Wimo  in Germany has CP antennas at those frequencies.  73, Adrian AA5UK

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On Sun, Feb 28, 2021 at 7:30 AM, Mark Johns, K0JMk0jm.mark@gmail.com wrote: -----------------------------------------------------------

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On 2/28/21 10:01 AM, KENT BRITAIN wrote:

WA5VJB.COM   Reference Section has some 1269 MHz CP Yagis that are pretty easy to build.

And quite a variety of simple Yagi's for LEO birds.

Also remember that the NanoVNA v2 has a frequency range that covers the 1.2GHz and 2.4GHz bands:

https://nanorfe.com/nanovna-v2.html

$130 is _extremely_ inexpensive for this much functionality, and it takes all the guesswork out of antenna matching.

--- Zach N0ZGO

That doesn't appear to be the NanoVNA V2 (or S-A-A 2), which has a larger frequency range.

On Sun, Feb 28, 2021 at 1:18 PM saguaroastro saguaroastro@cox.net wrote:

R & L Electronics is selling the NANOVNA FOR $59.00. ,70.. after shipping. Mine is on the way.

http://www.randl.com/shop/catalog/product_info.php?products_id=75145

73 Rick Tejera (K7TEJ) Saguaro Astronomy Club Www.saguaroastro.org Thunderbird Astronomy Club Www.w7tbc.org

-------- Original message -------- From: Zach Metzinger zmetzing@pobox.com Date: 2/28/21 09:49 (GMT-07:00) To: amsat-bb@amsat.org Subject: [AMSAT-BB] Re: WTB: Circular Polarized Yagis for 1.2/2.4 GHz

On 2/28/21 10:01 AM, KENT BRITAIN wrote:

...

WA5VJB.COM Reference Section has some 1269 MHz CP Yagis that are pretty easy to build.

And quite a variety of simple Yagi's for LEO birds.

Also remember that the NanoVNA v2 has a frequency range that covers the 1.2GHz and 2.4GHz bands:

https://nanorfe.com/nanovna-v2.html

$130 is _extremely_ inexpensive for this much functionality, and it takes all the guesswork out of antenna matching.

--- Zach N0ZGO

---

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This is off topic since the discussion was about CP antennas. When considering a NanoNVA version 2 go for the original design not a clone: https://nanorfe.com/nanovna-v2.html. Mine came very quickly.

Now back to CP antennas.

73, Adrian AA5UK

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On Sun, Feb 28, 2021 at 3:51 PM, saguaroastro@cox.netsaguaroastro@cox.net wrote: -----------------------------------------------------------

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Hi Jerry I have taken an antenna range to over 60 conferences.   And done quite a bit or work with Helix antennas at my lab.  Of the 100 or so Helix's I have tested, only about 10% were circularly polarized.That's right, only about 1 in 10.    I have proven many many times,  HAMS CANNOT BUILD CP HELIX ANTENNAS!  It is amazing how a Helix Antenna can have an Axial Ratio of over 20 dB.   That's about the same axial ratio as you get from many Yagi's.       The few helix's that worked were usually built by a professional in the field. Unless you have actually tested your Helix on a range, the chances are about 9 out of 10 is it not CP(Yes, it is a valid statement that all antennas are ellipticaly polarized, CP and Linear are just special cases.). As an example, the wave comes down the helix, hits the tip, them reflects as a standing wave on the helix structure with an opposite CP sense.You can put a helix antenna on an antenna range, then start trimming the tip with some wire cutters a few millimeters at a time.   The Axial ratio will be constantly changing.  You can, with some experimenting, find the CP point, but statistics are against you without any testing.  And the Kraus Formulas are about 3 dB Optmistic. Winding the helix on a plastic pipe creates all sorts of problems.   In free space the radio wave travels along the wire at about 95% the speed of light.   When you wrap the wire on a plastic tube, the velocity factor is now about 60%.The effective length and turns ratio is completely different from the calculations.    And darn near impossible to even simulate   What is the dielectric constant of that plastic you got at the hardware store?    And If you did look up the Er, that value was measured at 1kHz, not 1269 MHz!    So unless you actually measured the Er at 1269 MHz, your CST, HFSS, OPENEMS, etc simulation is not valid. Sam, G4DDK was the first to measure the effects of using just one dielectric boom with the helix winds attached directly to the boom.   i.e. one boom and the helix turns attached to the boom at their 12 O'clock position.The dielectric effects of the boom tilts the beam in the direction of the boom.and really reduces the gain of long helix antenna.                The NASA way, central boom and spokes to support the helix is by far the best way to go. 73  Kent  WA5VJB

On Sunday, February 28, 2021, 01:39:25 PM CST, on4cjq@telenet.be wrote:

Build one myself for 23cm years ago on 1268Mc. 2*19el fixed RHCP. The tricky part was the DR environment because spacings are small on 23cm. Made it with 1/4L mechanical spacing. It never lead me dwn, worked beter then my 30t helix. I hope my 4pol switch for this crossyagi will be finished in a month or 2, but busy with building µwave EME setup. Maybe i will try it first with my 70cm 4pol switch, but this will have more loss.

I've never seen commercial crossyagis for 23, but WIMO used to have helix antennes for 23c,and 13cm, or try to make them yourself.

best 73's

Jerry,ON4CJQ

----- Oorspronkelijk bericht ----- Van: "amsat-bb" amsat-bb@amsat.org Aan: "amsat-bb" amsat-bb@amsat.org Verzonden: Zondag 28 februari 2021 11:41:35 Onderwerp: [AMSAT-BB] WTB: Circular Polarized Yagis for 1.2/2.4 GHz

Trying to locate a good source for these. M2 doesn't have these.  Ideas pls?

73/Ed NI6S

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You're almost tempting me to buy some of the fancier 3D printer filaments with known dielectric values. https://www.preperm.com/webshop/product/preperm-3d-abs-%C9%9Br-3-0-filament/

*Dielectric constant* Loss tangent *2.4 GHz* *22 GHz* *60 GHz* *2.4 GHz* *22 GHz* *60 GHz* PPE260 2.60 2.60 2.58 0.0009 0.0022 0.0025 PPE300 3.00 3.00 2.99 0.0009 0.0022 0.0025 PPE320 3.20 3.20 3.19 0.0009 0.0024 0.0026 PPE350 3.50 3.50 3.49 0.0009 0.0024 0.0026

The main reason I think I'd want to try helix on a pipe or 3D printed cylinder, is more because you can use flat copper tape, as I understand it should increase the bandwidth if it's done right (big if?). I did get bored one evening and at least tried to print the tallest helix I could make on my printer a few weeks ago, but I still need to get around to finishing the SMA connection feed.

I really need more excuses to buy one of those nanoVNAs anyways.

regards,

Jordan

KF5COQ

On Sun, Feb 28, 2021, 13:03 KENT BRITAIN wa5vjb@flash.net wrote:

Hi Jerry

I have taken an antenna range to over 60 conferences. And done quite a bit or work with Helix antennas at my lab. Of the 100 or so Helix's I have tested, only about 10% were circularly polarized. That's right, only about 1 in 10. I have proven many many times, HAMS CANNOT BUILD CP HELIX ANTENNAS!

It is amazing how a Helix Antenna can have an Axial Ratio of over 20 dB. That's about the same axial ratio as you get from many Yagi's. The few helix's that worked were usually built by a professional in the field.

Unless you have actually tested your Helix on a range, the chances are about 9 out of 10 is it not CP (Yes, it is a valid statement that all antennas are ellipticaly polarized, CP and Linear are just special cases.).

As an example, the wave comes down the helix, hits the tip, them reflects as a standing wave on the helix structure with an opposite CP sense. You can put a helix antenna on an antenna range, then start trimming the tip with some wire cutters a few millimeters at a time. The Axial ratio will be constantly changing. You can, with some experimenting, find the CP point, but statistics are against you without any testing.

And the Kraus Formulas are about 3 dB Optmistic.

Winding the helix on a plastic pipe creates all sorts of problems. In free space the radio wave travels along the wire at about 95% the speed of light. When you wrap the wire on a plastic tube, the velocity factor is now about 60%. The effective length and turns ratio is completely different from the calculations. And darn near impossible to even simulate What is the dielectric constant of that plastic you got at the hardware store? And If you did look up the Er, that value was measured at 1kHz, not 1269 MHz! So unless you actually measured the Er at 1269 MHz, your CST, HFSS, OPENEMS, etc simulation is not valid.

Sam, G4DDK was the first to measure the effects of using just one dielectric boom with the helix winds attached directly to the boom. i.e. one boom and the helix turns attached to the boom at their 12 O'clock position. The dielectric effects of the boom tilts the beam in the direction of the boom.and really reduces the gain of long helix antenna.

The NASA way, central boom and spokes to support the helix is by far the best way to go.

73 Kent WA5VJB

On Sunday, February 28, 2021, 01:39:25 PM CST, on4cjq@telenet.be wrote:

Build one myself for 23cm years ago on 1268Mc. 2*19el fixed RHCP. The tricky part was the DR environment because spacings are small on 23cm. Made it with 1/4L mechanical spacing. It never lead me dwn, worked beter then my 30t helix. I hope my 4pol switch for this crossyagi will be finished in a month or 2, but busy with building µwave EME setup. Maybe i will try it first with my 70cm 4pol switch, but this will have more loss.

I've never seen commercial crossyagis for 23, but WIMO used to have helix antennes for 23c,and 13cm, or try to make them yourself.

best 73's

Jerry,ON4CJQ

----- Oorspronkelijk bericht ----- Van: "amsat-bb" amsat-bb@amsat.org Aan: "amsat-bb" amsat-bb@amsat.org Verzonden: Zondag 28 februari 2021 11:41:35 Onderwerp: [AMSAT-BB] WTB: Circular Polarized Yagis for 1.2/2.4 GHz

Trying to locate a good source for these. M2 doesn't have these. Ideas pls?

73/Ed NI6S

---

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