Need help on building a quad

Gyro Doctor

Gyro Doctor

Electronics Tech for over 45 years
:rolleyes: ... Even further yet thoughts on antenna making:

Now that I've touched upon the PHYSICAL and ELECTRICAL aspects of constructing antennas it occurs to me there's been no mention of tuning,
aside from my brief comment earlier advising the need to do so.

There's two important aspects to consider: Impedance Matching and VSWR

Impedance matching increases the efficiency of an antenna by allowing the best transfer of energy throughout the elements without creating
unnecessary losses. This can be done by a variety of methods including Hecker transformers, coax "stubs", microstrips, tapers, and (my favorite)
wave traps. :cool:

Lowered VSWR (voltage standing wave ratio) increases the efficiency by allowing the energy to completely pass to the radiating elements rather
than being reflected back to the source. If too much energy gets reflected back from an antenna into a transmitter it can damage it (I made good
money in the 70's, when CB radios were the rage, tuning antennas and repairing "blown finals" on radios that transmitted into bad or missing antennas)
as can be seen when your VTX antenna gets damaged or loosened and you hafta buy another VTX. ;)
SWR (or VSWR) adjustments are a function of both the antenna's radiating elements relationship to the frequency (simply the length in a simple "whip"
or dipole antenna) AND the position of the impedance matching element around the first quarter turn in helical antennas.

I'm not even going to get into how to DO these things, just pointing out that there's more to antennas than just following a pattern and soldering something together if you really want to get optimal results. I commend those, like Moz, who endeavour to experiment with antenna making, as it is almost an art unto
it's self. :)

(microwave communications technician for seven years @ Metropole Products Inc.) :p
 
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Gyro Doctor

Gyro Doctor

Electronics Tech for over 45 years
mozquito1 said:
Done all that making my own stuff.
They work but not as good as factory made.
Click to expand...

Moz, you should raise that bottom coil a couple of millimeters higher up off the reflector. About the last 1/4 turn or so of it is elevated.
You shouldn't need any tape to keep the end of it from touching because, as it is, what you've done there is you've basically made a capacitor.
Try that and I'll bet it helps. ;)
 
Syntax_Err

Syntax_Err

Member
TBH, this whole antenna subject should get it's own category here, or at least a thread.
I didn't know how much was under the hood till now.
 
mozquito1

mozquito1

Well-Known Member
The tolerance for the antenna pictured of the coil & connecting signal pin was 0.4mm, hence the tape is 0.4mm thick.
The tape was removed. It's a 5 turn with no wave trap. Not precise in its range
(God knows what it's shape is.
but works on most bands at a good enough range.
 
Gyro Doctor

Gyro Doctor

Electronics Tech for over 45 years
:rolleyes: ... Every heli I've ever seen kept the last quarter turn at least 2mm off the ground plane, this makes for what amounts to an air core capacitor for tuning.
Tape acts differently than air (it's called the dielectric property) so the spacing to achieve the same value changes when you use anything besides air and that value
depends on the material. So if you're sure that's the way it's supposed to be built then I'd leave the tape in, otherwise the value will get messed up and detune the antenna,
just never seen it done like that before.
 
mozquito1

mozquito1

Well-Known Member
I did say the tape was removed.
And the blueprint says 0.4mm space. PhotoPictureResizer_170812_231537619-1024x768.jpg
Sorry I cannot find the other picture with the list on but J = 0.4mm.
The wave trap is just a tiny copper triangle cut to size & solderd on the tip.
I opted for no wave trap as if you get it wrong, it's miles out. The option I took was the easy one & probably the least effective. The other one I made is not very good. It's arc is about 100 degrees.
Tried on its own & can't pick anything up behind. Flying away there is a noticeable tube shape of better reception.
Which runs out about 200m.
Done right like the 2nd one it will probably pickup alot more channels either side of the 5800.
 
Spork

Spork

There is no spoon
Thanks for the discussion on antenna stuff.

@Gyro Doctor (or others) is there a book you would recommend that is a good basic introduction to antenna design. Not looking for PhD level stuff, but I'd like to upgrade my basic knowledge I learned from studying for the HAM test, which is just some basic safety information, the 1:1 impedance match, and not much else. My biggest interest (for now) is a lot better understanding of the stuff I might come across related to quads - so the 2.4/5.8 Ghz stuff down to the popular frequencies used for longer range (in the hundreds of Mhz range).
 
Gyro Doctor

Gyro Doctor

Electronics Tech for over 45 years
Spork said:
is there a book you would recommend that is a good basic introduction to antenna design.
Click to expand...

Bruce on "RC Model Reviews" channel for YouTube is a wealth of information and has several videos about antennas.
There's also "Mr. Steel" videos (but those are mostly quad builds) as well as any of Joshua Bardwell's videos (he gets more technical than most others) that I enjoy.
Oscar Liang is another noteworthy source of information for just about anything to do with quads. I like videos because "a picture is worth a thousand words".
Otherwise I just resort to my old college textbooks. :p
 
Spork

Spork

There is no spoon
Gyro Doctor said:
Bruce on "RC Model Reviews" channel for YouTube is a wealth of information and has several videos about antennas.
There's also "Mr. Steel" videos (but those are mostly quad builds) as well as any of Joshua Bardwell's videos (he gets more technical than most others) that I enjoy.
Oscar Liang is another noteworthy source of information for just about anything to do with quads. I like videos because "a picture is worth a thousand words".
Otherwise I just resort to my old college textbooks. :p
Click to expand...

Awesome, thanks. I'm already a fan of Bruce and Mr. Steel - just haven't had a chance to go through all their videos yet. Hadn't heard of Joshua and Oscar before - so I'll check their channels out as well.
 
Spork

Spork

There is no spoon
Yeah, I've learned a lot already from both Bruce and the Painless360 guy. If I ever wanted to catch up on all their videos it might take me a year.
 
mozquito1

mozquito1

Well-Known Member
Spork said:
Totally agree, but sometimes I still prefer a book (esp kindle, etc) over a video because it's easier to search and skip ahead.
Click to expand...
Github is a good place for knowledge
If your running betaflight then you must have it bookmarked. Or you should have its where you download blheli configuration tool also.
 
Spork

Spork

There is no spoon
mozquito1 said:
Github is a good place for knowledge
If your running betaflight then you must have it bookmarked. Or you should have its where you download blheli configuration tool also.
Click to expand...

Also good to know, thanks Moz. I'm a software guy, so I spend plenty of time on GitHub - but rarely think about it for things outside of "code" reasons. Makes sense to find it there since it's open source. I'll have to remember to search there for other things as well.
 
mozquito1

mozquito1

Well-Known Member
Alot of ppl doing first builds tend to buy cheap boards like a naze32 or Cc3d.
This is the one are you shouldn't scrimp on. These 2 boards are by far the worst for failing. Just buy the cheapest F3 if money is an object.
 
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