SMA Connector Mobile Antenna

[bwhite]

Somewhat to my surprise, after years of having scanners with BNC connectors lo & behold, my 396 has an SMA connector. I understand that I can use an adapter, but, my fear is signal loss if I go that route.
Is it fair to say, obtaining a mobile antenna with an SMA connector is
the way to go? If so, any recommendations for, preferably a mag mount
covering VHF Hi & 800's ? It will probably be mounted on top of the
bed rail of my pickup right behind the cab, but I'm open to innovative
suggestions.
Thanx all.

 

[n5ims]

Using quality adapters that are correctly installed will give you some loss, but not enough for you to notice. It's like the bathtub example. You have a bathtub half full of water (representing the loss of your antenna system's cable and existing connector). You then add a cup of water to the tub (representing the additional loss from the adapter). You look at the bathtub and how much water is in it. Did that cup of water add so much water that you notice the rise in water level? Probably not in the least.

 

[W8RMH]

I have used either a BCD396T or my newer XT with and without the supplied adapter for over seven years and I have not noticed any difference. I don't really think that little fraction of an inch is going to make any difference. Plus the BNC makes antenna change outs easier and a lot quicker. I use BNC adapters on my HH ham gear as well with no issues.

 

[davedaver1]

The loss is negligible, but one concern with using adapters that chain together at the antenna jack is physical stress on the connector on the radio. The duck antenna has a wide base that minimizes stress on the SMA jack, but when you hang an adapter on it, the weight and pull of the adapters and the cable make it susceptible to damage. Personally I don't mind the extra time required to twist off an SMA connector so I have antennas for the scanner and HTs that have SMA connectors only. There are a number of ham and scanner mag mounts that have SMA connectors.

You could also use an adapter like so: http://www.dxengineering.com/parts/cma-hb-05?seid=dxese1&gclid=CKq0pd-I2LoCFYM9QgodlhAAzA

As for antennas - check out this one: SpectrumForce Wideband Antenna with Mag Mount and SMA

It won't make a ton of difference, but your reception will be better on the roof rather than a bed rail. The influence of the metal body will make the antenna act somewhat directional.

 

[bwhite]

Gents,
Thanx for the info, I didn't know if an adapter would create negligible loss or be pronounced.
I purchased both my 396's 2nd hand, I wasn't aware there was supposed to be a supplied adapter. I'll have to see what I can do to locate one. Having the ability to use most any available scanner antenna would be a plus (BNC connections on most).
I know that putting the antenna in the middle of a field of sheet metal such as the roof but my vanity won't let me do that, smile. Good other info and considerations Dave. I'll check out the links in a bit.

 

[n5ims]

If you're worried about loss you need to check what coax is used on the mag mount you're interested in. Especially if it has an SMA connector on it. Many of them use a very thin RG-174 type coax, which is quite lossy (3.666 dB over the standard 12' run for a typical 800 MHz signal vs. about 2.5 dB loss using RG-58). Remember that the reported gain is generally just the antenna and ignores any loss from the coax.

 

[teufler]

I agree, the SPECTRUMFORCE works good. I travel with it all the time. Small, lightweight, and the price was right. I got mine at $9.95 at a hamfest and the wind bends it alittle at highway speed, it easily comes back to shape with alittle bending. I use the antenna at the house, mag mounted to the top of my 780xl scanner. Receive range is improved. Less hiss an distant stations. As for mobile coax, used to manage a company that sold time shares on 800mhz systems across the U.S. We used a coax that was white, made by Teflex. It was teflon coated, white in color and extremely low loss at 800-950 mhz. Motorola supplied it . For listening to 800 trunking, a loaded 800 mhz mobile antenna is great.`````They are 14 inches long. Little pigs tail curl near the bottom. Looks similar to a cell phone extrernal antenna. Most commercial radio dealers have some, probably in the scrap bin and eager to get rid of them. By far the best base antenna I have is a cell phone antenna that the cell phone company took off the local water tower. Its more like a corner reflector design, but it helps bring in 800 systems from 50-70 miles way. They stand about 4 feet tall. You've seen them on water towers, mounted on the rails around the tower. Phone company just gave them away, as the tower was getting repainted and they would put up new antennas and large hardline. 1 1/2 hard line. They gave away the hardline but not the connectors. Connectors are $215.00 each.

 

[bwhite]

Thanx gents.
I ordered the Spectrumforce, for $19 + yuck shipping, not overly burdensome.
Now to try and route the cable to the scanner without drilling a hole in the new vehicle or distorting the rubber around a window.....we'll see.
I was going to purchase a car charger from them too, it appears to be the Uniden model, however the single user report mentioned that it fried his 396 so I passed.

 

[LtDoc]

I agree with the other posters. The one thing that I don't agree completely with is the location of that antenna. Behind the cab of a pickup is just not a good place to put any antenna, much less one that deals with 800 Mhz. It may not seem like it but the cab will certainly 'block' signals from some directions. Putting the thing on the roof really is a better alternative. And while I can certainly 'identify' with that drilling a hole thingy (been there), do it anyway. If it's done correctly, meaning something close to 'right', it will make no difference in the value of your vehicle and do much better. Or better yet. Go the mag-mount route and change antenna positions from bed rail to cab and see for yourself... then drill the hole.
- 'Doc

 

[bwhite]

Yup, I know having as large a possible "field" of sheet metal around the antenna gives the better ground plain. You're right, I'll probably experiment around a bit with location, the trouble being, 12' of cable ain't giving a large number of options. I was even thinking of dead center in the bed although my bed is composite, I don't think there is sheet metal under it. Funny, one of the posts also mentioned removing the plastic on the magnet as it apparently creates a much better ground plain connection and reception. I know I won't be jeaprodizing my paint without trying it with the plastic on first.
I know drilling the hole won't affect the future value, if the connector wasn't already on the radio end it would be easy to find a crack to shove it through.

 

[teufler]

The SPECTRUMFORCE antenna is so small, the coax can be pushed inside the windsheld molding, then it can come around the door jam and into the car. the mag base is only about 1.5 inches across. I have not noticed any reception changes from reading up and sticking on a rental car roof as I drive out of the lot. Not centered but adaquate.THE ANTENNA UNSCREWS FROM THE BASE EASILY SO WATCH THE ANTENNA UNSCREWING IN THE WIND. I've thought about taking pliers and tighting it but I was afraid of stripping the screw that goes into the bottom of the antenna. Never has blown off of fell off but it has become unscrewed alittle. When you first get the antenna, you will laugh at how flemsy it looks. It receives well, thats what you are getting it for and that is all that matters. After driving at 70 mph, the antenna has developed a bend to the rear. Small antenna wire, you can bend it back or just let it slop alitte. Doesn't seem to hurt reception. I take it off and go to hotel rooms with it. Mag base, I find the window heating unit, or the tv, anything metal, and you are back in business. Even used a waste basket turned over. If you get a so-239 to sma adapter, make yourself a tape measure beam. Go to Google, type in "tape measure beam". Small, light weight, portable and they really pull in weak signals. You can travel with this as no piece is over 12 " in length, just press the tube pieces together , screw on the adapter and listen. The antenna is a vhf design, about $9 to build. Even as a vhf antenna, it works well on the other bands. Its about 8dbd gain.

 

[bwhite]

Thanx for the info T. I will prob try to run it thru the slider windows in the back of the cab initially using a little bit of a drip loop to coax rain to drip outside.
You may want to get i little bottle of Thread Lock or even use epoxy on the threads to prevent inadvertent unscrewing.

 

[bwhite]

Thumbs up on the SpectrumForce. I've not seen cable this tiny, I like it; it routes and hides so much better.

 

[LtDoc]

I'll repeat what's already been said. Something the size of RG-174, about 1/8" in diameter, is terrible for the higher UHF bands. It was made for very short runs, not long ones by any means. It's physically smaller, sure, but depending on frequency and length of run, it's electrical performance also suffers.
- 'Doc

 

[bwhite]

Gotcha LtDoc. In this case, I'm willing to sacrifice some performance for convenience and for it's non-obtrusive presence.