Hi I am new to this I am using a spitfire tx and I well be having the standard 3 meter copper pipe radiator .i wanted make a good loading coil so I went out and 120 feet of 8 g soled copper wire and 6 diameter pvc pipe that is a bit over two feet in hight can anyone out there till how many feet to roll on the pipe and in what detection . Thanks riv
Welcome to the forum and hello from Dublin, Oh.
The design of the loading coil depends on the inductance required to bring the antenna system into resonance. This is usually around 250 microHenries but it can vary quite a bit from this depending on several things.
Here's a link to a calculator which can be used to answer your question about the coil. Start with 250 uH and the dimensions of your pipe and it will calculate the number of turns and wire length.
http://www.k7mem.com/Electronic_Notebook/inductors/coildsgn.html
It is a good idea to start with more turns than needed and change the tap on the coil to get resonance. Resonance can be detected by listening for an increase in the strength of the received signal.
If you need more help please ask.
Neil
I just ran the calculator linked above and got an answer which is not very realistic in terms of coil length and wire length.
You might consider a different design. I used a 3 inch form and wound #18 enameled wire for the coil. The coil length is just over 3 inches. I don't recall the number of turns but you can run the calculator for this. This coil works very well and gives a sharp resonance.
Neil
Radio8z,
What do you mean by sharp resonance?
"What do you mean by sharp resonance?"</em"
This is an old radio term which is another way of saying the circuit is high Q. A high Q resonant circuit will have a narrow bandwidth and tuning is quite sensitive as it moves through resonance, hence it tunes sharply. Another way this applies is if the response curve is plotted as gain vs. frequency the resonant peak is sharp.
Conversely, a low Q circuit will have a wide bandwidth, changes with tuning will be slow, and the curve will have a broad peak.
I posted using "sharp" to indicate that the coil is high Q and I thank you for asking since I shouldn't have assumed all knew what this meant.
Neil
"What do you mean by sharp resonance?"
This is an old radio term which is another way of saying the circuit is high Q. A high Q resonant circuit will have a narrow bandwidth and tuning is quite sensitive as it moves through resonance, hence it tunes sharply. Another way this applies is if the response curve is plotted as gain vs. frequency the resonant peak is sharp.
Conversely, a low Q circuit will have a wide bandwidth, changes with tuning will be slight, and the curve will have a broad peak.
I posted using "sharp" to indicate that the coil is high Q and I thank you for asking since I shouldn't have assumed all knew what this meant.
Neil
Not sure where it is, but if you look back thru the archives you might find one where I described 3/4" copper pipe height adjustment went in and out of peak within the width of a relatively new sharpie pen. Base-loaded coil - IIRC, 67 turns of vinyl-jacketed 16 AWG fine multistrand wire on a 4" white PVC sewer pipe - .215 wall. Believe it or not, fine multistrand jacketed wire was what was called for in the plans. The jacket provides some separation between turns to counteract loss due to current eddies, and fine multistrand wire provides more total surface area than solid wire. It's strictly a one-off design spec'd for 1650 kHz. With sea water ground connected through my boat's ground system, I could get a slightly noisy signal on a Honda radio as far as 3 miles on a good day, about 1.5 mi. in a 1998 Astro van, and S8 at 8 mi. with an expensive multiband ham radio receiver (lots of filters and preamps) using a 300' longwire antenna. I can't get that on land with rocky ground anymore, but i'm working on a bottom-coil-fed high efficiency eight-wire inverted conical with a buried underground R-11 low-loss cable and 48 @ 20' buried radials. I also have a big bottle full of pennies I intend to pound into the ground... I hope it works 😉
for building coils and short part 15 antennas, this device is the best $65 you can spend. affordable chinese sweatshop antenna analyzer has netted me a 1.3:1 or better SWR with my all my part 15 installs
The specs for that MR100 analyzer show that is designed for the 1 to 60 meter bands, IOW, a frequency band well above the standard AM broadcast band. But it does include the FM broadcast band.
Edit by Moderator: The Ebay seller advised the range of operation is 1 MHz to 60 MHz and not 1 meter to 60 meters.
nope, it works from 1-60 MHz. i know because i have one. chinese to english language barriers are very real