Is there a difference between a RF choke and a RF coil ?

H

has.mac

Guest
"George" <nospam@mindspring.com> wrote in message
news:buhvq0tc3sq9pinkrtj5j4lamtu37qa6nq@4ax.com...
Re: Is there a difference between a RF choke and a RF coil ?

I normally think of the RF choke as a large value coil specifically used to
stop RF from travelling through it. An RF coil is any inductor used for RF
applications, typically a small value, nH, used for matching, loading, etc.
But both are coils, just different applications.

has.mac
 
Both have inductive reactance but are applied differently. A coil is used
as one element in a tuned circuit. An RF choke is used to decouple circuits
from RF ... they act as low-pass filters and can be used to block or isolate
RF.

The very same component could be either, depending on the application. Back
in the bad old days of vacuum tube rectifiers, a filter choke was often used
to block 60 or 120 Hz. ripple (so it does not have to be an RF application).
Choke means to "choke off" the ac component that is not wanted.

Generally, coils are selected to have a higher Q (inductive
reactance/resistance) and chokes often are selected for size/cost.
 
Thanks charles
That was what I was looking for to build my on base loaded antenna. I
believe I have the #18 magnetic wire, just need to find a .42 core.
This is for my RC helicopter , so the shorten range should not be a
problem. I will try several different length of piano wire to
determine best range reception starting at 6 inches.
Thanks again
 
George (nospam@mindspring.com) writes:
Thanks charles
That was what I was looking for to build my on base loaded antenna. I
believe I have the #18 magnetic wire, just need to find a .42 core.
This is for my RC helicopter , so the shorten range should not be a
problem. I will try several different length of piano wire to
determine best range reception starting at 6 inches.
Thanks again



So you posted to a slew of newsgroups, causing individual threads in
Click to expand...
each of them, and posted the question more than once to some of some of
the newsgroups, when you could have picked the most appropriate and asked
the specific question pertinent to your application than a vague quesion?


You could have picked sci.electronics.basics or sci.electronics.components
and asked "I need a coil of XXX uH for YYY application, can I use an RF
choke like I see in the catalogs, or do I have to wind something myself?"

Michael
 
I am wanting to shortin my RX wire on my RC radio sytem. The
schematic I found calls for a 1.5 uh Coil,
silver-Brown-Gold-Silver-Green You cut down the RX wire and leave 4
inches of wire on the RX, add the coil in series and add a 6 inch
piece of piano wire. The RC radio in on 72 Mhz channel 22 ( 72.230
Mhz) The original length of the RX wire is 38 1/8 inches. I have
found 1.5 uh RF chokes on Ebay, but not sure if they will work. I
would like to tune the RX antenna to 72.230 Mhz as close as I can, to
avoid signal loss.
Thanks
Remove nospam in email
nospamgem56@earthlink.net








On Fri, 3 Dec 2004 16:40:47 -0500, "Charles Schuler"
<charleschuler@comcast.net> wrote:

Both have inductive reactance but are applied differently. A coil is used
as one element in a tuned circuit. An RF choke is used to decouple circuits
from RF ... they act as low-pass filters and can be used to block or isolate
RF.

The very same component could be either, depending on the application. Back
in the bad old days of vacuum tube rectifiers, a filter choke was often used
to block 60 or 120 Hz. ripple (so it does not have to be an RF application).
Choke means to "choke off" the ac component that is not wanted.

Generally, coils are selected to have a higher Q (inductive
reactance/resistance) and chokes often are selected for size/cost.
Click to expand...
 
"George" <nospam@mindspring.com> wrote in message
news:cs44r0h52186tbgmsln1uav3ln3hsdb7d3@4ax.com...
I am wanting to shortin my RX wire on my RC radio sytem. The
schematic I found calls for a 1.5 uh Coil,
silver-Brown-Gold-Silver-Green You cut down the RX wire and leave 4
inches of wire on the RX, add the coil in series and add a 6 inch
piece of piano wire. The RC radio in on 72 Mhz channel 22 ( 72.230
Mhz) The original length of the RX wire is 38 1/8 inches. I have
found 1.5 uh RF chokes on Ebay, but not sure if they will work. I
would like to tune the RX antenna to 72.230 Mhz as close as I can, to
avoid signal loss.
Click to expand...
Yes, you can shorten an antenna by adding a loading coil (yet another name).
You will lose some performance (range).

Here is a calculator if you want to make your own loading coil:
http://my.athenet.net/~multiplx/cgi-bin/airind.main.cgi
(20 turns, 0.42 inches dia., 1 inch long is close). I'd suggest #18 magnet
wire or something similar.
 
The guy asked a simple question, not how to post in the newsgroups
How do you know which newsgroup is read by a RF coil expert ?
How much does it cost YOU for every time he post his replies ?
I have read the replies in four ( a slew) newsgroups and all gave an
example of there applications.
Maybe you can explain the difference between a 1.5 uH RF coil and a
1.5 uH RF choke ?
Bob









On 4 Dec 2004 23:05:12 GMT, et472@FreeNet.Carleton.CA (Michael Black)
wrote:

George (nospam@mindspring.com) writes:

Thanks charles
That was what I was looking for to build my on base loaded antenna. I
believe I have the #18 magnetic wire, just need to find a .42 core.
This is for my RC helicopter , so the shorten range should not be a
problem. I will try several different length of piano wire to
determine best range reception starting at 6 inches.
Thanks again



So you posted to a slew of newsgroups, causing individual threads in
each of them, and posted the question more than once to some of some of
the newsgroups, when you could have picked the most appropriate and asked
the specific question pertinent to your application than a vague quesion?


You could have picked sci.electronics.basics or sci.electronics.components
and asked "I need a coil of XXX uH for YYY application, can I use an RF
choke like I see in the catalogs, or do I have to wind something myself?"

Michael
Click to expand...
 
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