Lscott

I seem to remember somebody claimed to have setup their repeater as a trunked system which required the radio to electronically send its serial number. The serial number(s) for “approved” radios was entered into the repeater’s system software. In that case tones were useless to gain access. Spoofing a radio’s ESN takes expertise in hacking the radio’s firmware and or hex editing the image loaded into the radio’s micro’s memory. This is something basically your average repeater jammer/clown likely won’t have.

I usually have my radio on scan so it doesn’t matter much. It doesn’t take long to scan 15 channels. I have the radio programmed to stop when the PTT button is pressed on a channel I want to use with activity. It also helps to program in a decently long delay before scan resumes too.

It’s about the same thing using a VOX setup. It takes a bit to get use to giving the system about a second or so delay. Once you get in the habit it sort becomes second nature. I had used a VOX headset with an HT years ago running mobile. Didn’t take long to get it right.

You need something like one of these refill cartridges that IBM makes for their stuff to fix your radio.

Sooner or later somebody will propose using channel 2 for dirt bikes (2 wheels), channel 3 (3 wheel types), channel 4 (for the Jeep crowd), channel 19 for those that can’t figure out the logic for the first few channels etc. Yup, something for everyone. Get enough people confused that means less people jamming up your favorite “official” road channel.

Well one Ham got tired of people using cheap Baofeng radios, and other similar CCR’s, on his repeater. So, he switched over to require a MDC sequence to activate it. The cheap Chinese radios typically don’t have it. It effectively kept them off his repeater it seems. Of course he got branded as a Motorola snob. However some of the other main stream commercial radio manufacturers have it as well, not universally on all models, so it’s not that huge of a limitation. I have it on some of my Kenwood’s, for example the TK-5220/5320 P25 ones in my collection. There are some other Kenwood models I have with it too besides the ones above. https://www.urci.com/downloads/kenwood/kenwood_tk_5220_5320_brochure.pdf The TK-5320 with the band split of 450-520 has FCC Part 95 certification, FCC ID ALH378500. The radio can be programed and used for GMRS legally provided power, frequency, bandwidth and modes are followed as listed in the rules. One could use the MDC signaling as a means to keep unauthorized users out of a private GMRS repeater. Another use would be to identify which radio in your group is transmitting. This is advantageous when the radios are all operating under the same license. Let’s say you’re out camping, hiking etc. and one of your family members is injured and can’t speak. Simply keying up the radio will uniquely identify who it is.

I estimated at least 5 amps for a 25 watt radio and about 9 amps for around 50 watts. I think the minimum you should look for is a 15 amp power supply. https://www.hamradio.com/detail.cfm?pid=H0-003728 While this one is a bit more expensive than the one you looked at it does have ample current capacity to power your radio or a 50 watt model, many use this for 100 watt Ham radios, if you choose to move up for more power. The extra outlet and power connections are handy for powering other devices at the same time. One nice feature is the noise offset adjust. Every switching power supply will generate high frequency trash, some more than others, that may show up on the frequency you want to operate on. The adjustment allows you to change the internal switching frequency by a slight amount, usually enough to get the garbage off the frequency you are using.

A Halfwave antenna has a “matching network” on the end, usually in the base area, that a 1/4 wave doesn’t have. You can’t simply cut a 1/4 wave antenna for a lower frequency and expect it to work as a 1/2 wave with no ground plane at a much higher frequency.

Exactly correct.

As long as the ID is made by the rules who cares what language is spoken on the repeater. You’re not trying to hide or obscure the communications so it shouldn’t matter to anyone else.

I would recommend a LFP, Lithium Iron Phosphate, battery pack over a cheap Lead Acid type. https://www.bioennopower.com/collections/12v-series-lifepo4-batteries Lead Acid batteries, gell, glass matt, marine etc. all suffer from the same short comings. First they don’t like sitting for extended time periods in a partial state of charge. When they discharge lead sulfate forms on the plates. Newly formed its porous allowing the acid to penetrate so on charge it is changed back to lead or lead dioxide, depending on which plate it is like the positive or negative one. Allowed to sit the porosity decreases and the areas where the acid can’t penetrate results in a permanent loss of capacity. The common practice of using a trickle charger is employed to combat this. The next problem is the terminal voltage during discharge. It starts off around 12.6 volts and drops fairly steadily as the battery discharges. Mobile radios are typically designed to operate on a 13.8 volt electrical system, which is what you have when the car’s alternator is charging the battery. The range is usually plus or minus 15 percent of that 13.8 volts, so the low side is around 11.73 volts. That’s about 50 percent, more or less depending on discharge rate, of the battery’s capacity used. http://scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf At the low voltage spec radios may behave erratically, shut down and or loose significant output power. LFP batteries largely avoid the above problems. You can leave them sit around for months in a partial state of charge without damage. The terminal voltage starts out around 13.3 to 13.4 volts and remains around 13 volts for 70 to 80 percent of the discharge capacity. That makes for a better match to the typical specifications for mobile radio gear. https://footprinthero.com/lifepo4-battery-voltage-charts The LFP batteries are significantly lighter than similar capacity Lead Acid types. Much better for backpacking etc. Now the major negative of LFP battery packs is the cost.

You could try using a very small dab of Vaseline on the seat area of the hinge. Recheck the match afterwards to make sure you are getting metal-to-metal contact. Any gaps in the seat area should be filed in with the Vaseline blocking any water ingress. If that works likely you need to recheck it every few months and reseal it with fresh Vaseline. I would also lube up the area where the center section slips down in to the collar with the Allen screw used for adjusting the antenna height up and down a bit.

The yearly license fee doesn't sound too bad if you use it frequently. A 3 day turn around time is quick. What is the typical charge to get, lets say one frequency (or pair for a repeater), for business use? I've seen people mention anywhere from a few hundred bucks to thousands. Reason for asking is on these forums it's been suggested that anyone who wants a "private" frequency for communications get a business frequency. That ignores if you even qualify for one. If you do and the cost is reasonable the suggestion makes sense.

I’m going to guess the coordinators use some software tools to estimate area coverage and signal levels to figure out potential interference to co-channel users. Are these publicly available, free to use, or expensive proprietary software?

Well at least a few people figured out CB radio is used for “communications” not to generate attention grabbing noise, make a fashion statement or stroke one’s ego by being the channel king.

I wonder how long it will take before you see these showing up on eBay at a cheap price.

Thanks. That was a very good detailed explanation. Tower rental costs isn’t something I see mentioned hardly at all on these forums. Hams get spoiled since a lot of them get freebie, or nearly so, space on buildings etc. Everyone else ends up having to pay.

Ok. The modified radiation pattern due to the tower acting as a passive reflector makes sense. Another group member here has done it on a multi bay vertical where the mast was the reflector. I modeled it using EZNEC and it does work. There was noticeably higher signal strength on the side opposite the mast. It wasn’t a huge difference however. I get the extra revenue from more antennas mounted on the tower, and using it the shield one antenna from another, why you see a lot on side arms. I just thought it a bit odd nothing was mounted on the top spot on a number I’ve seen.

Here is a question. I've noticed on some towers than none of the antennas extend above the top of the structure, all are mounted on side arms. Is that done to stay under the permitted height of the tower?

The new DHS bureau of disinformation will put an end to that idea.

It would nice if they did. This topic should be split off into a separate thread. However some of the benefits might be lost along the way, increased channel capacity and lower battery drain. People are confused enough trying to figure out repeaters, offsets and tones. Now you want them to understand talk-groups, color codes and time slots? I suspect if it ever does get approved it will look more like the DMR446 license free service you see in Europe as a DMR tier 1 service. There the radios transmit on both time slots I believe from a few websites I've been too looking for info. The later might be country specific. So much for added channel capacity and lower average TX power savings. What they do for talk-groups I'm not sure. https://kenwoodcommunications.co.uk/files/file/comms/uk/pmr446/PMR446-White-Paper-V6_18AUG2016_JT_KB.pdf They also have dPMR446 which uses FDMA, which is very similar to NXDN. Note they have several different codecs that can be used. You can find the Chinese dPMR radios, most are really DMR (TDMA) based, while a few are FDMA but use some Chinese specific version of a codec that is not compatible with the AMBE+2 you typically see in NXDN, P25 and DMR radios from the major manufactures. https://en.wikipedia.org/wiki/Digital_private_mobile_radio Confused? Yes they have three different modes used on their license free service, the equivalent to our FRS radios. It seems to work for them so I don't see why it won't here.

You can get the optional spring and swap out the lower section in case you forget for that antenna. I recommended that for a buddy at work and he installed it.

You can no longer use voice inversion on GMRS. That was one of the changes made in the 2017/2018 rule updates I believe.

I believe Motorola’s patent on MDC has expired. That would mean it’s no longer even a “proprietary” signaling system. The patents are listed at the end of the below article on Wikipedia. The technical details are known how it functions. https://en.wikipedia.org/wiki/MDC-1200 Several of my Kenwood commercial radios have it. For example the TK-3360. https://pdfs.kenwoodproducts.com/16/TK-2360&3360Brochure.pdf The radio can be easily programmed to work on GMRS, however it’s only certified for Part 90 so it’s not strictly legal to use except on Part 90 and the Ham 70cm band. Personally I’m more interested in seeing the FCC to allow some form of digital voice to be used. I think people favor DMR. If they allow NXDN my NX-300’s are already certified for Part 95A. I can use them on GMRS FM currently. https://comms.kenwood.com/common/pdf/download/301_NX200-300.pdf NX-300 FCC Grant - 1.pdf

Ham radio in general is more permissive in what technologies are used for communications. The principal limitation is on bandwidth, transmissions have to fit into allowed emission masks. Also you can’t use codes or encryption meant to obscure or hide the contents of the communications. There is an exception for satellite control ground stations for obvious reasons. The recent rule changes for GMRS in 2017, effective in 2018, encryption is now prohibited on GMRS, including the old voice inversion methods. You’ll likely find this on the older, pre rule change, radios but can no longer be used. So even though modes such as NXDN on Ham, for example, are proprietary they are “published” so anyone can receive the signals and don’t count as encryption thus legal to use. The same would apply to many other signaling systems currently in use. If one wants to design a new signaling system, fine, but the technical details have to be publicly available to any interested party. On GMRS you can use modes other than FM. There are several that are permitted, such as SSB, J3E. Not likely to encounter that one but it is listed as a legal mode. https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95/subpart-E/section-95.1771 https://repeater-builder.com/tech-info/pdfs/fcc-emissions.pdf So I would recommend looking over the rules to see EXACTLY what is permitted first, then examine if a particular mode/signaling system is allowed per the FCC emission masks. Then decide if its an allowed emission does it fall under the prohibition of “codes” meant to hide or obscure the communications.