A couple more db. - Page 2 - Techwatch: Satellite TV forums, FTA, Cable, Hardware, & Tech forums

Jimdefruit · 12-06-07, 08:36 AM

I am with Stick on this one - I dont know what I am talking about,

Surely, if you do manage to get the two signals in phase it will only be at a specific frequency. Also you might double the signal strength and get a 3 db increase. Worth it?

Go for it and let us know what actually happens.

$ly · 12-06-07, 09:21 AM

That's the plan Jim.
It will be better at A specific frequency (assuming I cut it correctly), but will not be as much as a fiddle as it would first appear in that I will be dealing with the IF frequencies which are about 100mm per ½ λ at 1400MHz and not (the less than 3cms at) 10GHz which the LNB sees at the other side.

L.

BGonaSTICK · 12-06-07, 10:28 AM

I don't see why it would be limited to a single frequency, or be (or even need to be) optimised to one - the whole microwave frequency block is dropped down to an IF block at the LNB.

As far as I'm concerned, you shouldn't need to tune the length of the coax to a particular wavelength - you're only trying to match the two lengths exactly to ensure the carriers are synchronised. You might even find that the two will be out of phase as soon as the signal leaves the F connectors on the LNB - depending on how the LO works between the two halves.

It might, for example, be 180 degrees out right off the bat.

Or am I talking crap again?!? :roflmao:

Does a twin LNB have one or two local oscillators?

Who's volunteering to smash one up and find out?!?!? :spite:

$ly · 12-06-07, 10:47 AM

Two I hope.

Yes, just went down ro get some tools and thought about that. The Length is immaterial providing it contains the same amount of wavelengths (down to less than one sixteenth or better) so they add. 180 degrees would theoretically lose everything although in practice this won't be the case.

Well the Broadlogic runs it like this although the signal strength displayed is a bit pants like the SS2 it gives the same sig and q readings all the time.

Going to put the SS1 in and see what we can get.

Wish me luck chaps.

L.

BGonaSTICK · 12-06-07, 10:54 AM

LOL - good luck.

If it was 180 degrees out, you'd just have to trim half of one wavelength (wavelength of what exactly, I don't know!) off the coax.

Ow, now my head hurts, and I've not even had my first beer of the day yet :roflmao:

$ly · 12-06-07, 11:18 AM

1450Mhz (about mid band) is 200mm per wavelength.

Right something is happening, BBC World on 1W is normally ~86%.
Plugged both in and went down to 37%.
Cut 40mm off the length of one and plugged both back in sig changed to 73%

So the theory looks sound.

Just got to find the critical point now. :

L.

BGonaSTICK · 12-06-07, 12:39 PM

The critical point will come after 12 hours when your patience is exhausted and you swing a 2lb club hammer at the LNB in frustration!

Sounds promising - it does seem to prove the theory doesn't it?

12-06-07, 08:36 AM	#11 (permalink)
Jimdefruit Super Moderator Join Date: Jan 2006 Posts: 2,642 Thanks: 10 Thanked 88 Times in 83 Posts	Re: A couple more db. I am with Stick on this one - I dont know what I am talking about, Surely, if you do manage to get the two signals in phase it will only be at a specific frequency. Also you might double the signal strength and get a 3 db increase. Worth it? Go for it and let us know what actually happens. __________________ Dreambox 7000s + VBox + Channel Master 1.2 with 36v actuator CM120 feedhorn and Invacom .3 LNB Skystar 2 PCI card with links to my Dreambox If you like what you see here, tell your friends.

12-06-07, 09:21 AM	#12 (permalink)
$ly Super Moderator Join Date: Feb 2006 Location: Out There Posts: 496 Thanks: 1 Thanked 2 Times in 2 Posts	Re: A couple more db. That's the plan Jim. It will be better at A specific frequency (assuming I cut it correctly), but will not be as much as a fiddle as it would first appear in that I will be dealing with the IF frequencies which are about 100mm per ½ λ at 1400MHz and not (the less than 3cms at) 10GHz which the LNB sees at the other side. L.

12-06-07, 10:28 AM	#13 (permalink)
BGonaSTICK Super Murderator Join Date: Nov 2005 Location: Brighton Posts: 10,626 Thanks: 3 Thanked 53 Times in 34 Posts	Re: A couple more db. I don't see why it would be limited to a single frequency, or be (or even need to be) optimised to one - the whole microwave frequency block is dropped down to an IF block at the LNB. As far as I'm concerned, you shouldn't need to tune the length of the coax to a particular wavelength - you're only trying to match the two lengths exactly to ensure the carriers are synchronised. You might even find that the two will be out of phase as soon as the signal leaves the F connectors on the LNB - depending on how the LO works between the two halves. It might, for example, be 180 degrees out right off the bat. Or am I talking crap again?!? :roflmao: Does a twin LNB have one or two local oscillators? Who's volunteering to smash one up and find out?!?!? :spite: __________________ Dreambox 7000, Skystar2 PCI, Skystar USB, Fibo 90cm on Moteck SG2100, Triax TD110 multi-LNB. Sky + ART cards. 45.0°E - 58.0°W

12-06-07, 10:47 AM	#14 (permalink)
$ly Super Moderator Join Date: Feb 2006 Location: Out There Posts: 496 Thanks: 1 Thanked 2 Times in 2 Posts	Re: A couple more db. Two I hope. Yes, just went down ro get some tools and thought about that. The Length is immaterial providing it contains the same amount of wavelengths (down to less than one sixteenth or better) so they add. 180 degrees would theoretically lose everything although in practice this won't be the case. Well the Broadlogic runs it like this although the signal strength displayed is a bit pants like the SS2 it gives the same sig and q readings all the time. Going to put the SS1 in and see what we can get. Wish me luck chaps. L.

12-06-07, 10:54 AM	#15 (permalink)
BGonaSTICK Super Murderator Join Date: Nov 2005 Location: Brighton Posts: 10,626 Thanks: 3 Thanked 53 Times in 34 Posts	Re: A couple more db. LOL - good luck. If it was 180 degrees out, you'd just have to trim half of one wavelength (wavelength of what exactly, I don't know!) off the coax. Ow, now my head hurts, and I've not even had my first beer of the day yet :roflmao: __________________ Dreambox 7000, Skystar2 PCI, Skystar USB, Fibo 90cm on Moteck SG2100, Triax TD110 multi-LNB. Sky + ART cards. 45.0°E - 58.0°W


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12-06-07, 11:18 AM	#16 (permalink)
$ly Super Moderator Join Date: Feb 2006 Location: Out There Posts: 496 Thanks: 1 Thanked 2 Times in 2 Posts	Re: A couple more db. 1450Mhz (about mid band) is 200mm per wavelength. Right something is happening, BBC World on 1W is normally ~86%. Plugged both in and went down to 37%. Cut 40mm off the length of one and plugged both back in sig changed to 73% So the theory looks sound. Just got to find the critical point now. : L.

12-06-07, 12:39 PM	#17 (permalink)
BGonaSTICK Super Murderator Join Date: Nov 2005 Location: Brighton Posts: 10,626 Thanks: 3 Thanked 53 Times in 34 Posts	Re: A couple more db. The critical point will come after 12 hours when your patience is exhausted and you swing a 2lb club hammer at the LNB in frustration! Sounds promising - it does seem to prove the theory doesn't it? __________________ Dreambox 7000, Skystar2 PCI, Skystar USB, Fibo 90cm on Moteck SG2100, Triax TD110 multi-LNB. Sky + ART cards. 45.0°E - 58.0°W