Log in
Register
Menu
Log in
Register
Home
What's new
Latest activity
Authors
Forums
New posts
Search forums
What's new
New posts
Latest activity
Members
Current visitors
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Forums
Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
KA Band section
Dishes for Ka-band: what works - what doesn't?
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="s-band" data-source="post: 1003676" data-attributes="member: 407744"><p>John, what you are trying to would be difficult at the best of times. It is quite likely that signals are getting around the dish by multiple reflections, knife edge diffraction or a combination of those and other factors. Tests like this would normally be done in an anechoic chamber and are still difficult. Really, you need a section of the dish on the wall of a screened enclosure to be able to measure the transparency of the sample. Even then it is hard to ensure that you don't have leakage around the sample.</p><p></p><p>The feed you are using is circular on Ka isn't it? Your TX is from a dipole - linear polarised. That is good in some respects as the RX feed will be insensitive to the actual angle of the linear polarisation. If you use linear on both ends you should rotate for max signal. You still won't know if it is going through or around. If your test antenna is only 10mm from the surface, it will be in the near field where effects may not be what you expect.</p><p></p><p>Using foil to confine the field might not be doing what you think either. You can get more weird effects where the foil forms a slot (as in slot antenna). Copper tape with conductive adhesive would be better but I'd be inclined to use absorber as that will minimise reflections.</p></blockquote><p></p>
[QUOTE="s-band, post: 1003676, member: 407744"] John, what you are trying to would be difficult at the best of times. It is quite likely that signals are getting around the dish by multiple reflections, knife edge diffraction or a combination of those and other factors. Tests like this would normally be done in an anechoic chamber and are still difficult. Really, you need a section of the dish on the wall of a screened enclosure to be able to measure the transparency of the sample. Even then it is hard to ensure that you don't have leakage around the sample. The feed you are using is circular on Ka isn't it? Your TX is from a dipole - linear polarised. That is good in some respects as the RX feed will be insensitive to the actual angle of the linear polarisation. If you use linear on both ends you should rotate for max signal. You still won't know if it is going through or around. If your test antenna is only 10mm from the surface, it will be in the near field where effects may not be what you expect. Using foil to confine the field might not be doing what you think either. You can get more weird effects where the foil forms a slot (as in slot antenna). Copper tape with conductive adhesive would be better but I'd be inclined to use absorber as that will minimise reflections. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Satellite TV receivers & systems support forums
DISH SETUP: Single sat, Multi-Sat & Motorised
KA Band section
Dishes for Ka-band: what works - what doesn't?
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
Accept
Learn more…
Top