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Need More R
- Thread starter C2
- Start date
If the antenna is truly resonant where you want it....forget the rest. Everything's fine...if your meters are accurate.
Good luck
Good luck
Now you have a decent reason to make one for this antenna.
Besides, you can always go to Halted (or is it 'Haltek'?) Electronics on Central Expwy/Santa Clara; they have a lot of cool stuff there like that.
Besides, you can always go to Halted (or is it 'Haltek'?) Electronics on Central Expwy/Santa Clara; they have a lot of cool stuff there like that.
It's tired so it's laying down. Lean over and look at it.
(+)
--//////------<|
---'
(G)
Allowing for the 'superb' graphics, ever see something like that before? It works. It does introduce reactances, but they are not in the antenna so the antenna is still resonant. They are in the impedance matching device where they are doing something constructive, which means that particular reactance ain't 'bad'. That 'device' produces something the feed line and transmitter will be happy to see, 50 ohms.
Those coil turns above the (G) tap are generally there to 'load' the antenna if needed. If they are not needed, they don't have to be there. The coil turns between the (+) and (G) tap are the ones that produce the 50R - 0X the rest of the system sees. Called an inductive match. Same thing can be done in a slightly different configuration for a capacitive match. Same results, different way of getting them. (Coils are easier! Don't have to have a bucket of caps to try out.)
Don't necessarily need a torroid, just wrap the coil on a broom stick, tie the antenna to the top of the broom stick. (RedNeck radio practices!)
- 'Doc
(+)
--//////------<|
---'
(G)
Allowing for the 'superb' graphics, ever see something like that before? It works. It does introduce reactances, but they are not in the antenna so the antenna is still resonant. They are in the impedance matching device where they are doing something constructive, which means that particular reactance ain't 'bad'. That 'device' produces something the feed line and transmitter will be happy to see, 50 ohms.
Those coil turns above the (G) tap are generally there to 'load' the antenna if needed. If they are not needed, they don't have to be there. The coil turns between the (+) and (G) tap are the ones that produce the 50R - 0X the rest of the system sees. Called an inductive match. Same thing can be done in a slightly different configuration for a capacitive match. Same results, different way of getting them. (Coils are easier! Don't have to have a bucket of caps to try out.)
Don't necessarily need a torroid, just wrap the coil on a broom stick, tie the antenna to the top of the broom stick. (RedNeck radio practices!)
- 'Doc
C2,
In your diagram you have a loading coil, not an impedance matching coil. So while the antenna can certainly be resonant, nothing is being done to match impedances which are not 'close'.
I'm not too sure where to go with that comparison with a dipole. Assuming the antenna is a vertical, then you're also mixing polarity in that comparison, which will always produce some dissimilarities. I'm also assuming that the dipole is horizontal, so could certainly be heading for 'left field' with that.
Am I assuming too much?
- 'Doc
In your diagram you have a loading coil, not an impedance matching coil. So while the antenna can certainly be resonant, nothing is being done to match impedances which are not 'close'.
I'm not too sure where to go with that comparison with a dipole. Assuming the antenna is a vertical, then you're also mixing polarity in that comparison, which will always produce some dissimilarities. I'm also assuming that the dipole is horizontal, so could certainly be heading for 'left field' with that.
Am I assuming too much?
- 'Doc
The difference between 'Doc's version and yours is that 'Doc's version has the feedpoint isolated from ground.
If I'm not correct at interpretting those superb graphics, I'm going to blame it on the glass of Wild Turkey/rocks that I'm sipping on whilst tipping my head to the right. If I do that one more time I might fall over... :blink:
Let me re-do that 'superb' graphics again. Just made a mistake in 'signs'.
(G)--/////------<|
(+)----'
That ought to make a little more sense.
The above privides one variable, the (+) tap point. If you want two variables, make either the antenna, or (G) points variable. Or you can have three variables by making all of them taps that can be varied.
If you have at least a 'ball-park' guess as to the size of that coil, you can probably make do with just the one tap point of the center conductor. If you aren't sure about the size of the coil at all, making all three taps variable, then adjusting each separately for nearest reading, makes it sort of inevitable that you'll find the 'right' match. ... eventually.
- 'Doc
(All us geniuses gotta make dumb mistakes like this every once in a while. Other wise, people start expecting too much! You know? It's a 'genius' thing!)
If you won't go for that one, I can always tell about being in my second childhood and being one'a them prodigies... I get to ride that 'special' bus to Wal-Mart too!
(G)--/////------<|
(+)----'
That ought to make a little more sense.
The above privides one variable, the (+) tap point. If you want two variables, make either the antenna, or (G) points variable. Or you can have three variables by making all of them taps that can be varied.
If you have at least a 'ball-park' guess as to the size of that coil, you can probably make do with just the one tap point of the center conductor. If you aren't sure about the size of the coil at all, making all three taps variable, then adjusting each separately for nearest reading, makes it sort of inevitable that you'll find the 'right' match. ... eventually.
- 'Doc
(All us geniuses gotta make dumb mistakes like this every once in a while. Other wise, people start expecting too much! You know? It's a 'genius' thing!)
If you won't go for that one, I can always tell about being in my second childhood and being one'a them prodigies... I get to ride that 'special' bus to Wal-Mart too!
Now THAT makes a lot more sense....it's the standard coil matching system. Darn it 'Doc...I was flipping through my ARRL Antenna book trying to find your first version while sipping on my Wild Turkey. Needless to say, I was starting to get confused.
BTW, you still need the ground side of the coil insulated from top part of the coil.
BTW, you still need the ground side of the coil insulated from top part of the coil.
- No one is chatting at the moment.
