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post #31 of 54 Old 07-31-2001, 06:24 PM
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I fixed up my spectrum analyzer so here some more stuff for our modulator file.

http://home.earthlink.net/~rogercc/_uimages/chan3tn.jpg zoom Here's channel 3 output from the modulator. It's way weird. The scan is 5mhz/cm, so the signal is almost 15mhz wide. It does quit on the high side at about the right point. Signal is weak.

http://home.earthlink.net/~rogercc/_uimages/chan4tn.jpg zoom Here's channel 4 output. Same fat mess shifted up 6 mhz.

http://home.earthlink.net/~rogercc/_...han65-66tn.jpg zoom Just so you know my analyzer isn't junk, this is what a real DTV signal should look like. All settings on the analyzer are the same except frequency has been shifted up to 782 mh. What you see here are two adjacent DTV stations (chan65 and chan66). Note that they are about 10 to 15 db stronger than the modulator, and are exactly 6 mhz wide each. You can see the dip between the two. The other junk on the screen is analog.

http://home.earthlink.net/~rogercc/_...s/input-tn.jpg zoom Here's a better shot of the modulator input area. Does anybody out there have info source for the Zenith chip (T3W41AF), or knowledge of the input circuits? Why 3 coils?

------------------
-Roger
Analog -- Always out of adjustment.
Digital -- Always one more bug.

-Roger
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post #32 of 54 Old 07-31-2001, 11:53 PM
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Interesting, Roger! I'd love to get your scope on my pre-production modulators. http://www.avsforum.com/ubb/smile.gif

So, if the production modulator is outputting a 15Mhz wide signal, but our tuners are able to lock on & decode the MPEG stream, I'd surmise that the essential data all resides within the proper 6Mhz channel. Therefore, putting an appropriate bandpass (I love the way the forum spell checker suggests "badass" instead!) filter on the output should allow it to co-exist with adjacent channel signals.

While most of the info in this article is quite dated (interesting info on MUSE, though), this diagram from the article illustrates the difference in waveform between ATSC (top) and NTSC signals. My guess is that no bandpass filter which was designed for NTSC use achieves such a sharp cutoff that the sidebands would be attenuated too much.
http://www.ee.washington.edu/consele...hdtv/95x54.gif

I'll be trying something like this (using a Blonder Tongue CATV headend filter) within the next week. (Actually, not trying to combine ch 3 & 4 Dish modulators, but injecting the ATSC ch 3 modulator signal into an OTA feed which includes an NTSC ch 4 signal. But since my objective is to combine the modulator output with the ATSC signals in the OTA feed I may use a ch 4 elimination filter if that's what it takes.) I'll report the results here.


------------------
Peter

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post #33 of 54 Old 08-01-2001, 03:15 PM
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Well, Peter, if you ever make it down to SoCal let me know. Or, you could just send me one of those old things. I promise I'll send it back.http://www.avsforum.com/ubb/wink.gif

It looks like balaser was right about the sidebands (I wonder if spell check will suggest sideburns). Across the top it looks like about 12 mhz, and sloping off less steeply than the broadcast standard.

This site has a variety of narrow notch filters and tunable filters in addition to badass filters.

------------------
-Roger
Analog -- Always out of adjustment.
Digital -- Always one more bug.

-Roger
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post #34 of 54 Old 08-01-2001, 07:57 PM
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Gridleak,

I didn't measure the width of the 5000Mod output at the 3db points, but the shape of your spectra (OTA & 5000) are just what I remember seeing with the 5000mod set for channel 3.

However, your ch4 spectrum exhibits a surprising amount of tilt compared with the flat top when set to ch3. I wonder what this is due to.

When I'm set up again, I'll set the 5000mod to ch 4 to see if I also have tilt.

Thanks for the pictures.
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post #35 of 54 Old 08-01-2001, 09:59 PM
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Hey, Roger, why not just send that scope up NoCal way? http://www.avsforum.com/ubb/biggrin.gif


------------------
Peter

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post #36 of 54 Old 08-01-2001, 11:21 PM
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It's clearly a shipping weight issue. My Spectrum Analyzers 40 pounds vs. your puny modulators 40 ounces.http://www.avsforum.com/ubb/tongue.gif


------------------
-Roger
Analog -- Always out of adjustment.
Digital -- Always one more bug.

-Roger
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post #37 of 54 Old 08-01-2001, 11:22 PM
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I am in Bay area and do have a HP 8594E spectrum analyzer. Maybe we could get together sometime and "check out" your preproduction modulators and compare them with the production ones I have.
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post #38 of 54 Old 08-01-2001, 11:58 PM
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Roger -

Your logic is unassailable. http://www.avsforum.com/ubb/frown.gif But I think I'll take Orio up on his offer instead, OK? http://www.avsforum.com/ubb/wink.gif

Orio -

Sounds good! I'm pretty busy right now planning for my wedding,http://www.avsforum.com/ubb/rolleyes.gif but we should be able to schedule something in about 2 weeks. I'll send you some email.

------------------
Peter

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post #39 of 54 Old 08-02-2001, 12:50 AM
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Congrats, Peter. Does she know about your nasty HD habit?

------------------
-Roger
Analog -- Always out of adjustment.
Digital -- Always one more bug.

-Roger
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post #40 of 54 Old 08-02-2001, 08:41 PM
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Roger -

Keeps me home at night. Need I say more?

------------------
Peter

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post #41 of 54 Old 08-03-2001, 12:24 AM
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Peter, tell us where you're going for the honeymoon.

I know you'll set timers to record stuff while you're gone, but who's going to change the tapes?

------------------
-Roger
Analog -- Always out of adjustment.
Digital -- Always one more bug.

-Roger
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post #42 of 54 Old 08-03-2001, 03:51 PM
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Hey, congrats Peter. Guess you don't plan on bringing out the HD cam with you to the islands? http://www.avsforum.com/ubb/smile.gif
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post #43 of 54 Old 08-03-2001, 09:46 PM
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Quote:
...who's going to change the tapes?
Well, Roger, if my HD habit keeps me home at night, you've hit on what keeps me awake at night!

Barbara & I will be in Hawaii, enjoying the surf & sand. I'll (be trying to) not think about HD one bit. (Yeah, right...)

------------------
Peter

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post #44 of 54 Old 08-06-2001, 12:47 AM
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Hey, James, good to hear from you again!

Hmmm, an HD Cam...

Now there's a piece of gear I don't have yet. http://www.avsforum.com/ubb/wink.gif

------------------
Peter

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post #45 of 54 Old 12-01-2001, 10:15 PM
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This thread kind of died out, but I have been accumulating bandpass filters and various other RF equipment to try to combine my 5000 modulator outputs. I also have DISH and ExpressVu and want to combine those along with my OTA so I can send one coax thru out my house that can carry everything to DST50s instead of having sat receivers everywhere. Kind of like being my own Cable company multiplexing signals together on one wire.

Anyway, in the meantime I came across an original modulator like Peterd talked about that outputs on 14/15. Unfortunately, when I plug it into the IRD, I get an onscreen message that says "HD modulator memory is corrupt, unplug unit for 10 minutes and try again". I have 2 DISH 5000 receivers and tried it with both, I also have 2 of the consumer HD adaptors, and they both work in those receivers. Neither of the LEDs on the back light up, and the DISH channel guide actually deletes the HD channels while this modulator is plugged in.

Has anybody seen this? Also, interesting things to be seen inside this box. There is a pot labeled "RF level adjust" also "Pilot level adjust". Everything is very clearly labeled such as "Clock Frequency 19.392658", "To 8vsb board" a "test/normal jumper" and 2 leds, one for "normal" and one for "error". Also, the chnl 14/15 is set with a switch on the back, and not by the software in the receiver. There are test points everywhere on the 8vsb board.

Looking at the cable from the HD board to the 8vsb board, it reminds me of when I installed an SDI board in my DVD player last week, and ran the ribbon cable over. Hmmmmmm.....

Any comments appreciated,

Jay

"Can I please just watch this the way it was meant to be seen?"
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post #46 of 54 Old 12-02-2001, 10:17 PM
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Jay, please let us know in detail (makes and models) about the bandpass filters and other equipment that you've used to construct your all-on-one-coax solution.

I had a bad experience with a Tru-Spec channel combiner that ruined six months of recordings.

Ron Gomes
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post #47 of 54 Old 12-02-2001, 10:38 PM
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>This thread kind of died out, but I have been accumulating >bandpass filters and various other RF equipment to try to >combine my 5000 modulator outputs. I also have DISH and >ExpressVu and want to combine those along with my OTA so I >can send one coax thru out my house that can carry everything >to DST50s instead of having sat receivers everywhere. Kind of >ike being my own Cable company multiplexing signals together >on one wire.
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post #48 of 54 Old 12-02-2001, 10:42 PM
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>This thread kind of died out, but I have been accumulating >bandpass filters and various other RF equipment to try to >combine my 5000 modulator outputs. I also have DISH and >ExpressVu and want to combine those along with my OTA so I >can send one coax thru out my house that can carry everything >to DST50s instead of having sat receivers everywhere. Kind of >ike being my own Cable company multiplexing signals together >on one wire.


Have you successfully used a 5000+modulator with ExpressVu? I have tried getting one of my 5000+modulator setups working with ExpressVu, but the receiver won't take any updates on the Nimiq satellite. I guess Bell isn't sending updates for the 5000 series receivers since the release of the 6000.

Thanks.

Bill.
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post #49 of 54 Old 12-02-2001, 11:11 PM
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rrg,

So far I have just been buying parts to do this, but haven't assembled them all into a working solution yet. There is no guarantee it will work at all. I have notch filters that remove a single channel, I would use a channel 4 notch filter to remove the upper sideband or bleedover from the chnl 3 modulator. I have channel pass filters that only pass one channel, I would use a channel 4 bandpass to remove the lower sideband that is bleeding into channel 3. I also have a couple of devices that shift a VHF channel to the UHF band, but I don't have much faith that this will work with an 8vsb signal. In the next week or so I should have results to report back.

How did the Tru-spec combiner wreck your recordings?

Bill,

Yes I have a 5000 and modulator working with ExpressVu, unfortunately I'm "testing" it right now, if you know what I mean. I'm trying to get a legit sub with it, but it's not easy. Only about 200 model 5000s were authorized for use with the Bell system, mostly as Demo pieces for dealers before the 6000 came out. As far as taking a software update, I doubt there is a 5000 update in the stream since so few were made, but if you aim at Nimiq1 and set your box to transponder 11, you will load the ExpressVu channel guide. It will be just a few channels at first, but after a few hours you will have the entire guide and will actually be able to watch channels 198 and 199, low-def of course. One of those is the CBC news channel I think. Anybody with a DISH 5000 and a Dish card can do this. But let me say, I'm not entirely sure what software updates are made to your box, and I haven't tried aiming back at DISH satellites after this to confirm that they return to normal. So experiment at your own risk.

Jay

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post #50 of 54 Old 12-03-2001, 07:32 AM
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Quote:
Originally posted by J_Nemeth
How did the Tru-spec combiner wreck your recordings?
I described it in more detail in this thread, but the gist is that I had persistent digital breakup problems that I could not eliminate until I replaced the channel combiner with a simple A/B switch. I've had very little problem with breakup since then. And I'm still slowly replacing movies that were recorded during those first six months, as they're rebroadcast on HBO and Showtime.

My guess was that the strong OTA signal on Ch. 4 was interfering. But I don't really know. I'm reluctant to experiment now because it's time and it's trouble and it ruins recordings.

I'd still love to simplify my setup and send all the digital signals around the house on one wire.

Ron Gomes
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post #51 of 54 Old 12-03-2001, 08:23 PM
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I thought this was a dead issue, but I'm heartened to see effort still being made.

Thanks and good luck. Please continue to keep us in the loop.

'Better Living Through Modern, Expensive, Electronic Devices'

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post #52 of 54 Old 12-05-2001, 03:57 PM
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The thread, that is. Me - I'm only back from my honeymoon. :D

Jay -

Quote:
I came across an original modulator ... Unfortunately, when I plug it into the IRD, I get an onscreen message that says "HD modulator memory is corrupt..."
Unfortunately, you may be SOL. I tried this with the same results.

It appears that the original firmware from the IRDs (mine show as version A001B) was blissfully ignorant of the modulator. Since the consumer version uses firmware control to select the output channel (rather than the slide switch on the pre-production units), the IRD needs to talk to the modulator. The later firmware supports this (as well as switching the OTA pass-through input). My guess is that the mechanism for this is to simply map the control addresses onboard the modulator into a portion of the memory in the IRD (and control the modulator by reading from and writing to these addresses). When connected to the older modulator, the initialization of this mechanism fails since the STB can't find the expected values there and assumes the memory must be corrupt.

PM me so we can trade email addresses and discuss possibly testing your modulator with an original IRD.

As to the other issues:

I think you should be able to shift the VHF output of one of the modulators to UHF, as the ATSC signal is designed to fit within the same bandwidth as an ordinary NTSC channel.

Why not subscribe another IRD to BEV (perhaps their 5100 PVR)? Since they don't charge extra for multiple IRDs, you'd be able to "do the right thing" and continue "testing" your 5000 indefinitely.

Earlier I had written that I had a temporary setup using ordinary splitters and a consumer broadband amp to combine multiple modulator outputs (but didn't have OTA hooked in at the time). I, too, was collecting pieces to try better filtering and combining the signals. I've since done further experimentation, but have gone back to what I still consider to be a temporary setup ('though with OTA now).

Here's what I found of most significance:

1st, signal levels are all over the place. Between the various OTA DTV signals I receive, there's a wide variance in levels. Further, the channel 3/4 output of the production Dish modulator is the lowest of all. It is about 30db below the other (ch 14/15) modulators.

2nd, my measurements confirm Roger's observation that the production modulators splatter down one full channel's worth (I was using a meter, though, not a scope).

Finally, make sure all the filters, combiners, amps, etc. are rated to pass the full UHF spectrum if you'll be including OTA signals. I wound up scratching my head when I lost most of the OTA channels. Turns out that the combiner and ch 14 notch filter I had were CATV units rated only to 550 Mhz.

Currently, I have the following setup:


Code:
                        +-+                   +-+        +-+
OTA ------------------->| |                   | |------->| | TU-DST50
                        | |                   | |        +-+
ch14 ------------------>| |                   | |
                        | |                   | |        +-+
ch15 ------------------>| |------------------>| |------->| | TU-DST50
                        | |                   | |        +-+
                        | |                   | |
                        | |                   | |        +-+
                        | |                   | |------->| | TU-DST50
            +-+         | |                   | |        +-+
ch3 ------->| |-------->| |                   | |
            +-+         | |                   | |        +-+
                        | |                   | |------->| | Dish 6000
          VHF/UHF       +-+                   +-+        +-+
            Amp  
                       4-way                4 output
                      Combiner              VHF/UHF
                     (splitter)               Amp


The channel 3 signal is boosted around 30db by a consumer VHF/UHF RF amp (Radio Shack). That, the OTA antenna feed and the other modulator outputs run into a combiner (actually a splitter with inputs & outputs reversed) and the combined signal is fed into a Channel Master consumer amp which has 4 outputs.

That's it. No filters. I did not have access to the meter after experimenting with the other components, so I tuned this by the seat of the pants. This setup is reasonably stable now, but weather does affect the OTA DTV reception. Also, the NTSC reception on ch 4 is pretty poor. I suspect this has to do with the splatter from the ch 3 modulator.

Eventually, I'd like to take a pass at this with a spectrum analyzer and replace the RS amp with a single channel (or at least low VHF only) amp and the other with a tri-band amp (with separately adjustable low VHF, high VHF and UHF levels). I'd like to put back the ch 3 bandpass filter as well (but it appears to have too much insertion loss without further amplification, so I'm not using it at the moment). Also, I get away without the ch14 channel elimination filter at the moment since the OTA signal there is weak. However, I might have to add one back in once I even out the low VHF, high VHF and UHF levels.

Peter
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post #53 of 54 Old 12-05-2001, 04:52 PM
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Nice to see you back, Peter. Incredibly long honeymoon --- you must be exhausted.:)

-Roger
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post #54 of 54 Old 12-05-2001, 10:22 PM
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Hi Peter,

I figured you would be the one that would know what was going on with the modulator, I was thinking along those lines earlier but was in denial. I'll PM you.

As soon as I get my buddy's spectrum analyzer over here, we're gonna have an RF party with this pile of stuff. It's really hard to know where the problem is or where the weak link is between filters, amps, weak modulators and insensitive DST50s without being able to see the signal.

Unless I can get the 14/15 modulator to work, I will still have to make 2 of the 3/4 modulators coexist. If it works I'll post the secret formula here.

Jay

"Can I please just watch this the way it was meant to be seen?"
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