Use of 168.5500 MHz

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Mike_G_D

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Been busy with life stuff so sorry so late in reply.

Zerg, I'm nobody special but I do have a professional technical background in RF engineering (primarily TDMA cellular stuff, DSMR handsets, terrestrial+sat handsets, some digital cable TV stuff that didn't do good things to my career - nuff said, and some Bluetooth reference design for RF IC design folks) and have been a radio hobbyist for over 38 years and am VERY familiar with the technical (the internal radio design aspects as well as the operational aspects within various environments) aspects of LMR operation.

Enough of that junk...

Rereading my last I think I came off in a pretentious fashion for which I sincerely apologize! Nevertheless, I stand by my basic assessment - the solution presented for the jumpers and rapellers is certainly not ideal but is acceptable given the usual operating environments and procedures as outlined by ExSmokey and others and given the limitations of available channels in the newest Federal pool PLUS the more nebulous aspects of typical Federal bureaucratic operational procedures. I leave it to ExSmokey and others like him to inform us about the wildland management and fire fighting procedures and "dumb them down" for those of us not involved in those professions just as I try to do from a RF technical angle.

I cannot say that the use of one frequency to handle both rapellers and smoke jumpers using different CTCSS tones will NEVER result in problems at some point in the future nor can I say that no injuries or deaths will result directly or indirectly from that solution. I don't really think anyone can - we CAN present possible scenarios or models that COULD result in such problems but then we have to look at the real likelihood of those situations actually happening and weigh that against the other limitations that the planners had to contend with which included but were not likely limited to what frequencies were available and what governmental bureaucratic obstacles were in their way given the time limit they were operating within.

No matter how much thought, sweat, blood, and tears you throw at a solution, in a human environment within current corporate or government institutional constraints you will HAVE to make compromises and you will almost certainly NOT be happy 100% of the time with all of those compromises. I know this from my RF engineering lab experience and I am pretty certain that ExSmokey knows this from his experiences in wildland management. So many times in my experience engineering staff knew what the best solution to a problem was but were not allowed to implement that solution due to cost constraints or to other design constraints they had no control over. A compromise was the only game in town - that's pretty much the name of the game in practical engineering and I rather think also in all of life.

I wish ideal solutions could always be implemented to all problems but it simply can't be; sometimes the constraints put upon planners of any profession and at all levels will seem ridiculous when viewed from only one or only a limited number of angles (e.g. in this case from only very narrow technical and operational points of view one may not understand why only one radio frequency is made available to two usage groups) but will make more sense when the view is widened to include the less elegant aspects of the entire planning environment (available resources, conflicting needs from rival departments, the relatively slow speed of governmental procedure modification and implementation, etc.).

As ExSmokey said, in the documents outlined the powers that be have stated they will modify the solution to give exclusive frequencies to the two groups if recurrent situations of harmful interference are noted. I know you can fire back that someone could be injured or die in the meantime but choices were made within limited resource environments and given constraints we can only guess at - again, the ideal may be a laudable goal but is seldom if ever reached.

-Mike
 

SCPD

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Mike, good post. Thank you. Another factor that sometimes affects the design and use of a radio system is ego. People at the decision making level may not consider the input of field going personnel and/or engineering staff because their idea is not one that the manager came up with. Additionally there can be some managers that may not be all that competent and may want to show that he/she really does know something by coming up with their own idea. That idea may not workwell on the ground, but it may be incorporated into the system design or use.

I've experienced these ego/competency issues when working for private sector corporations and small businesses, most especially the latter. Small business owners tend to reject proven principles of human resource management due to their egos telling them that they intuitively know how to run things and reject those principles because they are too "corporate or government" originated. I've also experienced one competency issue on one of the four ranger districts I worked during my career. The feds send you to the best management training available and some people just don't practice what they have been trained in.

On incidents competency and ego issues are much less of a problem as people don't obtain command positions due to politics as they sometime would before ICS was implemented. Task books have long lists and many incidents and supervisors have to sign off that tasks have been completed. Politics are still a factor due to human involvement, but it is a much smaller factor in incident management. I don't believe these issues interfere with critical life and death aviation and incident communications design and use.

NIFC personnel reach management positions based on experience based on my limited observations. Limited as I've just seen a couple of excellent dispatchers move on up to NIFC. Both of them gained it by being a ground pounder, then a dispatcher before they transferred to NIFC. Comm personnel in the NIFC partner agencies are generally quite dedicated and understand the importance of their jobs and want to serve the "customer" as best they can. This situation with smokejumper and rappel being on the same frequency will be solved should a problem arise.
 

Mike_G_D

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Fred,

Yep...understood and agreed with; egos are certainly relevant factors including one's own (yes, I am talking about myself here - I have been my own worst enemy on occasion). Interesting point you made about small business managers - think I've seen that in startup situations too. Anyway, we're getting off topic here...

Zerg,

You asked: "Another good question to consider - if there are absolutely no other freqs available such that smoke jumpers and rapellers can be given separate exclusive channels, then is it better to use 2 PLs, 1 PL, or no PLs?"

Assuming both groups are operating simultaneously within radio range of each other using analog FM (today's "wide" +/-5KHz or today's "narrow" +/-2.5KHz deviation) low power VHF handhelds with standard "rubber ducky" negative gain antennas and also assuming that they are not so close so as to interfere in a severe harmful manor with the opposite groups' communications (that is, the capture effect is maximal and effective) then:

1) 2 "PL's" - Very effective and most preferred as it would keep members of each group from being distracted and confused by the opposite group's communications while still allowing each group effective nearly "simultaneous" usage of the radio frequency using the FM capture effect as the interference "buffer". I believe this is the reason that the two tone usage was called for and outlined in the noted documents.

2) 1 "PL" - Not effective if both groups must operate independently of each other (due to the confusion and distraction of hearing the communications of the opposite group while in service) but possibly effective if both groups were operating under a unified central command structure such that they were effectively operating as one large group. In the latter case, though, communication would have to be tightly disciplined such that the two groups did not try and communicate simultaneously (possibly due to "force of habit" for example) amongst their respective members over the radio - which is why I say a "unified central command structure" such as one person designated overall leader and coordinator on the ground would be in effect.

3) No "PL" - same as #2, essentially no difference from carrier squelch mode unless there were still other receivable groups also using that frequency within in radio range of the two groups in question which must be muted, traffic-wise (assuming those "other" groups used a different tone or no tone).

If we change the assumptions such that both groups are now operating so close to each other so as to rule out effective FM capture effect benefits then I would say that the powers that be would be extremely likely to consolidate both groups into one effective situational "super group" and give them one common communication channel anyway - they would all be operating in close cooperation with each other and would operate under a unified command structure as outlined in scenarios #2 and #3 above.

The above are purely theoretical and hypothetical and are, in my case, solely based on my understanding of RF and basic low power VHF handheld radio usage in the field; I cannot comment on the actual likelihood of said scenarios - based on what Exsmokey and others with similar professional backgrounds have said, they would seem to be unlikely.

-Mike
 
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