Rx antennas: can I do this?  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       

All Forums >> RC Airplanes >> Tips & Techniques >> Rx antennas: can I do this?
Page: [1] 2   next >   >>  

Login
Message << Older Topic   Newer Topic >>
Rx antennas: can I do this? - 12/8/2007 1:17:52 AM   
H5606


 

Posts: 82
Joined: 7/17/2006
From: , MD, USA
Status: offline 		Can I do this to a Futaba 7-channel 72 MHz FM receiver and still have decent range?

Attachments
Click to see fullsize image.
Click for fullsize
       Post #: 1

RE: Rx antennas: can I do this? - 12/8/2007 1:53:32 AM   
Laird SS


 

Posts: 226
Joined: 4/17/2005
From: Peoria, AZ, USA
Status: offline 		I wouldn't recommend it. The receiver needs to have the antenna extended to its full length to receive signals of a strength to allow reliable operation. Shortening the antenna like that will cause problems. Why not run it in a soda straw (or something similar) inside of the fuselage if you just want to hide it?

(in reply to H5606)
       Post #: 2

RE: Rx antennas: can I do this? - 12/8/2007 1:56:14 AM   
gary9648


 

Posts: 1175
Joined: 10/22/2002
From: Troy, OH, USA
Status: offline 		I concur, that coil you created will change the tuning of the ant. Stretch it out to it's fullest lenght. however, if you are only flying it indoors, do a range check and if OK, fly it like that. Just set it down and move to the other side of the room the longest distance from the plane and see if you still have control. I would not fly it that way out side though.

< Message edited by gary9648 -- 12/8/2007 1:59:32 AM >

(in reply to Laird SS)
       Post #: 3

RE: Rx antennas: can I do this? - 12/8/2007 2:01:47 AM   
RCKen



Posts: 14714
Joined: 7/10/2002
From: Lawton, OK, USA
Status: online 		This asking for trouble. When you coil up an antenna like that you reduce it's overall length, thus reducing the range.

Ken

_____________________________

The take off is optional, but the landing is MANDATORY!!
AMA # 712539 www.gettingairborne.com
Moderator- Beginner''s, Sport Flying, Off-Topic, & AMA Discussions
RCU Community Moderator

(in reply to gary9648)
       Post #: 4

RE: Rx antennas: can I do this? - 12/8/2007 2:16:18 AM   
H5606


 

Posts: 82
Joined: 7/17/2006
From: , MD, USA
Status: offline 		The receiver in the picture is a Hitec 555 that I've been flying in that configuration without difficulty for several years. The coil is stacked and at no point does the antenna cross over itself. I was wondering if anybody had done the same with a Futaba Rx and had similar success.

(in reply to RCKen)
       Post #: 5

RE: Rx antennas: can I do this? - 12/8/2007 3:44:28 AM   
BadSplice



Posts: 431
Joined: 2/27/2004
From: Nevada City , CA, USA
Status: offline 		I have done similar with a few different reciever, though I keep at least 1/4" between the wires in the coil, usually wrapped around a piece of cardboard or foam that can be taped to an inside wall. Especially useful for using JR radios in park flyers... (man those jr antennas are long) But done in a couple gas planes with really long range checks and no problems.

_____________________________

May the Force be With You; and if necessary, be prepared to go to the Hobby Shop and get More Force!

(in reply to H5606)
       Post #: 6

RE: Rx antennas: can I do this? - 12/8/2007 11:39:42 AM   
Ed Smith


 

Posts: 2834
Joined: 12/29/2001
From: Brantford, ON, CANADA
Status: offline 		We have been doing it for years in the limited space inside a Pylon Racer. Usually wrapped around a dog bone shaped piece of balsa or cardboard.

Important that the antenna coil does not overlap anywhere.

Ed S

(in reply to H5606)
       Post #: 7

RE: Rx antennas: can I do this? - 12/8/2007 1:19:54 PM   
dbacque


 

Posts: 380
Joined: 6/3/2005
From: Houston, TX, USA
Status: offline 		A whip antenna http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKX47&P=7 makes for a neat installation. It keeps everything confined in the fuselage with no significant loss of range.

Dave

(in reply to Ed Smith)
       Post #: 8

RE: Rx antennas: can I do this? - 12/8/2007 3:27:37 PM   
js3



Posts: 1142
Joined: 1/30/2002
From: Arvada, CO, USA
Status: offline
quote:

ORIGINAL: H5606

Can I do this to a Futaba 7-channel 72 MHz FM receiver and still have decent range?


Yes, you can do this without significant loss of range. Just make sure the wires don't cross (as you said) and I prefer to have them not touch each other as well.

It works very well.

_____________________________

John
I feel a lot more like I do now than I did earlier!

(in reply to H5606)
       Post #: 9

RE: Rx antennas: can I do this? - 12/8/2007 5:15:58 PM   
H5606


 

Posts: 82
Joined: 7/17/2006
From: , MD, USA
Status: offline 		Thank you all for the replies.

dki

(in reply to js3)
       Post #: 10

RE: Rx antennas: can I do this? - 12/9/2007 2:45:55 AM   
micagreenmachin


 

Posts: 131
Joined: 3/11/2003
From: Mundelein, IL, USA
Status: offline 		Ditto. Don't cross the wires... I've never had a problem coiling like that. Do a really good range check and call it a day.

As long as you get a good range check you should be fine.

_____________________________

Everytime you take-off, at some point you're gonna have to land...

(in reply to H5606)
       Post #: 11

RE: Rx antennas: can I do this? - 12/9/2007 10:36:19 PM   
mikegordon10


 

Posts: 199
Joined: 7/12/2003
From: Provo, UT, USA
Status: offline 		I've been doing it like in the photo for quite a few years in 1/2 A Pylon Racers without any problems. JR 610M RX.

Attachments
Click to see fullsize image.
Click for fullsize


_____________________________

Mike Gordon AMA 320990
RC Pylon Racing, the ultimate thrill, when sex and drugs just ain''t enough.

(in reply to Ed Smith)
       Post #: 12

RE: Rx antennas: can I do this? - 12/16/2007 2:21:37 AM   
chashint


 

Posts: 902
Joined: 1/1/2002
From: Rowlett, TX, USA
Status: offline
quote:

ORIGINAL: H5606
The receiver in the picture is a Hitec 555 that I've been flying in that configuration without difficulty for several years. The coil is stacked and at no point does the antenna cross over itself. I was wondering if anybody had done the same with a Futaba Rx and had similar success.


I have to ask why you would think a Futaba RX might behave differently than the Hitec in regards to coiling the antenna ??
As far as decent range goes ..... what do you consider decent range ??


_____________________________

regards,
Charlie

(in reply to H5606)
       Post #: 13

RE: Rx antennas: can I do this? - 12/16/2007 5:33:27 PM   
H5606


 

Posts: 82
Joined: 7/17/2006
From: , MD, USA
Status: offline
quote:

ORIGINAL: chashint


quote:

ORIGINAL: H5606
The receiver in the picture is a Hitec 555 that I've been flying in that configuration without difficulty for several years. The coil is stacked and at no point does the antenna cross over itself. I was wondering if anybody had done the same with a Futaba Rx and had similar success.


I have to ask why you would think a Futaba RX might behave differently than the Hitec in regards to coiling the antenna ??
As far as decent range goes ..... what do you consider decent range ??



I'm not well versed in radio theory; I just know what you're supposed/not supposed to do. I was shown this technique by my peers. I've only coiled the antenna like this on a GWS receiver and that Hitec shown in the picture and was surprised that there did not seem to be any degredation in range. The GWS receiver was on a Pico-Stick flown indoors and outdoors. The Hitec receiver is in a .25 size combat profile design. I am not too emotionally tied to either airplane however I would like to continue using this technique on more elaborate projects with Futaba receivers as I hate to have "excess" antenna length trailing along behind the aircraft.

Poor choice of words on my part -- "decent range" should have been "no change in range" or as long as the model can be seen.

(in reply to chashint)
       Post #: 14

RE: Rx antennas: can I do this? - 12/16/2007 5:41:20 PM   
quepasa


 

Posts: 211
Joined: 2/2/2007
From: Golden Valley, AZ, USA
Status: offline 		Anytime you coil wire induction happens! Unless the coils are spaced far enough apart, (how far I don't know) it will change the electrical length of the wire. (resistance) This changes the "tuning" of a reciever. It's the wave-length/electrical-length of the antenna that is critical to the tuning of the reciever. Crossing the coils probably wouldn't make much differance as its still going to be out of tune, though probably not as much. SWR (standing wave reflected) on a transmitter is critical. Thats why some trans. antennas are longer than others. Recievers are "tuned" to a specific frequency and the antennas electrical length is part of it. Change the electrical length with wire cutters or any type of coil, and ya change the frequency. This can't be a good thing even if it works close in! It will cut down on the range. How much depends on how far off frequency it is in a reciever, or how much of the signal is reflected back into the transmitter. Any of ya into amateur radio, or CB will tell ya that 1/4" of antenna length will change everything in recieving or transmitting. A wad (not a coil) of antenna wire inside of the fuse. with a little strung outside is WAY better than any kinda coil. Thats why that "whip" is the best alternative, when the rest of the antenna is waded-up in a hap-hazzard fassion inside the fuse. No coil, no cut! JMO. Q.

Edit; a "wad" of wire ain't a "coil", and does not change the electrical length of the wire. IF the "whip" has a load-coil then the reciever can be fooled to think the overall length is correct because the electrical length is correct due to induction in the coil.
My point is...wad it up inside, pull some out to fit the model and forget it.

< Message edited by quepasa -- 12/16/2007 5:57:50 PM >

_____________________________

"If ya think that was somethin, hold my beer and watch this!"

(in reply to chashint)
       Post #: 15

RE: Rx antennas: can I do this? - 12/16/2007 6:11:22 PM   
<