・Shortwave crystal radio (2014)
　A Proof-of-concept model of crystal radio with basket coils.





・RCX - Proto (2015) 
　Homebrew crystal radio for MW DXing. Prototype.
　I posted an article of making and testing of RCX-Proto in QEX JAPAN NO.17 (below).


別冊 CQ Ham radio QEX Japan NO.17  (2015.12)
  My article in this edition（ pp. 80-89, Japanese ）
  " Improve selectivity and sensitivity by devising coils.
  Designing and making of crystal radio with basket coils : Part 2 "

別冊 CQ ham radio QEX Japan No.15 (2015.6)
  My article in this edition（ pp. 90-95, Japanese ）
 " Designing and making of crystal radio with basket coils : Part 1 "



・RCX - 61000 (2016) 
　Homebrew crystal radio for MW DXing.
　After testing of RCX-Proto for a year, I tried to design a new set with higher performance and easy to use.
　Result: Very satisfied.

  


    A handout (PDF, Japanese)  at JARL Ham Fair 2016, Tokyo.
   Circuit diagram ( PDF, Japanese )
   Daily reception of JOGB (Kumamoto) in Tokyo from Jan. 1 to Dec. 31, 2017 with RCX-61000, (PDF, Japanese).



・RCX - 61000  MK II  (2017)  
　Homebrew crystal radio for MW DXing, 
　Exibited at the JARL Ham Fair 2017, I enjoyed a pleasant talk with many people. Thank you !
　

  
別冊 CQ ham radio QEX Japan No.25 (2017.12)
  My article in this edition（ pp. 82-89, Japanese ）
 " Designing and making of crystal radio RCX-61000 MKII for MW DXing "
    A handout (PDF, 4 pages, Japanese)  at JARL Ham Fair 2017 ( Ver.5 Revised on Sep. 30 ).
   Circuit diagram ( PDF/Ver.4, revised on Sep. 11 )

・RBM - 100 (2016)
　This is the second set of my portable crystal radio projects for the hotspots exploration ( see below ).
　It has 3 ferrite bars (18 cm long) with litz wire coils for the main antenna. A rod antenna is also mounted.
　Also, it carries red and blue LEDs as a detector in addition to germanium diodes.

 


・RBM - YR (2015)
　The first set of my portable crystal radio projects.
　I made it for my wife so as to use it during the hotspots exploration. It has 5 ferrite bars (18 cm long) with litz wire coils for the main antenna. Also, it carries red and blue LEDs as a detector in addition to germanium diodes.
　It appears in the footage of the " TAMORI Club ( See below ) ".

 



・Prototypes of RBM series (2014 - 2015)
　Each sets can use MOSFETs, LEDs, and diodes as a detector by replacing on the socket easily.

    

  

What is Radio Waves Hotspots ?
    There are places where you can hear the broadcast on a crystal radio without a big external antenna - like a long wire antenna, while those places are surprisingly several kilo meters  to well over 10km away from the transmitting antenna.
    We call those places radio waves hotspots.
    There are possibilities of hotspots, such as near tall building pillars, utility poles, guardrails, fences, crossovers, big bridges and so on.
    In order to qualify as a hot spot, it is subject to (1) while it depends on the power of transmitting antenna, it should be far enough from the transmitting antenna, and (2) you might be able to receive and enjoy the broadcast on a crystal radio without an big external antenna.
    On hotspots, you can enjoy the broadcast even with dynamic headphones or speakers, with loud sounds. With ceramic earphone, you could hear it at such a high volume that the ear might hurt.
    Also, even with an LED that has high forward voltage, detection can be done and you might see an led light up brightly.
     In addition to medium wave broadcasting, hot spots exist also in shortwave broadcasting band and FM broadcasting band.
    We frequently conduct field surveys on hot spots in Japan since 2014.

・Hotspots of Magnetic field type in Tokyo

・Hotspots of Electric field type in Tokyo
　 Tokyo Big Site - Feb 2017  (Report in Japanese)


<<<<<　Caution !!!   >>>>>　
· Do not explore in places where you can not secure your own safety.
· Do not enter private  property or restricted area without permission.
· Do not disturb other people while exploring on streets and other places.
· Be careful not to be mistaken as a suspicious person.
· Common sense and good manner are the most important things you should know while exploring.

Hotspots links

・全国・電波ホットスポット探検隊 - Radio Waves Hotspots Detectives (Japanese site)"
・全国・電波ホットスポットを探せ (Japanese site)

・Hotspots Detectives on National Television !
　We were featured in the famous Japanese TV show, " Tamori Club（タモリ倶楽部）" on February 12, 2016 (24: 20 - 24: 50).
　Title :  " A Thorough Survey of Radio Waves!  We are Radio Waves Hotspots Detectives"
　You might find the footage on Youtube by searching with " Tamori Club 2016.02.12 ".

　別冊 CQ Ham radio QEX Japan NO.23  (2017.06)
My article in this edition（pp.85-92, Japanese）
" Product review : UZ-8CQ - Large wooden loop antenna for medium wave reception "
In this article, you can check the great performance of UZ-8CQ in MW DXing with Tecsun PL-360ET, SDR#, or in the reception of NAVTEX Japan.

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