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How to choose base antenna?

A place to ask questions about base setups.

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MightyMo
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How to choose base antenna?

Post by MightyMo » Saturday, 07 October 2017, 12:57 PM

I'm in the market for a base antenna. When it comes to mobile antennas it seems that the 102" whip is the best an all others try to perform as good as that. What about base antennas? Is the 102 whip (with ground plane) still king?
I read online that some antennas that are good for DX (over 1500 miles) won't be as good for contacts less than that.
What are your recommendations? Where do I start?

Thanks


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MDYoungblood
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Re: How to choose base antenna?

Post by MDYoungblood » Saturday, 07 October 2017, 16:08 PM

It really all depends on what your looking for. I am happy with a 5/8th wave ground plane antenna. You can pick one up for around $150 and the ones built like a tank can soar to more then $500. A bean antenna can go the same way.
Since I don't have room for a beam I will just talk about a omni ground plane. The plane lowers the angle of radiation from the antenna, giving you a little more distance to the horizon, so the higher you put it the farther you will talk giving your surroundings. During skip conditions, it really doesn't matter in height of the antenna, I've talked all over using a dipole 8ft off the ground.
The last thing to look at is will it handle the wattage you plan to use, most antennas will handle a modest amount with out a problem, don't believe all those 2K claims, thinking of big watts then the more expensive antennas are what to look at.

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MightyMo
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Re: How to choose base antenna?

Post by MightyMo » Saturday, 07 October 2017, 23:54 PM

I think I'm going to be looking for a 5/8 omnidirectional antenna. I saw a recommendation for MFJ Hy-Gain SPT-500 on a random site I was looking at, but he didn't really say why he recommended it. I've also been looking at a couple antennas from Sirio. I was looking at the "Sirio 827 (26.4 - 28.4 Mhz) CB/10M 3000W Tunable Base Antenna". But the "Sirio 2016 (26.4 - 28.2 Mhz) Tunable Base Antenna" looks identical to me except there is a $2 price difference.
I've noticed some have 4 elements for the ground plane where other antennas have 6 or 8. Does the number of ground plane elements make a difference in antenna or signal quality?

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MDYoungblood
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Re: How to choose base antenna?

Post by MDYoungblood » Sunday, 08 October 2017, 9:22 AM

The HyGain is a good antenna, the long radials do make a difference. Not sure about the difference in the 2 Sirio antennas but I would look at the Sirio Vector 4000, more height and the same price as the HyGain. Look at DNJ's website for the best prices on the Sirio antennas and tell him your a member here.

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Uniden Washington
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Texas Ranger TR-696FD1C
Handheld
Maxon HCB-40WX
Antennas
Avanti Sigma II
Homemade Full Wave Loop
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Hustler 102" SS Whip and Hustler Ball Mount

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De_Wildfire
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Re: How to choose base antenna?

Post by De_Wildfire » Saturday, 21 October 2017, 17:00 PM

I run the Imax 2000 on a 13 foot pole and worked Japan, New Zealand and Europe. It's about the take off angle.


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Re: How to choose base antenna?

Post by jessejamesdallas » Saturday, 21 October 2017, 17:56 PM

If you have plenty of land to put it on...Get the biggest antenna you can find, and talk to the World!...(and other Worlds) :mrgreen:

"Go Big, or Go Home"

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The DB
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Re: How to choose base antenna?

Post by The DB » Sunday, 22 October 2017, 13:32 PM

What you should look for is the antennas tip height. Its not actually length, in and of itself, that causes longer vertical antennas to outperform shorter vertical antennas, it is getting the part of the antenna that radiates the most further above the earth below.

The part of the antenna that radiates the most on a CB antenna is the area between 102 and 108 inches down from the tip of a vertical antenna (with a few specific exceptions). A smaller antenna whos tip is mounted higher than a longer antenna will outperform said longer antenna, even though it is shorter.

Effectively, all length is is a way to get a small amount of additional height for said part of the antenna that radiates more than any other part over a shorter antenna, however that only works to a point, namely 5/8 wavelength antennas (and by extension what some people sometimes treat as the "almighty" .64 wavelength antennas) with rare exception. That length (specifically the part that is longer than 1/2 wavelength) also comes at a price.

For those who are obsessed with an antennas "take off angle", the higher the antenna's tip, the lower the antenna's take off angle, which is why 5/8 wavelength antennas are said to have a lower "take off angle" than shorter antennas. This is something that gets far overstated by most of the people who talk about it. Also, as a general rule, if you double the height of the antenna's tip, the "take off angle" will be about cut in half. For example, an antenna that is 60 foot to its tip will have a "take off angle" that is half of an antenna that is 30 foot to its tip. This is a fancy way of saying that adding height to an antenna gives diminishing returns. Once you get to a point, it gets more and more expensive to make increasingly small changes to the antenna's "take off angle". This also tells us that the difference between two different lengths of antenna will be less noticeable the higher said antennas are mounted.

You will note, I put the phrase "take off angle" in quotes every time I typed it. The reason for that is if you do everything else right, and you get your antenna high enough, the "take off angle" is something that, in my experience, will simply fall in line on its own. Unless you are planning on mounting the antenna at earth level (if you are you really need to ask more questions), it just isn't something that you need to worry about.


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Re: How to choose base antenna?

Post by Scipio Kid » Monday, 23 October 2017, 8:45 AM

Hey Mo!
I've been seeing your ads from time to time and calling for you when I'm up north. I'm sure I heard you the other day but the rig I was driving was having trouble with the CB and I wasn't getting out very far. (Either that or you were just ignoring me ... I get a lot of that.)

Well, it seems all we’ve ever heard since the good ol’ days has been bigger and higher, bigger and higher. Those two factors, more than anything else, seem to be the best formula for “getting out” and others “getting in”. DB gave you theory followed by practical advice. Theory is great until it meets with reality and practicality. For instance, having a .64 wave antenna is great, unless you live in a basement apartment with no allowance for external antennas. In such a case, many of the ingenious members of the forum have come up with clever ways to use smaller mobile antennas disguised as everything from awning supports to flagpoles. While these solutions won’t get out as well as the .64, the .64 won’t get out at all, it’ll just sit in storage.

The biggest antenna you can find, mounted atop the highest mast you can imagine would certainly be the best way to “get out”. There is your standard. Then practicality has to come into the picture. As DB points out, a good antenna on a 30’ mast will work almost as well as it would on a 100’ mast. But the cost of the 100-footer would be astronomical (and likely illegal in most areas). Likewise, a real nice .64 wave antenna mounted at ground level wouldn’t perform as well as a homemade dipole in the attic. There will always be tradeoffs.

Back in the 70’s we had a ¼ wave ground plane antenna on the top of our shop and it worked great for our needs. Our foreman came in one day and said he’d found a great deal on a .64 wave and we jumped on it. Since we now had the “big” antenna, we made up a mast to put it 15’ higher than the old one as well. It was a lot of work but we thought it was worth it to get bigger and higher. But, after all that work, there wasn’t much difference. We had power lines and big trees all around us and the bigger antenna and the extra 15’ didn’t do much to overcome those obstacles. Ironically, I took the old ¼ wave antenna and mounted it to the top of my dad’s chimney and set up a base station there at his house. Amazingly, that setup seemed twice as powerful as the one at the shop. The difference was no interference with trees or power lines and his house was on the mountain side 1000’ higher in elevation than the shop.

We never thought of running linears back then. Uncle Charlie was a real threat to anything over 4 watts. We actually had an agent follow the signal to the house one evening, claiming we were using a linear. He’d tracked us for 15 miles with his rangefinder. We showed him our “barefoot” Sears Roadtalker Base Station and he chuckled and said, “you’ve got a nice setup here boys”. Well, it really wasn’t any different than any other CB setup other than the extra 1000 feet of elevation we got due to our location. I’m sure if we’d put up a 1000’ mast at the shop, it’d have done just as well. Back then, there were antennas of all sorts on top of every house. Today you can’t do that. My home is higher in elevation than Dad’s was but it’s illegal to put even a TV antenna on the roof. So, my base antenna is hidden in a tree and even when amplified, doesn’t do nearly as well as that old ¼ wave did up on Dad’s chimney.

The best setup I’ve ever had is out in the desert (in the middle of Cedar Valley) where we have an equipment yard. We put a 102” SS whip on top of an old semi-trailer (full aluminum roof for a ground plane) and even though it’s only 15’ off the ground, it’s the highest point for 10 miles in any direction. That thing talks & receives all over the world on AM. I can talk with truckers on I-15, 25 miles away and they think I’m on the road with them and I’m running barefoot out there too. (Got a new SSB to put out there when I get a chance and a little Texas Star amp as well. We’ll see if we can talk to some of the forum members back east on 38 LSB when we get it all set up.)

Anyway, once you’ve considered theory, then start thinking practicality. What will work best given my local, ordinances and budget? I picked up an old 5/8 wave down in Spanish Fork a couple weeks ago. The guy wanted a lot for it but I pointed out the top of the mast was missing and offered him 15 bucks. For 20 he said he'd throw in the 50' of HD coax so I took it. I found the aluminum tubing I need to fix it at Metal Mart there in Lehi. Now all I have to do is get practical and find a way to put it on my roof without the neighbors or P.M. patrol noticing it. Something like that would work great for you up on Washington Terrace. If you can set up a good ground plane with your 102" whip, you'll be impressed with the performance. I have a couple extra if you need one.
Happy Trails




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