The Mysteries of Antennas             

Never a dull moment when you play with those skyhooks.   



I have been recently enjoying a resurgence in CB radio fun. The last several months of this year have seen quite a bit of time spent restoring classic old radios from back in the "golden days" of CB radio, along with many hours of on-air fun.  I was not expecting this level of interest when I first moved in, so consequently I only put up a very modest antenna, a 102" whip on my second floor rain gutter.  This was the ultimate throwback antenna, as I had started out with my very first 23 channel rig connected to a similar antenna setup back in 1974.  That setup didn't work all that well then, but because of my current home's altitude, that throwback antenna actually performed rather well.  But human nature being what it is I, like most people, are never satisfied at any one signal level for too long and, consequently, I started looking for antenna performance enhancements.  Fueling this desire was the fact that my fellow classic radio enthusiasts were at least 10 air miles from me (One guy is 20 miles away), and our respective signals were not all that great and I wanted to improve my standing in the signal department.  The easy solution would be to just put up my old crank-up tower with some sort of monster beam on it, or a high quality ground plane.  But complicating the issue was the deed restriction imposed on my development by the builder, which prohibits antennas attached to the house from extending above the roofline (And being visible from the front).  Because of this, I was forced to become more "creative" and "stealthy".  My first antenna improvement experiment was the Gutter Beam.  Adding the reflector element to the 102" whip improved my signal about 4 - 6db to some people, but also seemed to have a much greater signal improvement to others in the lower elevations in the neighboring town of Pottstown.  It also knocked down interference from the west, and seemed to reject a great deal of skip noise as well.  This modest signal improvement was expected and welcome, but I was still not strong enough to overcome the frequent jammers who seemed to have a problem with us old time CB operators, who were relative newcomers to this particular group.  But other than a full sized CB antenna, I didn't think I could do much better than what I was doing currently, although I had given some thought about adding a director element and making the Gutter Beam into a 3 element.  I didn't think it would add much more in signal, so I was not all that motivated to do it.  I also figured that my enhancement to the 102" whip pretty much made it equivalent to a 1/2 wave "stick" antenna (at least to the east), so there was probably not all that much more I could do in the antenna department to improve my signal.  But then one day, I was returning from an outing in my mobile and while I was sitting in my driveway, I managed to catch one of my friends on and, on a lark, did some signal comparisons.  I now came to find out that my mobile (Also equipped with a 102" whip and running equal power) sent him a stronger signal (by at least 1 or 2 "S" units) than my base did.  I thought that strange since the Gutter Beam was 20' higher in elevation plus had that reflector element for added gain, so it should've had the stronger signal potential.  But the meters don't lie (At least not relatively), so that got me thinking about the likelihood that there might still be some more signal potential hiding in my setup.  I just had to find it.

Back in the old days, most of my CB associates and I were pretty much one dimensional in our thinking when it came to antennas.  Bigger was better, higher was better, and closer was better. We believed that if one omni-directional antenna put out a better signal to one or two people over another antenna design, that it should put out a better signal to everyone else, no matter where they were. Also, we believed that the higher up your antenna was, the further out your signal would carry unconditionally.  And lastly, assuming equal power levels, the guy who was the closest would transmit the stronger signal.   Naturally, any experienced radio guy who's been around a while would debate those blanket assumptions.  Experience tells us that antenna radiation has many more variables than constants and that there is very little that is set in stone.  Unless we happen to live in a totally flat area, with consistent soil resistance and few obstacles (trees, buildings etc.), terrain will have a very influential affect on which antenna setup will work best in a particular direction.  Most of us did not have the ability, back then, to do a real time A/B comparisons between our old antenna and the new one, or lower height vs. higher, with every person on the channel to map the results.  We also did not fully understand the phenomena of radiation angle, multi-path cancellations, and changes in signal polarity, and how a particular antenna design and mounting height could affect each of them. 

Now back to my current signal improvement quest.  I don't want to make it sound like I knew exactly what I was doing here, because the unknown variables are just that, but it was clear that I needed to try something.  So I decided to try an experiment on a whim.  I had been toying with the idea of placing some sort of full-sized antenna on the back of my detached garage roof in spite of my deed restrictions.  For one thing, 7 years had gone by and the builder has long gone.  A home owner's association was never formed and therefore there is no one tasked with the authority to enforce the restrictions.  Secondly, I think I may have a loophole in that the restrictions make reference to the house itself, but do not address large external buildings (Of which I am the only one in the neighborhood to have). Lastly, the back of my garage is nestled within a somewhat wooded area, and a simple stick antenna would blend in with the trees to some extent.  With these little tidbits of information in mind, I made tentative plans to "do something" sometime next year when the weather improved. All I needed to do was figure out what antenna I wanted to use. The least obtrusive would be to put up one of those "stick"-style fiberglass antennas.  I've never been a big fan of those and I didn't know how well one would work.  Because of the interference issues, I also preferred something directional.  But even a 3 element beam would be a bit too obvious.  I also still had my old Avanti Sigma 4 vertical from my old location.  This antenna doesn't have any radials, but is a whopping 27' tall and would actually hit at least one branch if I mounted it on the back of the garage roof.   I also have to pick up a 25' extension ladder to get up on the roof, which is probably my biggest hurdle, as I'm getting increasingly leery of climbing ladders the older I get.  But those were my choices, and I had 5 or 6 months of impending winter weather to make a decision.

But then one day when the late fall weather took a brief turn for the warmer, I decided, totally out of the blue, to see what would happen if I put the Sigma 4 up on a short pole behind the garage.  I had briefly put up that antenna before during my first winter in my new home.  But I had to take it down when they graded and seeded my yard the next spring.  During that time, I didn't really get a chance to compare its performance relative to the original 102" whip.  This time, the antenna was attached to about 6 feet of mast and I ran about 100' of coax cable from the back of the yard up to my radio sanctum.  A quick check of SWR showed about a 1.8:1 match.  Not as low as it once was, but acceptable for now.  But the big test would come that night.  Would this bigger, but altitude challenged, antenna beat out my current antenna system? And if so, by how much?  Well the answer was somewhat surprising. To my fellow classic radio compadres, my signal jumped up a whopping 10db, and made the difference between a marginally noisy signal and a full quieting one.  I was overjoyed to say the least, considering that when I put it on the roof, it will gain an additional 15' of height, which SHOULD translate to an even greater signal right?  But wait! Things were not quite so straightforward, as I found out over the next few days, as those ubiquitous and unpredictable variables manifested themselves.  As part of the fact finding test, I put both of my antenna systems on a switch box so I would be able to switch back and forth between them for a quick A/B signal comparison.  What I found was interesting. The Sigma 4 was not always the better signal producer. To the people farther out and on higher ground, the Sigma 4 antenna showed a significantly better signal.  But to those in the altitude challenged parts of Pottstown, the Gutter Beam was noticeably better.  Huh? How can this be? The Sigma clearly had more gain in a few different directions, so why not to every place?  Note that I'm only comparing signals in the same general direction in which the Gutter Beam is pointed to.  I would expect it to fail miserably in the opposite and side null directions.  Well, enter in the affects of terrain and the radiation angle of the antenna.   It would seem that in just about every case where the Sigma outperformed the Gutter Beam, those stations were at equal or better height to my location. That leads me to theorize that my Gutter Beam has a lower radiation angle, which better fills in those low areas in the center of town. This theory was further supported when some E-layer DX started running one night last week.  The Gutter Beam rejects quite a lot of skip while the Sigma seems to be a skip magnet.  I had stations in Ohio and Indiana calling me out of the blue just to let me know that my ground mounted antenna was working.  There were some other ancillary benefits which I noticed when running the Sigma 4 as well.  For one thing, placing the antenna 100' farther away from my radio room (The Gutter Beam was directly overhead), has resulted in much less R.F. energy bouncing around in my shack. With the Gutter Beam, the near field R.F. was so strong that monitor radios would have their "S" meters pegged without even having an antenna attached.  One of my power supplies would also fluctuate with the R.F. present.  I also had trouble with microphone R.F. feedback, as well as the inability to operate my stereo while transmitting.   There was even occasional interference caused to my VHF Ham rigs (especially 6 meters).  All of these problems have been either reduced or eliminated by running the Sigma.  The extra antenna distance has also reduced the interference I receive from my wireless router and computers.  It would seem that even at a barely above ground level mounting, the Sigma has improved the whole experience for me.

Antenna theory pretty much says that a ground mounted vertical will have a relatively high angle of radiation without a counterpoise of ground radials.  You can also lower the angle of radiation by raising the antenna to over 1/2 wavelength in height above the ground.  I've always believed that the design of the Sigma 4 promoted a higher radiation angle than that of a conventional 5/8th wave ground plane.  When I lived in an altitude challenged area, that higher radiation angle helped my signal to climb out of the hole, which is why I felt that the Sigma was my best performing omni antenna.  But now, the question before me is;  "Now what"? Will raising the antenna further increase my signal potential to my more distant friends, or will lowering the radiation angle cancel the gains I already have? The weather is promising to hold on the warm side, and I'm planning to correct the SWR and may try another experiment or two to see what happens.  Well, the next weekend came and I raised the antenna up to about 9' in height, and dropped the SWR to around 1.6:1.  So far it would appear that those very minor changes have not resulted in any really noticeable further gains in signal.  I also guyed the mast to protect against the unrelenting winter windstorms which blow through my area on practically a weekly basis.  I'll probably leave the antenna as it is now until spring where (hopefully) I'll finally put it on the garage roof.  Something will have to happen in any case, as once the grass starts growing again, my feedline will become a target for the sharp, unforgiving blades of my lawn mower.

As frustrating as this kind of trial by experimentation might be, this is one of the most interesting and fun aspects of radio.  The unpredictable nature of it adds to the mystique of the hobby.  There is no hard, fast, one-size-fits-all solution to signal propagation.  This is why many H.F. hams have several different antennas, of different configurations, for the various bands.  They know that each different antenna type works better for specific types of conditions.  

But as they say, ignorance is bliss. As a teenaged kid in the 70's cutting his teeth in radio, it was much easier to deal with these issues from a one-dimensional perspective. Trying to factor in all the variables would have driven me crazy, especially considering my anemic cash flow situation at the time. That's why rediscovering the good old days in CB have been so much fun.  I'm much better able to make sense of it all now.  Who would-a thunk it?

Update: My antenna system has continued to evolve. A trade opportunity presented itself and I found myself the proud owner of a 3 element beam. The beam was soon mounted to the back side of the garage, where it barely cleared the overhanging tree branches. The signal potential increased again by about 5 or 6 db and the rejection from the back side of the antenna was just what the doctor ordered for nulling out jammers who mostly come from the opposite direction.  Checking signal with my friend Art, when he had his remote receiver running on the internet, revealed that from 20 miles away, my gutter antenna is barely readable, while the beam is a full S7.  Once again I learned that it's all relative, and at the end of the day, a real antenna will still outperform a makeshift one, everything else being equal.  But it's still fun to experiment.