RF Distribution Amp/Splitter

[vintage.digi]

I'm looking for advice on my NTSC RF setup and I'm not sure where to turn with this being a dead art.

I'm creating my own playlists that are running into Pico Macom MMA860S RF modulators, and then the output of those is going to a Blonder Tongue output combiner. At this point I have one RF cable with my 4 channels, but that's where I'm not sure what I need next. I want to split the signal to various TVs around my office building.

My office consists of two buildings put together and I would like to have an 8-way splitter in one building daisy-chained to an 8-way splitter in the other building, to simplify runs.

Could anyone give me advice as to the proper way to do this without signal loss, or point me in the right direction to find out?

Thank you!

[DavGoodlin]

For a similar setup with four VHF channels and broadcast distance less than 100 feet, I use custom cut 1/4 wave antennas on the output of the modulators, located in an attic of my garage, which broadcasts to the house and outbuilding. I picked RF channels that are not active locally. These WILL affect DTV reception and the 65" LCD will scan them all as analog channels. LOL

It sounds like you need an amplifier if you're using more than 50 feet of RG-6 cable, or splitting off to more than 2 sets. Look for Blonder Tongue BIDA-50 or similar amp, that covers up to 500 mhz unless using UHF, then a 750 mhz is better.

The issue with combining analog or digital RF channels is that losses in cable and splitters is different for every channel. Each 2-way splitter drops the signal -3.5 dB. Runs of RG-6 cable typically lose 3.0 dB per 100 feet on VHF High band, RG-11 is about half the RG6 loss and recommended for UHF run over 100 feet

Also important is flatness of response within the 6mhz channel, otherwise sound, video or chroma will be affected. If you can get a spectrum analyzer to look at each channel at each outlet, this is helpful to identify and correct with a gain, "tilt or slope" adjustment that some amplifiers have.

[Electronic M]

I transmitted too... My Blonder Tongue AM60 modulators can be recieved a block away from my house when output is set to max. It's a lot less hassle with 100 TVs on 3 floors than wired options....Granted steel frame office buildings may not be as condusive to wireless RF as wired RF.

Blonder Tongue hotel distribution amplifiers ar probably the way to go for wired distribution.

[vintage.digi]

I'm looking to buy coax cable right now but I'm unsure what to get. It looks like my longest run is somewhere around 116 ft. I had no plans to use UHF channels, but would it be of benefit to do so? I'm planning on doing a maximum of 4 channels.

Would RG11 be better no matter what, or would it be entirely pointless to get RG11 vs. RG6 for my use? There are so many types of coax cable, apparently. I never knew.

My building is metal and it blocks cell phone signal almost entirely, so I assumed there would be little hope of broadcasting successfully via an antenna. I might experiment with it down the line, but at first I'd just like to get a few of my favorite TVs hooked up directly. It seems like a few of them are having some fussiness with RF reception anyway, so troubleshooting problems would probably be easier if I know the connection is physical.

[ChrisW6ATV]

RG-6 should be fine for that distance. To ensure the best quality in the further-away building, I would go from your combiner's output maybe into an RF amplifier, then into a two-way splitter. Feed that splitter's output into the two buildings, with the eight-way splitters in each building.

TV signal distribution is always a matter of gains and losses, and adding gain in advance of the losses when necessary. Your four-way combiner likely adds about 6 dB of loss per channel (or higher if it has more inputs), unless it has an amplifier built in. Two-way splitters add 3 dB of loss, the eight-way splitters will add 9 dB or more, and so on. So, an RF amp with 12 dB or more of gain will compensate for those losses, and also the loss in the cables.

Stick with VHF rather than UHF to minimize losses.

[vintage.digi]

Okay, it's been a while but the installation is slowly moving forward. I've got coax run to four different spots in my office for various televisions. I'd like to also do a wireless broadcast though, so that I can set up more of my misc TVs to be functional. I've got a lot of questions though and I'm hoping I can get a little guidance on this.

For an amplifier, I have an RMDA-750-30. From that, I plan to run into an 8-way splitter, and then into coax cables that go to various places in the two buildings. I abandoned the idea of having a splitter in each building and instead opted to have all coax terminate in the same place. What I'd like to do, if possible, is to have an antenna in each building, transmitting within that building.

First, what sort of device would I need to broadcast in this manner? I see mention of using an agile modulator with an antenna, but in my case, I have all of the channels already combined into one coax cable. Is it possible to broadcast that signal with four channels in one, or would each channel need to be broadcast separately? If they need to be broadcast separately then that would complicate things as each output would need to be split for coax and wireless.

Assuming that's all even possible, is it acceptable to have two transmitters like that in close proximity? Signal transmission in my office is pretty bad. Cell phones don't work here and generally a cordless phone signal won't go from one building to another. However, if the internal garage door is open, then you can pass some cordless phone signal through the building. So, I'm worried if there was some bleed through with the television signal, would that ruin the video? Would a TV pick up a little of both? I imagine that there might be a slight difference in timing between the two broadcasts. I suppose one thing I could do is to use the same amount of cable for both runs.

Is it possible to accomplish what I'm trying to do? I hope this wasn't too confusing.

[Alex KL-1]

I dunno if maybe ghosting (in analog) and screen mute (digital) will occur with various antennas, if simultaneously various garages/doors are open at same time.... or if will not be a problem, if not bother nobody (if exists, anyone have this field experience here)?

About centralized splitters vs cascade, is important to assembly something easy to troubleshooting in the future (the most easy considering the actual physical characteristics of the buildings), including easy of changing cables if needed.

I'm working at a place with some metal buildings, including some Faraday rooms for electronic labs, and for that, cable comms are guaranteed. So is the safest workable route.

[Electronic M]

Transmitting is possible, but some of your suggested methods may or may not work as intended.

Combining wired and wireless from the same modulators seems like a recipe for troublesome complications.

I know there are some people who have used a combiner to feed the same modulators to a single antenna, but they usually have to eat 6dB of loss. Finding a distribution amp that can output the 60dBmV necessary for transmitting is difficult.

Most folks who transmit do so with multiple agile modulators and as many antennas as modulators. I've got Ch7 and Ch9 modulators and antennas right next to each other and it's fine...Granted I have the dipoles facing orthogonal directions to minimize coupling between them.

I recommend having the wired and wireless on different channels. On sets with 300 ohm input you'll get multipath from the wired and wireless and that can cause a variety of issues.

[zeno]

There were books on designing MATV & CATV systems in the
olden days. It can get deep. You are going beyond just wiring a
house with 4 outlets. That was common work. Just a distribution
amp & coupler etc. All of high quality & old brand names.
No place for Chi-com amps !

73 Zeno
LFOD !