I did a regular VHF
test with a friend of mine. Both have mast
top antennas at about 17 m above water
. Distance was about 7 nm with some islands in between (not very high, but some trees). I could hear load and clear him even when he was sending at 1 W, but he could not here me at all even at 25 W with squelch set very low. I have a 11 years old Simrad
RD68 and my friend has a 8 years old Raymarine
Both systems have been working very well previously. My friend has installed an active antenna
splitter a few years ago and we both take our masts down for the winter. This was the first test after setting up the masts, maybe even after the antenna
splitter was installed to my friends boat
. My friend still hears well distant broadcasts from official stations and his AIS
receives ships even up to 70 nm. So I was certain there is something with my sending. I climbed to the mast
and took the antenna down. It is a 90 cm Glomex steel
antenna and seems to be short circuit when measured with a multimeter (well below 1 ohm). I found some rather poorly done UHF connectors, which I soldered (the outer mesh was only pushed in place) and also one 90 degree piece that had 1 ohm DC resistance for the middle pin. I measured the cabling and it had more than 20 Mohm between the pins without the antenna and 1.3 ohm with the antenna. I also opened the cover of the antenna and it was so simple that it's hard to believe there would be something wrong in it. Just a few rounds of copper wire around a plastic and a connection to the steel
Testing again with my friends boat
gave the same result. I did some test to a handheld radio
. I could hear 3 nm while the handheld was sending at low power
(1 W? It has high/mid/low) and the handheld could only hear while I was sending at 25 W (not at 1 W). So I thought there must be something wrong, since I needed more power.
While my friend went sailing I did some more test. He could not here me even at 3.5 nm. Then I set up my emergency
antenna at 5 m above water
. At the same time my friend picked up his handheld. He still could not here me with his mast top antenna + fixed VHF
, BUT he could here me with his handheld, even when it was just lying on the cockpit
seat. So he seems to have a problem with his reception
and maybe I have a problem with my sending.
I ordered a new cable, Aircell 5, to replace the 21 m of RG58 and new connectors. I haven't yet installed the new cable.
I also did some VSWR measurements (Sheakspeare) of my system. When I connected the meter at the radio
, It showed 18 W power and 1.6:1 VSWR. When I removed the 1 ohm 90 degree connector at the radio I got 20 W and 1.5:1. I also measured at the connector near the base of mast (below floor) and got 18 W and 1.2:1. My emergency
antenna showed 22 W and 3:1, so it seems to need some tuning. The emergency antenna is just a dipole made out of RG58.
So is there anything wrong with my system? Can the cabling or the antenna be bad even when I get good VSWR readings? Is it normal to need to use 25 W while the handheld only needs to use low power
? Can there be something wrong with the radio?
What about my friends boat? Can the active antenna splitter somehow spoil RX while TX still seems to work very well? Why can he still hear VTS, weather