OldRadioGuy
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Posts posted by OldRadioGuy
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It's very easy to make a mobile type antenna with low SWR at these frequencies where no "tricks" are needed to make the antenna shorter (as you would need the 80M ham band.) So it is very suspicious that you have such a lousy SWR. All of my Ham 70cm antennas do better than your SWR's on my GMRS radios. Usually about 1.5 or less.
It's also odd that the radio mfg requires an SWR lower than 1.5:1. This means less than 4% reflected power which is very small. Even a 2:1 SWR is only 11% reflected power which is not very much. What is their problem???
GMRS is limited to 50W and 10% reflected power is not something most engineers would worry about at these power levels. A 1.5:1 on a portable radio seems ridiculous and unnecessary.... but should be very achievable on a mobile antenna.
I would check your connectors but also your SWR meter. Did you test the meter with a dummy load? Something's not right.
Vince.
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I have both the Nagoya 771 and the Smiley super stick (and the stock 805G rubber duck). The Nagoya 771 and the Smiley (fully extended) seem to perform about the same and both are significantly better than the stock antenna. I think the Smiley retracted is at least as good as the rubber duck.
As for the range of your 905G... There are lots of metal foils (on insulation and foil backed drywall) and "see through" metal coatings on glass used in commercial buildings and high rise apartments. Texas has a lot of intense sun and hot weather so many windows will have the metal coatings. These will just eliminate your GMRS signal. So I would not judge the radio by that.
Take the radios outside and test them. Even our cheap FRS radios will do a mile... and that was inside the car with no external antenna. Terrain and metal surfaces are your two worse enemies.
Vince
- TOM47 and fillmoreranger
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I was thinking "no way" but then I accidentallyfound what looks like the adapter you need on Amazon. The link is too long so here is the exact title on amazon. If you copy and past the title into the search bar you should find it.
Mcbazel Surecom S216 3/8'-24 to SO239 Heavy Duty Stud Antenna Mount Adaptor
I think you will need to chech your SWR because the adapter may affect it.
Vince
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We have a Uniden VHF with FRS.
Maybe they still make these since FRS does not require a license.
The VHF in ours works pretty well but we've never tried the FRS band on them.
Vince
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Lots of people like the Surecom SW-33 SWR Mk2 meter avail on Amazon. It's about $40.
It certainly can be used with an HT (Walkie Talkie) as long as you have the correct cables. I use my MFJ meter with HT's all the time and it works fine. Just make sure the power range is appropriate for whatever radio you intend to use in your test. You do not have to test the antenna with the same radio you want to use it with either.
Testing a portable antenna (like a rubber duck) is a little tricky because the ground is not well defined and the meter itself can impact that. But usually portable ants aren't tunable anyway so why bother. With HT's and portable (radio mounted) antennas your body is actually part of the ground system.
The main reason CB meters are so cheap is that they make so many of them. They're a commodity. Some day GMRS meters may also be that cheap but I suspect most GMRS users do not test their antennas and just use it out of the box.
Vince
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Our ham club discusses GMRS often and even has a GMRS repeater.
Several reasons.
1 Radio is radio and we like them all.
2 It gets people interested in ham
3 The whole family can use it.
4 The whole family can use it.
5 The whole family can use it.
Vince
- mbrun and AdmiralCochrane
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The best way to get started in Ham is to join a local club. NE Ohio has several clubs to pick from. Of course covid has thrown a wrench into these things for now. Not much we can do about that. Maybe some clubs are offering zoom type classes on the internet. You'll have to explore the current options.
Vince
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The online path analysis software scadacore.com shows that this was likely a "line of sight" path.
So no surprise that it would work just fine. UHF works very efficiently over any direct path.
I did experience "ducting" once on VHF and it can be amazing. I had moved to my new house in southern NH and tried the TV on rabbit ears to make sure I could still get Boston and Manchester TV.... but I also got Burlington VT clear as day. I was amazed....But the next day it was completely gone. Just a fluke thing. It was late November so not sure what actual conditions were at play.
Vince
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You do have to be careful with a telescoping antenna fully extended but I've never had a problem. I keep it retracted most of the time until I really need a better signal.
Of course you have to consider your own situation. That's why I also have the Nagoya 771 antennas. I choose what's best for each situation.
But the Smiley telescoping wins 80-90% of the time. It just works good for me.
Vince
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I have tested several of my 70cm ham antennas on my GMRS and the SWR looks fine on all of them. Under 2:1 in all cases and usually about 1.5 which is just fine. Most of them are dual band 2m/70cm. Many of the ham antennas are dual band so this gives you a lot to choose from.
Since 465MHz is a shorter wavelength than the ham 70cm you probably could trim the antenna down very slightly to improve SWR but you'd want to be very careful and use a very short coax with a good SWR meter for your testing. I do not see the need for this. You only lose about 10% of your power or .5dB with a 2:1 SWR.
There is a huge selection of 70cm ham antennas so it really is a nice option to have.
Vince
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Being able to change the antenna is the best thing about GMRS - over FRS.
I like the Smiley Super Stick 465MHz telescoping antenna. https://www.smileyantenna.com/product-p/46510.htm
It can be used either fully retracted (about 5") or fully extended at about 17" and a lot more gain. The lengths are incorrectly stated on their website. It is NOT 48" fully extended.
So you can keep it compact most of the time and just pull it out when you need more gain. I also have the Nagoya 771 and the performance (extended) is comparable but I like that the Smiley can be made compact and still work as good or better than the rubber duck.
Be sure and check for the proper connector selection here. https://www.smileyantenna.com/Articles.asp?ID=253
I have a ham radio 70cm "440MHz" band mag mount that I use in the car. The SWR tests fine on my GMRS.
Vince
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As others have said.....Check your antenna SWR with just a foot or two of coax if you can. Minimal loss coax will show the true SWR of the antenna but higher loss coax will hide a bad SWR. It can make a bad antenna "look" good (but not work good)
If the SWR looks worse with longer or higher loss coax you probably have a connector problem... or the coax is not 50 ohms.
Vince
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Another good alternative to the Nagoya is the Smiley super Stick 465MHz telescoping antenna.
https://bettersaferadio.com/smiley-antenna-super-stick-iv-465mhz-gmrs-noaa-sma-m/
It can be used fully collapsed at just under 5" or extended to 17" to become a 5/8 wave. It is very comparable to the Nagoya when extended (I have both). When collapsed it is still better than a rubber duck and very compact. It only takes 1 second to extend or retract it. It can be very convenient and it's the antenna I use most often.
You can also buy these direct from Smiley. Their website did have the extended length incorrectly stated. Not sure if they fixed that. The correct extended length is about 17".
Vince
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You could use some heavier, lower loss coax for the middle section of the run where flexibility is not an issue.
Keep the thinner more flexible coax for a few feet at the ends where you need it more flexible.
This will keep your overall loss lower without make it unwieldy.
I would try to limit coax loss to around 3db if you can. Lower is of course better.
Vince
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Seems like you could just use your 440 MHz / 70cm ham antenna with a coax switch.
I've tested several of my hamband UHF antennas on GMRS and all seem to match up well enough.
Vince
- WRMH343 and AdmiralCochrane
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Are you mostly interested in the repeater for social reasons or to extend your range for necessary comms?
If you are just interested in the social aspect of the repeater you may find that the internet would have some alternatives. I have found most GMRS repeaters are pretty quiet. Some ham repeaters are pretty busy but many are pretty quiet too.
Ham radio has many more repeaters so you would likely be able to reach one of them. See repeaterbook.com for listings. The repeaters are often operated by radio clubs. You might want to check out joining one of these clubs. Most clubs will allow you to join if you are making some kind of reasonable effort to get a license. They will often have classes to help you get a license too.
Vince
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On most radios it's easy to turn off but.....
Our Cobra PX880 FRS radios do not allow the roger beep to be turned off. You're stuck with it.
I couldn't believe there was no menu setting for it. I guess they figured lots of people like it.... or they're idiots.
Vince
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I took my Ham 2M radio on a plane once and even got permission to use it in the air. But that was before 9/11. Not sure I'd try it today. I'd just put a pair of cheap FRS radios in the checked luggage. I wonder if they would ask you to demonstrate that the radio works. They were doing this at one time but I'm pretty sure they don't anymore.
It's pretty fun to take an FM broadcast radio up in a plane. You get stations from ALL over. Every click has a station.
Vince
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When we moved we just used a pair of decent FRS radios and they worked quite well.
The key is to keep the truck behind the car because the car has a back window but the truck has a metal "wall" behind the cab. I guess some trucks have a fiberglass box but not too many. Most people would instinctively put the truck in front but that's backwards for radio purposes. Better to have reliable communication than to be able to see it.
Even if you get a mobile radio you can not put a mag mount on top of the truck box which is probably aluminum. So you'll still have a problem there.
Wouxun KG805G GMRS hand held radios can connect to external antennas and also can be used with a speaker mic. So that's sort of an in between option. That's what we use now when we take the camper van and the car. We put a mag mount on the van since is does not have a lot of windows.
Vince
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One of my KG805's has a spec of "dandruff" right in the middle of the display window. It doesn't actually hurt anything but it's annoying as heck. I guess at least it gives us a way to tell the radios apart.
I think if I could just open up the radio maybe I could use compressed air to blow it out of there. I would not want to risk harming the radio though. If it opens up easily I'll try it.
Has anyone out there opened up their KG805? I have good tools but I know a lot of these cases snap together and do not come apart without getting beat up. I do not want to rat up the case just to clean the display window.
Vince
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I really wonder how much earth grounding means at UHF frequencies like 460Mhz. The wavelength is nominally 25". On a smith chart you can see than an open looks like a short at 1/4 wavelength away. Basically, impedances invert every 1/4 wave which is half way around the chart. (This is real too) So what does a ground look like 3.632 or and random number of wavelengths away???? It's just a bunch of wire hanging out there. Probably doesn't matter what it's connected to.
Of course, a ground wire is not a transmission line either. It's just wire. But it certainly has a velocity factor or 1 or less. So same rules apply.
I'm not convinced that grounding is a big deal when the ground wire is several random wavelengths long. At 80 meters it's a no brainer. A 6' ground wire looks like a pretty good ground. Of course our HT's work pretty well without much of any external ground at all. For 60Hz power purposes the ground may serve a function. You don't want your radio "bouncing around" at 60Hz or maybe even 750KHz from a nearby AM radio station. But I think the outlet ground will take care of that.
Between pieces of equipment it is of course good to have a solid power ground so those currents don't use the coax as a return.
Vince
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We should also be worried that cheap Li Ion batter packs do not have proper safety circuits built into the pack. That vast majority of (legitimate) Li-Ion powered products require the safety circuits to be built into the battery pack. If the battery pack has a legitimate CE mark it probably does. But with all the counterfeit stuff you can't trust the label either. They may have not safety circuit at all. (BTW, this does not apply to NiCad batts)
I've had a lot of bad experiences with off-brand Li-Ion camera batteries either not charging fully or not holding charge at all. Being very small batteries, they are less of a fire safety risk - but still a risk. Now I buy only major brands, if not the camera brand.
Vince
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Just remember that higher cable loss results in BETTER SWR.... (but not better radio performance). I do not necessarily think this is what's going on in this particular situation though.... unless something is really wrong with the cable itself or a connector is defective.
Minimum return loss is twice the cable loss. So if your cable loss was 3dB your min return loss would be 6dB which means the worst SWR you could ever see is 3:1 even with no antenna at all. (Of course, no mobile install would have such a high coax loss with only 20' of cable.)
You can see this if you just install a 3dB attenuator on the SWR meter with nothing at all attached after it.
Ham guys are often puzzled when they upgrade (a 75' run or whatever) to low loss coax then end up with a worse SWR. The antenna was always a poor match but it was masked by the lossy coax. Of course their radio will actually radiate more power than before with the better coax even with the worse looking SWR. More power reaches the antenna and therefore more power is reflected back.... with the same antenna as before.
Length of coax does not affect SWR at all except for the difference in loss associated with it. It can however affect forward radiated power if your radio output is not a true 50 ohms... and most are not. They are designed to "work into 50 ohms." This does not mean that they "look like 50 ohms" when looking back into the output port. There may be impedances other than 50 ohms which result in better (or worse) power output. I've seen this on my KG805G with a ham radio 70cm antenna and a certain length of coax. The radio will actually put out more than the typical 4-5W with some lengths of coax.
Of course the "wrong" impedance can also cause instability or excess dissipation so you want to operate your radio into something reasonably close to 50 ohms. Any SWR better than 3:1 should be safe though. Many low power hand held or mobile radios would be "safe" into just about any impedance.
Vince
Ground Trailing Wire (aka Rat Tail)
in General Discussion
Posted
Good test and it totally makes sense. There is no such thing as a monopole antenna so having an adequate ground structure is a significant influence.
I have a compact FM broadcast radio and on weak stations you can't put the radio down. It needs your hands on it to receive weak signals.
Vince