Batboard

Moderator- I posted this under a topic I started several days ago but it has gone from DVRS recommendations to asking board members about running dual antennas. I'd like to repost it as a new topic since its nowhere near DVRS recommendations anymore.
My problem is this; we are using XTS5000's in armored trucks and our signal suffers because of it. Another board member suggested plugging a roof mounted antenna into the portable via SMA adapter and just switching back when needed. That was my intial thought, but ran into the problem of having to rapidly dismount the trucks so in my research I came up with an idea but I'm not sure if it will work. We have the radios attached to our vests generally out the way and it is cumbersome to do anything but change channels/volume and they are wired with an extended antenna secured to the Molle straps on the vest. If we have to dismount in an emergent situation we don't have time to unscrew the roof mount and screw the extended antenna back in, which would be next to impossible to do anyway with the way we have them attached. I saw that the XTS5000 series uses an RF adapter for the public safety mic which led me to another thread here. The guy was asking what adapter to use for a roof mount and the replies said an SMA to BNC. I looked up the adapters and saw that they have Tee connectors. I am mechanically inclined, but lack the electrical engineering to know if this will work. My idea is this...use a Male SMA - whatever style connector for roof mount antenna - Female SMA Tee style connector to:
1) Male SMA to plug into the radio, 2) whatever style connector for roof mount antenna to plug a short pig tail with a male phono type jack which then plugs into a female phono type jack and continues out to the roof mount antenna (this would serve as a quick disconnect from the roof mount antenna), 3) Female SMA to plug the extended antenna into. This would serve two purposes, it would allow us to keep the extended antenna plugged in AND give us the roof mount antenna we need with a quick disconnect when we dismount.
My questions are this:
Is it possible to have both antennas attached at the same time?

And if so, I think we are setting up the radios to operate both UHF/VHF freq's by switching from the "A" bank to "C" bank. Will the connectors and roof mount antenna support both types of bands?

I'm not sure of the connector type for the roof mount antenna or even which type of roof mount antenna I need, can anyone tell me what you think would be best? It's basically for comm's between 3 trucks using XTS5000's, spread out maybe a mile or so.

If the pigtail idea will work the connector can be considered permanently attached. If not, I would need some kind of terminating quick disconnect to plug into the Tee connector.

Regarding the roof mount antenna itself, can you suggest a vendor that would be able to supply an antenna with the wire as I described with the phono type jacks and pigtail with the connector?

Regards,
John

It is generally not good practice to double terminate an antenna. It will kinda sorta work, kinda sorta not as well as you hoped.

In my experience, a pig tail for guys to jack in and out of their radios becomes a high maintenance item. I suggest a mobile radio in each truck.

A thick roof mount antenna kit should work for you cab. There are dual band antennas for VHF and UHF.

The XTS5000 is not dual band UHF/VHF capable...it's one or the other. The RF switch used for public safety mics, and for the in-vehicle XTVA, looks like this:



It has an SMA male connector at the top, for the standard portable antennas. I don't know if something similar exists in a tee connector for what you're trying to do. There are certainly SMA tee connectors:

http://canada.newark.com/amphenol-conne ... dp/99H5069

However, I can't find any SMA-to-phono adapters. Your best bet might be to use the SMA tee connector I linked to above, and fashion an SMA-to-phono jumper cable to allow quick connect/disconnect from the vehicle antenna. It would leave a jumper connected to the radio, but if you have it fastened to your outfit with a velcro strap or the like, it might be ok.

Obviously this is not an ideal arrangement. Will it affect your portable range with a tee connector and jumper cable connected when outside of the vehicle? Probably...how much I can't say, but I believe it would be minimal.

Another thought might be to explore a passive antenna system...ie: try to give the RF a 'path' to follow out of the vehicle. You could try a test with a couple of mag-mounts connected together with the cable passed out the window. Have say a 1/4-wave whip antenna inside, located as close as practical to where the driver & passenger(s) sit. Use a high-gain whip outside. Duplicate this setup in a couple of trucks and see how far away you can get from one another, and if it's any different than without it.

You know, this just occured to me why I haven't seen a single antenna on an armored truck around here. Sure enough, I asked a buddy of mine who works in an armored car and he says he uses all portables in the truck, however they only work in the city area and of course get a great city grade signal from a local LTR system. The reason like you mentioned is for safety purposes like in an truck jacking and what not.

Now understanding the situation better, I can think of two suggestions. One would be to put a decent SMA to BNC adapter on the radio and use a decent BNC Rubber duck from Larsen for when you step out of the truck. When you get back in, you just remove the BNC duck from the radio and then connect it to a thick NMO mount antenna terminated with a BNC connector which you just connect to your portable on the vest. BNC is quicker to switch out instead of SMA. When I was a stupider radio tech first getting started, I tried the tee adapter idea and just wondered why any transmitted or receive signals just sounded awful.

Another option would be to use a vehicle adapter where when you get back in the truck, you just take the radio and plop it in the cradle and it turns the portable into a mobile on a NMO mount antenna mounted on the truck. When you need to bail, just pop it out and go.

I would also recommend wavetar's passive antenna suggestion. We use a passive antenna in our ambulances and it works well. Before, portables were useless inside the ambulance but with the passive antenna system they work as if you were outside the truck.

I also recommend Wavetar's passive antennas. Just get a good quality mobile antenna with low loss cable, an extra mount and whip.