[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

# Re: 435 offset yagi phasing

• Subject: [amsat-bb] Re: 435 offset yagi phasing
• From: "kc6uqh" <kc6uqh@xxxxxxx>
• Date: Fri, 28 Dec 2007 18:55:50 -0800

```Andrew,
Yes that is correct with one exception that a 50 ohm, 1/2 wave section needs
to be inserted for the opposite rotation in one antenna. This is switched in
and out with a coax switch or relay. The 1/4 wave sections do the matching
and both offer the same delay so there is no phase difference to the
antennas. As the antennas are 1/4 wave offset one leads by 90 degrees.
adding a 180 degree delay will cause that antenna to lag by 90 degrees and
hence the opposite rotation.

Good luck with the project. Learning by doing is the best way!

Art,
KC6UQH
----- Original Message -----
From: "Andrew Rich" <vk4tec@people.net.au>
To: "Amsat-Bb@Amsat. Org" <amsat-bb@amsat.org>
Sent: Friday, December 28, 2007 3:25 AM
Subject: [amsat-bb] 435 offset yagi phasing

> Hi
>
> I have had good success with just one yagi of an offset crossed array I am
> building.
>
> http://wa5vjb.com/yagi-pdf/cheapyagi.pdf
>
> I will add the other elements shortly.
>
> I am not ready to tackle the phasing part.
>
> I hope I have this right.
>
> 1. The yagi's are offset, by 90 degrees so that is the offset already.
> 2. Both yagis's should then have the same length of coax coming from each
> one.
> 3. Both yagi's will require a 1/4 wavelength of 75 ohm coax for each feed.
> 4. Remebering that the velocity factor is 2/3 in coax cable, or the speed
> of
> light 200 instead of 300.
> 5. Both 75 ohm feeds then join at a tee, the result of the 50 ohm antenna
> and 70 ohm feed giving around 120 ohm
> 6. By tee'ing the two together, this should present around 50 ohm,
> required
> for the main feedline.
>
> Does that sound right ?
>
> ( 200/435 MHz ) /4 = 11.49 cm for each feed to the tee junction of 75 ohm
> cable.
>
>
> ----------------------------------------------------------------------------
> Andrew Rich VK4TEC
> _______________________________________________
> Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

_______________________________________________
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author.
Not an AMSAT-NA member? Join now to support the amateur satellite program!
Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

```

AMSAT Home