I’ll try a story about my antenna.
I may have to tell about the antenna in a couple of installments…
I’ll try a story about my antenna.
I may have to tell about the antenna in a couple of installments…
I’ll also say from the get go that I may say something that may not pertain to part 15 proper, but the story is about the antenna, not the operation of my radio station.
Before starting the part 15, my group tested a couple well known transmitters. I don’t have to name them, you know them. This group consists of actual AM engineers, so besides my opinion, their opinion counted.
The popular transmitters were only good with a good antenna. Both tx’s recommended a CB-type whip antenna. And, if you like 500 feet of pure signal, they are just fine.
I ended up purchasing a sstran transmitter kit, which one of our engineers built for me. It came with the traditional 3 foot wire antenna, and to tell the truth, the transmitter put out exactly the same signal that the popular, expensive ones put out with a CB whip. I knew a CB whip isn’t tuned to the AM band, and it certainly isn’t tunable.
Phil Boylan, who owns sstran tx company was very helpful with my setup. But I had a ton of questions, and one of them led to Phil doing two things; redesigning the tx so that it could accept a coil/base loaded antenna, and designing such an antenna. We wanted this to remain part 15 acceptable.
I use an antenna very very similar to what Phil designed. It consists of a coil, which is magnetic wire which includes taps, wound around a piece of pvc pipe. The antenna itself is copper pipe, which sits upon pvc, which acts as an insulator.
Basically, your antenna wire runs to a selected tap on this coil, the top of the coil attaches to the copper pipe. The copper pipe antenna is adjustable, built with about one foot of 3/4″ pipe, and inside sits about 9 feet of 1/2″ pipe (these lengths are estimates, actual footage to remain legal is on the sstran.com site.
And that is key; in order to make the antenna “resonant” to your frequency, you can raise up, or lower your antenna, more accurately than cutting a piece of wire, more or less rendering you off the air.
My first incarnation of this antenna was built inside during the winter. I live in a metal mobile home, and I set it against the house to test it. I got nowhere, but the reason was I was up against a metal house.
When spring came, I purchased a 10 foot iron pipe, 4 inches across, and also purchased various pieces of pvc to attach to it in order for it to accept the (about) 2″ pvc adapter which holds the copper antenna pipe.
This put together, I dug a good hole in the ground and cemented the iron pipe into the ground. With the iron pipe, my antenna stood about 25 feet high at the tip, and I placed it about 12 feet from the house.
The biggest trick to this installation is making sure the iron pipe is really cemented into the ground, and that you have a ladder whereby you can reach the point where 3/4″ and 1/2″ pipe come together. That is where you tune the antenna.
I also should mention that the coil needs to be as close to this copper pipe junction as possible. In my case, I actually ran the coil and tx from the ground, encased in a large Rubbermaid tote, because at the time I had no way to mount it way up there. (See?…I learned from my mistake; I couldn’t climb up that pole!)
I’ve been in AM radio, and I know that radials are helpful. In my case, my backyard has a tendency to remain damp and in most cases, wet. A wet ground is excellent for AM radio broadcasting, so this area was perfect.
With 100mW broadcasting, radials can help your signal. In standard AM broadcasting, there are 360 radials per tower, which could run into quite a bit of copper, and then quite a bit of money. In our case, just several, to notice the difference is required, and that may be just 10 radials.
I bought copper strand wire, and a hose clamp. The clamp went around the base of the iron support pipe. You want to make sure you can see the iron, and not any paint, so you may have to sand it.
I laid the copper wire radials out in equal lengths, about 10 feet each, and separated equally, like a clock. I buried them a couple inches into the ground and then soldered them to the iron pipe, tightening it all down with that pipe clamp.
After some tuning, (that is another story) I found phenomenal results.
Well, here is the story; I didn’t have a Field Strength meter, so the best I could do was to tune off frequency, try to tune the antenna, STEP BACK, and listen.
The louder I got off frequency, the better I was, and I did this til I got a signal that covered the entire high band. I was on 1540 khz, with 1590 down the road, and I killed 1590 for a mile. So I knew I had it right.
Now comes the sad news; My trailer park “outlawed” antennas. So, it had to come down if I was to stay living here, and down it came. I thought of everything…using wires around the house, up the house, etc, etc, and I did try some of these things knowing they would not work.
And they didn’t.
So, I had to build this antenna all over again, and DISGUISE it.
In short, I decided to build a pvc pipe flagpole over it, and even now, Ol’ Glory hangs beside my house on what contains my copper AM radio antenna.
Does it work?
Yes it does, although at this time I’m having some problems related to a couple ground shorts; tonight I may have solved the problem, but the point is that the pvc does not kill your signal if you have to hide an antenna.
I had to make the flagpole look like a flagpole and not an antenna, and I had to hide the transmitter and coil, so I built a box around it. You should see me working inside that box, and no one really knows what I’m up to. Ultimately it will be a planter when everything is soldered up right.
It is a good idea for someone in a position like mine, where you want your station on the air, but you are not allowed to have an antenna.
This is a great hobby for me, and when I achieve this goal, which I will, I’ll probably move onto something else. And that something else is a SECRET!! 🙂 Well, for now anyway. Share your antenna ideas with us!
The cost of building the antenna: The magnetic wire cost the most, about $25 bucks but I had enough to
build two coils and had extra, and btw, it was a good thing I bought extra; I ruined the first coil.
The parts for the antenna cost about 30 bucks, but I needed everything and you may have some pvc or copper laying around.
Once built, you can move it, adjust it, move it again. Be careful, the smallest pvc part is very fragile, just like an insulator,otherwise, it is easy to build and is kind of a fun project.