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On a somewhat separate point, I did notice interruptions on the TV screen at the start of movies during the opening credits and during navigation using the Zidoos controls causing drop-outs in signal from the SDK2018. Using my Applied Instruments XR-3, the signal level fluctuated and the MER level dropped to zero causing a unlock status. Problem was, It all happens so fast and brief, it's kinda hard to keep my eye on the TV, the meter & the SDK all at once.
I will have to run some more tests.
 

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Discussion Starter · #22 · (Edited)
Unfortunately it appears this modulator is no longer listed at eBay. AliExpress does list it, at the same $237 price, but says it's "no longer available." Pity; it was a great deal while it lasted (nearly 2 years).

The Thor Petit is still available, but costs nearly twice as much. The Stellar Labs modulator has gone up too. At this point the best deal for those looking for an ATSC modulator under $300 would seem to be the new Channel Master one (for now, just barely under $300 at $299), which appears to be a version of the Stellar Labs modulator with some much-needed updates.
 

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Discussion Starter · #23 ·
I just ran across an eBay listing for a "blade" style ATSC/J.83B (aka QAM) modulator by the same seller and for the same price as the Souka modulator. Unfortunately the seller only has one. I had already given up on trying to find the Souka modulator and ordered a Channel Master one instead, so I don't know anything about this one. I would expect it to be similar in functionality to the Souka modulator, but no guarantees.

This "blade" version lacks either HDMI or an RF pass-through, so you'll have to use an HDMI splitter or RF splitter/combiner if you need those functions.

The seller also has one (sigh) blade-style ATSC modulator listed with a composite video input instead of HDMI for under $200. That doesn't seem as useful, but it might come in handy if you need to convert the output of an old VCR, DVD player, or the like to digital so you can tune it with a digital-only tuner or DVR.
 

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Discussion Starter · #24 ·
Warning
Do not connect the RF input of this modulator directly to an antenna! It turns out that the modulator has significant "backwash" that escapes through the RF input, and would be broadcast by an antenna connected to it.

The new modulator from Channel Master was found to have the same issue, so I checked both my Channel Master modulator and my SKD2018 and they both do this.

@rabbit73 checked his Thor Petit (which the SKD2018 is a clone of) and found the same issue with it too, so this appears to be quite common.

To avoid unintended broadcasting, you could do one or more of the following:
  1. Place a unidirectional amplifier after the antenna
  2. Place a low-pass, high-pass, or band-stop filter after the antenna and set the modulator to a frequency the filter doesn't pass (a Channel Master LTE filter would be ideal; just set the modulator well above RF 37).
  3. Eschew the modulator's RF input, instead combining its output with the antenna using a signal splitter in reverse. A typical signal splitter would have about 3.5dB insertion loss but would provide much better isolation between the two inputs being combined. (To avoid the insertion loss, if there are no VHF-Lo stations in your area, you could use an HLSJ instead of a reversed splitter; connect the antenna to the Hi input and the modulator to the Lo input, and set it to RF 2 through 6.)
 

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As I stated before, the loss thru both of these is high. 4.5db.

Just don't use the input at all. Put a terminator on it and use a high value 'tap' (in reverse of at least 12db) to combine the output w/ an antenna feed.

That solve both problems. ;)
 
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As I stated before, the loss thru both of these is high. 4.5db.

Just don't use the input at all. Put a terminator on it and use a high value 'tap' (in reverse of at least 12db) to combine the output w/ an antenna feed.

That solve both problems. ;)
I've used a modulator with a reverse splitters. It's not easy to get the modulator output set just right. Takes some work. I'm not convinced many modulators produce a real clean signal.
 
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