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# ? gamma for a home-made 70cm 6-element yagi ? - RF Cafe Forums

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Below are all of the forum threads, including all the responses to the original posts.

 Post subject: ? gamma for a home-made 70cm 6-element yagi ? Posted: Mon May 30, 2005 8:09 pm
 Lieutenant

Joined: Mon May 30, 2005 7:51 pm
Posts: 1
 hi, with a 35" wood stick and 6 pieces of 3/32 welding rod a 70 cm yagi was made. using the AD8302 eval bd to check the reflected energy thepeak Vg was for 429 MHZ. the open end of the DE was trimmed at Fin=433.9 M until the same peak Vg was gotten. the new peak was at F=433.4 this is close enough to 433.9. the gamma was calculated byVg=928 at no input signals to the 8302 and Vg=1447 mV at its peak.gamma = (1447-928) / 30 = 17.3 (it's really a minus ). for a VSWR somewhere between 1.22 and 1.43.my question is for those of you who have too made your own yagiand measured its gamma ... what did you get ?and do you know what is a ball-park gamma for commercial yagis. previous tests of gamma with the 8302 used a string of VAT's on oneinput to make the Vg = 900 mV. but i was getting this funny compression with each add'l VAT dBm unit. until i figured the VAT's themself wereadding up a significant insertion loss compared to the add'l return lossi was trying to achieve. anyway, now i simply utilize the beauty of this 8302 device by letting the A & B inputs be un-equal and using the Vg output as the experimental data. then divide whatever it is by the slope of 30mV/dBm to get a number for ret loss. easy as pie this way

Posted  11/12/2012
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