Im working on trying to cover a five state area with my 100 MWs
Ive built a nice loading coil using a ferrite cord from an old AM radio antenna as the ferrite slug, to change inductance.
Im working on trying to cover a five state area with my 100 MWs
Ive built a nice loading coil using a ferrite cord from an old AM radio antenna as the ferrite slug, to change inductance.
The coil form is about four inches long, and about an inch in dia. There is about an eight inch space between the ferrite and the wire, ( loose coupling in a sense to the ferrite) because of how the form is made. The form is used as a spool in a receipt machine. The wire is about 22 G. might be smaller. I use this to tune a ten foot copper half inch pipe. Works very well. Basically this is a heavy duty version of a loop stick antenna. Not sure of the inductance but at 1500 the slug dosent have to be in very far to get max output from the antenna.
Here is the question I need to know from those who know.
How much energy am I loosing using a ferrite core for tuning vrs a larger air core coil with taps?
I am getting good results from the set up but havent tried a air core coil as this one is a pleasure to tune. No taps, no caps, just slide the ferrite in or out for tuning.
Any help on the question will be apriciated. Have to get back to transmitting now....
Thanks,
Radio Joe
Should read eighth inch space not eight inch (1/8 inch)
Should read eighth inch space not eight inch (1/8 inch)
Joe, that sounds like a nifty setup. Since you are using a ferrite designed for radio application and since it is barely in the coil your loss should be low. You might gain a bit by using larger wire for the coil.
The proof is in the range you are getting. Please let us know how the range is if you do a range test.
Neil
Joe, that sounds like a nifty setup. Since you are using a ferrite designed for radio application and since it is barely in the coil your loss should be low. You might gain a bit by using larger wire for the coil.
The proof is in the range you are getting. Please let us know how the range is if you do a range test.
Neil
Fortunately there will be smarter comments than mine, but with my small knowledge what I would do is a side by side test having an entire second setup identical to the first, except the second setup would have the air-core coil. Then compare the results.
Fortunately there will be smarter comments than mine, but with my small knowledge what I would do is a side by side test having an entire second setup identical to the first, except the second setup would have the air-core coil. Then compare the results.
Thanks guys, ill try to post some picture links in the next day or so.. retied now but still so busy ill hve to retire from retirmetn to get things done!
Ok, well yes the best way to test is make a air core coil then test range but too lazy at this point to do that, the one I made works so well. I basically put it all up here in minn befor the snow and cold hit in pieces an parts so nothing is mounted yet, but early trials were impressive. I think youll like the pictures, the project is turning out nice!
I think that since the ferite isnt in the core very far like Neil said the loss wont be high, I can check on the wire guage, im sure its in the range I said befor, but still effective. Just wondering though, how much loss DOES a ferrite core induce? or dosent it?
Thanks for any answers,
Joe
Thanks guys, ill try to post some picture links in the next day or so.. retied now but still so busy ill hve to retire from retirmetn to get things done!
Ok, well yes the best way to test is make a air core coil then test range but too lazy at this point to do that, the one I made works so well. I basically put it all up here in minn befor the snow and cold hit in pieces an parts so nothing is mounted yet, but early trials were impressive. I think youll like the pictures, the project is turning out nice!
I think that since the ferite isnt in the core very far like Neil said the loss wont be high, I can check on the wire guage, im sure its in the range I said befor, but still effective. Just wondering though, how much loss DOES a ferrite core induce? or dosent it?
Thanks for any answers,
Joe
Your method is like that of the Talking House internal and external antenna tunner, using a movable slug to tune the coil.
Unless you find by comparative testing that an air core coil with taps is noticably better, I'd go with the slug tuning. More precise tuning.
Another approach is to compress or expand the coil itself for tuning. I saw this done on a large scale in the Amateur Radio magazine QST.
The fellow wanted to remote tune his 160 meter (1800 kHz) antenna. He made a coil that was about 12 inches in diameter. He used a motor driven screw jack to compress or expand the coil. The large diameter coil was for high-Q. He felt the experiment was very successful.
Your method is like that of the Talking House internal and external antenna tunner, using a movable slug to tune the coil.
Unless you find by comparative testing that an air core coil with taps is noticably better, I'd go with the slug tuning. More precise tuning.
Another approach is to compress or expand the coil itself for tuning. I saw this done on a large scale in the Amateur Radio magazine QST.
The fellow wanted to remote tune his 160 meter (1800 kHz) antenna. He made a coil that was about 12 inches in diameter. He used a motor driven screw jack to compress or expand the coil. The large diameter coil was for high-Q. He felt the experiment was very successful.
I use a ferrite rod to tune the coil I use with my
SS-Tran transmitter. I works well. The
set-up is configured differently from the
coil and 3 meter antenna arrangement that most SS-Tran
experimenters have built, but it gets out OK.
I have heard a weak but clear and completely
readable signal on the car radio 2 miles away.
Best Wishes
Bruce, MICRO1690/1700
I use a ferrite rod to tune the coil I use with my
SS-Tran transmitter. I works well. The
set-up is configured differently from the
coil and 3 meter antenna arrangement that most SS-Tran
experimenters have built, but it gets out OK.
I have heard a weak but clear and completely
readable signal on the car radio 2 miles away.
Best Wishes
Bruce, MICRO1690/1700
I'm pretty sure you're actually using an iron powder rod, common mistake, made it myself before. Ferrite is usually used for filtering and Iron Powder for tuning, according to the Amidon tomes.
I have read that the trade off is that air core has higher Q but more wire and therefore more resistance
Slug tuned can have lower Q but far less wire, less resistance to an already tiny signal.
I have had far better luck with iron powder toroid and rod rod core wound inductors than with air cores. Others the opposite experience.
I'm pretty sure you're actually using an iron powder rod, common mistake, made it myself before. Ferrite is usually used for filtering and Iron Powder for tuning, according to the Amidon tomes.
I have read that the trade off is that air core has higher Q but more wire and therefore more resistance
Slug tuned can have lower Q but far less wire, less resistance to an already tiny signal.
I have had far better luck with iron powder toroid and rod rod core wound inductors than with air cores. Others the opposite experience.