Site Communications Difficulties

[wb4bsd]

I need a temporary and cost effective solution for my workplace comms problems.

We currently operate on VHF 140 Mhz (thats right, i am military). All comms are secure and are simplex. But i cant talk from one end of the place to the next with out getting dispatch to relay. As many of you know, if you have to get dispatch to relay every little thing it becomes a pain in the butt.

I have looked at some BDA'a but dont really know if this would work or not.

Any suggestions would be wonderful. Thanks guys and ladies.

[Jim202]

[quote="wb4bsd"]I need a temporary and cost effective solution for my workplace comms problems.

We currently operate on VHF 140 Mhz (thats right, i am military). All comms are secure and are simplex. But i cant talk from one end of the place to the next with out getting dispatch to relay. As many of you know, if you have to get dispatch to relay every little thing it becomes a pain in the butt.

I have looked at some BDA'a but dont really know if this would work or not.

Any suggestions would be wonderful. Thanks guys and ladies.[/quote]


You haven't given us much to work with. You did mention your radio coms are simplex and secure. The type of equipment may or may not come into play here. Some of the older secure radio modulation kind of stinks. The newer radios have a good secure system that doesn't cut down the range. Is there any chance of getting authorization for a repeater? That would solve the whole problem.

Next question is you didn't state what kind of units were having the com problem. Are you using protable or mobiles? Hope you don't have the short stubby antennas. Putting on the long antennas on the portables will make a big difference.

The use of bidirectional amps only works if you have a well designed system with isolation between the doner and user antennas. Inside a building to the outside world is a prime use of a BDA.

Jim

[wb4bsd]

Jim, thanks for pointing out my lack of info. I wasnt sure what all i needed to add.

Our current stock is mostly comprised of Sabers, some R some not, but all are older radios. None are astro. We have one dispatch radio that is an analog saber, it is attached to an outside antenna and the hardline is slotted to allow people inside to hear transmissions and to allow dispatch to hear transmissions from portables operating in doors.

the problem i am having is getting two portables to hear each other when there is a little distance between them. This building is 3 stories and is blast proof. also we have an office barge on the river about 200 yrds from the main building and comms between the barge and other portable ht's is very poor. So all comms have to co through dispatch.

Repeater? well, even if we had access to one and we do on an emergency basis, we wouldnt be able to get into it from inside any of the buildings.

in 2008 we, the entire base, is slated to convert to astro p25 uhf trunk. this posses another interesting dilemma as we will probably not be able to get into the trunk either from inside the building. Kinda stinks i know.

anyway, hope thats adds a little light to what i am dealing with. also the secure is DES only, no XL at all. not even capable of using XL as all the older sabers have DES modules only.

thanks

[nmfire10]

Wow, that is creative. A portable with radiax and an antenna at the end.

Lets try this...

1. Can the dispatcher hear everyone?
2. Can everyone hear the dispatcher?

If you answered yes to both of the above questions, unplug the "dispatch saber" and replace it with a Kenwood TKR-750 VHF repeater set for continuous duty (25 watts). Plug in desk mic. Now you have a dispatch radio that is also a repeater complete with in-building and outside coverage. Everyone's portables will need to be reprogramed for repeater operation.

Now, I have no idea how you go about aquiring frequencies or if you can just pick one since your that special . But, like I said, if you answered yes to 1 & 2, that should fix it quite nicely.

[xmo]

"...unplug the "dispatch saber" and replace it with a Kenwood TKR-750 VHF repeater set for continuous duty (25 watts)...."
_________________________________________________________

Well - you learn something every day! I sure didn't know that a Kenmore repeater was compatible with Motorola Securenet.

One issue - if you are currently not using XL encryption - changing to XL could improve your range.

If you did want a REAL Securenet capable repeater, BroCom has been selling VHF low range [132-154] Quantars on ebay for less than 3 grand.

[KG6EAQ]

(thats right, i am military). All comms are secure and are simplex.

I think you answered your own problem. You need to ask the communications powers that be for your unit for some help. An addition of any repeater is going to involve a lot of work and money. You'll also need to get access to the programming software and equipment and reprogram all the portables.

Are you or someone in your unit authorized to make those changes?

[wb4bsd]

its funy XMO, i am about the most junior person there with the most knowledge about radio's. So i guess you could say i am the Commnications Powers that be.

and yes, i purchase many things as far as radio equip goes. the only problem is that the freq's were are given by the region are all taken up. so i cant really play around with that. If there is no way to extend my simplex ops without a repeater i guess i will have to just make do until the trunk comes around. and of course by then i will be long gone and it will be someone elses problem.

[RFdude]

VHF coverage in a concrete bunker is very poor. Wall attenuation is huge, and I'm sure you guys probably used more than ample rebar. The good news is that this type of isolation from the outside is good for a BDA or On-Frequency Repeater gain. There are a few companies that manufacture these units. The Radiax that is in the building might suffice to get the job done as long as it goes through the best isolated parts of the building. You could put a unity gain whip at the bottom (the end opposite the OFR) of that Radiax for even better pickup. You didn't mention the area of the bunker. Radiax has coupling limitations for how far your portable can be from the cable. If the building is big and wide, a distributed antenna system would work better. The isolaton between indoor and outdoor antenna would have to be 15 dB more than your OFR gain to avoid interfering with itself. As poor as VHF is in-building, it propagates very well in the open. So the OFR with an outdoor omni antenna might just get heard by other portables.

An OFR manufacturer can evaluate your needs and provide consultation.

A quick GOOGLE search yields: KAVAL, TX RX Systems, FUTURECOM

[wb4bsd]

just to clear it up, we use a spectra for dipatch, not a saber.

not sure what kind of antenna is attached to the spectra at the other end of the radiax.

I would switch to XL in a heart beat if the module we had supported it.

[nmfire10]

"
Well - you learn something every day! I sure didn't know that a Kenmore repeater was compatible with Motorola Securenet.

Where is the "bang head on wall" smilie??? CRAP. I must have overlooked and/or forgot about that little detail. Scrap that thought. It was a good idea while it lasted damn it!!

Yea, so your screwed.