Summer 2008 Issue

HSMM

HSMM and Field Day – raison d’ętre

By John Champa, K8OCL

Field Day use of HSMM (high-speed multi-media) radio is increasing dramatically to the point where most major club Field Day sites have full intranet radio service among the various stations scattered across the countryside. Often they also have some Internet access to keep family and friends posted on their progress and to communicate vital needs to outside supporters. We will have more on these exciting events in the next issue, but of all the many uses radio amateurs have made of HSMM technology, Field Day is clearly its raison d’ętre (reason for being). When you must move a lot of data very quickly and accurately and there are no wires, HSMM radio techniques are tough to beat.

Although emergency communications applications of HSMM radio are frequently discussed and written about, the fact remains that too few radio amateurs know enough about IP-networked radios to set up such systems in the field and in a hurry. That is changing, but it will take time.

SSID Protocols

The ARRL HSMM Working Group never established an SSID standard for HSMM radio. However, the ARRL Michigan Section DRG (Digital Radio Group) has proposed such a standard. For example, the author’s SSID is k8ocl-2. We encourage the further development and use of this DRG standard.

SSID Purpose

-0 home stations

-1 home-station personal mailboxes

-2 gateways

-3 full-service BBS (those that forward mail and bulletins)

-4 network nodes (having two or more radio ports that perform TCP/IP routing)
-5 console, keyboard, printer, etc.

-6 conference bridges

-7 crossband digipeaters (802.11g and 802.11a, etc.)

-8 crossband digipeaters (other)

-9 mobile, modats, etc,

-10 WL2K

-11 HSMM airborne nodes (balloon, aircraft, etc.)

-12 HSMM satellite (OSCAR) nodes

-13 unassigned

-14 unasssigned

-15 downlink address when exiting the far end of a network

Note: There is now a page for listing your D-Star DD or 802.11 HSMM installations: <http://en.wikipedia.org/wiki/List_of_hsmm_ nodes> (Thanks to KF4YFD for this information.)

Coaxial Cable Feedlines

All present-day HSMM radio experimenting is done at 900 MHz and above, with the majority of it being on the 2.4-GHz band. Thus, please pardon me while I state the obvious: All 1/2-inch coaxial cable is not created equal. Even though the 1/2-inch black cable has quality N-series connectors at each end, this does not make it suitable for HSMM work; RG-213 and RG-214 are prime examples. Here is what I recommend in the way of “1/2-inch” coaxial cables, as they are far more suitable.
 

Cable Type 2.5 GHz Loss 5.8 GHz Loss

(dB/100 ft.) (dB/100 ft.)

LMR400 (good) 6.8 10.8

1/2" Heliax (better) 5.7 10.5

LMR600 (best) 4.45 7.25

When installing coaxial cable for your antenna projects, exercise some care:

1. If you pull coaxial cable too hard, its loss properties may increase.

2. Bends in coaxial cable must not exceed the cable’s spec for bend radius.

3. The longer the run the higher the loss, so keep runs as short as possible.

4. If the antenna is outside, you must provide for lightning protection.

5. Even weather-tight connections should be sealed outside.

The Biggest HSMM Events of the Year!

Every year a team from the HSMM Working Group of the Texas Microwave Society puts together huge HSMM radio networks to service the Wild Ride Against Cancer and the Plano (TX) Balloon Festival. We all can learn much from this team’s experience. The notes and photos that comprise the remainder of this column were supplied by Kipton Moravec, KE5NGX (kip@kdream.com):
 

Click here to return to Summer 2008 highlights

Click here to subscribe to VHF

_________________

© Copyright 2008, CQ Communications, Inc. All rights reserved. This material may not be reproduced or republished, including posting to a website, in part or in whole, by any means, without the express written permission of the publisher, CQ Communications, Inc. Hyperlinks to this page are permitted.