HobbyKing.com New Products Flash Sale
Reply
Thread Tools
This thread is privately moderated by IBCrazy, who may elect to delete unwanted replies.
Old May 05, 2012, 02:58 PM
"FPV"er not a "LOS"er
Wettfeat's Avatar
United States, NC, Charlotte
Joined Feb 2012
360 Posts
I'm not exactly sure how you would go about doing that. Maybe brass tubing or copper tubing?
Wettfeat is offline Find More Posts by Wettfeat
Reply With Quote
Sign up now
to remove ads between posts
Old May 05, 2012, 03:21 PM
Registered User
United States, NC, Wilmington
Joined Aug 2011
767 Posts
Quote:
Originally Posted by Wettfeat View Post
Whichever you choose though make sure your RX antenna is the same length.
Never heard this before. Where did you read or hear that?

The mod only needs to be done to the receiver from all that I have learned.

Go to this page and scroll to the bottom. It gives a great calculator to figure the length of you antenna. Just input your frequency.

http://team-blacksheep.com/article/page:20


Marc
MASHTON is offline Find More Posts by MASHTON
Reply With Quote
Old May 05, 2012, 03:24 PM
Registered User
JLT_GTI's Avatar
Oviedo
Joined Jun 2010
2,285 Posts
Quote:
Originally Posted by jwbalder View Post
New information for me, rx antenna same length! Good to know, both wires the same lenght or together? How do I make a 4 meter antenna for 35 mhz ?
Making a long Rx antenna is easy.. just buy 4m of antenna wire and either solder it to the end of the existing one (so the total incluiding the original one is the wanted lenght) or put a connector..

some guys put a servo conetor to the end of the original and the other in the enlarged wire so it can be plugged and unplugged easily and also to disconect in case the long antenna gets stucked in something at landing so it doesnt get riped off from the Rx


Still making the Tx antenna longer is not an option for me as it has the telescopic antenna
JLT_GTI is offline Find More Posts by JLT_GTI
RCG Plus Member
Latest blog entry: CL-415 GuanLi
Reply With Quote
Old May 05, 2012, 03:51 PM
Wallop!
Martin7182's Avatar
Bussum, Netherlands
Joined Oct 2009
743 Posts
Quote:
Originally Posted by MASHTON View Post
Never heard this before. Where did you read or hear that?

The mod only needs to be done to the receiver from all that I have learned.

Go to this page and scroll to the bottom. It gives a great calculator to figure the length of you antenna. Just input your frequency.

http://team-blacksheep.com/article/page:20

Marc
Ehh sorry but shouldn't you compensate for the lower electrons speed in metal wires?
The calculator seems to use the plain speed of light, so lengths are about 5% off.

Martin
Martin7182 is offline Find More Posts by Martin7182
Reply With Quote
Old May 05, 2012, 05:41 PM
Registered User
Joined Feb 2012
16 Posts
Quote:
Originally Posted by JLT_GTI View Post
Making a long Rx antenna is easy.. just buy 4m of antenna wire and either solder it to the end of the existing one (so the total incluiding the original one is the wanted lenght) or put a connector..

some guys put a servo conetor to the end of the original and the other in the enlarged wire so it can be plugged and unplugged easily and also to disconect in case the long antenna gets stucked in something at landing so it doesnt get riped off from the Rx


Still making the Tx antenna longer is not an option for me as it has the telescopic antenna
Thanks again! So with 35 mhz you never make your tx antenna longer. I thought that was the whole deal. So I only need to increase lenght of antenna of receiver! Thanks!
jwbalder is offline Find More Posts by jwbalder
Reply With Quote
Old May 05, 2012, 06:28 PM
Registered User
United States, NC, Wilmington
Joined Aug 2011
767 Posts
Quote:
Originally Posted by Martin. View Post
Ehh sorry but shouldn't you compensate for the lower electrons speed in metal wires?
The calculator seems to use the plain speed of light, so lengths are about 5% off.

Martin
Don't know for sure I am not an RF engineer and I didn't write the formula used in the calculator. What I do know is there are plenty of people using that calculator for 72 and 35MHz with great success. 5% probably translates to ~1.2:1 SWR versus 1:1 and that is close enough to work quite well. Heck 1.6:1 is considered very good so even at that you have a well matched antenna.

Marc
MASHTON is offline Find More Posts by MASHTON
Reply With Quote
Old May 06, 2012, 01:29 AM
Registered User
JLT_GTI's Avatar
Oviedo
Joined Jun 2010
2,285 Posts
Quote:
Originally Posted by jwbalder View Post
Thanks again! So with 35 mhz you never make your tx antenna longer. I thought that was the whole deal. So I only need to increase lenght of antenna of receiver! Thanks!
Well dont use my words as total information....im about to begin with FPV and havent yet enlarged my own antenna or tried..


I tried with the stock antenna (both Tx and Rx) and i had control at 4kms with a whole city between and radio antennas nearby.. as far as i have readed until now only enlarging the Rx wire, but dont know about swaping the Tx antenna
JLT_GTI is offline Find More Posts by JLT_GTI
RCG Plus Member
Latest blog entry: CL-415 GuanLi
Reply With Quote
Old May 06, 2012, 05:08 AM
Wallop!
Martin7182's Avatar
Bussum, Netherlands
Joined Oct 2009
743 Posts
Quote:
Originally Posted by MASHTON View Post
Don't know for sure I am not an RF engineer and I didn't write the formula used in the calculator. What I do know is there are plenty of people using that calculator for 72 and 35MHz with great success. 5% probably translates to ~1.2:1 SWR versus 1:1 and that is close enough to work quite well. Heck 1.6:1 is considered very good so even at that you have a well matched antenna.

Marc
Marc, the calculator just divides the speed of light in vacuum by the frequency, so:

299792458 / f

For 35Mhz this yields 4.28m for a half wavelength. You better multiply that length by 0.95 for your practical wire.

Why not pursue a better system by using a better formula? I think among equally easy solutions you should always choose the best one. It even costs less material . But anyway, VSWR 1:1 cannot be obtained as a half wave whip antenna has impedance mismatch. So without a matching network in between you'll always have some losses. Also I think most receivers extend the antenna length electrically so that a shorter wire can be used that still behaves like a 1/4 wavelength antenna. My 35Mhz antennas are about 1 meter long, so that's 1/8 wavelength, probably electrically lengthened to 1/4 length. I don't know what the effect is if you change the wire to 1/2 wavelength.

As we're talking about receivers only, a high VSWR will not damage anything. It only has bad efficiency. Maybe you should just try it and do a range check.

Martin
Martin7182 is offline Find More Posts by Martin7182
Reply With Quote
Old May 06, 2012, 07:06 AM
"FPV"er not a "LOS"er
Wettfeat's Avatar
United States, NC, Charlotte
Joined Feb 2012
360 Posts
I've heard of people on 72mhz making half-wave antenna's for their tx's but just increasing the rx's antenna length would give you extra range as well. All this is totally optional, you don't even have to do it if you are only flying 3-4km away. After that you are better off to buy an LRS anyways.
Wettfeat is offline Find More Posts by Wettfeat
Reply With Quote
Old May 06, 2012, 11:59 PM
Registered User
Canada, BC, Vancouver
Joined Feb 2012
652 Posts
was out today for my 5th Fpv flight. Awesome i went 2km no problems, im running http://hobbywireless.com/index.php?m...roducts_id=566
and have changed out the stock whip on the Tx with a 3dbi omni, its a little big tho i think in size... any ways, the range im getting with my setup is satisfying for me but what id also like to do is have better 1km range around trees and other objects, What will i b looking at to say fly behind a house for some shots or come over some trees for a rip down the fairway behind my house, what kind of antennas will i b needing for some penetration? Blubeams, Omnis the ol YAgi?
Thanks guys
elliott000 is offline Find More Posts by elliott000
Reply With Quote
Old May 07, 2012, 01:07 AM
Registered User
FL
Joined Jul 1999
457 Posts
I watched the videos on the first page and it sounds to me like this is a good place to get some FPV help.
I have done a little flying FPV about 15 years ago and in fact still have the systems I used then. They are large when looking at the systems of today.
SO, I will start fresh.
I have airplanes and a quad that I could put a system on. I fly using 2.4. (9503X radio)

I am looking for a complete system that will offer about a 1 mile range as I would not see me flying out more than that.

It would be great if there is a turn key system I could buy and maybe upgrade a part or two to meet my needs.

I look forward to hearing what is out there and where to get it.

Thanks,
Troy
testfly is online now Find More Posts by testfly
Reply With Quote
Old May 07, 2012, 01:10 AM
I need a bigger shed..
sammyc's Avatar
Australia, TAS, Launceston
Joined Nov 2011
1,498 Posts
Who can comment with ANYTHING to do with FPV on a conventional helicopter (T-REX 450)?
I have been learning to fly helicopters, and the bug have bitten me very badly! So badly I have given myself no time for FPV with my bixler!
I know im a long way from FPV'n a 450, but am very interested!
sammyc is offline Find More Posts by sammyc
Reply With Quote
Old May 07, 2012, 01:36 AM
"FPV"er not a "LOS"er
Wettfeat's Avatar
United States, NC, Charlotte
Joined Feb 2012
360 Posts
Quote:
Originally Posted by elliott000 View Post
was out today for my 5th Fpv flight. Awesome i went 2km no problems, im running http://hobbywireless.com/index.php?m...roducts_id=566
and have changed out the stock whip on the Tx with a 3dbi omni, its a little big tho i think in size... any ways, the range im getting with my setup is satisfying for me but what id also like to do is have better 1km range around trees and other objects, What will i b looking at to say fly behind a house for some shots or come over some trees for a rip down the fairway behind my house, what kind of antennas will i b needing for some penetration? Blubeams, Omnis the ol YAgi?
Thanks guys
I've heard circular polarized antenna's do well for stuff like that. IB Crazy has a thread for them.
Wettfeat is offline Find More Posts by Wettfeat
Reply With Quote
Old May 07, 2012, 05:21 AM
Registered User
Joined May 2012
4 Posts
Need Advice Please

Moved my question to the main thread. Not sure if I posted it here correctly. Thanks.
and444 is offline Find More Posts by and444
Last edited by and444; May 07, 2012 at 07:13 PM. Reason: Not sure if posted in the right thread.
Reply With Quote
Old May 07, 2012, 05:45 AM
Registered User
JLT_GTI's Avatar
Oviedo
Joined Jun 2010
2,285 Posts
Any pics or hints on where and how put 2 to 4m of antenna in a 2m plane
JLT_GTI is offline Find More Posts by JLT_GTI
RCG Plus Member
Latest blog entry: CL-415 GuanLi
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion How to calculate flight time - guide ikorman Multirotor Talk 11 Dec 30, 2011 07:22 PM
Discussion How many FPV pilots in the world? rbmaze FPV Talk 10 Aug 03, 2011 06:16 AM
Poll Would you be interested in buying Ready to Fly FPV airplanes from a new FPV store? FPVNOW FPV Aircraft 36 Oct 06, 2010 08:56 PM
Discussion Can this cam be used for FPV ? SpookiePower FPV Talk 8 Sep 12, 2010 07:12 AM
Cool How cool would this be for FPV Kai_Shiden FPV Talk 2 May 11, 2009 07:41 PM