slaving 2nd receiver with switch in system

[B.J.]

I've probably mentioned this before a couple times, but it hit me again today, and I thought it wouldn't hurt to post as a reminder. I run several of my receivers in slaved mode, where the dish, LNB(f)s, and diseqC switches are controlled by other receivers. I have often noticed that reception on the slaved receivers gets very poor, if the controlling receiver is not locked on a transponder.
This SEEMS to only happen on the slaved systems that go through a diseqC switch. Ie what seems to happen, is if the controlling receiver is not locked on a signal, that the firmware of many receivers attempt to re-tune the transponder by sending out DiseqC signals to the switch (I've used this in the past to help tune in satellites with a meter that has a 22KHz indicator, since when the transponder is locked, it won't send out the 22khz diseqC signals, but when you lose lock, it sends them out, so I'd split the difference between the two points where the 22khz indicator lights).
Anyway, for some reason the sending of these diseqC signals seems really degrade the sat signal, and I'm not at all sure why. I know that in some cases, it's because it has actually tried switching my switch to another switch position, but it also degrades it seriously even when it's sending the proper switch position. Also, if I turn off the diseqC option, then the signal is NOT degraded on the slaved receiver.
So, I'm curious relative to whether anyone has any theory for WHY the signal would be degraded while a diseqC signal is being sent? You wouldn't think it would be the 22khz that's doing it, since when working through a 22khz switch, the 22khz is on continuously, and doesn't affect things too much. The degradation seems to occur whether I'm slaving through a passthru or if I'm slaving via a splitter, so it doesn't seem to be caused by the passthru shutting down. Perhaps when the diseqC is generated, it changes the impedance of the controlling receiver or something???

Anyway, does anyone have any theories???

 

[zamar23]

If this observation is common, may be a DC Block in the Master's Loop Out port causes signal degradation when activated. However, I don't think, its a common observation in the first place. I had 2 receivers slaved on a motorized system, and experienced some other issues with loosing a recorded sat position in one receiver when switching to another. I traced it mentally to another cause. But I never experienced signal degradation, while watching 2 shows on a Pic-in-Pic screen with 2 receivers. Its fare to say, they were both of the same brand, but different models. Given current import trends, they were probably designed by different companies, certainly based on different hardware, but made in CN on the same factory, and again firmware was finalized by the same importer's team. No signal degradation though.

 

[B.J.]

If this observation is common, may be a DC Block in the Master's Loop Out port causes signal degradation when activated.
....
....
But I never experienced signal degradation, while watching 2 shows on a Pic-in-Pic screen with 2 receivers. .....

Happens even when not using the loop out port.
If you're watching 2 shows at same time via pic-in-pic, then both have locks. I don't get any degradation that way. It's when I switch the master receiver to a non-active transponder, so that it loses lock, then the slave suffers degradation that is apparently caused by the diseqC signals.

I first noticed this when listening to DSS audio on the 101 sat. The receiver I was using was slaved to one of my other receivers, but there was no signal to lock an FTA receiver on there, so the master receiver wouldn't be locked, and the reception would be poor. I finally figured it out that if I would just turn off the diseqC signal after selecting the port for the circular LNBF, that then it wouldn't be sending diseqC, and the reception would be good. Today, I was watching the MSNBC stuff on AMC6, on both master and slave, then, I'd switch the master to the transponder mentioned in another thread, looking to see if it had become active, and as soon as I'd switch transponders, I'd lose lock on the slave,even though it was the same polarity. Turn the diseqC port from 3 (linear) to OFF, and the slave would come back active again. The slave isn't connected through the pass-through, it's connected via a splitter.
I also have to turn the diseqC off to tune in Nimiq-5, since there aren't any transponders on that sat to lock onto. So I send the dish there, tune to a vertical transponder, selecting diseqc PORT-1 for circular, then turn off the diseqC , and then the slaved Genpix can then lock on the transponders.
This has happened with at least 4 different master receivers now and 2 different slaved receivers. I don't think the degradation is related to the receivers.

 

[pendragon]

If the master receiver does not have a lock, it may do all sorts of nasty things that would make it hard for the slave receiver to hold a lock on another signal. For example when my Pansat 9200HD does not have a lock, it will go through a process of dropping the LNB voltage completely, restoring it and resending the DiSEqC commands. This is made even worse if the 22 kHz tone is selected, because not only is that dropped when the LNB voltage is cut off, but anytime DiSEqC commands are being sent, the tone has to be shut down. The Pansat will repeat this every few seconds until it is able to lock. Other receivers may do similar or different things.

I used to have a splitter to my Pansat and spectrum analyzer so I could slave the SA off whatever I tuned on the STB. I was able to live with the interruptions when looking by eye, but when I started to capture data on a computer from the SA, this proved unacceptable. I now use a computer tuner as the master for the SA.

 

[zamar23]

B.J.

Sorry, I missed your "non-locking" point. Have to take some yoga classes now to improve concentration.

Apparently, having a Spectrum Analyzer takes one's guessing to a totally different level. I can't wait anymore for a long promised soft BLSA replacement.

 

[Hindu55]

Glad this was brought up.
On my setup here I have my Dynamic to the motor, then to 2 port DiSEqC switch
with port 1 to a linear dual and port 2 to a circular dual. On the same dish
I have the AzBox going to another 2 port DiSEqC switch with port 1 to the same
linear and port 2 to the same circular. A while back I had left a circular bird
and left the AzBox on port 2, Ran the Dynamic to a weak linear bird and could
not get a signal. At first I did not know what was wrong but after a little
testing, found out that with one box on the opposite port, it attenuated the
signal on the other receiver. Also, when Blind scanning with the Dynamic and
watching a feed on the same port with the AzBox, I see the signal cut out and
in through the scan. As long as they are on the same port and no scanning is
going on all is well.

 

[knowmiddlename]

If the master receiver does not have a lock, it may do all sorts of nasty things that would make it hard for the slave receiver to hold a lock on another signal...

I've also found that to be true. On a similar topic, my S/A loads the loop output of many receivers and I've considered installing a buffer amp for isolation but haven't tried that yet.

 

[pendragon]

I've also found that to be true. On a similar topic, my S/A loads the loop output of many receivers and I've considered installing a buffer amp for isolation but haven't tried that yet.

Good splitters have a high return loss, which is probably what you want.