wirelees system
- Thread starter avr
- Start date
Larry Fisher unswered this few yearsd ago ( the charmane of lectrosonics , this article from 1999 , but actually nothing changed since)
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I've seen several discussions about VHF vs UHF wireless systems in several
newsgroups. Since at Lectrosonics, we make both types and are happy to sell
either kind, I'd like to make several points. Currently, VHF wireless
operates from 169MHz to 216 MHz and UHF wireless operates from 470 MHz to 806
MHz in the US. The UHF frequencies are 3 times higher than VHF and the UHF
antenna efficiencies are about 10 times higher. The reason for the better
efficiencies are simply that the antenna, the ground that it works against
and the distance from the antenna to an absorptive object (the human body)
all need to be at least a quarter wavelength in distance or length. For VHF
you need a 17 inch antenna with a transmitter case 17 inches long, with the
antenna spaced 17 inches from the body. This is not a practical system. For
UHF, the quarter wavelength dimension is only 5 inches. Since the 5 inch
dimension is much closer to what people want for size and comfort, the
antenna efficiencies on practical systems are much better for UHF. In fact
the radiated power from an UHF system is approximately 10 times better than
for a comparable VHF system. These radiated power ratios are actual
measurements that we have made, both indoors and out. When you add in the
fact that the maximum FCC allowed transmitter power level is 50 milliWatts at
VHF but up to 1 Watt at UHF, then UHF has an even larger advantage in
radiated power. In comparisons between 50 mW VHF transmitters and 100 mW UHF
transmitters, we have ALWAYS found a three to one range advantage in favor of
UHF. We have measured them over hills, around corners, line of sight, on the
front side and back side of the body, inside masonry rooms, and rooms with
metal lathing and also with chicken wire inside stucco. We have NEVER found a
situation where UHF didn't have much more range.
Then why are some users getting results that don't bear this out? One
reason, is that a number of UHF transmitters don't produce the power that is
"quoted" in the spec sheets. The typical user doesn't have an RF power meter
in his toolkit to check this specification and the manufacturer can safely
let it slide by. Also, if you read the spec sheets, there will be various
weasel words that make the specification less than guaranteed. So what
happens, is some people get the same range with a VHF and UHF system since
they may have a VHF transmitter that is producing a true 50 mW and a UHF
system that is producing only 10 mW or less. A second reason can be receivers
that have different sensitivity levels. Some expensive receivers from big
name manufacturers don't even have a gain stage before the first mixer and
have correspondingly poor sensitivity. This of course reduces the range of
the system. A third and obvious reason can be interference on or near the UHF
frequency. With the wide open front ends being put on most UHF receivers,
interference is becoming gradually more probable as DTV begins to use up the
available UHF frequencies.
But back to the main thought of this note: if you are comparing apples to
apples, UHF will have substantially more range than VHF for practical
wireless systems under any real world situations
Larry Fisher
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I've seen several discussions about VHF vs UHF wireless systems in several
newsgroups. Since at Lectrosonics, we make both types and are happy to sell
either kind, I'd like to make several points. Currently, VHF wireless
operates from 169MHz to 216 MHz and UHF wireless operates from 470 MHz to 806
MHz in the US. The UHF frequencies are 3 times higher than VHF and the UHF
antenna efficiencies are about 10 times higher. The reason for the better
efficiencies are simply that the antenna, the ground that it works against
and the distance from the antenna to an absorptive object (the human body)
all need to be at least a quarter wavelength in distance or length. For VHF
you need a 17 inch antenna with a transmitter case 17 inches long, with the
antenna spaced 17 inches from the body. This is not a practical system. For
UHF, the quarter wavelength dimension is only 5 inches. Since the 5 inch
dimension is much closer to what people want for size and comfort, the
antenna efficiencies on practical systems are much better for UHF. In fact
the radiated power from an UHF system is approximately 10 times better than
for a comparable VHF system. These radiated power ratios are actual
measurements that we have made, both indoors and out. When you add in the
fact that the maximum FCC allowed transmitter power level is 50 milliWatts at
VHF but up to 1 Watt at UHF, then UHF has an even larger advantage in
radiated power. In comparisons between 50 mW VHF transmitters and 100 mW UHF
transmitters, we have ALWAYS found a three to one range advantage in favor of
UHF. We have measured them over hills, around corners, line of sight, on the
front side and back side of the body, inside masonry rooms, and rooms with
metal lathing and also with chicken wire inside stucco. We have NEVER found a
situation where UHF didn't have much more range.
Then why are some users getting results that don't bear this out? One
reason, is that a number of UHF transmitters don't produce the power that is
"quoted" in the spec sheets. The typical user doesn't have an RF power meter
in his toolkit to check this specification and the manufacturer can safely
let it slide by. Also, if you read the spec sheets, there will be various
weasel words that make the specification less than guaranteed. So what
happens, is some people get the same range with a VHF and UHF system since
they may have a VHF transmitter that is producing a true 50 mW and a UHF
system that is producing only 10 mW or less. A second reason can be receivers
that have different sensitivity levels. Some expensive receivers from big
name manufacturers don't even have a gain stage before the first mixer and
have correspondingly poor sensitivity. This of course reduces the range of
the system. A third and obvious reason can be interference on or near the UHF
frequency. With the wide open front ends being put on most UHF receivers,
interference is becoming gradually more probable as DTV begins to use up the
available UHF frequencies.
But back to the main thought of this note: if you are comparing apples to
apples, UHF will have substantially more range than VHF for practical
wireless systems under any real world situations
Larry Fisher
MattinSTL
Sound Modulator
I had two Lectro VHF sets... both CR187's... and I sold one of 'em planning to replace it with either a Sennheiser G2 or one of Lectro's higher-end UHF sets.
I sold it for the reasons stated above in Oleg's post. Why didn't I sell the other set? Because on 9.5 out of 10 occasions I get almost perfect sound under any circumstances. I read about dropouts, pops, and poor sound quality that some people get with their wireless. When my video buddies hear my Lectro (VHF) they think it sounds as good as the boom. I shot some video of a martial arts exhibition with a Sensei explaining the action... this was at the Japanese festival at Shaw's Garden... huge place in Saint Louis... anyway, the garden supplied a wireless set and PA system for these guys to use... I watched them play with it and all you could hear was static and non-stop dropouts. Just before the action started I ran down to the Sensei and PA table and asked if they'd like to use my wireless set. The PA guy says, "We got a wireless...", like I'm some jerk with a toy... so I say, "trust me", and he takes my wireless and plugs the receiver into the PA and I run the tiny body pack out to the Sensei... complete with Tram...
Umm, yeaaaah... NO comparison... I looked at the PA guy and he just smiled at me.
I'd definitely suggest UHF over VHF... but you still gotta' spend some cash. I'd like to think that the Sennheiser G2 is as good a system as a Lectro VHF... but I really don't know. I think it depends on the circumstances as stated in Oleg's post. A VHF system is an "all your eggs in one basket" gamble... so in that sense it's stupid to do it... but if there's an RF hole with no competition at that frequency it's still possible to get good results.
If you have $500 to spend on a wireless I'd probably get a G2. If you can come up with a grand or so I'd look at a used Lectro 200 series... and it will take a while to find a good deal.
I sold it for the reasons stated above in Oleg's post. Why didn't I sell the other set? Because on 9.5 out of 10 occasions I get almost perfect sound under any circumstances. I read about dropouts, pops, and poor sound quality that some people get with their wireless. When my video buddies hear my Lectro (VHF) they think it sounds as good as the boom. I shot some video of a martial arts exhibition with a Sensei explaining the action... this was at the Japanese festival at Shaw's Garden... huge place in Saint Louis... anyway, the garden supplied a wireless set and PA system for these guys to use... I watched them play with it and all you could hear was static and non-stop dropouts. Just before the action started I ran down to the Sensei and PA table and asked if they'd like to use my wireless set. The PA guy says, "We got a wireless...", like I'm some jerk with a toy... so I say, "trust me", and he takes my wireless and plugs the receiver into the PA and I run the tiny body pack out to the Sensei... complete with Tram...
Umm, yeaaaah... NO comparison... I looked at the PA guy and he just smiled at me.
I'd definitely suggest UHF over VHF... but you still gotta' spend some cash. I'd like to think that the Sennheiser G2 is as good a system as a Lectro VHF... but I really don't know. I think it depends on the circumstances as stated in Oleg's post. A VHF system is an "all your eggs in one basket" gamble... so in that sense it's stupid to do it... but if there's an RF hole with no competition at that frequency it's still possible to get good results.
If you have $500 to spend on a wireless I'd probably get a G2. If you can come up with a grand or so I'd look at a used Lectro 200 series... and it will take a while to find a good deal.
audio limited is no better system in any way then the 400 i had them( 2000.2020 and sold them without any regret
, the zaxcom is something completely different and has some +++ mostly for boom operating and stereo sending to the camera ,
but for 90% of the time the lectros are more easy and reliable all around systems
currently running 2 211 and 4 411 + 2 zaxcoms st
and if we incl service of these 2 and customer support ( look i live in the deep sheet hole of the universe and not in New Jersey or Rio Rancho) they miles better then the audio or senheiser which only half way from here
about where 2 buy . the maim rull is from some one who respect you as a customer and willing to give you support one minut after he clears your check.
, the zaxcom is something completely different and has some +++ mostly for boom operating and stereo sending to the camera ,
but for 90% of the time the lectros are more easy and reliable all around systems
currently running 2 211 and 4 411 + 2 zaxcoms st
and if we incl service of these 2 and customer support ( look i live in the deep sheet hole of the universe and not in New Jersey or Rio Rancho) they miles better then the audio or senheiser which only half way from here
about where 2 buy . the maim rull is from some one who respect you as a customer and willing to give you support one minut after he clears your check.
no ,i meant the resellers since some times you need their support if you have trouble with your gear.
.
about the lectro from self experience after 7 years and about 15 different systems i had and have now i can admit that this is one of the best companies to get support from
.
they dont afraid to deal even with nut cake like me from 0-10 i give them 9.5 for relations with their customers
.
about the lectro from self experience after 7 years and about 15 different systems i had and have now i can admit that this is one of the best companies to get support from
.
they dont afraid to deal even with nut cake like me
from 0-10 i give them 9.5 for relations with their customers