122GHz challenge

When Harry WA0CNS and Herbert AF4JF made their first 122GHz QSO on September 20, 2020 during second leg of the ARRL microwave contest, everybody was surprised how easy it was. Our second 122GHz QSO during the SPRINT Contest on October 12 made it look even easier. We were planning on extending the distance spanned by our QSOs over 10 miles. First step was supposed to be a QSO from EM48rq (Chesterfield, MO) to EM48rr (Harvester, MO) across the Missouri river over a distance of 3.65 km with direct line of sight. We have found suitable locations, checked them ahead of time ... everything seemed to be "granted":

This picture shows Herbert's location and open view towards Harry (on a hill on the horizon):

However, neither of us heard a beep, just a noise. We have tried to turn our antennas, tune the radios up- and down, move around the parking lot ... nothing. Herbert even went across the river to Harry's location to make sure that Harry really points his antenna in correct direction. Everything was OK, just no signal. 

Weather situation (recorded on Herbert's side of the river) was:

• temperature 4.1 deg. C
• dew point 1.3 deg. C
• pressure 1011.9 mBar
• humidity 43.2 %

The day was actually very windy, we were both "frozen to the bone", so we gave up for the day and decided to continue on the next day, make sure our stations still work and decide how to continue.

Next day was a little warmer. It was also the day of a SLAMS meeting. The SLAMS just started having meetings in the local park instead of eating breakfast together at Denny's. Harry WA0CNS and Herbert AF4JF got together in the Creve Coeur park. (EM48sr). Armand KD0PXF joined us for a short talk later. Harry started a small fire to keep our fingers movable:

Weather situation was:

• temperature 16.3 deg. C
• dew point 3.9 deg. C
• pressure 1000.5 mBar
• humidity 40.2 %

We have set up our stations approximately 100 ft. apart first, then about 1000 ft. In both cases, we have heard each other immediately. Signals were very strong and stable, exactly on the frequency (IF on 144.4 MHz CW) where expected:

WA0CNS

AF4JF

View from AF4JF towards WA0CNS

Well, our stations appear to be in good shape. Signals were very strong and aiming was not too critical (at least not for Herbert who uses a conical horn). We are not sure why our contact across the distance of 3.65 km didn't work. Looks like QSOs on the 122GHz band will be a challenge and come with surprises...

Herbert and Harry already decided on next try, two weeks ahead from now. We hope to have more good news to report after that next test.

73 Herbert

AF4JF