lnb modification

[jimbofz]

Hi everybody,im quite new to this forum ,i have afew questions for the teckies ,i used to install systems back in the analogue days ,i spend 10 weeks each year in costa blanca ,over there the only way to receive freesat or any uk tv, is with a1.9 mtr dish or a 60cm dish just for south beam [very limited choice] .
not every one there has the space to fit a large dish ,so a lot of companies have set up rebroadcast systems [they buy a licence to rebroadcast in spain] i have swung a small dish towards their mast and recieved signals but they must either be using circular polarised lnbs or are using lower local osc frequency lnb.i know these sigs are unencrypted as i borrowed my neighbours lnb, and with a full scan of my fta receiver bingo !
question; any ideas what mod they may have done to the lnb?
maybee inserted dielectic plate inside feedhorn?
i tried all the sat shops but they couldnt help the lnb looks just like a normal uni but with no markings on it any thaughts please

[nanochickin]

It might sound stupid but if you think they are circular polarity lnbs you could always try an old BSB squarial

The other place to find them would be on Ebay .com (The yank site) as they still use circular polarity in the USA

[jimbofz]

yes i looked on American sites at all the circular types ,hoping i would see one that looks the same [with the same casing ] but no joy it looks for all the world lihe a common uni single o/p type inside there were no numbers only a serial number 0809783a02766,there were no trimmers inside for l/o freq ill have a look for a squarial type thanks

[Topper]

Don't know why are you bothering when the systems are regularly being taken down by the Spanish authorities?

[jimbofz]

yes a lot of the dodgy non tax paying rebroadcasters have been locked up by the guarda civil they dont mess around,
but the ones that are registered in Spain are still allowed to transmit
its a bit of a lottery, many ex pats have been ripped off.the best ones provide tv for norweigans,as well as the brits , who otherwise would need JODERAL bank on their roof 1

[ralphmagno]

hello the lnb can be adjusted no problem.
but what frequency will you be reciving?
the osc can be adjusted by about 90 mhz.
if they were transmitting on a frequency of 10660 ghz your receiver will not tune below 10.750 so moving the lo to 09.660 ghz and bingo the receiver will receive a frequency transmitted below the satellite band by 90 mhz.
the receiver will say 10.750 even though you are receiving a signal at 10.660.
they are probaly using hor or vert polerazion.
this is like a mmds system and without the ofset on the lo no one will pick this up.
a 1 watt transmitter will at 10.6 ghz will go 20 km line of site with a 30 cm dish and 30 km witha 60 cm dish.
if you know the frequency it would be easier.
i have modified 100 lnbs like this.
the f-wave is the easiest

ralph

[slugworth]

The dielectric plate is just non-microwave safe plastic,the kind that heats up and melts in a microwave oven.
In the colonies people use old credit cards cut to fit the lnb throat.
I have used milk bottle plastic and plastic lids from coffee cans,but you have to double up the plastic strips if too thin.
Stick in the lnb throat at the 1 o'clock position relative to the probe inside.

[jimbofz]

hi i believe they transmit on 9.54ghz this is received on a 30 cm dish pointed towards the horizon, the lnb that is supplied when opened,has no trimmers to adjust l/o freq ,i tried a standard uni and tweeked the trimmers slowly with sig strength meter,
i still could not receive the sigs ,this led me to think they must modify feed horn any thaughts ?

[Huevos]

I can't believe that is anything but a universal LNB.

[jimbofz]

hi very informative reply thanks ralph magno is the F WAVE a type of lnb ?if so who makes them? another interesting point the system requires no skew of the lnb but when i rotated it beyond 90 degrees the sig went up?
most uni lnbs i/p freq is 10.7ghz to 11.7ghz this means that if i tweek the trimmer i still cant reduce the freq low enough any thoughts please

[Huevos]

Just a thought. If the transmitter were really broadcasting on 9.54GHz and you set the receiver to l.o. 10.6GHz (i.e. hi band) the IF would be on 1.06GHz, well within the receivable range of the box with a standard universal LNB. This is not the case though as all the ones I've seen are tuned to lo-band, somewhere around 10.7GHz if I remember right.

How about doing a test the other way around? Stick the possibly modified LNB on a dish pointed at a satellite and see how it works. This would prove whether it is modified or otherwise.

[jimbofz]

hi thanks for reply ,i tried that i have a dish set for 28.2 astra
it receives south beam with standard uni lnb ,
when i tried the modified lnb i got no signals ?

[jimbofz]

hi being new to the forum im not yet allowed to post pm[ private messages]
i want to contact Ralph magno as he seems to have the answer to my problem.if you read this Ralph can you e mail or pm me please ,i would like some more info re lnb l/o mods MANY THANKS JIM

[Channel Hopper]

Just a thought. If the transmitter were really broadcasting on 9.54GHz and you set the receiver to l.o. 10.6GHz (i.e. hi band) the IF would be on 1.06GHz, well within the receivable range of the box with a standard universal LNB. This is not the case though as all the ones I've seen are tuned to lo-band, somewhere around 10.7GHz if I remember right.

Unless I have read your post incorrectly, a digital stb with a functioning Local oscillator setup will not work to receive a lower working frequency than the local oscillator it is set up to use, unless are working at C-Band.

Since these are normally set to 5.150GHz, you could always programme this into the receiver, and then scan with a standard unversal LNB (set to the upper band with the 22kHz switch) around the frequency of 4.09 GHz.

[Tsiklon]

Perhaps the OP could post a photo of the LNB used by his neighbour?

He could also figure out what the LO of the modified LNB is by doing a blindscan on 19e with the modified LNB and calculating the difference between the recorded freq and the published freq on lyngsat.

I've only ever heard of terrestrial transmission of television channels in the Ku band, but never below 10.7 GHz in the 9GHz region.

[jimbofz]

Thanks Channel hopper i never thought about c band ,its just that my neighbour who has this system
i borrowed his lnb just to try and after a full scan on my fta receiver bingo all signals received.
i did not have to alter my fta settings to c band , all sigs received i then began the QUEST of finding out what was different with this lnb .
A standard lnb will pick up some sigs but not them all SO ;
its either lower l/o freq ? possibly around 9ghz
dielectic plate inside feedhorn?
or something else ,possibly sourced from USA for circular polarisation?
any thaughts

[Channel Hopper]

Thanks Channel hopper i never thought about c band ,its just that my neighbour who has this system
i borrowed his lnb just to try and after a full scan on my fta receiver bingo all signals received.
i did not have to alter my fta settings to c band , all sigs received i then began the QUEST of finding out what was different with this lnb .
A standard lnb will pick up some sigs but not them all SO ;
its either lower l/o freq ? possibly around 9ghz
dielectic plate inside feedhorn?
or something else ,possibly sourced from USA for circular polarisation?
any thaughts

A circular polarised chanel will be approximately 4dB down if using a non circular LNB and so I would not expect this to be the reason for no detection.

Unless your neighbour has a hugely modified LNB (with something like an 8GHz local oscillator), I can only suggest you try the C-Band trick and let us know what happens, however, if this was the case, then there would be no need to offer modified LNB's in the first place. Are you certain 9.54 GHz is correct ?

[Channel Hopper]

Ahhhhhh.

http://www.satellites.co.uk/satellit...gnals-etc.html

[jimbofz]

thanks again channel hopper this thread seems to be quite old and things have moved on ,the old systems rebroadcast analogue with a wire mesh square aerial and downconvertor the new guys use 30 cm dishes and the MYSTERY LNB

[jimbofz]

i was told by a local sat installer that they used this freq he seemed pretty certain cheers ps love the logo septic resident

[Channel Hopper]

There are five pages, last post was a year ago, and there is mention of microwave frequencies of 15GHz, which can be received using a modified telecom band LNB.

[jimbofz]

15ghz cant find the original post for this?

[ralphmagno]

hello to all we need to do the math.
first the satellite receiver, the tuner will not usualy go below 950 mhz.
the tuner is rated at 950 mhz to 2150 mhz.
tuners that tune below 950 mhz may exist but i have not realy found one.
the lo of a standard lnb is 2 osc. one at 9.750 ghz and upper band at 10.6 ghz.
since we are trying to receive a retransmitted frequence in spain and we assume its a digital transmission using mpeg 2 at 9.54 ghz then in thery the lo lower band would have to run at 8.580 ghz to give a output at 960 mhz and the tuner would lock on to this ok.

but being that they are transmitting at 9.54 ghz a standard lnb can be lowered from 9.750 ghz to 9.650 ghz no problem.
but lowering the lo to 8.580 ghz is a 1,160 mhz lower and it will not work.
the lnb is probaly made special for this project.
in my area the 10.660 ghz tranmission a 30 cm dish and a modified lnb
works like a champ.
i have tunes the 9.75ghz 90 mhz down to 9.660 ghz to receive a 10.660 ghz signal then the tuner thinks its receiving a 10.750 ghz satellite signal
and it works like a champ.


well hope this helps
ralph

[jimbofz]

Hi Ralph if i got an old 10.00ghz blue cap [metal casing, used in uk when analogue was the only option]
and reduced the l/o to 9.00ghz do you think that would work ?

[Channel Hopper]

Hi Ralph if i got an old 10.00ghz blue cap [metal casing, used in uk when analogue was the only option]
and reduced the l/o to 9.00ghz do you think that would work ?

Highly unlikely you could get the trap to function much beyond a couple of 100MHz outside its standard setting, certainly not 12%.