[HamWAN PSDR] 902 MHz Band Plan? Hardware?
me at bartk.us
Fri Nov 21 15:59:35 PST 2014
Are you sure a Mikrotik host board won't just run a 902MHz card like the
XR9? If it's possible, that'd allow us to keep the same software stack
we have right now, keep TDMA, and provide the MIMO we're seeking. The
other thing I'm curious about is the frequency agility of the XR9. Does
it support 2.5MHz/5MHz channels? What are the quantization steps on its
tuning ability? What is its tuning range? Are there other 902MHz
miniPCI(-e) cards on the market?
I'd still like to see sectorization since it's hard to scale otherwise.
The band is 26MHz wide, which is enough for 5MHz sectorization. Perhaps
the sectorized spectrum can be arranged to avoid the most
likely/frequent users of this band, but I don't think you're gonna have
any luck by trying to comply 100%.
If someone has any suggestions about other technologies, such as CDMA
spectrum sharing, I'd like to hear them. One of the things to keep in
mind about 902MHz HamWAN service is that it's aimed squarely at mobile
users. Can't assume high gain directional antennas at the user
terminal. I'd like to support things like whips on car rooftops with
near-continuous coverage as the car drives around.
As some of you are aware, I'm not satisfied with the available power
levels for any of this equipment. Mobile stations will be behind
buildings and trees, at close to ground level. I'd like to bring things
up +20dB or so over stock (ie: 50W range). If you know of any
affordable 902MHz amplifiers that can be used with these radios, let me
know. The requirements are RF-sensed TX triggering from signals as low
as 100mW or so, bidirectional signal handling, about a 1us TX/RX delay
time, and linear amplification since these modems use amplitude
components to carry data. Running off a standard 12V car power system
would be a bonus. The combination of reduced frequency and increased
power ought to drive a far more available service than we have with the
6GHz offering right now. However, experiments can begin right now with
just stock power levels to get a better feel for propagation properties
and noise levels of this band.
On 11/21/2014 10:34 AM, Ryan Elliott Turner wrote:
> Hey folks,
> I'd love to get rolling on testing some 900 MHz gear here in Memphis.
> I've got a few high-level questions about it, though, and I'd love to
> find out what others have already settled.
> Do we want to do sectors and multiple channels? UBNT sells a AM-9M13
> that looks pretty slick; 120 degrees, 2x2 mimo; spec sheet here:
> Mikrotik sells a metal 9hpn that's 27 dBm @ 11Mbps to 24dBm @ 54 Mbps
> (500 mW transmitter), but that's single chain. From what I read, dual
> chain MIMO mitigates about 3dBm of noise, which may be worthwhile.
> These devices don't play nice between vendors, though, and I think the
> preferred dual chain 900 mhz device is the UBNT XR9. We'd lose TDMA by
> going with this but gain another chain. Thoughts?
> Apparently the ARRL band plan is pretty outdated and unrecognized
> (http://www.aracc.org/33cm900mhz.pdf ). Around here, we have an
> organization named SERA that has specified a 900 MHz band plan; it is
> available at the following URL:
> So, here we've got
> * 922<=f<928
> * 910<=f<916 (it says ATV...)
> And that's it. So, if we were to sectorize, we don't even have 3
> channels to use here.
> Thoughts? Looks to me like omni, TDMA, and single 5 MHz channel
> (911-916?) is the best way to go for this.
> Ryan Turner
> PSDR mailing list
> PSDR at hamwan.org
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the PSDR