Hi Krohsis,

Thanks for all of your help. I am not giving up on this. { I'm having way too much fun} 

If the next attempt doesn't get the results that I want, I will be looking for different copper tubing. 

Thanks 

Hi Krohsis,

I think my copper tube was not correct, so I now have 1/4 inch ID copper tubing is several thicknesses.

If you still have some of the tubing that you used, could you weight a 58mm piece (the size needed for the build) and let me know how many grams that it weighs. That way, I can cut the various pipes and compare the weight.

Thanks  

(17-Dec-2020, 03:27 PM)iFly4rotors Wrote: Hi Krohsis,

I think my copper tube was not correct, so I now have 1/4 inch ID copper tubing is several thicknesses.

If you still have some of the tubing that you used, could you weight a 58mm piece (the size needed for the build) and let me know how many grams that it weighs. That way, I can cut the various pipes and compare the weight.

Thanks  

Hey Harry, I will try to get that info to you when I can today.  We will be doing a Century ride today on the bicycles (100 miles).  So that will occupy most of my time today.

I'm not sure weight is what you want.  Copper is copper as long as it isn't a copper alloy with differing amounts of other metals.  I believe the critical measurements will be length, diameter and wall thickness.  Weight would be different with different wall thicknesses and diameters, but weight alone may take you down the wrong road.

(17-Dec-2020, 03:37 PM)Krohsis Wrote: Hey Harry, I will try to get that info to you when I can today.  We will be doing a Century ride today on the bicycles (100 miles).  So that will occupy most of my time today.

I'm not sure weight is what you want.  Copper is copper as long as it isn't a copper alloy with differing amounts of other metals.  I believe the critical measurements will be length, diameter and wall thickness.  Weight would be different with different wall thicknesses and diameters, but weight alone may take you down the wrong road.

Hi Krohsis,


Understood. The original copper tubing that I bought just doesn't seem to be working. It is, however, a thin wall. My thoughts on the weight are that if two pieces of the same length weigh the same, then the wall thickness would likely be about the same as well. I would also take the wall thickness if you have that. With these two additional pieces of information, I am hopeful that I can select the correct copper tubing, then it should just be a matter of cutting to length and putting it together.

No rush, I don't want to be a bother or interfere with "real life" activities. Have Fun  

Thanks  

Hey Harry,

You are no bother at all.  I just wanted to make sure you understood why I didn't give you the info you requested in a timely fashion.  I try to get back to people ASAP after they post as I know they maybe waiting for a response to proceed on their project.

Below are the pics of the measurements of the piece I cut today.  Hope this helps. 







The outside diameter wasn't perfectly round, with a high of 6.36mm and a low of 6.33mm.



Wall thickness was .55-.56mm.

Hi Krohsis,

Thank you very much     That is perfect, just what I was looking for.

Now, I can compare my tubing with yours and determine what I should use.

Thank You

2021-01-08

Well, with the holidays behind us, it is time to resume my work on this 915 mHz Gen 3 receiver antenna build.

Now, I have no doubt that the formula is correct; with the coax being correct, the only other thing is the copper sleeve. 

Let's first consider that the 58mm length is quite a bit shorter than the 75.50mm length of the active element. Since these lengths are normally the same, the mass of the passive sleeve must be the factor and why the passive copper sleeve is shorter; because it has more mass. In my mind, the formula is actually based upon the mass and the 58mm length is for a specific copper tubing. Furthermore, any deviation in the copper tube's diameter or wall thickness will effect the mass and may require a length adjustment to bring the mass into alignment with the formula.

Since, there is a direct relationship between mass and weight. I will start by analyzing the differences between the material that I have and the new information from Krohsis; specifically, the actual dimensions and weight of the piece of copper tubing used in his build.

Krohsis' Copper tubing:

Length:                         58 mm
OD:                           6.35 mm
Wall thickness:  0.55 - 0.56 mm
Weight:                     5.00 grams

Tubing used in my original build attempts:
    
Length:                      57.98 - 58.20 mm 
OD:                                        6.35 mm
Wall thickness:             0.34 -   0.40 mm
Weight:                                  3.00 grams

When comparing these values, there is 2 grams difference in mass {likely due to the thinner wall thickness}.
If we consider that the mass needs to match, then 2 grams is a pretty big difference. 

With this new information and analysis, let's proceed... 

2020-01-10

I have worked on this Gen 3 antenna build for the past couple of days without success.

With the active element at 75.50mm, I have tried different lengths of copper sleeves from 58mm to 66mm {the 64mm weighs 5 grams} and different tubes with different wall thicknesses; all without success.

Next {just to see the results}, I tried the active element at 78mm with different lengths of copper sleeves. This length actually produced better numbers but still in the 2.5 - 3.0 range. When I shortened the length to 75.5mm the numbers got worse.

At this point, I have consumed most of the raw material and have not even gotten close {not even as good as my first attempts}. 
I have made quite a few {Not Any Good}  antennas and now, I am running out of material and I am a little frustrated.

One irritation is that there is essentially NO effective method of adjustment after the antenna is together. What you get is what you got.
Furthermore, I have NO real clue as to what is wrong nor how to change when the number is too high. Do you add mass, add length, shorten length. Yes, I understand that it should work if EVERYTHING is SPOT ON, but what if it doesn't work. Where did it go wrong? Is it the raw material? What adjustments need to be made? What is different? What do you change or do different for the next build? Who can say? Who knows? 

Perhaps, I need to have a better understanding of antenna theory and construction {need to learn more}.  
At this point, I am not inclined to invest in additional material. I will need to study antenna theory, design, and construction.

Although I really wanted to have a successful build, it is just not working out for me.      No Gen 3 antenna at this point in time    

Moving on...

Hi Harry,

I told you it was difficult.  On the plus side when you get it right it is a super antenna, and easily removeable for transport or replacement if damaged. 

But given the gen 2 antenna is WAY easier to build and the performance is likely within 80% of the gen 3 and still very much superior to the Immortal T, the gen 2 is a better choice for most.

What I do know, when the 2 rocket scientists (literally) designed the antenna, they sourced parts and designed around those parts.  If you choose to build with parts that are different, you end up being a design engineer without the equipment they had available to them.  I know you didn't want to buy from the supplier they chose, so maybe it is there where your problem lies.

As for me, my issues were with the solder joint at the sleeve to shield.  I had several misses before I finally built 2 with great performance.  But even though I still have enough materials for 5 or 6 more antennas, I won't be building anymore Gen 3s.   

I think you bailing out at this point was a good decision.  Try building the Gen 2, I'm confident it will go well for you and you will be very pleased with the performance. 

Hi John,

Yes, I agree that it is likely with the material, specifically the copper tubing, but that just can't be helped. So, yeah, I would need to study some design engineering before attempting a Gen 3 build again. On the other hand, it has been quite a fun experience and I have learned quite a bit already and now have an antenna analyzer. Maybe after I pass antenna design 101, ha ha.    

I did look at the Gen 2 and think that will be my next antenna adventure. 

I want to Thank You very much for all of your help, assistance, and guidance. 

Hope you have a very Happy and Fun Filled 2021 

Harry  

(10-Jan-2021, 07:01 PM)iFly4rotors Wrote:  

Hope you have a very Happy and Fun Filled 2021 

Harry  

Hey thanks Harry, you as well.

As it turns out if 2021 goes as well as it started it should be a stellar year.  I'm actually getting some flying in where I got hardly any in 2020.

Let's make sure that Harry gets that 5km badge this year....and the honest way, 5km out and then return home...no cheating!!

(10-Jan-2021, 07:01 PM)iFly4rotors Wrote: Hi John,

Yes, I agree that it is likely with the material, specifically the copper tubing, but that just can't be helped. So, yeah, I would need to study some design engineering before attempting a Gen 3 build again. On the other hand, it has been quite a fun experience and I have learned quite a bit already and now have an antenna analyzer. Maybe after I pass antenna design 101, ha ha.    

I did look at the Gen 2 and think that will be my next antenna adventure. 

I want to Thank You very much for all of your help, assistance, and guidance. 

Hope you have a very Happy and Fun Filled 2021 

Harry  

Hi iFly4rotors (long time no chat ;-) )
Have been reading up on all the antenna build posts including your struggling with this fun Gen3 project. Was wondering did you ever retry get it working in the end ?
Am seriously contemplating giving it a go myself , but struggling to even find some consistent awnser to the measurements for EU's 868Mhz for this version of the antenna (so with the copper tube).
I did see some measurement on the alternative way with folded back brading and compulsory air-gap , but the whole reason i want to build (besides obvious quality and range improvements over immortal-t) is for having a semi stiff non flapping around in the wind antenna and that version looks way too flappy to me for my light mid/long range builds.
I played with a bardpole (ufl and sma versions) but due to its non round shape it is heavyly sensitive to sidewind and flaps around (bad for light quads flight performance etc).
The analyser is on the way already (even just to measure current status quo and comparison ), and have als got the tbs tuned tx just in case it is close enough or at least better than the immortal T for 868 after measuring.
Anyway, just curious and let me know if you have any further thoughts or tips for me.

Hi fpvapnea,

Regarding the Gen 3 antenna build. There are a couple of things 
that I had not understood or realized when I was working on it:

1) The only accurate test is when the antenna is fully constructed.
    Any intermittent testing is just not accurate. I was trying to test
    it before the final part of the construction so that was throwing
    my readings off a bit. Had I completely finished an antenna 
    before testing it, I might have had some very good results.

2) There is supposed to be an "air" gap between the coax shaft
    and the copper sleeve that I either overlooked or was not aware
    of. In any case, mine did not have the air gap.

3) The antenna is BIG and only really suitable for a 7-inch or larger
    quad. In fact, it is pretty big even for a 7-inch. Being big, it is 
    also a bit heavy. John made special aluminum mounting brackets
    just to hold the antenna. Mounting it with a TPU bracket on a 
    anything smaller than a 7-inch might be questionable. 

    Consequently, the Gen 3 antenna is simply not feasible for a
    sub-250 gram craft and questionable on a 5-inch quad. So,
    this antenna is really and truly only applicable for larger quads.
    Yet another reason that I just sort of discontinued my work on
    the Gen 3 DIY project. 

    The other reason that I tabled the project is that I really didn't
    need it when I made the decision to give up on long range due
    to the legal issues. When I realized that flying beyond visual line
    of sight is in violation of the FAA regulations (yeah, I know that
    one can get away with it), all of my stock antennas are sufficient
    for my flying range.

Now, a word about antenna "stiffness". I learned a neat little trick
from JJRotoGeek about how to stiffen antenna shafts which works
amazingly well and is exceptionally resilient. The basic concept is
to use hot glue covered with heat shrink tubing. It is a three (3)
part process as follows:
 
1) Apply a line of hot glue down the length of the antenna shaft. 
    I have a thin tip hot glue gun so I generally lay a line down one 
    side and then a second one on the other. If you have the larger
    size hot glue gun then a single line will likely be enough. I let
    the glue cool before moving to the next step which seems to
    work better than trying to slide the tubing over hot glue.

    NOTE: Don't worry about getting the hog glue even or 
              smooth because it doesn't matter at this stage
              and will be smoothed out in step 3.
           
2) Next, slide a length (longer than the hot glue line) over the
    U.FL connector and over the line of "cooled" hot glue. Since
    the glue is cool, it doesn't interfere with the tubing.

3) Finally, heat shrink the tubing. The heat also melts the glue
    and the shrinking of the tubing evens it out so that the end
    result is a decently round and smooth finished product.

    If it needs a bend, you can do an initial bending before the
    glue cools and sets up.

    If you need to change the antenna or bend it, you can just
    re-heat it and bend while the glue is hot. 

The finished product will retain its shape and stiffness, however,
it will bend just a bit during a crash and doesn't get broken. It
works amazingly well and will actually hold an antenna vertically.

The following video is from JJRottoGeek's Tech Tips: 



My Phantom-X with the VTX antenna shrouded in yellow heat shrink
tubing with hot glue inside and bent backwards a bit. The lower part
of the antenna shaft is zip tied to a standoff column above the top
deck plate. 




Here is my Katana-LR4 build with the hot glue and heat shrink applied to both antennas.
Notice the almost 90 degree bend on the 900 MHz antenna. Again, attached to a standoff
column above the top deck.



Here is my Ronin-MK1 ONE build. Yet again, the same way.



And there you have it.

Later, My Friend, iFly  

Thanks buddy. Helpfull info as always.
I was aware of the hot glue trick but completely forgotten as was ages ago i saw that trick. Tnx for the reminder and images !!! and I wil revisit some of my mini quad antenna mounts now.....

The airgap is indeed a tricky one and i am fully aware of it. The weight issue i had not thought a lot about yet and can see that that definitively can be an issue on smaller quads. I am building it for a recent 6 inch long range build for which i made a custom dual SMA connector / GPS back end in TPU and holds the current antennas super rigid, so doable. (have a trip planned to the cabin of some friends in the Swiss mountains in a few months so thats the target for this baby)

I actualy just an hour ago finished my first IBCrazy(s) alternative version. (the dude from Video Areal Systems) . Guess it is somewhere between gen2 and gen 3 for concept and also has an airgap and he has exact measures for 868Mhz (which are still m.i.a. for GEn3). I did it with a small plastic straw inbetween the airgapped shrinkwrap and the core to keep the shielding part at a fixed distance so easier to keep its airgap shape rather then just with the shrinkwrap (got that trick from the comments in the video). Stiffened with one extra layer of wrap seems already properly stiff, so for this one no hot glue needed. Total weight just below 10gram (so even 2grams lighter than my long range vista antenna) and no problem in my mount. Rock solid, construction wise.
I am still waiting for my analyser (it only just left China) so will cut / finalise the top part lentgh once its in and will see how good it is. Will work on getting that build version working before i even think about the coper tube version.
Regardless if i will use the actual gen3 coper tube version (eg if turns out too heavy or just bad) , its a fun project to try. The worry is with the exact metal tube , which you also struggled with and here in the EU that exact type is unobtanium , unless i get that from ebay from the US at insane shipment fees that make it not worth it. Will see

Anyway, will let you know how my current version(s) work once the analyser is in.

(26-Aug-2023, 02:50 PM)fpvapnea Wrote: Thanks buddy. Helpfull info as always.
I was aware of the hot glue trick but completely forgotten as was ages ago i saw that trick. Tnx for the reminder and images !!! and I wil revisit some of my mini quad antenna mounts now.....

The airgap is indeed a tricky one and i am fully aware of it. The weight issue i had not thought a lot about yet and can see that that definitively can be an issue on smaller quads. I am building it for a recent 6 inch long range build for which i made a custom dual SMA connector / GPS back end in TPU and holds the current antennas super rigid, so doable. (have a trip planned to the cabin of some friends in the Swiss mountains in a few months so thats the target for this baby)

I actualy just an hour ago finished my first IBCrazy(s) alternative version. (the dude from Video Areal Systems) . Guess it is somewhere between gen2 and gen 3 for concept and also has an airgap and he has exact measures for 868Mhz (which are still m.i.a. for GEn3). I did it with a small plastic straw inbetween the airgapped shrinkwrap and the core to keep the shielding part at a fixed distance so easier to keep its airgap shape rather then just with the shrinkwrap (got that trick from the comments in the video). Stiffened with one extra layer of wrap seems already properly stiff, so for this one no hot glue needed. Total weight just below 10gram (so even 2grams lighter than my long range vista antenna) and no problem in my mount. Rock solid, construction wise.
I am still waiting for my analyser (it only just left China) so will cut / finalise the top part lentgh once its in and will see how good it is. Will work on getting that build version working before i even think about the coper tube version.
Regardless if i will use the actual gen3 coper tube version (eg if turns out too heavy or just bad) , its a fun project to try. The worry is with the exact metal tube , which you also struggled with and here in the EU that exact type is unobtanium , unless i get that from ebay from the US at insane shipment fees that make it not worth it. Will see

Anyway, will let you know how my current version(s) work once the analyser is in.

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.