HT Mobile Install Problem

[pinballwiz86]

Hello. I finally bought myself a mag mount for my vehicle.

I attached it to the trunk lid and ran the coax to the front seat. I also made myself an air choke balun.


Tonight, I drove for a few miles and talked pretty good with a 4 watt HT attached to the mag mount.


All of a sudden it starts to cut out on me. Then, I can't hear the repeater at all but they can hear me. I can hear the local NOAA weather station though. I went inside and switched to a 19" whip. It then worked fine on transmit/receive.


What could be the problem?


Thanks in advance for any help.

 

[KQ9U]

Did the coax get pinched during the installation? Was it raining?

 

[pinballwiz86]

If anyone is having any RFI problems or bad reception from their mag mount, try moving the mag mount from the trunk lid to the roof. There may not be enough of a ground plane on the trunk lid. That solved my problem!

 

[jhooten]

If your car has a ferrous metal roof.

 

[pinballwiz86]

If your car has a ferrous metal roof.

It's not fiberglass like the BMW M3.

 

[jhooten]

My Camaro is plastic. One of the local guys has a metal roof that his magnet won't stick to. He swears his mag mount should stick to his aluminum roof.

 

[pinballwiz86]

Oh I see. So what did you do in your case Jerry?



And...I spoke too soon. It's acting up again. There seem to be a lot of "dead spots" where the reception starts cutting out. Maybe I need a larger antenna?

 

[AK9R]

Mag-mounts are notorious for having problems. Some basic trouble-shooting things I'd consider:

1. Is the mag-mount in good mechanical shape? Any loose parts? Any parts that don't seem to fit together well? Does the mag-mount attach firmly to your vehicle or does it rock?

2. Is the coax on the mag-mount in good shape? Is the coax well attached to the mechanical parts at the base of the antenna? Is the coax free of kinks, sharp bends, cuts or abrasions? Is the connector on the end of the coax properly attached? Is the connector the proper one for your radio or are you using adapters?

3. What kind of antenna do you have on your mag-mount? There are hundreds of antenna designs, so just telling us "mag-mount" doesn't help us much. Is the antenna properly tuned for the frequencies you are using?

4. How are you powering the handheld radio? Batteries or a cigarette lighter adapter?

5. You say there are dead spots. Do you live in a hilly area? Are there lots of tall buildings around? Are trying access a distant repeater?

 

[pinballwiz86]

Thanks a lot for your help! I have an MFJ "shorty" 2 meter antenna. It's attached firmly to the roof, no kinks in coax.


You know, there's quite a bit of strong pager signals in the area, etc. I think the Baofeng UV-5R+'s front end might be getting over loaded by the better antenna.


I just ordered the Baofeng UV-5B because I've read it has a way better front end. Hopefully that works out for me. I'll have to wait a few weeks for it to get here from China before I'll know!

 

[AK9R]

I have an MFJ "shorty" 2 meter antenna.

How long is it? Are there any coils in the elements?

You know, there's quite a bit of strong pager signals in the area, etc. I think the Baofeng UV-5R+'s front end might be getting over loaded by the better antenna.

That's entirely possible. Generally, handheld radios make lousy mobile radios. Their wide-band front ends and lack of filtering can deal with the RF trash that a rubber duck antenna hears, but a good mobile antenna hears much better than a rubber duck. Ultimately, I think you'd be better off buying a real mobile radio rather than another handheld.

 

[K5MPH]

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Thanks a lot for your help! I have an MFJ "shorty" 2 meter antenna. It's attached firmly to the roof, no kinks in coax.


You know, there's quite a bit of strong pager signals in the area, etc. I think the Baofeng UV-5R+'s front end might be getting over loaded by the better antenna.


I just ordered the Baofeng UV-5B because I've read it has a way better front end. Hopefully that works out for me. I'll have to wait a few weeks for it to get here from China before I'll know!

These radios have weak front ends they will get overloaded a lot they don't make good mobile radios but you can use them as a mobile......

 

[jhooten]

Oh I see. So what did you do in your case Jerry?



And...I spoke too soon. It's acting up again. There seem to be a lot of "dead spots" where the reception starts cutting out. Maybe I need a larger antenna?

L bracket on the rear quarter panel, one of the few metal body parts on the car.

 

[xxdanielt3]

L bracket on the rear quarter panel, one of the few metal body parts on the car.

Trunk/hood lip mount is another option.

 

[jhooten]

They are both plastic/fiberglass.

 

[pinballwiz86]

I've been trying out the mag mount with my Yaesu 2900R indoors. It works great so there's no problem with the coax or antenna or mount.

I finally received the UV-5B. Took the mag mount and attached it to my car. Hooked up the Baofeng and tried it out mobile.


I got great signal reports on it.


But, I could not receive other people at all. It was very staticky. I switched it over to NOAA and the reception was spot on.


What could be the problem with not receiving the repeater?


Thanks.

 

[AK9R]

I asked you two weeks ago how long the antenna was, but you didn't answer. So, I'll ask a different question. What is the model number of the antenna? Have you done anything to tune the antenna? Have you checked the SWR on the 2m band?

How far away are the repeaters that you are trying to receive? Are those repeaters on tall towers? Do you get strong signals from those repeaters on other radios or with other antennas?

You are comparing your reception of 2m repeaters with your reception of a NOAA weather transmitter. How far away is that NOAA transmitter?

You stated that there are lots of strong pager signals in the area. Paging transmitters will often overload the front end of inexpensive or poorly filtered radios and handhelds are notorious for having overload problems. Handhelds are designed to be used with rubber duck antennas. When used with antennas having better gain, it's very easy to overload the radio with too much signal.

 

[pinballwiz86]

It's the MFJ 1402 (black). No, I haven't checked the SWR. I'm only running 5 watts so I figure its not worth getting an expensive antenna analyzer.

Besides, I can talk on 4 repeaters no problem (full quieting). It's the receive that isn't working good.

Repeaters are 18, 25, 30, 45 miles out. They all give me a strong signal on my scanner and my Yeasu 2900R and my UV-5R. It's when I hook up the UV-5R/UV-5B to the mag mount that it acts up. On a Diamond SRJ77CA I get great reception.

The NOAA transmitter is 22 miles away.

I know handhelds are intended to be used with a low gain antenna. But, I don't want to wire up a mobile radio in my car. So, I'm trying to get this to work.


I thought about using a band pass filter to only let ~ 144-148 through.

I tried to use the PL tone of 88.5 hz on both receive and transmit. But that, sadly, didn't work. The radio was still overloaded.

I tried the antenna on the roof, then moved it down to the trunk lid so it would attenuate the signal somewhat. Didn't work.



Btw, I saw what you wrote before you edited your post. I get email alerts, lol.

I've only had my Extra ticket since May (I passed all three on the same session). I'm learning and trying improve my operating. Thanks for your help though.

 

[AK9R]

OK, that antenna may be a 1/4 wave on 2m. If it's less than 19 inches long, there's a bit of antenna matching magic going on there. Frankly, you'd be better off with a plain 1/4 wave antenna. When it comes to antennas, there's no such thing as a free lunch. If the antenna is physically short for the intended frequencies, the electrical matching and tuning to make it work mean that some of your signal, on both transmit and receive, are lost as heat. And, as many hams will tell you, some MFJ products are not worth the powder to blow them away.

You don't need an antenna analyzer to test the SWR of an antenna. SWR meters are not cheap, but they are less expensive than antenna analyzers. If you don't do anything to scientifically test your antenna, you are simply relying on the manufacturer and your installation skills. The final RF output devices in your 5-watt handheld can be destroyed by a bad antenna just as well as the finals in your 50-watt mobile radio.

Based on your observations, I think your handheld is simply being overloaded by strong signals in the area. You can band-aid the problem with band pass filters. Or you can use a different radio. I've never cared for using handhelds as mobile radios. The filtering in most handhelds is easily overloaded when connected to mobile antennas, the user interface is not designed for mobile operation, and all the cables (antenna, power, speaker-mic) easily become a rats nest.

Using PL won't help if the radio's front end is being overloaded by strong signals.

 

[pinballwiz86]

I've been running a BC125AT scanner in my car since back in December 2013.

I just bought a Yaesu FT-7900R dual bander. I'll let you guys know how that works. Should get here Friday.

Thanks for the help.

 

[N9JCQ]

you will not be disappointed with the 7900. I have 7800 and its a great radio. Lots of memory and a pretty good front end as well. I still have a few spots where I get some intermod interference. Get the programming software too.