[MLB-WIRELESS] New Lightpointe product
mw at freenet.net.au
mw at freenet.net.au
Wed Aug 5 19:41:09 AEST 2015
Yeah, bugger – that’ll kill it! :-D
I looked at the detail, and there’s actually a peak for oxygen absorbtion smack on 60GHz – that’s why they open that band up for class license no doubt ;)
It looks like it is ‘only’ about 11dB though, but that’s still easily enough to put a dampner on that idea ;)
(good article about all that here: https://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet70/oet70a.pdf)
Nonetheless, It’s still an interesting alternative to 24GHz :)
From: Tony Langdon [mailto:vk3jed at vkradio.com]
Sent: Wednesday, 5 August 2015 7:25 PM
To: mw at freenet.net.au
Cc: melbwireless-bounces at lists.wireless.org.au
Subject: Re: [MLB-WIRELESS] New Lightpointe product
On 5/08/2015 7:18 PM, mw at freenet.net.au <mailto:mw at freenet.net.au> wrote:
I thought so too until I took a look at the LIPD docs:
Data communications transmitters used outdoors
1. Transmitters are limited to land and maritime deployments.
2. Maximum transmitter power must be 20 mW or less.
3. Spurious emissions outside the band must be less than ‑30dBm/MHz.
4. For outdoor use only.
According to this detail, max EIRP is 52dBm which means that 8 dBm max tx capability with 47dBi antenna still comes in under the regulatory limits.
According to free space attenuation calculator (here http://www.radio-electronics.com/info/propagation/path-loss/free-space-formula-equation.php) 60GHz over 10km is only 146dB, so if that lightpointe gear can run at full 55dBm EIRP, then result at the receiver (assume 47dBi antenna) will be up to around -47 which will surely be sufficient for a decent link :)
Tell you what, though, 0.6 degree antenna beam will make it damn tricky to align, and to KEEP aligned when there is a lot of heat fluctuation in the air ;)
But even with the 44dBi antenna, it only adds 18dB to the calculations, and -65 over 10km is still pretty good….
Did you include the additional 16dB/km of Oxygen absorption loss? That's on top of normal 1/R^2 free space losses. So, there's 160dB of absorption loss from oxygen in the atmosphere over a 10k path. Hmm, 300dB path loss, that's worse than VHF moonbounce (~270dB)! :)
73 de Tony VK3JED/VK3IRL
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