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

Fall Sprint October 2020

 Saturday, October 10th afforded me an opportunity to see Herbert AF4JF and Harry WA0CNS operate in the Fall Sprint.  They were able to make a two-way 1.2 GHz QSO with Zack W9SZ in Illinois from the YMCA.  They also tried on 2.3 GHz and 10 GHz with no propagation.  They spent the rest of the morning experimenting with 122 GHz.  Stability issues were resolved and successful Qs were made in the YMCA parking lot.  Feeling empowered and emboldened, we decided to relocate at 370 Lake Park (EM48rt) near St. Peters, MO.  

S-9 signals were achieved shooting across the lake about six-tenths of a mile.  We are making plans to attempt a 7K path in a few weeks!

                            Herbert AF4JF at the YMCA parking lot with some of his uW antennas.

                                                       

                    Harry WA0CNS with his portable uW gear at the YMCA parking lot

                      

                 AF4JF is setting up his 122 GHz rig to work Harry WA0CNS at the YMCA parking lot.

    The view at 370 Lake Park, EM48rt from WA0CNS across to the other side to AF4JF about .6 miles.

                  Harry WA0CNS with his 122 GHz rig at 370 Park EM48rt 

Herbert wrote about his  sprint experience: 

I have participated on the contest too. However, my participation was aimed at testing new technologies. 

I have made a CW QSO with Zack W9SZ on 1296MHz across 259km, but not on 2.3GHz although the stations were comparable in RF power and antenna gain on my side. Maybe next time. We have also tried 10GHz, since we have worked each other from this location, but no luck this time.

The next thing I was testing was my new 122GHz unit from VK. We have made a contact wit Harry WA0CNS using these units before, but it was on windy day and my station was open with no shielding of the PCB. As a result, the frequency stability, although GPS disciplined, was not good enough. This has definitely changed, two pieces of styrofoam fastened to the PCB on both sides to cover the oscillator did the trick! Even with 1pps frequency reference (I haven't modified this board for 10MHz yet), the frequency was stable enough for convenient CW QSO! We have worked each other across a lake with Harry WA0CNS with S9+ strength and nice clean signals ... wow!

One of attached pictures shows my "small" 122GHz unit with conical horn in front of the 10GHz tripod. I am also including a picture of Harry's station that uses a dish and rifle scope for aiming.

We are planning one more test over longer distance this year.

73 Herbert

AF4JF