Canadian Reginald Aubrey Fessenden in his lab believed circa 1906 (Source: Radio Canada International)
Many thanks to SWLing Post contributor Brian (WA1ZMS), who writes:
What has now become an annual LF listening event, WI2XLQ (an FCC Experimental Callsign) will once again be QRV for a recreation of the alleged first voice transmission made by Reginald Fessenden in 1909. Transmission on 486kHz in full carrier AM will start at 22:00z on Dec 24th and run for 24hrs. In keeping with tradition, a repeat transmission will take place on Dec 31st at 22:00z and run for 24hrs. Further details about the Fessenden transmissions can be found in prior years of ARRL News.
-Brian, WA1ZMS
I look forward to tuning in each year. Thank you so much, Brian, for making this annual broadcast a reality!
TX is a Heising modulated MOPA design from 1921. Osc is a UV201 and final is a VT-25 (mil version of UV-202 as the 203s were getting costly to keep going through). The output is 3w of AM. That gets attenuated and drives a pair of Hafler 9505 audio amps running in phase to get about 300w of AM carrier. The antenna is my 160m dipole with 600 ohm open wire feed that gets tied together and through a variometer is feed against a maze of ground rods and wire all buried in the side yard.
Hope that helps
Yeah! It’s Fessenden time again. I picked this up for the first time last year on both transmissions. I think the Baltimore area is on the very northern fringe for reception, but with radio propagation, you never know. 486 kHz is a challenge for a lot of equipment, particularly antennae. My loop just barely tunes it. Lots of fun.
Brian, if you read this, can you give us some details on your LF station? Transmitter, power, antenna, etc would be interesting to know about.
Thanks/73
Last year’s SWL post mentioned some of the retails, but not all: WI2XQL uses a slightly more modern home-brew 1920’s era Amateur-grade MOPA transmitter (based on a UV201 oscillator and UV202 final) and a high power linear FET amplifier. The MOPA also uses true AM Heising modulation as was first done in WW1 for the US military.
https://www.arrl.org/news/view/experimental-station-will-recreate-1906-fessenden-transmissions
500W amplifier