dosw

HHD1 · Thursday at 04:20 PM

Amateur radio spans almost the entirety of the RF spectrum, and LW, MW, and HF propagation are vastly different from VHF, UHF, and other much higher frequency band propagation.

GMRS uses 65cm, which is very close to amateur 70cm. For those, propagation will be virtually identical; UHF 70cm and UHF 65cm GMRS will be identical.

GMRS doesn't extend into VHF. Amateur radio has bands in 2m and 6m that can be described as VHF. VHF requires bigger antennas than UHF for similar gain characteristics. VHF suffers less from attenuation by foliage. But UHF is a little better at getting through walls. Both are "line of sight."

Amateur offers 10m (a lot like CB propagation -- pretty long range during periods of high sunspot activity, line of sight at other times).

Amateur offers 20m, 40m, 80m, 160m. These are the bands people use to talk all over the world, but they're subject to seasonal changes, day/night changes, sunspot activity, and so on. They achieve these long distances by bouncing the radio waves off the ionosphere -- layers in our atmosphere. Requires knowledge and good technique for knowing when to use which band. Very large antennas are common, and high power levels. Not entirely reliable.

You're probably asking about 2m/70cm amateur vs GMRS. And again, there, 70cm vs GMRS there's no practical propagation difference. 2m vs GMRS there can be some advantages to 2m if you have comparable gain antennas, which will be bigger. But the advantages are subtle.

The fine print: I skipped over the following amateur bands: 1.25m, which is less used, but close in propagation to 2m. I skipped 900MHz and GHz bands because they're uncommon for simplex over any distance. And I skipped LW/MW, as well as 17m, 15m, and 12m amateur. 17,15,12 are going to share characteristics of 10m and 20m, but are less common bands. LW and MW require much larger equipment and are relatively niche bands. 160m is pretty close to MW though. I also skipped over MURS, because its power requirements are more limited, despite propagation being similar to 2m. 30m is useful in the same way that 20 and 40m are useful, but less common. And 60m is relatively niche. I skipped CB because at 11m, its propagation is similar to 10m, but it's a dumpster fire of crazy traffic. However, people do use CB. It's limited to 4w for AM transmissions, and 12w for SSB transmissions.

May 8

3 hours ago, WSGC728 said:

I have had good luck with my Retevis RA87. According to my SWR meter, it pulls a steady 1.0-1.1 SWR reading & anywhere between 40-45 watts of power with a Larson magnetic mount antenna. It also pulls the same SWR & wattage on a dummy load.

SWR is the Standing Wave Ratio, and is a function of your antenna, cabling, connectors, antenna mount, ground plane effectiveness, and environment. As power is reflected back into the radio rather than efficiently disappating it in the form of RF output, the reflection back into your radio is the standing wave. This is a bit of an oversimplification, but accurate enough to explain that if you see a higher SWR your radio is usually the last place to look, the last thing to blame. And into a dummy load -- it would be a terrible dummy load if it were reflecting power back into the radio. Their purpose is to absorb power with the proper ohm load to avoid elevated SWR that could damage the radio.

Anyway, the RA87 has been very reliable for me over the past year or so. Unfortunately it fits in great with the utilitarian interior of my old Bronco, but not as well with the cushy interior of my newer F150. I'll probably go with something with a remote faceplate if I can figure out where i want to mount it, and how to route the antenna cable in this newer truck. In the old Bronco a few visible wires and a big radio under the dash just ads character.

May 6

Confirming:

You hear them but they don't hear you, and you don't hear the kerchunk when you key up the repeater?

How are you verifying they can't hear you? Is it by asking for a radio check while you know people are active? Or are you listening for the kerchunk on the radio you transmitted with? Or do you have two radios in close proximity, one to transmit and one to listen?

Different troubleshooting tactics apply to each.

WRTC928 · May 1

The GMRS version of the 5RM series is the UV-5G Plus.

Type-approval aside, the 5RM variants (with the exception of the UV-5G Plus) cannot be set to power levels below about 2w. That makes them incapable of meeting the technical requirements for operating on GMRS/FRS channels 8-14, since those channels are supposed to be constrained to 0.5w or less. Aside from that they can be correctly configured for 1-7 and 15-22, though they would still not be type-approved, so still in violation of the FCC rules, which not even the FCC has enforced against individuals historically. It would be impossible to distinguish a 5RM series configured technically correctly on channels 1-7 and 15-22 from a UV-5G Plus. Nobody could tell the difference. And on 8-14 it would be hard to know, though transmitting at 2w when you're supposed to stay under 0.5w is more likely to interfere with nearby repeater mains, so not a good practice.

If there is now a 5RM GMRS variant, that is probably going to be something very similar to the UV-5G Plus. And it may even be a type-approved radio. You could look it up in the FCC filing but it's a lot of work to find, and ultimately not worth the bother.

SteveShannon · April 30

This is a topic you could search for hours on and not come up with a clearly definitive answer. In fact, there's almost no argument, even. The advantages and disadvantages of each are so minor people don't really seem to be all that passionate about it.

CTCSS will behave with older equipment that doesn't support DCS. But who are we protecting? There aren't a lot of people operating 20 year old blister pack GMRS radios lacking DCS support on repeaters. Both are subaudable tones or sequences that have to be filtered out by the radio's high pass filter. Both have different reasons for behaving a little oddly at fringe-reception areas. DCS *may* take a little longer for the sequence to be transmitted completely enough for a radio to open squelch, but we're talking tenths of a second at most. CTCSS may be a little more crowded (you may have a slightly harder time finding a channel and tone pair that isn't in use).

But the fact that we have both systems really is a product of the evolution of marketing bullet points from vendors. One or more vendors claimed they had a new and improved system, and they pushed it to the point that it gained adoption. But the fact that DCS and CTCSS have continued to co-exist for decades, filling the exact same purpose, without a clear winner pushing the other out of the way kind of indicates there's not a clear winner.

April 29

4 hours ago, WRYZ926 said:

GMRS repeaters are going to have the same coverage area and range as 70cm repeaters when antenna height and locations are equal.

We get 30-35 mile radius of coverage with our GMRS repeater antennas at 400 feet and 35-40 mile radius of coverage with our 70cm antennas at 900 feet. Both are on the same tower. And both 70cm and GMRS has the same dead spots when one is mobile.

GMRS repeaters have the same exact propagation characteristics as 70cm. I'm aware of this as you are. But 70cm doesn't have a prohibition against linking. The point I was making was that it's possible the OP was hearing a 70cm repeater that was legally linked -- a very common practice -- as opposed to hearing a GMRS repeater that is illegitimately linked -- a much less common practice nowadays.

April 29

Are you sure you were listening on GMRS frequencies? Could the radio have been set to pick up 70cm amateur? It's a lot more common to find repeater networks in the amateur bands. It still happens in GMRS despite the FCC clarification. But if you were picking up 70cm amateur it would be less surprising.

OffRoaderX · April 23

4 hours ago, Socalgmrs said:

Nope. Never heard of a dummy antenna. Dummy load? Yes. Dummy antenna? Nope. Another question that could have been answered by a quick internet search.

We all value knowledge and experience here, but the way you're treating newcomers is out of line. Everyone starts somewhere, and being dismissive, impatient, or outright rude doesn't make you look more knowledgeable—it just makes this community less welcoming.

If your goal is to actually help people learn and grow, then your attitude needs to reflect that. Otherwise, you're not building anything—you're just gatekeeping. You were new once too. Try to remember that.

April 23

Just following up with a few pictures and thoughts:

1R-TZx2sXZtB5VeoNzVYUUdh537kbVpeM

1R4AwUegDgP7ah-gv4selGUVxdnPf5BFR

1QvOYWltKxpcItGcxLZCTJskw-9aolGER

One is the old Bronco with an MXTA26 antenna. Inside is an RA-87 mounted under the driver's side console above the driver's right knee. Plenty of room there.

The other two are the newer F150. It's in pretty good shape, so I'm a little reluctant to make an amateurish attempt at routing wiring through the headliner to set up a rooftop drilled-through NMO mount. Yet that's probably the best option. I'm thinking I might get in touch with an audio installer and let them go at it. I think the roof is probably my best option, though as you can see from the picture I have a sun roof, and I'm not sure how far back the window equipment goes. Thus I don't know how far back I'll have to put the NMO mount to be out of the way while still having some ground plane available.

Inside, things are pretty tight. I like the idea of putting a radio under the center console, and then running the head unit up to the sunglass holder overhead, OR to a seat mounted bracket.

WRUU653 · April 23

13 hours ago, The219 said:

yes but its not clearly written and I was not able to find much as far as setting for the RA87 online. some reviews here and there and some tutorials on how to set two up as a repeater but not much else.

@WSHM765 Press the "FUN" button on the face then the "MHZ" button on the face and scroll to "MDF" its "menu #16" press the "MHZ" button on the face again turn the dial to"MN" then press the the "MHZ" button on the face to lock it in. you have to do it to both "sides" of the display.

Yeah, the radio doesn't get the love that some of the Wouxuns and other fairly popular models get. But it's really pretty solid. Very close to the full 40w across the GMRS range (within, say, 5% in my most recent testing). Good sound quality. I kind of wish that it had more than six character channel labels. I like the "left" and "right" side option; I set the left up for scanning repeaters, and set the right up for the channels my family is most likely to use, as well as for open scanning. Signal reports are favorable, though that has a lot to do with the antenna and geography.

It has some quirks. From the front panel you can only swap between low and high power. But within chirp there are five power options. I usually set "medium" power in the programming using Chirp, knowing that I can push the power button to get to high if I need it, for example. But I've been using it about a year now in my dusty old Bronco and it has held up great.

April 22

1 hour ago, WRTC928 said:

I really like the 5RM (AR-5RM, UV-5RM). It has all the features I would ask for in an entry-level HT. As much power as is practical in an HT, 3 power level selections, 3 bands tx/rx, airband and NOAA rx, USB charging, and it uses accessories which are robustly supported. IMO, the UV-5r is too small to manipulate easily, but the 5RM is a good size and it feels solid in the hand. In fact, I don't have any significant complaints about it. I have a couple of spares unopened, but so far, neither of my "regular use" 5RMs have shown any sign of quitting. I invariably get signal reports of full quieting on repeaters. Some users have reported that they get poor audio output quality, but I haven't experienced that. It doesn't do digital modes, and I'll want that eventually, which is why I describe it as an "entry-level" radio, but that isn't a factor on GMRS and it may be all the HT radio you ever need for simplex and GMRS usage. It remains to be seen how well it will hold up over time, but it was so inexpensive that I bought spares, so I'm not too concerned about that.

The things that could be better on the 5RM:

It's a little on the large size, particularly when compared to the tiny UV5R.
It doesn't have a squelch knob as higher end models often have.
It's not weatherproof, but it's so cheap it probably doesn't really matter.
It doesn't allow for dividing the 999 channels into scan-banks, as some higher end models allow.
The lowest power setting is about 2.2w, which exceeds the power limits of some bands it wasn't explicitly designed to work with (GMRS channels 8-14 are max 0.5w. MURS is max 2.0w). Of course it's not made for those frequencies; it's a ham radio. But people often do use it for those bands.
The display is rather hard to read in bright daylight.
Some of the menus and secondary functions of the number-pad buttons are counter-intuitive or even mislabeled.

However, for approximately $30, it's the best radio I'm aware of. Models that are substantially better tend to cost substantially more. It's my most frequently used handheld.

OffRoaderX · April 15

3 hours ago, Alec said:

@WSEZ864 Thanks for the suggestion about the back rack, and for the photo! Very helpful. That is certainly an interesting option worthy of consideration.

@WRUU653 Thanks for the A-Pillar suggestion. I do understand compromises...

Cost isn't a primary consideration for me, but even so the 3rd tail-light mount is in itself sort of a compromise, rather than following the recommendation of the "drill-baby-drill" enthusiasts who advocate for just installing that NMO mount. While an NMO mount installed dead center of the roof of my truck cab might be the best solution for RF purposes, that isn't necessarily the best solution for my purposes.

I've been browsing YouTube videos about removing the headliner as was suggested by @WRUE951 and unless you are someone who does that sort of thing all the time, it appears like it could potentially be a PITA that is not without its own considerations and complications.

In the process, I've also stumbled across a great many videos regarding replacing or fixing a 3rd taillight on these trucks. Some replace it for the purpose of a cargo/5th wheel bed camera, others for brighter or flashing LED lights etc. Many people with many different reasons. However, there are also folks that speak of damaged headliners as a result of leaks from a worn 3rd taillight lens gasket. Many suggest that it is not "IF" it will eventually leak, but rather "WHEN" it will leak, and they advocate replacing the gasket and resealing these 3rd taillight assemblies with silicone as a preventative measure. Something to think about...

Interestingly enough that gets me back to my original post about this type of antenna mount where I asked those with direct experience using these devices: "Do they leak?" I'm thinking of an antenna being pushed by wind or by hitting trees, etc. and wonder how that might contribute to breaking or otherwise compromising that watertight seal around the mount? IOW, if these 3rd taillight assemblies are prone to leaking, maybe introducing an antenna mount there would be inclined to make matters worse.

Absolutely nothing is without compromise!!

Again, thanks for the comments and feedback on the topic.

This is how this thread has gone:

OP: Has anyone tried these?

Others: Those won't have a very good ground plane, and that will hamper your signal propagation.

OP: But this is what I want to do.

Others: *shrug* then why did you ask?

April 15

On 4/14/2025 at 4:38 PM, Alec said:

On my 2018 GMC Sierra pickup truck (w/ a 6' truck bed) the 3rd brake light is very close to being as centered, front-to-back and right-to-left, as you can get. Thus, I don't believe this location sacrifices 180 degrees of ground plane as you suggest. I'm not wanting to direct the radiating pattern in any specific direction. If I'm not understanding your comment here, please explain...

Thanks

You'll maybe need to show a picture demonstrating how an NMO mount on top of the 3rd brake light has a full 360 degree ground plane. Three or four feet below inside the truck bed is not acting as a ground plane. So if that's what you're expecting to consider as your ground plane, no photo needed. It's not doing what you think. Now, it may *work* to have an antenna mounted there. You'll be able to transmit and receive. But your SWR will be a little high, and your propagation in the aft 180 degrees will be relatively lousy.

April 15

I have a new-to-me F150 Lariat with SuperCrew cab. It's a 2014. The front console seems pretty full, though there's a "SYNC" panel at the base of the front panel that may have space behind it; I'm not sure. It's possible I could find room under the seat if I use a detachable faceplate style radio such as a KG1000G Plus (GMRS) or the KG -UV980P (amateur).

I'm looking for examples of successful installations that seem not too intrusive or not to have that "I bolted this thing to my dashboard" look. Additionally, examples of antenna mounting would be useful. I already can't park the truck in the garage, but would prefer not becoming so tall that I also can't pull into commercial or municipal parking garages. On my 95 Bronco a hood lip-mount works great because the cowling aft of the hood is also metal, so I'm able to achieve a good ground plane. But on the F150 the cowling aft of the hood is plastic, so the ground plane would be poor with that type of mount. Cab-top is probably ideal from a functionality standpoint, but a compromise in terms of what kind of antenna I can put up there (it would pretty much be the Ghost, or frequent swapping to accommodate height obstructions).

WRUU653 · March 31

2 hours ago, WSAL818 said:

I'm struggling to correctly set up Retevis RA87 using their software. Can anyone tell me what the Step(KHz) stands for and what the proper value is for the gmrs?

When the radio is set in VFO mode, and you turn the knob on the right, it will move up or down through its frequency range. Step is how far it jumps with each click. If you set up the radio for GMRS, you probably wouldn't use this setting much. But it's there in case you want to move around through the frequencies to listen to things, such as in the 70cm amateur band.

SteveShannon · March 31

On 3/29/2025 at 10:13 AM, SteveShannon said:

People successfully talk to the International Space Station using a five watt handheld on 70 cm. That’s a couple hundred miles.

240m at best, when it passes directly overhead at 17,000 miles per hour. With a decent antenna I start hearing it about 1100 miles away, a little above center frequency, and stop hearing it about 1000 miles away at a slightly lower than center frequency, due to the Doppler shift associated with its speed. It's pretty amazing, really. And it fades in and back out again not because of the miles but because of the curvature of the earth.

Mariners have used line of sight formulas for centuries, of course. RF line of sight formulas are only slightly different from visual.

March 31

On 3/29/2025 at 9:06 AM, WSGH675 said:

I been told that a gmrs handheld can reach line of sight to a repeater ok but there has to be a limit how many miles a gmrs handheld can reach a repeater. I know Hawaii is a long ways away but there is nothing but ocean between West Coast and Hawaii but there has to be a range how far a handheld gmrs radio can reach to a repeater

Line of Sight, explained

You have to account for the fact we live on a spheroid.

March 23

The 701 was nothing special when I had one. 771s are great.

WRYZ926 · March 18

6 hours ago, OffRoaderX said:

Please tell us where we can find a new, 40W, single-case/chassis, weatherproof Motorola repeater with a warranty, and weighs only 4Lbs, for 1/2 the price....

We're waiting....

And it must also have a 200 mile range any time, rain or shine.

March 13

On 3/12/2025 at 7:34 AM, nokones said:

Laird (T E Connectivity) has a 450-470 Meg # TRA4500N non-Groundplane Phantom NMO mount antenna. I use this antenna on my Fiberglass body racecar with excellent results. The antenna also comes in Black, but you have to buy multiple quantities. You can buy the White antenna as a single unit.

This is great information. I have a Ghost antenna (MXTA25) that I don't really use, but this would be ideal for a boat or RV where ground planes are difficult. Laird TE TRA4500N. Thanks for sharing that.

OffRoaderX · March 13

35 minutes ago, OffRoaderX said:

Yes - last night I was trying to look up someone's GMRS callsign that he posted on X so I could DOX him, and I keep getting the same error.

You weren't trying to call your minions in his part of the country to coordinate their burglarizing efforts, since his X post made him obviously not home to defend the place?

SteveShannon · March 13

I have the Surecom SW102, and the NanoVNA.

Advantages to the NanoVNA: You don't just get SWR, you can get an SWR curve showing you where the dip in the curve is, and can identify immediately whether the antenna is too long or too short. With just an SWR meter you have to take multiple samples and plot your own curve. Also the NanoVNA does a LOT more than just SWR.

Advantage of the SW102 - It tells you the power level being transmitted. And it's very simple to use. But for accurate power, and to avoid annoying people you'll need a dummy load, too.

SteveShannon · March 12

5 minutes ago, TrikeRadio said:

You all need to stop rag-chewing and chatting about this subject here on the forums because that is not covered in Part 95 and is not allowed you know.

From The Importance of Being Earnest:

Quote

JACK.
I am sick to death of cleverness. Everybody is clever nowadays. You can’t go anywhere without meeting clever people. The thing has become an absolute public nuisance. I wish to goodness we had a few fools left.

ALGERNON.
We have.

JACK.
I should extremely like to meet them. What do they talk about?

ALGERNON.
The fools? Oh! about the clever people, of course.

JACK.
What fools!

It seems like whether one is a rag chewer on an amateur repeater, or on a GMRS repeater, or a rag chewer here in online forums, we're talking about the ~~fools~~ clever people, of course, which makes us all ~~clever~~ fools.

CaptainSarcastic · March 11

4 minutes ago, CaptainSarcastic said:

Wouldn't it make more sense to make sure your argument is "iron clad" and can hold up in a court, BEFORE suggesting something like this?

Exactly. The people with "skin in the game" are the ones who adopt this. And they're relying on someone's layman theory, not iron clad findings.

WRXB215 · March 11

12 minutes ago, CogentRadios said:

As we all know wording in law is crucial, a ruling is an interpretation of the law and not the actual law or does it carry the same weight, there is the problem, and yes I have discussed this with friends that practice law, not communications law but they believe there is an argument to be made here.

But you're experimenting with other peoples' liability, without an actual legal consultation on the issue, and other associated due diligence. That is irresponsible. And people are justified in being skeptical. People who adopt are trusting your discussion with a friend who practices law not pertaining to communications law, putting themselves at risk.

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