(26-Aug-2023, 05:42 PM)Krohsis Wrote: Not sure which analyzer you purchased, but if it is the same I was using during my antenna building here, make sure it is well charged each time you use it.  Once the battery becomes discharged to some degree (around 50%ish) readings can be less accurate.  This can cause you to chase your tail a bit to determine why you are having varied readings when much else is the same.  

Good luck.

Thanks. Extremely good tip i would say and was not aware of it.
I got the Agility Instrument N1201SA 140Mhz-2.7Ghz and also got a proper calibration kit. Will most def take your tip in consideration

Hi fpvapnea,

Thanks for the positive rating; much appreciated.   

Looks like you have got it under control. Thanks for the info.
By the way, do you have a link for the IBCrazy DIY antenna build?

Hi Krohsis,

Good to see your comments.  It has been awhile.
Thanks for the info about the analyzer's battery; didn't know that.

I probably won't (but you never know) work on the Gen 3 antenna build,
however, the Gen 2 looks interesting; when I get back into the game.
Right now, my building and flying are sort of on hold. Ah, but I am 
keeping my hand in the forum.


Later, My Friends,  iFly  

(27-Aug-2023, 12:24 PM)iFly4rotorsHi fpvapnea, Wrote: By the way, do you have a link for the IBCrazy DIY antenna build?

Here you go:

SMA version:


U.FL version:


p.s Another little tip. Had this rotating coax cutter/stripper tool laying around and makes cutting the sheath and or isolation of these different size coaxes a piece of cake. No exacto knife widow maker stuff needed.


Made a smal vid on the method i used it for, to cut and extract the exact length RG142 shield

Not too shabby for 2 tries.
The 1st one i accidentaly made the ground/shielded element too short, but finished it anyway as i did not have my analyser yet.
Then made a second one to the specs for 868Mhz (around 83mm for the RG142 shield ).
Today i got my analyser , calibrated it with the calibration kit, and found out both my builds where duds, but funny enough the short one came much , much closer.  
So i decided to open up the longer (to specs) one and slowly shorten the covering shield step by step and it became better and better.
At the max point i locked it in place with some hot glue on the bottom and a few shrinkwraps over the length.
Then i finalised it with a very small cut from the top of the active element to do the final finetune with the analyser.
Totaly dont understand the resulting sizes (asymetric) i ended up with other than the different velocity factor in the airgapped bottom part that must have come into play, which contains a plastic straw (slightly compressed/deformed) and shrinkwrap stuff . Also as the straw was 5mm diameter , i had to cut the RG142 about 75% longer than the final length when i build it , as to push it over the straw and shrinkwrap layer, i had to push it (the braids) tighter together. So thicker , more massive shield and slightly wider airgap filled with some straw plastic.
Ended up with around 66 shielded bottom segment and 75 active element and its tuned super good to 868Mhz.

 

p.s. Now i also know that my Vas shapeshifter and TBS diamond are super at 868Mhz. A TBS TX tuned antenna is useless for me (tuned very well at around 900Mhz, but bad  with 3.6VSWR and -5dB S11 at 868Mhz, so will salvage it for parts).
Funny enough the old faithfull Immortal-T's are pretty solid as well for 868Mhz (which explains me hitting easy 5+KM's with them, more limited by my video.).

Hi fpvapnea,

Good Job  

iFly  

Love this analyser thingy...
Managed to retune the TBS RX tuned antenna from garbage on 868MHZ to 1.24ish VSWR , based on my small experience with tuning my own build antennas, by adding some copper material to the bottom of the original copper tube they used. 
Had not much laying around so found some copper 6.3 mm audio plug and took the bottom part.
I slowly adjusted the position up and down to find the sweetspot, then soldered in place . After the shrinkwrap I cut a mm or so from the active top to get it where i wanted it.
Nice

 

WOOOOOOOWWWWWWWWWW.....

After this weeks experiences I came up with a better/simpler way to create something inbetween the ibCrazy type and the type 3.
Both have the same concept in the end. The passive part a semi rigid or rigid shield/conductor over an airgap consisting of either pure air or a mix of air and some material like shrink wrap or like my last builds a plastic straw plus shrinkwrap.
Depending on the resulting velocity factor inside the gap of this mix and the conductiveness of the used shield material, it results in some hard to predict length of the passive element and resulting balancing length of the active part.
So the trick i did :
- make it adjustable so it can more easily be tuned on the analyser.
- make the gap non deformable for stability in shape/quality (pure shrinkwrap collapses deforms and plastic straw as well ,although more stable, and this changes the velocity factor and therefore the resulting tune)
- make the shield as solid as possible , so either a tube (which is not adjustable by itself, but you could use a sliding ring of material on top like i did with the TBS TX antenna ) or very tightly wound / sqeezed solid braided shield material.

So what i did, i took the braided shield out of the RG142 as before, but not throw away the outer plastic shield , but keep that, cut it to length and push the braided metal shield over the top of the plastic shield. Compress it so it becomes very sold (so you require much more lenght then the final lenght once compressed down , almost like a solid copper tube. The more solid the better
Then slide this whole thing on top of the original core design , making sure the length of the plastic is from the top of the SMA connector to just below the little exposed RG316 shield. 
Solder the top of the braided shield to the inner RG316 shield as before. Make this a neat as possible !!! No messy job or it will kill the quality

Now the tuning.  
I started with the active element a bit longer than i expected to end up with. So i started with about 95mm
Now this contraption can be tuned from the bottom mmost tricky part first (stretching or compressing the braided shield up or down, making it shorter/longer) and push the resonant frequency up and down close to or or exactly on top of the target frequency.
Below a picture of it without the shrinkwrap so you can understand better how this works.


It takes patience but you can get it perfectly close if your solder job is nice and the braided shield is nice , solid and clean cut.
Once happy (and it already blew my mind at that point), i super glued the bottom part to not shift anymore.
Then 1 layer shrink-wrap on top and keep measuring.
After final shrink-wrap , i had to cut a few mm off the top to get it back to perfection. And my god what values.
I think this thing goes to battle with the one from the 2 rocket science friends of Krohsis   

( p.s Maybe it is because on paper i am also a legit rocket scientist ;-)  Studied aerospace engineering in the Netherlands a lifetime ago , but i call it still valid   )

The final measure i ended up with where 91.5mm for the active and 71mm for the passive element for a 868Mhz tune. Total weight 8.9gram

Look at these insane numbers............ 


 

Hi fpvapnea,

Excellent Job,   Mate      


Later, My Friend, iFly  

(01-Sep-2023, 06:10 PM)fpvapnea Wrote: WOOOOOOOWWWWWWWWWW.....

After this weeks experiences I came up with a better/simpler way to create something inbetween the ibCrazy type and the type 3.
Both have the same concept in the end. The passive part a semi rigid or rigid shield/conductor over an airgap consisting of either pure air or a mix of air and some material like shrink wrap or like my last builds a plastic straw plus shrinkwrap.
Depending on the resulting velocity factor inside the gap of this mix and the conductiveness of the used shield material, it results in some hard to predict length of the passive element and resulting balancing length of the active part.
So the trick i did :
- make it adjustable so it can more easily be tuned on the analyser.
- make the gap non deformable for stability in shape/quality (pure shrinkwrap collapses deforms and plastic straw as well ,although more stable, and this changes the velocity factor and therefore the resulting tune)
- make the shield as solid as possible , so either a tube (which is not adjustable by itself, but you could use a sliding ring of material on top like i did with the TBS TX antenna ) or very tightly wound / sqeezed solid braided shield material.

So what i did, i took the braided shield out of the RG142 as before, but not throw away the outer plastic shield , but keep that, cut it to length and push the braided metal shield over the top of the plastic shield. Compress it so it becomes very sold (so you require much more lenght then the final lenght once compressed down , almost like a solid copper tube. The more solid the better
Then slide this whole thing on top of the original core design , making sure the length of the plastic is from the top of the SMA connector to just below the little exposed RG316 shield. 
Solder the top of the braided shield to the inner RG316 shield as before. Make this a neat as possible !!! No messy job or it will kill the quality

Now the tuning.  
I started with the active element a bit longer than i expected to end up with. So i started with about 95mm
Now this contraption can be tuned from the bottom mmost tricky part first (stretching or compressing the braided shield up or down, making it shorter/longer) and push the resonant frequency up and down close to or or exactly on top of the target frequency.
Below a picture of it without the shrinkwrap so you can understand better how this works.


It takes patience but you can get it perfectly close if your solder job is nice and the braided shield is nice , solid and clean cut.
Once happy (and it already blew my mind at that point), i super glued the bottom part to not shift anymore.
Then 1 layer shrink-wrap on top and keep measuring.
After final shrink-wrap , i had to cut a few mm off the top to get it back to perfection. And my god what values.
I think this thing goes to battle with the one from the 2 rocket science friends of Krohsis   

( p.s Maybe it is because on paper i am also a legit rocket scientist ;-)  Studied aerospace engineering in the Netherlands a lifetime ago , but i call it still valid   )

The final measure i ended up with where 91.5mm for the active and 71mm for the passive element for a 868Mhz tune. Total weight 8.9gram

Look at these insane numbers............ 


 

 
Outstanding numbers!  Way to go!  So when do you plan to field test?

(01-Sep-2023, 08:32 PM)Krohsis Wrote:  
Outstanding numbers!  Way to go!  So when do you plan to field test?

Probably coming days somewhere as weather going to be good.

Well today was that day. No wind , 25C and i had just converted my 6inch from Betaflight to Inav so ready for a maiden flight with new software and new antenna . No risk no gain no fun 
After messing for an hour to get this damned compas thing sorted out in the field, i did a quick first flight with some distance to test this antenna. Turned around at 3km as the RTH arrow was pointing in the same direction as me flying so guess i was off 180 degrees. Ouch.
But the antenna was like i was flying 10 meters out. OMG .
Then after finished playing with all the inav stuff like alt hold, pos hold and a small autonomous wp mission it was time for some more daredevil maiden. Why not.
So at about 6 km i was running out of land, and DJI was getting a bit more tricky (flew in a sideways curve after hitting the coastline so bit difficult to point my helicals) so turned around , but the antenna was not even getting warmed up. This thing rocks.
Incredible. Compared to my last 5km flight where crossfire was almost giving up on me, i can easily double this now (or more).
Also i was flying for at least the 1st 2-3km lowish to the ground and did not need to pull up as normal.
So i can forget about control link. Nice, one less guage to monitor so only my dji MB/s and bat voltage/amps to care for.

So the conclusion that this antenna build method is not only way easier then the metal tube Gen 3, as hand tunable during/after build , leads to a lighter build, but also on par performance wise. I call it a Gen 2.9 build.

And all i need is 1 super antenna as have put an sma on all my mid/lr quads so i can screw it on the one i am flying. I am super happy and can add another skill to my arsenal.