I wanted to try this too. All I wanted
was a red LED on top of the 1690/1700
"3 meter or less" stick.
I never figured out how to do it through.
Use a germanium diode in front of the LED, no resistor needed. Need more brightness? Series more germanium diodes.
-------->|--->|--->"|---------
ant / gd / gd / led / ant
You can also experiment and try fast switching diodes for those super bright led's.
RFB
The lady I rent from is the islands primary florist, she's got plenty of germaniums. I see if I can get some for my antenna.
Anyone else wants some, just let me know, I could get a good deal on them for you
Don't you see where this is headed? The antennas are becoming art projects.
A botanical antenna?
Antenna light shows?
Maybe this is what will make part 15 a mainline cultural event.
Concerto for antenna and orchestra from a 1950s Boris Karlof vampire movie.
Zorro's whip antenna.
Antenna pole dancing.
How about a new show to boot...titled "The Little Lit Whip Hour" 🙂
RFB
And that brings another 80's song to mind..
now whip it
into shape
shape it up
get straight
go forward
move ahead
try to detect it
it's not too late
to whip it
whip it good
--DEVO Whip it.
So to RFB, where is the best place to put just
one LED (and the 2 1N34s or whatever)
on the antenna? (I figure I'll
start with just one.)
And, I guess some hams once had a plan
to use a tree for an antenna. I'll have to
look that up.
Best Wishes,
Bruce, MICRO1690/1700
P.S. Oh, yeah - I guess the
diodes on the antenna will
make some harmonics or
mixing products?? Well, if
so, that's OK. It's just part
of the education
As you know, the short length of a Part 15 stick does not allow the RF current to flow evenly along the short length, it tends to stay mostly at the lower to mid section of the element. With a cap hat, that will help distribute that energy more evenly across the short length, and is why a cap hat seriously improves the performance of a Part 15 3 meter stick. If you add a cap hat, you have to shorten the length of the antenna to make the total length stay within 3 meters.
My past experiments with an antenna sporting a 2 foot diamater cap hat and 7 foot long antenna not only improved the performance over a 9 foot long antenna, but also helped with the bandwidth tremendously. That is the antenna was able to tune with a much wider range on a frequency which seriously improved the sound of the signal. Increasing the diameter size of the antenna also helps because your signal is on the surface of the antenna, and the wider the element, the better the footprint.
The cap hat allowed me to place a small light closer to the top, and also made the rest of the lights shine more evenly across the entire length.
Keep in mind, the very weak RF on that antenna from 100mW is not going to make them light up with the brightness of a set of decoration lights that plug into a wall socket. But they will light enough to see that the antenna has lights on it, especially if your antenna sits in a dark area where no light is present..ie from a street light or security light/porch light.
Adding lights will affect tuning, but that can be compensated for by simply re-tuning the antenna on the loading coil by selecting another tap point or adjusting the variable cap across it. I did not observe any significant noise or spurious junk on the spectrum analyzer with either standard bulbs or the led. My Christmas stick used standard incandescent grain of wheat bulbs. The led experiment was an attempt to model an actual broadcast tower with the all familiar "red" beacon light at the top and sides.
This lit stick project was more of playing around cuz I am board kind of thing and was not intended to try to do anything in the way of improving performance. It probably wont improve anything, but I know in my experiments it did not degrade performance to a point where the antenna became useless. Also keep in mind I was operating at the upper end of the band as well. I have not attempted the "lit whip" experiments on the low end of the band. I stay away from the low end of the band when using the intentional radiator simply because a 3 meter long antenna even with a properly built loading coil is still highly inefficient and wont throw the signal as good as it will in the upper part of the band.
Another way to work this experiment is to take a pvc pipe and insert that inside the copper or aluminum pipe that is the actual emitter element. The pvc pipe will provide you with an inside insulator to run a pair of wires for feeding DC up to the top to power a light. It is also a great way to add de-icing to the antenna by inserting at regular spaced intervals a few resistors to create heat. Re-tuning will be required as well as adding chokes at the bottom to keep the RF on the wires from going into the power source. Use a pvc cap at the top instead of a copper or aluminum cap to mount the light. Seal it with silicone and your set.
To mount side lights or any lights without chopping the antenna into segments and feeding the lights with DC voltage instead of relying on the weak RF to power them, use the inserted pvc pipe method and then simply drill small holes just large enough to let the light/led stick through.
Feed the pre-wired light from the outside through each hole and as you feed it into the holes, make sure the wires are thin enough to be flexible and head in the right direction..downward to the power source. I use a salvaged Li-Ion battery charged by a solar panel. Using led's, the current draw is so little that the battery has yet to drain to a point where the solar panel has to charge it heavily during the day. The lights stay on continuously which who cares if they do....they will be lit at night when it really counts and also saves from having to add a switch or some over kill relay/photo sensor scheme for turning them off during the day, on at night...but you can add that too if you want. It is not difficult and would add more to the overall project.
To add sunrise/sunset on and off automatic functionality, use a photo cell and a simple TTL circuit with a transistor as a switch. Run the photo cell into the base of the transistor and the other side of it biased with about .5 volts. During the day, the photo cell has high resistance and shuts off the .5 volts bias to the base of the NPN transistor. At night, its resistance decreases enough to allow enough of the .5 volts to feed the transistor to turn it on. Connect the emitter to ground of the power source, and the collector to the negative side of the led light/array..and wala...an automatic day/night on and off circuit to control your led lights.
If you use the super bright led's, they will require a bit more current, so you will have to experiment with the biasing of the transistor and photo cell as well as use a transistor that will pass a bit more current. An NTE 128 NPN transistor will do the job for both normal bright led's as well as the super bright led's. I recommend using clear lens types and not the defused types. Increase the photo cell bias to about .9 volts. Use a series of 1n4001's to drop the raw voltage down, or a voltage regulator. Small solar cells are incredibly cheap and can be series connected to provide good charge voltage and current for the Li-Ion battery.
Oh..almost forgot. The "tree" antenna. Take an old aluminum Christmas tree, about a 6 footer and experiment away! Mount it upside down so that the wide branches are at the top. That one is fun..trust me! And you be amazed at how well it works!
Enjoy!
RFB
Thanks RFB!
Wow, you sure have a lot of good information!
I was over on your Carrier Current blog.
That was great, too!
Thanks again!
Bruce, MICRO1690/1700
Some have opposite function when light is present versus no light, that is with light onto the photo cell, the photo cell decreases its resistance and lets current flow, and when no light is present, it increases the resistance...so make sure you get the right kind. If you can only find one or the other, you can use a flip-flop circuit or simple logic gate to invert the photo cell's function to get the correct on/off trigger for the NPN transistor's base connection.
RFB