Antenna Field Test Results Updated

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Antenna Field Test Results Updated

For years now I have been using an indoor antenna for AM transmitting. This antenna is mounted horizontally on the ceiling in my basement with the tx. grounded to a cold water pipe near the base of the antenna. The antenna is resonated with a loading coil. Being indoors and horizontal it is suspected that this is a less than ideal situation to achieve range.

So to test this I did an outdoor antenna test. I laid down 11 10 foot radials and connected the ground of my "high efficiency" transmitter to the center point of the radials. The transmitter was positioned on the ground next to the antenna. As seen in this picture the loading coil and antenna are supported by a high tech insulator (an empty wine bottle). The loading coil is the same one I use indoors and has a trim coil for fine adjustment seen at the bottom.

The three meter high antenna is supported with Kynar rope as seen here: My wife ventured out and when she saw this she said "Oh, you're playing with an antenna.". Nothing surprises her anymore.

I used my current transformer arrangement to tune the antenna to resonance. It appears that being outdoors above the radials adds capacitive reactance compared to the indoor position since it required adding 8 turns to the coil to get resonance. It is almost amazing how sensitive this antenna system is to artifacts nearby. I found that by moving from about three feet away to 8 feet away shifts the phase angle by 45 degrees. It is really a sensitive adjustment.

Having achieved resonance it was time to do a comparative range check based on past experience with the indoor antenna. First with my portable I walked down the street and there was a very marked improvement in the signal strength. I could hear the signal at a distance where it was lost previously.

Now for a drive around test. The results are surprising. From my home to the exit of our neighborhood the signal was about the same on my car radio but making the turn onto a state highway the signal disappeared and there was very strong interference from the high voltage power lines on the poles (within our neighborhood the power lines are underground). With the indoor antenna I could travel down this road for 2 miles and still hear my signal. This wasn't the case now. Perhaps having my antenna indoors coupled a good bit of the RF signal to the power lines and the pole mounted lines were radiating this signal ala carrier current.

I continued and turned onto a street with underground lines and the noise abated and I could hear my signal at a distance where it could not be heard previously away from the overhead power lines. This was about 1 mile away. My criteria for this test is if I could identify the audio as being from my station then I was in range, if not I was out of range. Because it was rush hour I didn't drive further away to find this limit but at this distance of about a mile the signal had noise but it was listenable. The signal stayed listenable as I approached my home being heard as I entered my neighborhood by the back door route where previously I couldn't hear the signal.

Then I drove the other direction along the state route and again the line noise blocked the signal. About a mile away in this opposite direction I turned into a neighborhood with underground power lines and my signal was again listenable.

It seems that the range is much improved as I heard a listenable signal at distances and in areas where it was not heard with the indoor antenna but the antenna effect from the overhead power lines experienced with my indoor antenna is gone.

The conclusion from this is that an AM transmitter delivering 86 mW into a base loaded antenna over ground mounted radials can be listenable on a car radio out to at least 1 mile.

I haven't decided whether to go back to the indoor antenna or make the outdoor antenna permanent. This indoor antenna needs not be weather, people, deer, falling limbs, and other mayhem resistant but it is not the optimum for getting a signal out.


Good Test

I can understand why it is tempting to have that outdoor setup, and I have some ideas on resolving the "what to do" dilemma, which I'll get to in a minute.

The wine bottle makes a fine insulator, and appears to be filled with water for ballast. Is there any way the water is influencing the RF field?

I didn't notice a ground rod for that extra type of ground connection, do you think that would affect performance if added?

To help with the decision of where to install things in the future, I would ask what is your objective with the station. If the indoor setup filled your needs, keep that for its convenience.

Another option that would appeal to me would be to have two systems, one in and one out. You could use the outdoor as your nighttime signal.

Carl Blare

That Ain't No Ripple Bottle..

Great job, Neil! I wish I had more time to play again. I sure do miss it..

The Mighty "T.H.C." Tunnel Hill Control.

Radiating Wild Animals with R.F. for Years!

More Likely

"Perhaps having my antenna indoors coupled a good bit of the RF signal to the power lines and the pole mounted lines were radiating this signal ala carrier current."

Highly unlikely. It is more likely that your range was doing good on the indoor setup due to the fact you were grounded to a cold water pipe, which that cold water pipe is connected to a huge array of cold water pipes ran all over the place, down every street, in every neighborhood, and yes even along the state highway in the area where you observed the signal before.


What kind of transmitter are you using?

I'm curious as to what kind of transmitter you are using. You mentioned it's high efficiency.

I also think your range is very good considering the transmitter is at ground level. I know this sounds stupid, but I thought the antenna and transmitter would have to be on a 10 or 20 foot tall mast in order to reach over a mile. I always thought an on the ground setup wouldn't even reach the neighbors.

It's amazing what 100mW will do!

Channel X 1610AM
"The Radio Revolution"
Coming soon to Eastern Cincinnati (If I can ever get a transmitter)

Alright Neil! And a note to ChannelX1610

I'm so glad you brought the
set-up outside. It's a real
adventure to do an outside
set-up. I think it's exciting
to drive around and see where
it goes.

The nulls and peaks and such
can really be puzzling. But it's
very interesting.

Also, I'm sure we all appreciate
the photographs. They look
really good!

To ChannelX1610, Neil built the
transmitter himself.

If you go to the thread that says:

Radio8Z Part 15 Transmitter Design

You can read about it.

Bruce, DRS2


Neil, What Kind Of Portable Radio Are You Using?

Just curious. (I hope you're not
dragging the SuperPro around in
a wagon with a big long extension

Some portables are a lot more
sensitive than others.

Bruce, DRS2



The wine bottle was soaked in hot water to remove the labels just before the photo so there was a little water left inside. Water is death to RF in this instance because the dielectric constant is 83 (if my memory serves).

There was no ground stake used and I don't think it would make much if any difference. The ground stake is primarily for lightning protection.

For Channel X, the transmitter used is one I designed and built and it is in the gray box at the antenna base. The details are at these links:

It is just recently that transmitters with claimed high efficiency have become available. As far as I know this one is the only one where the power output has been documented and reported and it delivers 86 mW into the antenna shown in this project. I am not saying that there are not other high efficiency units out there but I know of none with documentation of the output power into an antenna.

I regret that a more complete and better documented test could not be done but this is a start. Maybe as time and energy permits I will spend some more time on this.

Bruce, I used a GE el cheapo $15 portable with moderate sensitivity for the walk up the street test. For the drive I used the stock radio in my Armada. It seems not to have the sensitivity of car radios I had 20 or 30 years ago but it is adequate. As an example, with my previous truck I could hear WLW during the daytime in Bay City Michigan but with the Armada radio WLW fades away around Ann Arbor.


I feel so dumb now lol

The thread was right in front of me! I can't believe that I missed it!

But anyway...

I wish I knew how to build from a kit. I bet it would be cheaper than buying a transmitter already assembled. And his transmitter seems pretty powerful. 80 some odd percent efficiency? Isn't that better than the procaster? It might even be better than the rangemaster.

I would love to see a side by side between his unit and the SSTRAN AMT5000.

Channel X 1610AM
"The Radio Revolution"
Coming soon to Eastern Cincinnati (If I can ever get a transmitter)

Would Like to Know

And his transmitter seems pretty powerful. 80 some odd percent efficiency? Isn't that better than the procaster? It might even be better than the rangemaster.

I would like to know this but I know of no published data by which to make a comparison.


Me Too

I would love to see a side by side between his unit and the SSTRAN AMT5000.

I suspect that the two transmitters using the same antenna and radials would have almost the same range. The big difference is that with the AMT-5000 the loading coil is internal and none is needed at the antenna.


Cold Water Pipe Ground


I tend to agree about the coupling to the power lines since the drop transformer is set in my neighbor's front yard and it serves only his house and mine. This would likely block the signal.

The water line from the street is black plastic and if there is a messenger wire buried with it this doesn't enter the house. Are you saying that the RF could be going through the water in the pipes?

What about the CATV and the telephone lines? The cable runs within a couple of feet of the antenna in my basement and the phone line stops at the network bridge adapter on the outside wall. They both share the same electrical ground with the cold water pipes indoors.


A Possibility

"Are you saying that the RF could be going through the water in the pipes?"

Could be. Are you familiar with the water antenna? They are antennas that use a stream of water shot out of a spout mounted above an inductive coupling coil. Just like a metal conductor's length determines the resonant frequency, the length of the stream of water determines the resonant frequency. They have been proven to work very well even at HF frequencies.

Since the pipe is non-conductive from the street to the house, that would allow any signal riding on that water in the pipe to radiate, perhaps even couple to other conductive objects the electrical conduit pipe underground, which would carry your signal onto other objects that could inductively carry the signal even further.

Another possibility is the messenger wire, or the pipe itself may have a layer of protective sheeting between the layers of the pipe itself for strength reasons.

Radio..gotta love it's many mysterious ways of getting around!


Are We

Are we drinking radio programs?

Can a filled bathtub be used for reception?

Carl Blare

Bathtub Booster

"Can a filled bathtub be used for reception?"

Try a kiddie swimming pool. You will be surprised at how much that will improve things..both RX and TX.


This answers a question I had before.

Neil, I looked at your photographs
again. What a great "on the ground"

I had asked a few weeks ago about
radials and if they would work just
sitting on the ground. Well, there's
the answer. They sure do!

I have seen ham radio portable vertical
antenna installations... What about
this set-up?

It would be really cool if you made this
permanent. But if you are unable to,
maybe you can make some kind of portable
package that you can deploy when you want.
If it was me, I'd put the whole thing in
a big plastic tool box. (Except for the antenna.)

Either way, it looks really really good.

Bruce, DRS2

P.S. I have now found all of the lost pieces to
my original outside Part 15.219 installation.
The one thing that is still hanging me up is: the
area of the yard where the transmitter was
sitting on the ground is grown over. (It was
in the corner of the back yard.) Underneath
that spot is a 16 radial ground system.

I have found the original "high Q" coil
that actually connects to the inside of
my SS-Tran AMT-3000. And two days ago,
I found the "ferrite rod" I used to fine
tune the coil.

This spot was really far from the house. I am
thinking of abandoning that ground radial system
and putting the transmitter in another spot.
I have several other projects before this one.
But finding the coil and the "ferrite rod" made
all the difference. -Bruce



"I had asked a few weeks ago about radials and if they would work just sitting on the ground. Well, there's the answer. They sure do!"

Yeah I had answered that question the day of your inquery but I guess validation was needed. Now you are assured what I said is correct. It even works good over a non-dirt surface like a parking lot or on a tennis court. Of course anyone is welcome to actually do it and find out I am correct there as well, though not necessary.

At least now there is a drawing/picture/illustration to actually visualize it, though as simple as laying down a table cloth on the dirt under a tree impressing the date on a picnic.


Passing Inspection

Would a ground area like that pass the muster? Just curious..

My first ground area was made with chicken fencing. 2 peices (48"X25') laid in an "X" configuration below the base. I soldered a few spots together where the fencing crossed to assure a good connection. I mounted things on a 3' tripod roof mount right in the center of the "X". I tested a Rangemaster and an SSTran at the same location with many hours of tweeking and peaking to assure the best of both. The SSTran won hands down. You can see the loading coil for the SSTran antenna in my avatar.

I operated both units remotely through some Cat-5 ~ 60' away from the house. I converted my 12 v.d.c. house supply to 24 volts using a voltage converter. (I'm totally off grid) Both units will handle 24 v.d.c. I used a pair for power and another pair for audio. Worked well..

The Mighty "T.H.C." Tunnel Hill Control.

Radiating Wild Animals with R.F. for Years!

Odd Even

From viewing the picture I admire the way the radials merge into a soldered twist that is formed into an upward mounting post for attaching the transmitter.

I went back to the photo to count the radials, and noticed your text gives the total as "11".

11 is an odd number. I would have thought that each branch of the radial needs its equal-opposite to avoid radiating radials.

Carl Blare

Odd Radials

There is a reason for the 11 radials and it dates back to when I made them a few years ago. I was planning on a permanent installation at the time but put it on indefinite hold. Ten radials were made and the eleventh wire was added to connect to the electrical service ground stake or a grounding rod of its own. This probably would have upset the current balance and the ground stake should have been placed in the center of the starburst rather than at its end. It may have been better if I cut this extra one off but I doubt the vertical component of the radiation was affected much.


Would It Fly?

"Would a ground area like that pass the muster? Just curious."

Why wouldn't it pass? Ground is from the surface of the Earth and on down. Anything above that surface is not ground unless it is a wire or other conductive object sticking up or over the surface directly connected to that ground radial system. In the sense of 219, keeping the ground connection from the TX to the laid down ground radial wires as short as possible is what matters, and is where that field agent is going to look.

Until the rules clearly say you cannot lay down ground radial wires on the surface of the Earth, can't see any reason why it would not be allowed.



Yup! I remember that you answered
that ground radials would work on
the ground without being buried.

Believe me when I tell you that I
completely trust your info. As far
as I'm concerned, if you say it -
it's true. I didn't need any further

I was just really excited for Neil and
was excited in general, so that's what
came out with my words on the keyboard.

If I wasn't for you and so many of the
other guys here, I would never have
learned as much as I have.

Best Wishes, and Thanks Always,
Bruce, DRS2


how about 1/4 or 1/2 wave

how about 1/4 or 1/2 wave piece of conductor laid out on ground spiraling out from tx mast to out perimeter in a circular fashion in place of tradition radials laid out symmetrically

Ya Spirals

Ya, I've wondered about a spiral ground.

I either asked about it once, or thought about asking it.

If I asked about it, it may already have been answered back then, but if I never asked, it has yet to be answered.

Heat waves cause spirals before the eyes, just prior to collapsing.

Carl Blare

Antenna Tests

Had some more time to play outdoors and did another antenna test. This time 12 10 foot radials were laid out better and the antenna was set to exactly 3 meters from tip to soil. The turns on the coil were adjusted to give resonance and the tx. input power was 98 mW with 80 mW delivered to the antenna feed point.

Using the truck radio as a receiver I drove one direction and the signal was clear and listenable out to 1.3 air miles. The noise became noticeable beyond 1.3 miles and annoying at 1.5 miles. This is encouraging.

A short walk to about 300 feet from the antenna gave a good listenable signal on a portable radio.

The transmit antenna was located 40 feet behind my house and the signal became noisy on the portable upon entering the house. The noise was electrical buzz most likely from the light dimmers. Though the audio was readable, the noise was annoying enough that I would not listen for long.

A check with my Yeasu FRG-100 receiver using an indoor short whip antenna gave about the same noisy reception as the portable. The receiver indicated S7 for the signal strength and I tuned to a broadcast station running 5 kW omni 13 miles away and it too was noisy with a signal of S7.

Given that a good transmit antenna and efficient transmitter can be used without much improvement in field strength possible the biggest obstacle to in home listening is the man made noise in the modern home environment. Absent electrical noise and with a decent outdoor receive aerial I estimate that a listenable signal can be delivered out to 1 mile. It was not unusual for at home listeners in the '50s to have such a receive system, especially in rural areas and many radios had external antenna connections. With today's radios and lacking a good aerial in home reception of part 15 AM signals seems unlikely.


Results May Vary

Neil, your testing is informative as the many combinations and unexpected variable results are all added together.

Until now I have innocently believed that an outdoor antenna would simply seem "far away" when received indoors. But the noise environment will most likely enter the picture.

I just noticed today that the LED ceiling bulbs I installed are creating a buzz field within several feet.

In some rooms when the compact fluorescents are turned on, there is hum on some radios but not others.

As regards the distance, I have been using "blocks" for measuring, but of course blocks are wildly different here and there.

I will chart out a mile in all directions to find out where that is.

Carl Blare

Varying Results

Yes, they can. I hated to sound so negative in my last post but that is the situation here. My wife likes light dimmers and they are installed in every room and some of them create RF buzz even when turned off. Recognizing that my home may not be typical in terms of interference there may be hope depending on the circumstances. I reside in a suburban area yet am unable to receive any AM broadcasts interference free indoors. Part of my problem can be due to the stucco siding which is backed by hardware cloth and metal foil covered sheathing. This could explain the low S7 readings from both my station and the broadcast station.

When I used to listen to AM I relied on my "Big Ear" outdoor dipole antenna which is located away from noise sources. This is the setup on which I received the Talking House from over two miles away.


Good News...Kinda

I repeated my tests with the outdoor antenna as described earlier and something has certainly changed. This time the signal inside my house was loud and clear on the portable radio. Two possibilities are that today the light dimmers were off and I tuned the portable to the transmit frequency (yes, you read that right). The situation is that for the outdoor test I am using a frequency 10 kHz lower than my usual frequency and I can't say for certain that I retuned the portable the other day. Nonetheless, today the reception was great.

There is another factor which is important, and that is the antenna system load resistance. The measured load resistance of my antenna system is 57 ohms at the feedpoint which indicates substantial ground R losses. Further investigation is underway concerning this.


Seeming Improvement

The results this time sound like an improvement over the other time, with of course, those uncertainties which make it all questionable.

Mentioning the dimmers reminds me of something I cannot recall. In the fog of memory it seems that, while I was once studying the various causes and cures of RFI (radio frequency interference), I think I read about some way of adding some parts to noisy dimmers to make them shut up.

Here is my pledge as we approach election time. I shall dig back in my RFI file and attempt to find secrets and methods for noise suppression, that we might apply in the constant attempt to clean up the AM dial.

Carl Blare

Hi Neil!

This will be brief. I'm on
a computer that I can't really
see well.

Going up or down one channel can
make a huge difference with noise
in your house. Maybe that's part of the
puzzle of how things changed.

I do a lot of listening between
the AM BCB and the top end of
80 meters. Some frequencies can
be obliterated by house noise.

Also, it seems to me the signal
of your transmitter should be
very strong in your house. I wonder
why it wasn't before? In my last
AM installation, the transmitter was
50 feet (at least) out in the back
yard. It wasn't strong in the house
when I first started getting it running,
but by the time it was all tuned up
it was very strong indoors.

Thank you for doing these tests. In
the long run, this will be a big
help to all of us.



Resolving Dimmer RFI

That may be more difficult than you think. Those dimmer things can throw interference a good distance and they also embed that noise onto the power wiring, like a CC system injecting its signal onto those wires.

Do not be surprised if you put dampers and suppressors on those dimmers and still hear RFI noise and even see it on that soon to arrive brand spanking new spectrum analyzer.

When it does arrive, look and be amazed at how wide band that dimmer buzz fuzz noise is across the spectrum! And how many do you have in your home? How many in the next door neighbor's house, or along the entire block?

You may be able to knock out the RFI from your own dimmers, but that does not solve the interference from someone else's dimmers.

Dimmers are not the only cause. Switching power supplies also cause RFI in homes and businesses. Gotta notch those out too.

Got a flat screen (lcd or plasma) tv? Oh..take a spectrum analyzer near one of those and think your dimmers put out noise! heh.

It's a long road to interference freedom.



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