Brian, VA3HJ's answer is correct but incomplete. The 75 ohm cables must each be 1/4 wavelength long. The actual value needed for the phasing cable characteristic impedance is 70.7 ohms. Essentially, taking a 1/4 wavelength of  70.7 ohm cable will transform 50 ohms resistive to 100 ohms resistive. Then take the two 100 ohm impedances and parallel them to get back to 50 ohms where you can use any length of 50 ohm cable to get to the transmitter.  FredK9SO

"The characteristic impedance of cables must be such that the proper length of cable will provide an impedance transformation from 50 ohms at the antenna end to 100 ohms at the connecting point. A quarter wavelength of cable that provides the proper characteristic impedance can transform the 50-ohm impedance of each antenna to 100 ohms at the connection point.  The characteristic impedance of cables L1 and L2 must be 70.7 ohms. Because 75-ohm cable is readily available, it is generally used to make the phasing harness. Standard 50-ohm impedance cable is used for cable L3, which extends from the connection point to the transceiver."

On Monday, November 29, 2021, 05:42:55 AM EST, V Chu ve3xre@gmail.com wrote:

Brian  You can use 2 75ohm cable to connect each antenna and join them with a coaxial splitter then 50ohm cable to your Transmitter.

de VA3HJ mobile On Sun., Nov. 28, 2021, 23:23 Brian Clark decompudoc@gmail.com wrote:

Hello Everyone, I have two Dual-Band 2 Meter/440 Yagi's  that I would like to use on a Rotator, with one in the vertical polarity and one in horizontal. Is there a phasing circuit or system that someone can recomend to allow both of these antennas to coexist on one coax input to my radio? Thanks, BrianKF6FES -----------------------------------------------------------

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I was waiting for him to clarify if he wants more info.

Thanks for the clarification.

de VA3HJ mobile

On Mon., Nov. 29, 2021, 06:33 Fred Glenn wa9mvz@yahoo.com wrote:

Brian, VA3HJ's answer is correct but incomplete. The 75 ohm cables must each be 1/4 wavelength long. The actual value needed for the phasing cable characteristic impedance is 70.7 ohms. Essentially, taking a 1/4 wavelength of 70.7 ohm cable will transform 50 ohms resistive to 100 ohms resistive. Then take the two 100 ohm impedances and parallel them to get back to 50 ohms where you can use any length of 50 ohm cable to get to the transmitter.

Fred K9SO

"The characteristic impedance of cables must be such that the proper length of cable will provide an impedance transformation from 50 ohms at the antenna end to 100 ohms at the connecting point. A quarter wavelength of cable that provides the proper characteristic impedance can transform the 50-ohm impedance of each antenna to 100 ohms at the connection point. The characteristic impedance of cables L1 and L2 must be 70.7 ohms. Because 75-ohm cable is readily available, it is generally used to make the phasing harness. Standard 50-ohm impedance cable is used for cable L3, which extends from the connection point to the transceiver."

On Monday, November 29, 2021, 05:42:55 AM EST, V Chu ve3xre@gmail.com wrote:

Brian

You can use 2 75ohm cable to connect each antenna and join them with a coaxial splitter then 50ohm cable to your Transmitter.

de VA3HJ mobile

On Sun., Nov. 28, 2021, 23:23 Brian Clark decompudoc@gmail.com wrote:

Hello Everyone,

I have two Dual-Band 2 Meter/440 Yagi's that I would like to use on a Rotator, with one in the vertical polarity and one in horizontal.

Is there a phasing circuit or system that someone can recomend to allow both of these antennas to coexist on one coax input to my radio?

Thanks,

Brian KF6FES

---

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I think Different 75ohm cable will have different result.

I only use VHF as my reference for initial cutting. And you'll know if you need to make them longer or shorter once it's installed by tuning frequency up and down with SWR meter.

de VA3HJ mobile

On Mon., Nov. 29, 2021, 10:41 Brian Clark decompudoc@gmail.com wrote:

This is all helpful information Everyone!

I have many 75 ohm t’s, will that work for coupling the antennas?

Also, I assume the 1/4 wave measurement will need to be addressed differently for each band?

Thanks,

Brian KF6FES

On Nov 29, 2021, at 7:31 AM, V Chu ve3xre@gmail.com wrote:

 I was waiting for him to clarify if he wants more info.

Thanks for the clarification.

de VA3HJ mobile

On Mon., Nov. 29, 2021, 06:33 Fred Glenn wa9mvz@yahoo.com wrote:

...

Brian, VA3HJ's answer is correct but incomplete. The 75 ohm cables must each be 1/4 wavelength long. The actual value needed for the phasing cable characteristic impedance is 70.7 ohms. Essentially, taking a 1/4 wavelength of 70.7 ohm cable will transform 50 ohms resistive to 100 ohms resistive. Then take the two 100 ohm impedances and parallel them to get back to 50 ohms where you can use any length of 50 ohm cable to get to the transmitter.

Fred K9SO

"The characteristic impedance of cables must be such that the proper length of cable will provide an impedance transformation from 50 ohms at the antenna end to 100 ohms at the connecting point. A quarter wavelength of cable that provides the proper characteristic impedance can transform the 50-ohm impedance of each antenna to 100 ohms at the connection point. The characteristic impedance of cables L1 and L2 must be 70.7 ohms. Because 75-ohm cable is readily available, it is generally used to make the phasing harness. Standard 50-ohm impedance cable is used for cable L3, which extends from the connection point to the transceiver."

On Monday, November 29, 2021, 05:42:55 AM EST, V Chu ve3xre@gmail.com wrote:

Brian

You can use 2 75ohm cable to connect each antenna and join them with a coaxial splitter then 50ohm cable to your Transmitter.

de VA3HJ mobile

On Sun., Nov. 28, 2021, 23:23 Brian Clark decompudoc@gmail.com wrote:

Hello Everyone,

I have two Dual-Band 2 Meter/440 Yagi's that I would like to use on a Rotator, with one in the vertical polarity and one in horizontal.

Is there a phasing circuit or system that someone can recomend to allow both of these antennas to coexist on one coax input to my radio?

Thanks,

Brian KF6FES

---

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https://www.qsl.net/dk7zb/Cross-Yagi/crossyagi.htm

From: Nico Janssen hamsat@xs4all.nl Sent: Monday, November 29, 2021 4:52 AM To: Brian Clark decompudoc@gmail.com; amsat-bb@amsat.org Subject: [AMSAT-BB] Re: Phasing Cable/System - 2 Dual-Band Yagi's

Brian,

The only correct way to do this is using a hybrid ring coupler. That'll give you 50 Ohms on all ports and you don't lose half of your signals.

73, Nico PA0DLO

On 29-11-2021 05:22, Brian Clark wrote:

Hello Everyone,

I have two Dual-Band 2 Meter/440 Yagi's that I would like to use on a Rotator, with one in the vertical polarity and one in horizontal.

Is there a phasing circuit or system that someone can recomend to allow both of these antennas to coexist on one coax input to my radio?

Thanks,

Brian

KF6FES

-----------------------------------------------------------

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No he didn't. He asked how to feed them with a single co-ax. He didn't mention phasing. He said they were mounted one horizontal and one vertical.

The problem with phasing lines is that he said they are dual band antennas. If they are single feed, your phasing lines will not work on both bands.

On 29/11/2021 08:38 Fred Glenn wa9mvz@yahoo.com wrote:

Mr. Gunn,

He specifically asked how to phase them. Using a relay to switch between them is an obvious solution that he apparently didn't want to use.

If you want to combine two 50 ohm loads into one, my suggestion is correct. Not gibberish. It is a variation of the Wilkinson combiner/splitter. Read up on it.

Fred K9SO

On Monday, November 29, 2021, 08:20:15 AM EST, Nigel A. Gunn G8IFF/W8IFF nigel@ngunn.net wrote:

Unfortunately, Brian, you're getting mostly gibberish that you didn't ask for.

...

On 28/11/2021 23:22 Brian Clark decompudoc@gmail.com wrote:

Hello Everyone,

I have two Dual-Band 2 Meter/440 Yagi's that I would like to use on a Rotator, with one in the vertical polarity and one in horizontal.

Is there a phasing circuit or system that someone can recomend to allow both of these antennas to coexist on one coax input to my radio?

Thanks,

Brian KF6FES ----------------------------------------------------------- Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/amsat-bb@amsat.orgTo unsubscribe send an email to amsat-bb-leave(a)amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org

Nigel A. Gunn, ///shoulders.outwards.resolutions tel +1-937-971-0366 Amateur Radio G8IFF W8IFF and GMRS WRBV701, e-mail nigel@ngunn.net www http://www.ngunn.net

---

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Nigel A. Gunn, ///shoulders.outwards.resolutions tel +1-937-971-0366 Amateur Radio G8IFF W8IFF and GMRS WRBV701, e-mail nigel@ngunn.net www http://www.ngunn.net

Let's try to make this more clear...

Let's assume that the satellite is not transmitting circularly polarized (CP), which is true of nearly all. So your goal is to enable you to avoid fades as the satellite rotates and the linear polarization changes direction.

As have been mentioned here there are two choices: A CP antenna or switching from horizontal to vertical. In both cases with Yagis, you need a vertical and a horizontal set of elements. CP has the advantage that you don't have to switch--it works regardless of the direction of the incoming linear polarization and requires no relay, nor relay coil power. (Some people, including one of my best ham friends, swear by the ability to switch the CP antenna from right hand to left hand circular. I am not one of those when working linear satellites :-) ) To make a CP antenna, many have described the required coax length and impedance. I have not seen this said, but I believe that the crossed elements of the yagi also have to be a specific distance apart and at different distances, the coax length will need to be different. (I'm no expert here...I just bought an LEO Pack).

The other choice is to have a coax relay that will switch from horizontal to vertical polarity. The advantage is that it is simpler...the cable lengths and locations of the elements are less "fussy". The disadvantage is the opposite of the above: You have to manually switch back and forth to find the best polarity and you need power in some form out at the antenna to drive the relay coil.

I hope this helps. There are obviously two different ideas going on in this thread, so I wanted to try to sort them out.

73,

Burns WB1FJ