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KB1DTB

GP Patch antenna polarity?

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It's linear. The up arrow on the plans indicates the orientation for vertical polarity. Rotate 90 degrees for horizontal polarity.

If in doubt, just try both orientations at the field to see which give the best overall range.

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Hello mister RC Cam,

Do you know the beam width?

I have seen some commercial patch units listed as dual linear. How do they do that?

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It's about 80 degrees (-3dB point). In practical application, you can often fly within 160 degrees (at moderate distances there is sufficient gain to allow this).

This white paper will explain how dual linear polarization is achieved (see introduction paragraphs): http://www.ctsystemes.com/zeland/publi/166.pdf

Some dual polarized patches, and their circularly polarized cousins, rely more on marketing than science. The beam plots will identify those that are true to their claims.

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Thank you for the replies.

I will be making one of your GPP for the receiver and one turnstile for the transmitter. I was trying to calculate the turnstile size based on frequency length for 910mhz but the dimensions do not match the PC Electronics website if calculated out. Should I scale everything up from the PC Electronics website or go by the calculated sizes?

Did they adjust the sizes based on response?

I understand the velocity factor now. If it takes longer for the wave to travel thru the coax you need to shorten the coax based on the Vf so it's length will equal the lambda in free air.

Thanks,

Brian

Edited by KB1DTB

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Cyber-Flyer has extensive experience with Turnstiles. Maybe he will chime in with some advice.

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That would be great! You guys here have so much more experience in this field. I am very greatful for any and all help.

I need to know if the total length of each dipole is 1/2 lamda or do you add the space between the two 1/4 wave poles to the overall dimension or subtract it from the length of the 1/4wave poles so the overall length would be exactly 1/2 lamda.

Did that make any sense?

Thanks Mr. RC CAM

Edited by KB1DTB

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I was trying to calculate the turnstile size based on frequency length for 910mhz but the dimensions do not match the PC Electronics website if calculated out.

The turnstile elements size for 910 MHz should be 2400/910 times longer than for 2400 MHz - this is using simple scaling law between frequency and wavelength. Sometimes slight deviation in length can improve antenna but this will require precise measurement equipment. I suggest using simple scaling law which results in 85mm length for each of four elements of turnstile antenna.

I am not familiar with PC Electronics article, can you give me a link?

Regards,

Val.

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