Presidio POTA (US-7889) inside Golden Gate NRA (US-0647) — QRP CW, transit, and a surprise eyeball QSO

Live portable ham radio from San Francisco’s Presidio with a clean take-off toward the Pacific. Route via PresidiGo, light wire vertical, and a crystal-locked 14.0574 MHz start. I keep local times in the story; the QSO map is in UTC.

I arrived downtown at Embarcadero Station at 15:20 PST yesterday with Project Toucans, a portable ham radio. There was a newly married couple, still in their dress and tux, waiting to ride the cable car up towards California and Powell. I was waiting for the PresidiGo bus out to the Presidio.

Golden Gate Bridge from the Presidio with coastal scrub in the foreground — staging area for POTA activation US-7889 inside US-0647](IMG_GGB_WIDE

It's a free bus out to the park that passes through downtown several times a day.

PresidiGo Downtown Loop showing 1-minute arrival at Drumm/California, Monday holiday and Free badges visible

I hopped on the bus at 4 PM downtown. After a few stops at 4:07 PM PST, the bus was completely full. Interestingly, when we arrived at the first Presidio stop at 4:15, almost everyone got off and exited the Presidio back towards town. I don't know why.

The bus winded through the rest of the Presidio towards the transit center. The center is right in front of the new park, called Tunnel Tops. It's a bit confusing because there was already a park in town, (and still is), called Tunnel Tops. So it goes.

By 5:02 PM PST, the rig was setup and transmitting as I broadcast the control panel for the radio on a YouTube livesream, and my Morse code on 14057.4 kHz.

I've talked to W6CSN another ham in town who does POTA's, but I'd never met him in person, so it was a big surprise when he walked upt at 5:27. By then I'd QSO'ed with AL7KC form AK, K2UPD from NY, WZ0D from CO, and WQ7O from Washington. I took a break and we talked radios. Later in the afternoon, I heard from W6CSN on the radio from across the park!

Getting back to the park, i managed to set up things in a pretty compact and convenient way. The lawn in in the middle of the park is covered with plastic chairs. I electrical tpaed the veriical antenna mast to one of them.

Seat-mounted antenna setup on the red chair with lightweight mast/wire vertical; QRP station laid out on the grass

I ran the counterpoise along the edge of the chair .The rig is tucked behind the chair.

The second QSO to NY was a bit odd for the afternoon from San Francisco. I haven't worked out for certain what did happen, here's the FoF2 and hmF2 map between San Francisco and New York at the time of the QSO.

You can see that the F2 layer is really dense over SF, Nevada, and Utah at the time as indicated by the high crticial frequency. That ususally forces Project TouCan's signal back down into Utah until the sun goeas down. You can see that there's a big gradient in the F2 along the path from SF to NY. It drops several levels from white to green and then stright through to yellow and red. I believe the signal made it across the country on a path like path five shown below in teh diagram from the Department of Commerce's 1960s book on ionospheric propagation.

Six ionospheric ray paths launched from the same point at increasing elevation angles. Paths 1–2 are low rays with long ground range, path 3 reaches the skip distance, paths 4–5 are high rays reflecting near the F2 peak, and path 6 penetrates the ionosphere. Skip zone labeled between transmitter and first return.

"In figure 4.6 we see what happens to the ray path (on a given fre-quency) as the angle of elevation (takeoff) slowly increases. For low angles the propagation path 1 is long. As the elevation increases, the ground range (path 2) decreases until the skip is reached (path 3), after penetration occurs as shown by path 6. Paths 1 and 2 are the low-ray paths and 4 and 5 are the high-ray paths. The variation of ground range D with angle of incidence 0o for a parabolic layer is sketched in figure 4.7

Graph of ground range D versus incidence angle φ₀ showing two branches: a 'low ray' and a 'high ray' separated by a minimum marked skip distance. Curves for f/fc = 1, 1.25, and 3 illustrate how range changes with frequency; the high-ray branch rises steeply, indicating strong sensitivity to small angle changes.

for various ratios of the operating frequency to the penetration frequency. Note that for a given distance there are two values of one corresponding to the low-angle path and the other to the high-angle path. The minimum distance is the skip distance. Note that the high-angle ray is very sensitive tochanges in phi_nought."

QSO Map

The map below shows all the QSOs at the beginning. By moving the slider or clicking the play button, you an watch the QSOs as they folded out.

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