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Old Nov 09, 2012, 09:24 AM
Registered User
United Kingdom, England, Herefordshire
Joined Oct 2012
195 Posts
Grounding shield?

Hi All,

Firstly, thank you for the guide! Amazing work for everyone

I've just built a cloverleaf and a skew planar for 1280Mhz (see image attached, I used some wire that was really thick!! Is 2mm Diameter too thick? I got it out of some cable thats meant to wire up your house)

My understanding was..

1. Signal wire (core) attaches to the top side of all the ends
2. The copper is then bent to shape
3. The bottom of the copper attaches to the SHIELD of the signal cable
4. The shield connects to ground

My question is, is it meant to attach to ground? All my electronics says that attaching to ground is shorting it out, would it not be better with a filter capacitor to ground?

The original antenna on my system did not contact ground, only the shielding..

I have looked all over internet but no one mentions about this grounding.. My cheap transmitter i don't think is powerful enough to overcome this (see the image, its that tiny tiny green square attached to the antenna)

Video works and it does transmit, but not very far, and I get interference when it is tilted.. to be honest i'm not even sure what frequency my transmitter/receiver is! It has an analogue tuning dial..

Thanks! G
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Old Nov 09, 2012, 09:35 AM
Registered FPVer :)
markus123456's Avatar
Switzerland, LU, Buchrain
Joined Aug 2006
2,819 Posts
Quote:
Originally Posted by geebles View Post
Hi All,

Firstly, thank you for the guide! Amazing work for everyone

I've just built a cloverleaf and a skew planar for 1280Mhz (see image attached, I used some wire that was really thick!! Is 2mm Diameter too thick? I got it out of some cable thats meant to wire up your house)

My understanding was..

1. Signal wire (core) attaches to the top side of all the ends
2. The copper is then bent to shape
3. The bottom of the copper attaches to the SHIELD of the signal cable
4. The shield connects to ground

My question is, is it meant to attach to ground? All my electronics says that attaching to ground is shorting it out, would it not be better with a filter capacitor to ground?

The original antenna on my system did not contact ground, only the shielding..

I have looked all over internet but no one mentions about this grounding.. My cheap transmitter i don't think is powerful enough to overcome this (see the image, its that tiny tiny green square attached to the antenna)

Video works and it does transmit, but not very far, and I get interference when it is tilted.. to be honest i'm not even sure what frequency my transmitter/receiver is! It has an analogue tuning dial..

Thanks! G
What at DC levels looks like a short is not a short in the HF domain. Your antennas are built correctly as it seems.

HTH

Markus
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Old Nov 09, 2012, 09:50 AM
Registered User
United Kingdom, England, Herefordshire
Joined Oct 2012
195 Posts
Quote:
Originally Posted by markus123456 View Post
What at DC levels looks like a short is not a short in the HF domain. Your antennas are built correctly as it seems.

HTH

Markus
Thanks for the quick reply, i'm sorry for how silly my post may have sounded! Have learnt something Either way i think i will upgrade transmitter, the Cloverleaf is still a significant improvement open the original one!

Thanks, G
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Old Nov 09, 2012, 01:27 PM
Wallop!
Martin7182's Avatar
Bussum, Netherlands
Joined Oct 2009
740 Posts
Geebles,

Your wire is thick, but not relatively as thick as the wire that many 5.8Ghz CP builders use. And they are successful so I guess it won't harm that much. But it is also heavy. Anyway, if you have significant improvement then that's an important step forward. Maybe next time try thinner wire like piano wire (really tough and strong but a bit hard to straighten out and bend). Others also use welding wire with success, but I never tried that.

Martin
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Old Nov 14, 2012, 11:43 PM
Dreamer
Australia, TAS, Memana
Joined Aug 2004
2,125 Posts
Hi guys,
Been watching the clip on building a base feed cloverleaf
Base-fed Cloverleaf build.mpg (4 min 44 sec)
.
The construction looks pretty straight forward but is a lot different to the details on page 1 of this thread. Is this video the same antenna, and are there measurements/ details for building this one?

Thanks, Mark
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Old Nov 19, 2012, 11:39 PM
Can i get a do-over?!?!
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United States, TN, Clarksville
Joined Nov 2012
98 Posts
Newbie with stupid questions

I have read this front to back and i have yet to find any lengths for the wire to work for 900mhz systems. Did i just miss it, or is it not in this thread? I am new to RC and to FPV, so i really don't want to to ruin anything. I just got the hobbyking 900mhz 100mw system and it is ok, but i want to venture out farther than the stock antennas will allow. Any suggestions? Thank you for your time and help.
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Old Nov 19, 2012, 11:48 PM
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Australia, NSW, Yamba
Joined Oct 2008
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Quote:
Originally Posted by JesterKlown77 View Post
I have read this front to back and i have yet to find any lengths for the wire to work for 900mhz systems. Did i just miss it, or is it not in this thread? I am new to RC and to FPV, so i really don't want to to ruin anything. I just got the hobbyking 900mhz 100mw system and it is ok, but i want to venture out farther than the stock antennas will allow. Any suggestions? Thank you for your time and help.
Look below , from the first page

Cheers
Patrick


Quote:
Originally Posted by IBCrazy View Post
The antenna is made from two lengths of wire. One is twice as long as the other. The lengths can be calculated:

Long Wire length in inches = 24175/f in MHz

Or for you metric folks

Long Wire length in mm = 614035/f in MHz

So for:

910MHz = 26.5"/675mm
1280MHz = 18.9"/479.5mm
2.4GHz = 9.86"/250.5mm
5.8GHz = 4.1/105mm

Short wire length = 12088/f in MHz
Or in metric:
Short wire length in mm = 307022/f in MHz
910MHz = 13.25/338mm
1280MHz = 9.44/240mm
2.4GHz = 4.93/125mm
5.8GHz = 2.08/53mm

Now you need to calculate your quarter wavelength which is simply 1/8 of your wire length.

Quarter wavelength in inches = 3021/f in MHz

Or

Quarter wavelength in mm = 76755/f in MHz

So for:

910MHz = 3.32"/84mm
1280MHz = 2.36"/60mm
2.4GHz = 1.23"/31mm
5.8GHz = .52"/13mm

You may notice this is a little longer than the true electrical quarter wavelength such as that is used in the BiQuad tutorial. Admittedly, I don't know why this is the case, but it appears to work best 1-2% longer than the electrical wavelength, so we'll go with it. Hey, it hit a perfect 1.0 SWR on the first try, so apparently something is right.

-Alex
KJ4RIV
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Old Nov 20, 2012, 12:03 AM
Can i get a do-over?!?!
JesterKlown77's Avatar
United States, TN, Clarksville
Joined Nov 2012
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Quote:
Originally Posted by hpcoolahan View Post
Look below , from the first page

Cheers
Patrick
HOLY CRAP!!! I read that (a couple of days ago) and it flew right over my head!! Now, to get my brain to wrap (or warp) around it!! Thanks for the point... Had i been smarter (or possibly sober when i read it), i would've seen it days ago.
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Old Nov 20, 2012, 12:27 AM
Fatshark Repairs AU/NZ
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Australia, NSW, Yamba
Joined Oct 2008
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Quote:
Originally Posted by JesterKlown77 View Post
HOLY CRAP!!! I read that (a couple of days ago) and it flew right over my head!! Now, to get my brain to wrap (or warp) around it!! Thanks for the point... Had i been smarter (or possibly sober when i read it), i would've seen it days ago.

lol. your welcome
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Old Nov 20, 2012, 03:13 PM
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Lynden, WA
Joined Nov 2000
2,830 Posts
anyone know where to simply buy a set of 5.8g antennas?

Thanks
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Old Nov 20, 2012, 05:55 PM
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United States, ID, Boise
Joined Mar 2012
162 Posts
Quote:
Originally Posted by JohnVH View Post
anyone know where to simply buy a set of 5.8g antennas?

Thanks
Hugo at TrueRC.com would be one of the best out there.
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Old Nov 21, 2012, 11:51 AM
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Amherst, VA
Joined Jun 2006
10,343 Posts
Hugo (True RC) and his "True Wired" antenna set is a great choice. The BluBeams are the original sets. You can find these at Ready Made RC, Hobby Wireless, Future Hobbies, and a several other places.

-Alex
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Old Nov 22, 2012, 01:16 PM
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Lynden, WA
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Thank you!
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Old Nov 22, 2012, 02:08 PM
Can i get a do-over?!?!
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United States, TN, Clarksville
Joined Nov 2012
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I made a pair of these for my modest little FPV setup and WOW!!! The work great!! I know the angles are off and the measurements are not perfect, but they work WAY better than the stockers that came with my system. Thanks, Alex for your hard work and generosity in gifting the ideas and how-to's that make it possible for all of us to do this sort of thing (even on a tight budget). I am so impressed, even with my "hack-job", I might make a couple of your other designs, just to say I tried them. Thanks again.
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Old Nov 23, 2012, 12:42 PM
Mobius Cables... I got em'
chanyote66's Avatar
United States, TN, Oak Ridge
Joined Dec 2011
3,801 Posts
Quote:
Originally Posted by IBCrazy View Post
You can find these at Ready Made RC
Yup... checked there hoping for a Blackfriday special... sort of dissapointed I was hoping to get a 5.8 600mw and a CL set for it for more than 25% off but guess this black friday is not like the rest...

Chris
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