JLeikhim
-
Posts
161 -
Joined
-
Last visited
-
Days Won
10
Content Type
Profiles
Forums
Events
Gallery
Classifieds
Posts posted by JLeikhim
-
-
We are using Asterisk as the server (running on a raspberry pi 3) and the RTCM made by micro-node. Cheaper hardware solutions vs the RTCM are available but require other configuration. I have not used any of the other hardware so I wont touch on that. I chose the RTCM for its single unit design and application specific properties. The interfacing with the RTCM is rather simple, I went with the MTR2000 repeater for reliability, full duty cycle and used market availability.
Our group hosts its own local node server (Asterisk running on a raspberry pi 3) with 6 repeaters connected to it. This local node also allows us access to the MyGMRS national linking network hosted by the owner of this site. By entering commands in Asterisk or using DTMF, links to other systems can be connected or disconnected on the fly. Things like usage counters and the visual map show links with red lines as well as what site is transmitting by changing its marker from green to red, all of this in real time.
Its not as hard as it sounds, Rich from MyGMRS was a huge help, you can also find a linking thread in the private section here. Along the way I found a company that was able to build a custom cable for interfacing the MTR2000 with the RTCM, it provides a reliable solution that's repeatable and works flawless. The MTR2000 repeater can be configured to work with the RTCM rather simply using the repeaters wire-line card to handle the audio and the 96 pin J5 connector to pull ctcss, core, ptt and power.
We are using the RTCM and MTR at 6 sites with a stand alone MTR at a 7th and could not be happier. These machines are worth every penny, its not 2 mobiles in a box its a true full duty cycle, commercial grade repeater. Due to the simplicity I have several more RTCM / MRT2000 combos ready to go I just need to fined a few more tower sites with internet.
Hope this answers a few questions.
Forgive me if I have stirred up a dead thread!
Corey; If I simply get an RTCM and connect to my repeater, configure to and with my home LAN network can I participate in the myGMRS network? Or do I need a server?
-
§ 95.335 Operation of non-certified transmitters prohibited.
Except as provided in paragraph (a) of this section, no person shall operate a transmitter in any Personal Radio Service unless it is a certified transmitter; that is, a transmitter of a type which has obtained a grant of equipment certification for that service, pursuant to part 2, subpart J of this chapter. Use of a transmitter that is not FCC-certified voids the user's authority to operate that station. See sections 302(a), (b ), and (e) of the Communications Act (47 U.S.C. 302(a), (b ), and (e)).
(a)Exceptions. Under certain exceptions, non-certified Personal Radio Service transmitters, or transmitters certified for use in the land mobile radio services may be operated. Any such exceptions applicable to stations in a Personal Radio Service are set forth in the subpart governing that specific service. See e.g.,§§ 95.735 and 95.1735.
(b )Revoked or withdrawn certification. In the event that the FCC revokes or withdraws a grant of equipment certification for a type of Personal Radio Service transmitter, existing transmitters already in service may continue to be operated unless and until the FCC determines otherwise and gives Public Notice of that decision.
©Grantee permissible modifications. Only the grantee of the equipment certification may modify the design of a certified Personal Radio Service transmitter type, and then only pursuant to and in full compliance with the requirements and procedures for permissible changes and modifications in part 2 of this chapter. See §§ 2.932 and 2.1043 of this chapter.
The subparts 95.735 and 95.1735 (GMRS) are shown as "reserved" in their respective sections.
-
Question for discussion...
Programming your own Part 90 radios into Part 95 service, and front panel programming... Is this legal?
This may be another area that needs further clarification from the FCC, or perhaps I just cannot find the rule that applies, but in the past, all type-accepted radio transmitters had to be set up and aligned by (or under supervision of) a licensed technician before they were legal to use. Radio owners/operators were never allowed to modify their radios in any way. A licensed technician used to be defined as "the holder of a valid Commercial General-Class Radio-telephone Operator's License."
Today, we are all programming our own radios for the frequencies we would like to use, and some even modify radios for front-panel programming. Is this even legal?
The only laws I can find about this today are:
95.319 (b.) Internal repairs. Internal adjustments and repairs to Personal Radio Services transmitters must be performed by or under the supervision of an individual who is qualified to maintain and repair transmitters.
95.337 No person shall modify any Personal Radio Service transmitter in a way that changes or affects the technical functioning of that transmitter such that operation of the modified transmitter results in a violation of the rules in this part. This includes any modification to provide for additional transmit frequencies, increased modulation level, a different form of modulation, or increased transmitter output power (either mean power or peak envelope power or both). Any such modification voids the certified status of the modified transmitter and renders it unauthorized for use in the Personal Radio Services. Also, no person shall operate any Personal Radio Service transmitter that has been so modified.
I had never really considered this before, since I do hold a Commercial GROL, and I am a qualified technician, but what about others programming their own radios with eBay cables? What about those internal modifications that allow the front panel to essentially be used as a VFO? This is fine for ham use, but can that possibly be legal at all for GMRS?
Open for discussion.....
95.319 (b ) does not hold much water. It does not specify who those folks might be. However I like that the rule exists. More below.
I am also a GROL. Years ago, the FCC under pressure of a certain Radio Vendor Evil Batwing Corp, removed the requirements for a GROL to perform tuning, repairs and service of LMR equipment. They did this no doubt, so they could pay technicians a smaller wage and to reduce liability. The FCC rewrote Part 90, putting the responsibility on the licensee to ensure the equipment worked as required.
95.337 as underlined, describes the condition under which a modification becomes a violation. You can modify if it still meets rules. So lets say you want to install a wire into the radio to tap the discriminator or grab COR logic. That's a modification, but it is benign. Or you are a bench tech and the radio comes in with a blown final and you determine that no OEM part exists, but you are aware that an MRF123X is same part, install it, test the radio for spurs and harmonics. That is technically a modification, but not a violation. Then comes Sparky McSpark with his golden screwdriver. He goes into the 40 watt Midland and twists some coils and turns a pot and now his bird wattmeter shows 60 magical watts! That is potentially a violation.
As far as Part 90 and FPP. I am OK with running Part 90 radios within the rules. I think the FPP sort of pushes the envelope however. You can accomplish same thing with a small laptop computer and RIB. I was programming Saber Radios with an HP200LX palmtop and DOS RSS long before FPP became a thing.
Back to 95.319 (b ) . If you read the new rules closely (I can't cite off my head) there is as mentioned above, a rule that hints at the use of non part 95 certified equipment and it refers to "reserved sections" within the RC and GMRS rules. I think that a reasonable rule change could acknowledge that certain Part 90 radios are technically compliant with Part 95 GMRS and that 95.319 (b ) could be the qualification required to use Part 90 radios within GMRS.
-
What is the purpose/intent of the FCC Part 95 rules? It appears that the FCC aims to create a uniform standard for transmitter emissions. Following the "spirit" of the rules regarding frequencies, power output, bandwith, deviations, etc. seems to be the important aspect that allows GMRS users to have a reasonably functional band. Why does it matter how you configure or construct your transmitter if it comports with the emission standards? To a reasonable person, the "letter" of the rule would seem less important than the "spirit". Obviously, the FCC missed the common sense boat during their last rule-making session. Since I am new to GMRS, does anyone know how often they consider making changes?
The Certification rules are written as much for the manufacturers of new radios as they are for the licensee. If you look at the history of FCC enforcement of equipment certification you will see little of it has been directed at the licensee.
What does all this mean?
If you have a radio that was certified in 1989 under much less stringent rules, it is still certified. I have some Motorola Systems Saber radios. They are dual certified Part 90 and Part 95. They also have some features that if activated clearly violate some rules, like encryption. But the radio is still certified and if programmed and operated correctly complies with present rules.
If the FCC were to crack down on the use of part 90 equipment used in GMRS, they would be very busy. I think that even though you may be driving an automobile with a helicopter turbo jet engine, violating all EPA and NHTSA standards, as long as you stay between the lines and watch your speed, the police won't bother you.
Now the problem is, that there are a lot of newbies buying some pretty dodgy and cheap Chinese radio gear and they may be inclined to install an equally cheap 50 watt Chinese power amplifier to this gear. If they do that, and a spurious signal bothers the local air traffic control tower, they will be in a heap of trouble.
-
"(ii) On a non-profit basis, with contributions to capital and operating expenses including the cost of mobile stations and paging receivers prorated equitably among all participants"
This says you can charge, but you would really have to form a legitimate non profit and get a CPA involved in the books. And Corey is right, you may have some hassles. I am considering a no-fee arrangement with tones for private use, but with some certain operating rules so that if, frankly, I don't want someone using it because of their behavior, I can send them a certified letter telling them they have violated rules and must go away.. I would send a nice letter first. I just don't want to have to punish everybody by pulling the plug.
-
Ok, I'm still confused. Does this mean that old part 90 radios are automatically certified for part 95 transmission? or does the manufacturer have to request, and be granted certification in both 90 and 95. Can we ask the FCC what they mean? "Hey, FCC, can I use my part 90 certified business class radio to legally transmit on all FRS/GMRS frequencies under my GMRS license? If yes, what grants me the authority to do so?" I have searched extensively and can find no FCC rules that expressly permit Part 90 radios to transmit on Part 95 FRS/GMRS freqs. Did no one address this during the Part 95 NPRM discussion? If so, what were the FCC's findings? I have found very few Part 95 repeater capable mobile units and even fewer handhelds and would like to know that using readily available Part 90 radios is in compliance with the code.
This is an interesting question. There may be some overlap where the rules permitted part 90 radios and the age of some older equipment. Hopefully your license is likewise that old.
-
If anyone has verifiable official documentation that ANY GMRS licensee has ever been given an FCC citation for using a Part 90 Type Certified "transmitter" in Part 95 service, please add that documentation to this thread.
I have searched the FCC NAL listings going back many years and I have never seen an NAL for either type certification or for linking via any means. Honestly, the only NAL's I found were for corporate businesses blatantly using GMRS or that Bundy guy in California who happens to be a GMRS licensee jamming Part 90 users. GMRS has a pretty good record with the FCC.
-
The vast majority of GMRS Repeaters are Part 90 Type Certified. The technical standards in that regard are almost identical between Part 90 and Part 95 and we know of no instances where a station inspection netted a citation from the Commission for a licensed GMRS operator using a PROPERLY OPERATING Part 90 system in Part 95 service. If ANYONE has DOCUMENTATION of such a citation, please add to this thread with that data.
The Rules that were recently modified "seem" to address this partially - Section 95.1761 Sub C, "No GMRS transmitter will be certified for use in the GMRS if it is equipped with a frequency capability not listed in §95.1763, unless such transmitter is also certified for use in another radio service for which the frequency is authorized and for which certification is also required. No GMRS transmitter will be certified for use in the GMRS if it is equipped with the capabilities to operate in services that do not require equipment certification, such as the Amateur Radio Service. All frequency determining circuitry (including crystals) and programming controls in each GMRS transmitter must be internal to the transmitter and must not be accessible from the exterior of the transmitter operating panel or from the exterior of the transmitter enclosure."
Also, refer to Section 95.335 - especially Sub A, "Except as provided in paragraph (a) of this section, no person shall operate a transmitter in any Personal Radio Service unless it is a certified transmitter; that is, a transmitter of a type which has obtained a grant of equipment certification for that service, pursuant to part 2, subpart J of this chapter. Use of a transmitter that is not FCC-certified voids the user's authority to operate that station. See sections 302(a), (b ), and (e) of the Communications Act (47 U.S.C. 302(a), (b ), and (e)).
(a) Exceptions. Under certain exceptions, non-certified Personal Radio Service transmitters, or transmitters certified for use in the land mobile radio services may be operated. Any such exceptions applicable to stations in a Personal Radio Service are set forth in the subpart governing that specific service. See e.g., §§95.735 and 95.1735."
Disclaimer: The Staff at MyGMRS is supplying this data as information only and assumes no liability for it's use by individuals. It is the responsibility of each licensed user to know and follow the most recent Rules covering the radio service that they are licensed for.
Interesting! See e.g., §§95.735 and 95.1735." Those sections are actually reserved. Could it be the FCC contemplates allowance for Part 90 equipment? This has been raised during the NPRM. To be honest, to be fully compliant with certification and to have a proper 50 watt 16K03FE or 20K0F3E emission as intended, requires one to choose from a small number of obsolete products. Some of them quite good, like Motorola Systems Sabers or Kenwood TK-8302H . I am actually building a repeater that will be 99% compliant. The PA is the 1 % problem.
-
Ritron has some older radios that are indeed part 95A certified. The DTX-450 RF Modem for one.
If you want certified mobiles I would recommend the Kenwood-TK8302HU-UHF-TK-8302HU
-
I found uploads dont work as well.
-
Is this proceeding still open? Any resolution. It worries me when Motorola asks for something. There is usually some over reach. Having 30 of those GPS gadgets on a channel at a national park will be a mess. And yes, at bubble pack prices, folks will be attaching them to their cars and motorcycles as a poor mans lojack.
-
( Check 95.339 for additional specifications on this topic. )
The effect of this rule is that you don't violate rules to begin with. There is no distinct prohibition on attaching a Part 95 approved amplifier to Part 95 exciter/transmitter.§ 95.339 Operation of transmitter with external device causing rule violation prohibited.No person shall operate any Personal Radio Service transmitter to which an external device or accessory has been added such that operation of the combination results in a violation of the rules.
The reality is that a lot of Part 90 equipment is routinely used on Part 95 and the FCC is fully aware of this. It is inevitable that high performance Part 95 equipment will cease to be manufactured. I say inevitable but reality is that the crap being sold as Part 95 by the manufacturers is narrow band and that in itself renders GMRS impotent. Licensees need to choose equipment carefully and petition the FCC to permit certain Part 90 equipment (that meets Part 95 specs) be permissible. At same time, reject manufacturers who see GMRS as FRS on 15 watt steroids.
- Ian, RCM and Elkhunter521
-
3
-
Transportable != mobile. Compliance could be achieved by, for example, powering it from an external 120v circuit via extension cord, or a double-pole double-throw switch that disconnects the battery from the vehicle and prevents vehicle operation while the repeater is in operation. Tapping the signal line to the "BRAKE (!)" light on the dash to enable the repeater controller is yet a third option. This is an engineering problem, and it is fairly tractable. I may not have the patience to hack together the fanciest options, but running the gear off an extension cord should be quite simple, and would in fact allow me to locate the whole kit 'n caboodle in a truck tool box that can be moved, removed, or carried up a freight elevator if a rooftop is available and convenient.
Exactly the edge-case I have in mind. Besides that, the balloon-lofted antenna in my hobby project simply cannot be deployed in motion, or you won't have a balloon-lofted antenna - or any antenna - very long. I was planning on something to support a local festival like the Highland games, and people enjoying themselves there. (PS, really don't use that thing around power lines, and especially high-tension lines.
)I'm working on it. But mostly this stuff is already available to amateurs, and does me absolutely zero good 'cause nobody else I know has, or is willing to, get an amateur license. If they give me a justification, it's either due to not being arsed to study, too much hassle, or perceived toxicity in the culture surrounding amateur radio. "Pushing forward the state of the art" as used here is really about improving the products available to customers via retail channels. Finding new handies that are repeater-capable is an exercise in scouring eBay for new old stock. I think the only products available are the TERA TR-505 and the BTECH GMRS-V1; the former requires PC programming and won't cover all the channels in the service, the latter requires … actually the BaoFeng meets spec IMHO.
I mean, if nobody makes it yet, there's always Kickstarter…
Not that I'll be ready for that until I have a few more years' experience under my belt, but I still really like the idea of a combination satnav and 50 watt GMRS radio.
I don't think you have to go to fancy extremes to be compliant. Just don't operate with a balloon tailing behind you on the 417!.
"perceived toxicity in the culture surrounding amateur radio"
I am a ham and have seen this time and again. Folks ask on the board how they can get reliable two way communications for family and the answer right away is to get a ham license for every member of the family. I know of a few families where that is the case, but they are unicorns. Then there are the FCC "Nazi's" who look for an infraction in every sort of activity not positively supported by the rules, or twist wording to favor their prohibition de jour. Fact is If it is not specifically prohibited it is probably OK, The FCC's GMRS infraction filing cabinet buried deep in warehouse 13 in Gettysburg is mostly an empty drawer. The few NAL's they write are commercial users on GMRS channels. Or GMRS operators that are jamming part 90, well one guy from California basically. The filing cabinet for Ham radio infractions takes up three floors.
- mainehazmt, Ian and Elkhunter521
-
3
-
95.1 The General Mobile Radio Serv- ice (GMRS).
(a) The GMRS is a land mobile radio
service available to persons for short-
distance two-way communications to
facilitate the activities of licensees and
their immediate family members. Each
licensee manages a system consisting
of one or more stations.
GMRS is not a hobbyist service, it is not for expanding ambitions, it is not a place to push the state of the art forward. However, there is a place for that... Amateur Radio. Per the FCC, Part of the Basis and Purpose of amateur radio is the: Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art. If those are your interests, get an amateur license.
Oh god, I will have to put my flame suit on. Here it is. I am a licensed ham, have been for years and have pushed the state of the art in many venues. Built an amateur radio satellite station, worked the world, constructed a 98 foot tower etc. Spent a lot of money at AES.
However every so often I get the bug to build a repeater. I am building a repeater for GMRS and not for ham as my immediate family will not benefit. This is something my neighbors might benefit from as we are in a hurricane area and power and communications are out at least a few days every year.
So I am building a 50 watt (wide band ) GMRS repeater with quadruple receiver diversity. Yes folks I intend to push the state of the art forward. All parts will be Part 95 certified. The four receivers will each have a separate diversity antenna mounted with separation to exploit the uncorrelated multipath signals. One of the four receive antennas will be a horizontally polarized loop to exploit angle diversity. Why am I doing this? To improve the reception form a 5 watt handheld so that talk back reliability approaches talk in. The heart of this is the repeater shelf I am assembling and the brains are a surplus JPS SNV-4 voter which has DSP S/N voting and DSP noise reduction. Will it work well? I think so, that is part of the fun. Once the fun is over I will have a powerful GMRS repeater in my town.
- RCM, Elkhunter521, Ian and 1 other
-
4
-
I've said it before and I'll say it again, you can't do a vehicle-installed repeater. Repeaters must not be capable of operating while moving, and cannot have a mobile operation mode. It's written in the Part 95 definition of a repeater station. They must operate at a fixed position. The specifics of what defines a fixed station is a question I'm trying to raise to the FCC's attention.
(snip)If I read correctly what Ian is describing, it is a repeater to be used at a fixed location on a temporary basis. And using a balloon hoisted antenna. There is no prohibition in the rules for such a station.The fact that it is installed in a vehicle does not preclude lawful operation of the station when deployed at temporary locations. A fixed location is not a specific location. It is simply a stationary one. Further the FCC no longer licenses fixed GMRS stations by site so there is no expectation of a protected service area other than using care to operate without interference.
§ 95.303 Definitions.
Repeater station.
A station in a fixed location
used to extend the communications range of
mobile stations, hand-held portable units and
control stations by receiving their signals on one
channel (the input channel) and simultaneously
retransmitting these signals on another channel (the
output channel), typically with higher transmitting
power from a favorable antenna location (typically
high above the surrounding terrain).
-
The Northern California GMRS Users Group (NCGUG) has started to see an uptick in direct mode/simplex users on our repeater inputs over the past month. Some are not encoding tone, other are using 88.5, D031, D606, D172, and a few others.
Has any new programmable radio been released that is different than those that came before? Or one that ships with the 467 MHz uplink channels configured/configurable for Direct Mode?
This may also be a growing lack of understanding of these channels? As our repeater receiver is at 2,200 ft. AMSL, it easily hears handheld radio users within a 20-30 mile radius, and they can wipe-out our users when they are weak.
Occasionally they use one of our active codes, so their "discreet" (and likely unlicensed) comms are being retransmitted everywhere.
Normally such destructive interference was from heavily-accented maritime users at a nearby shipping port. But these new users are all english-speakers with little to no accent, with some minor exceptions. No callsigns are being used, and many seem to be unsophisticated radio users (which tells me some new radios are being sold with 467 MHz direct mode channels in them).
Greg
KAF1291
Greg; If you have repeaters on the band edge, be aware the FCC now permits part 90 NXDN operations INSIDE the lower and upper edges of Part 95, they did this against there own previous practices and despite objections. Unfortunately the GMRS community kind of snoozed on this "guard band intrusion" and now it is here. If you operate a repeater on the upper and lower pairs, and especially if you have an AFC (Micors), there may be interference. Because the FCC no longer license GMRS repeaters by site, who is to say who is the incumbent should there be a part90 vs part 95 shooting match.
-
That is certainly good to hear. I am building a new repeater and trying to comply with Part 95 . Finding a PA has been a worry. Aftermarket PA's are commonly used with Part 90 equipment and as such, I have not seen any concern as to specific certifications. It is the exciter that does the heavy lifting as to modulation emissions. The PA if well designed and terminated into a proper load should do fine.
-
Some of those random attempts might be folks with "low parts count" radios from China. Many don't provide adequate deviation and the CTCSS tone might be weak.
-
A couple of years ago there was a Doctors office near me that was using GMRS. I set my simplex repeater on that frequency and PL for a few days...after that, never heard them again. I guess having to hear themselves repeated back all day was annoying! Imagine that.
That is so excellent!
-
Years ago, the FCC approved maritime "port operations" on UHF channels with non standard repeater pairs. some of these operations are simplex as well. It is all supposed to be low power.(2 watts) Some of the frequencies are in the GMRS band. It is not unusual for cruise ships to be on these frequencies.
If you call the ship on the radio, be polite and simply indicate interference and request the vessel name and or to talk to the captain to get company contact information. Be sure to ID your GMRS station properly. Use simplex, don't use their input frequency! Mostly I would listen for clues as to what ship it is coming from and contact the IT or Telecom director at the Cruise company by writing a letter (and CC your local FCC field office) and simply request the use an alternate tone.
-
I have a bunch of RITRON DTX-450 modules I need to program for a GMRS repeater project. It is a one time deal so I intend to cobble up the 3.5 mm programming plug and wire to a Motorola RIB box. The problem is that the documentation is unavailable to determine which of the tip, ring or sleeve are for TX and RX data. I am assuming the sleeve is data ground. The only schematics I can find are for a cable that terminates in an RJ plug for use with RITRON's proprietary RIB, and the data labels are missing. I am using a Motorola RIB, so any help would be appreciated.
I assume the same cable is used for Jobcomm and Patriot radios.I am in Orlando Area if anyone is willing to loan out their programming kit for a day.
Thanks
-
I want to point out that the FCC is once again proposing to encroach inside the band edges of the GMRS band .
Recently the FCC has approved waivers for several commercial part 90 operators to encroach in this manner. I apologize in advance for cross posting this on other boards, but this is important and is likely not to be noticed by many.
This started in about 2013 when Mobile Relay Associates of California requested to encroach on Part 95 band edges in LA and Miami. The GMRS community did not react and the FCC subsequently awarded waivers to permit MRA do do this without any reservation, nor any technical data in support that doing so would not cause interference to incumbent 25 KHz GMRS operations.
At a later date MRA attempted to obtain similar waivers to encroach on other spectrum and has been denied because "the assignment of non Part 90 spectrum to Part 90 licensees was contrary to FCC procedures". So in one case the FCC ignores their own procedures and assigns GMRS Part 95 spectrum to MRA and in another case, the FCC denies MRA access to spectrum which was part of the auctioned Radio Common Carrier band.
If you are a GMRS licensee, I urge you to respond vociferously to this FCC NPRM and make your voice heard,
"On its own motion but suggested by recent waiver requests, the FCC proposed to make available for PLMR use frequencies that are on the band edge between the industrial/business (I/B) pool and either general mobile radio service (GMRS) or broadcast auxiliary service (BAS) spectrum, to make certain frequencies that are designated for central station alarm operations available for other PLMR uses. The FCC also made certain updates and corrections and amended its rules to accommodate certain railroad operations.
Specifically in the I/B pool, the FCC proposed to amend the frequency table to add frequency pairs 451/456.00625 MHz and 451/456.0125 MHz, with the limitation that the authorized bandwidth not exceed 6 kilohertz.
The commission also proposed to amend the I/B pool frequency table to add frequency pairs 462/467.5375 MHz and 462/467.7375 MHz, with the limitation that the authorized bandwidth not exceed 4 kilohertz. “We tentatively conclude that it would be in the public interest to make additional frequencies available to PLMR applicants that can be utilized without overlapping the occupied bandwidth of currently assignable frequencies and without causing harmful interference,” the NPRM said."
Link to article
-
I seem to recall that T1504 was a four bandpass/reject cavity duplex filter. It may have been sold as a kit of parts. But in any event depending upon the frequency band you got a set of critical length interconnect cables and a "T" connector. The duplexer is band pass with reject notch filters. The band pass is wider than the reject notch so after first tuning band pass, then tuning reject, you could fine tune the reject with the pass knobs. That is how I did it and they worked well. The trick was that the screws on the slotted reject loop had to be almost tight so they made reliable connection and then I would "rap" the screws one direction or the other in the slot to tune the notch. A couple Excelite nut drivers were the ideal tools to move the knurled nut. Use one as a "hammer" and the other as a "chisel" and tap their plastic heads together to move the nut just enough. Then hand tighten,
-
So for those of us that have very little technical knowledge - if this is a bad thing for GMRS how about a member with more information and ability provide a sample letter that we could copy and send to the FCC or congressman or senators - any or all - whoever would be appropriate so we can try and prevent this?
Just a thought
Dan
You might take a look at the responses to NPRM 10-106 and find a style and preamble that you are comforable with.
Tell FCC who you are, why GMRS is important to you, and then explain why it is detrimental to have commercial operators inside the now protected 25 KHz bandwidth of the band edge GMRS channels. You might cite the existing guard band the FCC has in place as being good engineering practice.
Whatever you do, don't get caught up in copycat letters. In 10-106 there were a slew of essentially form letters sent by well intended folks. However, one of those mailings had a technical error which implyed the respondents were pro something they were likley not. Additionally the letters lacked the vitality of individuals who were passionate about the cause.
Unlike NPRM 10-106 which required dozens of pages to respond, this filing can be dealt with in a few paragraphs unless someone wants to make an engineering argument.
Why "More Power" Isn't The Answer
in Technical Discussion
Posted
I am going to throw out some ideas for those who are repeater operators. It is an area I am exploring.
By now everybody realizes that a 5 watt portable talking through a 50 watt repeater will have its range limited to the ability of that 5 watt portable to "make" the repeater, lets say 8 miles. If that 5 watt portable is talking through the repeater with another user with a 50 watt mobile some 20 miles further distant, that is an inherent accomplishment of the technology.
In the public safety arena, UHF 5 watt portables are the critical users. Users want that portable to work everywhere. Public safety seeks to design systems to 97% reliability within a jurisdiction (town/country/statewide). Reliability is the name of the game. A TIA document TSB-88 describes how such systems are designed and tested.
For example, if you wish portable coverage throughout a large city or county, the use of satellite voting receivers has long been the solution. Each of these voting receivers has a reliable footprint where a 5 watt portable can be received. Lets say that a small city has three satellite receivers at various locations and where the city boundary is reached, the coverage from any single receiver is 97% reliable. However in other areas within the city, the coverage drops to 70% reliable , if the other two receivers in the system overlap those areas and are also 70% reliable or greater, then > 97.3% "Joint Probability" is attained when the voter switches between strongest signals.
For the typical GMRS repeater operator, constructing such a system would require having antenna towers at various locations and a means to bring the signals back to a voter by phone line or other circuit. The towers alone would be costly to build, rent or maintain.
However, the hardware, satellite receivers and Voters are readily available on the surplus market and can be pressed into use in a much different way on one site, preferably a rooftop..
All three receivers can be co located on the same tower or rooftop and be used to facilitate multiple receiver diversity reception. Diversity reception can work with two repeaters, but we will use three in this example.
If your repeater had 70% reliability out at 8 miles, you could improve the reliability to 97.3% in theory by adding two more receiver antenna branches.
To get maximum return, there is a need for the antennas to each receive uncorrelated signals from that distant portable. In a hilly or urban area that may easily be the case. The antennas will have to be physically separated many wavelengths from each other on the tower or rooftop to yield diversity gain. A caveat is that the additional two receivers will need bandpass / notch filters to filter out the transmitter, just as a duplexer would do for a singe receiver station..
I will provide an excel file "Joint probability example" to anyone interested. I was unable to attach it.