[HamWAN PSDR] Switching to the 10MHz frequency plan

[Bart Kus]

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.png

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 at 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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