On Tue, 27 Nov 2018 21:42:22 -0500, "Mr. Luddite"
wrote:

On 11/27/2018 7:36 PM, wrote:
On Tue, 27 Nov 2018 17:47:44 -0500, "Mr. Luddite"
wrote:

On 11/27/2018 5:22 PM, wrote:

I have a uniden CB radio (new) and have an existing larsen wb vhf radio already on my truck. Will this antenna work with my new radio.
Derek


Can't determine without knowing what freq range the truck antenna is
"cut" for. There are two VHF bands, low-band VHF (49-108 MHz),
high-band VHF (169-216 MHz). Marine radios operate in the high band.

Generally it will receive ok but transmit range may be limited due to
high standing wave ratio (SWR).

Even a marine VHF antenna should be tweaked in terms of length to
minimize SWR in the middle of the radio's freq range.


He is talking about CB (27mz) so that is over twice the wavelength of
the lowest frequency VHF.
SWR is really going to be ugly but since they are capped at 5w,
(usually more like 4.5) I doubt the magic smoke comes out but he won't
be "getting out" far either.

If his "truck" is a real one (breaker good buddy size) and he has 8-9'
from mirror to mirror the best antenna is the co phasers you see on
big rigs. Otherwise it is hard to beat a bottom coil loaded ~48"
antenna right in the center of the roof. That is what I had on my van
but you had to remember to take off the vertical when you went into a
parking garage. ;-)



I completely missed that it was a CB radio he was talking about.
Thought he was talking about a new VHF Marine radio. But the antenna
issues remain the same. For max range whatever antenna he uses needs to
be of the proper length. At 27 MHz a full wavelength is about 103
inches. A half wave antenna would be about 51.5 inches long and
aquarter wave length antenna would therefore be about 25.75
inches.

If really anal about these things, an SWR meter should then used to trim
the antenna length to the lowest SWR on channel 20 (mid-range).

I have an old SWR meter from the CB craze years that I never use anymore
but for some reason it's one of those things I just can't throw away.

I used to just buy what they had at Radio shack or something but my
old 3d shift partner was a Ham/Navy ET so I got pretty good guidance.
;-)
He was an RF wizard.
He was the guy who left FE, went to IBM FSD, Lockheed, Loral and
worked in Germany for a decade or two and now retired in Colorado.
http://gfretwell.com/ftp/colorado/Greg%20and%20John.jpg
Three old guys on the top of the hill behind John's house, next to the
fence to Rocky Mountain Federal Park.
Another Navy guy doing well! I hope "Dutch" (the dog) is still OK
;-)