My teams finally started assembeling the AMT3000 today. I havent felt this giddy since I built my first computer. Anyway, then antenna is allways on my my mind. Unfortunatly I just cant afford to build the great lookin coil loaded job on the sstran site. Although I probably will once school gets out in June.
For now I only require an antenna that will get me a few hundred feet. (just enought to get around the building) I was thinking of using a 108in whip with a series inductor.
My teams finally started assembeling the AMT3000 today. I havent felt this giddy since I built my first computer. Anyway, then antenna is allways on my my mind. Unfortunatly I just cant afford to build the great lookin coil loaded job on the sstran site. Although I probably will once school gets out in June.
For now I only require an antenna that will get me a few hundred feet. (just enought to get around the building) I was thinking of using a 108in whip with a series inductor. Will this crude setup get me the range I need? If not any suggestions? Also am I gonna run into a problem if I have to have the Antenna indoors? (I'm not shure if I'll be able to get the school to let me put it on the roof)
Hi!
The range of having your antenna indoors will depend on many factors including the construction of your building. It's also going to depend on what kind of radios are tuning your station. Some radios just don't perform well enough to work at any distance from a low power transmitter.
I tested one of our transmitters inside our office building this past summer and the range was severely restricted to about 50 feet. To be fair our walls are plaster over a wire mesh and that blocks most of the signal.
Are you going to use the building's electrical ground as your antenna ground?
You have a lot of variables, all of which could affect your range. I guess it just comes down to doing some testing when your transmitter is built.
Hi,
Techpuppy said some good things. I would add that when my class put a Ramsey AM on the air in the classroom we didn't get good range and had a lot of noise. We got about 20 feet or so, but the receiver was a cheap unit that had trouble receiving local stations and the Ramsey unit has no provision for tuning to the antenna. I then tossed the ant out the window with no ground and the signal could be heard in the parking lots.
If you already don't have a whip antenna, don't buy one. Just use a piece of vertical wire. Try the power line ground, or run some wires horizontal for a ground. You will not have a lot of range, and will probably have some hum issues. You are starting with an excellent transmitter, but the environment is the big challenge.
Don't forget to check the transmitter adjustments if you change anything. As far as trying a coil loaded ant goes, try it. Not much to lose, especially if you build it from scraps.
I currently run my AMT3000 into a resonant antenna in my basement and get a range of about 200 feet away from my house on a portable radio. Transmitting from inside a campus building is probably worse than from my basement. Just don't expect much range, but start with that and improve things one at a time.
I think you are a long way from asking for permission to use the roof. You mentioned in another post that you might experiment at home. Do that first then apply what you learn on campus.
Neil
Y'all,
Well, I strung the wire in the attic & made a path for the roof-fixers to get to a spot that a roofer had failed to finish off nicely a couple years back. Yeah, a couple years. Noticed it this year 'cause there was signs of dessicated water on the Christmas ornaments boxes. Neat.
As to the antoona: I hung a huge stretch of wire across the rafters & discovered that the AMT3000 works best with just the legal limit . . . at 1700 kHz. This led me to other stupid ideas and eventually I ended up back with the Modern Radio Labs #2 DX Crystal Set schemo. I used it a couple times (the schemo) on various LF/VLF/MF doodads & it does, for want of a better term, kick. Very selective, if you set it up like that.
So I got 11 inches of 3-inch ID PVC (keep it around for crystal sets) and went to Roger's for two large spools of Teflon covered silver-plate. Wound many turns. Hosed the capacitors up. Removed many turns. Removed more turns. Cut it back to about 7 inches of pipe. Then back to the capacitors &c. Got the beast to work in the selective setting of the crystal set schemo. Very sharp.
Notes:
#1. I am going to put a serious antenna meter in the box. The Stockton Wattmeter is a nice circuit but I only need one half of it. And it don't work unbalanced. More trial and error, but it's a necessity. And not a digital meter. I like seeing the needle bounce around.
#2. I have not set the mods for using an external tuning circuit (like the base loaded antoona). That process will come when I get the rest of the LC circuit together in one box. Best part of that is it's all gonna be PVC pipe. Even the radiator. Hang some of this Teflon from the top to the bottom of a chunk of small diameter PVC (left over from 6m experiments) and figure how to put the tuning caps in there & still have 'em accessible. Need to take many breaks on that one. Glue fumes, well, it was the 60s, see?
#3. The DC Kits PLL SFM board now feeds a real antenna (as real as I can get using heavy gauge house wire & double-sided PCB. The stock signal gets out easy a couple tenths of a mile. QRO gets an easy 2. I think the antenna's too good now.
#4. There's a Norteña estacion on 1700. I can hear it during the day. Still ain't figured out where it is. Bein' as I have many vecinos chicanos, I think I'll find another frequency. Who knows who's listening. Coverin' up Grupo Exterminador with Archie Shepp might be a bit unneighborly.
Every time I get down in the MF stuff I end up back with ol' Elmer Osterhoudt's circuit books. HF is easy. VHF is more like plumbing. MF is plain carpentry. LF/VLF, well, I ain't got the real estate for that. And yet, still I try. (Like that Procol Harum song "Still there'll be more.")
So yes, it is possible to be satisfied with creepy antennas made out of plumbing pipe and Teflon spool remainders. Ok, you don't need the Teflon. But it's so easy to work with: the insulation don't melt!
73
Nils
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La Estancia de los Guajolotes Sonrientes
W8IJN - http://w8ijn.tripod.com
If I do end up being restricted to transmitting from inside, can I use the ground from an electrical outlet? Is that really gonna gain me anything as opposed to just stringing up a piece of wire?
I got alot of good ideas. Problem is, most of em suck.
George Carlin (WINO)
Hi,
Yes, you can use the power line ground. You might experience some noise pickup. The AMT-3000 has jumpers for three inductors. I found that my unit works best if the inductors are in the circuit (jumpers off). Your ground connection should be from the shell of the antenna connector. If the inductors are in the circuit, then the power ground from the wall wart transformer and audio grounds are not RF grounds.
Is the power line ground better than no ground? There is only one way to tell...try it both ways. Don't forget to retune the transmitter antenna match C5 with each change you make.
With part 15 AM we are trying to squeeze every nanowatt out of our signal. Since each setup is different, experimentation is the best way to find out what works and what doesn't. As you experiment, change only one thing at a time and check the results.
Hope this helps.
Neil