Digital communications


Griff Hamlin <griff@...>
 

Hi Fellow CMRA members,

Michael Hauan's recent email mentioned kb9mwr's blog about the use of 2.4ghz HSMM radios in Texas for emergency communications. kb9mwr recently told me about a Singapore manufacturer, Doodle Labs, who is making a 1 watt high data-rate transceiver that operates on 70cm with a signal bandwidth of 5mhz and sells for about $130. See http://http://doodlelabs.com/products-and-services/militaryfederal-bands/410-470-mhz-dl440/111-420-450-mhz-embedded-ofdm-transceiver-dl435-30.html for more info. kb9mwr has advocated using these radios on the little used 5mhz ATV channels at the low end of the 70cm band (see http://http://kb9mwr.blogspot.com/2009/01/70-cm-hsmm.html). The range on 70cm should be better than on 2.4ghz.

A canadian company, XAGYL, was going to import these radios for resale, but the deal evidently didn't work out. kb9mwr told me:

their (Doodle Labs) business model is to work with OEMs. Doodle Labs is not
set up to address small quantity purchases. Doodle Labs has
approached a few resellers to see if they can do this. But they want
to see the demand first before they carry the product. So this is like
a chicken and an egg situation.
I'd like to see a group like TAPR to consider buying a small lot of
these. If you know anyone who might be interested in being a reseller
that would help things.

Steve, KB9MWR

Are there some CMRA members who would like to experiment with high data-rates on 70cm if TAPR or some other group does obtain some of these radios? If so, Is there anything we can do to help TAPR or some other ham organization to get some of these radios?

Griff W5VWP


Don - KM0R <km0r@...>
 

I'd like to play around with some of the networking if we can find
reasonably priced equipment.

I've been looking at some HSMM stuff lately too and found this site
interesting. http://hsmm-mesh.org/

Don M. - KM0R


Griff Hamlin <griff@...>
 

Hi Don,

I found the HSMM MESH site not long ago. THey use WRT54G (Linksys) radios. I've used WRT54G
radios in the past, but I've had better luck with the newer Ubiquity radios. The WRT54G has about
a 50mw to 100mw transmitter. The Ubiquity has 800mw transmitter and costs $82. Also the
Ubiquity units are capable of reducing the signal bandwidth from the 802.11 standard 20mhz down
to 5mhz. This reduces the data-rate to 1/4 of normal, but it should give more range. I haven't
personally tested this since no one to talk to in Columbia. I've read websites that talk about loading a version
of the MESH firmware into the Ubiquity products, but I haven't tried it yet. I'm still trying to see
how far I can go on one hop. Some websites say that mesh networks don't work too well with
more than about 2 "hops". Have you read this? I know each hop halves the data-rate.
In years past I have setup 802.11 "repeaters" using a pair of 802.11 radios connected to each
other via ethernet, mounted on the same pole, and connected to antennas pointing in different
directions. One radio was setup as an "access point" and the other as a "slave". No special
firmware was needed. I haven't tried this on my newer Ubiquity gear, however.

Michael Hauan and I are probably going to purchase one lot of three 24DB-gain parabolic antennas
from ebay.com. Total cost is likely to be about $90. That's $30 per antenna. Would you be interested
in buying the extra antenna? Normally such antennas cost about $60 plus shipping.
I'm 8 miles from Michael who lives in Millersburg. We might try to establish an 8-mile link, but I
suspect we won't be able to mount the antennas high enough to maintain line-of-sight.
Do you have access to any tower or high-spot in the north or east part of columbia, within
about 5 to 8 miles from me? I live in NorthEast columbia. You can put my address into
maps.google.com to see how far away.

Griff
W5VWP
5980 E Sing Dr
Columbia, MO 65202

On 10/10/2011 07:44 AM, Don - KM0R wrote:
I'd like to play around with some of the networking if we can find
reasonably priced equipment.

I've been looking at some HSMM stuff lately too and found this site
interesting. http://hsmm-mesh.org/

Don M. - KM0R



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