I run mine with the Sirio Mag mount on the roof. Its is a awesome antenna. I have it back on the truck now and works great. They come through and cleared out some limbs on the road. It does also work with my new carport. All is good.
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Best shortest mobile CB antenna??
- Thread starter Galaxy 959
- Start date
Basically all mobile antennas are a 1/4 wave.
Some use up part of that length in a coil.
Some have the coil on the bottom, some in the middle, some nearer the top (Hustler).
Raising the coil away from the metal of the car body helps the coil efficiency and also tends to lower the take off angle.
In the mountains I'd prefer a full 1/4 wave or a base-loaded so I would get up and over tree-lined ridges better.
In the city it's a crap-shoot with buildings, freeway overpasses, heavily treed neighborhoods, all trying to suck up your signal from your 10' high current radiator.
For the best shorty, I'd have to go with a slightly elevated coil, and as long a whip as you can get away with.
The longer the whip, the more efficient the antenna - needs less coil.
- Maybe 8"-10" of shaft, then the coil, then at least 4' of whip and you should do well.
On my "Point-n-Go Econo-Coffin" (Honda) I use a Wilson trucker 5K with a 9" shaft and about a 4' whip.
Beats the old Sirio 5k & Wilson 5K hands-down, and even when I'm headed up camping it seems to get out at least as well in the mountains & valleys near Tahoe as do the base-loaded styles.
I use a 4-Mag mount for it so I have little trouble with it being knocked off.
Just try to stay away from coils with metal on top &/or beneath, ie: ANTENNA - Worst performing antenna I ever owned. SWR was decent, 1.3:1 best, but just didn't perform at all.
Some use up part of that length in a coil.
Some have the coil on the bottom, some in the middle, some nearer the top (Hustler).
Raising the coil away from the metal of the car body helps the coil efficiency and also tends to lower the take off angle.
In the mountains I'd prefer a full 1/4 wave or a base-loaded so I would get up and over tree-lined ridges better.
In the city it's a crap-shoot with buildings, freeway overpasses, heavily treed neighborhoods, all trying to suck up your signal from your 10' high current radiator.
For the best shorty, I'd have to go with a slightly elevated coil, and as long a whip as you can get away with.
The longer the whip, the more efficient the antenna - needs less coil.
- Maybe 8"-10" of shaft, then the coil, then at least 4' of whip and you should do well.
On my "Point-n-Go Econo-Coffin" (Honda) I use a Wilson trucker 5K with a 9" shaft and about a 4' whip.
Beats the old Sirio 5k & Wilson 5K hands-down, and even when I'm headed up camping it seems to get out at least as well in the mountains & valleys near Tahoe as do the base-loaded styles.
I use a 4-Mag mount for it so I have little trouble with it being knocked off.
Just try to stay away from coils with metal on top &/or beneath, ie: ANTENNA - Worst performing antenna I ever owned. SWR was decent, 1.3:1 best, but just didn't perform at all.
Huh? All commercial antennas are made to be resonant by manipulating the radiating resistance thru changing the inductive and capacitive reactance. In theory, you can make a very short antenna resonant so long as the coil (inductance) and capacitance are tuned properly.
Doesn't mean it will have desirable specs either, such as optimal bandwidth and radiation pattern. Shorter also means more loss because the parts that are used to create a match will also rob power from what is being radiated. A longer, natural length radiator (ie 1/4 wave length) also has unity gain, where a shorter, less efficient antenna will also have less effective radiated power. A short antenna - less than a 1/4 wave - gets less and less desirable as it becomes shorter. The Sirio 5000 is the longest compromise of a 1/4 on the market, unless you build your own 1/4 wave - IMO . . .
Not dissing you; just don't get where you are coming from.
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What do you think of this bad boy?
It looks like some crazy oil coil abortion.What do you think of this bad boy?
Very nice... I am still weighing my options on the mobile setup.. I have everything here ready to go but now I am in the process of getting my base setup first.. I am waiting for my friend to give me a hand, getting that antenna 60 feet up on the air is not going to be easy, but we will get er done..What do you think of this bad boy?
OK, well, when you shorten an antenna by cutting some length from a resonant 1/4 wave, you introduce capacitive reactance - requiring the addition of inductive reactance (COIL) to nullify/ balance reactances so the load (antenna) becomes as close to a purely resistive load as possible.
The coil diameter, form factor (ratio of diam to length), number of turns, height of the coil above the car body, size of coil wire, spacing of turns, amount of length the antenna is shortened, ratio of top whip length to bottom shaft length, stray capacitance due to insulation, dielectric, etc...
- these are just some of the parameters to consider when designing a coil-shortened or "Loaded" antenna.
My favorite mobile antenna "creation" which I made from odds & ends in the shop, has about a 3MHz bandwidth @ 2:1, and outperforms a 102" whip (and all other antennas tested against it - all of which were also mounted atop the center of the roof) - to a local internet-linked receiver approximately 12 miles away.
At center (tuned) freq it's:
X=0/1
SWR = 1.0:1/ 1.1:1
R=49/50Ω
...I do alright
Hey rabbiporkchop, Try a Wilson Trucker 2000 in place of that oil-coil, I bet you'll like the improvement in performance.What do you think of this bad boy?
Ring and pinion needed to be replaced so the whole axle was at the shop when the picture was taken
Unfortunately Wilson doesn't offer a four foot shaft. I'm sure you are correct that if I was to replace the load with a Wilson load there would be an improvement with the air dielectric inside the coil assuming I used the same 4-foot shaft
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That truck doesn't belong to me it happens to belong to another one of Mark's customers who lives about an hour and a half south east of me. I just donated some odds and ends to him to make sure his station was operating at Peak efficiency so we can have some fun on the airwaves in the near future and make some videos.Very nice... I am still weighing my options on the mobile setup.. I have everything here ready to go but now I am in the process of getting my base setup first.. I am waiting for my friend to give me a hand, getting that antenna 60 feet up on the air is not going to be easy, but we will get er done..
That's amazing! In fact hard to believe, a coil loaded antenna with 3 MHz of bandwidth. Last time I checked a 1/4 wave whip didn't come close to that!
Just because a shortened coil loaded antenna has great bandwidth, it doesn't mean it has great radiating power efficiency. In fact, it is probably more of a leaking dummy load since it is buried in inductance from the coil itself.
Do you have a REAL antenna analyzer or other means that can back up that claim showing that kind of bandwidth?
What I would like to see is a SWR plot graph like this one pictured below done with my Rigexpert AA54 analyzer and a short coax jumper at the antenna checking the bandwidth on a Sirio 5000 trucker series mobile antenna. The numbers may be a little hard to read in the pic but it shows at center frequency of 26.320 MHz for the lowest SWR with the scanning preset for 1000KHz, the bandwidth is clearly just over 1 MHz below 2.1 SWR.
And here are all the numbers after scanning for bandwidth.
Depends on the losses. If its a very lossy installation/coil then you could get something like that.
Not lossy at all, at ~12 miles it beats the 1/4 wave whip!
It required several days of calcs & trial/error in building. Bringing calculations to life in the real world is sometimes a daunting task when it comes to fashioning materials to make them do what you want.
Looks like Sirio did a fine job on that trucker. What length & type of coax did you use to connect it to the analyzer?
I'm extremely happy with the final outcome of mine to the degree that I hassle bringing it inside the garage at night in fear it might get (randomly) stolen and I'd lose my beloved prototype.
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