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Static while in motion, roof mag mount

WRVS497

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WRVS497 Apprentice

WRVS497

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Curious if anyone has had this same phenomenon and/or a solution.

I have a Nagoya UT-72G mag mount on the roof of my Tacoma with a Midland MTX275 micro mobile. The Midland is powered off the dash cigarette lighter plug using the stock cable and plug. When parked, my transmit and receive is quiet and other mobiles on the channel/repeater copy loud and clear. As soon as I get going however, any time a transmission comes in I hear consistent popping and static on RX and when I TX, other mobiles say that it sounds a bit staticy and/or "picket fencing". Again this disappears when I stop at a light, etc. 

I have not yet tried ferrite chokes on the power line however I did try one on the antenna cable near the connection to the radio without any change. I do plan on rewiring the power situation with a 12v relay, some 10ga power cable (OFC) and a fused power block as well as grounding the negative cable close to where the radio is mounted. I plan on having additional radios later hence the choice of cable size.

Before I go down the rabbit hole of moving the antenna, replacing the antenna with something more "expensive", or throwing chokes everywhere, has anyone experienced this with their rigs or the UT-72G specifically? Could this be a flaw with the antenna itself or is there additional grounding necessary to counter wind static? If its wind static what is the best way to bleed static off the antenna from a roof mounted position? I assumed the grounding side of the coax would take care of this but maybe I need to ground the connector to the truck frame? Throwing out ideas here.

Thanks in advance for your help and knowledge.

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WRVS497 Apprentice

WRVS497

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I'm definitely considering an NMO setup. Looking into the MXTA26 antenna with the MXTA27 hood lip mount. I've heard good things about Trams but also heard good things about the Nagoya. What is it about the NMO mount that could potentially solve my issue?

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kc4mhh Newbie

kc4mhh

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You are starting out with a poor ground.   By using the auxiliary power connector, you can have voltage drops along with a poor ground that can introduce engine noise from the ignition and alternator.  I definitely recommend a roof mount NMO antenna.   As well as providing a better ground plane for the antenna, which will result in a much better signal, it will greatly reduce induced noise.    A 1/4 wave antenna is ok if you are local to the repeater.   However, if you do a lot of traveling or are far from the repeater, I would use a quality 5/8 wave gain antenna such as the Tram or Larson.     

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gortex2 Veteran

gortex2

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34 minutes ago, WRVS497 said:

I'm definitely considering an NMO setup. Looking into the MXTA26 antenna with the MXTA27 hood lip mount. I've heard good things about Trams but also heard good things about the Nagoya. What is it about the NMO mount that could potentially solve my issue?

No spring. Alot of the cheap springs are part of the RF path. A quality LMR antenna will have a braid inside the spring coil to transfer RF from the mount to the whip.

The Nagoya is a CCR antenna and the only people who praise them know nothing about antenna's. Its normally hams or users who got on amazon and bought them who read how good they are. 

The Midland option is a decent unit from what folks say. Personally all my stuff is from LMR providers and is MSI, Laird or Larsen.

 

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marcspaz Grand Master

marcspaz

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@WRVS497 I would want to hear a recording to see if its at an unusual level, but what you are describing is SOP for mobile operations.  Unless you are within a couple of miles (or closer in many instances) of the repeater or another simplex station, you are going to have static and popping on transmit and receive.

 

Dust and other pollutants can become statically charged when they rub against one another. They collect on the surface of our vehicles and our antennas. Driving can cause dust static. It never goes away until you stop, which is when the static stops.  The perceived loudness usually increases with speed.

 

Also, as you drive, there are 'things' (trees, buildings, hills, even people in some cases) that are moving in an out of the radio path as you drive, changing the receive level of the signal.  Plus, if you have a whip antenna, the wind is moving your antenna all over the place.  That changes the direction or focus of the antenna's receive and transmit pattern/path.  Imagine putting an flashlight on your antenna and going for a ride.  Think about how the light beam would be moving all over the place as the antenna moves.  That is a good, but over exaggerated example, of course.

 

These are just a small sample of what can cause noise while driving... there are many others, including noise generation from your vehicle itself.

 

If you don't hear these things when you are stopped or when you are driving close to the other radio, this is because the signal strength of the desired signals has gotten to the point that they significantly overpowered the random noise signals.

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WRQC527 Mentor

WRQC527

Posted
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I've had a couple of radios do this. A Wouxun HT and a Juentai JT-6188 mobile. Even at walking speed the radios break squelch intermittently. Not when stopped. I attribute it to poor receiver filtering, which is allowing speed or abs sensor signals to break the squelch, since none of my Yaesus or Icoms have the problem. My mobile radios are connected directly to the battery with a noise filter that removes 99% of the alternator whine. 

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WRVS497 Apprentice

WRVS497

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Thanks all for the information! Based on this I'm going to start with the wiring and ensure everything is grounded properly and minimized voltage drop occurs. I hate using cigarette lighter for power anyway, other than charging phones. The coil spring does makes sense. This antenna has a short spring at the bottom so there is potential there for sure. 

@marcspaz Hey I've spoken to you before. I'm on the Warrenton and Bull Run repeaters frequently so if I catch up to you one day we can test it out. I'm typically on ~0630 to ~0730 in the mornings and 1600 to 1800 evenings depending on when we get on the road after work. I also considered all the random stuff in between me and the repeater but when stationary there is rarely any consistent static. In motion its every caller, stationary its only the ones that are far from the repeater and having trouble reaching it.

@WRQC527 can you link me to the noise filter you are using?

@gortex2 Can you link me to some of those LMR antennas as well?

Thanks again

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marcspaz Grand Master

marcspaz

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Posted
36 minutes ago, WRVS497 said:

@marcspaz Hey I've spoken to you before. I'm on the Warrenton and Bull Run repeaters frequently so if I catch up to you one day we can test it out. I'm typically on ~0630 to ~0730 in the mornings and 1600 to 1800 evenings depending on when we get on the road after work. I also considered all the random stuff in between me and the repeater but when stationary there is rarely any consistent static. In motion its every caller, stationary its only the ones that are far from the repeater and having trouble reaching it.

 

I do remember chatting, now that you mention it.  I have to do some work on my Jeep on Saturday, but we can always meet up in Gainesville or Haymarket sometime Saturday or Sunday and check it out.  I can toss some tools, meters, and spare equipment in the truck, too.

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WRVS497 Apprentice

WRVS497

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3 minutes ago, marcspaz said:

 

I do remember chatting, now that you mention it.  I have to do some work on my Jeep on Saturday, but we can always meet up in Gainesville or Haymarket sometime Saturday or Sunday and check it out.  I can toss some tools, meters, and spare equipment in the truck, too.

Much appreciated! let me figure out what I got going on. I don't have any meters yet so it would be interesting to see the SWR, etc. I have gobs of electrical gear and tools as I do all my own mobile sound system work but when it comes to radios I'm totally green. If I don't catch you on the airwaves ill DM you.

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WRVS497 Apprentice

WRVS497

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Wow that DIY filter. who would have thought you could use a regular old link like that. Guess it really is all about the turns.

Thanks again ya'll. Looking at those Lairds I think I'm definitely going to consider those over the midland series. Much appreciated!

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wayoverthere Mentor

wayoverthere

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Posted (edited)
3 hours ago, gortex2 said:

@WRVS497 Here is a good link with many decent LMR units.

https://theantennafarm.com/shop-by-categories/shop-all/mobile-antennas/gmrs-mobile-antennas

Personally I use the Laird BB4503 on a lot of my friends vehicles if the 1/4 wave doesn't work. Its a solid little antenna.

I'll also mention the 'no ground plane' category for jeeps or less than stellar mounting situations...they have some 1/2 waves in the same price range And similar sizes, in black or silver, spring, polymer spring, or no spring.

 

https://theantennafarm.com/shop-by-categories/shop-all/mobile-antennas/300-512-mhz-uhf/no-ground-plane-antennas/3236-laird-connectivity-bb4502ns-detail

https://theantennafarm.com/shop-by-categories/shop-all/mobile-antennas/300-512-mhz-uhf/no-ground-plane-antennas/3231-laird-connectivity-b4502n-detail

 

Edited by wayoverthere
fix 2nd link
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BoxCar Mentor

BoxCar

Posted
Posted
27 minutes ago, WRVR303 said:

Try revving the engine while stationary and in park or neutral; alternator noise gets worse as it spins faster. This can at least help ID the noise source.

Alternator noise usually means you need to have it checked as almost all the noise problems have been addressed by the auto manufacturers.

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WRVS497 Apprentice

WRVS497

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Alternator noise is on the low end of consideration. I have an aftermarket audio system in this truck that I installed myself with multiple amplifiers, a DSP, signal RCAs, speaker wire, and power cables all custom. There is zero engine whine on the signal RCA's or from the speakers so I'm fairly certain this is not an issue. My amplifiers are much stronger than the radio so if alternator noise was an issue it would be blasting at me. That doesnt mean that my equipment isnt filtering out, just saying I would certainly hear it there first.

In addition to that my coax for this rig is separated from the power cable(s) by more than a foot for the majority of its travel through the vehicle. The one place where they meet each other I ensured the traversal is perpendicular so I'm not convinced that would be the issue. Not saying its impossible just dont think thats it.

I'm pretty sure its the antenna design and coupled with the spring based on earlier replies. 

Having said that, I went ahead and pulled the trigger last night on that Laird BB4503 and the GBR8Pi that @gortex2 linked me to. I couldn't wait. We shall see what happens.

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WRVS497 Apprentice

WRVS497

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The Laird BB4503 and NMO mount upgrade definitely made a difference. Much less popping static now while in motion and the only interference I notice is the common multipath and/or obstruction dropouts which you cant do anything about. In addition the antenna is shorter with no external spring so it doesn't move and has a much lower profile on the roof.

Thanks for all the responses, especially @gortex2 for the Laird suggestion. I like the quality of these antennas so they will likely be my go to.

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