Coax cable, double screen ("triax cable") - advice?

H

Hudson

Member
My Satellite Setup
Panasonic TU-DBS30 Sky Digibox, 90 inch prime focus SAMI mesh dish (formerly C-band antenna), f/D=0.38
My Location
Denmark
Hello all

Nice people have given me a scrapped drum of 75 Ohms camera cable from a television station. It is coax with two sheaths, known as _http://en.wikipedia.org/wiki/Triaxial_cable Triax cable 8 . Apparently this cable has greater attenuation than RG11 or even RG6 (slightly) according to _http://communications.draka.com/sites/eu/Datasheets/st31e.pdf" the specs but I was hoping that the extra shielding might lead to better signal quality even if it is attenuated more.

What is the advice of the collective wisdom here? And yes, it has something to do with price. I have to run abt. 90 meters of cable in order to hide the dish as much as possible and I want to receive Sky and others from Astra 2D.

If I use the cable, how should I connect it to take advantage of the extra shielding provided by having two sheaths? I have four C-connector jacks for cable ends and the suitable plugs for them as well but the LNB I plan to buy (Invacom QDF-031) of course only has F-connectors.

Thank you in advance.

Hudson
 
Not designed for satellite, only suitable composite video distribution.
 
Do it with fibre, you could then have as many outputs as you would need at the house. You could use the stuff you mentioned to send the power down to the fibre LNB.
 
For that long of a run try to find some LDF-400-75, I have used this out to 400 meters, it is very pricy though.
 
hello,
this cable is not good for satellite, the loss will be too much.
video cable is used to send a video signal, this signal is from 0 to 6 mhz in that area and with 100 meters in length it may by a 6 db loss.
run a satellite signal from 950 mhz to 2,150 mhz and there mat be a 30 to 40 bd loss.
if you are running a length of 90 meters from the dish to the receiver i would try good low loss cable first and then probably a 10 to 15 db inline amp.
place the amp close to the dish.
or use fiber optic lnb and a fiber optic line but this may be expensive to do so.
ralph
 
@Robbo abt fibre: Interesting. Do you have a link to a more elaborate description of this method?
 
hello
i was not sure if you are asking me another question.
if you do not have sky plus and just a regular sky box then you need one line.
run a good low loss cable first and try that.
if you are having problems with the weeker channels then a small inline amp about 15 db will improve the weeker signals
ralph
 
Before considering a fibre solution, which would be quite expensive for domestic use, we need to know details of the dish (is it the one in your profile) and your location, if in the UK, not a problem, but if in a fringe area, Fibre MDUs (LNBs) are not as sensitive as the best standard LNBs and you may have problems with the Astra 2D channels.


Here are the prices of the kit from one of our supporting advertisers: _http://www.sateuropa.co.uk/overview.asp?catid=12&subcat=66
 
I still say this is the best bet for that run.

hXXp://www.frontier518.com/cables/lmr400-75.htm
 
It would be fine if it was sold in the UK, which I don't believe it is. You can of course buy equivalent RG11 cables in Europe and the UK, one of these is WF165 from Webro, they also have quick mount connectors for it, which require no specialist compression or crimp tools.

If the original poster is looking for two feeds to the house, then the fibre option becomes more realistic, as the RG11 1.65 option is ramping up the cost, although the job would still be doable with a smaller core cable and a couple of line amps which would be significantly cheaper.

Triax TX125 for example with a couple of line amps would set one back just over £200.
 
Yes, I was mainly thinking about if the OP would want further feeds at a later date, which generally people do.

The fibre solution is the most versatile, as very little extra work would be required to add any extras required, but not cost effective for just one feed or maybe two.

The fibre solution consists of a fibre optic LNB, a length of fibre, and a fibre to coax converter module (eg Virtual quad). The LNB needs power and can be supplied by standard coax.
 
Thank you for the replies.
Yes, the dish is the one in my profile info.
No, I am not in the UK, I am in Denmark just outside the 2D footprint for 120 cm dishes.
I really need the 2D signal as the missus is very keen on watching English television.
Two or more feeds would be a very good bonus.

I have looked at some of the info on the Invacom fibre lnb and it is very handy that it comes in a C120 version usable with the adjustable feedhorn. My dish has an f/d of .38 and I do not expect the standard LNBs to fit. If I go analogue I am inclined to buy the same feedhorn with the QDF-031 quad lnb.

Best

Hudson
 
What dish is it for? Prime focus or offset? If it is for offset use a Black Ultra. The gross signal from that LNB is a good 10dB more than the Invacom. Worst case over 90 metres with good quality, standard 1mm core cable is around 28dB loss at 2GHz and 20dB at 1GHz. I think that would probably be ok even without a line amp, although one would help. All depends on your budget really.
 
Hudson said:
the adjustable feedhorn.
Click to expand...
I'd steer clear of those; they eat the signal.
 
Huevos said:
What dish is it for? Prime focus or offset? If it is for offset use a Black Ultra. The gross signal from that LNB is a good 10dB more than the Invacom. Worst case over 90 metres with good quality, standard 1mm core cable is around 28dB loss at 2GHz and 20dB at 1GHz. I think that would probably be ok even without a line amp, although one would help. All depends on your budget really.
Click to expand...

The dish is prime focus with an f/d of .38 which - as I understand things - rules out the Black Ultra. I actually have one of those on my 120cm dish modified with the original feedhorn from the previous lnb to f/d .50. And right now - 11.40 EU summertime - there is not enough signal to pick up any of the channels I chose at random to test :-(

My new dish has a area 3,6 times larger than the old one, but since it is petalized and made from mesh (as opposed to the solid old one) I expect lower efficiency. But even a reduction of, say, 45% would still mean a doubling of signal strength. If cable attenuation eats up the increase I would be very sorry.
 
I think it would be wise to do some tests with the mesh antenna before worrying about the feeds, to see if its any good for ku band and specifically what you want to watch on 2D.
 
If you can fit a wood pencil through the grids holes its an iffy for Ku band, the grid pattern may be too large.
 
Terryl said:
If you can fit a wood pencil through the grids holes its an iffy for Ku band, the grid pattern may be too large.
Click to expand...

Thanks. I was aware of that and luckily the mesh is much smaller than that.
 
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