Lscott

If anyone is interested in messing around with antenna simulations the software is now freely available. https://www.eznec.com/ I've attached some models I've played around with in the past. Magnet Mount - Rev 2.EZ Magnet Mount Ham and MURS.EZ Ham and GMRS Magnet Mount.EZ GMRS J-Pole Rev 3.EZ GMRS 11 Element Yagi Rev 2.EZ FRS-GMRS Gnd Plane With Radials.EZ 4 Bay Anetnna MURS.EZ

OK. I simulated a simple magnet mount 1/4 wave MURS antenna. The frequency was selected to be about in the middle of the band. The results looks good. The match and radiation pattern look like what I would expect. The exact same antenna was then run at a frequency about in the middle of the GMRS band, between the simplex and repeater input frequencies. As you can see the match short of looks OK on GMRS, however most of the RF power shoots up at a very high angle uselessly into space. I guess if GMRS has satellites in low earth orbit it might be a good antenna. For normal ground work most of the power is wasted. This is what I was getting at in my prior post comments.

For "under the hood" and exposure to weather that's a good idea. On the inside of the passenger cabin, a home setting or a sealed enclosure the power poles are a good idea.

If you look at the photo and the specifications at the link the insertion loss is about 0.1db up to 500MHz for the example switch. That's only about 2.3 percent power loss, basically nothing to worry about. https://diamondantenna.net/cx310a.html

Anderson Power Poles are commonly used. I have just about everything I use outfitted with them. There is sort of a semi official configuration for them. Anderson Powerpoles - Standard for ARES and RACES.pdf ARES - RACES Standard 12 VDC Power Connector.pdf INSERTION - EXTRACTION TOOL FOR PP15-45.pdf

If he does that it will may look OK from an SWR standpoint but the pattern will look bad with multiple lobes likely giving crummy coverage. I wouldn't recommend it other than as an experiment.

You want a coax switch. Be sure you get one that is rated up pass the highest frequency you intend to use. Since you're stuck using SO-239 sockets on it you have to be careful to get the right insulator and socket design type. Most SO-239 sockets for CB radio or HF work may use the crappy red or brown Bakelite insulating material around the center pin. DON'T use those!. These will cause SWR issues. The better choice is when the material is white. That would typically be Delron or Teflon. While better than the above I would only recommend it for VHF and below. The best is where the center pin is supported by what looks like a spoked wheel design around the center pin. That gives the interior of the socket mostly air and results in a socket impedance closer to 50 ohms, matching the radio and coax, which will mitigate SWR problems. https://forums.mygmrs.com/gallery/image/431-coax-switchjpg/

Rumor has it that Anytone is buying Motorola's land mobile radio division too.

And Midland filed for bankruptcy. Production and shipping of all models has been halted.

They are. It depends are what point of view you take. The minimum length for a radiating element used as an antenna is 1/2 wavelength. Obviously a 1/4 wave alone won't work. That's where the ground plane come into play. The easiest way to understand how it functions is place your finger at a right angle against a mirror. You see a reflection of your finger so it looks twice as long. The same thing happens with a ground plane. It "reflects" the 1/4wave element making it look like a 1/2 wavelength long. By bending the radials it changes the feed point impedance so it's closer to 50 ohms, a good match to the 50 ohm coax cable. A true 1/2 wavelength dipole antenna is closer to 70 to 75 ohms with the feed point at the center. That results in an SWR of about 1.5:1, which is perfectly acceptable by just about any radio out there. A 1/2 wavelength antenna is used where a ground plane, or room for radials at the base of a 1/4 wavelength antenna, is not possible. The draw back is the antenna is now twice as tall and the bandwidth is reduced since a special matching section is required at the base of the antenna. Also high gain antennas are multiple sections of 1/4 and 1/2 wave elements with a "phasing" section in between the sections. Those are the small bulges or tiny single loops you see spaced along the length. The down side to high gain antennas is the gain is HIGHLY concentrated in a direction perpendicular to the antenna. Works great for relatively flat open terrain. Not so good in hills or mountainous areas. People who like to hit the trails often carry two antennas. A high gain one, these antennas can be rather tall, used when on the highway and a low gain, usually a 1/4 wavelength, when hitting the trails. https://forums.mygmrs.com/gallery/image/259-ca-2x4mb-jeepjpg/?context=new https://forums.mygmrs.com/gallery/image/268-ca-2x4sr/?context=new https://forums.mygmrs.com/gallery/image/338-cheap-14-wave-gmrs-antenna/?context=new

For a J-Pole type antenna a coax line choke at the base of the antenna is HIGHLY recommended.

Your comments about signal penetration is generally true. The 2M band is popular for general communications. It’s other advantage is Hams are the primary users and enjoys worldwide allocation, typically 144 to 146 and 144 to 148, depending on country and zone. The Ham 70cm band, at least in the US, is allocated frequencies from 420 to 450. There are some reductions in spectrum when close to the Canadian border. Due to the large spectrum allowed you find various experimental modes being used. Also most of the digital voice activity is on this band.

Oh-oh. The recommendations just changed. That’s an VERY important point. For safety reasons, fire and explosion, you would be well off to get what are called “intrinsically safe” radios. This might actually be a requirement for your work environment! They are specially fitted normal commercial grades radios but have been specifically sealed to prevent any arcing or sparking from the radio’s internals which can precipitate a gas explosion or fire. The same also applies to the battery packs, external speaker microphones etc. If you look in the Kenwood catalog they do sell that type of radio for the models I recommend along with the safety rated battery packs.

Kenwood offers some very good radios for a reasonable cost. For rugged outdoors use as you mentioned a public safety grade radio is a must. I would recommend the VHF models in the attached brochures. You will need the software and license for them. To add some of the digital voice modes to the higher end models requires additional licenses. The NX-5000 series is the only one that can do three digital voice modes, two at a time, NXDN, DMR and P25. The licenses for the first two are really cheap, about $42 each. The P25 license is very expensive and typically used by government agencies and first responders like police and fire. If you don't need P25 then the somewhat cheaper NX-3000 series hand held might work for you. The cheapest option is the NX-1000 series. They are good radios but aren't really public safety grade. Encryption options are available for some of the digital modes if required. The attached catalog has all of the options listed and the current "list" price. You may qualify for a discount if you're a local, state or federal government agency etc. Kenwood Land Mobile Radio Guide 2024.pdf NX-5200_5300_5400.pdf NX-5700, 5800, 5900.pdf NX-3200_3300.pdf NX-1200_1300 Num 1.pdf NX-1700_1800.pdf

How have you got your radio programmed up?

Despite the government's denials, a cell phone kill switch, I'm sure in the case of some "domestic disturbance" cell phone use would be restricted or disabled completely by their order. After J6 if it didn't exist then I'll bet it does now. That's when you're likely to need your radio the most to coordinate with others to get out of an area to a safe place.

I've tried installing my own connectors, wasn't easy, didn't turn out that well. Unless you've done a lot of it, and have the right tools, it's money well spent to just buy a cable with the connectors already installed. One less question mark if things don't work as planed.

For a db or two that's true for most people. With a modest gain antenna the coax loses can be compensated for. For people on the very fringe of a coverage zone every db counts.

You have to be careful about which models to get. For example the Kenwood TK-3180's come in two different band splits. Both will cover GMRS, but only one has Part 95A certification. The 450-520 MHz band split can be "pushed", enter out of band frequencies with a warning message, down below 450 MHz to get into the repeater section of the Ham 70cm band. https://forums.mygmrs.com/gallery/image/417-tk-2180jpg/?context=new Some radios, like the Motorola's, the frequency range is locked to the official one and out of band frequencies can't be entered like with the Kenwood's. You have to buy the correct band split version. Also they may not have Part 95 certification either. https://forums.mygmrs.com/gallery/image/261-motorola-xpr6550jpeg/ For example while the Motorola XPR6550 is a nice radio it's not FCC Part 95 certified. TK-3180 FCC Grant-2.pdf TK-3180 FCC Grant-1.pdf TK-2180_3180 Brochure-2.pdf XPR6550 FCC Grant 4.pdf XPR6550 FCC Grant 3.pdf XPR6550 FCC Grant 2.pdf

I think LMR600 has lower loses, a bit larger than LMR400, and I think it's not much more expensive either. The loss at 450MHz for LMR400 is 2.7db/100 feet. The loss at 450MHz for LMR600 is 1.7db/100 feet. For somebody who needs to run between 50 to 100 feed of coax stepping up to LMR600 would makes sense. The chart frequency of 450MHz is close enough to GMRS at 462/467 MHz the extra loss at the slightly higher frequency isn't that significant. For 50 feet of LMR400 at 450 MHz the power loss would be about 27%. For 50 feet of LMR600 at 450 MHz the power loss would be about 18%.

At a reasonable cost. There is better cable, various types of "hard line", but gets expensive real fast.

I’ll have to check that one out. Every once in a while I get asked about it.

I was under the impression they all required a ground plane. https://forums.mygmrs.com/gallery/image/428-stealth-dual-band-with-swr-scanjpg/