SEA GAIN EFFECT FOR MW DXING

    Do you know sea gain for MW reception ? The sea gain is the additional signal gain when one or both terminals is situated near the sea, but it does not apply to propagation over fresh water.
Therefore, You can enjoy MW DXing much better at a sea cliff or a sea coast than that in inland area.
   The sea gain was found long time ago by P.Knight, a researcher of BBC around 1975 and the sea gain was defined with some formulas in the ITU-R recommendation P.1147-4 (Click)
" Prediction of sky-wave field strength at frequencies between about 150 and 1700 kHz". The sea gain depends on the distance between transmitting point and receiving point  and frequencies. The graph below is  an extract from the ITU-R recommendation.  The curve A is for MW band. For MW DXing, the propagation distance would be more than 6000 km then the sea gain is expected about 10 dB. This means your S-meter goes up about 3 scales(I mean when  your S-meter indicates S-1 at a inland area, you can expect S-4 signal at a cliff or a coast.)   You should not ignore this effect for much better MW DXing.

   Some papers written by P.Knight et al of BBC are downloadable. The clickable links are as follows.

The influence of the ground and the sea 

on medium-frequency sky-wavepropagation.(1968)

LF and MF propagation: An approximate formula for estimating sea gain (1975)

LF and MF propagation: The effect of earth curvature on sea gain (1976)

    There are very few articles of MW DXing that report about the sea gain. But we can read a very interesting article titled " Inland versus seaside MW DXing".(Click)

written by John Plimmer from South Africa who is one of famous MW DX information web site DXing info Community.   ((http://www.dxing.info/)

     The following video shows some reception scenes of KKOL (Seattle) on 1300 kHz at a cliff in Chiba, Japan on Sep.22 2016.  The audio clips and pictures are provided for my blog by one of MW Japanese DXers, Sawapon (Sawapon is his nickname.) Sawapon's blog(Japanese) is here (click).. We conducted a DXpedition with other MW DXers on the same day. The signal of KKOL propagating 7700km from Seattle was received well even with a portable MW radio thanks to the sea gain. 

THE MOVIE " IN THIS CORNER OF THE WORLD"

   This movie "In this Corner of the World " that was supported by crowd funding of this cartoon fan including me, has been just released on Nov. 12, 2016.   Most of movie theater seemed to be full yesterday.  As one of supporting fan, my name is listed at the end credit of this movie. This anime depicts ordinary people's life in Hiroshima during the Second World War through the life of heroine "Suzu".  This movie was made with accurate historical investigation by the movie staffs including the director Sunao Katabuchi. This investigation gives the anime strong powers of persuasion. 

   This movie doesn't insist on vigorous opposition to the war in us directly and dramatically. This movie just shows us the life of people in laughs, sadness and loves simply with good tempo in about 120 minutes. I was never bored at all. The color of each scene and each expression of characters in this movie was so excellent and impressive. 

    During the movie, to be honest, I sobbed. I could mull the life of people during the war in the past comparing to my life over in my mind. It is difficult to explain my feelings with words, but I was watching this movie remembering  the spent days with my grand mother and grand father in the countryside.  Other audience were also sobbed too, but we felt hopes, happiness and warmness at the last scene of this movie.

    After the movie  I felt that I was standing in this "little" corner of the world that had been made by ordinary people who live in the past.

    I hope this movie will be introduced to all over the world in appropriate languages. I recommend all of my foreign friends to watch this movie to understand Japanese ordinary people's life in the past and Japanese heart that has been passed down calmly from our ancestors to us who are living in the present world.

  

Ａ support member meeting in Tokyo with the production staff of this movie on Aug.4 in 2015

(The man at the center of front row is Director Sunao Katabuchi.) 

This movie is also introduced on NHK World's VOD .

APPLICATION OF GOOGLE MAP FOR MW DX LOG

    I am evaluating Google map for my MW DX logging. The map below shows a distribution of received MW stations of U.S. on TDXC DXpedtion conducted at a coastline of Chiba prefecture in Japan on Sep.22,2016.  With your mouse, you can freely click each orange dot to see the reception sound link for each received station and You can also see the distribution of the stations. You can move the map freely too. Most of the received stations are located close to west coast.      I am wondering why I couldn't receive more inland MW stations. I guess this result is related to sea gain effect at transmitting site. 

A PICKED MW DX STATION FROM MY DX-PEDTION LOG ON SEP.10 IN 2016

    Let me introduce a picked MW DX station from my TP (Trans Pacific )DX-pedition log on Sep.10 in 2016. I could receive KFAB in Omaha of Nebraska in the U.S. on 1110 kHz at 18:00 JST. The reception point was a sea side of Iwate prefecture. We used a 20m TDDF antenna.
The propagation path length is about 9400 km.

    This station has been received sometimes by other Japanese DXers too.  I 'm very glad to get this station ID because this MW station is the most inland American MW station for me in this year.
In this video, you can hear "This is news radio ..10 KFAB Omaha.". You can see its transmitting antenna here and its office here. 

 This is a compilation of KFAB's Jingles. 

MW STATION MAP OF U.S & CANADA & MEXICO

   I am evaluating Google Map for my MW DXing. This is a MW station map of U.S. and Canada and Mexico. The stations with tx power more than 0.99kW  for night transmission are shown in this map. I would like to add a search window to point the station by its call sign. But I haven't found the solution yet.   

MW DX LOG IN KAWASAKI ON OCT.24 2016

　　The condition was not so good.  I could hear some regular big gun stations in Kawasaki from 2:00 a.m. to 3:00 a.m of JST.

 Bangladesh Betar on 693 kHz 1000kW
 BBC World Service on 1413 kHz (Oman) 800kW
 ABC 4QD on 1548kHz (Emerald QLD, Australia） 50kW

* These links are clickable to see the location of transmitting antenna on Google map.

    ABC 4QD on 1548kHz was not so strong even though the signal becomes usually strong from Oct.  I enjoyed a ethnic song like Quaran on Bangradesh Betar with deep fading for short time. I would very appreciate if anybody translate the song in English because I couldn't understand the lyrics of song.

DISTRIBUTION MAP OF MW STATIONS HEARD IN THE MW DX PEDITION IN CHIBA ON SEP.22 2016

    Fig1.shows a night area at 19:00 JST on Sep.22 2016 when we caught a lot of MW stations from north America. The propagation was achieved by skywaves in the night area

Figure 1 The night area at 19:00 JST on Sep.22 2016.

    Fig.2 shows the distribution of MW stations of north America that I digged in the DX pedition. Most of the stations are located in the west coast. There are some inland MW stations too. I'm satisfied with this result of this DX pedition but I would like to dig more inland MW stations in the next challenge.  

Figure 2 The distribution map of MW stations heard in the MW DXpedition in Chiba

(Note: Some stations are not shown in this figure due to reduction by Google Earth.)

MW DX LOG IN KAWASAKI ON OCT.17 2016

   The condition seemed not to be good, but I could hear some big gun stations TWR-Moldova, BBC-World service-Oman, and ABC 4QD-Australia. Unexpectedly I could hear AFN Korea on 1440kHz (it was presumed AFN Korea Thunder 5kW ) too. I used a 1m*1m handmade shielded loop antenna in my balcony and a 16dB preamplifier and CMC filter. The RX was a Perseus SDR.

BBC-World service-Oman on 1413kHz at 01:59 JST


ABC 4QD Australia on 1548kHz at 02:00 JST (Very weak)

You can hear the music that is played right before every hour news.

TWR-Moldova on 1548kHz at 02:58 JST You can hear the IS.

AFN Korea (Thunderbird?) on 1440kHz at 03:59 JST.

STRANGE SYMPTOM OF MY PERSEUS RECIEVER WHILE RECORDING

   This video shows the strange symptom of my Perseus receiver.  This occurs suddenly only while recording and it cannot be stopped until I restart the program. My PC is Lenovo X201 with 256GB SSD ,4G RAM  and core i5 CPU.  I encounter this phenomenon when I use an external HDD through USB3.0 interface too.
   I hate this problem because my midnight MW DX recording becomes ruined. I would appreciate if you could tell me any solution for this problem.

Postscript information (Oct.24, 2016)
According to Perseus SDR HW &SW Group of Yahoo,  This problem seems to be occurred by increment of CPU load or a USB3.0 driver problem. I am still checking this symptom. 

MW STATION LOG OF DX-PEDITION IN CHIBA WITH TDXC MEMBERS ON SEP.22

   This is a log of MW DX-pedition in chiba on Sep.22 2016.  Most of the MW stations were from west coast of North America but several inland stations from Utah, Oklahoma, Idaho, Colorado (Red call signs )could be heard too. You can listen to each audio file by clicking each station call sign and see the location by clicking each QTH.  I recommend you to use a headphone :-)

MW DX-PEDITION AT A CAPE FACING THE PACIFIC OCEAN IN CHIBA

    Totsuka DXer's Circle(TDXC) member including me enjoyed a MW DX-pedtion at a cape facing  pacific ocean in Chiba prefecture on Sep.22, 2016. Unfortunately it was almost rainy day. We set up a twisted double delta flag(TDDF) antenna and pitched two tents there. 

     TDDF antenna was terminated by voltage controlled resistor (RTR:Remote Termination Resistor) and the antenna was fed by coaxial cable with a supercharged voltage follower.

We used SDRs such as Perseus and ELAD and the antenna output was divided to each member of TDXC.   

     Even though thunder noise often prevented us from catching trans pacific DX stations in good condition I could catch more than 50 MW stations from North America,Hawaii,Guam and Mexico in total. Thanks to sea gain, we could hear some MW station of North America with a portable MW radio too. The list of MW stations that I caught and their sound files are introduced in next article.

KKOL(Seatlle, WA) on 1300kHz at 19:00 JST

PRELIMINARY SIMULATION OF TWO KINDS OF FLAG ANTENNAS FOR MW BAND

1. Antenna size

     I tried to simulate two kinds of flag antennas for MW band. One is a normal flag antenna and the other is Twisted Double Delta Flag (TDDF) antenna.  I used two simulation software called MMANA-GAL and MMANA (Japanese version) .
     I'm not sure the best size for these two antennas. So I adopt that the length is 20 m and the height is 5 m for both antennas considering practical field installation. Fig 1. depicts the size of each antenna. The termination load value is chosen for best FB ratio on 1.2 MHz.  Relative permititivity and conductivity for ground are 13 and 1 [mS/m].

Figure 1. The size of antennas

2. Directional characteristics in horizontal plane 

    Fig.2 shows directional characteristics in horizontal plane for both antennas. In this figure, FB ratio of the normal flag antenna is better than that of the TDDF antenna. However the half value angle of the TDDF antenna is 104 degrees and the angel of the flag antenna is 158 degrees. This means the TDDF antenna has more sharp directivity than the normal flag antenna.

Figure 2. Directional characteristics in holizontal plane

3. Directional characteristics in vertical plane

    Fig.3 shows directional characteristics in vertical plane for both antennas. In this figure, elevation angle of the TDDF antenna is smaller than that of the normal flag antenna. It seems that the TDDF antenna is suitable for very long path propagation of MW band. In terms of the shape of directivity for back side, the TDDF antenna has more pressed shape compared to the normal flag antenna. This means that the TDDF antenna is more robust for interference by domestic MW radio stations and other noises coming from behind the antenna.

Figure 3. Directional characteristics in vertical plane

    Fig.4 shows antenna patterns for both antennas in 3D view. The antenna gain Ga of TDDF is 16 dB lower than that of the normal flag antenna.  To compensate for the reduction of Ga, a preamplifier  with low NF and high IP such as RPA-1 of DX Engineering could be applied.

Figure 4. Antenna patterns in 3D view

Figure 5. Low NF and high IP preamplifier

4.Antenna Impedance

 Fig.6 shows simulated frequency characteristics of both antenna impedance and F/B and absolute antenna gain Ga for the isotropic antenna. The antenna impedance varies by a value of termination load and frequency etc. If 50 ohm coaxial cable is used as a feeder, an appropriate impedance matching circuit must be needed.  Appropriate impedance matching methods will be discussed later in this blog.  

    It should be noted that both F/B and Ga of the TDDF antenna is almost proportional to frequency but F/B of the normal flag antenna is inverse proportional to frequency even though Ga is proportional to frequency.

Figure 6. Frequency characteristics for antenna impedance and F/B  and Ga 

   

ELECTRICAL CHARACTERISTICS OF GROUND

    In this blog, I will try to simulate receiving antennas for MW DX. In these days, Flag antenna and its modification are very popular among enthusiastic MW DXers because these antenna are directional antennas that  can mitigate interference from strong domestic MW radio stations on adjacent frequencies. A directional characteristic of typical flag antennas is cardioid.  

    To conduct the simulation of MW receiving antenna we should know some parameters for electric characteristics of ground. These are conductivity that is reciprocal of electrical resistivity and relative permititivity.  

    Figure.1 shows the distribution of electrical resistivity of Japan archipelago. The conductivity is the reciprocal of the electrical resistivity. For example the conductivity of orange area in this figure is from 3[mS/m] to 1[mS/m]. 

Fig.1 Electrical resistivity of Japan archipelago

*This figure is linked to  http://www.sankosha.co.jp/technical_data/technical_earthing/daititeikou.jpg

    The relative permititivity can be obtained from ITU-R recommendation P.527-3.  The relative permititivity for medium dry ground is about 15.

Fig.2  Relative permititivity and conductivity as a function of frequency
(*ITU-R P.527-3)

     From these results, I decided to use these parameters for the simulation as follows.

       

       Conductivity : 1to 3[mS/m]

       Relative permititivity : 15
      

OVERSEAS MW STATIONS HEARD IN JAPAN -2

    I introduce very popular overseas MW stations easily caught in Japan. These audio files were made from reception records in Fukushima city (inland area) with a 1m*1m homemade shielded loop antenna and DX Engineering RPA-1(16dB preamplifier )and AOR AR7030PLUS at night on September in 2015.

Audio file 1: BBC World Service (Oman) on 1413kHz     Google map
Audio file 2: KUAM (Guam Island ) on 630kHz    Google map
Audio file 3: KTWG (Guam island) on 801kHz     Google map
Audio file 4: Trans World Radio (Moldova) on 1548kHz    Google map

Shielded loop antenna

OVERSEAS MW STATIONS HEARD IN JAPAN -1

    Let me introduce an example of reception of overseas MW station in Japan.
This is a reception record of Australia 4QN on 630kHz at 10:00 UTC on May 2 in 2016.
    The radio station 4QN is transmitted from Brandon Queensland in Australia that is about 6000 km apart from the reception point. 4QN is one of very popular overseas MW stations caught in Japan.

Google map: Australia 4QN, Brandon QLD

    We set up a twisted double delta flag antenna beaming to south east at a cliff facing to the Pacific Ocean in Chiba prefecture.  The received signal was so strong and the program could be heard very well like Japanese local radio. Sea gain effect also helped to catch such a nice signal too. The another weak English program also can be heard on the same frequency.  This is KUAM from Guam island.

CIRCUMSTANCE OF MW DX IN JAPAN AS OF TODAY

     For foreign MW DXers, I introduce the circumstance of MW DX in Japan as of today.
About 40 years ago listening to international radio broadcasts on short wave crazed for teens.This hobby was called BCL (BroadCast Listening) too. Monthly magazine called "Tanpa" (Short wave)　was being published at that time.  In this magazine, MW DX was also introduced and this MW DX was getting different popularity compared to listening to international short wave radios because of its difficulties of reception within so many interference of domestic stations and fun of modification of receivers such as changing IF filters etc.  I remember narrowing IF filter for YAESU FRG-7(FROG) and TRIO 9R-59D. Reception antennas for MW DX at that time were mainly loop antennas and long wire antennas including Beverage type.
    Unfortunately this boom started shrinking rapidly after 1980 and the rise of Internet almost beat this hobby after 1990. But some fanatic Japanese MW DXers still had been enjoying MW DXpedition at ocean side with using AOR AR7030 etc..

Reference: Meeting Japanese DXers by Jim Solatie

    As of today, I guess the population of MW DX in Japan would be less than one hundred. On the Internet, Japanese web sites that write mainly about MW DX are very few in total contrast  to the popularity of MW DX in western countries.
   However  some enthusiastic Japanese MW DXers still keep their activities as of today. Their hunting styles have changed to recording all MW band at night with using software defined radios such as Perseus and analyzing the record very carefully taking very long time. The popular reception antenna for MW DX is now changed to flag type antenna.
   In these days problems of noise interference on MW band in urban area is very severe for MW DX in Japan too. But Japanese MW DXers mitigate the noise by employing some handmade common mode choke filters (CMC) and a galvanic isolation filter effectively.

A scene of DXpedition in Japan as of today

Setting up a twisted double
delta flag antenna

ABOUT MY HOBBIES AND STUDIES

    My name is Fumiaki MINEMATSU. I'm Japanese, 51 years old.

I decided to write about my hobbies and studies on this blog.

My hobbies are MW DXing and singing songs with electric piano etc. 

First of all, I'm going to write mainly about technical articles regarding to MW DXing for a while.
    I have been studying RF technical problems and learning English conversation as an international communication skill too. I will write about the study when I find new things to me.

My RX (Perseus SDR,AR7030Plus and CRF-1)