Lnb

[C_S_B]

Re: Lnb

hi I changed my LNB and find that certain frequencies on some satellites variate a lot from full signal to none at all and signal continually fluctuates and yet if I put original lnb back on dish this doesn't happen
Can anyone help or has anyone any ideas?

Why did you change your lnb, if the original one works ?

I'm sure that would be a little more helpfull.

[kalpikos]

Re: Lnb

Dear,
may be your lnb is faulty so you have to return it back and take other and better other model, or you just forgot to adjust the skew.
Turn it left or right for a little in order to find better signal.

[nanor01]

Re: Lnb

ok I will try that ..

did as you suggested and still the same..

I had originally a single lnb and swopped it for a quad

[kostis]

Re: Lnb

ok I will try that ..

did as you suggested and still the same..

I had originally a single lnb and swopped it for a quad

i done the same, those quad are less powerful than my 12 years old single lnd! the signal is 5% less and they also break a lot (every 2 years), anyway when i put a new lnb its not in the same position as the old one it need a lot adjustment, give it a try before you run to the store.

[nanor01]

Re: Lnb

thank you... would the fact that satellite cable is approx. 20 or 30 meters away from stb and joined in 2 places make a difference with certain frequencies not being received?

[Mobley3]

Re: Lnb

thank you... would the fact that satellite cable is approx. 20 or 30 meters away from stb and joined in 2 places make a difference with certain frequencies not being received?

You should not have any joins in Sat Cable, do yourself a favour and go out and buy some decent CT 100 cable or similar, and then check the results.

Regards Mobley3

[purenirvana]

Re: Lnb

Well as your original LNB worked on all frequencies with the length of cable and the joins in it I can't see this being your problem.

That said, if it was my satellite equipment, I would definitely be making plans to re-cable as I wouldn't want two joins in my cabling.

[C_S_B]

Re: Lnb

Less connections the better. But more important is understanding that the signal from the lnb to receiver is not carried via the central core or outer shield.

But the space between the two. A bit like a ****/garden hose.

So, smooth bends will deliver a better signal to your receiver. If junctions are done properly you will get a good signal, however they increase the chance of water ingress.

Also make sure your F-Connectors are terminated properly.I'll bet most signal issues happen there.


Edit: Don't buy cheap cable. IE Sky shotgun type that is everywhere. Do as advised in this thread, buy once, install correctly and it will last 10's of years. You will change your dish more times than the cable if done right. Also think ahead. If you have a dish that's in a really hard place to get to. Put in extra cables at the time of wiring (& leave some spare coiled-up near the dish).

You should not have any joins in Sat Cable, do yourself a favour and go out and buy some decent CT 100 cable or similar, and then check the results.

Regards Mobley3

[aplok]

Re: Lnb

... the signal from the lnb to receiver is not carried via the central core or outer shield.

But the space between the two. A bit like a ****/garden hose.

hi,

do you mean the coax tv-sat cables's physic behaves like wave guide ?

if so, one should consider to be especially tidy for junction,
for copper contact,
and
to reduce plastic-air-plastic impedance's echoes :

?

[C_S_B]

Re: Lnb

hi,

do you mean the coax tv-sat cables's physic behaves like wave guide ?

if so, one should consider to be especially tidy for junction,
for copper contact,
and
to reduce plastic-air-plastic impedance's echoes :

?

Correct.

Although slightly off topic, fibre optic's work in a similar fashion. In Multimode fibre optic cables, that are used in offices and locally, the light/signal that is sent down the cable, is actually bouncing off of the inside surface of the fibre.

Reflecting like a mirror on the inside of a ****.

And this is similar to the principal that applies to RF signals.

[aplok]

Re: Lnb

ok, great,

so that's something to keep in mind when cabling with tv's coax:

Reflecting like a mirror on the inside of a ****.

,ie

case 1: theoretical and perfect 90° bending :

incident:


| v |
| v |
| v |
| v |
| v |
| v |
| v |
| v +------
| v
+-x--------


reflection:


| ^ |
| ^ |
| ^ |
| ^ |
| ^ |
| ^ |
| ^ |
| ^ +------
| ^
+-x--------


transmission : 0 % <- full reflection, come back

case 2:real life bending :

incident - bounce - reflection -> transmission


| v |
| v |
| v |
| v |
\ v \
.\ v \
..\x \
...\.> +-------------
....\..>
.....\...> > > > > > > ~100 %
......\
.......+---------------

last but not least, the 2Ghz wave length is ~ 15 cm !

( and the 10 000 Ghz is ~ 3 cm )
( and the 12 000 Ghz is ~ 2.4 cm )

[nanor01]

Re: Lnb

so if I completely replace the cable this should fix the problem altogether?

[Mobley3]

Re: Lnb

so if I completely replace the cable this should fix the problem altogether?

,

Not necessarily, as I mentioned in my earlier post you will need to tune the Lnb in the mount for best signal, also if you are missing frequencies then check that the settings for the Lnb are correct in your receiver, generally 10.600 -12.700 for Universal Lnb's, unfortunately you have not given us any info relating to the new one other than that it is a Quad.

Regards Mobley3

[nanor01]

Re: Lnb

sorry its a universal sky lnb

[Mobley3]

Re: Lnb

sorry its a universal sky lnb

Some confusion here ,on your original post you said that signal varies on some satellites. Are you using just a fixed Sly dish or is your system motorized ?
If you are using any other dish than a Sly one then this Lnb will not work properly as it only works with a dish that is wider. Please confirm which.

Regards Mobley3