Hi band or low band wisicom

[chrisyking]

So I bought four channels of the higher band 566 to 790 wisycoms. Just out of interest how much extra range do you get if you use lower radio frequencies i.e. if I had bought the lower range 470-700 band? Effectively how much further would a radio mic on 470 be than one on 790? Anyone know the maths of this?

 

Also are there any other advantages of choosing a particular band? 

 

I'm having my usual post purchase regret.

 

Chris

[Nate C]

Don't regret, Enjoy. Learn and push the limitations of your new toys.

 

The frequency bands in which we operate don't make a significant difference in range in ideal conditions. Where it is more important is in relation to interfering frequencies in your shooting locale. 

[maxpolo]

Free space propagation states: Lfs = 32.45 + 20Log10(dkm) +20Log10(fMHz)

Normally your range is actually dominated by diversity (true diversity gives a big advantage in environment with a lot of reflection), noise on your frequency (remember that every time u can lower your squelch of 3dB is like doubling the power of your Tx), antenna positioning!

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[chrisyking]

Hey Massimo. Thanks for the equation!! Not sure what each variable is but if I went from say 400MHz to 800MHz, what would be the difference in range? percentage wise? or is that difficult to work out?

 

Do work for Wisycom? If do you mind me asking a few questions about the receivers I bought? I don't want to hassle you outside work!!

[maxpolo]

We all work in this audio business for passion u do not bother me.

But my people in support@wisycom.com certainly can help u in a more effective way, especially if a

The am formula is a simple correlation between link budget and distance/frequency.

But it is not true in real application u never get double coverage with half frequency.

U may have some dB advantage on signal levels, but with a good antenna positioning or good frequency/squelch setup u improve 10/20 dB.

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[LarryF]

Not to hijack Massimo's correct description but to make the physics easier to understand, consider this simplification: The reason lower frequencies "propagate" farther, is that the antennas become larger as you go down in frequency. Therefore, the lower frequency antennas are covering more area at any given distance. Hence, they intercept more of the original energy radiated in all directions from the transmitter. It's not that lower frequencies get absorbed less: It is that you can intercept more of the original signal with the necessarily larger receiver antenna. The larger antenna covers more of the sphere that the transmitter radiates into, therefore you pick up a larger fraction of the power from the transmitter.

 

Here's an interesting question: if you had equal sized antennas at a given distance and compared high and low frequencies would the range be equal? The answer is simply yes. The problem is that you can't make a 1/4 wavelength antenna twice as large. It becomes a half wavelength antenna, which is different animal entirely. So, for a given antenna type (typically 1/4 wave antenna), twice the frequency will be half the intercepted area or half the range. Once you get into fancier antennas such as LPDA's or Yagi's, for the same physical size antenna at the higher frequencies, you can use more elements helping to off set the frequency-range trade offs. 

 

Why isn't this decrease in high frequency range more apparent to the typical wireless user? You must also consider that the smaller receiver antennas at the higher frequencies intercept less interference as well as less of the desired signal. The hit to performance, also pointed out by Massimo, is therefore not as great as you would calculate.

Best Regards,

Larry Fisher

Lectrosonics

[studiomprd]

CK: " how much extra range do you get "

1.367 m

 

you must let go and quit shopping, now that you have made your purchase...

 

MP: " true diversity "

compared with..?  false diversity..?  un-true diversity..?

sorry,  there are lots of different diversity systems, and they are all real, and true...  you know better.

 

CK: " Do work for Wisycom?  "

Max is WISYCOM...

(all your research and you missed that..?)

 

" but if I went from say 400MHz to 800MHz, what would be the difference in range?"

6.845m

" percentage wise? " 

.4638%

 

" or is that difficult to work out? "

not for a computer, but,  make that a big BUT  there are so many other variables, and they are probably more significant  --as both Mas and Lar pointed out.

 

so, CK, you still have a lot of learning to do, and I suggest you start with the wireless guides several of the manufacturers (including Lectrosonics) have made available;  much of the information is brand and model agnostic.

 

CK, you made your selection for a number of reasons, including a notable special pricing offer. smile, relax, and stop reliving it.

Edited November 30, 2014 by studiomprd

[chrisyking]

Hi Senator. You're fab. Thanks for putting me at ease. I love this forum. Wish I'd found it sooner.

 

Max I didn't realise you WERE Wisycom!! Wow!! Nice to talk/type to you! I had some questions about firmware, so I'll email Raycom. Won't bother you with it.

 

Chris