Wednesday, June 7, 2017

AM Broadcast Loop Antenna

540 kHz to 1700 kHz Loop Antenna

                                                                           
Several years ago, I became interested in medium wave DXing. One of my limitations was the size of my yard, so I developed an interest in tuned loop antennas to compensate, because setting up a beverage antenna was out of the question. I experimented with different sizes of loops, and found that the bigger the aperture, the more gain the loop would have. The tuned loop antenna is also very directional, which allows you to reject, or null out interference from either noise or other stations. Loops are considered bi-directional in that they receive to the front and back, but not to the sides. The tuned loop antenna quickly became my weapon of choice for medium wave DXing.

Recently when the weather began allowing me to enjoy the outdoors, I decided to make another smaller loop antenna from a plastic milk crate I had lying around. I saw the idea on the internet when I observed that someone had used a milk crate for their loop. Click here to see a variety of tuned loop antennas that others have made. Whichever material you decide to make your loop antenna from, just make sure that it is not a conductive material. Wood, plastic, and cardboard seem to be popular materials for loop making. In the photo above, I am using my Sony ICF-2010 to listen to WCCO on 830 kHz. This station is nearly 200 miles south of me, but I am able to receive it with 9 LEDs lit on my signal strength meter while using the loop. There is no direct connection of the loop to the radio, it is inductively coupling with the radio's own ferrite rod antenna. 

If you are interested in making a loop antenna like mine, here are the materials you will need:
120 ft of 18ga insulated wire (I bought a 100 ft spool of cheap speaker wire and pulled the 2 conductors apart)
1 - Plastic milk crate
1 - 15 to 365 pF air variable capacitor (found in many old radios, or a google search to buy one from an internet store)
1 - Tuning knob. Any knob will do as long as it fits the shaft on the variable capacitor.
1 - Tape or wire ties. I used tape to secure the wire while winding, then hot glue when finished.

When you begin to wind your coil, use tape or a wire tie to secure the wire, and leave about a foot of wire. This extra foot of wire will later be soldered to the frame on the capacitor. As you wind your coil, pull the wire snugly and with each turn leave about a quarter inch spacing between each turn. The spacing isn't critical as long as the spacing is consistent.  I wound 21 turns on my crate. This may differ for you, depending on the size of your crate, or the value of you capacitor. If you find that the bottom frequency isn't low enough, you can add more wire to make a few more turns. This will lower the bottom frequency for you.

After winding the coil, you can solder each end of the coil to your capacitor. The beginning of the loop gets soldered to the frame of the capacitor, and the other end of the coil to the rotor solder lug on the side of the capacitor. If you do not have a soldering iron, you can use alligator clips to connect your loop coil to the capacitor as well. I secured my capacitor to the inside corner of the crate with hot glue. I put a generous amount of the hot glue onto the bottom of the capacitor frame, and held it to the crate until the glue cooled enough for the capacitor to stay on it's own. I used enough to get the job done, but not so much that it interfered with the plates in my capacitor. The hot glue seemed to adhere very well. I then checked the spacing of my coil turns, and secured them with the hot glue as well.

I was very impressed with the results after spending some time with the loop. It's small enough to maneuver around easily, but big enough to give it some gain, so I can listen to daytime dx. I may make another tuned loop using two crates to see how much more gain I get with the larger aperture.

Happy DXing,
James Townley

Saturday, December 10, 2016

Eton E1XM Review


I purchased my Eton E1XM from National Geographic for $225.00. My first radio had the issue with the line down the screen. I contacted them, and they sent me another E1XM. I've had it now for nearly 10 years, and it has worked flawlessly. The E1XM was plagued with issues dealing with quality control, and it has never been given the respect it deserves. I feel lucky to have one that has no issues.

I have used several receivers over the course of the past 35 years, and have a pretty solid idea of what I would expect from a receiver. Sensitivity, selectivity, audio, and ease of use are of my most important factors. Some receivers are considered to be very sensitive, but if the audio is distorted, the overall quality of listening is hampered.

The E1XM started out as the Grundig Satellit 900, and was supposed to be the next flagship of the Grundig line. I used to thumb through magazines and books wishing to own the Satellit 500 and the 700, but at the time I could never afford them. When news of the 900 came out, I was like a kid at Christmas time eagerly awaiting it's arrival. There were rumors of it's arrival each year, but it never happened. Then suddenly it was announced that Eton would release the Grundig Satellit 900 as the E1XM. The original price was $500.

As a radio enthusiast, there are several aspects that are important to me. Sensitivity, selectivity, audio quality, frequency range, and ergonomics are at the top of my list. There are other deal-breakers for me, and your list may be different than mine, but these aspects are what determines how much I will use a radio after dishing out the money to purchase it.

I don't use my E1XM as a portable radio. It sits near my desk connected to a power supply, and a Wellbrook ALA1530 loop antenna which is mounted approximately 60 feet (20 meters) from my house. I have occasionally taken the E1XM on camping trips, and over-night hotel stays, but mainly I use it as a desktop receiver.

The sensitivity of this radio is as good, if not better than, any of the other radios I've compared it to. On a nightly basis, I have three receivers operating at the same time. Currently they are the Yaesu FRG-7, the SDRplay RSP1, and the E1XM. I also have a Sony ICF-2010. Comparing very weak signals with all of these radios, I often find that the E1XM will produce a signal equal to, or better than any of them. I often find myself listening to pirate radio stations, and some of them can be a challenge to hear with any radio depending on atmospheric conditions and interference. Comparatively, the E1XM makes these weaker signals more comfortable to listen to in my opinion.

Selectivity is the ability of a receiver to block adjacent signals, so they don't interfere with the signal you are attempting to listen to. The E1XM does a great job in the selectivity department. It has three filter settings 2.3, 4, and 7 kHz. Depending on the situation, I feel that these bandwidths are adequate and work very well when trying to reject offending signals. Pass band tuning is another feature that comes with the E1XM and it works very well. PBT is a feature that is rare to portable radios, but it comes with the E1XM and is a very handy tool to have. I find myself using it to eliminate annoying whistles and other noises that interfere with what I'm attempting to hear.

Synchronous detection circuits very from radio to radio. The E1XM allows you to choose from lower sideband, upper sideband or double sideband. I keep mine set in the double sideband mode. I have found that while I am happy with the performance of the sync feature in the Sony ICF-2010 and the 7600gr, the E1XM's sync is superior in how it appears to reduce the fade and distortion of am signals compared to other receivers with this feature. The effect is more dramatic when the E1XM locks in compared to other receivers I have known.

On the E1XM the auto gain control (AGC) has three settings: Slow, Fast, and Auto. I keep mine in the auto position, which allows the receiver to select between slow and fast. While other portables also have this feature, side by side comparisons have proven to me that the E1XM does a better job at stabilizing  signals during conditions where there is deep rapid fading.

Audio in receivers can be the determining factor in whether the target signal is intelligible or not. The quality depends on the type of circuitry and the quality of components. The speaker used and the size of the enclosure are also factors. I have found that the capacitors are very crucial to the sound. Different types of capacitors charge and discharge at different rates. This can severely affect the sound that the receiver produces. Cheap capacitors can cause distortion to varying degrees. They can cause speech to sound slurred. For example an S can sound like Shhhhh, or a J can sound like Chhh. I have replaced capacitors with higher quality capacitors and found that the improvement can be very dramatic. The new capacitors produced clearer audio and brought very weak signals out of the noise, or at least made them easier to decipher.

On the E1XM, there are individual controls for bass and tremble. This in conjunction with the PBT, Sync, and the bandwidth features, make this radio very enjoyable to listen too. The audio with the internal speaker is among the best I have heard in a portable radio. This is of course a personal preference, as we all have slightly different tastes in sound. With the various controls, you can tailor the sound to meet your needs. I have found no need to replace the capacitors in my E1XM, as the audio is very pleasing to my ears.

I quite enjoy the overall appearance of the radio. It has a neat Art Deco look to it. The display is very large and easy to read. There are three levels of brightness, and a contrast adjustment, so a person can adjust the display to their own preference.  There is an exhaustive amount of memory for your presets that can recall the entries alphanumerically with the desired settings for each entry. I think you can store up to 1700 entries. I rarely use the memory functions, because I find it just as easy to enter a frequency and go there. With the E1XM you simply enter the frequency, and after a second, it automatically sends you there.

The E1XM has some downsides to report in an attempt to be fair. First, they designed this radio without an internal ferrite rod antenna for MW and LW. Surprisingly the telescoping antenna works well, but it isn't as effective, because it is not directional like the standard ferrite antennas are. Second, initially I liked the rubbery feel of the radio that gave you something to grip, so it wouldn't slip out of your hands. In time the surface began to get very sticky. I used rubbing alcohol to rub the tacky surface off of it, so it is no longer an issue. Other than these two issues, the E1XM has surpassed my expectations.

The Eton E1XM was issued to the public in 2005. I have used this radio on a daily basis for the past ten years now, and while I have taken very good care of it, there is very little sign of use. I wouldn't bounce this radio down the street like a basketball, but if I keep it clean and continue to care for it, the E1XM should last for several more years. The radio feels solid when I hold it, and seems to be very well constructed. My only regret is that I didn't have the foresight to buy two or more of them at $225.00. Now, they go for higher than $600, and it's rare to see one for sale.







Wednesday, July 13, 2016

General Electric p780 E


I picked up this GE P780E radio from eBay. It was made in 1960 right here in the USA. I updated the electrolytic capacitors, sprayed some DeOxit in the volume control - power switch, re-attached the large ferrite core antenna (the plastic clips had long since rotted and broken) and polished it up. 

Some have said that this was the finest solid state AM radio ever made. This radio was designed to sound like a tube radio with it's eight transistors. The antenna is a very large ferrite rod 5/8 inches thick and approximately 7 inches long. Behind the solid metal grill, is a 5 inch speaker. In conjunction with the tone control, this radio has a real full and warm sound to it. The case on this radio is a chrome covered metal with the back of the case being an AVS type thick plastic. With the six D cell batteries, this radio weighs around 12 pounds. This is a very solid and durable radio.

I was amazed at the number of daytime stations I was able to tune in. WCCO is 200 miles from me, and I was able to listen to their station without having to strain too badly. Overall, I am very pleased with this radio.


Monday, June 27, 2016

SDRplay & SDRuno

Recently purchased SDRplay and am using SDRuno to control it.












I have given other SDR control software programs a try, but SDRuno is now my favorite