eHam

eHam Forums => Mobile Ham => Topic started by: CERTNEAL on August 07, 2009, 10:13:15 AM



Title: Motorola shop question
Post by: CERTNEAL on August 07, 2009, 10:13:15 AM
I am in need of some help installing my 2 meter radio. The local Motorola 2 way shop seems a good choice but do I need to worry about the quality of anything they use. Mainly I am wondering about the power wire they might use, he said he may have some "laying around" that he could use.

These guys do a ton of cop cars and I figure they know what they are doing but should I be at all worried they may use some lower gauge wire to get by? My radio is an older Azden but it is 50 watts and I want to get all I can out of it. I plan to get a larsen NMO 150 antenna and NMO mount for them to install as well, the price seems well worth it so far.

Thanks in advance!


Title: Motorola shop question
Post by: WB2WIK on August 07, 2009, 10:49:55 AM
I'm sure they'll use appropriate wiring, this isn't rocket science.

For the Azden #12-2 should be plenty if the "run" is 20 feet or less, which it certainly ought to be for any conventional car or light truck.


Title: Motorola shop question
Post by: KB1LKR on August 07, 2009, 12:45:34 PM
Just ask them to run 10 AWG (or perhaps 12 AWG) wires for power, so they know what you need/want.


Title: Motorola shop question
Post by: N2HBX on August 07, 2009, 06:18:37 PM
Let them know the power output of the radio. Any MSS worth the name will install the correct gauge wiring.

73,
Larry, N2HBX


Title: Motorola shop question
Post by: CERTNEAL on August 07, 2009, 06:53:07 PM
I appreciate the answers, makes me feel a bit better about using them.

Cheers,
Neal


Title: Motorola shop question
Post by: KF5BTI on August 07, 2009, 09:04:03 PM
Why not ask them about the install details to before they perform the install.  Depending on the shop they might also allow you to watch/supervise the install to ensure its up to your standards and you may learn some new tricks/techniques.


Title: Motorola shop question
Post by: K0BT on August 07, 2009, 11:01:53 PM
I wouldn't worry about the phrase "laying around" when they talk about wire.  An MSS will probably have a lot of old wiring harnesses in boxes.  They were sufficient for 100W Motracs, so the wiring will work fine for your purpose.  As the other poster indicated, any MSS worth its salt will install your radio correctly.


Title: Motorola shop question
Post by: CERTNEAL on August 08, 2009, 05:07:51 AM
I do hope to be able to watch, as this is my first radio I want it done right, but the next time I hope I can do it myself.

Once again I appreciate the help and look forward to being on the air soon!

Aloha,
Neal


Title: Motorola shop question
Post by: K5LXP on August 09, 2009, 08:36:54 AM
You could also eliminate all doubt and supply them with the materials you want them to use.  Wire, fuseholders, powerpoles, premium NMO mounts, coax, you name it.

Just because a two way shop does a lot of installs doesn't mean they do it well.  I've had to repair more "professional" installations than I care to recount.  In general you get what you pay for.

Odds are they'll do a clean professional job. But there's nothing wrong with "helping" them to make sure it happens.  

Mark K5LXP
Albuquerque, NM


Title: Motorola shop question
Post by: CERTNEAL on August 11, 2009, 05:23:06 AM
Mark I appreciate your comment, I had the same idea and plan to give them a Larsen NMO mount and 150 antenna to install. My friend volunteered to help mount the radio and power wire, he is very good at most all automotive stuff like that.

Now I just need to find some 8 guage wire, I think Lowes has some. I know I probably don't need that heavy of wire but if I upgrade my radio I will have that part done anyway.

I plan to use a 49 stranded copper wire, does that sound about right? Should be about a 6-8 foot length so I don't think I will drop much voltage.

Thanks a bunch,
Neal


Title: Motorola shop question
Post by: K5LXP on August 11, 2009, 06:39:24 AM
6-8ft of number 8 is way overkill for a 50W radio, 12ga would be plenty.  #8 house wire from Lowe's will be kind of stiff, the real flexible stuff has many more strands, like this:

<http://www.powerwerx.com/product.asp?ProdID=30204&CtgID=1002>

8ft of 8ga is good for about 75A continuous draw, so you should be good for any 12V radio you'll ever connect to it.  FWIW, 8ft of 12ga is good for half that, which is still more than enough for almost any 12V radio...


Mark K5LXP
Albuquerque, NM


Title: Motorola shop question
Post by: AA4PB on August 11, 2009, 06:43:45 AM
I'd look for the wire at an automotive supply store. The wire is generally more flexible and has a stronger insulation that what you'll find in Lowes and other home supply stores. #10 is probably plenty big enough for what you want to do and you can find it in a red/black pair that makes for easier routing.

Many modern vehicles have power attachment points close to the battery where you can make the connections (fuse the wire at the connection point) rather than going directly to the battery. This avoids the possiblity of your wires being corroded by battery acid over time.

If you attach directly to the battery then you need a fuse in the negative lead as well. If you connect to the attachment point at the ground end of the factory battery negative wire then you do not want to fuse the negative lead.


Title: Motorola shop question
Post by: AA4PB on August 11, 2009, 06:50:54 AM
By the way, #10 wire has a resistance of 1 ohm per 1000 feet or 0.001 ohm per foot. An 8-foot run (16 feet total down and back) will have a voltage drop of about 0.15V maximum for a 50W radio.


Title: Motorola shop question
Post by: CERTNEAL on August 11, 2009, 10:34:50 AM
Thanks again for the help guys! I am going with a 10 gauge wire I can pick up at Advance auto. Any recommendations on how to fuse the ends, the connector to use?

Thanks much,
Neal


Title: Motorola shop question
Post by: K5LXP on August 11, 2009, 02:29:22 PM
You can get inline blade fuse holders in the same aisle you found your wire.  The local Auto Zone here has two sizes, I go for the 40A version (#10 wire).  The fuse you use in it is dictated by the current draw of the radio.  I would use whatever the OEM used in the factory power lead as a starting point.

Use butt splices to connect the inline fuseholder to your wire, and then crimp an appropriately sized eye lug onto the remaining fuseholder lead.

Attach to the battery terminal/power distribution stud per AA4PB's post.

Personally I never would connect the negative lead directly to to battery, so a negative lead fuseholder isn't necessary.  Just an appropriate eye lug on the negative lead and ground it near the high current battery chassis ground connection.

Routing is important.  At a minimum secure it with tie wraps to stable points so that it doesn't flex or abrade against anything and to keep it away from anything hot.  As an extra measure of protection you can use split loom.  Leave a little extra slack at the end to allow servicing later.  I usually bundle a fold of wire along with the fuseholder and secure them together with tie wraps to a convenient support.

As far as radio end termination the sky's the limit.  You can butt splice it directly to the radio harness, use powerpoles or come up with your own distribution bus.  

Hint: Leave the fuse out until you're ready to test the installation.  Check everything with a meter before you connect the radio.


Mark K5LXP
Albuquerque, NM


Title: Motorola shop question
Post by: K0BG on August 11, 2009, 03:13:29 PM
Mark and I are on opposite ends of the spectrum here.

All manufacturers, without any exceptions, recommend direct connection to the battery for radio equipment. However, there is a case to be presented wherein direct connection could place a large load on the radio wiring itself. I personally have never seen the results of such a failure, but that in itself doesn't preclude it.

The other issue is one of current draw. The battery does have a DC return line for the accessories. It's typically inadequate for current draws in excess of that drawn by the accessories. One could argue that there isn't a case where everything in the vehicle is turned on at once, but the manufacturers know that too, so they size it accordingly. For example, the accessory ground in my Ridgeline is size #6, and the main harness fuse is 120 amps, which exceeds the wire's capability. If I were to add another 20 amps, the accessory ground could fail, and we'd have the scenario mentioned above.

To direct connect or not to direct connect is a matter of choice, except in cases where a high power amp is used. In any case, adequate wire size is essential. The rule of thumb is to keep the voltage drop below .5 volts, under full or peak load as the case may be (not average load). Quite obviously, the correct fuses need to selected as well.

For more information on selection, visit my web site.

Alan, KØBG
www.k0bg.com


Title: Motorola shop question
Post by: CERTNEAL on August 11, 2009, 05:16:08 PM
I think I will go directly to the battery, using fuses on both lines at the battery.

Those powerpoles look nice but for now I think I will go a bit more simple in that area and upgrade as I get the cash.

Can you guys recommend any good meters I may need for a two meter setup like this? Budget being a concern, the very basics are what I can afford just now but I don't want anything blowing up on me if I can help it. Also anything I may need for my antenna?

Thanks again,
Neal


Title: Motorola shop question
Post by: K5LXP on August 11, 2009, 08:20:40 PM
Odds are you can connect the negative lead to the battery and nothing bad will happen.  But your odds are even better than that if you don't.  I have seen the effects and it ranges from radios that get hot even when they're off, to wierdness during operation, to burned up circuit boards and damage beyond repair.  All for the sake of doing it "by the book".  So I move my negative connection 6" away and mitigate the risk.  The manufacturers are betting the fault current will blow the negative fuse.  I'm betting it won't.  My evidence is empirical.

What kind of meters are we talking about?  The meter I referred to was a basic voltmeter, $3 on sale at any Harbor Freight.  As far as SWR/power meters I would only worry about that when initially testing and tuning the antenna.  Nothing should change during normal operation to require you to monitor that.  You can borrow a meter or have another local ham help you check and tune the antenna.  You could also use an antenna analyzer, which makes the job quick and easy.  If your install is good the resonant points will be very close to the cutting chart.  The NMO 150 is a durable and reliable antenna, mine's been on my truck over 20 years now.


Mark K5LXP
Albuquerque, NM


Title: Motorola shop question
Post by: KF5BTI on August 12, 2009, 05:35:50 AM
Got a question regarding the fusing of a ground.  Do you run the risk of blowing the ground fuse and the radio then pulling its ground through the shield of the coax?


Title: Motorola shop question
Post by: N8ESD on August 16, 2009, 07:16:21 PM
I have worked in several Radio Shops including 7yrs at a Motorola Shop. Shops can be hit or miss when it comes to installations. Keep in mind that is where most techs start there career. If you find a good shop you will be fine.

A couple of suggestions-

#1 FUSE EVERYTHING AT THE ORIGINAL POINT OF POWER SOURCE.

#2 GROMMET ANY CABLES PASSING THRU THE FIREWALL.

#3 SOLDER EVERYTHING

#4 10ga power wire sould be fine , make sure they ground to the same point as the battery ground not the battery post, also take the power feed to the main lug of the under hood fuse block not the battery terminal. If you go to the battery terminals they WILL Corode. If your want the radio to turn off and on with the key add a bosch relay connected to a switched fuse in the internal fuse block. (Little trick- after making connections under hood, spray with clear Krylon spray paint. Connections will look new for a long time)

#5 DO NOT USE THHN wire, the insulation and coating WILL NOT hold up to automotive heat. A good source for wire is a car stereo install shop or www.partexpress.com

#6 Antenna use a Antenna Specialist ASPR-7495 for 2m (can also be cut to be 3DB gain on 440) This is a wide band 1/4 with a spring. These use an NMO mount and are 24mhz wide on VHF and 80mhz on UHF, they have an extremely heavy rod. I have used them for the last 20yrs and never had one fail.

#7 If you mount your antenna on a trunk lid make sure to add a heavy duty ground strap to the lid at the hidges.


Good Luck on your install


Title: Motorola shop question
Post by: CERTNEAL on August 16, 2009, 07:37:24 PM
Thanks again for the advice, I just got my ticket today so kinda excited about getting my radio set. Hopefully by the time I have it set I will be in the fcc database.

I got 2 fuses for negative and positive by the battery, also some split loom to help protect the 10 gauge wire I got from advanced auto. I have a 10 amp fuse on the positive side by the radio, what size should I use for the ones by the battery? It's a 50 watt radio and that's all that will be on that line.

Thanks again!
Neal


Title: Motorola shop question
Post by: K0BG on August 17, 2009, 05:11:44 AM
If you visit my web site, and read the two Wiring articles, you'll have all the info you need to do the job correctly.

Alan, KØBG
www.k0bg.com


Title: Motorola shop question
Post by: N8ESD on August 17, 2009, 03:04:59 PM
Typically I use a fuse twice the amperage actually required. for a 50watt VHF radio I would use a 20A on both lines.


Title: Motorola shop question
Post by: W0FM on August 28, 2009, 12:43:18 PM
Neal,

Most commercial shops (Motorola and otherwise) have signs posted keeping customers from service bay and installation areas for insurance reasons.  See if you can find a ham at that shop (hams are usually well-represented in these shops) that can get his manager's approval for you to view the installation.  Exceptions ARE made from time-to-time.  A ham tecnician or installer at the shop would be a good place to start.  Just a hint from an "insider".

73,

Terry, WØFM


Title: Motorola shop question
Post by: AF6IT on October 07, 2009, 04:29:38 PM
What is the purpose of sizing a fuse at twice the typical load? Protecting the fuse? I thought the purpose was to protect the radio & car's wiring. I would use the same rating as what the manufacturer specified.


Title: Motorola shop question
Post by: K0BG on October 07, 2009, 06:00:20 PM
Stu, twice is a little too much in some cases, but not all. The rule of thumb is not to exceed 60% of the fuse rating under sustained load, especially when it's ICAS.

If you stress a fuse by subjecting it to say 80% to 90% in an ICAS load, it will eventually fail even though the fuse never saw and overload above its rating.

Fuses aren't an art, they're a science, and specific factors play into what ever service they're subjected to. I suggest you read up on the Littelfuse site for more information.

http://www.littelfuse.com  (Note, the spelling is correct).

Alan, KØBG
www.k0bg.com


Title: Motorola shop question
Post by: W0HC on October 20, 2009, 09:59:57 AM
I never ever ever use butt splices.  I learned that when working in a radio service shop.  Using them was grounds for immediate dismissal.