T plate ...Open T ....Hybrid T..

[Channel Hopper]

many c-band Freaks in Germany are using this Feed - maybe also good for you?

_hxxx://www.satshop24.de/satshop24_s/waveguide_polaraiser_av_comm_mit_polarai.html_

I'm surprised the cost is E350 for a C band unit, but anyone can make hay while the sun is shining.

The issue for VS will be finding the exact boresight for the feed, (and keeping it centred at all satellite positions), plus - justifying the cost of it when the 'perfected' T-plate design comes so close to the reception characteristics.

 

[bonou2]

hi @remlap
I'm sorry but LNB Star Sat,is an attempt
good for satellites with strong signal
not recommend to anyone )(-red
send an email to sonicolor and ask if you send in Wales

 

[Vipersan]

I'm surprised the cost is E350 for a C band unit, but anyone can make hay while the sun is shining.

The issue for VS will be finding the exact boresight for the feed, (and keeping it centred at all satellite positions), plus - justifying the cost of it when the 'perfected' T-plate design comes so close to the reception characteristics.

..Thats the problem CH ..
I'd say the basic design of the T is as close as I can get to perfect for Circular depolarisation..
Confirmed by others to give that 2 db gain ...as the claims of the servo motorised feed claims 3db gain ...this is indeed close ..
The problem is that making a plate that doesn't require physical removal for Linear signals is as we know ..impossible ..so it would have to be a compromise.
Thus a reduction in that 2db advantage on circular in favour or a couple of db gain on linear ...with the plate in situe.
Now ..if only I can come up with remote controlled teleportation..
Press a button ..and it it vanishes from the lnb throat ...and materialises in my cupboard.
;)

On a more plactical note ..I did wonder about the propeties of lcd ..
A theoretical plate which remains in place ..and transparent with no voltage applied..
Apply a voltage and the plate becomes opaque ...(basically polarized itself)
I wondered if this 'magical' dissappear and reappear act would actually affect signal polarity..
Perhaps not ...but it was just an idea ..and sadly I don't know the properties of such materials ...nor can I manufacture one in the back yard ..to test.

Maybe not such a stretch of the imagination as light and radio waves are part of the same EM spectrum...just at opposite ends..

rgds
VS

 

[remlap]

hi @remlap
I'm sorry but LNB Star Sat,is an attempt
good for satellites with strong signal
not recommend to anyone )(-red
send an email to sonicolor and ask if you send in Wales

Thanks mate, does anyone at sonicolor to your knowledge read English?

 

[bonou2]

use google translator english-spanish

 

[remlap]

Thanks mate I've just checked the cost of shipping and at €22 I can't justify another €40+ on an LNB

 

[Vipersan]

OK ...just got home from work ..and the first thing I did after my cup of T ...A question of priorities...was to remove another 1cm of poyethylene from the open section of the T ..so now only 1cm of complete cross section plate is actually inserted inside the LNB throat.
You'd think it would no longer de-polarise circular signals..
You'd be wrong ..
..as I said ..I'm convinced you can de-polarise _outside_ the lnb itself..
So more proof and this process of comparison is a bit more scientific.

First the dish was moved to 1 West ..and the Pentagon Channel selected ..
The 3 plates were readied ...A full T ...An Open T ..and a commercial dielectric plate supplied with a new lnbf.
OK ..
The commercial plate was tried ..and a signal level of 5.1 db photgraphed..
Next ..a Full T plate ..
6.9db..which is a bit of a record for me..but maybe conditions were good today..
Next the Open T of which only 1cm of full cross section polyethylene is physically inside the lnb throat ..
6.3 db ...
So thats a drop of 0.6db on a full T .

Next the dish was swung over to 37.5 W ...and silverbird ...and then Metro were tested ..
First with no plate at all ..
Silverbird (Locked) 8.8db ..
Metro (Locked) 13 db

then the Open T was inserted
Silverbird (Not Locked ) 6.3db
Metro TV (Locked) 11.2 db

So it looks like the open T continues to do its job on circular signals with a roughly a0.6 to 1db drop in gain
Whereas Allowing access to linear with the Open T in place reduces signal by approx 2 to 3 db as expected..
This fact means its useless I guess ...except on BUD type dishes ..
But ...it does appear to work ..and is reasonably consistant.
No use for signal that are threshold ..but high power signals ...maybe very useful as a cheap way to achieve both circular and linear with a single plate inserted.
There are variations with regards to linear ..for example Jamaica TV at 55W ...is only reduced from 6.5db to 4.5 db..
So I assume frequency modulation type and symbol rate etc ..also play a part.
I hope someone else tries this as its inexpensive ..and the more info the better.

In Short you stand to lose approx 2 db on linear signals ...and 1db on circular ...with the OPen T in place..
rgds
VS
Here are the pics

 

[pride21]

hi VS just seen your article on plates,been busy doing my dish extentions,anyway here is a close up of the av-comm set up.

 

[Channel Hopper]

On a more plactical note ..I did wonder about the propeties of lcd ..
A theoretical plate which remains in place ..and transparent with no voltage applied..
Apply a voltage and the plate becomes opaque ...(basically polarized itself)
I wondered if this 'magical' dissappear and reappear act would actually affect signal polarity..
Perhaps not ...but it was just an idea ..and sadly I don't know the properties of such materials ...nor can I manufacture one in the back yard ..to test.

Maybe not such a stretch of the imagination as light and radio waves are part of the same EM spectrum...just at opposite ends..

rgds
VS

The properties of microwaves are similar to that of light, both being electromagnetic. Since various materials can be used to convert one form into another in the optical spectrum, there should be something similar for the lower wavelengths of signals from satellites.

I was working on (number of) Faraday rotator designs back in the early/mid 90's using Gaussian coils (not dissimilar to that used in particle beam technology) to focus microwaves into the LNB without the use of a scalar plate, but this was at low Ku band (8-11 GHz).
The results were measurable, but could not be maintained across the whole spectrum at a fixed voltage.


Application efficiency was offset by the use of energy in keeping the current flowing as well, which meant it was also uneconomical when compared to - say - adding a few extra panels onto the dish.

In a similar vein the ferrite polarisers (horrible lossy things) that were used throughout the 90's on satellite equipment required adjustment at each frequency received by the receivers tuner. Coil technology means the equipment remains outside the direct path of the incoming microwaves (at least on an offset dish) and so the direct loss to the incoming signal is zero.


If you search for gyrotropic waveguide or permittivity you might find something of value, the following should start you off though


_http://www.sccs.swarthmore.edu/users/08/ajb/tmve/wiki100k/docs/Magneto-optic_effect.html