WF9XIH

by
Brian Justin, WA1ZMS/4
 
The early history of wireless contains the names of many great pioneers. While 
Marconi’s name is most well known, the names of Fessenden and Heising are only 
rarely mentioned.  As early as 1900 Reginald Fessenden  was experimenting with 
the direct transmission of human speech. While during WW1, Raymond Heising was 
developing a method of constant-current modulation that was one of the earliest 
forms of AM. Since I have been one of the active CW 600m stations as part  of 
the ARRL’s Experimental License project for some time now, I decided to take a 
step or two further into the realm of early radio transmissions.  One of the 
transmitters I have used for 600m CW and QRSS work has been a vintage homebrew 
design that could  support traditional CW and Heising AM. Since the ARRL’s Part 
5 license only supports CW and narrow-band digital modes, the Heising modulator 
went unused until a new idea came to mind.
 
Fessenden’s early work includes a very unique 1906 Christmas Eve transmission of 
him playing the violin, a recording of a “Ombra mai fu”, and him reading a Bible 
verse.  An idea was thus born to apply for  an FCC STA (Special Temporary 
Authorization) for 600m operation that is for amplitude modulation, in 
particular the Heising modulation.  With the cooperation of commercial coastal 
CW station WNE and the FCC’s OET (Office of Engineering Technology) the STA  
with call sign WF9XIH was granted for AM transmissions until March 1st, 2012 
with a center carrier frequency of 472.5kHz.  The plan is to begin a series of 
evening test transmissions the week of December 18th, 2011 with a special 
recreation  of Fessenden’s Christmas Eve transmission at 0200z on Dec 25th. 
(That would be 9pm EST Dec 24th, 2011).
 
Since the likelihood of a 5w AM signal being heard much beyond a few 10’s of 
miles, a 500W solid state linear PA will be used for best DX.  WF9XIH is 
licensed for up to 20wERP (just like the WD2XSH stations) and  every effort will 
be made to run as close to that ERP as possible. The same antenna (a 160m dipole 
feed as a Marconi-T against ground) that has been used for WD2XSH/31 will be 
used for WF9XIH.
 
Commercial station WNE is currently running CW marine weather transmissions at 
2200z & 0100z daily. So you can sharpen your 25WPM CW skills at those times 
too.  WF9XIH transmissions are being coordinated with WNE  and any changes to 
the WNE schedule will alter the WF9XIH operating times.  The current plan is to 
at least make a Heising AM transmission most evenings at 0200z. Audio loops of 
speech and a series of stepped audio tones will be used most of the time. The  
stepped audio tones will make it easier for DX listeners to demodulate in CW or 
SSB mode even when they are well beyond the range of the AM signal.