully restored, water-powered grist mill that grinds grain. We saw the sign on Saturday, and googled it that night, and decided to return on Sunday and see what the tour was all about. It was great: the miller was there leading tours, and spent about an hour talking about the history of the mill, and then allowing us to view all the intricate mechanisms inside that serve to grind grist (the seeds of either wheat or corn) into flour or meal. For a small donation, you can even cart away some of the resulting flour for yourself. Since I’ve been baking bread a bit, I decided to come away with some bread flour, buckwheat, spelt, and some polenta. I’ll let you know how it turns out.

The most interesting thing to me about the mill was how refined the design is. Our guide said that many of the elements for the mill would have been taken from the design published in The Young Mill-wright and Miller’s Guide, first published in 1795 (and available for download at the link!). Its author was Oliver Evans, who received an early (the third, apparently) U.S. patent for an automatic flour mill. It uses the power of water to move grist and grain around through a series of bucket elevators and conveyors. The mechanisms visible at the Bale mill seem rather antiquated to us today, but if one considers the times, they would have been positively cutting edge. The miller, working by himself (perhaps with some “dusties”, or apprentices), could have processed as much as a ton of grain per day. And since lanterns and the like were not allowed because of the risk of explosion, that was just as long as daylight lasted.

It was a lot of fun. If you are in Napa, consider stopping by (and donating money, they don’t receive any state funds anymore). I had a blast.

Like many people, I live in a development with a fairly restrictive HOA. This means that I have to be fairly careful to use largely invisible or stealth antenna setups. Because of a lack of suitable trees on my property, this means that I’ve had fairly compromised setups: I’ve gotten the most use from a simple 40m dipole which probably only averages about six meters in height.

But at least for receive there might be an interesting alternative. PA0RDT has developed a simple active antenna which has intrigued me.

Here is DL1DBC’s excellent description.

This article points out something which may not be entirely obvious until one thinks about it: antennas designed for transmission and reception have different goals. A transmitting antenna is designed for efficiency: to send as much of the input power out as radio energy as possible. In this context, short antennas have a very low radiation resistance, so other losses tend to dominate, and you lose a lot of power as heat. But receive antennas aren’t concerned with efficiency: you really just want to preserve the signal to noise ratio of the incoming signal. As long as the noise generated by the preamplifier is low, it doesn’t actually matter how efficient the antenna is. A short antenna picks up less of the desired signal, but also picks up less of the surrounding noise. So, these antennas can work reasonably well, especially on frequencies where full sized antennas are impractical such as VLF.

PA0RDT has created a simple preamp circuit, including a way to power the preamp through coax so you can easily mount this antenna remotely, say 50 feet from your house, and avoid the electrical noise that dominates many active antenna setups. A very neat solution, and inexpensive.

Some more links: Scott built one, using the more ubiquitous MPF102 and 2N3904 transistors, instead of the recommended but harder to find J310 and 2N5109 transistors.

Peter Marx got an official one that was built by it’s creator, Roelef Bakker:

You can read about Peter’s experience here.

A neat little project. Roelef’s articles (esp. the second one) linked from DL1DBC’s give lots of details. Worth looking at, particularly if you are interested in VLF/HF/shortwave listening.