47 GHz AND THE FIRST WEEKEND OF THE 2005 10 GHz AND ABOVE CUMULATIVES CONTEST

by Dave Hallidy K2DH

As most of you know, there is a group of folks within the Rochester VHF Group that is very interested in operation on the millimeter-wave bands (the bands at and above 10 GHz). This group consists primarily of: WB2BYP, K2LDU, WO2P, W2DYY, N2EZS, K2EHF, K2DH, and is growing every year. For a number of years now, we have gone out to see what we could do to make QSO’s and score points in this contest. We always have a great time, but we never turn in the highest scores, just because we don’t live in an area where many really long-haul QSO’s can take place (for example California, where mountaintop-to-mountaintop contacts approaching 1000km are possible). But, we understand that, and still go out to see what we can do and have fun.

This year was the same, with one exception- a number of us have been working towards VUCC on 47 GHz and have been stuck at the four-grid level for some time (you need five grids confirmed on 47 GHz for the basic award). So, one of our goals this year was to try to get that elusive 5th grid square. In our area of Western NY, four grids come together at the so-called “Four Corners”- FN03, FN13, FN02, and FN12. At one particular spot, FN02xu “Transit Road”, there is a very good path to these four grids. However, the fifth one requires “busting out” of the local area and working at least one fairly long-haul path to the fifth grid. From our Transit Road site, that fifth grid turns out to be either FN04xa or FN14aa (both in Canada, 130km from the FN02 site, and with the water of Lake Ontario beneath most of the path). A year ago, when we started this venture, John WB2BYP generated a spreadsheet that allowed us to calculate the expected signal to noise ratio over various paths, taking into account such variables as: Power Output, Antenna Gain, Receiver Noise Figure, and especially attenuation due to Water Vapor and Oxygen. On 47 GHz, we quickly realized that the signal strengths we typically would see on 10 and even 24 GHz were not going to be repeated on 47 GHz. The 10 GHz band is affected to some relatively small degree by water vapor in the air, and the 24 GHz band is greatly affected by the same thing- water vapor in the air. On 10 GHz, the path to FN04 has about 1.8dB additional loss due to Oxygen and Water Vapor. At 24 GHz, the same path has over 21dB additional loss, mostly due to Water Vapor losses. But at 47 GHz, the same path has OVER 48dB additional loss, 39 of it due to Oxygen in the atmosphere! See Figure 1 for a comparative graph of the expected signal to noise ratios for our modest stations on each of the three bands- you can quickly see that even if we were to bump our transmitter power from the 30mW we each currently run to a “gigantic” 1W, we wouldn’t gain that much in DX capability, due to the additional loss in the path from Water and Oxygen!

Figure 1

It should be noted here that K2LDU and WB2BYP were successful on one attempt to make the path over the lake work, between FN04xa and FN02vu (Werner Road). On that same day, others who tried to duplicate the results, from FN02xu (Transit Rd) were unsuccessful.

The weather forecast for the first weekend of the contest actually boded well for those of us who were going to try again- while Saturday was predicted to be warm and humid, there was a front coming through on Saturday night that would bring rain overnight and drying conditions throughout the day on Sunday, with cooler air and low humidity.

So, Saturday was spent working the usual suspects on 10 GHz- W2DYY, N2EZS and I were parked on top of Transit Road and managed to have quite a good time with some local and some DX contacts on 10 GHz. We also worked each other, K2LDU, and WB2BYP on 24 and 47 GHz over local paths. Over the course of the day we worked into EN92 on Lake Erie (thanks NE8I/3, K3SIW/3, and WA8VPD/3!), W2EV/VE3 on top of the Skylon Tower (nice signal Ev!) and a number of others including, at the end of the day, AF1T/1 located on Block Island, Rhode Island (FN41ee) at 561km, all on 10 GHz. After hearing the weather forecast, WB2BYP decided definitely to head for Canada on Sunday, so Russ and I decided to return to Transit Road rather than head to another site for a better shot to the stations in New England. See Figure 2, 3, and 4 for pictures of the setups of N2EZS, W2DYY, and K2DH on Transit Road.

Figure 2- N2EZS’s Station

Figure 3- W2DYY’s Station

Figure 4- K2DH’s Station

Sunday morning I got to the site about 1230Z and it was enveloped in fog. I thought we were doomed, as it didn’t seem to be moving, and it seemed as though it might rain at any instant. However, I also knew that WB2BYP wouldn’t be on site in FN04xa until at least noon, so I watched and waited. As time went on, things began clearing up and W2DYY arrived at the site. We managed nice QSO’s with VE3ZV and VE3TFU on 10 GHz in EN93, then a while later with VE3FN/2 in FN25- his signal was crushingly loud at 1649Z. Just then, WB2BYP/VE3 came on the air from FN04xa, stating that he was setting up and would be ready shortly. It was very windy, but the air was clearing fast- we could see sights which were lost in the haze 24 hours earlier. A quick check of the Relative Humidity showed it to be dropping, now at about 55%, down from the 60’s a short while before. At about 1715Z, John began sending dashes on 24192.100 MHz, and his 24 GHz signal was crushing- the air was very dry over the lake. Once we had all peaked up on 24 GHz, we went to 47. At about 1730Z, John started sending dashes on 47088.100 MHz. Russ was the first to find him- I discovered I have a 3o negative offset in my 47 GHz dish relative to 10 and 24- once I found that, I found John, too. We both jumped and danced around as we listened to his signal- not very far out of the noise, but Q5 with rapid QSB. Russ then sent back to John so he could peak his dish on us, and the next time John transmitted, he was much stronger, peaking S5 at times. Russ quickly worked John for Russ’ fourth Grid on 47 GHz, then it was my turn- I also easily worked John, and this was Grid number five for me, completing VUCC on 47 GHz! Figure 5 is a shot taken by WB2BYP/VE3 of the shot towards Transit Road from FN04xa- apparently, the shot to us is just to the left of the hay mound!

Figure 5- From FN04xa towards FN02xu (I think you can just see Russ and me smiling, waaaay in the background!)

At that point, K2LDU, who had been operating from FN02vu (Werner Road) had heard nothing from John. He also could not hear us when we pointed toward him only 8 miles away, so we were pretty sure there was a problem with Charlie’s gear. Hoping that wasn’t the case, Charlie packed up and headed for Transit Road. Meanwhile, Walter NQ2O showed up with his barefoot 10 GHz transverter (10mW and 8” dish) and proceeded to work John on SSB from the FN04xa site. We then talked John into going to FN14aa, only a few miles away, to try again on 47. John arrived in FN14aa, got set up, and proceeded to have to wait out a rain shower that ultimately took out the PA in his 2m liaison rig. No matter, he was louder on 10 GHz anyway, so we used that for much of our liaison talkback. Once again, John began sending on 47 GHz and both Russ and I quickly found his signal- louder than the previous time, and once peaked up, pushing as much as 20-30dB out of the noise, but again with rapid QSB, probably from the rapid change in the water vapor conditions over the lake. We both worked him, Russ for Grid #5, me for Grid #6. Unfortunately, K2LDU could not hear John at all, and John could not copy him. Once again, NQ2O worked John on SSB on 10 GHz, using his 10mW rig!

At that point, Russ and I were very pleased and immediately agreed that we would be the next ones to go across the lake to provide QSO’s to those still needing them here. A huge “THANK YOU” has to go to John and his wife Gloria, for taking the day to give us the 47 GHz QSO’s. Thanks also to everyone else who worked us or tried to work us on 10 and 24 GHz- your efforts are very much appreciated. And a postscript- apparently K2LDU has discovered that his transverter is about 12dB down in output (probably in receive sensitivity, too since the mixer is used in both modes)- it may be due to a blown mixer diode, but it is on it’s way back to DB6NT for checkout/repair and hopefully it will be back in time for the next outing!

Next, 78 GHz!

Dave Hallidy K2DH

Chairman, Rochester VHF Group