Tag Archives: Stupid radio tricks

How-to: Aluminum case for new RTL-SDR blog brand TCXO dongle

The RTL-SDR Blog posts articles and links related to software defined radio. They also sell RTL-SDR dongles and accessories. Last month they introduced a dongle with a temperature compensated oscillator (TCXO). This virtually eliminates the well-known offset and frequency drift of “standard” dongles as they heat up or the ambient temperature changes. NooElec also makes a model like this, but if you don’t like the MCX connector on the latter, the RTL-SDR Blog version uses an SMA connector (and is a bit cheaper at the moment). Both brands are good products in my experience.

The RTL-SDR Blog does not sell an aluminum case for this dongle (yet), but once you get past your first RTL-SDR experimentations, this is a must have. A metal case shields the dongle from RF interference and provides a better ground plane. It is a fairly straightforward mod to get the RTL-SDR blog dongle to fit in the RTL-SDR case sold by NooElec.

Disclaimer: you can potentially ruin your RTL-SDR dongle, so attempt this at your own risk.

Tools needed: sandpaper, small metal file, small phillips screwdriver, power drill, hammer and hole punch (optional)

Here is a picture of a modified case and an unmodified case, plus the file I used, and the dongle removed from the plastic case it comes with:
IMG_1574_case_blowup

I did not take a picture of an unmodified dongle, but you want to sand down the long edges of the PCB just enough so that it fits on the rails in the case. Normal fine grit paper works fine. Also, you can sand down the PCB that sticks out from where the USB plug is mounted. Do not sand too much or you can hit conductive traces and/or solder points.

Using the file, etch smaller slots on the short sides of the existing USB slot in the case. You might also need to file down one of the long sides of the main slot to allow the plug to vertically fit. You want to do this fairly precisely to avoid creating a large hole for RF interference to leak in, so trial and error is the best method.

On the other end cap, you will drill a 1/4″ hole for the SMA plug. Note that a commercial case might have a square hole to accommodate the lip of the plug, but that it not necessary. It just means that the USB plug will stick out a couple millimeters more than usual on the other end. Use the slot end of the case as a template to determine where to drill the hole. A hole punch can be very helpful here to mark the hole location to keep it in the same vertical plane as the rest of the dongle and USB plug.

Some people claim that the paint on the case can cause electrical problems, i.e., the case will not be a unified ground plane. So, before you put the case together, use the file or sandpaper to strategically remove paint where the case pieces fit together. This does not have to be precise.

You can fill the MCX hole in the case with a short screw and nut to prevent possible RF interference from entering here.

Here are a couple shots of the end product (a little blurry, but you get the point):
IMG_1571_USB_end

IMG_1572_SMA_end

I’ve had this running for about 20 hours total since I made the mod and it works fine.

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Gear: Pattern test of AM BCB tuned loop antenna

I’m impossibly behind in my posting of DXing sessions and AM station recordings, so I’m not sure how I’m going to take care of that.  But, I hope to make several posts over the next month or two on antenna testing.  To start this off, I did some formal pattern testing of my 6-foot tuned loop antenna this morning.  Ideally, one should do this at high noon, but the testing was 2 to 2.5 hours after local sunrise, and all of the skywave signals seemed to be long gone by that point. Continue reading

Gear: Antenna experimentations

I still owe a long post on the details of building wood-frame tunes loops, but I have to put together all of the various photos, instructions, etc. One of the problems with these loops is that their figure-8 reception pattern means that if there is a strong station 180-degrees from the weaker station you want to hear, you are stuck. However, there are various ways to get a different reception pattern. The down side is that many of those antennas require a lot of real estate and need to be supported in special ways. Continue reading

First post: All WWV frequencies in 35 seconds

I plan to start posting regular listening logs soon, but I’ve been traveling and have had some other stuff going on.  As a teaser, here is something neat regarding time signal station WWV out of Fort Collins, Colorado (and WWVH out of the island of Kauai, which I often hear underneath the main WWV signal and sometimes as strong as WWV). Continue reading