Topics

Yagi- more


John Fell
 

23cm Yagi Feeding

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .
Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....


The pics below should elaborate :
The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .
The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .


JOhn 
G0API


Robin Szemeti - G1YFG
 

Interesting notes, and a novel workaround to the "loop height" problem.  Thanks for sharing.

The "antenna pointing upwards" is a work of genius, I have no idea why I did not think of that, I use that method for measuring axial response of loudspeakers, why it did not occur to me for antennas is beyond me, thank you!


On Mon, 20 Jul 2020 at 10:58, John Fell <john.g0api@...> wrote:
23cm Yagi Feeding

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .
Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....


The pics below should elaborate :
The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .
The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .


JOhn 
G0API


John Fell
 

Robin,
This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>


23cm Yagi Feeding

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .
Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....


The pics below should elaborate :
The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .
The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .


JOhn 
G0API


Robin Szemeti - G1YFG
 

Interesting ...

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...



On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:
Robin,
This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>


23cm Yagi Feeding

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .
Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....


The pics below should elaborate :
The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .
The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .


JOhn 
G0API


--
Robin Szemeti - G1YFG


John Fell
 

I built 10 of the 39 el DL6WU for 23cm in 1988 - 2 boxes of 4 used for 23cm contesting when I got fed up with spending hours on VHF NFD tweaking G3JVL Quad Loop Yagis in a 200 el array (don't make the elements out of sheared 18swg Alum ! ). One of the 10 is on my mast now.

I did test a prototype using the double split sheath balun but went for the folded dipoles as for contesting you need the minimum of "fiddly" things that fracture and more screw on and play .Weatherproofing was an issue .
Mind you 2 boxes of 4 and identical N type terminated interconns to  two ,4 way and one , 2 way power dividers takes a bit of time to make .

73
John
G0API

On Wed, 23 Sep 2020 at 18:59, Robin Szemeti - G1YFG <robin@...> wrote:
Interesting ...

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...



On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:
Robin,
This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>


23cm Yagi Feeding

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .
Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....


The pics below should elaborate :
The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .
The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .


JOhn 
G0API


--
Robin Szemeti - G1YFG


Robin Szemeti - G1YFG
 

10 sounds like quite a handful!  My plan is that by 2021 NFD gets here I want to have a red hot open class setup for either 23cm or 70cm ... so at the moment, both are making progress.  On 23cm I have the txvtr, PA and at least some progress on the aerials.   On 70cm I have a new txvtr, LNA and a good pattern for the aerials if I choose to build more.  The PA is still "coming together".  As ever, it is all the buggering about I really enjoy ;)


On Wed, 23 Sep 2020 at 19:12, John Fell <john.g0api@...> wrote:
I built 10 of the 39 el DL6WU for 23cm in 1988 - 2 boxes of 4 used for 23cm contesting when I got fed up with spending hours on VHF NFD tweaking G3JVL Quad Loop Yagis in a 200 el array (don't make the elements out of sheared 18swg Alum ! ). One of the 10 is on my mast now.

I did test a prototype using the double split sheath balun but went for the folded dipoles as for contesting you need the minimum of "fiddly" things that fracture and more screw on and play .Weatherproofing was an issue .
Mind you 2 boxes of 4 and identical N type terminated interconns to  two ,4 way and one , 2 way power dividers takes a bit of time to make .

73
John
G0API

On Wed, 23 Sep 2020 at 18:59, Robin Szemeti - G1YFG <robin@...> wrote:
Interesting ...

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...



On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:
Robin,
This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>


23cm Yagi Feeding

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .
Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....


The pics below should elaborate :
The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .
The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .


JOhn 
G0API


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


John Lemay
 

Robin

 

Have you considered using “Paraclips”? Available here:- http://www.powabeamantennas.co.uk/

 

These hold the element above and insulated from the boom, so you can easily fit a split dipole at the same height. You might be able to 3D print similar, but my experiments showed that it’s tricky to print something robust enough.

 

You can see my implementation using Paraclips here:- http://www.g4ztr.co.uk/amateur-radio/23cms/

 

(My blog is sorely out of date and I’ve moved on to a parabolic dish for 23cms, but that isn’t because the yagi went out of favour, it’s because a dish gives me multiband potential).

 

Regards

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Robin Szemeti - G1YFG
Sent: 24 September 2020 00:49
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Yagi- more

 

10 sounds like quite a handful!  My plan is that by 2021 NFD gets here I want to have a red hot open class setup for either 23cm or 70cm ... so at the moment, both are making progress.  On 23cm I have the txvtr, PA and at least some progress on the aerials.   On 70cm I have a new txvtr, LNA and a good pattern for the aerials if I choose to build more.  The PA is still "coming together".  As ever, it is all the buggering about I really enjoy ;)

 

 

On Wed, 23 Sep 2020 at 19:12, John Fell <john.g0api@...> wrote:

I built 10 of the 39 el DL6WU for 23cm in 1988 - 2 boxes of 4 used for 23cm contesting when I got fed up with spending hours on VHF NFD tweaking G3JVL Quad Loop Yagis in a 200 el array (don't make the elements out of sheared 18swg Alum ! ). One of the 10 is on my mast now.

 

I did test a prototype using the double split sheath balun but went for the folded dipoles as for contesting you need the minimum of "fiddly" things that fracture and more screw on and play .Weatherproofing was an issue .

Mind you 2 boxes of 4 and identical N type terminated interconns to  two ,4 way and one , 2 way power dividers takes a bit of time to make .

 

73

John

G0API

 

On Wed, 23 Sep 2020 at 18:59, Robin Szemeti - G1YFG <robin@...> wrote:

Interesting ...

 

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

 

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...

 

 

 

On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:

Robin,

This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>

 

23cm Yagi Feeding

 

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

 

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .

Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

 

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....

 

The pics below should elaborate :

The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .

The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

 

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .

 

 

JOhn 

G0API


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


Virus-free. www.avg.com


Neil Smith G4DBN
 

Paraclips are certainly a good solution for 70cm, I was thinking of trying to make something similar from PEEK to make a 13cm yagi to replace my old rear-mount Wimo for use when it is too windy to raise the SCAM with a 1m dish on top.  Although PEEK isn't a brilliant RF dielectric, it is a very good engineering plastic and machines extremely well, so making self-aligning standoffs suitable for 23/13cm yagis would be reasonably simple.  Because the material is strong, it should be possible to make the parts fairly thin.  PEEK is expensive though, so whether it is practical for anything other than one-offs, I rather doubt. Might be easy enough for anyone with a desktop CNC engraver/router to make.  Certainly easy to do on manual machines with the help of a couple of customer fixtures, but it would be tedious work. Glass-filled nylon is a non-starter because of the way it soaks up water and the relative permittivity varies with the weather. Delrin might work, but the sections would need to be thicker than with PEEK.  Another alternative might be to use a small diameter GRP tube boom and mount the entire antenna in a thin-walled PE or PU extruded round/rectangular section tube with thin spacers to hold it in the middle, then fill the tube with PU foam.  That would need experiments to determine the permittivity of the foam, and a lot of messing about scaling the design to work when immersed in that dielectric.  Huge fun for dark winter evenings though...

Neil G4DBN

On 24/09/2020 08:39, John Lemay wrote:

Robin

 

Have you considered using “Paraclips”? Available here:- http://www.powabeamantennas.co.uk/

 

These hold the element above and insulated from the boom, so you can easily fit a split dipole at the same height. You might be able to 3D print similar, but my experiments showed that it’s tricky to print something robust enough.

 

You can see my implementation using Paraclips here:- http://www.g4ztr.co.uk/amateur-radio/23cms/

 

(My blog is sorely out of date and I’ve moved on to a parabolic dish for 23cms, but that isn’t because the yagi went out of favour, it’s because a dish gives me multiband potential).

 

Regards

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Robin Szemeti - G1YFG
Sent: 24 September 2020 00:49
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Yagi- more

 

10 sounds like quite a handful!  My plan is that by 2021 NFD gets here I want to have a red hot open class setup for either 23cm or 70cm ... so at the moment, both are making progress.  On 23cm I have the txvtr, PA and at least some progress on the aerials.   On 70cm I have a new txvtr, LNA and a good pattern for the aerials if I choose to build more.  The PA is still "coming together".  As ever, it is all the buggering about I really enjoy ;)

 

 

On Wed, 23 Sep 2020 at 19:12, John Fell <john.g0api@...> wrote:

I built 10 of the 39 el DL6WU for 23cm in 1988 - 2 boxes of 4 used for 23cm contesting when I got fed up with spending hours on VHF NFD tweaking G3JVL Quad Loop Yagis in a 200 el array (don't make the elements out of sheared 18swg Alum ! ). One of the 10 is on my mast now.

 

I did test a prototype using the double split sheath balun but went for the folded dipoles as for contesting you need the minimum of "fiddly" things that fracture and more screw on and play .Weatherproofing was an issue .

Mind you 2 boxes of 4 and identical N type terminated interconns to  two ,4 way and one , 2 way power dividers takes a bit of time to make .

 

73

John

G0API

 

On Wed, 23 Sep 2020 at 18:59, Robin Szemeti - G1YFG <robin@...> wrote:

Interesting ...

 

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

 

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...

 

 

 

On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:

Robin,

This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>

 

23cm Yagi Feeding

 

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

 

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .

Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

 

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....

 

The pics below should elaborate :

The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .

The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

 

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .

 

 

JOhn 

G0API


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG



Alan Beard
 

Plastics,

Recycled plastic garden stakes, a good source of 20mm x 20mm rod. It's an antenna, does the RF care?

Alan VK2ZIW


On Thu, 24 Sep 2020 09:31:24 +0100, Neil Smith G4DBN wrote
> Paraclips are certainly a good solution for 70cm, I was thinking of trying to make something similar from PEEK to make a 13cm yagi to replace my old rear-mount Wimo for use when it is too windy to raise the SCAM with a 1m dish on top.  Although PEEK isn't a brilliant RF dielectric, it is a very good engineering plastic and machines extremely well, so making self-aligning standoffs suitable for 23/13cm yagis would be reasonably simple.  Because the material is strong, it should be possible to make the parts fairly thin.  PEEK is expensive though, so whether it is practical for anything other than one-offs, I rather doubt. Might be easy enough for anyone with a desktop CNC engraver/router to make.  Certainly easy to do on manual machines with the help of a couple of customer fixtures, but it would be tedious work. Glass-filled nylon is a non-starter because of the way it soaks up water and the relative permittivity varies with the weather. Delrin might work, but the sections would need to be thicker than with PEEK.  Another alternative might be to use a small diameter GRP tube boom and mount the entire antenna in a thin-walled PE or PU extruded round/rectangular section tube with thin spacers to hold it in the middle, then fill the tube with PU foam.  That would need experiments to determine the permittivity of the foam, and a lot of messing about scaling the design to work when immersed in that dielectric.  Huge fun for dark winter evenings though...
>
> Neil G4DBN
>
> On 24/09/2020 08:39, John Lemay wrote:
>


Robin Szemeti - G1YFG
 

The problem with praclips is firstly, the rod diameter. 5mm ... its a bit big for 23cm ... its like building a 2m antenna with 45mm (eg scaff pole) for elements.

Secondly, I am not convinced how "contest rugged" they would be,  not in uses, but in the getting snapped off during transport.  They do eliminate the problems with calculating boom correction, but, there again, its not an impossible task.


On Thu, 24 Sep 2020 at 09:31, Neil Smith G4DBN <neil@...> wrote:

Paraclips are certainly a good solution for 70cm, I was thinking of trying to make something similar from PEEK to make a 13cm yagi to replace my old rear-mount Wimo for use when it is too windy to raise the SCAM with a 1m dish on top.  Although PEEK isn't a brilliant RF dielectric, it is a very good engineering plastic and machines extremely well, so making self-aligning standoffs suitable for 23/13cm yagis would be reasonably simple.  Because the material is strong, it should be possible to make the parts fairly thin.  PEEK is expensive though, so whether it is practical for anything other than one-offs, I rather doubt. Might be easy enough for anyone with a desktop CNC engraver/router to make.  Certainly easy to do on manual machines with the help of a couple of customer fixtures, but it would be tedious work. Glass-filled nylon is a non-starter because of the way it soaks up water and the relative permittivity varies with the weather. Delrin might work, but the sections would need to be thicker than with PEEK.  Another alternative might be to use a small diameter GRP tube boom and mount the entire antenna in a thin-walled PE or PU extruded round/rectangular section tube with thin spacers to hold it in the middle, then fill the tube with PU foam.  That would need experiments to determine the permittivity of the foam, and a lot of messing about scaling the design to work when immersed in that dielectric.  Huge fun for dark winter evenings though...

Neil G4DBN

On 24/09/2020 08:39, John Lemay wrote:

Robin

 

Have you considered using “Paraclips”? Available here:- http://www.powabeamantennas.co.uk/

 

These hold the element above and insulated from the boom, so you can easily fit a split dipole at the same height. You might be able to 3D print similar, but my experiments showed that it’s tricky to print something robust enough.

 

You can see my implementation using Paraclips here:- http://www.g4ztr.co.uk/amateur-radio/23cms/

 

(My blog is sorely out of date and I’ve moved on to a parabolic dish for 23cms, but that isn’t because the yagi went out of favour, it’s because a dish gives me multiband potential).

 

Regards

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Robin Szemeti - G1YFG
Sent: 24 September 2020 00:49
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Yagi- more

 

10 sounds like quite a handful!  My plan is that by 2021 NFD gets here I want to have a red hot open class setup for either 23cm or 70cm ... so at the moment, both are making progress.  On 23cm I have the txvtr, PA and at least some progress on the aerials.   On 70cm I have a new txvtr, LNA and a good pattern for the aerials if I choose to build more.  The PA is still "coming together".  As ever, it is all the buggering about I really enjoy ;)

 

 

On Wed, 23 Sep 2020 at 19:12, John Fell <john.g0api@...> wrote:

I built 10 of the 39 el DL6WU for 23cm in 1988 - 2 boxes of 4 used for 23cm contesting when I got fed up with spending hours on VHF NFD tweaking G3JVL Quad Loop Yagis in a 200 el array (don't make the elements out of sheared 18swg Alum ! ). One of the 10 is on my mast now.

 

I did test a prototype using the double split sheath balun but went for the folded dipoles as for contesting you need the minimum of "fiddly" things that fracture and more screw on and play .Weatherproofing was an issue .

Mind you 2 boxes of 4 and identical N type terminated interconns to  two ,4 way and one , 2 way power dividers takes a bit of time to make .

 

73

John

G0API

 

On Wed, 23 Sep 2020 at 18:59, Robin Szemeti - G1YFG <robin@...> wrote:

Interesting ...

 

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

 

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...

 

 

 

On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:

Robin,

This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>

 

23cm Yagi Feeding

 

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

 

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .

Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

 

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....

 

The pics below should elaborate :

The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .

The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

 

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .

 

 

JOhn 

G0API


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG



--
Robin Szemeti - G1YFG


Bob_G1ZJP
 

Robin

 

When I used to weekend contest we ran 23 ele Tonnas either 8 + 8 or 1 x 16 which wasn’t really too good when windy, the pole bends quite a lot and the vertical beam width is very! Narrow ~ I still have 12 tucked away in the garage 😊 ~ if going /p, I used to mesh 4 together  and cable tie them together [reusable ties] and carry them in the car with a seatbelt around them – never had a damage problem in many years.

 

Bob, G1ZJP

 

 

 

 

From: Robin Szemeti - G1YFG
Sent: 24 September 2020 09:52
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Yagi- more

 

The problem with praclips is firstly, the rod diameter. 5mm ... its a bit big for 23cm ... its like building a 2m antenna with 45mm (eg scaff pole) for elements.

 

Secondly, I am not convinced how "contest rugged" they would be,  not in uses, but in the getting snapped off during transport.  They do eliminate the problems with calculating boom correction, but, there again, its not an impossible task.

 

On Thu, 24 Sep 2020 at 09:31, Neil Smith G4DBN <neil@...> wrote:

Paraclips are certainly a good solution for 70cm, I was thinking of trying to make something similar from PEEK to make a 13cm yagi to replace my old rear-mount Wimo for use when it is too windy to raise the SCAM with a 1m dish on top.  Although PEEK isn't a brilliant RF dielectric, it is a very good engineering plastic and machines extremely well, so making self-aligning standoffs suitable for 23/13cm yagis would be reasonably simple.  Because the material is strong, it should be possible to make the parts fairly thin.  PEEK is expensive though, so whether it is practical for anything other than one-offs, I rather doubt. Might be easy enough for anyone with a desktop CNC engraver/router to make.  Certainly easy to do on manual machines with the help of a couple of customer fixtures, but it would be tedious work. Glass-filled nylon is a non-starter because of the way it soaks up water and the relative permittivity varies with the weather. Delrin might work, but the sections would need to be thicker than with PEEK.  Another alternative might be to use a small diameter GRP tube boom and mount the entire antenna in a thin-walled PE or PU extruded round/rectangular section tube with thin spacers to hold it in the middle, then fill the tube with PU foam.  That would need experiments to determine the permittivity of the foam, and a lot of messing about scaling the design to work when immersed in that dielectric.  Huge fun for dark winter evenings though...

Neil G4DBN

On 24/09/2020 08:39, John Lemay wrote:

Robin

 

Have you considered using “Paraclips”? Available here:- http://www.powabeamantennas.co.uk/

 

These hold the element above and insulated from the boom, so you can easily fit a split dipole at the same height. You might be able to 3D print similar, but my experiments showed that it’s tricky to print something robust enough.

 

You can see my implementation using Paraclips here:- http://www.g4ztr.co.uk/amateur-radio/23cms/

 

(My blog is sorely out of date and I’ve moved on to a parabolic dish for 23cms, but that isn’t because the yagi went out of favour, it’s because a dish gives me multiband potential).

 

Regards

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Robin Szemeti - G1YFG
Sent: 24 September 2020 00:49
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Yagi- more

 

10 sounds like quite a handful!  My plan is that by 2021 NFD gets here I want to have a red hot open class setup for either 23cm or 70cm ... so at the moment, both are making progress.  On 23cm I have the txvtr, PA and at least some progress on the aerials.   On 70cm I have a new txvtr, LNA and a good pattern for the aerials if I choose to build more.  The PA is still "coming together".  As ever, it is all the buggering about I really enjoy ;)

 

 

On Wed, 23 Sep 2020 at 19:12, John Fell <john.g0api@...> wrote:

I built 10 of the 39 el DL6WU for 23cm in 1988 - 2 boxes of 4 used for 23cm contesting when I got fed up with spending hours on VHF NFD tweaking G3JVL Quad Loop Yagis in a 200 el array (don't make the elements out of sheared 18swg Alum ! ). One of the 10 is on my mast now.

 

I did test a prototype using the double split sheath balun but went for the folded dipoles as for contesting you need the minimum of "fiddly" things that fracture and more screw on and play .Weatherproofing was an issue .

Mind you 2 boxes of 4 and identical N type terminated interconns to  two ,4 way and one , 2 way power dividers takes a bit of time to make .

 

73

John

G0API

 

On Wed, 23 Sep 2020 at 18:59, Robin Szemeti - G1YFG <robin@...> wrote:

Interesting ...

 

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

 

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...

 

 

 

On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:

Robin,

This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>

 

23cm Yagi Feeding

 

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

 

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .

Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

 

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....

 

The pics below should elaborate :

The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .

The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

 

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .

 

 

JOhn 

G0API


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG

 


--
Robin Szemeti - G1YFG

 


Neil Smith G4DBN
 

Now I *really* want to see a 2m Yagi made from scaff poles.  Probably need a length of Rohn 25 for the boom....

Neil G4DBN

From: Robin Szemeti - G1YFG

Sent: 24 September 2020 09:52
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Yagi- more

 

... its like building a 2m antenna with 45mm (eg scaff pole) for elements.

 



Gordon REASON
 

I do'nt have one , and probably would'nt have any idea how to use one , but it seems to me ,

that an obvious answer, is the use of a 3D Printer ?

Once a successfull print/manufacture is done , the data information and material source , can be shared ,

for round , oval or square booms ................

Have a nice autumn ..........

---------- Original Message ----------
From: Robin Szemeti - G1YFG <robin@...>
To: UKMicrowaves@groups.io
Date: 24 September 2020 at 09:52
Subject: Re: [UKMicrowaves] Yagi- more

The problem with praclips is firstly, the rod diameter. 5mm ... its a bit big for 23cm ... its like building a 2m antenna with 45mm (eg scaff pole) for elements.

Secondly, I am not convinced how "contest rugged" they would be,  not in uses, but in the getting snapped off during transport.  They do eliminate the problems with calculating boom correction, but, there again, its not an impossible task.

On Thu, 24 Sep 2020 at 09:31, Neil Smith G4DBN < neil@...> wrote:

Paraclips are certainly a good solution for 70cm, I was thinking of trying to make something similar from PEEK to make a 13cm yagi to replace my old rear-mount Wimo for use when it is too windy to raise the SCAM with a 1m dish on top.  Although PEEK isn't a brilliant RF dielectric, it is a very good engineering plastic and machines extremely well, so making self-aligning standoffs suitable for 23/13cm yagis would be reasonably simple.  Because the material is strong, it should be possible to make the parts fairly thin.  PEEK is expensive though, so whether it is practical for anything other than one-offs, I rather doubt. Might be easy enough for anyone with a desktop CNC engraver/router to make.  Certainly easy to do on manual machines with the help of a couple of customer fixtures, but it would be tedious work. Glass-filled nylon is a non-starter because of the way it soaks up water and the relative permittivity varies with the weather. Delrin might work, but the sections would need to be thicker than with PEEK.  Another alternative might be to use a small diameter GRP tube boom and mount the entire antenna in a thin-walled PE or PU extruded round/rectangular section tube with thin spacers to hold it in the middle, then fill the tube with PU foam.  That would need experiments to determine the permittivity of the foam, and a lot of messing about scaling the design to work when immersed in that dielectric.  Huge fun for dark winter evenings though...

Neil G4DBN

On 24/09/2020 08:39, John Lemay wrote:

Robin

 

Have you considered using “Paraclips”? Available here:- http://www.powabeamantennas.co.uk/

 

These hold the element above and insulated from the boom, so you can easily fit a split dipole at the same height. You might be able to 3D print similar, but my experiments showed that it’s tricky to print something robust enough.

 

You can see my implementation using Paraclips here:- http://www.g4ztr.co.uk/amateur-radio/23cms/

 

(My blog is sorely out of date and I’ve moved on to a parabolic dish for 23cms, but that isn’t because the yagi went out of favour, it’s because a dish gives me multiband potential).

 

Regards

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Robin Szemeti - G1YFG
Sent: 24 September 2020 00:49
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Yagi- more

 

10 sounds like quite a handful!  My plan is that by 2021 NFD gets here I want to have a red hot open class setup for either 23cm or 70cm ... so at the moment, both are making progress.  On 23cm I have the txvtr, PA and at least some progress on the aerials.   On 70cm I have a new txvtr, LNA and a good pattern for the aerials if I choose to build more.  The PA is still "coming together".  As ever, it is all the buggering about I really enjoy ;)

 

 

On Wed, 23 Sep 2020 at 19:12, John Fell <john.g0api@...> wrote:

I built 10 of the 39 el DL6WU for 23cm in 1988 - 2 boxes of 4 used for 23cm contesting when I got fed up with spending hours on VHF NFD tweaking G3JVL Quad Loop Yagis in a 200 el array (don't make the elements out of sheared 18swg Alum ! ). One of the 10 is on my mast now.

 

I did test a prototype using the double split sheath balun but went for the folded dipoles as for contesting you need the minimum of "fiddly" things that fracture and more screw on and play .Weatherproofing was an issue .

Mind you 2 boxes of 4 and identical N type terminated interconns to  two ,4 way and one , 2 way power dividers takes a bit of time to make .

 

73

John

G0API

 

On Wed, 23 Sep 2020 at 18:59, Robin Szemeti - G1YFG <robin@...> wrote:

Interesting ...

 

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

 

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...

 

 

 

On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:

Robin,

This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>

 

23cm Yagi Feeding

 

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

 

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .

Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

 

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....

 

The pics below should elaborate :

The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .

The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

 

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .

 

 

JOhn 

G0API


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


 

 


--
Robin Szemeti - G1YFG


Jules G0NZO
 

There was an excellent talk by G8ADN at one of the Baisingstoke CAT BATC meetings.  (Cat16 ??)
About efficiently feeding antennas.
It was on the BATC youtube channel.

Jules


Chris Bartram G4DGU
 

Hello Neil

I have seen professional yagi designs for VHF (in ground-based avionics) which have used element diameters approaching 50mm! My own 1296MHz yagis use 4.76mm elements. Thicker elements tend to reduce the loaded Q and will also increase their surface area. For a given material that will also reduce the effective resistive losses and thus increase the bandwidth and efficiency of a yagi - and other antennas.

73

Chris G4DGU


Mark GM4ISM
 

Not yagis  but some big  band II transmit antenna use  spearhead X dipoles which sit in front of a reflector.

These have elements about 6 inches in diameter.   Power handling is only part of it ......

They are galvanised steel which make them pretty robust

Mark ISM

On 24/09/2020 11:33, Chris Bartram G4DGU wrote:
Hello Neil

I have seen professional yagi designs for VHF (in ground-based avionics) which have used element diameters approaching 50mm! My own 1296MHz yagis use 4.76mm elements. Thicker elements tend to reduce the loaded Q and will also increase their surface area. For a given material that will also reduce the effective resistive losses and thus increase the bandwidth and efficiency of a yagi - and other antennas.

73

Chris G4DGU






--
This email has been checked for viruses by AVG.
https://www.avg.com


 


Like this one, Mark. 88-108 MHz.

Ken YKI



Not yagis  but some big  band II transmit antenna use  spearhead X dipoles which sit in front of a reflector.


These have elements about 6 inches in diameter.   Power handling is only part of it ......

They are galvanised steel which make them pretty robust


Ian White
 

I've had good results with Paraclips and 4-5mm rod elements on 2m and 70cm - not portable, but over several years in a coastal environment. For /P, solid rod elements of all kinds have the huge advantage that in case of accident they almost always bend and can be straightened again, unlike tubing elements which usually either fold or snap.

4mm rod elements are also strong enough to withstand visits by large birds (as a pheasant could once testify). It's also worth noticing that the Wimo elements are 4mm diameter - and as others have already pointed out, that actually isn't "huge" in the broader scheme of things. The best way to deal with the unreliable joints between the parasitic elements and the side walls of the boom of the Wimo Yagis would be to drill out all the holes to take 4mm ID plastic rivets, and then shorten the existing elements appropriately.

One option for the driven element could be to change the rear end of the boom from metal to plastic or fibreglass. The non-conducting material would provide a lot more flexibility in element mounting.

If the parasitic elements are mounted well above the boom on Paraclips or similar, another option is to use a plastic box for the driven element mounting. The traditional folded dipole and half-wave coax balun can then be replaced with a direct 50-ohm feed and a sleeve balun, the open end of which is safe inside the waterproof box.

73 from Ian GM3SEK



On 24/09/2020 08:39, John Lemay wrote:

Robin

 

Have you considered using “Paraclips”? Available here:- http://www.powabeamantennas.co.uk/

 

These hold the element above and insulated from the boom, so you can easily fit a split dipole at the same height. You might be able to 3D print similar, but my experiments showed that it’s tricky to print something robust enough.

 

You can see my implementation using Paraclips here:- http://www.g4ztr.co.uk/amateur-radio/23cms/

 

(My blog is sorely out of date and I’ve moved on to a parabolic dish for 23cms, but that isn’t because the yagi went out of favour, it’s because a dish gives me multiband potential).

 

Regards

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Robin Szemeti - G1YFG
Sent: 24 September 2020 00:49
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Yagi- more

 

10 sounds like quite a handful!  My plan is that by 2021 NFD gets here I want to have a red hot open class setup for either 23cm or 70cm ... so at the moment, both are making progress.  On 23cm I have the txvtr, PA and at least some progress on the aerials.   On 70cm I have a new txvtr, LNA and a good pattern for the aerials if I choose to build more.  The PA is still "coming together".  As ever, it is all the buggering about I really enjoy ;)

 

 

On Wed, 23 Sep 2020 at 19:12, John Fell <john.g0api@...> wrote:

I built 10 of the 39 el DL6WU for 23cm in 1988 - 2 boxes of 4 used for 23cm contesting when I got fed up with spending hours on VHF NFD tweaking G3JVL Quad Loop Yagis in a 200 el array (don't make the elements out of sheared 18swg Alum ! ). One of the 10 is on my mast now.

 

I did test a prototype using the double split sheath balun but went for the folded dipoles as for contesting you need the minimum of "fiddly" things that fracture and more screw on and play .Weatherproofing was an issue .

Mind you 2 boxes of 4 and identical N type terminated interconns to  two ,4 way and one , 2 way power dividers takes a bit of time to make .

 

73

John

G0API

 

On Wed, 23 Sep 2020 at 18:59, Robin Szemeti - G1YFG <robin@...> wrote:

Interesting ...

 

What I was planning on trying was making a folded dipole with Pawsey stub ... and adding a parallel section of box tube boom near the feedpoint, and then when it is welded in place, removing a section of the boom at the feedpoint so the folded dipole can sit directly in the path of the dircectors ..

 

Ultimately, I want a "box of four" so whatever cock-eyed feed system I settle on needs to be stable and reproducible ...

 

 

 

On Wed, 23 Sep 2020 at 18:40, John Fell <john.g0api@...> wrote:

Robin,

This works well.

---------- Forwarded message ---------
From: John Fell <john.g0api@...>
Date: Mon, 20 Jul 2020 at 10:57
Subject: Fwd: Yagi- more
To: <ukmicrowaves@groups.io>

 

23cm Yagi Feeding

 

I found Vol No 14 -Autumn 3/1982 of VHF Communications yesterday , during a chuck out of olde tree based materials .

 

Gunther DL6WU and later , Ian GM3SEK , opened our eyes to Double Optimised , extremely Long Yagi Antennas .

Amongst the data a folded dipole feed was presented and that was the basis for the construction I used back in 1986 to build 10 off 39 el Yagis .

 

These were used at my QTH ( one is still on the mast and working well) and as 2 boxes of stacked and bayed , which was used in contests during the late 80's and early 90's by G4RFR/P .The construction was far more "contest" proof than the previous 800 el QLY array .....

 

The pics below should elaborate :

The o/a length of the long part of dipole is 112.25mm. The 2 short parts (L/4) are 50.25mm and the 6mm dia elements are 15mm c/c apart .

The 2 pillars used to support the N socket are 26mm long .My boom is 15x15 mm sq."TV antenna " semi-hard aluminium alloy and each element is retained by an M3 Nutsert and slotted cross head setscrew .

 

I cover the dipole feed area in Silicone conformal coating - the end plates linking the dipole arms are 6mm HE30 strips , secured to the 6mm components using 4BA SS Alum head setscrews .I test each Yagi using an EME Muller dual sampling line Power meter and with the antenna pointing vertically upwards the reflected RF component should be low , with the indicated VSWR in the 1.1 to 1.2 area . 

 

I have used the DL6WU design data for 50MHz (11 el , 50Ft boom) , 432 MHz standard and crossed for Sat working(20 el) and 2.3GHz (60 el) -all used folded dipole and balun driven .

 

 

JOhn 

G0API


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Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


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