T Plate vindicated ..well sort of ...

[Vipersan]

Hi friends ..
As some of you may be aware ..I have been singing the praises of my polyethylene T plate recently ..
Llew ..even made one up ..but saw no appreciable difference between its performance and the standard green/brown supplied dielectric plate ..
So ..I had to prove again to myself it realy does what it says on the tin ..

These are the 4 plates I used ..to test

A = Standard supplied plate (comes with the lnbf)

B = Heavy solid white Teflon ptfe T plate

C = polyethylene plate - same material as my T plate ..but without the T crossbar

D = My Polyethylene T plate ..


These where tried in turn first with SSTV @20 East

Then again on Pentagon Channel 1West

Here are the somewhat perplexing results...


A = Standard plate - SSTV 4.7DB (Picture) - Pentagon 2.4 DB (no picture)

B = PTFE plate - SSTV 2.0 DB (no picture) - Pentagon 1.9DB (No Picture)

C = Short Polyethylense plate - SSTV 2.7 DB (No Picture) - Pentagon 3.0DB (No picture)

D = Poyethylene T plate - SSTV 5.5DB (Picture) - Pentagon 6.8DB - (Solid locked Picture)

Ok these tests where done on the Alco PF dish ...but even surprised me ..
Yes the T plate outperforms generally ...but look at the Pentagon result ...its bizzare at best ..
Almost as though its 'Tuned' to a specific range or range of frequencies ..
We all know that The AFN C band transmissions @1W are a law unto themselves anyway ...but without the T plate ..I simply couldn't view them ..

Can anyone explain whats going on here ..??
I suspect its a combination of superior dielectric material ..and the crossbars extension above the feed/focus ...and generally this improves signal capture ..but in some cases ....literally doubles and triples the signal arriving at the receivers front end ..

Thoughts opinions ..ideas ...in fact any theories are welcome ..

I dont believe its the dish thats incorrectly setup ...
Firstly the sstv results confirm almost identical results T ..and standard plates...
Also ..I've tried a simillar experiment on an 80cm ..offset dish ..and this too benefitted from the T plate ..

rgds
VS

appologies for any typos ..
My hands dont work too well today ..
;)

 

[nelson_b]

hi -
this is not a very scientific test -- as i,m just using my old vantage 22x signal indicators to measure the signals - and a portable t.v. to view the results of my tinkering
i find the vantage very sensitive to small increases in signal between 40 to 75 on strength and quality -- so its the best reciever i have for this kind of fine tuning .

i,v played around with some T plates before but they were teflon type of material and only upto 3.5 mm thick
and did not give good results .

this one i,m using is cut from a -- Polythene chopping board -- slightly rough surface 8 mm thick

i used Africa tv 3893 R as a test transponder as it was just locking a watchable signal 35 strength -- 40 Quality
between 4.00 and 6.00 this afternoon - here -- which was a good result / starting point anyway

from here on it gets puzzling and raises more questions ??--
the plate was made to fit snugly against the feed rings and project slightly beyond the front of the feed ,the board i bought was not quite wide enought to span the full width of the feedhorn .
i decided to pull the plate further foward in the throat and got a improved signal, peaked at around 23 - 24 mm of forward movement .

i then decided to add an extension to the front of the plate and taped a 50 mm piece of Polythene chopping board to the front and got a bit more signal improvement .

so heres the signal meter results -- and a picture of the plate as it sits giving the best results so far ?

strength -- quality

35 - 42 fully pushed in -- without the extension

40 - 65 pulled out -- without the extension

40 - 52 with extension and pushed fully in

55 - 82 pulled out and with extension

i have no time to try anything else now for a while, but it was interesting -- and i,m well pleased with the results
even though it looks very odd . - and i will buy another - "wider " board to make my next one from ,l.o.l.

i have left the setup like this for now to test on other sats -- a quick look at 1 west showed a notably improved signal on both the pentagon channel t.p. and the nile news t.p. without any adjustment needed -- all other plates i,v used needed to be adjusted to a compromise between these 2 transponders

regards -- nelson.b.

 

[Vipersan]

Thanks heaps for the tests Nelson ...

Another satisfied customer ;)

Looks like anyone making one will have to customise it for their setup ..

But I'm fairly conviced now ...that mine wasn't a fluke ..and it does work.
You have made me a very happy sataholic buddy

Remember ..the original I made was for a pf dish ..so I simply cut one I'd already made to fit the feed I had available..
..but lots of scope for futher experiments I think.
As said previously ...the fact that it requires minimal adjustment is a plus.

rgds all
VS

 

[Vipersan]

..Forgot to add Nelson ..
That should you decide to leave it in place ...it will of course keep the lnbf throat open to the elements ..
Not quite so important on a pf ...but an offset has the lnbf ...leaning backwards ..so rain will enter the throat ..
I've discovered that a decent sized tupperware bowl is almost totally transparent at Cband fequencies ..so you can use one as a hat to keep the rain out ..
rgds
VS

 

[nelson_b]

yes-- the cover i had over the old setup will not go over this huge plate -- so its got a swing bin liner over it for now -- l.o.l
until i find or construct something for it

cheers

 

[Channel Hopper]

..Forgot to add Nelson ..
That should you decide to leave it in place ...it will of course keep the lnbf throat open to the elements ..
Not quite so important on a pf ...but and offset has the lnbf ...leaning backwards ..so rain will enter the throat ..

Not if the dish is installed upside down on the mount

 

[nelson_b]

hi -
just to give the new plate setup another test on another "difficult " transponder -- i had a look at " Saba tv " on Yamal 49 east and again got a better than usual - good signal from that t.p. without any adjustment -
and a blind search revealed a weaker one - new to me -
3596 L DVB-S/MPEG-4 1850 5/6 -- GTRK Tula -- needed to put it through the spiderbox to see it as its MPEG-4 -- but no breakup on the picture
so good results across 3 sats so far
no time for any more today now

cheers --

 

[Vipersan]

O-no..No Fair Nelson ....No Fair

I can't even get a sniff of Yamal ..thanks to the position of that troublesome tree ..grrrr

Still ..I'm soooo happy its proving to be a useful addition to your Cband toolbox
rgds
VS

 

[nelson_b]

Not if the dish is installed upside down on the mount

a 1.8 motorised channel master mounted upside down -- that would be a fun project to take on -----

 

[nelson_b]

ok -
a new plate made today
this one differs from the last one - in that it is 9 mm thick not 8 and has a different surface pattern
but seems to be made of the same material

i made it the full width of the feed this time and and cut 23mm off the bottom of the T to compensate for the 23mm i was having to withdraw the other one to peak the signal -- so it now sits up against the feed -rings -- and does not go all the way down the l.n.b. throat.
and as i hoped has not lost any signal from doing this -- the length of the material ouside the feed is the same as the last one -- i started with it longer but had a poorer signal so cut it back

performance wise its exactly the same as the one i made before - but fits much better in the feed - and is in one piece this time -- l.o.l.

i,m glad i finaly got round to experimenting properly with this type of plate -- its giving me the best results i,v had up to now , with my Cband setup.

regards nelson.b.

 

[Vipersan]

Yep....and a thing I'd wanna see first hand ...lol



VS

 

[Vipersan]

ok -
a new plate made today
this one differs from the last one - in that it is 9 mm thick not 8 and has a different surface pattern
but seems to be made of the same material

i made it the full width of the feed this time and and cut 23mm off the bottom of the T to compensate for the 23mm i was having to withdraw the other one to peak the signal -- so it now sits up against the feed -rings -- and does not go all the way down the l.n.b. throat.
and as i hoped has not lost any signal from doing this -- the length of the material ouside the feed is the same as the last one -- i started with it longer but had a poorer signal so cut it back

performance wise its exactly the same as the one i made before - but fits much better in the feed - and is in one piece this time -- l.o.l.

i,m glad i finaly got round to experimenting properly with this type of plate -- its giving me the best results i,v had up to now , with my Cband setup.

regards nelson.b.

And the project goes from strength to strength..
;)

Good that you are trying different surface patterns ..
I sort of suspected that it wasn't so much crucial that it had the same surface pattern as mine ...so much as it doesn't want to be a smooth surface ...
I think I tried this once ..and even though it was polyethylene the results of a smooth plate for the same size and shape was somewhat poorer in performance.

might possibly be due to creating standing waves ..in phase... on the plate surface...or even dispersing anti-phase standing waves ...
rgds
VS

 

[pride21]

hi VS i made a tee plate with the diameter you have shown,i tested it against my home made plate which after about thirty plates is the best i have made,i started with rascom all the channels were the same exept afm which was less with breakup then as below.
1W all channels same including pentegon only ertu went from 50 upto 58 quality
5W all channels same exept dw-tv from 76 down to 70,ortb from 84 upto 88,dbs from 58 down to 52
18W grts 48 to no signal
22W congo same,atlantic from 68 to 72,cnn 60 to no signal.
24W ortm 30 to no signal
27W afn from 68 to 62,record africa from 60 upto 62,rtg from 64 down to 58
34W KNR 48 to no signal,RTI same
40W most channels were either up or down to a level of breaking up,canal tro went from 62 to no signal,rbn went from 66 to no signal,telepacifico went from 56 to no sig.
your plate is definitly better than the plate you get with the lnbf,your plate is either tuned to some channels but not others.
cheers

 

[Vipersan]

Hi Pride ...
As Nelson found out ..there is some adjustment to be had ..by pulling it out of the throat a little ..
..A sort of tuning method ..
Also ..he extended his plate (the T crossbar to make it stick out further ..)

But these mods were for his Offset dish setup ..

Try extending the plate itself by taping an offcut to the front of the T crossbar ..
you never know ..

Are you using it on a PF or offset ?
As a final note ...
The material that worked best for both of us is rough sided patterned polyethylene ...and must be at least 6mm thick ..
...The basic concept is there ..but I suspect the plates have to be sort of ..customised for individual setups ..
Thanks for reporting back ...all info is useful and appreciated..
rgds
VS

 

[pride21]

hi VS yes i did try and bring the plate out but there was no difference,the polyethylene i got is 6.5mm thick with both sides rough.its classed as a offset but behaves like a PF with normal scaler.ill try to extend the T piece and see what happens.

 

[Vipersan]

hi VS yes i did try and bring the plate out but there was no difference,the polyethylene i got is 6.5mm thick with both sides rough.its classed as a offset but behaves like a PF with normal scaler.ill try to extend the T piece and see what happens.

All I can do is wish you luck m8 ..

If the dish is actually an offset ...If convinced you'd benefit from a conical feed ..

That might even explain the wide variations you are seeing ..
Any chance of a photo of the setup Pride ?
rgds
VS

 

[pride21]

Hi VS here is a picture of my dish,i have tried a connical scaler feed reception gets worse and i lose channels its much stronger with PF scaler,its a shame because the T-piece looks promising

 

[Captain Jack]

Hey Nelson, nice TV you have

 

[nelson_b]

Hey Nelson, nice TV you have

hi - Captain Jack -
you refer to post 10 i guess --

its almost a collectors item by now i think - l.o.l.

its very hardy - its lived outdoors 24/7 for the past 8 months in the open fronted box you can see in pic 1 --

i have a similar one ready to replace it when it finaly fails - pic 2

cant bear to throw away anything that still works -
yorkshire upbringing you see --

regards nelson.b.

 

[Captain Jack]

That's old Japanese quality that is! No idea what "National" is, though, but I like the manual channel selector knob!