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

Re: R: Circular patch behaves linear



Dom:
I'm VERY interested in the plots you mention.  Thanks & 73,
jim
wb4gcs@amsat.org


i8cvs wrote:
> ----- Original Message -----
> From: Anthony Monteiro <aa2tx@attbi.com>
> To: Charles Suckling <charles.suckling@ntlworld.com>; William Leijenaar
> <pe1rah@hotmail.com>; <amsat-bb@AMSAT.Org>
> Sent: Monday, June 23, 2003 4:11 PM
> Subject: Re: [amsat-bb] Circular patch behaves linear
> 
> 
>>It also appears that the dish significantly affects the patch as I noticed
>>the return loss goes all over the place as the patch is moved around the
> 
> focus.
> 
>>It would be interesting to hear if anyone did any polarization or return
> 
> loss
> 
>>measurements on a prime focus dish with a G3RUH patch installed. The G3RUH
>>patch is more rigidly constructed so this would help but I would be
> 
> surprised
> 
>>if there was no detuning from the dish reflecton.
>>
>>Any comments?
>>
>>73,
>>Tony AA2TX
>>
> 
> Hi Tony AA2TX,
> 
> I have built one patch of K3TZ and four of G3RUH designe all for 2400 MHz
> and i have adjusted both for the best compromise of circularity and return
> loss in my lab with the patch alone looking at  free space out of the
> window.
> 
> Without to go in performance comparison i have seen the following:
> 
> Suppose the return loss with the patch alone looking at free space is 25 dB
> and circularity - 1dB
> 
> When i place the patch in to a prime focus dish than the return loss changes
> greatly as i move the patch up and down  around the focal point but as soon
> the focal point fall in the exact phase center of the feed than the return
> loss become again exactly 25 dB as in the lab.
> 
> For the G3RUH patch i found that the phase center fall exactly over the
> outer surface of the active element.
> 
> If you measure the return loss before in the lab with the patch alone
> looking at free space and if you readjust the patch position at the dish for
> the same return loss around the focal point than you have reached the exact
> position for the phase center of the feed.
> 
> If you get the same return loss with the active element positioned at the
> geometrical focal point it is an indication of a good circularity separation
> because the feed is LHCP and the dish reflects RHCP energy to the feed.
> 
> If the feed has a good isolation between RHCP to LHCP than the energy
> received back by the feed from the dish is very small and return loss is
> small affected.
> 
> For return loss and circularity measurements i have used a rotatable 2400
> MHz dipole with balun + a HP8690B Signal Generator + HP11692D Dual
> Directional Coupler and HP 8555A Spectrum Analyser
> 
> If any one is interested on pattern diagrams,circularity diagrams and pics
> of the above test set up please send me a  message and i will replay to all
> ASAP
> 
> 73" de i8CVS Domenico
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> 
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home