Dielectric plate ?

[pride21]

hi nelson_b i too played around with the plate,while ago i bought some slug tape from ebay its thin copper with sticky back which you peel off,any way i made a plate today waited for the rain to stop a bit rushed outside put in the lbnf then went to see any improvement,well i was surprised there was an increase of quality on most channels across sats,what surprised me more was ortm on 24.5w went from 30% quality to 46%,then i tried 18w before i tried grts which was breaking up,now it shot in with 56% quality,i think copper seems the answer.

 

[Vipersan]

hi nelson_b i too played around with the plate,while ago i bought some slug tape from ebay its thin copper with sticky back which you peel off,any way i made a plate today waited for the rain to stop a bit rushed outside put in the lbnf then went to see any improvement,well i was surprised there was an increase of quality on most channels across sats,what surprised me more was ortm on 24.5w went from 30% quality to 46%,then i tried 18w before i tried grts which was breaking up,now it shot in with 56% quality,i think copper seems the answer.

Hi Pride ..that slug tape is very similar to the stuff I've ordered ..
Sadly ..nothing in the post today ..
Hopefully I might get it tomorrow ...
Nice to know the adhesive copper is working.
rgds

 

[doktorofsat]

hi nelson_b i too played around with the plate,while ago i bought some slug tape from ebay its thin copper with sticky back which you peel off,any way i made a plate today waited for the rain to stop a bit rushed outside put in the lbnf then went to see any improvement,well i was surprised there was an increase of quality on most channels across sats,what surprised me more was ortm on 24.5w went from 30% quality to 46%,then i tried 18w before i tried grts which was breaking up,now it shot in with 56% quality,i think copper seems the answer.

Congratulation Pride21

I worked very hard on a polarmount today and I have no time at all to to make&test some dieldectric plate!!!

Your results are excelent !!! I know that 24,5W has a very low signal for me QTH , I never catch this bird with my 150cm PFA Dish!

I'll try to get some Cu foil to make a new plate and see the results

 

[Vipersan]

Hi friends ..
Still playing around with the foil version of the DOS plate..

I tried sandwiching the 54mm DOS plate against another 1mm section of the same material ...but this time cut into the same shape as my origional Polythene T shaped plate..

I'm using the Pentagon channel as my test channel ..

First I tried my origional polythene T ..
Signal 44 Quality 27
Perfect picture

Then I tried the 1mm T cut from a clear DVD case..

Signal 43 Quality unusable
No picture

Next the 54mm DOS foil on 1mm plate
Signal 44 Quality low 20's
No picture

Finally the DOS foil 1mm sandwiched against another the 1mm T shaped piece of plastic (the foil strips are in the centre of the sandwich)
Signal 44 Quality 24 >25 slightly varying

Perfect picture


I expect this design might be best for my setup as it still leaves room for improvement ..
Hopefully the copper strips will gain me a bit more ..when it eventually arrives.

Overall ..it does seem that I _have_ to extend the dielectric outside the lnbf throat in order to collect signal and get maximumum gain..whichever option I choose.
I suspect this might be a quirk of my particular dish as it was _never_ designed to use a feed horn or scalar rings.
rgds
VS

 

[nelson_b]

hi nelson_b i too played around with the plate,while ago i bought some slug tape from ebay its thin copper with sticky back which you peel off,any way i made a plate today waited for the rain to stop a bit rushed outside put in the lbnf then went to see any improvement,well i was surprised there was an increase of quality on most channels across sats,what surprised me more was ortm on 24.5w went from 30% quality to 46%,then i tried 18w before i tried grts which was breaking up,now it shot in with 56% quality,i think copper seems the answer.

thanks for the tips -- pride 21 --
this is getting addictive l.o.l. -- have no copper -- but did have some thin brass so again made another plate --

1 mm perspex -- thin brass sheet - on double sided tape --
same design as yesterday -taper to large then taper--
inserted all the way into the l.n.b.
very pleasing results

-- pentagon channel 1 west up from yesterdays tinfoil result of 40 strength 40 quality
to 55 strength - 82 quality --

not tried other sats as yet -- leave that till tommorow now i think

regards - nelson. b.

View attachment 25417

View attachment 25418

 

[Vipersan]

thanks for the tips -- pride 21 --
this is getting addictive l.o.l. -- have no copper -- but did have some thin brass so again made another plate --

1 mm perspex -- thin brass sheet - on double sided tape --
same design as yesterday -taper to large then taper--
inserted all the way into the l.n.b.
very pleasing results

-- pentagon channel 1 west up from yesterdays tinfoil result of 40 strength 40 quality
to 55 strength - 82 quality --

not tried other sats as yet -- leave that till tommorow now i think

regards - nelson. b.

View attachment 25417

View attachment 25418

Verrry Nice Work Nelson..
I'm suitably impressed
;)

 

[doktorofsat]

Nice results nelson_b


Please tell us the lenght of the striped from the 2 columns ad the distancw between them

 

[Channel Hopper]

hi nelson_b i too played around with the plate,while ago i bought some slug tape from ebay its thin copper with sticky back which you peel off,

The problem you are going to have is when the weather changes again, the heat of the reflected sunlight will quickly evaporate the adhesive.

Veroboard is the way to go.

 

[nelson_b]

Nice results nelson_b


Please tell us the lenght of the striped from the 2 columns ad the distancw between them

hi -- doktorofsat --

length of top stripe 10 mm
second stripe 11.5 mm
all other stripe lengths - as your original -
thickness of all stripes 3.5 mm
distance between stripes 5.5 mm

no time to check signals from other - transponder/ sats - untill tonight -

cheers nelson.b.

 

[pride21]

hi nelson_b thats a good result for pentagon channel,btw what is the quality of ertu channel.

 

[pride21]

hi doctorofsat we have to keep trying to improve on signal quality,my 1.4 offset is my limit here tho i would like a 1.8cm dish,do you get grts on your 1.5cm dish if so what quality.

 

[Vipersan]

The problem you are going to have is when the weather changes again, the heat of the reflected sunlight will quickly evaporate the adhesive.

Veroboard is the way to go.

Can't argue with your logic CH ...but I guess during the 'experimental' phase ...its definately the way to go.
So much easier to manipulate...
Once the perfect design emerges ...I would think either vero or better still ..an etched pcb would be the answer.
best rgds
VS

 

[Channel Hopper]

How do you know paxolin is not a dielectric ? , besides copper plate works very well at these frequencies, foil is not a great contender

Just to confirm

_http://www.holbourne.co.uk/index.php?option=com_content&task=view&id=22&Itemid=48

10G/50: Silicone glass grade with high temperature resistance. Can be used at 200°C. Excellent dielectric properties and low loss tangent. Conforms to BSEN60893 3-6 SIGC202 (BS3953 Type SI4 & SI5

 

[Satcom1]

I'm thinking it is the element array and not the board material. One mentioned 2mm not as good as 1mm. What if thinner?

This is an interesting thread. Experimentation is how Edison solved so many problems.

Sad to say we have no Circular C band in states everything we watch FTA is Linear. With the exception of one or two channels in the clear.

 

[Vipersan]

..Hi friends ..
I can't help feeling a little dissapointment..
My adhesive copper tape arrived today ..
Spent a few hours making up another plate .
And now have my DOS plate as efficient as i can get it..
It is now providing fairly uniform gain accross the C band spectrum on all sats tested but is only -equal- to my T shaped slab of polyethylene cutting board ..
Nothing I do will make it produce better results.
Both plates are effectively maxed out and equal.
I can only assume I was getting maximum possible results for my dish/lnb/plate combo to start with.
cest la vie..
I'm amazed at Nelsons result with the thin brass on perspex ..and can only assume he achieved resonance at that specific fequency..
Looking forward to seeing his results for other sats and other frequencies.
rgds 2 all
VS

 

[Channel Hopper]

Polyethylene is probably the best of most common dielectrics, and you had a decent quality slab.

However Nelson had an offset dish in the first place and a generic feed, I assume your feed is designed to work on the dish it was designed with.

If needed to persue this further I do have an early sample of mechanical circular depolariser waveguide (single polarity only) in the shed, but this will not fit on the voltage switching LNBs (LNBFs ?) you are using if combined with a feed.

PS - It adds a few cms to the length of the feedhorn system as well , so you will need additional clearance at the front, as well as longer cable runs.

 

[Vipersan]

Hi CH ..
In actual fact ..my Alcoa 1.8pf was never equipped to receive C band ..
in fact when I bought it 20 odd years ago ..it was fitted with a tube feed with an in line mechanical polarizer and an OMT with 2 single polarity lnbs for High and Low band.
The feedhorn was nothing more than an open ended KU waveguide ...with no scalar rings or actual horn of any kind.
The boss was never wide enough to accomodate a C band LNB ...so I had to redesign the mount boss in aluminium ...and everything thereafter to allow the cheapo pauxis polarity H/V switched lnbf to be retrofitted .
It could be argued that since I appear to require the dielectric material to extend out beyond the lnbf throat ..that it isn't correctly positioned at the dishes focal point ...but believe me I've tried every conceivable postion ...and the one which best suits ..ties with the calculated fd of the dish...
Without the extended dielectric T ...there is absolutely no possiblity of getting AFN on 1 west ..
But with it inserted I get a stable ..watchable picture.
I guess I just got lucky ..both with the construction ..
..and with the chosen material for the dielectric plate.
What is interesting is that an identical cut slab (T shaped) of identical thickness ptfe/Teflon gives about 10% less signal ..
sorry for the life history ..
..but I guess I can't push any more out of my setup
..just wishful thinking.

rgds
VS

 

[Vipersan]

..just as an addon to what I posted above ..
The origional in line polariser was unusual insofaras ..it did not rotate a probe..
In actual fact it had a small motor driving a nylon gear external to the waveguide ..which in turn rotated a circular gear inside the wavegide.
This circular gear was atached to series of linked plates in a line..which ran lengthways down the wavegide.
one end of this series of linked plates being anchored.
The first plate would rotate through 90 degrees dragging the other plates behind ..sequentialy..
The net effect was to form a twist in the wavegide pipe ..and thus rotate the signal through 90 degrees.
Did you ever see one of these before ?
rgds
VS

 

[nelson_b]

I can only assume I was getting maximum possible results for my dish/lnb/plate combo to start with.
cest la vie..
I'm amazed at Nelsons result with the thin brass on perspex ..and can only assume he achieved resonance at that specific fequency..
Looking forward to seeing his results for other sats and other frequencies.
rgds 2 all
VS

hi -
- i do agree you were getting exellent results to start with

i was myself amazed at the increase on the 4175 R - AFN t.p.
but -when i had a play around tonight i found that - it came at a cost - i got a decrease on the ERTU 4180 L t.p .

i,v spent the last hour getting a balance between the two -
which is controled by how far in or out the plate sits in the throat of the l.n.b. --
in for AFN -- out for ERTU --
the balance point is with the top of the plate showing 1 mm outside the mouth of the l.n.b.

this plate with the brass is very sensitive to movement in or out of the l.n.b. much more than the tin -foil one -- other than that they are identical --

i note that the AFN t.p. is Right -- and ETU is Left -- but the frequency number is almost the same ----

any way i have 40 sig strength and 60 quality on both t.p. s
now , which is which is fine -- well above breakup point

had a quick look at 24.5 west to check if i still had 4111 L ORTM
and its still ok - no break up --

and for the first time i had a signal and picture ( no breakup ) from 4193 R - RTB (Burkina Faso) also 24.5 west

so despite the transponder compromise this plate is giving my best results so far --

its been a long day i,m finished playing for tonight --U-zzz

regards - nelson. b.

 

[pride21]

hi nelson_b i tried your lenth of strips starting 10mm next 11.5mm and so on but i found the signal degraded so i got my original plate in lnb,my mesurements are first 7.5mm next 10mm,11.5mm,11.5mm,10mm and last 7.5mm,it seems the best for me with 12mm outside lnbf,i tried to put it inside but it degrades so much.