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Old Apr 02, 2013, 01:50 PM
RC beginner
New York
Joined Oct 2008
6,054 Posts
Mini-HowTo
extending range of small quad/heli radios

due to several recent pm requests for this, prompted by mention in another post, i figured good idea to start a new thread instead of answering same questiones again and again. for my wlt radio i got almost 1.5km (8x range increase) with the simple mods described here.

first thing i noticed when opening the case was the stock antenna was bent over double which could not be good. straightening it out more than doubled range. im not sure how many suffer from this but all the $8 v911 tx from tmart were like that. at least it had a real antenna. some of the newer "toys" with tiny pcb antenna may also benefit from similar mods.

anyway big improvement but not quite enough because, in addition to v911 helis and v939 quads, this was being used for planes which can go much farther. so next step was to almost double range again by effectively converting the monopole to a dipole and improving orientation as shown in the first photo. there are two ways to do it:

1. tack on a 1.5" pieces of wire to the shield where exposed part starts. the trick is to avoid melting the plastic insulator when soldering on the new wire. one secret is to work FAST and also use a tiny alligator clip as a heat sink.

2. strip off 1.5" of outer insulation, loosen the braid, then pull the center conductor through at the beginning of the exposed part. its harder to get a tight 't' this way because the center insulator is stiff but can be done with a little heat.

in both cases toss the plastic antenna shell. and notice a glob of silicone can be used at the junction to keep the 't' shape better. legs start out 1.5" long and then cut down til range/rssi starts dropping. the length is not that critical imo. one big benefit was not only the dipole configuration but being able to orient the antenna vertically when held in your hand as opposed to the original which almost always points right at the model. worst possible position.



a similar trick at the rx will now get us over 4x the original range:



if theres interest i will continue with a description of how i doubled again by adding another piece of wire. no photos but if requested ill take some and post. let me know.
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Last edited by dave1993; Apr 02, 2013 at 02:35 PM. Reason: rx photo
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Old Apr 02, 2013, 02:01 PM
RC beginner
New York
Joined Oct 2008
6,054 Posts
Quote:
Originally Posted by SeByDocKy
Hi,

I am very interested by your simple mod, i.e. use a real dipole instead of the basic wire. I want also to apply your mod to an 911 TX. Got some questions:

For the TX

1) what is the exact length of the dipole ?
2) Which material did you used
3) Did you solder the original wire to the center of this dipole ?
4) How are you holding straight this new antenna ? with a piece of plastic ?

To add a new antenna for the V911 birds, it would probably to heavy isn'it ?
dipole legs ended up a little over an inch long. imo not that critical.

depending on which of the above methods material was just any piece of stranded wire or original antenna material. or a completely new one built from thin 50ohm coax. i got many feet attached to cheapo ebay notebook j-pole antennas for a buck or so.

one wire is connected to center conductor, the other leg to the shield.

self supported and holds its shape surprisingly well. even if distorted easy to bend back. virtually impossible to damage.

very light and added almost no weight to my v911s and v939s.
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Last edited by dave1993; Apr 02, 2013 at 02:39 PM. Reason: speling
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Old Apr 04, 2013, 12:20 PM
RC beginner
New York
Joined Oct 2008
6,054 Posts
if you dont mind ill reply here. better to post than pm because i dont check there very often overflow issues and also others can benefit:

Quote:
Originally Posted by Cheese5
Quote:
Originally Posted by dave1993
probably from this thread?http://www.rcgroups.com/forums/showt...l#post24246253

im not sure about v949 but for my v911 radio i got almost 10 times that. sounds like theres something else wrong. i just made the legs 1.5" long and started cutting down til range/rssi started dropping. the length is not that critical imo.

did you try converting the rx to dipole too? the biggest problem people run into is bad antenna connection and adding a new one sometimes reveals that. good luck.
Ah so your tx is different than mine. I suspect its the TX since the board says 20dBm (~100mw) but in reality it has less range than my DX6i in range check mode!

How would you convert the RX antenna to a dipole? Since it has no ground to solder to where would the other element be? Right on the RX side there is a 1/4 wavelength wire soldered to it.

In the future I will buy a booster for this, since for FPV 50m is far too short, but that booster (sunhans) will take a month or 2 to arrive, so I'm trying to see if there is any way to extend the range a bit during the long wait.
im not a huge fan of boosters but there seems to be something seriously wrong with your radio. stock v911, v929, v939 go much further than that. id suggest getting a replacement from banggood or tmart. they are very cheap. and hopefully the pics and description above will help.
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Old Apr 04, 2013, 11:06 PM
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This is what I have right now:

The TX antenna is a 1/2 wavelength dipole, one element soldered to the shielding, while the other one is the original monopole material. The RX antenna is a 1/4 wavelength wire, I don't understand how you solder to the shielding when there is none on the board??

Also the range I'm measuring is from the TX on the ground with the quad on the ground, worse range testable. That way I know i can go farther in the air. I'll see how far it goes before cutting off in the air this weekend. Hopefully a lot more than 50m!!
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Old Apr 05, 2013, 01:35 PM
RC beginner
New York
Joined Oct 2008
6,054 Posts
tests on several stock wlt helis and quads show about 350-400 long paces (meters). not on the ground but held up in the air away from our bodies. anything worse than that indicates a problem. usually coax disconnected or shorted at pcb. that improves with mods as described above.

of course a lot depends on the noise floor but my tests are usually in suburban soccer field which aint the quietest palce on earth.
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Old Apr 05, 2013, 05:13 PM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,698 Posts
Dave,
Nice Consider this an interested request for your doubled range doubling
Thanks and Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index
Quote:
Originally Posted by dave1993 View Post
due to several recent pm requests for this, prompted by mention in another post, i figured good idea to start a new thread instead of answering same questiones again and again. for my wlt radio i got almost 1.5km (8x range increase) with the simple mods described here.

first thing i noticed when opening the case was the stock antenna was bent over double which could not be good. straightening it out more than doubled range. im not sure how many suffer from this but all the $8 v911 tx from tmart were like that. at least it had a real antenna. some of the newer "toys" with tiny pcb antenna may also benefit from similar mods.

anyway big improvement but not quite enough because, in addition to v911 helis and v939 quads, this was being used for planes which can go much farther. so next step was to almost double range again by effectively converting the monopole to a dipole and improving orientation as shown in the first photo. there are two ways to do it:

1. tack on a 1.5" pieces of wire to the shield where exposed part starts. the trick is to avoid melting the plastic insulator when soldering on the new wire. one secret is to work FAST and also use a tiny alligator clip as a heat sink.

2. strip off 1.5" of outer insulation, loosen the braid, then pull the center conductor through at the beginning of the exposed part. its harder to get a tight 't' this way because the center insulator is stiff but can be done with a little heat.

in both cases toss the plastic antenna shell. and notice a glob of silicone can be used at the junction to keep the 't' shape better. legs start out 1.5" long and then cut down til range/rssi starts dropping. the length is not that critical imo. one big benefit was not only the dipole configuration but being able to orient the antenna vertically when held in your hand as opposed to the original which almost always points right at the model. worst possible position.



a similar trick at the rx will now get us over 4x the original range:



if theres interest i will continue with a description of how i doubled again by adding another piece of wire. no photos but if requested ill take some and post. let me know.
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Old Apr 05, 2013, 05:40 PM
RC beginner
New York
Joined Oct 2008
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will do jim. its as simple as converting to yagi by glueing wire onto the coax insulation. no soldering. not quite double but almost. ill take a few pics when i get a chance.
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Old Apr 13, 2013, 04:41 AM
Sopwith Camel's Cousin
Between my tx and crashed aircraft
Joined Mar 2006
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Quote:
Originally Posted by dave1993 View Post
will do jim. its as simple as converting to yagi by glueing wire onto the coax insulation. no soldering. not quite double but almost. ill take a few pics when i get a chance.
Just read a little about yagi's.
Is this added wire a reflector that is about 1/2 wavelength long and about 1/4 wavelength behind the dipole antenna: so about 3 inches long and placed about 1.5 inches behind the dipole?

Thanks!
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Old Apr 13, 2013, 04:46 AM
Sopwith Camel's Cousin
Between my tx and crashed aircraft
Joined Mar 2006
3,803 Posts
.
Quote:
Originally Posted by Cheese5 View Post
This is what I have right now:

The TX antenna is a 1/2 wavelength dipole, one element soldered to the shielding, while the other one is the original monopole material. The RX antenna is a 1/4 wavelength wire, I don't understand how you solder to the shielding when there is none on the board??
...
From what I know of antennas, one guess is then when there is no shielding, electrically connect the other 1/4 wavelength wire to ground (what the shielding would be electrically connected to, if there were any shielding).
From what I know of RC rx's, ground tends to be the connection to the negative battery terminal.

Side note: the term "ground" is kind of funny when talking about a receiver that is flying through the air and not really in electrical contact with actual ground (until it lands or crashes ).
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Last edited by flying-llama; Apr 13, 2013 at 05:08 AM. Reason: The term "ground"
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Old Apr 13, 2013, 08:48 PM
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United States, CA
Joined Jul 2010
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Hmm that would be a bit tricky to hook up on the RX side. Just did a range test without FPV equitment, the quad can go as far as I can see orientation without losing link (about 150m). Looking good so far, I'm still waiting for my FPV TX to come to test the FPV range.
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Old Apr 15, 2013, 12:13 PM
RC beginner
New York
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Quote:
Originally Posted by flying-llama View Post
.
From what I know of antennas, one guess is then when there is no shielding, electrically connect the other 1/4 wavelength wire to ground
if you refer to the reflector centerpoint actually it dont matter whether you ground or not. voltage and current waves cancel there resulting in zero power. i just glue it on the coax with a glob of silly-cone. for director a skinny piece of bamboo serves but that is probably not needed and the radiation pattern does get a bit narrow. wasnt a problem for me but anyway ive removed the reflector on mine (accidently, not on purpose). range is still way beyond los for these tiny planes and copters so it dont really matter.

i will take some pictures when my diy flysky rx project calms down.
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Old Apr 15, 2013, 07:47 PM
Sopwith Camel's Cousin
Between my tx and crashed aircraft
Joined Mar 2006
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Quote:
Originally Posted by dave1993 View Post
Quote:
Originally Posted by flying-llama View Post
.
From what I know of antennas, one guess is then when there is no shielding, electrically connect the other 1/4 wavelength wire to ground
if you refer to the reflector centerpoint actually it dont matter whether you ground or not. ...
My other reply was about a reflector.

But in this reply, I am referring to the added 1/2 of a dipole (your monpole to dipole conversion) that you electrically connect to the shielding (ground).
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Old Apr 15, 2013, 08:05 PM
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Quote:
Originally Posted by dave1993 View Post
if you refer to the reflector centerpoint actually it dont matter whether you ground or not. voltage and current waves cancel there resulting in zero power. i just glue it on the coax with a glob of silly-cone. for director a skinny piece of bamboo serves but that is probably not needed and the radiation pattern does get a bit narrow. wasnt a problem for me but anyway ive removed the reflector on mine (accidently, not on purpose). range is still way beyond los for these tiny planes and copters so it dont really matter.

i will take some pictures when my diy flysky rx project calms down.
So I'll just glue another wire onto the monopole on the quad to make it a dipole?
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Old Apr 15, 2013, 08:40 PM
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New York
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nope. as lama said his first post about yagi was confiused with his second regarding dipole. to make a dipole you SOLDER another wire equal in size to the shield where exposed part of original wire comes out. look at my pic. its pretty clear. for yagi reflector you just glue another wire equal to these two in length to the coax behind the dipole.
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Old Apr 15, 2013, 09:01 PM
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Originally Posted by dave1993 View Post
nope. as lama said his first post about yagi was confiused with his second regarding dipole. to make a dipole you SOLDER another wire equal in size to the shield where exposed part of original wire comes out. look at my pic. its pretty clear. for yagi reflector you just glue another wire equal to these two in length to the coax behind the dipole.
Yes that's what I have on my TX, I was talking about the dipole for RX (on the quad) since it has no shield on the antenna joint. Going to make a yagi for TX soon after getting my FPV TX.
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