UHF vs VHF

[rfdadams]

What is a good way to describe UHF vs VHF when discussing Fire Department Radio? Trying to get fireman to understand the difference between the two. Just need to dumb it down for my guys.

 

[zz0468]

The spelling? The length of the antenna? What are you looking for here? You're question is pretty vague.

 

[davidgcet]

UHF is Ultra high freq, VHF is Very High freq. the 2 are not compatible, as Ultra is way higher than Very. if they require more info than that, tell them to buy a study guide and brush up. there is no real reason they as users need to know specifics of propagation just to mash a button and talk.

 

[IowaGuy1603]

UHF is most likely going to be used in an urban area whereas VHF is going to be more useful in a rural area.......................

 

[texasemt13]

What is a good way to describe UHF vs VHF when discussing Fire Department Radio? Trying to get fireman to understand the difference between the two. Just need to dumb it down for my guys.

Don't take this the wrong way, but you imply that you yourself understand the difference and yet you yourself can't dumb it down for your guys?

The basics:

VHF= 30 - 300MHz, or a wavelength between 10m and 1m. Propagates well through rural terrain and works best with line of sight to the other operator (HT and repeater).

UHF= 300- 3000MHz (3GHz), or a wavelength between 1m and 0.1m. Propagates ok through a rural terrain and better (than VHF) through an urban terrain. Works best with line of sight to the other operator.

The two terms are just letter designations for a band of frequencies (VHF band is 270MHz wide and UHF is 2700MHz wide).

 

[W2NJS]

Use a large piece of white display board. On it draw a heavy black horizontal line. Somewhere on the left end of the line make a green "X" and label it "Radio Broadcast." Then farther to the right do the same thing and mark it "FM Broadcast." Continue with as many discrete areas as you think are needed, maybe showing the ham band as being just below the public service VHF band, then a wide space until you get to what you mark as the "UHF Public Service" band. You get the idea. Graphics are a wonderful teaching tool if done correctly.

 

[DickH]

What is a good way to describe UHF vs VHF when discussing Fire Department Radio? Trying to get fireman to understand the difference between the two. Just need to dumb it down for my guys.

I would tell them they use different bands of frequencies - just like AM radio and FM radio use different bands of frequencies.

 

[CrabbyMilton]

You can tell them that they are just different frequencys. If they still don't understand, tell them that GOOGLE is their friend on such things.

 

[hockeyshrink]

What is a good way to describe UHF vs VHF when discussing Fire Department Radio? Trying to get fireman to understand the difference between the two. Just need to dumb it down for my guys.

What is the problem you are trying to solve? What is the instructional objective? Why do firefighters need to know the difference between VHF and UHF? Is it just understanding, or is there an operational need to distinguish between the two systems (e.g., do they use VHF radios on the rigs and UHF for fireground/tactical?)?

What BEHAVIOR must change as a result of your training?

You don't need to "dumb down" anything, but you do need to be very clear about what the objective of the training is and design an appropriate instructional method to deliver it.

 

[zerg901]

How about - UHF is "Ultra High Frequency" - VHF stands for "Very High Frequency" - we are talking about how fast the radio wave "vibrates" - on your car radio, an AM station might be at 650 kiloHertz - that radio wave vibrates at 650,000 times per second - a FM radio station, such as FM 108 is at 108 Mhz - which means that the radio wave vibrates at 108 million times per second - kinda blows your mind if you think about it too hard.

Otherwise, maybe all the FD guys need to know is that a UHF radio cannot talk directly to a VHf radio or a 800 radio. A patch system of some sort would be needed. It is like putting gas in a diesel engine - it dont work. Like putting Chevy parts on a Ford. Dont work. (Or does it - I have no clue). Like putting mayo on a donut. I'll stop now.

 

[rfradioconsult]

For simplicy VHF normally refers to frequencies in the 150-174 MHz range, UHF refers to frequencies in the 450-512 MHz range, another common term is low-band these usually denotes frequencies in the 30-50 MHz range.

 

[lbfd09]

I would break it down further...

VHF Low Band -- ~30mHz to ~100mHz (FM radio) - Covers Vast Tremain with hills and forests (density not withstanding). This band is less susceptible to dropping out and can travel farther.

VHF High Band -- ~100mHz to ~300mHz - More susceptible to dropping off and will not have the range per transmitter wattage. Will have a little penetration into building and structures.

UHF Low Band -- ~400mHz to 700mHz - Need for more repeaters and distance per watt is less but you have better building penetration.

700mHz -- Even less kick per watt and better yet on penetration into building.

800mHz -- Even more extreme than 700...

900mHz -- Still greater need to use in a repeater environment, but is very usable with generally decent range to well placed and designed repeaters. Great penetration into a structure.

1.2gHz -- Excellent penetration but sucks when comparing use on a repeater system. The range is dramatic from 900 to 1.2.

This is a general satatement and there are exceptions but the higher the frequency the less range and greater the need for repeaters. Also the higher the frequency the better the signal will penetrate into a building (Here again building construction will nich this as well).

This should give you another way to describe some of the characteristics of the various bands and little insight on why and how they are used. If your firefighters ask for more, they are ready for their ham ticket.

 

[DickH]

I would break it down further...

VHF Low Band -- ~30mHz to ~100mHz (FM radio) - Covers Vast Tremain with hills and forests (density not withstanding). This band is less susceptible to dropping out and can travel farther.

VHF High Band -- ~100mHz to ~300mHz - More susceptible to dropping off and will not have the range per transmitter wattage. Will have a little penetration into building and structures.

UHF Low Band -- ~400mHz to 700mHz - Need for more repeaters and distance per watt is less but you have better building penetration.

700mHz -- Even less kick per watt and better yet on penetration into building.

800mHz -- Even more extreme than 700...

900mHz -- Still greater need to use in a repeater environment, but is very usable with generally decent range to well placed and designed repeaters. Great penetration into a structure.

1.2gHz -- Excellent penetration but sucks when comparing use on a repeater system. The range is dramatic from 900 to 1.2.

This is a general satatement and there are exceptions but the higher the frequency the less range and greater the need for repeaters. Also the higher the frequency the better the signal will penetrate into a building (Here again building construction will nich this as well).

This should give you another way to describe some of the characteristics of the various bands and little insight on why and how they are used. If your firefighters ask for more, they are ready for their ham ticket.

He is asking for a way to apply the KISS principle - Keep It Simple, Stupid. Your explanation is so far from simple that even some so-called Hams (tech. license) won't understand it.

 

[joetnymedic]

ok uhf better building penetration but only travels short distance. vhf sucks at building penetration (actually it weakens the signal) but pretty good for distance

 

[majoco]

I'm with Joe on this - UHF is much better then VHF for building penetration, although I'm not overly sure that the distance achieved is any different. In a fire rescue situation, I guess the building penetration factor is of greater importance.

 

[zz0468]

...uhf better building penetration but only travels short distance...

Free space loss is slightly higher at UHF, but as far as traveling only short distance, this is FAR from reality.

 

[lbfd09]

He is asking for a way to apply the KISS principle - Keep It Simple, Stupid. Your explanation is so far from simple that even some so-called Hams (tech. license) won't understand it.

Well Dick, I might have gone a little overboard in my outline, but this is actually less technical using a more physics type of approach. But as a 40+ year member of the fireservice, I have learned that most in the service are more interested in the how come this and not that approach in answering the question.

I know my guys understood instantly when I have given the above explanation -- I guess they are ready to take their advance ticket exam?

 

[rfdadams]

DickH thanks for the info, it made sense and I have a better understanding.

 

[n5ims]

What is a good way to describe UHF vs VHF when discussing Fire Department Radio? Trying to get fireman to understand the difference between the two. Just need to dumb it down for my guys.

You can simply say that they are two different types of radio that can't normally talk to eachother. For a visual, grab two of your department handhelds and a pair of cheap FRS radios. Show that the two department radios will easily talk to eachother and that the two FRS radios can talk to eachother, but that the department radio will not talk to the FRS radio, nor will the FRS radio talk to the department radio.

When they ask "Why?" simply say "That's the way it works, kind of like you put out fires with water, not gasoline." When they ask "Why do some folks use one and others use the other?" you can first say "There aren't many VHF channels available so folks had to get UHF channels. Now most of the UHF channels are used up so folks are now getting 700/800 band frequencies." If they want more of an answer than that you can use the info from the post that shows each band and what it's good for.

 

[DickH]

... But as a 40+ year member of the fireservice, I have learned that most in the service are more interested in the how come this and not that approach in answering the question.

I know my guys understood instantly when I have given the above explanation -- I guess they are ready to take their advance ticket exam?

Well, I began my fire service career in 1955 on the east coast and some of them barely knew enough to push the mic button. East coast and left coast were/are? like night and day in some matters.