'Directional' antenna for Part-15 ??

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'Directional' antenna for Part-15 ??

Has anyone designed or know of an existing 'directional' antenna array, adaptable to the Hamilton transmitter?  I am positioned in a place where my designated service area is in a certain and specific direction, as opposed to a dense forest behind me. Unless I have a measurable audience among the wildlife, it would be beneficial to concentrate my signal toward an actual population of people... in a floodlight-like pattern, if possible. Of course, any such antenna must fall within the legal-length measurement.  I guess a 'beam' antenna, like those used by HAMS, might be an area to explore.

I think you'll find beams way

I think you'll find beams way too big at the frequencies we're talking about.

A dipole is somewhat directional, but you'll only get 1.5 meters on each side, and I'm not sure that would tune (or be even remotely efficient if you could tune it).

I suspect that a ground-mounted 3 meter vertical antenna with a great ground (including radials) would still outperform any directional antenna you might come up with.

Beam thoughts

Just kinda shooting from the hip here as we're heading out the door pretty soon... but...

This beam idea might not be to crazy for this type of situation.

After all, the verticals we use now are technically much to short, yet the transitters are tuned to work into them.  Who is to say that a beam that is also much to small wouldn't work equally well?

Further, and again -- just quick thinking -- a beam antenna only has one actual driven element. basically a dipole.  The other elements -- the one behind it a reflector, and the directors in front that "focus" or concentrate the signal in a given direction, are parasitic e.g. not connected to the feedline, and wouldn't count as part of the antenna. 

I would think someone who could do some antenna computing could figure out a beam based on the shrunken vertical size we're allowed, and come up with element size and spacing for a beam.

I would expect that as long as the driven elements are of legal length (let assume 1.5 meters per side of the boom) the antenna would be legal as the reflector and directors are not connected to the feedline -- they are parasitic elements.

I do think there may be some useful experimentation to be done. 



An Unproven Idea

I suspect that by putting all your radials on the side toward the desired target the radiated signal from a vertical antenna will put all its strength in the direction the rials are pointing.

Carl Blare

i was thinking same thing

i was thinking same thing carl just posted. but we arent supposed to have ground radials.

2 cents

Won't help because your using line of sight, not skywave just pure ground wave, just simple point to point antenna height to antenna height and free space and a receiver turned your direction and one that is free of AC hum and noise will hear you.  Get that antenna up in the air and let mother nature's line of the geographic site do the rest, keep it away from things that will absorb your signal and waste burning up what little rf the fcc bestows on us, lucky fellows as we are in the 100 milliwatt class 


AM 1680 KOIW Old Time

heres a gent who discovered its all about height not radials


AM 1680 KOIW Old Time

examples of height makes might


AM 1680 KOIW Old Time

example of am radio transmitter antenna

here is wbt am radios antenna system notice they are tall and fat and hey are far away from anything that would absorb or reflect their energy but a lot of us use tripods or mount our antennas on houses and what's happening is the little wattage we have is being wasted heating a roof or a tree or worse the ground...



AM 1680 KOIW Old Time

fact discovered that elevation is the key not radials

Published on May 12, 2015

Hamilton Rangemaster AM1000 for sale near Indianapolis on 1610. I can ship (at buyer's expense) the transmitter, brackets, cable, power supply and antenna base (2-3 feet) but not the upper part of the antenna (a CB whip) but would highly prefer that the buyer come here and hear it in action and witness the great coverage first hand to avoid misunderstanding. Mounting it on the ground, even with a good ground, will not perform as well as being on the roof at 20' with no ground. FCC approved as long as you use it exactly as it is. The audio of this video was recorded from an AM receiver about 15' from the transmitter. It is possible to tell what song is playing nearly 6 miles away but understand that your results may vary--that it why I would prefer that the buyer witness it's capabilities first hand before buying.

  • another argument for Line of sight again as the chief friend in the fight to be heard long and far :)


AM 1680 KOIW Old Time

The Truth About Ground Radials

Radioham posted:  "but we arent supposed to have ground radials."

I am happy to say that you are mistaken.

There is no restriction in the part 15 rules about ground radials.

Perhaps you're thinking of "ground-leads" that make your total antenna measurement more than 3-meters?

All part 15 stations that have the real-estate to do so tend to have ground radials.

Carl Blare

And herein lies the umpteen

And herein lies the umpteen kazillion discussion of ground leads, radials, etc.

The basic problem with all of this is that all we have are a few, simple words on a piece of paper (at least back when it originated) that tells us what kind of antenna system is compliant with Part 15.

These words are open to interpretation, and, in fact, have been interpreted differently throughout the years, both by practitioners and FCC inspectors alike.

Are radials allowed?  The rules don't say anything explicitly.  It's been stated (not by the FCC) that you're not allowed long ground leads, as they radiate, but again, that's not explicitly in the rules either.

Are capacitance hats allowed?  Not in the rules.  And again, differing opinions and potentially differing rulings from FCC inspectors.

So when someone says that, because the directors & reflectors of a beam antenna are not physically connected to the driven element, they are allowed, forgive me if I take this with a grain of salt.  They ARE part of the antenna system, and thus, according to the words in the rules, need to be at most 3 meters in length total (including matching element, feedline, etc.).  Others may disagree with me, but the fact that people are disagreeing leads us into yet another Part 15 gray area.

Bottom line - it will take an FCC inspector to determine whether ANY antenna system or installation is compliant.  All an operator can do is to infer the intent of the rules and do their best.

First off the audio on that

First off the audio on that Rangemaster is awesome. The coverage to really has me scratching my head on that one. Wish I had the land for a mass to actually try something like that because 6 miles is what I would really love to come.  And surprise of all surprises no rules had to be broken to get that type of range. I know pirates on FM that would really love to have that type of range. I have a good idea to see what we can do about trying something like that on AM.Well first I'd have to save $500 and that is just for the TX.

Progressive Rock (Album Rock, Deep Tracks), Classic Rock

More Power for Hobby Broadcasters

I didn't get nearly that

I didn't get nearly that supposed 6 mile range on my Rangemaster.

Not on my ground-mounted one over soil that was highly conductive, or mounted high.

I got 1-2 miles on the ground mounted install, much less up high.

I suspect that something is acting as a long ground lead on that transmitter.  The physics and math predict under 2 miles with a great (legal) installation.

How many choose ground-mounting?

Hmmm ... has ground-mounting become the trend? I'm curious, how many are engaged in this type of installation... and does it result in better transmitter performance (compared to elevated installs) ... or is the motivation driven by compliance, perceived or otherwise?

Beaming it your way

Why not build the classic 3 meter base loaded antenna with ground radials the side where you want the signal to point most of the energy, then measure out spacing from the middle the same length of the driven element? Put a slightly larger element behind the driven element at 3 meters, place another element in front of the driven element which is slightly shorter than the last two elements.

The only part of the antenna that would be energized is the middle element, the other elements would be a director and reflector.

The front non driven element would be the director, the rear non driven element would be the reflector. Those two added elements while technically not part of the transmitting antenna, should work much like a beam antenna. It would take some patience to set this system up , but i don't see why it wouldn't work.

What i don't know is the exact spacing needed to make the added vertical elements work with the powered element.  All beam antennas use a dipole as the driven element with hot on one side, ground on the other. In this case the earth is the ground side of the system.

Both the reflector and directors need to be isolated from Earth ground but spaced far enough apart to become effective, that's where patience comes in to play. Spacing makes or breaks a good beam system.

 Barry of 1200 AM BBR - WQYY 664

Ground Mounting Has Always Been the Trend.

Take a look at ANY commercial AM station antenna.

Druid Hills Radio AM-1710- Dade City, FL. Unlicensed operation authorized by the Part 15 Department of the FCC and our Resident Hobby Agent.  

Ground Mounting Has Always Been the Trend.

touche :-)



Druid Hills Radio AM-1710- Dade City, FL. Unlicensed operation authorized by the Part 15 Department of the FCC and our Resident Hobby Agent.  

guys guys guys

we are fooling ourselves into thinking your getting a foot out of anything other than line of sight because your not using skywave your not propagating a couple hundred miles you're not basking in a nvis straight up and down 25 mile coverage here we are line of sight depending on what's in your way and what's not in your way and reading all the results of what most are getting anyway 1-2 miles at most I would add take your transmitters up a tall tree and see how much farther you get it should surprise you esp your using a pro-caster or Rangemaster they are best things going basically mediumwave walkie talkie transmitters..




AM 1680 KOIW Old Time

Ground wave and Line of Sight Propagation

I just realized that I've been a member of this site since 2010, but don't think I have ever posted. I read the mail from time to time, but don't comment. Anyway, after reading the above post by Joe, I felt the urge to say a few things about ground wave and line of sight propagation.

Ground wave propagation happens with signals up to about 2MHz. The electro-magnetic waves from the transmitter induce currents in the earth. As a result, the wave tends to follow the curvature of the earth. Obviously, with the range of a low power Part 15 signal, there won't be a whole lot of curvature, but the fact that the ground is an important part of propagation at this frequency remains.

With line of sight propagation, the wave travels directly between transmitter and receiver in a straight line. The earth is not involved in the mechanics of this type of propagation. It is distinctly different from ground wave propagation.

I don't know a whole lot about propagation, and am learning as I go, but I'd say that Joe is definitely correct about the fact that our low power AM part 15 signals don't reach the ionosphere, which rules out any kind of sky wave propagation or NVIS. Unlike FM Part 15 though, where the only propagation mode is line of sight, our AM signals rely heavily on ground wave propagation for any kind of meaningful range.

Unfortunately, that means we need good connections to ground. Better get pounding those ground rods and/or burying those radials!

PS - sorry I haven't introduced myself, but I probably won't be posting here a whole lot.

Dave Richards

Oakland, California

AM MW Radio is not "LOS." It

AM MW Radio is not "LOS." It follows the earth's curvature during the day and Skywave at night.

Druid Hills Radio AM-1710- Dade City, FL. Unlicensed operation authorized by the Part 15 Department of the FCC and our Resident Hobby Agent.  

Plan-C Anyone?


Okay ... 'Plan-C' is now operational and with astonishing results.  I use the word 'astonishing' because for me, it accomplishes what has always been my primary objective, and that is to serve a small community, group or neighborhood with my legal Part-15 station.Since most seem to be in agreement that outdoor elevated installations could warrant a visit and/or an NOUO from the enforcement bureau .. and since my two attempts at ground-level installs were a disappointment in terms of desired range,  'Plan-C' was simply something I felt compelled to try.My Rangemaster has found a new home ... under shelter.  The transmitter now resides on the inside of a garage .. as the structure provides ample headroom for the 8 ft whip.Some immediate advantages are as follows.1. The transmitter is no longer exposed to the often-harsh outdoor elements of the brutal northeast.2. The cover of the transmitter's enclosure can be permanently removed, exposing the 100 milliwatt LED for anytime compliance monitoring.3. The audio/power cable length has been reduced to a mere 10 inches total ... leaving over 12 inches to spare all-the-while staying well within the 3 meter restriction. 4. And for what it's worth, the unit is less susceptible to a direct lightning strike and potential vandalism. ---------------------------------------------------------------As mentioned in a previous post, my configuration utilizes a wireless STL, meaning there is no direct physical connection between studio and transmitter. This allows for the much shorter (10") feed line ... greatly diminishing the likelihood of any measurable stray and unwanted RF emitting from the cable.The transmitter is now connected directly to the household's service ground... right at the outlet box. This DID effect overall range... but not as much as I have been led to believe. After all, in most cases, the ground lead is connected to a network of buried cold water pipes.On the inside, the 8 ft stainless steel antenna reaches the rooftop. If I can devise a foolproof method for preventing leaks, I might consider protruding the antenna through the ceiling by a few inches it could radiate into open space.  This would require careful planning and might actually offer some improvement.INITIAL PERFORMANCE RESULTS:( Reception In The Car)1. Detectable signal at 3.5 miles.2. Listenable signal at 2 miles.3. Minimal noise floor at 3/4 miles.4. Solid, zero noise floor interference at 1/2 mile.(Indoor Reception)Confirmed by three of my go-to neighbors for whom I can rely upon for an honest reception report.All reported an IMPROVEMENT in the signal, stating it was noise free and solid at distances of 1/4 mile and less.  One individual who claimed her light dimmer switch would often interfere with my signal, indicated that this was no longer an issue.So ... what can be derived from these conclusion?  First... they are inconclusive and need further testing and scrutiny. Factors such as direction of travel, weather and atmospheric conditions, man-made interference (power line congestion etc) along with time of day and time of year are all variables that are subject to change.However, I am impressed and excited by the indoor reception results thus far. It appears indisputably that my effective near-field range has improved.  Ultimately, my goal (stated in paragraph one) is closer to being realized. In this process, I'm trying not to be overly concerned with reception at the fringes... where few are likely to interact with my micro-station anyway....given the countless alternatives at their disposal. Based on the aforementioned observations and for the sake of conversation, I believe it is safe to say that my range in the far-field has been reduced by 15 to 20% .. which should come as no surprise. On the other hand, the near-field range has experienced a dramatic improvement ... for reasons I've yet to fully comprehend.Again, depending on what it is YOU are personally trying to achieve ... Plan-C may or may not be for everyone.


I like to be the first guy onboard to say congrats on an awesomely engineered station, sir! May you serve your community well.

PS I too get the same or a little better radius being outside in the elements so I concur wholeheartedly raising the antenna to 35 ft made me all the difference and no grounding at all..:) God SPEED on your upcoming programming keep us informed Bill!!



AM 1680 KOIW Old Time


There are a lot of cool folks on this forum and i love all the heated stuff we say hey we are all pioneers here




AM 1680 KOIW Old Time

Reaching for the Sky

Responding to Dave Richards comment:  "I'd say that Joe is definitely correct about the fact that our low power AM part 15 signals don't reach the ionosphere, which rules out any kind of sky wave propagation."

That is true based on something I read a couple years ago in either an engineering or amateur radio source:

The minimum power needed to achieve skywave reflections is about 20 Watts.

Carl Blare


So turning an am radio will increase its sensitivity most people forget to tell their audiences to turn their radio for better signal reception. That in mind we have several ways to our user's receivers and as i mentioned line of sight does apply as well as groundwave and reflection/refraction off objects like roads/powerlines/rivers/railroad tracks all are sources of pickup for signals below 2mhz  and lastly good old fashioned straight line propagation which in my opinion is the source of our signals best reception reports ALSO ROADS built with rebar are excellent propagators as well... 

;) Radioham 




AM 1680 KOIW Old Time

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