RE: Rx antennas: can I do this?  
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RE: Rx antennas: can I do this? - 12/18/2007 4:01:42 PM   
quepasa


 

Posts: 211
Joined: 2/2/2007
From: Golden Valley, AZ, USA
Status: offline 		JGspeed, Like I said as plain as I could, I'm not telling guys like you that what you are doing won't work!
If you think that antenna length is a minor issue for a layman, then I guess you and I just do not agree.
You can coil yours for whatever reason, and I won't coil mine for any reason. At the least, guys considering doing this will have a little more knowlege of how things work, (induction & how it changes tuning) to help them decide wheather or not they really want to try it.
Thanks for the education in todays RC equipment! Good flying to you! Q.

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RE: Rx antennas: can I do this? - 3/28/2008 1:33:54 AM   
rctrax



Posts: 597
Joined: 5/11/2002
From: Mosinee, WI, USA
Status: offline 		when you consider that the average rx will be efective out to a mile which is wayyyyyyyy beyond eyesite even if you reduce it's effectivness by 50% you are still way beyond effective site range and thereby still have plenty of range to operate at the ranges of most flying sites.

(in reply to JGspeed)
       Post #: 27

RE: Rx antennas: can I do this? - 3/28/2008 2:26:31 AM   
Acs_guitars



Posts: 2055
Joined: 2/22/2004
From: Tulsa, OK, USA
Status: offline 		Back from the dead thread.... I agree that this is not as big of a deal as some make it out to be. The Hitec 555 reciever even comes with a loom on which to coil the wire and the manual says this can be done with little effect on the usable range of the aircraft. It IS, however, important to not cross the wire upon itself, or tie knots in the wire(may cause breaks). Most posters in this thread say they have done this and had no problem, and I have also done this myself with zero issues so I have to say "the proof is in the pudding" ... It was also pounded into my training not to do this, but after buying a few of the 555's, reading the instructions, and trying the coiled length; I now know otherwise for myself. In any case I try to leave as much antenna straight and uncoiled as possible (atlest to the back of the fuse) just as a course of habbit and my training in RC.

< Message edited by Acs_guitars -- 3/28/2008 2:28:45 AM >

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       Post #: 28

RE: Rx antennas: can I do this? - 3/28/2008 3:18:47 AM   
JPMacG


 

Posts: 1173
Joined: 1/2/2002
From: Ivyland, PA, USA
Status: offline 		LOL.... I actually do design antennas for a living. I've been employed in antenna designer for 27 years, and before that, experimenting with ham antennas since I was 16. I have worked on everything from shaped-beam reflectors for communications satellites through land-based electrically small HF antennas.

My bottom line is this... I can't even begin to tell you how much shortening the antenna will reduce your range. There are too may variables to even guess. You have to try it and then range check, range check, range check. Don't assume that buying a commercially made loaded whip is better than just winding your own. Range check them as well. Don't assume that the receiver front end will tolerate a wide variety of impedances, length is length and it takes length to produce voltage. And don't assume RC-CAM's data is infallible. I'm not so sure his experiments are all that clean.

Range check! The best range check is a comparative one where you compare range with a full antenna to that of the shortened antenna.

End of rant.

(in reply to JGspeed)
       Post #: 29

RE: Rx antennas: can I do this? - 3/28/2008 3:37:03 AM   
Acs_guitars



Posts: 2055
Joined: 2/22/2004
From: Tulsa, OK, USA
Status: offline 		This is the best advice of all..... (hope you don't mind the edit of your quote)

quote:

ORIGINAL: JPMacG

My bottom line is this... try it and then range check, range check, range check.... Range check them..... Range check!...... range check....... the shortened antenna.

End of rant.


-- Not to mock or disrespect your knowledge at all, just a good point to drive home.

As I say I have found that it works for me, but this is also on smaller aicraft that the antenna is nearly 2x's the length of the fuselage.

< Message edited by Acs_guitars -- 3/28/2008 3:38:46 AM >

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       Post #: 30

RE: Rx antennas: can I do this? - 3/28/2008 8:35:35 PM   
garys


 

Posts: 755
Joined: 1/31/2002
From: San Diego, CA, USA
Status: offline 		Until switching to 2.4Ghz, I coiled a portion of all my Futaba receivers (did it on 127DF, 148DF, 129DP, 148DP, &149DP receivers) so that they stay within the length of the fuselage on my all pylon racers. I always did range checks and never had any issues on 72Mhz (I never noticed the range being any less with them coiled). However I found that when flying on 35Mhz in Europe, coiling the antenna did show less range. The range was much better on 35Mhz when letting the antenna hang behind the airplane.

Frankly, as many different variables as there are regarding signal strength, ect, it's quite possible that in some installations a coiled antenna can give better range than an improperly set up, fully extended antenna. Just because you "fully extend" an antenna doesn't mean it's going to give the best reception. A lot depends on how/where it's routed in/on the airplane, ect.

< Message edited by garys -- 3/29/2008 6:32:35 AM >

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       Post #: 31

RE: Rx antennas: can I do this? - 5/26/2008 12:39:02 AM   
anuthabubba


 

Posts: 174
Joined: 11/9/2007
From: Transylvania, LA, USA
Status: offline 		I've been sport flying a couple of RC HLGs for nearly 10 years with the JR rec antennas having about half their length coiled around a piece of stiff paper about 3/4" wide by 3" long with slight spacing and a piece of tape in one and the ant wire just wrapped around four fingers and then laid/stuffed in the fuse under the wing saddle in the other. Have been fortunate enough to throw them into some pretty good thermals (15 to 30 min. flts) that have taken them to the (vertical/horizontal) point of having to spin down to regain visual oriention without any perceived lack of control. The antennas are shortened enough to keep the ends inside the rather short tailbooms (1 wood, 1 CF) of these two gliders.

Granted this visual orientation range may not be all that far due to the small (60" span) size of the models but range checks are good and so far there have been no loss of control problems noted.

Have also used the JR base loaded transmitter antennas (~2' long) on glow powered (.40 thru 1.20 size) models (internal/external antennas) with no perceived problems.

Terry in LP

(in reply to garys)
       Post #: 32

RE: Rx antennas: can I do this? - 5/26/2008 2:59:20 AM   
H5606


 

Posts: 82
Joined: 7/17/2006
From: , MD, USA
Status: offline 		I have now coiled the antenna in this (electric) Parkzone T-28 and performed my standard range check which is to walk out at least 50 paces (100') with the collapsed Tx antenna pointed at the tail of the airplane and checked controls with motor off and then motor on. I've been flying this airplane since new (March) with no range problems yet.

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< Message edited by H5606 -- 5/26/2008 10:45:08 PM >

(in reply to anuthabubba)
       Post #: 33

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