Good TX but no RX on VHF/MURS mobile antennas

[Amclark]

Hello, I've been tinkering with MURS radios and have been looking for a simple mag-mounted mobile antenna. I've run into an RX performance problem on everything I've tried so far.

I tested 2 different Nagoya UT72 antennas which are supposed to work great with MURS (~152-155mhz.) These are 1/4 wave at VHF, coil loaded at the base and about 20" tall. I measured both antennas below 1.5 SWR and there were no apparent problems with the coax. These did increase transmit range but actually reduced reception range significantly... To the point where the stock rubber duckies inside the car have 5 times the RX range as when connected to the antenna on the roof of the car. I tested this with 3 different models of MURS radios and RX with a UV5r set to the same frequency. They all did the same thing. Also tried multiple vehicles, different positions on the roof, and different pigtail attachments to the radios with no luck.

I just tested another cheap-o mag mount UHF/VHF antenna that is a similar size to the UT72, but a different design at the base. It did the same thing.

The local NOAA channel (162.400mhz) had the same issue when connected to any of these antennas. Often no reception even though the signal was strong enough to be picked up with no antenna connected to the radio (even without a rubber ducky.)

Any ideas what would be causing this? I was really hoping to find a workable compact dual band antenna in case I ever want to get into GMRS. But would be open to trying something longer and/or dedicated to VHF instead.

Thanks for any input.

 

[kny2xb]

I personally haven't experienced this, BUT:

Other ops have said that the UV5Rs & other CCRs have poor/unfiltered front-ends,
& that using a better antenna overloads the receiver

I would get a better MURS radio, & a dedicated VHF antenna

I can throw some ideas out there, but I don't know what your budget is

 

[mmckenna]

It sort of sounds like something is overloading the receiver. If you have strong signals nearby, that may be enough to overload the front end on the radio and impact performance. Switching to the stock antenna reduces the amount of overload.

Which brand/model radios are you using? As stated above, Baofeng and the other Cheap Chinese Radios tend to have minimal filtering on them and will overload easily in high RF environments.

 

[alcahuete]

What KNY2XB said is completely accurate. Baofengs have a lot of issues with the receiver being overloaded, especially when using an external antenna. Is that what is happening here? Don't know.

First things first, buy yourself a mag mount with NMO. That opens you up to a world of actual good antennas instead of Chinese crap.

https://www.theantennafarm.com/catalog/index.php?main_page=index&cPath=191_192_200_451_220

https://www.theantennafarm.com/catalog/index.php?main_page=index&cPath=191_192_200_451_219

Look at the Larsen and Laird antennas. They throw some tri-band antennas in there as well, which can be ignored. Those are quality commercial antennas that will cover MURS and GMRS.

 

[prcguy]

This is exactly what happens when I use a UV5R with an external antenna. The fix is get a higher quality radio as it would cost a ton of $$ to buy filters to make a $25 radio play nice with an external antenna.

Hello, I've been tinkering with MURS radios and have been looking for a simple mag-mounted mobile antenna. I've run into an RX performance problem on everything I've tried so far.

I tested 2 different Nagoya UT72 antennas which are supposed to work great with MURS (~152-155mhz.) These are 1/4 wave at VHF, coil loaded at the base and about 20" tall. I measured both antennas below 1.5 SWR and there were no apparent problems with the coax. These did increase transmit range but actually reduced reception range significantly... To the point where the stock rubber duckies inside the car have 5 times the RX range as when connected to the antenna on the roof of the car. I tested this with 3 different models of MURS radios and RX with a UV5r set to the same frequency. They all did the same thing. Also tried multiple vehicles, different positions on the roof, and different pigtail attachments to the radios with no luck.

I just tested another cheap-o mag mount UHF/VHF antenna that is a similar size to the UT72, but a different design at the base. It did the same thing.

The local NOAA channel (162.400mhz) had the same issue when connected to any of these antennas. Often no reception even though the signal was strong enough to be picked up with no antenna connected to the radio (even without a rubber ducky.)

Any ideas what would be causing this? I was really hoping to find a workable compact dual band antenna in case I ever want to get into GMRS. But would be open to trying something longer and/or dedicated to VHF instead.

Thanks for any input.

 

[mmckenna]

If you are really interested in MURS, you can get better radios.

NT Series, MURS/VHF/UHF, Ritron 2-Way Radios

The NT Series is a full-featured, lightweight and compact analog portable 2-way radio. Tough and reliable - certified to Mil-Standard 810F and IP65 rating. Ideal for basic job site applications to in-plant repeater systems and selective signaling applications.

www.ritron.com

NT-152M is probably one of the nicest MURS radios out there. My brother in law had a bunch of them he used with his tower crews. That put them very close to high power transmitters, and he never had any issues.

Icom has some that are new to the market. Haven't heard any feedback on them, but Icom is a reputable company that makes good commercial/public safety radios:

V10MR Multi-Use Radio Service (MURS) Transceiver - Features - Icom America

www.icomamerica.com

Same for GMRS, if your interests go that way, steer clear of the Cheap Chinese Radios. If you're having issues on MURS, it's likely you'll have similar issues with the Baofengs on GMRS

 

[Amclark]

Thanks for the responses everyone. I have been primarily using the Btech MURS-1 and Retevis rt47v before that. I also have the dakota digital M538-bs, which I haven't tested on the third mag antenna yet. I'll give that a try tomorrow.

The receiver overload certainly sounds plausible. If that's the case though, one thing that doesn't make sense is that all of these radios performed great on my antenna at home which is an Ed Fong DBJ-1 (commerical) mounted on the roof ~30 above ground. If it's an issue of noisy environment/cheap radios, I would think this antenna would be even more likely to overload the receivers. But it has received well from the mobile units at ranges that seem right for this frequency (5+ miles.) The mobile antenna doesn't receive much past 1 mile.

I might go the NMO mag mount route. This would open up a ton of options.

 

[chief21]

The mobile antenna doesn't receive much past 1 mile.

The source of the offending signal could be the vehicle itself. Lots of "unintentional radiators" in many cars these days. Try the antenna away from the car or on another vehicle and see if there is any improvement.

 

[Amclark]

Hey guys, I did a bit more testing and the "CCR" receiver overload theory definitely seems to be valid. 2 different UV5Rs are consistently terrible RX on the mobile antenna. They're also worse RX on the base antenna than the other radios (although still somewhat usable with that.) Taking the UV5Rs out of the mix for testing also helped to identify a bad pigtail that was hurting reception as well. (UV5r still bad with a good pigtail.) Overall the BTECH MURS V1 is the most consistent performing unit with dakota digital radios coming in behind that.

I don't have the UT72 antennas or the Retevis RT47v radios anymore, so can't retest those. But the BTECH seems to be working fine with the "Bingfu" dual band mag mount. Still need to do some more long range testing though.

I also have an NMO mag mount and VHF 1/4 wave antenna on the way so I'm curious how this will perform. Will post back if there are any interesting findings.

Thanks again for the input everyone!

 

[JoshuaHufford]

I have a pair of the BTECH MURS V1 radios and have not experienced any overload problems using external antennas on the vehicle. Last time the radios were in use I had a 1/4 wave cut for 152-162MHz on a permanent NMO mount on my vehicle and the same antenna on a mag mount on my friends, we could get a couple of miles range with no problems.