HowTo: DIY radio helmet mic, on the cheap (Page 1 of 2)

Very Cool ... now I just need 3-5 UHF radios!

(how do I convince my team to buy them!!)

You just need two. One for the pits, and one hardwired into the car. You will want a spare battery for the pit radio.

Scott

Nice write-up.

I'd recommend at least 3 radios, a little redundancy is a good thing, but prefer a radio for each team member. We have a pile of radios now.

I have had good luck with Radio Gear Pro. The Puxings use a Kenwood plug and work well.

The Motorola GP68s are also a good option, they use the standard Motorola 2-pin, but you will have to get them from a different supplier.

Both of those radios function in the business band and are what I would consider "light duty" business radios. They are not as drop kick worthy as a full on business radio but they get you in the business band, offer battery eliminators and allow the use of external antennas. I don't think either are FCC approved.

The 10K resistor is relative to the microphone. I've never considered using a PC mic but it's a nice way to get a boom mic. The Pro-Grade equipment uses 150 Ohm dynamic microphones. The dynamic aspect of the mic is more about how the mic works, the impedance is how the radio sees it. The Pro-Grade car harnesses are designed to work with 150 Ohm microphones so your only guarantee it will work in all situations is to run a 150 Ohm mic and I haven't found any cheap ones.

Some radios are more forgiving them others though. For example, we use Motorola GP300s and they are happy with 150, 680 and 2200 Ohm microphones with no problem. A newer Motorola CP200 can be the same way depending on how the harness is grounded. One way will work up to 2200 Ohms and the other will not. I was unable to use a resistor to increase the range but was able to reconfigure the harness wiring. So a helmet kit like this is less universal. The harnesses I make are tested on the radios I have with 150-2200 Ohm microphones. The significance of 2200 Ohms is it's a common impedance for electret condenser mics and Midland's speced that but they do go higher.

Aside from impedance here are some other experiences I have had. We made our first home made helmet kits back in 2010 which were made from mics and speakers from our cheap motorcycle kits and Radio Shack connectors. They worked fine but the Radio Shack connectors are not very good quality and fall apart pretty easily. While working on the CP200 puzzle, I had the tip of an 1/8" Radio Shack connector get stuck in the radio. It's a $300.00+ radio and the tip of a brand new Radio Shack connector was stuck in it. It's about $50.00 to get that 2-pin connector replaced. I took the radio apart and was able to get the tip out but it really stressed me out. Swithcraft connectors are much higher quality and much more expensive. Neutrik has the Rean line which is a good quality connector at a reasonable price. We also had the tip fall off of a pair of $100.00 foam earbuds so this stuff does break and spares are good.

Speaking of Radio Shack, they do have cheap Electret Condensor Mics (ECM) which you can use if you are okay with a free floating, velcro in place mic which is what I make. They are omni-directional and the PC mic probably is too. I use noise cancelling microphones which eliminate a good bit of back ground noise but I still have an omni-directional mic in my own helmet and it's okay. One of these days my helmet will get a new helmet kit.

If you make helmet kits like this and they do not work with the car harness/radios you plug them into it's due to impedance, you will get little assistance from whoever you bought the harness from. I currently have a brand new harness for a Motorola Mobile radio from a big name racing radio supplier and it doesn't work. I called them and they tested it on their own equipment and it did not work for them either. Most of the racing radio suppliers are just resellers and know little about how or why the products work. If you mix and match parts it may or may not work and they may not understand why.

I think a lot of the Puxings are the same way. The radios with key pads that allow user programming are cool but as easy as it is to program. It's just as easy to screw up the programming.

The pricing is attractive though.

The Police did show up to a race in California due to radios. A team was using police or fire radios that I guy brought from his job as a police or fireman. I don't know the exact details but it is something like that.

There are licenses involved with some frequencies. No, we don't have one either. Narrowbanding goes into affect next year too and I don't think my radios are compliant with that either. I guess we will just have to shut up once the FCC shows up to our race.

The way I remember that story, the frequency used by the race team was the same or just close enough to interfere with a reserved police band in the area where the track was, and the source of the interference was traced back to the track.

So, second hand fire/police radios are probably not the best choices.  Radios with a channel selector that can be programmed yourself to various frequencies are your best bet.  As soon as I pull up to the track I turn my radio on and just listen for a while for chatter.  I might transmit a 'anyone on this frequency, hello hello' a time or two before the race just in case.  Prior to the race, I'll repeat that, and if necessary switch our radios over to another channel and repeat.  So far, I've not had to switch.

Seconding that, cheap connectors are OK for hobby use, or situations where a connection will get light use.  For race radios, you're going to be plugging and unplugging multiple times over a weekend, spend a bit more and get the good stuff.  I'm the radio guy for the teams I've been with, and my job is to make sure the radios are at least as, if not more reliable than the car itself. 

I just bought 3 of these:

http://www.amazon.co...d/dp/B007H4VT7A

I picked them over the 888s because they're tested at 4W on high power, where as the 888s are about 3W.

Then I added a programming cable and assembled a DIY car kit based on a $20 IMSA jack from an aircraft supply shop, plus a kenwood PTT harness, roof mount antenna, and 12V battery eliminator kit. All together the cost of the 3 radios plus car system was $183.

My team already has IMSA connector'd helmet kits ($125/ea!) so that's why I had to get the $20 IMSA jack, along with keeping them PNP with our other team's radio gear. If you're starting entirely from scratch you could ditch the IMSA for something cheaper, and use the money saved for most of the connectors on the helmet kits. I've tried all the cheaper options, but you really need a good pair of "racing" earbuds. Its important for them to both block noise and get the radio sounds clearly into your earholes. That means each helmet kit will add about $50-75 for some good ear plugs and a decent mic (M101 is $10-15).

Ear buds:
http://www.plugfones.com/?page_id=274
http://www.jamplugs.com/
http://www.ruggedrad...products_id=310

We'll be putting them to the test at Chuckwalla. I'll let you guys know how well they work.

Awesome details.  Looking forward to hearing how it works.  Thanks for sharing.

To make it seem like they weren't completely clueless they did try and confirm no one was using that frequency, but I guess whatever was didn't register it in whatever list they looked at.

That's awesome, $800 for what is probably $10 in components.  I know their volume is going to be low and they have to recover their development costs somehow though!

So why exactly can't we use something like this?

http://www.bhphotovideo.com/c/product/8 … phone.html

psychoboy, if you are using the genuine Midland motorcycle kit, it is better than the on pictured.

The pictured kit will work but it's not very durable. In fact I'd say a lack of durability is giving it credit, they are fragile and delicate.

Mounting the PTT on the steering wheel is high risk too which frequently leads to a broken PTT.