antenna build… marks out of ten?

[plingboot]

Just finished my first two VAS antennas, could i double check that i've assembled these correctly please?

Top views are slightly off centre.

Plan to pt a blob of hot glue or daub of plastidip over the centre, soldered area to protect it a bit
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[sircana]

Your are running the feed in parallel with the lobe wires...
The shield should arrive just to the point where the wires are horizontal:

[MASHTON1138]

^+1.

Check out my antennas here http://fpvlab.com/forums/showthread....-antennas-ever I built them using the same technique you used for bottom feeding. The path does not end until the solder joint so you want the 90 degree bend for the ground leg to be as close as possible to the top of the shield and solder the legs to the sheild starting at the 90. Also here is a Alex's How to on these antennas, it is for a Cloverleaf but the method is the same for assembly.


View this video on YouTube

[IBCrazy]

^What they said. Move that 90 degree bend down to the coaxial cable shield. Otherwise the antenna will have poor resonance and the radiation pattern will be distorted.

-Alex

[plingboot]

umm… bit of a build fail then?

I've subsequently finished up these two antennas - with a blob of hot glue and head shrink and they 'look' ok and appear to be pretty bomb proof.

As they stand, can anyone estimate how much of a detriment to performance this construction will cause? I'm awaiting deliver of my goggles and Rx so can't actually test them myself yet.

I don't have enough components to build another two antennas right now, but if the consensus is that they'll probably be a load of c**p i'll order more parts and make another two - anyone in the UK know where i can fine the right angle rpsma connectors?

[GLEvideo]

If somebody with some machining skills were to turn out a small brass nipple that allows for easy soldering onto the feedline and then soldering of each leg of the antenna loop (whether it be a Clover Leaf, SPW or Pentalobe or whatever) then this little piece of hardware would be extremely sought after by most antenna builders of this variety. It would simplify the build. It would clean up the solder glob that everyone seems to end up with. It would also make the structure more robust and it would allow for some consistency in construction, performance and specifications. It should be in three parts. A brass ring or collar for the base, possibly with notches or holes for the wire, then an insulator tube bonding the base to a small ring ( or a small ball ) at the top that also has small holes. Does anybody else see this in their mind? Do I need to sketch it out?

[Hucker]

Can't he fix/improve it by adding solder as high up as possible? On the ones that are finished, just cut off the heat shrink, and use a heat gun or boiling water to wash away the hot glue, then solder as needed. I have an antenna where I did exactly what you did..

Not really. The impedance of a cable is porportional to the ratio of the conductor diameters. Thus simply adding solder will not fix the issue.

Building these antennas at 5.8GHz is extremely difficult for anyone but an advanced modeler. It needs to be precise. This is why all of mine are still made by hand.

-Alex

[IBCrazy]

If somebody with some machining skills were to turn out a small brass nipple that allows for easy soldering onto the feedline and then soldering of each leg of the antenna loop (whether it be a Clover Leaf, SPW or Pentalobe or whatever) then this little piece of hardware would be extremely sought after by most antenna builders of this variety. It would simplify the build. It would clean up the solder glob that everyone seems to end up with. It would also make the structure more robust and it would allow for some consistency in construction, performance and specifications. It should be in three parts. A brass ring or collar for the base, possibly with notches or holes for the wire, then an insulator tube bonding the base to a small ring ( or a small ball ) at the top that also has small holes. Does anybody else see this in their mind? Do I need to sketch it out?

I use square brass hobby tubing for the skew wheels. I forget what size it is, but it fits perfectly. I just slide the lobes in and crimp it down with a specialty cut set of pliers.

-Alex

[MASHTON1138]

Can't he fix/improve it by adding solder as high up as possible? On the ones that are finished, just cut off the heat shrink, and use a heat gun or boiling water to wash away the hot glue, then solder as needed. I have an antenna where I did exactly what you did..

Not really. The impedance of a cable is porportional to the ratio of the conductor diameters. Thus simply adding solder will not fix the issue.

Building these antennas at 5.8GHz is extremely difficult for anyone but an advanced modeler. It needs to be precise. This is why all of mine are still made by hand.

-Alex

Not really. He cannot simply add the solder to fix it. If he were to cut the shrink tube off, heat the glue and clean it off, then de-solder the elements from the entire coax he could reuse the lobes and coax.
plingboot try this and start over. You will need to strip more of the insulator around the center conductor and shorten it. Dont forget to remove the sheilding first. Cut the sheilding down to about 2-5mm longer than the legs, and then cut and strip the center conductor just a couple mm's longer than the shield and strip the insulator leaving enough to prevent a "short" (true the antenna is shorted if you are talking ac/dc voltage but not in this case). Then solder the legs to the feed with the 90 as close as you can get it to the top of the sheilding, then solder the lobes to the center conductor. Hope this helps.

Marc