AI4SV/6 portable VHF

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The view from Christmas Tree Point at Twin Peaks, just southwest of downtown San Francisco.

This weekend, I attended the GI Cancer Symposium in San Francisco. I had back-to-back meetings from Thursday through Saturday morning, and didn’t see the light of day for half a week. Due to the trip, I missed operating the NAQP SSB with the folks at VWS, but I did get in some VHF operating on Saturday afternoon.

When I was planning the trip, I had more or less written off operating, but then I noticed that this weekend was not only NAQP SSB, but the January ARRL VHF contest.  I have only participated in one VHF contest in the past (the June VHF contest), so I wasn’t sure about the level of participation in this contest or how well I would do working portable and QRP, but given great weather and ideal local topology for VHF, I decided the night before I left to pack the FT-817 and some antennas.

The arrow antenna, ready for packing.
The arrow antenna, ready for packing.

On previous trips, I had worked HF from Buena Vista Park, and I knew that there is a bench with a good view of the arc from the Golden Gate Bridge to Oakland. However, the bench is a little off the path, there are trees here and there in the line of sight, and couldn’t think of a good way to mount the antenna. I wanted to travel light, so I wasn’t really keen to pack a tripod.  After fiddling with Google Maps for a while, I decided that the observation point at Twin Peaks would be better. Twin Peaks are the second highest point in SF. The highest is point is not far away, Mount Davidson, which supports the Sutro Tower.  I didn’t opt for Mount Davidson because I wasn’t sure how accessible it would be and also didn’t think it would be a great idea to operate VHF/UHF right under a giant television tower. From StreetView, I had scoped out the observation point (“Christmas Tree Point”) on Twin Peaks and saw a spot with a low metal railing next to a stone wall. It looked possible to fix the antenna to the fence on a stand-off and put the radio on the stone wall.

I packed a 1×2 piece of wood, a couple screws and a bit of PVC that I had previously used to wind coils. The PVC fit over the wood and became my azimuth rotor. The cut-out in the PVC was about the right size for the central axis of my arrow antenna. When I got to the site, I found that the StreetView was accurate and I dumped the gear at the junction of the wall and fence while it was clear of tourists. Every few minutes, a tour bus would arrive, mostly with foreign tourists, who watched with curiosity as I set up.  I stopped a few times to pose for photos with them.  I taped the wood to the fence with Gorilla tape, making spacers as needed from cardboard.  I screwed some wood screws into the wood a couple inches below the top to prevent the PVC from sliding down. After assembling the arrow antenna, I put it into PVC slot and taped it into position. The radio, battery, mike and log book rested comfortably on the stone wall to the side of the fence, and I started operation on 2m.

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Configured for 70cm and pointed at the Golden Gate Bridge.

I was able to pan the antenna more than 180 degrees, starting with the Pacific Ocean to the West of the Golden Gate Bridge, swinging North and then East, panning through downtown San Francisco, Berkeley, Oakland, and then South.  I did not hit the Southwest because the top of Twin Peaks was behind me, as well as an antenna installation, mostly microwave. If I were to do this again, I might bring a tripod and climb to the top of Twin Peaks to have 360 degree coverage.

I was surprised that when I tuned around in the weak signal portion of the band (144.050-144.100 CW, 144.2-144.275 USB), that I did not hear stations working a frequency. Even odder, I heard no CW at all. All my contacts on 2m were made right on the SSB calling frequency, 144.2 Mhz. In the June contest, back in Virginia, I had heard a number of station calling on various frequencies, both CW and SSB. I thought it a reasonable chance that some one in San Francisco might be operating FM, so I rotate the antenna for vertical polarization. Again, sweeping from horizon to horizon, listening and calling on standard simplex frequencies (other than the national calling frequency, which is verboten), I didn’t hear any activity.

I tried the same thing on 70cm and contacted about the same number of stations as on two meters. Again, my only contacts were SSB at the calling frequency, 432.1 Mhz. I had to check the contest rules to reassure myself that CW was permitted, and it was — just no one doing it. I am not sure why I had so few contacts on 2m and 70cm despite having what I thought was an excellent location. I can’t say from experience if the January contest is less popular than the June one, or if perhaps there are regional differences in the popularity of the contest, with East-coasters that much more active on these bands.

In the June contest, I had parked my car on a tall parking garage and my antennas were my trunk-mounted 2m/70cm vertical and my mini-Tarheel tuned for 6m. Although these antennas were suboptimal given their limited efficiency and vertical polarization, I had some power behind them: 100W on 2m and 6m, and I believe 50W on 70cm. I had much less power this past week, running 5W, but I assumed that the two mountain-top yagis, would put out comparable EIRP to the mobile rig, albeit in a directional pattern. I assumed that the beam antennas would also be great for scanning the horizon for both strong and weaker signals.

Key: Red is 2 meter, Blue is 70 cm, and Purple is 6 meter.
Key: Red is 2 meter, Blue is 70 cm, and Purple is 6 meter.

I noticed that all of the SSB stations SSB sounded strong. This would make more sense if I had been operating FM, but I expected to hear a range of SSB signal strengths from scratchy to booming. I realize that my QRP signal might not have sounded similarly strong to them, but I can’t account for not hearing some stations that were softer, unless my background noise level was higher than I appreciated. I suppose that being on a hill surrounded by other antennas might have had some negative effect on reception, but I don’t think this is the case. I would really doubt that this could affect CW so much that I wouldn’t have heard even one signal. I noted that many of the stations that I did work indicated that they had what I’d consider to be elaborate VHF set ups: large permanent, rotatable antennas, high power, and so on, so I am wondering if these stations are just used to working only strong signal stations.

After a while, I disassembled the arrow antenna and wandered a bit further up the hill towards a pine tree. The night before leaving for SFO, I had made a 6m dipole using the usual formula. I didn’t have time to test it, but just coiled it up and chucked it in my luggage. I threw a couple ropes about 15 feet up in to the tree (about the length of my coax) and suspended the antenna horizontally, roughly east-west so it could be broadside to downtown San Francisco. The computer bag that had contained everything became my seat. Again, I hit a number of stations on 50.125, the CW calling frequency, but only heard a couple more up around 50.135 and 50.140. I was determined to bag at least one CW contact, which I did, KJ6M. I’m not sure if he was in the contest or just scanning by the CW portion of the band, but I’m glad he was listening.

I got excited at one point that I had broken out of local area when one station on 6m indicated a QTH of Nevada. I thought maybe 6 meters was opening up and tried to figure out, with my limited recall of Western US geography, what sort of propagation would land a 6m signal in Nevada. The more I thought about it, the less it made sense, particularly since the station had a W6 call. When I got back to the hotel that evening, it made more sense: Novato, California. Not as far as I had hoped. Nonetheless, I had two contacts at a range typical range: a 6m contact at 143 miles and, more surprisingly, a 2m contact of 137 miles.

6mantennaSince I got out of my conference around noon and had to go back to the hotel to change, grab a quick bite and collect the radio equipment, I splurged for a cab ride up the mountain because I was concerned about the amount of daylight I’d have for operating. It felt like I was cheating, but this wasn’t a SOTA activation, my time table, and the fact that I have limited familiarity with getting around in San Francisco. As the cab dropped me near the summit, he asked how I’d get down, and I indicated that I’d figure something out. I was sorely tempted to just blend in with a tour bus crown and head back down the mountain, but after plugging away for a few hours, I still had enough light to walk down the mountain (much easier in that direction) and take a bus to Castro, where I was able to hop on one of the Market Street trams, which I rode just about to the front door of my hotel. The $2.00 return trip made me feel better about taking a cab on the outbound leg.

Without the 6m opening, I made a lot fewer contacts in this contest than I had in June. So, plans for future VHF contests? Yes, probably, depending how busy I am in June. Working the contest from Skyline drive and combining a gain antenna with the higher power output from the car’s transceiver sounds like a winning combination.

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