Technology: 900 MHz Ham Trunking?

902-928 Amateur Trunking, what's the story?

With all the current discussion on technology, I have been doing quite a bit of searching & reading of info on 802.11-900MHz, 2.4 & 5 GHz data stuff. One thing I came across is a web article called Amateur Trunking (http://www.clarc.org/~kc5vlz/trunking.html) by KC5VLZ Mike Holland. I read it & found it dated from Christmas 1996! It got me thinking, what ever happened to the concept?

Granted there is alot more equipment involved, it would seem to have some great utility with emergency networks. Does anyone know of any successful ham trunking networks or ongoing projects? This article clearly states there was usrd equipment available back then, there is even more now. If not, what is stopping it from happening? I fear pesky legalities, the "necklace" some tote around to impose on others these days. Whatever happened to "just do it"?

I have really liked the current technology discussions, please keep it up! I have learned more in 2 weeks than the last 4 months with regards to wireless data! It has rekindled my experimental curiousity. The inclusion of URLs is a good way to share info, websites & pictures of some installations would be a great addition to any thread! More pictures!

Wanted: Pringle cans, all-thread & washers! http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif I love it!

RM

http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif Yo, RM..........

How about coffee cans, dowl rods and copper pipe?

http://www.qsl.net/w0kph/index1.html

Interesting stuff. http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

73 de Craig.........KCØGOA http://www.qrz.com/iB_html/non-cgi/emoticons/wink.gif

[WA6CAW]

Weren't we supposed to get some of the 700MHz band?

P/S and emergency groups have their eyes on most of it, but we should get a small part, my opinion.

de WA6CAW
Lou M.

BTW, here is a link of some interest:

http://www.telecomweb.com

And another (the ARRL?)

http://www.rcrnews.com/cgi-bin/news.pl?newsId=2875

[K9STH]

I am not sure that "trunking" is really in the "spirit" of amateur radio. Primarily, trunking is used so that a number of users can "share" a frequency without their transmissions being "heard" by the others as well as utilizing multiple frequencies with "channel hopping" cababilities. With true trunking, then only a small group of amateurs within a predetermined "group" would be able to communicate with each other, all others being kept out. If this is what is wanted, I think there are other means of communicating.

Whether or not "trunking" is permitted on the amateur bands, my "gut" feeling is that it is not now allowed. But, clarification from the FCC would certainly be in order.

Also, in the vast majority of areas, the usage of amateur repeaters does not necessitate a sharing of frequencies since the relative activity is low.

Glen, K9STH

[WA6CAW]

Hi Glen….. I’m not sure that I totally agree with your post, but let me see if I can explain some possible misconceptions.

One of the main purposes of trunking, is to allow communications in a manner so that it appears to the user that he/she has a private channel. That is the goal of most people that use radio for communications. Hence, cellular arrived on the scene allowing the appearance of the same, to more users, and obviously to line the pockets of the telcos to make much money.

Your description of trunking is basically correct, and is similar to “true” analog cellular communications. I think trunking could exist in amateur radio, with the coordination of tones, much like repeaters are coordinated for frequency and location. A control channel is required, but if designed like the GE trunking system,originally, it too can become a communications channel ,when all channels are required. Channel groups are usually allotted in 1MHz spacing for analog.

Now, if we advance a little more to the digital world, like CDMA, or TDMA, (GSM is very similar to TDMA) only one spectrum area is required for up to 60 conversations at a time, all on one carrier(about 1.25 MHz). This is done by again coordinating digital codes to users, and repeaters work very well in this environment. CDMA probably falls more under the general category of SS or spread spectrum, not frequency hopping. Many other problems, that are normally dealt with in analog communications like multipath interference, multiple access interference, and hostile jamming are virtually eliminated and lower transmission power is required. CDMA can also share frequency bands with narrow band communications, since it requires very small average power in any narrow band slot. This means that it is very difficult to detect the presence of a spread spectrum signal by use of narrow band equipment. There are many more advantages to CDMA, but I’ll leave those out at this time.

So, I think there is no need for a “predetermined” group to exist any more than an open or closed repeater organization. Trunking is a new technology that should be allowed on amateur bands, and the FCC should allow it. More effort in Washington is needed. I stated this in another post on another topic.

Where are the “movers and the shakers”? Let’s keep moving ahead with the technology that is out there and available, at reasonable prices.

Respectfully,

WA6CAW, Lou M.

[K9STH]

Actually, both the GE/Ericsson (i.e. EDACS) and the Motorola trunking systems normally require a control channel while the Johnson/LMR system does not.

However, amateur radio is NOT based upon "private" communications and that is my concern. If one wants private communications, then there are other services that provide for such (and do not require an operator's license). One of the problems in many areas is the fact that there are numerous "private" repeaters that have been coordinated that have fewer than 5 users, if any! But, the coordinating bodies are very reluctant to either "share" these frequencies or to "pull" the coordination from those that really do not operate. Many of these frequencies do not have any activity for weeks at a time. However, if someone tries to use them then the coordinated repeater owner starts "screaming to high heaven". There is not sufficient "crowding" of the frequencies to necessitate trunking operation even if "private" communicatins were in the "spirit" of amateur radio.

The implementation of "trunking" and other "private" communications techniques are not in line with what amateur radio is about. If someone wants private communications, then they definitely should not be operating in the amateur radio service, citizen's radio service, family radio service, general mobile radio service, and any other service that is not intended for such private communications. If they want "private" communications, then go to business radio service, cellular telephones, etc. Amateur radio is NOT the place for "private" communications.

Glen, K9STH

[WA6CAW]

Yes, Glen, Motorola, EDACS, use a control channel for ANALOG communications. EF Johnson, which is referred to as LTR, does not. You have addressed the analog communications scene most correctly. But they only use one carrier with one person talking at a time. The repeater is in full duplex (2 frequencies in use) while the person talking is in ½ duplex, unless they have interconnect, and some times that is ½ duplex.

But don’t you think that 60 people talking at once on ONE carrier is more efficient use of the spectrum? The fact that the other people talking do not hear all the conversations is not what I see as a drawback. Does ham radio have to be a party line operation at all times? I don’t think so. Split band and other analog methods are allowed now! Should that be disallowed? I don’t think so.

All I am saying is that we need to allow new technology in some portions of the ham bands, to allow us to advance techniques, such as QPSK,OQPSK,MSK,CPSK,Trellis-coded modulation, and OFDM. I have not seen any permission proposals in this area. Digital voice and data has been addressed, but no progress yet. Maybe I’m impatient, but any news of this type technology is absent from the periodicals that I read, and I read many.

CDMA can be made to be open to anyone with the proper equipment. A calling channel could be set up to connect to the people wanting to talk” digital”. It’s time to think “outside the box” as some would say.

I am not totally in disagreement with you, maybe just a little ahead of your thinking. My opinion is that there is room for both of our ideas. Do you think?

Keep up the good thinking, and tell me where I’m wrong. I’m able to take it !

Lou M.
WA6CAW