DBSTalk Forum banner

d575d Destacker/Mitsubishi SR-HD5 problems

1565 Views 3 Replies 1 Participant Last post by  akropp
My apartment building uses a "wideband" signal to distribute directv to all of the units by stacking the two sets of transponders. They gave me a Sony B50 receiver which can use the wideband signal directly, but I'd rather use my Mitsubishi SR-HD5 (nicer picture, component out, digital audio out). They also gave me a Sonora Design d575d subscriber unit "destacker" which is supposed to let me do that, but I don't receive all of the transponders (most notably whichever one carries the guide data).

It appears that I am losing the bottom end of the spectrum. Of the odd transponders (the ones that are passed through unchanged), I don't get 1 and 3 at all, sometimes get 5 very faintly (20-30%), get 7 at 65%, and get all of the higher ones fine. I get all of the even (stacked) transponders fine.

Checking whether the subscriber unit was bad, I switched the Sony receiver out of wideband mode, and hooked it up -- worked fine. I get all of the transponders at very respectable levels. It seems that somehow my receiver doesn't work well with the d575d.

Has anyone seen anything like this? Do I need to get an amplifier to boost the signal before it goes into the destacker? Perhaps the Mitsubishi receiver doesn't put out the right voltage levels (or enough current) to power the destacker?

I haven't been able to find much discussion anywhere about the "wideband" signals, and nothing at all in relation to my receiver. Any help would be appreciated.
Not open for further replies.
1 - 4 of 4 Posts
A DSS receiver needs a minimum signal level of about -65dBm to operate properly, and a signal to noise ratio of about 8dB. Unlike analog signals, a digital signal that is below the threshold input level of a receiver can sometimes be recovered through amplification. I have seen signals that had dropped to about -75dBm recovered that way, though you may not have the same luck in an MDU since the signal may have gone through more stages of amplification and picked up more 3rd order intermodulation distortion than did the signal that I saw recovered in a technical seminar at WSNet's headquarters back in 1997.

I believe a Sonora D575 amplifies the evens but not the odds. The logistical problem you face is that the D575 does not pass power to the amplifier. so to add an inexpensive, inline amplifier to your drop you will either have to put it between the destacker and the receiver or you will have to use a power inserter and possibly a voltage blocking coupler on the other side.

Can someone from your MDU operating company do a signal level check in your unit? A properly designed MDU distribution system should develop a wallplate level of about 55dBm. Sonora engineers really severe reverse tilt into their commercial line extender amplifiers, and because of that, it is actually more common for a Sonora system to lose transponders at the low end of the spectrum (1, 3, 5) as the signal becomes weak than it is to lose them at the upper end (30, 32).
See less See more
This is more or less what I suspect is happening. The guy who set me up seemed perplexed that it wasn't working, but he didn't do a signal level check. I think I will have them come back in and check.
I have tried using two other receivers with the d575 (a Sony B-50 and an old RCA), and they both have no problem receiving a signal. All of the transponders are up at 80-90% on the signal meter. When I hook up the Mitsubishi receiver, the low transponders are all really low.

Interestingly, if I hook up the d575 directly to the wall plate, I get no signal on transponders 1 and 3. If I hook it up after a splitter (with a 6db loss), I get some signal on 1 and 3 (around 40%). Apparently this is not enough for the receiver to function though. Could it be that the incoming signal is too strong? This was rather surprising behavior.

On a side note, what transponder is the guide data transmitted over? I'm assuming it is 1, since my receiver can't get the guide data.
1 - 4 of 4 Posts
Not open for further replies.