Author Topic: Ham HT with external antenna  (Read 2507 times)

Bill

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Ham HT with external antenna
« on: December 09, 2012, 06:39:51 PM »
I have a yaesu ft270 hand transceiver that I want to attach an external antenna to.  The antenna is the larsen nmo150b that I home brewed a mag mount for.  I use a pigtail that converts the sma to a pl259 connection to connect the antenna, but when I do I get absolutely no reception no matter where I place the antenna on the vehicle.  I had it on the fender of my dodge dakota in a nmo fender mount.  In that location I could get some reception sometimes.  In that configuration, with the adapter if i pushed the two pl259 connectors and screwed them together I would loose any reception I did have.  I must be doing something wrong but for the life of my I can figure it out.  Any one got any ideas/suggestions?  I thought about getting a different antenna but don't wanna spend more money if it isn't going to work.
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Howard Pletcher

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Re: Ham HT with external antenna
« Reply #1 on: December 09, 2012, 09:17:36 PM »
My first guess is the problem is between the antenna and the radio.  It sounds like you are not making contact someplace there.  The antenna itself shouldn't be a problem unless you're dealing with really weak signals.  Almost any piece of wire should receive.

I'd suggest finding someplace where you know you have a signal.  The NWS Weather Radio on 162.xxx depending upon where you are is a good signal as it's always on.  You should be able to receive it on the rubber duck, then switch to your external antenna and see if you can make it receive.  You should also check continuity of both the center conductor and the braid to make sure they're good and that they aren't shorted to each other.

If you can find a ham, you can probably find another antenna to check with and another radio to check your antenna.  Your sig line makes me think you are in SW Ind someplace.  Since I'm in Fort Wayne, I can't be of much help there.

Howard


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Re: Ham HT with external antenna
« Reply #2 on: December 10, 2012, 02:09:31 PM »
InPrinter will be along shortly but my first guess is its your connection!
Ill suggest never halfway doing it just jump in feet first and do it right. I won't do my own connections for the simple reason I can't test then and buying premise are cheaper than the headache.

That said a couple members have built their own setups and some have learned the hard way.

Not to laugh but I do recall a certain member here doing up his own setup and several miles into our journey never hearing 2 trains we figured it that something was amiss. Ya you guessed it.

Bill

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Re: Ham HT with external antenna
« Reply #3 on: December 10, 2012, 05:57:46 PM »
I had a local commercial radio shop solder the end si its good togo.  Checked ohms with  my meter and showed clear but the tab from the coil to the nmo mount was bent a bit to far up.  Gotta check the simple stuff first I guess.  Now I have the antenna in my bed temporarily and it seems good o three weather stations until I start moving then two of the stations come in and out as the antenna is swaying.  Any solutions for this new issue?

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Howard Pletcher

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Re: Ham HT with external antenna
« Reply #4 on: December 10, 2012, 09:07:09 PM »
Getting the antenna up higher so you have a stronger signal should eliminate the mobile flutter.

INprinter

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Re: Ham HT with external antenna
« Reply #5 on: December 10, 2012, 09:52:13 PM »
Good advice already given. Just to reiterate: Check your cables for continuity and also shorts. Best place to mount antenna on mobile is in the center of the roof, second best place is on trunk lid(if you have one), third best place is on fender(that's where I have mine do to fact that I will not drill a hole in the roof of my truck). Make sure your radio has good electrical and RF ground. Drilling a hole in the sheet metal is the best way is you are willing to do that. Get your electrical power straight from the battery. Run a separate, heavy gauge line with appropriate fuses in both Pos and Neg lines. Plugging into the cigarette lighter or some wire under the dash just leads to needless ground loops and possibly alternator whining etc.

INPrinter

PS. I can't imagine someone on this board doing their own radio setup and not hearing the trains. Just can't imagine who that might be. I wonder if they ever figured it out? Did things get better? Do they have strange looking antennas on their vehicle?
Shelbyville-1st RR in IN: 7/4/1834. 1st RR abandoned in IN: K&S RR 1854, 26 miles. Making IN RR history. Without photons photography would be a black art. You can never get cornered in the Roundhouse.

torgy1962

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Re: Ham HT with external antenna
« Reply #6 on: December 11, 2012, 01:12:46 PM »
due to fact that I will not drill a hole in the roof of my truck

That's exactly what I did on both my brand-new Suburbans! Absolutely outstanding scanner reception.

Bill

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Re: Ham HT with external antenna
« Reply #7 on: December 11, 2012, 03:02:43 PM »
I guess dodges have double sheet metal or something so I have the fender mount bracket.  Works better but still comes and goes on some of the weather channels.   By the way im using a ht if that is of any consideration

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torgy1962

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Re: Ham HT with external antenna
« Reply #8 on: December 11, 2012, 03:12:25 PM »
The hardest thing about installing antennas on my Burbs was removing and installing the headliner without damage. The trucks also have a bunch of ribs that you need to avoid when locating antennas

INprinter

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Re: Ham HT with external antenna
« Reply #9 on: December 12, 2012, 02:57:05 PM »
That's exactly what I did on both my brand-new Suburbans! Absolutely outstanding scanner reception.

If I did drill the hole and mount the antenna in the middle of the roof, I would have to forgo ever parking the truck in the garage. The clearance distance is less than 1". I have adjusted the door travel to maximum up position and the roof just does clear the door framing. Sometimes we throw magmounts on the roof and that seems to work ok as well. I do have an unusual discone type antenna that I throw on the NMO fender mount position and that works quite well. Yes, would work better if mounted on the roof, but just isn't going to happen.

INPrinter

PS. What actually makes up the "ground plane" of the antenna mounted on your vehicle? The antenna you see is just half of the actual antenna. What part does your vehicle play in the antenna system? For the best answers to these questions go to http://www.k0bg.com/ . The info there is slanted towards HF antenna installations on vehicles but the theory will apply for VHF antennas as well.
Shelbyville-1st RR in IN: 7/4/1834. 1st RR abandoned in IN: K&S RR 1854, 26 miles. Making IN RR history. Without photons photography would be a black art. You can never get cornered in the Roundhouse.

torgy1962

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Re: Ham HT with external antenna
« Reply #10 on: December 12, 2012, 03:11:19 PM »
That's a good website.
I don't have a garage, so vehicle height is not an issue for me. Whenever I needed to use a parking garage I just unscrewed the antennas, but in the case of by '87 Suburban, it was usually too tall even w/o antennas.

INprinter

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Re: Ham HT with external antenna
« Reply #11 on: December 12, 2012, 03:18:35 PM »
That's a good website.
...

The author of that website helped me to engineer my mobile antenna and radio installations. He's a great source of no-nonsense info when it comes to radios and antennas. My "PS" was only intended to get folks to go read some real good, reliable info on how to do it right. That would be better than me just driveling on about things I just barely understand myself.
Shelbyville-1st RR in IN: 7/4/1834. 1st RR abandoned in IN: K&S RR 1854, 26 miles. Making IN RR history. Without photons photography would be a black art. You can never get cornered in the Roundhouse.

torgy1962

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Re: Ham HT with external antenna
« Reply #12 on: December 12, 2012, 06:43:08 PM »
He's a great source of no-nonsense info when it comes to radios and antennas. My "PS" was only intended to get folks to go read some real good, reliable info on how to do it right. That would be better than me just driveling on about things I just barely understand myself.

Yes, there's a lot of "nonsense" associated with mobile installations, and one can always learn something new. While I'm an electrical engineer, my specialty is factory automation/ machine safety, not antenna theory, etc.

central1751

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Re: Ham HT with external antenna
« Reply #13 on: December 15, 2012, 09:13:05 AM »
The larger flat metal surface, the larger and better ground plane you will have.  But there are also antennas that do not need a direct ground plane.  Marine antennas and many CB antennas are this way to work on boats and semi tractors that are mostly fiberglass or the antennas mount outboard on the mirrors or up on the flying bridge.  I myself run 3 seperate antennas on my 88 Dakota.  I have a Comet duel band pig tail, 2m/440cm mounted to a Larson NMO mag mount centered on the cab roof.  This is for my Yeasu dual band mobile radio.  I have a 2m 5/8ths wave whip mounted on a "L" bracket bolted to the front stake pocket inside my bed just below the bed rail top, thats for the scanner, antenna is peak tuned to the 160/162mhz range instead of the 2m ham band now.  On the opposite side from it is a K40 mounted to an "L" bracket mount for my CB radio.  All three work perfectly.   I used to have a Motorola firecracker antenna off a scrapped locomotive, but it got lost in one of my moves or I have not found it yet.  It worked really, and I mean really good for RR band stuff.  Keeping the line losses to a bare min in the feed line to the antenna is very important.  Both for reception and more importantly if your going to transmit with said antenna.   73's   Mike  N9ZXLZ

Bill

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Re: Ham HT with external antenna
« Reply #14 on: December 16, 2012, 06:39:04 PM »
Got to playing some more with my radio and realized I had the squelch jacked up.  That explained all the traffic ive been missng.  Ill be back in my work truck tommorrow so ill see how it really is doing with the fender mount

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REX LAMAR

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Re: Ham HT with external antenna
« Reply #15 on: February 24, 2013, 08:30:43 PM »
WHEN USING A "HAM HT" DUAL BAND, ONE TRICK TO GREATLY IMPROVE RECIEVE IS TO CHANGE SO THAT YOU ARE RECIEVING THE RR BAND ON THE 440 SIDE. THIS MAKE THE RECIEVE SENSATIVTY A LOT BETTER. IF YOU TRY TO LISTEN TO RR BAND ON 2M SIDE IT'S OUT OF BAND ENOUGH THAT THE SENSATIVITY IS POOR. ALSO TUNING YOUR ANTENNA TO THE RAILROAD BAND MAKES BIG DIFFERENCE ALSO, BUT IF YOU ALSO USE YOUR HT FOR IT'S INTENDED PURPOSE THIS IS A NO NO.

REX
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INprinter

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Re: Ham HT with external antenna
« Reply #16 on: February 24, 2013, 09:14:39 PM »
I would just refer you all to the ARRL.org website, the ARRL antenna handbook, the ARRL Operating Guide and the http://www.k0bg.com/ website for the real "skinny" on how to get the most out of your mobile radio installations. There are a tremendous amount of "myths" floating around out there about how and why radio communications work or don't work. I have never been misled by any of the above referenced sources.

Do yourself a big favor and check out these resources. You may have to read the materials a few times but it will be well worth it. You could spend at least two weeks alone on the K0BG website. If you did, you would probably come away knowing more factual information about proper mobile radio installations than most of the folks out there just repeating the myths.

INPrinter
Shelbyville-1st RR in IN: 7/4/1834. 1st RR abandoned in IN: K&S RR 1854, 26 miles. Making IN RR history. Without photons photography would be a black art. You can never get cornered in the Roundhouse.