Base Antenna Basics...

[jcrmadden]

What are the fundamental considerations for a base antenna?

I'm kicking around the idea of putting up a base antenna. Just to get started I'll run my mobile unit and my "shack" will be my truck.

I've read several threads regarding antennas and masts in different sub-forums. The information seems disjointed and in some instances contradictory (differing opinions aside).

End feed, random wire, dipole, beam, vertical, horizontal, inverted...

Mast height? Antenna length? Radials? Grounding? Is there an ideal setup for 11M?

I feel like I don't know enough to even ask the right questions.

So, my question here is, "what questions should I be asking?"

 

[prcguy]

Do you want to build something or buy one? For local stuff or skip?

For best success I would buy a well known proven base antenna and there are many good and bad opinions on this. For me a Hy-Gain Penetrator is one of the best with similar 5/8 over ground radial types being very good. Maco makes a similar model, the Sirio 2016 5/8 with a bunch of short ground radials are good, the IMAX 2000 has great reports and there are many others. Bottom line here is bigger is usually better and tiny antennas for CB usually suck.

If you want to roll your own you can make a simple 1/2 wave dipole for almost free and it can talk skip all day long very well as a flat top or inverted V, but since that is mostly horizontally polarized it won't do well for local comms. Ideal heights are placing the high current part of the antenna at 1/2 wavelength points above the ground like 18ft, 36ft, 54ft, etc. The high current point of a dipole or 1/4 wave ground plane would be near the feed point and for a 1/2 wave vertical antenna like an A99 would be in the middle.

For grounding look up NEC article 810 which deals specifically with antenna grounding and you can find many examples online.

 

[WSAC829]

Bottom line here is bigger is usually better and tiny antennas for CB usually suck.

That is subjective. Everyones setup is different, and some work better than others. I’ve now tried 2 “real” base antennas over the years (Antron 99 and just recently a Sirio GPS27) and both suck compared to smaller “mobile” antennas. Why you ask? Noise floor. Both base antennas had no ears because of a constant S3-S5 noise floor. I couldn’t hear my locals 40-60 miles away. My 102” whip mounted on an 8 foot pole behind my garage has an S1 noise floor, and the 4.5 foot Tram 717 on a mag mount that i'm now using on the house (attached to metal roof fascia) also has an S1 noise floor. Both have an SWR of 1.0-1.1 across the band. I can talk on SSB locally to guys 60 miles away with both of those antennas, or roughly 25 miles on AM. No issue shooting skip either.

As i said, everybody has different success stories. That’s mine. 3 different houses, 2 different base antennas, and at one point even bought a 40 foot tower, and same issue. No "weak station” ears. I always resort back to the 102” whip as it beats the base antennas for long distance local communications all day long.

 

[Backwoods40]

I’ve now tried 2 “real” base antennas over the years (Antron 99 and just recently a Sirio GPS27) and both suck compared to smaller “mobile” antennas

That's what I'm concerned about.
I've had the most amazing contacts with my mobile setup, and it honestly does far beyond what I ever expected.

I've never had a base station, but my half-wave antenna will be here tomorrow, and I'm curious how it will compare to my mobile.

My biggest issue is going to be height. I can run an 18ft mast, no problem. I tried 30ft without the antenna and it looks pretty sketchy without guy lines.

Hopefully, I'll be able to report back in a couple days.

 

[Backwoods40]

Ideal heights are placing the high current part of the antenna at 1/2 wavelength points above the ground

I know "height is might", but one thing I've never seen answered is what type of difference you would see between a 32ft, 36ft, and 40ft mount point.

Would the 36ft work better than a 40ft since it's a full wavelength instead of 1.1 wavelength, or is higher always better?

 

[prcguy]

That is subjective. Everyones setup is different, and some work better than others. I’ve now tried 2 “real” base antennas over the years (Antron 99 and just recently a Sirio GPS27) and both suck compared to smaller “mobile” antennas. Why you ask? Noise floor. Both base antennas had no ears because of a constant S3-S5 noise floor. I couldn’t hear my locals 40-60 miles away. My 102” whip mounted on an 8 foot pole behind my garage has an S1 noise floor, and the 4.5 foot Tram 717 on a mag mount that i'm now using on the house (attached to metal roof fascia) also has an S1 noise floor. Both have an SWR of 1.0-1.1 across the band. I can talk on SSB locally to guys 60 miles away with both of those antennas, or roughly 25 miles on AM. No issue shooting skip either.

As i said, everybody has different success stories. That’s mine. 3 different houses, 2 different base antennas, and at one point even bought a 40 foot tower, and same issue. No "weak station” ears. I always resort back to the 102” whip as it beats the base antennas for long distance local communications all day long.

I would like to hear from others with the same experience above. I'm betting this is an extreme situation and there is probably a good explanation why a mobile antenna seems to be outperforming a couple of known and larger base antennas. Noise of various levels is always there and general reductions noise between two antennas mounted in the same place usually means less gain therefore less range. I would also like to know the differences in transmitting between the mobile antennas and the base antennas among other things. If the transmit signal level at a distance is higher on the mobile antenna vs the larger base antennas something needs to be explained.

 

[prcguy]

I know "height is might", but one thing I've never seen answered is what type of difference you would see between a 32ft, 36ft, and 40ft mount point.

Would the 36ft work better than a 40ft since it's a full wavelength instead of 1.1 wavelength, or is higher always better?

Antenna height in 1/2 wavelength increments is the magic number and the more the better. Antenna radiation is greatly affected by the ground or earth below it, the pattern gets pushed upwards at varying angles depending on the height above earth. Take a horizontal Yagi, a 3 to 5 element for example, its advertised "free space" calculated gain lobe will extend straight out from the Yagi generally equal on both sides of the Yagi. Place that same Yagi 1/4 wavelength above ground (9ft for CB) and its radiation pattern will be skewed upwards maybe 10 degrees maybe more and signal at the horizon will be decreased noticeably.

Raise that same Yagi to 1/2 wavelength above ground (18ft for CB) and the pattern will be pulled down some. It will still be skewed upwards but the first 1/2 wavelength above ground will pull it down some and the second 1/2 wave or 1 full wavelength above ground will pull it down a little more and if you can get it up 10-20 wavelengths in exact 1/2 wave increments it will be nearly what the free space radiation pattern is at straight out the front of the antenna. The odd multiple of 1/4 wavelengths above ground will be the points where the pattern is skewed upwards more and that diminishes as you get many wavelengths above ground like 10, 20 or more wavelengths.

The same happens with a vertical antenna like a ground plane or 5/8 or whatever. Put a 1/4 wave ground plane at 9ft off the ground and its going to point upwards some reducing the signals at the horizon. Put that same ground plane at 18ft and the pattern will pull down a little and people down the street or a mile away or 20mi away at the horizon will see an improvement. Put that same ground plane at 36ft, better still and you also have basic height working for you at the same time getting above potential obstructions like buildings.

With CB being at 27MHz and 1/2 wavelength being about 18ft its not hard to get a CB antenna at a good heigh to maximize signal at the horizon at 36ft up, which is the second 1/2 wavelength point. On lower frequencies like 40m where the first 1/2 wavelength is about 65ft its much harder to get antennas high enough to bring the radiation pattern down at the horizon and the 2nd 1/2 wavelength point on 40m is around 130ft.

 

[K6GBW]

I can’t imagine a situation when a mobile antenna would work better than an A99 or other 1/2 wave or 5/8 wave base antenna. The only explanation would be to intentionally make the radio deaf to deal with noise, but that’s not really the right way to handle it. I run an A99 attached to an Icom IC-7300 and it’s one of the quietest antennas I‘ve ever used. Lately I‘ve used it on 10m to make contacts in Poland, Hungary, Ireland, Alaska and Argentina. So the A99 and similar antenna for sure work well.

 

[WSAC829]

I would also like to know the differences in transmitting between the mobile antennas and the base antennas among other things

According to my buddy 30 miles north of me, no noticeable change in received signal on his end. On LSB with the Sirio i was giving him 3-5 s-units, and i still give him the same with both mobile antennas. Radios used are a Radioddity QT40 (garage) and a Retevis HS4 (house). Both radios do about 40 watts.

I can’t imagine a situation when a mobile antenna would work better than an A99 or other 1/2 wave or 5/8 wave base antenna. The only explanation would be to intentionally make the radio deaf to deal with noise

Quite the opposite. The mobile antennas make my radio “un-deaf” due to their lower noise floor. I can hear weak (distant) local stations on the mobile antennas that i can't hear on the base antennas. Thus it means i can also talk to them since i know they are out there to talk to. Cant talk to people if you cant hear them to begin with right? Again, skip is NOT a problem. I’ve talked all over the world on mobile antennas used as base antennas. For the last 20 years i had been using a little wil mag mount on a metal garage roof. It finally gave up the ghost after 2 decades of abuse.

Again, in 35 years of using radios, this is MY personal experience. You guys don't have to agree. I know what works for ME, and base antennas aren’t it. Doesn’t matter my location, height, coax, ground, etc. I’ve tried it all and wasted loads of money trying to knock out the base antenna noise floor issues with no success.

Here is a video where a guy compares a 102 vs an A99. Notice the RX is damn near identical, but pay attention to the noise floor when he switches back and forth between key ups. The A99 has a S3 noise floor, the 102 has a S2 noise floor. For me that difference is huge since all my locals are 30+ miles away from me and get buried in a S3-S5 noise floor..

 

[WSAC829]

Here’s my current noise floor on the Tram 717. How a good antenna should be at night after skip is gone.

 

[prcguy]

Here’s my current noise floor on the Tram 717. How a good antenna should be at night after skip is gone.
View attachment 170981

If you lived closer I would like to drop by with some of my stuff and do some measurements. I think when I was done you would be a believer in base antennas again.

 

[WSAC829]

I don't need to believe. These are real world results, and that youtube video proves my point. So does this one….

Jump to 5:40 to see his noise level. Next to nothing, like it should be.

 

[niceguy71]

this is what I did... I may have everything wrong???? but I think it came out great and works fantastic..... been just over a year so I can give you prices for everything.

 

[prcguy]

I don't need to believe. These are real world results, and that youtube video proves my point. So does this one….

Jump to 5:40 to see his noise level. Next to nothing, like it should be.

In the video it looks like the guy went from one home made antenna, the PVC pipe job to a vertical dipole then he says the home made ground plane with just 2 radials talks better to horizontal antennas around town and it sounds like he has many friends running horizontal. And ithat particular ground plane with just two radials t probably would work better to horizontal antennas compared to the purely vertical dipole.

Most man made noise is vertically polarized and if you go horizontal there is usually a noticeable reduction in noise. But antennas can't discriminate between signal and noise because noise is RF energy at the same frequency the signals are on, so a reduction of noise on your S meter is usually a reduction of antenna gain, or a change to horizontal polarity with less noise pickup.

Bottom line for me is the video shows nothing concrete about antenna performance, that needs specific tests and specific A/B comparisons between antennas and test equipment to identify and verify any changes. I've lost count of the times over the last 40+yrs where someone has a fantastic claim about an antenna and with careful testing and finding problems in their setup I was able to prove that basic antenna principals prevail and the fantastic claims were due to something wrong in the setup or with the previous antenna they were using.

 

[WSAC829]

Preach all you want. My current setup works for my needs, and that's local long distance. Something 2 brand new base antennas couldn't do.

So by your theory, my reduction of noise floor = less gain. Yet i can hear stations 30+ miles away with “less gain” that i cant with more gain on the base antennas. Sure, makes sense. Not. Try again.

To make things clear, the Sirio and the Antron worked fine. Good SWR, etc. Good receive on strong / medium stations. They just sucked on picking out “weak or distant” stations do to their horrid noise floor. No good antenna should have S3-S5 or higher noise floor. That just makes them “deaf”.

 

[prcguy]

Preach all you want. My current setup works for my needs, and that's local long distance. Something 2 brand new base antennas couldn't do.

So by your theory, my reduction of noise floor = less gain. Yet i can hear stations 30+ miles away with “less gain” that i cant with more gain on the base antennas. Sure, makes sense. Not. Try again.

To make things clear, the Sirio and the Antron worked fine. Good SWR, etc. Good receive on strong / medium stations. They just sucked on picking out “weak or distant” stations do to their horrid noise floor. No good antenna should have S3-S5 or higher noise floor. That just makes them “deaf”.

I mentioned before an antenna can't discriminate between noise on frequency and an actual CB signal on frequency. You might have RFI issues that are changing with the setup like RFI induced onto the coax in the house and it travels up to the antenna. Using metal siding on a building and/or a metal roof for a ground plane is a completely different scenario compared to an isolated antenna up on a mast with respect to noise.

Could be the other antennas worked better but were masked with noise and if the noise issue is resolved the other antennas might work better than what you have now. As I mentioned before it takes methodical testing to rule out everything and sometimes the end result is not what you expected. I used to get flown all over the world at $2.5k/day billing rate to diagnose and fix impossible problems and I don't remember ever failing to deliver, usually surprising customers.

 

[WSAC829]

Again, this was tested over the years at 3 different houses, multiple mounting locations, 3 different types of coax, 40 foot tower w/20 feet of mast, etc. All same results. The 102” whip worked best in every situation. Now as for the metal roof ground plane, i agree. My house is 4000 sq foot and garage is 2500 sq foot. HUGE ground planes that are to my advantage when it comes to magnet mounts, and the Tram 717 is supposed to have a 6db gain. However the 102" whip is on a 102” metal pole behind the garage. Before that it was attached to a chimney mount at my old house which replaced the 40 foot tower and A99 because it outperformed it.

Not arguing your job/knowledge, but when it comes to radio equipment and setups, it’s never a “one size fits all” scenario. Everyone knows that. It’s no different than power mics. Some work great on certain radios, but will squeal like a pig on others. Just because it works for some doesn’t mean it’ll work for others.

At any rate, i’m happy with what i’m using. Can talk local long distance once again, and still shoot skip around the world. Isn’t that what radio is all about? Like @slowmover always says… hear and be heard.

 

[prcguy]

Again, this was tested over the years at 3 different houses, multiple mounting locations, 3 different types of coax, 40 foot tower w/20 feet of mast, etc. All same results. The 102” whip worked best in every situation. Now as for the metal roof ground plane, i agree. My house is 4000 sq foot and garage is 2500 sq foot. HUGE ground planes that are to my advantage when it comes to magnet mounts, and the Tram 717 is supposed to have a 6db gain. However the 102" whip is on a 102” metal pole behind the garage. Before that it was attached to a chimney mount at my old house which replaced the 40 foot tower and A99 because it outperformed it.

Not arguing your job/knowledge, but when it comes to radio equipment and setups, it’s never a “one size fits all” scenario. Everyone knows that. It’s no different than power mics. Some work great on certain radios, but will squeal like a pig on others. Just because it works for some doesn’t mean it’ll work for others.

At any rate, i’m happy with what i’m using. Can talk local long distance once again, and still shoot skip around the world. Isn’t that what radio is all about? Like @slowmover always says… hear and be heard.

The Tram 717 has less gain than a dipole and probably on the order of -2 to -5dB depending on ground plane, that can be proved in many ways. A 102" whip over a perfect ground plane has a little bit less gain than a 1/2 wave dipole, around a dB or so less. This will all show up when transmitting to test equipment that can accurately measure the differences. Reception is governed by signal to noise ratio and noise/RFI will affect that separate from antenna gain and pattern.

I get very curious when I hear radio and antenna things don't follow rules and I love to research why. Unfortunately for me its too far away to research but probably better for you.

 

[WSAC829]

I get very curious when I hear radio and antenna things don't follow rules

Rules are meant to be broken.

 

[niceguy71]

That is subjective. Everyones setup is different, and some work better than others. I’ve now tried 2 “real” base antennas over the years (Antron 99 and just recently a Sirio GPS27) and both suck compared to smaller “mobile” antennas. Why you ask? Noise floor. Both base antennas had no ears because of a constant S3-S5 noise floor. I couldn’t hear my locals 40-60 miles away. My 102” whip mounted on an 8 foot pole behind my garage has an S1 noise floor, and the 4.5 foot Tram 717 on a mag mount that i'm now using on the house (attached to metal roof fascia) also has an S1 noise floor. Both have an SWR of 1.0-1.1 across the band. I can talk on SSB locally to guys 60 miles away with both of those antennas, or roughly 25 miles on AM. No issue shooting skip either.

As i said, everybody has different success stories. That’s mine. 3 different houses, 2 different base antennas, and at one point even bought a 40 foot tower, and same issue. No "weak station” ears. I always resort back to the 102” whip as it beats the base antennas for long distance local communications all day long.

I think the Base Station antenna's are getting a lot of noise because they pick up more than the mobile antennas... if you turn your RF Gain down till you get a S1 it would work like your mobile antenna... but I honestly think the base antenna's are just picking up that much more signals.