@ Nelson ...sos

[Vipersan]

Hi buddy ..
I need you to do me a favour ..and check signal levels on AFN 1W

I am suffering low signal levels atm ..and can't get it to lock..
I've been aligning and tweaking so its possible I have sacrificed ...err..something along the way ..
The odd thing is that I can now lock Dunia at 30 East all day ..
And at least one of the starview transponders at 10 East ...at over 10 db for 90 % of the day ..plus both Soni Dharti and Oxygene from Paksat 1R ..so why AFN is unlockable is a mystery ..particularly as ertu and BBC remain locked solid ..?
I am using the esx dual lnb atm ..so that might be it ..but need to know if its low signal before I reverse any changes ..
Cheers m8
VS

 

[nelson_b]

hi vipersan -
only just checked in to sat uk and seen this post
AFN signal is ok here - a good signal -- a fraction lower than ERTU but thats normal for me here
i see the family channel is still f.t.a. --

regards ----

 

[Vipersan]

Thanks for checking Nelson ...its appreciated ..
ertu is about 7db ..about the same as usual ..but AFN is normally about 1.5 db less ..around 5.5 > 6db..
Its currently only 2.5db at my location on the F15 ..
I can only guess its being filtered by the changes I've made ..
Ironic really as all other circular channels appear as good ..or better..
I guess I'll have to compromise ..or give up receiving AFN ??
Not a choice I'm happy with .
rgds
VS

 

[Channel Hopper]

It could be that ERTU is so close to the AFN freq, that your new plate isn't quite able to filter out the opposite polarity.

Possibly positioning, but I recall a number of issues with polar filtering prior to the main focal point of the dish when I was working on dielectric materials back in the 90's.

I'll have a look back through the journals when I get home.

 

[Vipersan]

Now this is interesting ..
I haven't worked out whats different ..or indeed ...what the problem is but..
We are all pretty much aware that AFN exhibits unusual properties at 1W ..
But Flipping the H/V L/R polarity as the setup currently is
..completely kills the signal from ERTU ...BBC Arabic ...plus the data trasponders etc ..
Not so AFN ..
Switching polarity ie V to H or as it actually is L to R does not kill the signal ...it remains constant around 2 db ..
not enough to lock in either polarity ..but _does_ indicate there is something odd about this signal ..
Effectively the plate no longer depolarises 4176V/R ...????
This obviously has something to do with the heightened ..or tweaked positioning of the lnb ...or feed...or plate ..or both ..but only happens on this one transponder.
I can only conclude what we have long suspected ...the polarisation of AFN is different to the run of the mill signals on all other circular polarised signals.

I've no doubt I can get it back ..but would mean destroying the heightened response of the current setup to do it..
Any thoughts on this anomaly are very welcome ..as I'm confused to say the least ..
rgds
VS

 

[nelson_b]

i remember when i was experimenting with D.O.S.plates i never got one that would give me a good signal on both ERU and AFN without a plate adjustment --
as i remember it was ERTU -- plate pushed right into the l.n.b. for maximum signal
and plate halfway out of the l.n.b. for best signal on AFN i always had to compromise on signal strength one way or the other -- i had one plate that would see both signals ok at a reduced strength that sat flush with the l.n.b opening -- and was fine for performance on other sats ----
later when i made and refined my "vipersan" style plate it seemed to iron out all these differences and i got good all round reception across all circular sats including AFN and ERTU - (no more compromise ) ???
these were my findings on my 1.8 offset setup --
i do think there is something different about the AFN t.p -- but i have no explanation - i,m afraid

pic below of my current C band circular l.n.b/plate setup -- which is giving the best all round performance to date -
( usually covered with a plastic bucket to keep the rain out - l.o.l.)

regards ----

Edit --- just checked -- but polarity changing on AFN kills the signal just like the other 2 t.p.s - on my setup ---

 

[Vipersan]

Thanks Nelson
Fairly sure I'm going to have to compromise in the end ..as I suspect thats what I've been doing all along ..
I 'feel' that having tweaked my system to near perfect setup ...I now have instability on just the 1 transponder on 1W ...and I'll have to dumb it down again to get everything ..though I might try twisting the plate a little tomorrow ..to set angle not at 45 degrees to the lnb probe ...just to see what happens ..
rgds
VS
btw Dounia at 30E has been locked solid at 6.5 > 6.7 db for well over 8 hours ...
I guess thats the tradeoff..
Also scanned into the F15 ... reuters and MTVbase from the recently reactivated Amos 5 at 17 East

 

[Vipersan]

It would be a pity to dumb it down ...even the Startimes transponder at 3930V 10 East has been producing a solid locked 9.6 db signal since mid afternoon ..

..and relocated ...winners tvro @62 East ...and only part of the dish can see over the wall..lol

thems the breaks I guess..
VS

 

[Vipersan]

Ok ...
Back to the start ..
having discounted plates ...scalar feeds ...and focal distance of the lnb ..
The only thing left was the new mount plates position relative to the focal point..
I used a laser pen to eastablish this ..
I found out that the laser isnt exactly central in the pen ..and thus errors can and do creep in..
So back to the good old fashioned method ..
A stick placed from the rim of the dish to the support fing ...and a mark on the stick ..
when tried in various positions clockwise around the dish .. a 3/4 inch variance was found north to south ..or top to bottom ...
requiring repositioning of the tripod ..._without_ ..the lnb fitted ..
A combination of the stick method ..and the dish eye has produced a fairly close result ..
See the pic ..(disheye and crosswires)
Proving the dishes single eye ...although useful..isn't the best method to position the feed ..(lacking paralax) .....and laser pens are not accurately constructed..
Now to start over ...but sadly I don't have time today ..
Got to open the shop in an hour..
rgds
VS

 

[pride21]

hi nelson_b the latest plate that i made gets both ertu and afn with plate flush with opening of lnbf,if you or vs would like a plate to try i would be happy to send you one.cheers

 

[Vipersan]

Always in the market to try something new Pride ..
There will always be differences between mine and Nelsons setup ...PF v Offset ..but I would love to compare notes ..
I'll PM you my address
Cheers
VS

 

[nelson_b]

hi nelson_b the latest plate that i made gets both ertu and afn with plate flush with opening of lnbf,if you or vs would like a plate to try i would be happy to send you one.cheers

Yes - pride21-

thanks for the kind offer - i would indeed like to give your plate a try
i will send you my details by p.m.- later

regards nelson.b.

 

[nelson_b]

btw Dounia at 30E has been locked solid at 6.5 > 6.7 db for well over 8 hours ...
I guess thats the tradeoff..

hi -
this channel popped up for me tonight - when i scanned 30 east -- first time i,v had this one
its a very borderline lock though ----
cheers

 

[Vipersan]

Hi friends ..
This is what I mean about laser accuracy ..
This is the tool I made to substitute for the lnb during alignment..
A small battery powered laser insert centred in what was once the top off a can of spray paint ..
Accurately positioned and held in place by 2 x plastic inserts front and back ...
Sadly only acurate to within 1.5 inches over 1.5 metres ..
The reason ..
The laser led is not fitted in the brass encasement centrally ..and so the beam wanders by something like 2 inches over 2 metres ..
Its good enough for using as a rough guide ..and for adjusting the 3 springs holding the lnb plate ..and watching the shift of the laser spot ...
but it lies as to the actual centre point ...as this can be 1.5 inches out at the dish centre.
I've tried many laser pens and inserts ...they ALL exhibit the same inaccuracy ...my guess is positioning of the laser diode within the lense ..or the lense itself encasing the diode is distorted.
For pointing at a blackboard ..this isn't an issue ..
For alignment ...it is..

btw ..you can prove this for yourself if you have a pen or cylindrical laser mounted in a pen ..
switch it on and place it on the floor ..
note the point it makes on the skirting board ...then roll it accross the floor switched on ...and watch the spot it produces ..rise and fall up the skirting board or wall ..
rgds
VS

 

[Vipersan]

Ok ...AFN is back ..
Made the neccessary adjustments to the tripod ..
..managed to reduce the 3/4 inch error to less than 1/4 inch by taking a pipe cutter to one of the legs removing 1/2 inch of copper tube..thus allowing greater scope for movement..
then used the laser insert to get the new plate to within an inch aimed at the dish centre ..
Farrrr to cold to make any tiny tweaks ...so just popped an lnb at the presumed focus ...ignoring the focal distance for now ...
Threw on a commercial scalar plate ..and popped in the old T plate ..not the comb design ..
result is that AFN is back at 6.2 db and stable.
More tweaking to do but it will have to wait for a warmer day ..my hands are devoid of feeling atm ...
I HATE WINTER MONTHS..
No light nights to 'play out' with my girl ....and freezing conditions ..which don't help my 'condition'.
rgds
VS

 

[Vipersan]

Just to add to my above post ..
The accuracy must have improved ..re positioning of the lnb holder /plate ...I'm even getting a startimes transponder at 10 East ...without any tweaking ..and using the same config (unadjusted)
AFN and Startimes on a commercial scalar plate ..
Not had that before..
Maybe all this messing will prove worth it in the end..
;)

 

[Channel Hopper]

Having adjusted the position of the LNB and feed (boresight improvement) you will most likely find tweaking of the polarmount east/west to bring the full arc back to the centre, though you can compensate to some extent by the adjustment of both motors.

Btw, which specific design did you finally settle for last year for your comb filter unit ?

link to thread

http://www.satellites.co.uk/forums/c-band-reception-uk-europe/156485-dielectric-plate-3.html

 

[Vipersan]

Hi CH ..
Yep ..you are correct ...all sat positions have to be tweaked on the Vbox ..both Left to right ...and up and down ..
But I believe the boresight has improved considerably ..
I even have an intermittent lock on Dunia ..and the fine tweaking hasn't been done yet ...and using a commercial scalar feed ..and the basic design T plate ..
Not really come to any conclusion as yet re -- which dielectric plate is best ...as I haven't had chance ..
Both work well ..but the comb (shaped) design was made really for the hombrew scalar feed ....and as such I really need to refit my feed before I can conclusively comment.
All in all repositioning of the boresight ..is certainly an improvement ...
These errors should be expected I guess ..as everything but the actual dish petals is homebrew ...the tripod ..adjustable mount plate ....and the retrofitted scalar feed and plate ...
So many variables ...but thats what makes it fun ..
..at least ...fun when its warm enough to play out
;)

 

[Vipersan]

Ok ...so I've come to accept oddities and compromises are all part of this project ..
The repositioning of the boresight was essential ..and has proved worthwhile ..
I can now get 2x startimes transponders at noon uk time 10 East (see pics) ..and a variable lock on Dunia 30 East (see pics)....and AFN family 1W ...
So ..all good you might think ..
With a commercial plate and the old style T plate AFN locks immediately ...1 transponder possible Startimes ..and is infrequent /unstable and No pics from Kung fu ...dunia is just below lock theshold..
Add the Vscalar plate ...and the Modified (looks like a comb) T plate ....and you have what I listed at first..BUT AFN ...takes time to lock ...its as though the system has to wait isolate and process the signal cloud build up at the plate ...it can take up to 6 seconds to lock ...but once locked ..is stable at a reduced by .3 db signal
A tradeoff indeed ..but the assembly as is in the picture ...VScaler feed and Comb T plate outperforms for sure ..
My guess the tradeoff for the extra gain is slight instability...
rgds
VS

 

[Vipersan]

...and finally before I leave for work ..
WinnersTVRO 62 East @2.8 - 3db-ish ...
Only using part of the dish as a wall is in the way masking the bottom of Christina ...
..and yes ...I have that delay again ....I have to wait over 7 seconds to accumilate enough signal for a lock ..
..but lock it does ..and once locked ..is stable
rgds
VS