Advice Needed Diseqc 1.1 switch insertion loss

[Dggrr]

I think my question is on the relationship of insertion loss db and SNR db (if any!).

One of my setups is currently a ~30 metre cable run to a Diseqc 1.0 4 port switch which has a USALS Diseqc 1.2 motor on port A and a further ~8 meters run to 3 LNBS on a toroidal Wave Frontier T55 using switch ports B, C and D.

This works well, but the LNB on the T55 for 9E only gives about a 9.5db SNR back at the SF8008 receiver.

I'm thinking that it would be neater to have a single cable from the first Diseqc 1.0 switch to the T55 and then short runs to each T55 LNB using a Diseqc 1.1 switch.

Is the Diseqc 1.1 insertion loss likely to be a problem?

An advantage of the cascaded arrangment would be that I could add a few more LNBs to the T55, probably 19e and 13e (currently 28,2e, 9e and 5e).

 

[ozumo]

Just tried a 19.2°E transponder directly at the LNB vs a 20m cable run with 1.0 and 1.1 DiSEqC switches. Signal strength on 11739V 27500 was 10dBuV lower via the switches but SNR was the same 10.3dB.

 

[jeallen01]

@ozumo's loss numbers look about right (if a little high?), but actual numbers will depend on the switches used. Unfortunately, some switch suppliers don't quote loss figures - so check spec sheets wherever possible.

Loss of Signal Level is less important than loss of SNR/Signal Quality, and so that's where using "quality" switches could well prove important.

FWIW, I don't have much trouble with an antenna relay and a Smart Priority Switch in series with about 25m cable (and all the bits of cable connecting the various components!) to the Dark Motor and then to the LNB on the 1.25m Gibby.

 

[Dggrr]

@ozumo

Thanks, I'll give it a go then.

The T55 is really helping clear out my box of old LNBs!

(For anyone reading the first post, the 3rd T55 LNB is on 5w not 5e. 5e on such a small dish would be really magic.)

 

[Terryl]

I think my question is on the relationship of insertion loss db and SNR db (if any!).

One of my setups is currently a ~30 metre cable run to a Diseqc 1.0 4 port switch which has a USALS Diseqc 1.2 motor on port A and a further ~8 meters run to 3 LNBS on a toroidal Wave Frontier T55 using switch ports B, C and D.

This works well, but the LNB on the T55 for 9E only gives about a 9.5db SNR back at the SF8008 receiver.

I'm thinking that it would be neater to have a single cable from the first Diseqc 1.0 switch to the T55 and then short runs to each T55 LNB using a Diseqc 1.1 switch.

Is the Diseqc 1.1 insertion loss likely to be a problem?

An advantage of the cascaded arrangment would be that I could add a few more LNBs to the T55, probably 19e and 13e (currently 28,2e, 9e and 5e).

On the 30 meter run what type/brand of coax? Good stuff would be quad shielded with a pure copper center, less loss, or even RG11.

 

[Dggrr]

Just WF100.

I had WH167 on a previous incarnation but haven't noticed too much difference with the WF100.

 

[jeallen01]

@Terryl

This is in no way meant as a criticism but I don't think RG11 cable is widely, if at all, available for "domestic" use in the UK.

And I'm open to correction but I think that the normal "premium" cables for "domestic" use in the UK are Webro WF100, WF125 and (occasionally) WF150 (or similar) which are copper shielded and screened, foam filled cables with solid copper cores of 1.0, 1.25 and 1.5 sq mm respectively.

Anything else which is "better" will be both difficult and expensive to obtain (WF100 is expensive enough anyway!), and should really not be necessary to solve Dggrr's problems - which are similar to what many of us have faced, and solved, from time to time in the past without needing to resort to the more exotic types of professional-grades of cables..

 

[jeallen01]

Just WF100.

I had WH167 on a previous incarnation but haven't noticed too much difference with the WF100.

FYI here is the useful coax cable comparison chart that the Satcure site issued some years ago before they went out of business. WH167 isn't listed there but you could use the numbers quoted to make some comparisons

 

[PaulR]

WF100 is generally reckoned to be good for up to 50m without a problem. That's in "normal" conditions. For fringe reception that may be a bit optimistic and if there's a long run that can't be shortened then WF125 should be considered.

 

[a33]

Good stuff would be quad shielded with a pure copper center, less loss,

I would totally agree to the pure copper,
but not to the quad shield.
The quad shield would not do much against insertion or cable losses, and would only be needed with very strong interfering signals, I would think.

I still have cables that have just 1 foil and 1 braith (or what is it called in english...?). No problems so far...

Greetz,
A33

 

[jeallen01]

I still have cables that have just 1 foil and 1 "braith" (or what is it called in english...?). No problems so far...

Greetz,
A33

"Sheath" I think, but might be "screen" as I can't remember which - others will confirm one way or the other!

 

[ozumo]

I still have cables that have just 1 foil and 1 braith (or what is it called in english...?)

Braid

 

[jeallen01]

Braid

Absolutely - my memory really must be getting a lot worse than l thought

 

[Terryl]

I would totally agree to the pure copper,
but not to the quad shield.
The quad shield would not do much against insertion or cable losses, and would only be needed with very strong interfering signals, I would think.

I still have cables that have just 1 foil and 1 braith (or what is it called in english...?). No problems so far...

Greetz,
A33

The quad shielding gives a lower DC voltage loss due to less DC resistance, (not much more then regular coax) but in some cases every little bit helps. It's also a good way to cut down on direct 5G radiation into the coax it's self, also it's a good idea to directly ground the coax with an approved ground block.

It also has less loss at 1 GHz (6.1 dB per 100 foot, vs 8.2 on standard coax) (these values change between manufactures)

And some coax is only rated from 900 MHz to 1 GHz, these are for TV and cable TV use, be sure the coax used for satellite is swept to 2.5 GHz or rated to 3 GHz, or your losses with be much higher.

 

[a33]

It also has less loss at 1 GHz (6.1 dB per 100 foot, vs 8.2 on standard coax)

Ah, OK!

Greetz,
A33

 

[jeallen01]

The quad shielding gives a lower DC voltage loss due to less DC resistance, (not much more then regular coax) but in some cases every little bit helps. It's also a good way to cut down on direct 5G radiation into the coax it's self, also it's a good idea to directly ground the coax with an approved ground block.

It also has less loss at 1 GHz (6.1 dB per 100 foot, vs 8.2 on standard coax) (these values change between manufactures)

And some coax is only rated from 900 MHz to 1 GHz, these are for TV and cable TV use, be sure the coax used for satellite is swept to 2.5 GHz or rated to 3 GHz, or your losses with be much higher.

AFAIK all the WF series cables are rated well beyond 2GHz.
And are we not in danger of getting into the classic ¨over-specification¨ situation ¨just bcause we can¨ in a situation that does not actually warrant it?

 

[PaulR]

It also has less loss at 1 GHz (6.1 dB per 100 foot, vs 8.2 on standard coax) (these values change between manufactures)

Taking a figure of 39.2 inches to the metre, this works out at 19.9 dB/100m. The same as claimed for WF100.

The standard co-ax figure equates to 26.8 dB/100m. Whatever standard means!

 

[jeallen01]

Taking a figure of 39.2 inches to the metre, this works out at 19.9 dB/100m. The same as claimed for WF100.

The standard co-ax figure equates to 26.8 dB/100m. Whatever standard means!

Thus reinforcing the case that WF100 should definitely be good enough for most of the installations that are discussed on this forum.

As for the "standard co-ax", I would suspect that that refers to something like a basic commercial air-spaced "satellite cable" co-ax that most installers would use for most "non-critical" installations.

 

[satesco]

@Terryl

This is in no way meant as a criticism but I don't think RG11 cable is widely, if at all, available for "domestic" use in the UK.

...

From what you say, what do I understand as a continental European that RG11 cable is not found in your stores if I want to buy and use it?

 

[PaulR]

As I see it, the problem with using the term RG11 is that there is wide variation in what that means.

The specification lays down basic details such as impedance, layer construction and cable diameter but leaves completely unsaid what the materials have to be. Thus you can get RG11 with a copper coated steel centre core with aluminium sheaths and braid through to full copper core with copper sheaths and braids with consequent wide differences in impedance losses.