New 31 foot vertical homemade.

[PA5COR]

As you know I use (d) the Imax 2000 with radials for 10-17 meters on the roof.
Since 10/12/15 worked good but 17 already saw a decrease in efficiency I decided to make something nw.

It became the 31 foot vertical made partly of titanex alu tubing very strong and almost indestructible as used in my 77 foot inverted L.

Tested several 1:4 unun's piccie is of the test T200-2 core, with Teflon wire on it.

Last and chosen unun is the FT240 -43 core with 11 bifilar windings on it as 1:4 unun.

Bagged me testing on 15 meters Bear island with 5 watts...... not intended, but just happened.
Since this summer will see a complete redo and maintenance on the roof it will replace the Imax antenna for 40 - 10 it even has a good SWR on 6 and 4 meters, though the radiation pattern there might be a bit iffy....;)

Why 31 foot? I wanted to stay below the full 10 meter length, so it still gets a decent 10 meter pattern.
31 feet so the swr on 40 is now 1:2.5 measured with the MFJ 269 analyser at the balun can easily be tuned flat.
Made a 1:1 choke with a FT 240 - 43 core and RG 58 with 10 windings on that to keep the coax from getting RF on the outside.

Testing it here on the ground between the houses looking quite good, swr never higher as 1: 1.3 except 40 meters.
Could tune it even on 160, but will work as a leaky dummy load there with the 9.5 meters radiator.

So, why is everyone not building/making/testing homebrew antenna's here?
piccie 1.jpgpiccie 2.jpgpiccie 3.jpg

[WØTKX]

Speaking for myself, it's because I'm not gainfully retired. Yet.

Besides, it's ski season. ;)

[NQ6U]

All but one of my antennas is home made. The one exception is a little 70cm ground plane that was given to me.

[PA5COR]

Old Imax 2000 top sections = given to me, as was the old Imax on the roof, cost = 0
Titanex tubing bought cheap from importer 20 feet total about 20 euro's. left over from the inverted L antenna.
Glassfiber camo stick 4 feet from the army, bought 3 at the hamfest for 6 euro, used one.
Is isolator and mounting section, 2,5 feet into the 31 fet section rest for in the clamps on the chimney.
FT240-43 core 9 euro, Teflon wire got 100 feet blue and 100 feet grey with silvered wire inside, 10 bucks from left overs of the building of an plane it is used in.
Add coffee, 3 hours work to fit together, lots of fun testing several unun's I had from other projects.
Inverted L homebrew, active loop homebrew, FD-4 spare homebrew.
Baluns unun's homemade.
Have fun ;)

[KG4CGC]

Nice project. I've been considering a vertical folded loop wire design. For SWLing mainly but it could work on 160/80 if I can get the feedpoint high enough.

[PA5COR]

Rebuild the antenna this afternoon, fine sunny weather 15 C and after working a few days the length of the antenna for 12/10 was too high, the lobes crept up too high ( over 5/8 on 10...)
So, took off the top, with the Imax 2000 sections, added Titanex alu piping up to 24 feet ( 7.35 meters) and retry.
Strangly the swr on 40 became better was 1:4 now 1:3 and above all mostly within 1:1.2 even 50 MHz...
Compared to the OCF and Imax 2000 on the roof it was decent, the Imax through being on the roof at 40 feet above ground did have om 15 12 and 10 a little higher signal, but barely.
Getting the 24 footer above the roof will clear the groundclutter and the choke balun added ( FT 240 - 43 core with Teflon coax)
A bunch of radials will do the rest.
The 1:4 unun still the same, Ft240 - 43 core with 11 bifilar Teflon wire windings.
Handled 400 watts carrier for 5 minutes without sweating.

So, all in all, 40/30/20/17/15/12/10/50 in one stick...

[PA5COR]

Final version, 25 feet radiator, Ft 240 - 43 Unun with 11 bifilar Teflon wires as 1:4 unun.
At the final install on the roof there will be added a Ft240 - 43 choke balun after that.
Stinger next to the radiator, 1 1/2 feet away from the radiator, starting from the ground connection 4 feet of alu tubing in the middle of the vertical section a 1,5 micro Henry coil, in my case 9 windings Teflon coated wire around a 20 mm plastic core that also holds the 2 vertical sections of the 10 meter stinger.
The stinger is directly connected to the ground section and radials, 5.5 feet total and coil from the ground connection 1.5 feet to the side then vertical next to the main radiator.
Use UV resistant plastic/Teflon spreaders to mount the stinger and keep the distance from the radiator.


That one will lower the lobe for 10 and 12 to dx levels.
Raised the antenna 5 feet from the ground, added 2 free hanging radials of 9 meter long also 5 feet above ground.

SWR from 40 meters up to 6 meters 1 on 1.1 except 20 meters 1 on 1.4 and 17 and 15 each 1 on 1.3

[W3WN]

I was serious, what I said in the other thread.

Get me some pictures, write me up a little article on how you designed and built it. I'll print it.

[PA5COR]

Some background.
The Imax does perform very well on 10/11/12/15.
17 already shows that the antenna can be tuned, it is not optimal.
Forget 20 and yes I run the Imax with radials up to 4 x 5 meters and original GPK package....
Chosing the main radiator element length I worked my way down from 31 feet to now 25 feet, went as low as 20 feet to see what the effects were in SWR, radiation resistance and efficiency.

Normally we pick a length that is maximum 5/8 on the highest frequency because otherwise the vertical will has it's lobes there pointing up in the sky if we use a longer length.
That would be 6.6 meters length, or around 22 feet.
With that length the 40 meter suffered quite in efficiency ( still well under 1/4 wave there) so not very effective low rr so high losses.

Picking the 25 feet proved to be a lot better, SWR now elevated 5 feet over ground and 2 radials free of the ground was very satisfactory.
Running 200 watts carrier in the antenna for 10 minutes on each band didn't heat up the 1:4 unun, ( Ft240 - 43 core)

All other bands were almost perfect, worst is 1:1.3....
The stinger raises the 10/12 meter current point and lowers the lobs to a dx portion instead as looking up too much, no other effects on the other bands, see the stinger as a stub.
after instaslling the stinger tune it to just over the 10 meter band 30.5 to 31 MHz for best effect.
Check with beacons on your reception signal for maximum effect.

On my chimney I see this as the longest vertical without guying I can reliably get away with ( concrete chimney) and force 12+ gales we have here sometimes.
That was the reason to pick the supply of Titanex tubing I have around here, from 1 3/4 inch up to the smallest tube on top of 20 millimeter, wall thickness 1/10th of an inch.

The FT240 - 43 was chosen to have a reasonably high Mu and therefore enough high value, 7 MHz is almost 20.000 Ohms, 29 MHz is 82.000 Ohms.
Mu is 850.
The same cores are used as wideband chokes here good for 1500 watts ( single core) and Teflon 5 mm coax around them.
I'll run my definitive tests with 800 watts later in the weekend when the stinger is at it's place permanently.
I tested T225 - 2 cores, and found them lacking, they handle high power but they need 2 x 19 bifilar windings to be a bit effective for 40 meters, and then the capacitance starts to throw things off the rocks.
Too long windings around the core form capacity and will put things off the scale.
Max length of wire on the cores is 10% of the highest frequency in use ( 10 meter max wire length 1 meter).
Put tape on the FT 240 - 43 cores they conduct,so isolate them and use Teflon wire to make the unun.

The stinger idea was from here: http://www.eham.net/articles/29052, found late yesterday evening and made today.
Read that article including the piccies diagrams lobes for each band etc.
I already decided to 25 feet max radiator length so the stinger was optional.

[w2amr]

Nice job Cor.