Radio Tips for the DIY guy by PaulW

[PaulW]

DIY Radios Info
There are lots is details to deal with if you are a DIY guy. Here are my comments on what I have discovered after all these years. I need to point out that we use the commercial VHF band not the HAM or CB band. CB is really ineffective due to the long distances.
Race rigs have different needs than chase or spectator rigs.
Racer:
A race rig needs to be a quality VHF commercial radio with only a few freqs in memory.
These radios have automatic Squelch. They have a simple up/down button to grab an alternate freq and a simple mike.
Find out what other racers are using and begin your Internet evaluation by finding Internet reviews. Start with the race radio sellers and see what they are currently selling. Then buy the thing cheap off the Internet and buy the options discussed below.
Chaser or spectator:
These rigs need a versatile radio that has many freqs in its memory so the user can jump from place to place with ease. The most versatile radio will always be a HAM radio. Some need internal mods to be able to receive or transmit in the commercial band the racers use. Make sure the radio can transmit or receive with the race freqs or at least accept mods to do so. Weather man hates these radios because some do badly on the mod freqs due to crosstalk. The thing to remember is some work good and some do not. Your reviews on the Internet will tell you which ones are best. These Ham guys are so nerdy that they pay attention to these details.
Generic features:
Any radio you buy must have user-programmable software using a pc to radio cable. Buy that feature. Beware to get the proper setup meaning get a USB interface to the PC, not the obsolete hokey 10 pin d-sub or 9 pin serial connector. Make sure the software is designed for your PC (not many support Macs). Win 7 for sure and XP will work.
Get the keypad mike so you can enter a new freq in the field. For sure this is really inappropriate for the race radio since one would have to stop and figure it out. For a racer just get the simple stock mike.
A 50 watt radio it totally adequate for any mobile radio. The higher wattage radios are meant for base station with a 50+’ antenna.
Antenna:
You gotta have an antenna. Mag mounts suck because they fall off or get removed by a low branch. Shucks, I have one for my daily driver , but not my prerunner. For sure never use a mag mount on a racer. The only advantage of a mag mount is you can move from vehicle to vehicle or take it off when not needed so it will go into the garage without hitting. Most guys find this to much trouble. Jeeps are the exception since they come with plastic tops. Their solution is a mag mount on the metal hood. It’s a Jeep thing.
The hard mount attachment is called “NMO” you drill a hole in the metal top and attach with solder to your cable. The HAM radio place will sell these. If you do not have a metal top then you will have poor radio range due to lack of a ground plane. Never put an NMO on the Bronco shell since it is plastic. Anyway the plastic is too thick for it to fit.
Antennas come generic, meaning they are not tuned to your freqs. You must do that yourself. It involves cutting the whip to a specified length using your cutoff wheel on your Dremel. No big deal Google will locate a table for the mount you choose. Most of us choose either a quarter wave or a base loaded 5/8 wave antenna. Both will screw onto an NMO and can be found with a mag mount if required. Plug in 151.625MGHz in to the following links and you will get the following:
¼ wave whips are about 17” high. The 5/8 ones are about 46”. The half wave comes out 36” above the base. A high gain base loaded 5/8 wave is the most popular. Typical 5/8 wave base loaded whips vary from the generic value above. Example: A+3Db Ramdall/Larson comes out 45.64” and a +3db Antenex the length comes out 45.0”. This means when you buy a base loaded antenna use the chart that comes with the antenna.
Here is a link for generic cutting for half and quarter wave:
http://www.crompton.com/wa3dsp/hamradio/antcalc.html
Here is a link for the generic 5/8 wave:
http://kb5wck.com/antenna_calcs.php#58th Antenna
So what to do? Choose a frequency that you will use most often and other freqs near will work just fine. For a race rig use your assigned freq for cutting. For prerunning only or spectating use weatherman or 151.625
After you install the antenna and radio you will need to buy or borrow an SWR meter to verify radio to antenna quality. Again use the HAM store or the Internet. Be sure to get one that works for the commercial band - not the CB band like the ones sold at Radio Shack. The things come with instructions and cable. Mine is an MFJ-862. Just like the radio, get on the Internet and read the HAM reviews before buying. Here is a link for getting up to speed on various SWRs.
http://www.eham.net/reviews/products/40 ... 18effd4579
The SWR will identify bad connections and otherwise bad Installation. Remember after a few years of bouncing around in the desert things change and the SWR will tell you if all is well or is broken or degraded.
Use your DVM meter to verify your connections. No continuity between the center wire and the shield. Continuity between the shield and vehicle ground. Continuity between the center wire and the whip. Always use a meters lowest Ohm setting.
Radio Installation:
The manual that comes with the radio will provide the necessary info. These manuals always say connect directly to the battery. I do not do it because it’s too much trouble. Just find the +12 behind the steering wheel. It’s a #10 wire and goes directly to the battery with no switching and that is what I use. The ground goes to the dash frame which is solidly attached to the vehicle frame. No issues noted. Always power to the radio so I can use it with the ignition key removed. Handy.
I use RG400 antenna coax cable because it has less loss than the cheaper cable and has stranded wire and Teflon insulation - good for high heat and other abuse . Buy the cable from the aircraft electric supplier and solder on your own connectors after routing the cable. Radio Shack has the cable end connectors as does the radio vendor.
Mount the radio solidly to something metal for durability. Mine are bolted to the floor. I use stand offs that allow metal to metal contact to the radio mount. Avoid mounting the radio to the plastic dash cubby. The plastic will not survive hard bumps.
Contrary to the pros practice of keeping the wires separate from known RF antagonists circuits. Using quality coax eliminates any special considerations. If you end up with noise then re-route your power and ground wires.
Read what PCI says http://www.gofastbroncos.com/forum/view ... =32&t=3335
Programing:
Another major issue. Some friendly Internet radio sellers will provide you with the CD disk, cable and a typical data file with instructions. Be sure to ask them to send you a sample file that they made for a previous customer. That will make the whole process much easier. Pay extra if the seller won’t provide for free. My last buy was from Reddogradios.com. Friendly and has everything you need and sells the latest commercial radios. For a HAM radio, look at the hamradio.com and study their offerings. And do not forget to see the commercial band offerings being sold by
Pciraceradios.com, RuggedRaceProducts.com, and many others
Legal Issues:
One must remember that the using of any of the common race freqs in the US is rigidly controlled and only the race freqs should be used during the race otherwise you could get in trouble with the FCC.
In Mexico the freqs that you are NOT allowed to use are as follows:
153.0125 – 153.2375MGHz, and 159.0125 – 159.2000, and 163.0125 – 163.2375
If you are stopped in Mexico and asked for your radio permit be sure to tell the officer that you are not using the restricted freqs.
Last of all read the threads on racedezert.com. Some good info and some not so good? Here is one thread.
http://www.race-dezert.com/forum/showth ... 271A-radio
My radio collection includes - ICOM F121 race radio, a Kenwood Mcp-G707 multiband HAM unit, And two Yaesu VX-5R handheld HAM units. Programing is a significant chore as each has unique software. All are now obsolete, having been replaced by new models. I have SW for all.
PaulW
Fixed the spelling - PW

[bajascott]

Great read. I use rigpix.com as a reference when I happen to see a radio that looks like a good buy. One thing I ask people when they are looking for radio is what are you really going to use it for? I also tell them that they should be ware not to use the higher freqs,from 158.00 up to 174.00 as they are generally law enforcement or dispatching freqs.
One who does get a ham style radio should know that it is illegal to transmit on the ham bands in the 144.00 range bit it is really fun to listen to the chatter. That what is tuned in most of the time in my bronco because I don't have a cd player.
Asvv far as the rigpix.com site you can use that site to see if the radio you are looking into buy is able to transmit in the commercial bands. Usually if the radio will rx 136.000 to 174.00 it will be able to tx in those freqs as well with minor mods.
My radio units are icom ic2000 in bronco running 99% of the time.
Maratrac 100w in my mobile case with a 40 mast for base station
Yeasu v170 hand held moded to tx
And a icom ic-A20 for ground to air rescue.
I am working on getting my ham lic, and will be getting my own commercial freq for CODRA after I figure out what's happening with the narrow band crap the govt is doing to the commercial radios in 2013.

[Polarcub]

Great info Paul and Scott! Thanks for taking the time to put it together!

[AussieRod]

I finally had time to read this properly. This is great info for radio ignorant people like me. Thanks for the great write-up, Paul, now I have some guidelines to set up my gear and make it work like it should.

[PaulW]

Antenna install
In the aviation industry much effort is made to assure low resistance from the antenna mount to ground. The method to assure a good ground is directly applicable to any antenna install. The low ohm device mentioned below is typical of what the industry uses and can replace a high dollar meter with the same capabilities. Here is a copy of a recent discussion on this subject. Not many of us use aluminum bodies, but the same theory still applies to any metal antenna install. No alodine for steel, but simply using dielectric grease will preserve the metal to metal bond.
Copy of the discussion:
- - - - - -
Today I came upon a "General Antenna Installation Guidlines", written by Cobham which I think is the parent company to Comant. In those instructions they state that electrical bonding is best accomplished by "direct metal to metal" contact of the antenna base to the aircraft skin. Also paint is to be removed and to protect the aluminum against corrosion, the surface can be alodined. They then also mention using the mounting screws to provide a good ground as an alternate method with a couple of other stipulations. As well to test the bonding, a reading of .003 ohms between the base and the ground should be achieved.

So since I'm mostly using Comant on my -10, I guess I will continue alodining. I will check to see what kind of readings I get with my VOM.

Reply form the electric expert:
Your VOM is incapable of resolving resistance
measurements this low.

http://tinyurl.com/4l3tuj6

If you're not inclined to roll your own,
this is another option . . .

http://www.aeroelectric.com/Catalog/AEC/9008/
- - - - - -
I have one of the gadgets I bought from the AEC guy. Cost was $45. He still sells them here
https://matronics.com/aeroelectric/Cata ... talog.html
AEC9008-3 Low Resistance Measurement Adapter

Paulw