SG2100 Insertion loss

[satcom1]

Noticed that there was about a 3% reduction in Signal Quality with the motor inline.

Cut the foil coil at the LNBF connector and inserted a 1 Uh choke @ .65 Amps.

Signal Quality increased by 3%.

 

[Smith P.]

I did bypass the motor using second cable. In my case the loss figure ( amplitude on spectrum analyzer ) was more 10 dB .

 

[jerryt]

Noticed that there was about a 3% reduction in Signal Quality with the motor inline.

Cut the foil coil at the LNBF connector and inserted a 1 Uh choke @ .65 Amps.

Signal Quality increased by 3%.

You should do the external power supply modification for the SG2100, if you have the motor that far disassembled.

 

[satcom1]

Smith, P

I did this mod. for PBS HDTV, 2 channels. They typically were in the mud at 29% to 31%. I am now reading a solid 41%. I think it will help with Equity / RTN if I can ever get a motor to work.

What make of motor did you bypass. I just wonder if they all have insertion loss higher then it should be.

Best Regards,

Tom

 

[satcom1]

jerryt,

Yep, I gave up on this motor ever working the way the factory made it so I decided to "have at It"when I opened it up it was like a birds nest. Dirt, vegatation, sticky stuff that I don't even want to guess at what it is. Seven cold soldier connections. An IC that was popped out of its inline socket at one end and Metal shards attached to the Heil sensor magnetic wheel.

 

[Smith P.]

It was SG-2100.

 

[qwert1515]

Smith, P how did you bypass the motor? Did you make an internal modification or an external one?

 

[SatelliteAV]

I choose to use a 2x1, 2GHz, 2port power passing splitter. The loss of the splitter is much less than the DiSEqC motors. Most HH motors introduce at least a 7 - 10dB degradation.

Had a discussion last week with a customer who experienced a 48% Signal Quality for GMTN on AMC4 through a motor and 72% SQ with direct connection. He used a 2x1 splitter, 2Ghz, 2PPP and was happy with a 67% SQ.

Motors are good for moving, but not kind to signals!

 

[Anole]

Building some proper splitters sounds like a good project for those not hardware-challenged.

Maybe use an old 2:1 TV splitter; they should be easy to open and mod...
. . . or gut some of the cheap diseqc switches I got for Black Friday!
Now, the big challenge is to figure out what to do with the two unused connections. -

[FONT=Fixedsys]..
.             +------------ LNB
.             |  
.rcvr --------+
.             | 
.             +---@@@@@---- motor
.                (choke)
.[/FONT]

Would be interesting to see how this performs compared to the: 2x1, 2GHz, 2port power passing splitter.

I'm certainly not against opening the motor (again), but this would be something the less adventuresome would prefer.
So, I agree with SatAV that external is the way to go.

 

[qwert1515]

Anole, What is the purpose of the coil/choke ?

The only thing I can think of is to add resistance so that the LNB signal would "rather" travel to the receiver than to the motor.

 

[Anole]

just a different way to skin the cat . . .

The coil serves the same purpose as the choke in Satcom's post above.
It just keeps the RF/IF (L-band) out of the motor totally.
However , it doesn't block the low 22khz signal from going to the motor.
Functionally, it's no different from what he proposed.
Just external, 'cause I liked what SatAV suggested.
It's for those who'd prefer to not open their motor and risk any warranty.
Best of both, you could say.

But as for the best inductor value, I'll have to think about that . . .

 

[qwert1515]

Thanks Anole,

So it kind of acts like a low pass filter, time to experiment (Hopefully my BLSA will help me wind a coil)

 

[qwert1515]

It's 2:07 AM I played around with my BLSA and a few coil windings and I can block the whole L-Band until I put the coils into the metal case

The first spectrum scan is an uncalibrated scan of a Ku band satellite,
The second scan is with two coils before being placed into the metal case,
The third scan is in the metal case

I guess I have to try again tomorrow.

 

[Smith P.]

Smith, P how did you bypass the motor? Did you make an internal modification or an external one?

Use two coax cables: one connected straight to LNBF (linear); second - to a motor, then to LNBF (circular).

 

[brentb636]

I choose to use a 2x1, 2GHz, 2port power passing splitter. The loss of the splitter is much less than the DiSEqC motors. Most HH motors introduce at least a 7 - 10dB degradation.

Had a discussion last week with a customer who experienced a 48% Signal Quality for GMTN on AMC4 through a motor and 72% SQ with direct connection. He used a 2x1 splitter, 2Ghz, 2PPP and was happy with a 67% SQ.

Motors are good for moving, but not kind to signals!

This is an interesting thread, and may solve a problem I'm seeing. I'm getting odd quality feedback on my 80cm dish with SG2100 motor. I ordered two of the splitters from SatAV today, and will put one in and find out if the motor is interfering with the signal quality. At the very least, it will be an interesting troubleshooting technique.

 

[satcom1]

Brent,

While your waiting for your order, setup your dish on a weak but vieable signal, goto the dishmotor and disconnect the cables and insert a F series female coupler. Now read your signal quality.

Tom

 

[Smith P.]

There is no question about signal degradation thru HH motor; real question - what exactly the loss figure.

 

[brentb636]

Brent,

While your waiting for your order, setup your dish on a weak but vieable signal, goto the dishmotor and disconnect the cables and insert a F series female coupler. Now read your signal quality.

Tom

I've done that , Tom, and since I'm using an Invacom, I have switched to the other linear output, but so far the results are inconclusive. On the same day that I peaked my 80cm dish on 11720 V of G18 ( q=52 best I saw) an hour later the q is 28-32 and pixelating. Might be weather at Little Rock, might be weather here in Holland, but I'm also having some problems with the SG2100 at the same time.
Reset my Merc II to defaults, and started over with no unexplained problems since. Still it will be nice to get the splitter in the line to seperate the lnbf from the motor control and see how I feel about that! Thanks for the feedback.

 

[satcom1]

At Motorola we use a loss figure of .25 db for every N type connector inline at 450 Mhz. So at 1.5Ghz and F connectors it's probably a lot more. 1 db being about 20%

 

[brentb636]

At Motorola we use a loss figure of .25 db for every N type connector inline at 450 Mhz. So at 1.5Ghz and F connectors it's probably a lot more. 1 db being about 20%

Interesting, Do you work in Schaumburg ? I've been there for several 800mhz trunking classes.