Over the consecutive holidays of January 9-10, Radio Siesta-san, Shinzo-san, Hanabusa-san (These are their nicknames.), and I conducted a medium wave DXpedition at a villa with a large garden facing the Pacific Ocean in the Boso Peninsula, Chiba Prefecture. The day was blessed with good conditions and we received many Australian MW stations. This time, We set up a 20-meter-long delta loop antenna array which I deployed in November last year. The antenna was directed to South. We enjoyed MW DX reception from late Sunday night on Jan.9 to early Monday morning on Jan.10.
We met at Kawasaki station and headed for the site by a car driven by Hanabusa-san. On the way, we stopped for lunch at Kamome Shokudo (Kamome Restaurant) in Kisarazu City, where we had conger eel tempura(Fried conger eel) rice bowls. Needless to say, the portion was huge. So it was hard to reach for the meals at the supermarket where we stopped to buy our midnight snacks because we were full after eating the conger eel tempura rice bowl.
穴子天丼:Fried Anago(Conger eel) rice bowl(Click to enlarge)
Upon arrival, we immediately started setting up the antenna. The antenna we set up in the south direction was the aforementioned 20-meter-long delta loop antenna array. This antenna is made by placing two loop antennas in a straight line, changing the phase of the signal between both feed points by 180 degrees, and then adjusting the phase of the loop antenna in the direction where we want a null pattern. For the phase adjustment, I used about 15 meters of 50 ohm coaxial cable. A transimpedance amplifier using LMH6702 is mounted in both feed section to convert the current induced in the loop antenna into voltage. By using this amplifier, a flat antenna gain characteristic in the band is realized.
System diagram of the delta loop antenna array (Click to enlarge)
Antenna Pattern (Vertical Pol. @1MHz)
Installation of the delta loop antenna array(Click to enlarge)
DC distribution box, 50ohm power combiner, delay line and CMC (Click to enlarge)
The cottage we used this time has a solar power system on the roof, and the control panel of the power combiner showed that it was working during the daytime. Unfortunately, during the daytime, the noise from the power combiner of the solar power generator was so strong that we could hear a noise like a cry of Chinese muntjac all over MW band. I wanted to turn off the power combiner, but I couldn't contact with the owner of this rental villa at that time. However, as soon as the sun went down, the noise completely disappeared, and after that, we could only hear a light electric static noise, almost free from artificial electric noise. This was an ideal situation for MW DX. I've been DXing in many different places, but it's hard to experience such a quiet noise environment.
Now, I would like to share you my reception logs. Since I am not familiar with Chinese or Southeast Asian languages at all, I specialized in logging English stations. I was able to hear 79 English stations, excluding AFN in Japan. It is truly an extraordinary situation to hear so many English stations like this and I think it is the best part of MW DX. The log can be downloaded fromhere(click)
Now, I would like you to listen to several actual reception sounds. Some of you may not be familiar with MW DX, so please put on your headphones and experience what we were receiving. I hope you can feel the extraordinary nature of MW radio waves propagating from thousands of kilometers away. I chose audio clips that is relatively easy to listen to. Enjoy!
(1)ABC 4QD 1548kHz, 50kW Emerald, QLD, Australia at 16:00UTC on Jan.10
This is a familiar regular station in Queensland of Australia that can be received in MW DXpedition. It is possible to receive this station inland, but it is rarely heard this well. If you have an antenna with a large gain, a low noise environment, and a receiver with excellent dynamic range you can receive this station as if it were a local station.
(2)ABC 8GO 990kHz, 0.5kW Nhulunbuy, NT, Australia at 16:00UTC on Jan.10
この局は、私は初受信でした。オーストラリア、ノーザン・テリトリーのヌランベイにあるABCのラジオ局です。同地区ダーウィン向けの放送を行っています。出力は0.5kWと小さく、珍しい局の部類に入るのではないかと思っています。IDは、”ABC radio Darwin"と出ています。0.5kWという低出力にも関わらず良好に受信できたことに驚いています。
This was the first time for me to receive this station. It is an ABC radio station in Northern Territory, Australia. I guess this station is rare to be received due to 0.5kW of low output power. The ID is "ABC radio Darwin". The ID is "ABC radio Darwin". I was surprised that I could get good reception in spite of 0.5kW of low output power.
(3) 5CS 1044kHz, 2kW Huddleston, SA, Australia at 17:58UTC on Jan.10
This was also my first time to receive this station. It is a commercial radio station in Huddleston in South Australia, Australia. The ID is "Classic Hits 5CS".
(4) 4BH 1116kHz, 17kW Brisbane, QLD, Australia at 18:00UTC on Jan.10
The ID is "Brisbane, 4BH" with music. This is a commercial radio station in Brisbane in Queensland state. The signal is not strong, but it is clearly audible because there is little external noise. Please try to feel how little external noise there is. I'm sure it's not like this at your home. The noise that comes right after the ID, is the noise of lightning over the Pacific Ocean.
(5) 3MP 1377kHz, 5kW Melbourne, VIC, Australia at 16:59UTC on Jan.10
ビクトリア州メルボルンの民放ラジオ局です。IDはチャイム音の後に"3MP, proud to be Ace Radio Network" と出ています。
This is a commercial radio station in Melbourne, New South Wales, and its ID is "3MP, proud to be Ace Radio Network" after the chime.
(6) Radio TAB 1539kHz, 10kW Adelaide, SA, Australia at 17:00UTC on Jan.10
This station in Adelaide, South Australia, is run by the Totalisator Agency Board and broadcasts horse and greyhound racing (so-called dog racing). On this day, This station was confirmed on 1242 kHz too . There is no ID in the audio clip, but at 18:00UTC, I could hear an ID "Radio TAB" in the weak signal. The announcer spoke something about Crystal Water in this clip, which seems to be the name of a horse. Please listen to the background female voice on the top, which is small but so clear too.
(7) 2QN 1521kHz, 10kW Deniliquin, NSW, Australia at 18:19UTC on Jan.10
オーストラリア、ニューサースウェールズ州、デニリクインの民放局です。IDは、"This is the Australia ... on 15-21 2QN"と出ています。少し信号は弱いのでヘッドフォンで聴いてみてください。
This is a commercial television station in Deniliquin, New South Wales, Australia. The ID is "This is the Australia ... on 15-21 2QN". The signal is a little bit weak, so try listening with your headphones.
(8) 2MM 1656kHz, 0.4kW Darwin, NT, Australia at 17:35UTC on Jan.10
This is a narrowcasting station in Darwin, Northern Territory, Australia. The transmitting power of this station is 0.4kW. The language spoken in this program seems to be Greek, not English. The ID is "2MM (Two double M)" with music.
(9) 3SH 1332kHz, 2kW Swan Hill, VIC, Australia at 18:00UTC on Jan.10
This is a commercial TV station in Swan Hill, New South Wales, Australia. The ID is "13-32 3SH". During this time, the lightning noise over the Pacific ocean was terrible. But the signal was still coming through.
(10) Hot Country 1629kHz, 0.4kW Darby, QLD, Australia at 16:59UTC on Jan.10
オーストラリア、クイーンズランド州のダルビーにあるナローキャストを実施している放送局です。出力は0.4KWです。IDは陽気な声で”Saturday morning talk show 9a.m..., Hot Country”と出ています。
This is a narrowcasting station in Dalby, Queensland, Australia. The ID is "Saturday morning talk show 9a.m., Hot Country" in a cheerful voice. The ID is "Saturday morning talk show 9a.m. ... ,Hot Country" in a cheerful voice.
The official frequency of this station is 1629 kHz, but there was clearly an offset, meaning the frequency was out of 1629kHz a little bit. I think the frequency offset was about minus 50 Hz.
Yesterday, in an online discussion with a senior MW DXer about antennas for MW DXing, I had to refer to a development report by Dallas Lankford, who was actively involved in the research, development, and experimentation of MW DX receiving antennas. After that, when I was searching another reports on the net,I learned fromthis newspaper article that he had passed away at the end of June this year. He was 78 years old. Mr. Dallas was a professor of mathematics at the university and also a technical consultant, and after retiring from his job at the age of 61 years old, he seemed to be working on the research of medium wave DX antennas more full time.
I was not acquainted with him, but I was overwhelmed by the amount of his passionate and meticulous development reports and I have read through many of them. I'm not sure I understand all of them yet, but I've found them to be very valuable. I have no doubt that these reports will be worth references when considering an antenna for MW DX in the future. You can refer to his numerous development reports at the following link,
"While the complexity of his mathematics research and radio pursuits required intense focus, time, and independence, those who knew him well admired his intellectual brilliance, tremendous energy, sense of humor, and his charismatic, sparkling personality."
He has neatly documented his research and development memos. I thought I should learn from him. In my case, I just make word files or excel files etc in the middle of calculations and they are piling up in my hard drive like garbage. Writing it down properly and leaving it behind is a process that takes a lot of energy, as you'll see when you try it. Isn't it very important to write down what you've done and leave it behind for posterity, both in your work and personal life?
I want to be able to imitate his energetic approach to his hobbies, even though he have retired from the field. People who are passionate about something seem to have an overflowing sense of youth and fulfillment even as they age. Am I the only one who thinks like this?
Challenges remained, however before a commercial array could be made available. Designing the amplifier chain was especially difficult because of competing constraints. These included the need for closely matched input impedance over a wide frequency range (to ensure accurate timing), very low noise (because of negative forward gain), good gain (to overcome signal cancellation), and acceptable linearity. Finally, though, after a period of extensive testing and improvement, the Shared Apex Loop™ array is ready for production.
-----How to set up a new opamp model to Ltspice XVII-----
1. Download the opamp macro model from its manufacturer.
2. Put .lib or .mod file of the opamp to C:\Users\Username\Documents\LTspiceXVII\lib\sub
3. Make.asy file of the opamp by using opamp2.asy and put it to
C:\Users\Username\Documents\LTspiceXVII\lib\sym
This is a comparison of open loop gain characteristic of LMH6702 between Ltspice XVII and Datasheet. The absolute values don't match but the relative value of the gain and phase and the position of poles are almost the same.