I know there are a couple other folks on here who have some experience in the land mobile / commercial radio disciplines...

I'm either imagining things or just can't find what I'm looking for. I was sure that somewhere in trade magazines or the like that I'd seen a thing for a distributed antenna system that was a sort of tap that attached to heliax, such that you could run a length of heliax down a tunnel or hallway or the like and put these taps on and attach antennas. This ring a bell with anyone? Working on a weird coverage situation and a kind of in-building distributed antenna system I think would be the best option. I've never installed radiating coax before but I don't think it will work well in this particular situation.

This is a real thing. And quite common. No "taps". Appropriate Google search terms would be "leaky cables" or "radiating cables". You can buy a solution for any frequency VHF on up.

I'm familiar with leaky cables/radiating cables, but I'm not sure one will work in this particular installation. The taps thing would be ideal vs trying to put in power dividers and run multiple cables all over. I'm sure I've seen that somewhere, when I saw it it reminded me of a fire sprinkler system.

Are you trying to reinforce UHF/VHF or cellular? Most distributed antennas function similarly: BDA runs signal over Coax or fiber to antennas to reinforce whatever RF signal you’re trying to push. There are other options depending on what signal you’re trying to reinforce.

UHF in an in-building industrial environment. Repeater antenna is on the roof, but it's an all-metal building with a bunch of faraday-cage like compartments inside.

If you are just trying to cover the building and not the area around this will work. Repeater on bottom floor or in basement. Antenna on roof. Run radiax on the inside down to the floor just above the repeater. I always ran it down an elevator shaft or stairwell.

As an example, what I'm talking about is an alternative to a product like this:

Attached File

https://microlabtech.com/dn-44fn.html

But the product/system I thought I had seen just attached to the side of hardline cable instead of requiring input and output connectors. Apparently I'm not remembering the right kind of thing as it doesn't seem to exist.

We used to use vampire taps for in building radiating cable stuff, but have moved away from it due to inconsistency in installation quality. Now, just cut and terminate cable, then use dividers or taps to get her done. I have done this activity for several Moto radio shops in the past and do similar work for my current employer. We could always get you a basic design and you could implement it yourself (call in a local radio shop to terminate and test the cabling, if you dont have the tools). TT

I'm starting to reconsider radiating cable. Use a power divider to put a couple antennas where they need to be, and a couple runs of radiating cable to cover the rest. I just don't have any experience with radiating cable to know if it will perform correctly. Also if it will work for a cell phone in-building system which is also in the works.

If you are having a cell DAS system I stalled, then I would recommend working with that integrator to see how much extra it would take to fold the radio system into the DAS.

How poor is the coverage now? What frequency band? What type of building (warehouse, office, 1 story, 10 stories, etc)? Do you need a few more dB in a few locations or is it totally dark in the areas you want to cover?

I usually perform a basic coverage walk of the property to get a feel for the system. Typically, from the subscriber perspective, if you are receiving the system at stronger than-95 to -100, you should be able to get back into it. If you cant, thenthe system has issues.

If the properly working system does not have desired coverage, you have to identify the total area needing coverage. Often, I can run a 50/50 power divider and then run a cable from the outdoor antenna to the lower portion of the building needing coverage. To determine if this would work, select a place for the internal antenna and then use a simplex frequency. Talk from portable to portable from where you think the inside antenna would be placed. If you can talk from portable to portable, then you are very likely to be able to talk with a repeater antenna at that location.

Hope this isnt too convoluted. TT

I'm almost confusing myself, the UHF repeater and cell phone systems are two different projects in different places.

One problem with the UHF project is it's not practical to do the kind of experiment you suggest, access to the area is pretty limited.

I've worked on a few UHF DAS (not BDA) systems where we interfaced directly to the repeater(s). Vampire taps are very inconsistent and don't handle power well so unless you are going to be feeding the DAS via an ISO-T I wouldn't recommend it. The traditional power dividers and 10 dB taps are the way I would go about it. I also would not personally use radiax. It's handy in tunnels but in building I find traditional DAS antennas work better.

This is how I've been leaning. Any suggestion on what taps to use... I found those Microlab brand on a website for the cellular extenders.

When I was thinking about the "vampire" taps I was contemplating how to go about installing somewhere between 25 and 50 taps, but I think I'll be ok with a smaller number.

Comba is and CommScope are my go to's. It looks like Microlab does make some stuff that will cover LMR it just isn't as simple to find.

Tessco seems to have an okay selection you just have to keep power input and bandwidth in mind. Probably start off with your furthest run and work you way back to figure out what kind of setup you need exactly.

Tessco's website is such a PITA anymore, I can't find anything.

I'm glad I'm not the only one who things that things have gotten really difficult to find over the last 5 or 6 years now.

Tessco went from not great to terrible. TT