I got my AM-1 to go 3000 feet.
It wasn't easy, but I did do it.
Since the houses are close together
in our neighborhood, it could have
been heard by many people, if they
wanted to.
At a park, about 1/2 mile away, I
plunked a GE Superadio down on a
picnic table with some friends and
listened to the AM-1. It didn't sound
too bad. There was some noise, but
not too much. The GE Superadio is very
sensitive, but not as sensitive as a
car radio. At least that is what I
think.
It was a long time ago. But for the
first 1000 feet out from the transmitter,
it was strong. Until I had it grounded
correctly, it also got into the telephone,
although it was not very loud.
There were also some "hot spots" on the
car radio about a mile away in various
different directions.
My loading coil was HUGE. It was on a bucket
from the local ACE hardware store. Later,
I made it into a variometer, which was
helpful. Rather than explain what a variometer
is to those who don't know - I suggest Googling
variometer is probably a good way to find out
about it.
It also got into certain parts of West Hartford
center (1/2 mile away) on a really sensitive car
radio. Not as well as my SS-Tran, but it did appear
in some spots.
I don't know why it worked so well. I spent
literally months fooling around with the
loading coil.
Bruce, SLUG 88.3
Well, where do I begin? So many modifications, so little time...I think I will build the AM1 for the primary and try using the TH for the backup (with proper modifications)...I've got an audio mixer (or two), cd players, mp3 players, microphones, and a laptop or two to dedicate to the studio, so once the transmitter and the antenna is built, I should be able to fire it up...I will be transmitting around 1000-1150 KHz somewhere around there...stay tuned!
I got the transmitter (AM1) built. I don't know how much it's putting out, as I don't have a wattmeter that measures less than about 5 watts...now to build the antenna...I think I will put the transmitter in a weather tight box up high outside...what type of antenna should I build to compliment this setup? Any ideas?
3-meter (10-foot) vertical wire or pipe.
There is no other choice for AM.
Be sure to ground the transmitter either with a ground rod in the ground, connection to electric system ground, or ground radials. The ground makes the antenna work its best.
Can I bury radials in the ground...or is that even legal on part 15?
Dave VQX
Yes. Radials are legal for part 15. The reason they are legal is that they do not radiate themselves, but they do provide a return path to complete the circuit for the antenna to radiate over a much larger distance.
PhilB, another member, recommends radials at least 30-feet long, and I think 16 or 32 of them.
Radio8z has had good luck with 10-foot radials, I think he has 12 of them. There are recent postings about radio8z's installation with pictures.
What should I use for durability? Would aluminum be ok, (or steel), or should I just stick with copper? Sorry to be a pain, I know I'm in good hands here.
If you have some metal, go ahead and use it, then if it can be improved make the upgrade later.
All of the metals you named will work, although I think copper is considered best probably for overall exposure to the weather over a long time. More knowledgable members may have more to say.
There are many very informative postings on the site, do some searches.
Sorry to be such a pest, just getting anxious/excited...thanks for all the help...
Dave VQX
Dave,
It is always neat to follow the progress of a new build and I hope you will keep us up to date as this progresses. Here's some advice from one who has been down this road more than once.
Don't expect the antenna system and transmitter combo to work the first time. For best range the antenna system needs to be resonant and this is hard to find because of the very sharp tuning peak. Don't get discouraged (I almost did), you will find it when you get the right inductance for the loading coil. The antenna system I built shown in this LINK needed a 260 uH coil the inductance of which I determined by experiment. I started with 76 turns of #18 enameled wire close wound on a 3" form and removed one turn at a time until I found resonance. Once found I removed 2 more turns and added a movable coil of 3 turns which allows for really fine tuning the resonance. Some prefer to use coil taps but I think the movable coil is easier to use. There is an accurate coil design program which I have used at this link which is really nice because you can use almost any form dimension and wire size. I have had problems with PVC as a coil form and I recommend you avoid this. Maybe a HDPE bottle or food container of the right diameter and length (about 3 x 3 inches) can be found. My experiments with HDPE show no effect on tuning as opposed to PVC. Here's a LINK to the description of a cover I added to the antenna to protect the coil.
The radiator can be metal tubing and I recommend 3/4 inch dia. aluminum. Connecting a lead wire to aluminum is an adventure and some sort of clamp should be used. Make sure to make this water tight because aluminum and lead wires will be destroyed by electrolysis if it gets wet. If you choose copper pipe make sure you get type K which has a thicker wall than type M commonly found at big box home improvement stores. They should have both types. Check out the SSTRAN link in the left panel. The site has a link to antenna construction plans you might find interesting.
It is possible to use PVC pipe with a wire threaded up the center and a cap on top for the radiator but my experience with PVC pipe is that it is mechanically weak and a 10' length won't stay vertical unless guyed. Others recommend using a fiberglass pole but I have no experience with this.
This is a lot of info but don't let it bog you down. These are just suggestions and you probably can improve on them. One thing to remember is that if you build something you are not married to it so you can change it or throw it away and start again. This is how progress works.
Neil