Sunday, January 20, 2008

Received EME Signals on 7 MHz.

The High Frequency Auroral Research Program (HAARP) ran some tests on the 40-M band this weekend. They transmitted a 2 second carrier from their station in Gakona, Alaska, then were silent for three seconds. Hams and SWL's were asked to see if they could hear the resultant echoes from the moon. It takes 2.7 seconds for a signal to reach the moon and return to the Earth. So, a little over 1/2 second after the HAARP transmitter went silent (if you could hear it directly), the echo from the moon would appear.

I did not try to hear the test on Friday night since I felt I had no chance with only an 80-M Inverted-V and the Famous 160-M Inverted-L for antennas. But based on the fact that many hams did hear the signal (see this YouTube video), I decided to give it a try on Saturday night. Last night Garie, K8KFJ, heard it on his Icom 706-MkIIG with a vertical and Don, W8DL, heard it using an Icom IC-746 and a 270-ft. longwire.

The first hour of the test was on 6.7925 MHz and I heard NOTHING. I was drowsy and about gave it up but decided to at least spend a few minutes on the second hour of the test on 7.4075 MHz just to see if it was any different. I peaked up the Yaesu FT-1000MP MkV for the weakest signal I could detect. The AGC was OFF, no attenuation, RF Gain at maximum, the VRF was ON and peaked and the 125 Hz crystal filter was switched in to give the maximum signal to noise ratio.

About 9 minutes into the test I began to hear a signal. So, I began recording the audio out of the radio on my computer. I noticed I was only hearing one signal. Was it the HAARP transmitter directly via the ionosphere or was it the signal reflected from the moon? I didn't know. However, I had very carefully adjusted my station clock to WWV just before the test. My digital seconds would click over to the next second exactly as WWV "clicked." Also, I began the audio recording as close to 0839 and 00 seconds GMT as possible.

After about 13 minutes of recording the signal was getting fairly strong. I carefully watched the digital clock and the signal began at 2-1/2 seconds, 7-1/2 seconds, 12-1/2 seconds, 17-1/2 seconds and so on. I was receiving the signal from the MOON!

Of course, this conclusion was based on the assumption that the HAARP signal was begun exactly on the minute and every 5 seconds thereafter. Later on in the test, after a period when I could hear no signal, I began to hear a signal again and this time I noticed that it began exactly at 00, 05, 10, 15 seconds. So, I was now hearing the HAARP transmitter. (There was a short period where I "think" I could hear both signals but the EME signal was so weak I could not be sure. I'll check the audio file later to see if both signals can be pulled out.)

Here is a spectrogram that was recorded in real-time as I was receiving the signal. The width of the graph is just about 15 seconds and you can see three of the 2-second long transmissions.


When I played back that portion of the audio I had recorded on the computer, I found that section 13 minutes and 17 seconds into the file. If you look closely at the timeline from the audio program below, you can see that each signal starts at 17-1/2 seconds, 22-1/2 seconds and 27-1/2 seconds. This shows it is the signal reflected from the moon!


You can listen to the 14-second MP3 file of this signal HERE. The file size is 227 K. The audio tone is at about 580 Hz.

This signal is a good deal stronger than a lot of EME signals I had QSO's with on 432 MHz. from Ravenswood. It was definitely good enough to make a contact, IF the HAARP station could have heard my 1,500 watts (unlikely since they were transmitting in the range of 3.2 MEGA WATTS!)

All in all, I had hoped to do a little better. But, conditions tonight may not have been as good as last night. The A-Index was 9 and the K-Index was 3. But, it was still a hoot to have heard an EME signal on 40-M. Not something you run across just any day.

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