Posts Tagged ‘Shortwave listening’
Shortwave radio has been a source for great sci-fi plots, spy intrigue novels, movies, and so on, since radio first became a “thing.” But, what is the big deal, really? What is it that amateur radio operators listen to?
In this video, I share some of the types of signals one might hear on the high frequencies (also known as shortwave or HF bands). This is the first video in an on-going series introducing amateur radio to the interested hobbyist, prepper, and informed citizen.
I often am asked by preppers, makers, and other hobbyists, who’ve not yet been introduced to the world of amateur radio and shortwave radio: “Just what do you amateur radio operators hear, on the amateur radio shortwave bands?”
To begin answering that question, I’ve taken a few moments on video, to share from my perspective, a bit about this shortwave radio thing:
Link to video: https://youtu.be/pIVesUzNP2U — please share with your non-ham friends.
From my shortwave website:
Shortwave Radio Listening — listen to the World on a radio, wherever you might be. Shortwave Radio is similar to the local AM Broadcast Band on Mediumwave (MW) that you can hear on a regular “AM Radio” receiver, except that shortwave signals travel globally, depending on the time of day, time of year, and space weather conditions.
The International Shortwave Broadcasters transmit their signals in various bands of shortwave radio spectrum, found in the 2.3 MHz to 30.0 MHz range. You might think that you need expensive equipment to receive these international broadcasts, but you don’t! Unlike new Satellite services, Shortwave Radio (which has been around since the beginning of the radio era) can work anywhere with very affordable radio equipment. All that you need to hear these signals from around the World is a radio which can receive frequencies in the shortwave bands. Such radios can be very affordable. Of course, you get what you pay for; if you find that this hobby sparks your interest, you might consider more advanced radio equipment. But you would be surprised by how much you can hear with entry-level shortwave receivers. (You’ll see some of these radios on this page).
You do not need a special antenna, though the better the antenna used, the better you can hear weaker stations. You can use the telescopic antenna found on many of the portable shortwave radios now available. However, for reception of more exotic international broadcasts, you should attach a length of wire to your radio’s antenna or antenna jack.
I’ve owned many of the classic shortwave receivers throughout the roughly 40 years that I have been a SWL. Most of these I passed on to friends and relatives, while others were sold at hamfests, and on eBay. I know that my beloved Panasonic RF-2200, is still used by my sister-in-law Alice. My late brother Paul kept it prominently displayed on the counter for years. My Sony ICF-6500 lives in Wisconsin, in the hands of a good friend that wanted to get in to shortwave listening. Others, I’m not so sure as to the whereabouts, but hopefully they are still in use (with exception given to my National HRO-60 which I know was lost in a flood).
Of all of these, the one I frequently regret selling was my Sony ICF-2010. The 2010 is still considered to be one of the best portable shortwave receivers around, and rivals many tabletops. I sold mine on eBay during what we’ll call a dark time in my life a number of years back. I purchased the 2010 new at Gilfer Shortwave in NJ, in-person. Now, as I see working examples sell for upwards of $350 on eBay, I have relegated the replacement of this radio to a status of someday, along with several other things that I want but do not need at the moment. It would be a nice addition to my collection though, considering it is a great receiver. It has a synchronous detector, separate USB/LSB modes, and 100Hz resolution, and portability.
Last week while watching new postings on eBay I saw one come up. This example was listed as for parts or not working. Upon reading the description, I noticed that the seller indicated the radio to be completely dead. Now, in the world of radio repair, completely dead is usually better than many other states of being. Especially in the case of the 2010, which is known to have battery compartment issues. Anyway, I grabbed the radio immediately for a VERY reasonable price. It arrived last night, and as I suspected, the problem was battery compartment related. The 2010 runs on 3 D-cells, and 2 AA-cells. The AA cells are listed as the computer batteries. One thing about the 2010: If you want to run it on AC power alone, you still HAVE TO have the AA-cells in place. One of the plastic supports for the AA battery contacts had broken from the housing. It is still held in place with a ribbon-
sized piece of plastic though, causing it to tilt at an angle back and forth like a loose tooth. I temporarily fixed it with a piece of compressed foam and some plastic tubing. The radio works great! Better I think than my early example from years ago. I have a couple of questions for the radio community though.First of all, what should I glue the AA-cell support back in place with? I would try crazy-glue (or any generic cyanoacrylate), but I know that it will sometimes react with some commercial plastics, making the problem even worse. I was thinking of using Gorilla Glue, but I would need to devise a clamping method. I know some of you out there have dealt with such things before. What do you use?
Second, the radio arrived with a loop antenna of some kind. I have put pictures below. It is approximately 21 inches long, made from PVC pipe with two endcaps. On one end is an F connector and on the other end, an eye-hook. I scrounged in my adapters and was able to hook it up. It definitely improved reception on a few bands. Has anyone seen one of these before? Is it a commercial product, or homebrew? What is the bandwidth? And, if no one knows, what is the best method for determining its properties? Feel free to answer in the comments.
I built this antenna a few years ago and it is about time I posted details about it on this blog.
This is a small loop, that is the length is ≤0.1 of a wavelength, and designed for receive only, not transmitting. The loop is a little more oval than round with the narrower diameter being 36″ and the wider diameter being 40″. A transformer is used to collect the signal and pass it via coax to the receiver. The antenna shown and described here tunes from around 3 MHz to 18 MHz. So it covers 80m through to 20m and of course the broadcast bands in between those frequencies too.
The schematic of the loop is shown below.
The main loop is composed of ¼” copper tubing (available from hardware and plumbing stores). The advantage of this type of tubing is that is easy to bend into a set shape and it maintains that shape with just a few fixing points. If a wire loop was to be made it would require some sort of frame to retain the loop shape.
The capacitor is a variable capacitor from a receiver. I have not measured the capacitance but I suspect both sections together give a maximum of 300 to 400pF. To increase the range of the tuning of the loop I included a switch to allow either one or both of the dual stage capacitor to be included in the loop. The picture below shows the top mounting of the loop, the variable capacitor and the switch. To make easy connection to the capacitor, the copper was squeezed closed at the ends and holes were drilled for bolts. Ring or spade-end connectors can be used to connect wires from the capacitor to the copper tube, and held in place with nuts and bolts.
Note that the copper ends of the loop should not contact each other. They are close in my loop, because of the cable tie mountings on the pine wood, but they do not touch. Electrical connectivity is through the capacitor. To prevent any ‘hand capacitance’ effects when tuning (and hence tuning issues) I added a non-conducting shaft on the capacitor (you can see the brass shaft connector). In my loop the two capacitor sections are joined in parallel to increase the capacitance. The switch can switch out one section, so decreasing the minimum capacitance and increasing the upper frequency that can be tuned. A single stage capacitor, without a switch, will do fine, but the higher the capacitance the better.
At the opposite end of the loop a T50-43 toroid has been threaded onto the copper tube. The toroid has five turns of enameled wire wound on it and it slides easily over the copper. The copper loop now makes one turn on the loop and the five turns of wire on the ferrite toroid makes the transformer (as shown on the schematic). This arrangement can be seen below.
The enameled wire ends have had the enamel removed (only the ends) and have been tinned with solder before inserted into the electric wire block, which allows connection to the RG-58 cable. At the end of the cable add whatever connector you need for your receiver. The photograph also shows the simple L bracket arrangement for holding the pine plank upright on a simple plinth (a small piece of off-cut maple) large enough to stop the loop from toppling over..
The use of the electric connector block is not ideal I find (the enameled wire is too thin) and in future I will probably make something suitable out of some unetched copper circuit board and solder the wire and coax directly to the board.
I am sure there is room for experimentation with the type of mix of the toroid, as well as the number of turns of the enameled wire. My loop worked satisfactorily so I left it as it is.
How does it perform? Well I find it always surprises me how well it works for about 10ft of copper tube in a loop, a capacitor and a transformer. I use this in my basement and can easily tune in stronger stations on the bands. The high Q of small loop antennas rejects strong out of band stations that can bleed-through in more conventional random wire or even dipole antennas, so improving reception performance. When using the antenna you must tune to the frequency or band of interest and then adjust the loop’s capacitor to tune the loop to the same frequency. You will hear either a rise in signal strength of a station or background noise if there is no station on frequency. It is simple to use and it is surprising how it can increase the received signal.
Below are a few recordings made using the loop antenna. The receiver was the old but excellent Yaesu FRG-7, which for the purpose of this demonstration serves well as a general good receiver, although as you will hear the filtering is wide (‘barn-door’ wide springs to mind). For each of the recordings I tuned the receiver to the required frequency and adjusted its pre-selector for maximum signal. What you will hear in each case is the signal and then I will detune the loop one way, then tune it back through the peak to the other side and then returning to the peak of the signal. Recordings were made with an MP3 recorder place in-front of the receiver’s speaker, so you hear what the listener would hear. You should remember this is a 10ft circumference loop in my basement, NOT 100+ft of wire 50ft off the ground.
Small loops are directional to the signal source so if you use one you should experiment by turning it. It may be the HF frequency, or the fact that my antenna is below ground level, but I have noticed not too much of a difference when the loop is turned in orientation. That said, other small loops I have built for the AM broadcast frequencies, or medium wave, do show a stronger directional nature.
If you want to learn more about small loop antennas I recommend Joe Carr’s Loop Antenna Handbook, published by Universal Radio. That book describes many loops, both large and small and is well worth the read if you enjoy antenna design. This loop design is not from the book, but I used concepts and theory from it. The idea of using the copper tubing and the toroid transformer slid onto the copper was my own, although it may not be a novel idea and could have been reported before.
Let me know with a comment if you build and experiment with such an antenna. Share your findings with other readers.
Before this blog I had a web site with some amateur radio information. It is still out there, but I should close it down or update it totally. Here is one of the projects from those pages which I had great fun with and which is worth adding to this blog. I was quite impressed with the quality of the audio from this receiver which has just seven components (three capacitors, two transistors, a resistor and a transformer). Below is an edit of what was originally written a few years ago.
I constructed this simple receiver having seen the circuit at WB4LFH’s web site which he calls the ‘audion’. This circuit is almost identical to the last circuit on that page, except I changed the inductor connection to the variable capacitor from being a tapped connection to being a transformer coupling.
The inductor was a T50-2 toroid with secondary being 28 turns of enameled copper wire and the primary (connected to the antenna) being two turns. (Remember a ‘turn’ on a toroid is the passing of the wire through the hole). The transistors were 2N3904 types, but you can try any general npn transistor. The tuning capacitor was a air plate type taken from an old radio receiver, likely about 300pF. The circuit was constructed ‘ugly style’ on a small piece of unetched circuit board. Use what you have in your junk box and experiment.
The performance is very good considering the simplicity of this receiver. Below are a set of sound recordings from this receiver. The recordings show how the volume can change (no AGC here!) and that the selectivity is not too good.
If you consider building this receiver please note that these recordings were done with the receiver connected to my external antenna at that time, a G5RV. I tried using a long whip antenna, which I had in the junk box, and there was no discernable reception of a signal with it. So you will likely need to use a good length of wire to act as an antenna. Post a comment if you have any success with this circuit.