OFDM is a pretty rectangular emission spectrum (unless you're over-driving your amps), so it keeps pretty tightly to its own frequencies. For example: http://www.dsplog.com/db-install/wp-content/uploads/2008/02/ofdm_tx_spectrum... We haven't experienced issues with anyone above 5925 to date. The spectrum up there is for fixed microwave (think: point-to-point dishes) and earth-to-space (think: giant dishes pointed up). Both types of usage are highly directional, so even if there is some spill, it's unlikely to affect anything. I'm reluctant to pro-actively give up already limited spectrum on the off chance that some day we'll co-locate with a licensed transceiver that does use a frequency low down near 5925 and our sideband is strong enough and the antenna gains are correctly directional enough to interfere. We do spectrum surveys of our sites before we install anything, so that we can better predict if there will be issues. Good point though, and it has been considered during initial planning. Aside from emission frequencies, there's also the consideration of directionality (eg: F/B ratio). That's an area that we can use lots of improvement in. I'm not happy with our present performance there. I heard you guys are planning to use UBNT sectors. We might use them too. Just be aware of their very narrow vertical pattern. It means setting proper down-tilt is critical. I really gotta measure them in full 3D, and with WaveGuards. --Bart On 06/25/2014 12:30 PM, Tom Hayward wrote:
On Wed, Jun 25, 2014 at 12:27 PM, Kenneth Tolliver <ktolliver@hotmail.com> wrote:
Shouldn't the 10 MHz Plan be bumped down by 5 MHz(or some other amount) to allow 5MHz as a Guard at the top of the Ham Band Plan? I don't know what is on the other side of 5.925GHz; but I'd assume it could be an issue to us. Has that been discussed before and I just missed it? Maybe just 1 or 2 MHz would be sufficient? The guard bands were sized by testing. 10 MHz was decided on because that was where throughput speeds were good even with 3 sectors colocated.
There aren't going to be nearby transmitters on 5.926 GHz, so we have no reason to bump the guard band down. We might as well use the full ham band.
Tom KD7LXL
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