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VHF cable type?
On Sun, 18 Jan 2004 21:38:20 -0500, wrote:
My radio experience is painfully limited...as a teen in the '70s I ran
a 40 channel CB base station and used RG-8U...soldered my own
connections and all and put up a free-standing 30 foot tower and
directional antenna (squeaky pulley!). I know 58U was for cars, and
there was no way I was running expensive and heavy 8U up my mast, so I
used 58A/U for the 50 foot run from mast head to a splitter (for AM/FM
radio) under a settee and a further 10 feet to my VHF unit at the nav
station.
The various CB myths and cult followings wreaks havoc marine VHF is my
experience. Man, they got some strange physics education on CB....(c;
The gain in altitude (altitude is very important and the reason TV
stations have 2000' tall towers) is FAR more important than a few dB
loss in any kind of cabling. One of these days, I'm going to put up a
Metz on top of a 50' mast fed with RG-174/U, the tiny coax cable used
for connecting internal cables of equipment. Back 20 years ago, I got
a free 1000' roll of it from some ham or another. I never turn down
free stuff. The house is full of it, a regular packrat. Anyways, I
needed an extra antenna centered on 4585 Khz to use for the local CAP
squadron's HF comms I'd gotten my self mixed up in because a good
friend was the squadron commander and had no radio ops. Hell, it's
only 4.5 Mhz and only 100 watts of power, so use what's available. I
hung an inverted-V (dipole) from a pine tree by shooting an arrow over
a high limb with a borrowed bow....after many attempts, I might add.
The tiny RG-174 simple fed the center insulator. To my amazement, it
worked great on 4585 USB. Way early in the mornings, I could check
into the CAP net in Hawaii, causing quite a ruckus of Hawaiian
stations wanting to try to work SC DX. I got to using this big roll
for portable antennas at the local ARRL Field Day when hams camp out
on generators to see how many stations we can contact in 24 hours, a
contest.
The reality of it is a compromise between practicality and function.
Look at any receiver that has a calibrated S-meter. Notice the
calibrations are in 10 dB increments. 3 dB isn't much difference
indeed. Back to the chart someone quoted, the difference on 156 Mhz
between 8X and RG-58, which is so much easier to thread through a
boat, is less than 2 dB per HUNDRED ft. 1 dB for half of that. The
guys at the receiving end won't tell the difference.....er, ah, unless
you short out that big cable trying to bend it too sharp around the
corners...(c; It's fine....
Larry W4CSC
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