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

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

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
Location: colorado
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 the
peak 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 by
Vg=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 yagi
and 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 one
input 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 were
adding up a significant insertion loss compared to the add'l return loss
i 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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