Batboard

Looking for a few opinions. Here is what we are looking for. Currently in our fire department we use all low band equipment (44.06mhz) what we are looking at doing is upgrading to UHF or VHF portable radios. Channel 1 going back to a truck with a crossband repeater to low band. And channel 2 being a talkaround channel. Repeater would be in our ladder truck, which is onscene of all our incidents. What our toss up about is if we should go with UHF our VHF handhelds. Both band splits are available in our area. We are a suburban area, with a few high-rises in our district. Another reason we are looking at going to this type of set-up is that we are starting to run in a neighboring county that uses 33.80mhz which we have in our 9000s in the truck but of course can’t be put in our portables. Would like to here the pros and cons of both UHF and VHF. Thanks for your time.

I'm no expert on the matter, but I know that UHF penetrates in buildings usually better than VHF Hi or low...

If the setting will be mostly flat, VHF will have a better bang.

And if this ladder truck will be always onscene... the crossband repeater antenna could be setup on the ladder to improve range?

Just some thoughts...

Mike

UHF will get in and out of buildings better than VHF. If this is just an on-scene cross-band unit, you don't need the signal to travel for miles. It just needs to cover on-scene. Most vehicle repeaters are only running anywhere from 1-4 watts on a 1/4 wave antenna... basicly a glorified portable radio...

I have to agree that UHF works better inside buildings from my experience as well.

However id consider compatibility with my other comunications needs as well.

Does the com center if you have one in your area operate on vhf or uhf
ect ???

How about other neigboring law enfoecment agencies that you might need to comunicate with in an emergency situation.

Your local hospital / ambulance freqs= VHF/UHF?????

Not that im steering you away from UHF because if its on scene coms your concerned about and only that then yes by all means go UHF.

But if you need to be able to have comunications with the hospital/ambulance or say a local pd officer or even a state trooper and they operate on say for example VHF then maybe you should go VHF with the repeater option .

Even though UHF penetrates buildings better id say that if you really could use/need the VHF that with an on scene repeater doing 25 watts or even 45 watts at VHF freq that would more than likely do the inside building comunications for you since its basicly on top of your disaster site.

I dont really care to rely on radio for a lifes saftey but in all honesty we do just that and with eigther a VHF or UHF on scene repeater youll probaly win or loose equaly in any situation.

It may even be posible to go with UHF even if the others you need coms with are low band as the way i read your post youd low band in and UHF out (or VHF out????= your decision) and still maintain coms with them as well if they were to program there radios to gain access to your crossband repeater.

If your other agencies are on low band still then id consider asking to see what the general concesus would be as to which band they would upgrade to in the future so that youd be where they would be going to which would leave you compatible with them then as well when they upgrade.

Well there you go my 5 cents worth.

Good Luck

EKLB

The shorter wavelength of UHF allows it to pass through openings better than VHF. It actually propogates in waveguide modes in some instances indoors. 800 and 900 are even more capable of this mode of propogation. Inside elevator shafts, for example. On the other hand, UHF is more readily absorbed by foliage and some types of building materials than VHF. I have also noticed better performance of UHF in canyons here in the dry Southwest. Suspect it reflects off the rock walls better than VHF does. Plant some trees and everything switches around.

Doug

What would be best for dense foliage (Southern Missouri forests)?

The military seems to really love lowband still. I've always wondered if it was able to cut through the damp jungle environments better.

I'm just curious if there would be any advantage to using lowband portbles and backpacks during hiking trips rather than regular vhf or uhf.


mancow

mancow wrote:What would be best for dense foliage (Southern Missouri forests)?

The military seems to really love lowband still. I've always wondered if it was able to cut through the damp jungle environments better.

I'm just curious if there would be any advantage to using lowband portbles and backpacks during hiking trips rather than regular vhf or uhf.


mancow

Will in my tests in Southern Missouri forest, I would say that VHF and UHF work about the same in almost all cases when it comes to portable to portable. In very dense foliage such as in the summer, it would seem that the UHF radios work some what better.

Cam

I bet there's no shortage of trees up there where you're at.


mancow

I understand the qestions point of angle as to foilage and absorbtion.

So im going to answer the qestion and my observations from two stand points.

Yes i have noticed and am aware that UHF freqs do seem to be absorbed by foilage reducing range somewhat.

My experience with it has been that on my FB6 comunity repeaters that during the summer months when foilage is present i do experience about a 4 to 5 mile loss of range but gain it back in the winter months or foilage shy periods ect.

My system im refering to has a normal 30 mile range during the summer and increases to approx 35 miles come winter. (Im refering to a FB6 UHF repeater)

Now from the stand point of this being a consideration for a on site repeater at a disaster site= Probably not a point to take into consideration as again the repeater is at the site and foilage close in wouldnt be much if any of a factor to worry about.

Now im not sure that id care to say that VHF or UHF would be better than the other versus foilage as i cant say that i have enough experience to make a good decision on that angle.

But my gut feeling is that VHF may have a slight edge = but i cant tell you why i feel this to be the case/just that its my gut feeling.

I wouldnt with my pick of eigther VHF or UHF probably even consider the foilage factor as i have used both and had good performance myself in heavy foilage so id lean towards the band in preference for other properties and reasons= but thats only my point of view and feelings/others will have diferent opinions.

EKLB

UHF is generally selected for cross-band links such as you envision, for two reasons: first, UHF tends to do slightly better on going from the street into buildings; I think this has more to do with multipathing than aperture, but the effect is real (if not large); second, UHF portables can use shorter, handier antennas, in situations were a high performance antenna is not required.

Doesn't NFPA currently recommend that firegound comms be simplex? Maybe it came out after 9/11, or perhaps it's been there a while, but my memory tells me that this is what they think is best for this type of work.

Correct: I believe the cite is NFPA 1251. However, UHF "mobile extenders" are commonplace in the rural areas of the NE, where the base channel is low-band.

However, what 1251 is really urging against is (i) use of trunked system talkgroup for fireground and (ii) use of repeaterized channel (conventional repeater) w/o adequate training in use of (A) "direct" button or (B) separately programmed "direct" channel. Theory is that a guy in trouble in the basement would be unable to hit a distant repeater (either conventional or trunked control channel), and would therefore be out of comms with the guys on the street. That is less likely to happen with on-scene extenders.

Our Dept has similar mutual aid problems. Our neighboring county is on Low Band, we are UHF. What I have proposed to be installed in our new Squad truck, is a couple of cross band repeaters. We are figuring one for fireground ops the other for water handling (we are rurual and have to bring our own water) a third is planned for crossband use with the state police and locals.