UHF gurus - 3/4/5W power difference affecting range?
Submitted: Sunday, Feb 20, 2011 at 23:59
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ben_gv3
Hiya radio gurus,
I have a question about the effective range from 3, 4 & 5W UHF radios. With all other things being equal - time of day, elevation/obstructions, antenna size/position etc how much extra range will a 4W UHF have over a 3W and then a 5W over a 4W?
I understand range is not a linear relationship with output power but I'm sure there is some formula to work it out.
Thanks.
Reply By: Battery Value Pty Ltd - Monday, Feb 21, 2011 at 10:13
Monday, Feb 21, 2011 at 10:13
Hello ben_gv3,
hope you don't mind an answer from your battery guru ;)
The distance gain factor in your examples is sqrt(4/3), or sqrt(5/4) equals 1.15 and 1.12 respectively.
Using logarithmic terms (allows you to compare distance gain with antenna gain), 10*(log(4/3)), or 10*(log(5/4)) equals 1.25dB and 0.97dB.
In other words, by using an antenna with 1.25 or 0.97dB higher gain than the existing one, you achieve the same outcome as an increase of power from 3 to 4, or 4 to 5W.
But note that either way, the increase in range is only 15 or 12%.
Hope this helps.
cheers, Peter
AnswerID:
446145
Follow Up By: ben_gv3 - Monday, Feb 21, 2011 at 11:03
Monday, Feb 21, 2011 at 11:03
Oohhh maths.
Great thanks for the info Peter. It was very helpful.
FYI I am looking at a handheld UHF hooked up to an external rook rack-mounted antenna. The UHF I am looking at is a combined UHF (4W)/VHF (5W) unit so was wondering what the difference in range is between a 4W and 5W (other brand unit).
FollowupID:
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Follow Up By: olcoolone - Monday, Feb 21, 2011 at 12:28
Monday, Feb 21, 2011 at 12:28
Can you put it in basic terms as 99.9% of people like myself using them don't care about formulas or don't understand them.
It's good that we have someone on here with full on engineering skills who can rattle these formulas of the top of there head but what does it all mean if I can't understand it.
But it does make you look good!
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Reply By: Member - Graham H (QLD) - Monday, Feb 21, 2011 at 10:24
Monday, Feb 21, 2011 at 10:24
The biggest difference is the terrain you are in.
On some roads you can hear radios for a long long way On others barely around the next corner..
Most fixed UHF are 5w so put one in and be happy.
Get zapped by the latest solar flare and you wont have to worry LOL
AnswerID:
446146
Reply By: Member - Alastair D (NSW) - Monday, Feb 21, 2011 at 14:10
Monday, Feb 21, 2011 at 14:10
Ben,
UHF radios should not be considered as anything other than short range devices. As others have said there are many factors that effect the range and they are changing all the time.
As Graham has said you are best to get a 5w unit and just accept that the range will vary.
If you are wanting a device with good range for safety reasons then you need to consider a sat phone or HF. Regardless I think anyone who goes into remote areas should always carry an EPIRB or similar. They are quite cheap now and equate in cost to a couple of tanks of fuel. Cheap for the security in the event of soemthing bad happening.
cheers
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Follow Up By: ben_gv3 - Monday, Feb 21, 2011 at 16:05
Monday, Feb 21, 2011 at 16:05
Hi Alastair,
I am very
well aware of the overall shortcomings of UHFs and do own an EPRIB so do know about their use. I am also very aware of the properties/characterisitcs of the different frequency ranges.
My initial question was purely on UHFs, nothing more and nothing less.
FollowupID:
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Follow Up By: Member - Graham H (QLD) - Monday, Feb 21, 2011 at 17:36
Monday, Feb 21, 2011 at 17:36
You probably get more variation from a different aerial than anything.
I just stuck a 4014K on and it went whenever I wanted it to.
FollowupID:
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Reply By: olcoolone - Monday, Feb 21, 2011 at 18:10
Monday, Feb 21, 2011 at 18:10
Just some useless
information we used 2 GME TX6200 handhelds and got 93 kilometres as the crow flys with good voice and signal quality.
That was with the standard antenna on high power, we tried low power and still made contact but not as strong.
AnswerID:
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Reply By: Member - Alastair D (NSW) - Tuesday, Feb 22, 2011 at 10:38
Tuesday, Feb 22, 2011 at 10:38
*********************
Hi Alastair,
I am very
well aware of the overall shortcomings of UHFs and do own an EPRIB so do know about their use. I am also very aware of the properties/characterisitcs of the different frequency ranges.
My initial question was purely on UHFs, nothing more and nothing less.
********************
Ben
My apologies if my
well intended response upset you. I realise I went beyond your original question and made an assumption.
I think I am getting close to remaining silent on this site as I either cop abuse or upset people for reasons I don't understand.
regards
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