Last Updated on November 6, 2020 by KC7NYR
This past summer 2018, on one of my family’s ocean fishing trips I took along one of my Baofeng’s UV-5R radios. One reason was to have another means of communication, but the main purpose was to test propagation of VHF/UHF over water and to see how far away I could get into a specific repeater.
We departed from the mouth of the Salmon River, just a few miles north of Lincoln City on the Oregon Coast. We were making a run for Tuna so I knew we’d be going out pretty fair and this would give me an opportunity to test just how far out I could be and get into one of my favorite repeaters.
The repeater, there are two actually, is located on South Saddle Mountain. ARRG, a local repeater group in the Portland area, operates and maintains a VHF/UHF linked pair of repeaters at S. Saddle Mt. The VHF frequency is 147.320 MHz and the UHF frequency is 442.325 MHz.
On the way to our fishing spot I was able to do a little testing to see if I could get into the repeater system. Within 5 miles of shore I was not able to bring up either one of the repeaters. Once we got out to about 5 miles, I was able to bring up both the VHF and UHF side of the repeater system. Being that it was zero-dark-thirty in the morning, no one was on the system to get a signal report back. Due to the ocean conditions I was not able to do any further testing while we continued to our fishing spot.
Once we reached our final fishing location, we had a little down time between catching fish as one usually does. During one of the lulls in the fishing, I grabbed the radio to test again. At this point we were located 25 miles pretty much due West from the mouth of the Salmon River and about 70 miles from the repeater site.
Being so far out, I tried the VHF repeater thinking it would have the best chance of hearing me. I keyed up the radio, threw out my callsign and unkeyed…nothing back from the repeater and no return call. I tried a few more times just to make sure, still nothing. I wasn’t surprised given the distance, the fact I was running 5-watts through an HT with an 18-inch whip antenna.
I changed channels to the UHF side of the repeater system and tried again. Much to my surprise, when I unkeyed I heard the repeater come back to me. Not only was I able to hear the repeater comeback, Marc W7PM, located in Beaverton Oregon at the time, was listening and he came back to me. We held a quick QSO consisting primarily of location and signal report. While there was noise on the signal, we both were perfectly readable to one another, one might give it a 5 by 7 signal report.
For further reading on the topic of Radio wave propagation at VHF/UHF, I would recommend reading – The propagation of VHF and UHF radio waves over sea paths by Chow Yen Desmond Sim. To download the pdf document click on 2002SimCYDPhD.
Moreover, there is relatively very little published on equivalent propagation over the sea for both VHF/UHF when the direct path is obstructed by the sea surface. The propagation path over sea is very different from over land, as the atmospheric conditions over the sea are the dominant influence of the propagation characteristics.
HF/UHF and microwave signals can travel distances beyond the horizon under certain atmospheric conditions. Depending on the state of condition in the atmosphere, radio propagation between the transmitter and the receiver may occur by the mechanisms of scattering, reflection, refraction, diffraction and tropospheric ducting. It is generally agreed that the radio-meteorological situation in the coastal areas can produce complicated structures due to the interaction between the sea and the land.
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