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102” HELP!!!
- Thread starter BammBamm
- Start date
I believe that the moneys saved by saving one radio is me justification.
Well I tell my wife that, and it's good for her. I like to see my Reflect needle sitting in the safe zone. And it's fun to have stuff...
Also these reading are being taken with a MFJ-826b meter. I’m afraid of damaging radio but one thing I’m finding is that my internal swr meter in radio is within .05 of the MFJ! I am about to leave to go see my tech.
remember that a 1/4 wave antenna has a characteristic impedance of 36 ohms, and will read about a 1.4 to 1.6 SWR when working correctly.
a 102" whip should never be trimmed. attempting to get the SWR down to the 1.1 level will only result in you fooling your meter and taking the antenna out of resonance.
the fact that it raises to 2+ with the amp on most likely means that you have out of band harmonics being created either by the amp, or by the radio and being amplified by the amp.
if you have a low pass filter, you can put it after the amp and see if that improves things.
if it does, your amp is putting out harmonics along with the fundamental signal.
LC
a 102" whip should never be trimmed. attempting to get the SWR down to the 1.1 level will only result in you fooling your meter and taking the antenna out of resonance.
the fact that it raises to 2+ with the amp on most likely means that you have out of band harmonics being created either by the amp, or by the radio and being amplified by the amp.
if you have a low pass filter, you can put it after the amp and see if that improves things.
if it does, your amp is putting out harmonics along with the fundamental signal.
LC
No it was dropping with amp on. Replaced spring and coax jumper to amp and got it to 1.4 and 1.6 with or without amp.
Thank you everyone for all the help. Although I’m smacking trees in my subdivision once I’m out of it I barely ever hit anything. I know I’m over the “legal” height but haven’t had an issue yet. I keep hearing that 108” is the correct length...is this a ball mount with spring and antenna? Just the spring and antenna is about 106.25”.
yes, the 108" number comes from a 2" ball mount, a 4" spring, and a 102" whip.
as long as your SWR stays like it was, at 1.4 to 1.6 you are good to go.
LC
as long as your SWR stays like it was, at 1.4 to 1.6 you are good to go.
LC
Have a couple of 102” whips on order. As earlier in the thread was raised issue of potbelly spring quality — and I need a new pair — I got to searching around. Some old goat with a gigantic mag mount on a Chevy vans roof said he had found a spring source for his expensive antenna:
Cal-Av
Great, I thought, and stumbled over there . . . whoa, the 6” springs START at over $100.
Note: They recommend treating braid with some drops of LP-S for longevity.
.
Cal-Av
Great, I thought, and stumbled over there . . . whoa, the 6” springs START at over $100.
Note: They recommend treating braid with some drops of LP-S for longevity.
.
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Ran a 108' whip off a breedlove ball mount for a few years.. 2950 & 2 pill... best mobile setup I ever had. Lots of fun last cycle!
http://www.mfjenterprises.com/Product.php?productid=MFJ-1966
http://www.mfjenterprises.com/Product.php?productid=MFJ-1966
There's also a way to flatten the SWR on a 102" whip that works pretty well, I used to cut something a tech that I used to know would call a "beta loop". Basically you would take la single length of about maybe 8" of 12GA solid wire, I usually used insulated stuff like out of romex. Bend it into a V shape where the bend is in the middle of the two terminals. Then we would crimp ring terminals on the end one goes to ground/mount plate of antenna other goes to the center conductor.
I think this is the principle which its based on...
https://owenduffy.net/calc/shuntmatch.htm
I dunno how lossy these things are, etc, but for many years a friend of mine had a 102" on his truck on a mounting plate, and this is how we got the SWR to not be obnoxious. 1.5+ is horrendously terrible in modern gear, if there is any loss, at all, the advantage of not pissing off the radio or amp is worth it. He always had a killer signal with that thing with only 100W or so out of his 706mkII. We used a previou setup on his other truck but that one used a coaxial stub with a T connector, which was more broadbanded, I suspect that setup had more loss but the bandwidth was crazy out of that thing.
I think this is the principle which its based on...
https://owenduffy.net/calc/shuntmatch.htm
I dunno how lossy these things are, etc, but for many years a friend of mine had a 102" on his truck on a mounting plate, and this is how we got the SWR to not be obnoxious. 1.5+ is horrendously terrible in modern gear, if there is any loss, at all, the advantage of not pissing off the radio or amp is worth it. He always had a killer signal with that thing with only 100W or so out of his 706mkII. We used a previou setup on his other truck but that one used a coaxial stub with a T connector, which was more broadbanded, I suspect that setup had more loss but the bandwidth was crazy out of that thing.