Radio question

[Boudy]

Not true. Propagation is symmetric (i.e., if the transmit powers are equal the receive powers will be equal in both directions on the link). Interference, however, is generally not symmetric and can affect sensitivity differently on each end of the link. I think the other posts on sorting out interference are probably spot-on. It's either a connectivity problem (with the mic or PTT switch) or an interference problem. Shielding interference sources in the car will probably help, but these things can be tough to sort out.

 

I agree 100%. I only add that "this" link is not symetrical in that it has a 3000 lb reflection problem on one end. From what I've read, it just seems to me that his problem is RF, not electrical interference.

 

1) It's a portable, he's not tied into the car's electrical system.

2) It works fine in the pits and wonderfully at times.

3) It covers most of Thunder Hill.

4) Other times it has poor TX with good RX.

 

Shawn's last post is the best next step.

 

Let us know what you find, Tom.

 

Boudy

[Eric J.]

I agree 100%. I only add that "this" link is not symetrical in that it has a 3000 lb reflection problem on one end.

 

Even with reflections propagation is symmetric. A ray reflected in one direction will reflect back along the exact same path in the other direction. For example, no matter how many mirrors you use, if you can see someone in a mirror they can see you, too.

 

From what I've read, it just seems to me that his problem is RF, not electrical interference.

 

The effect is the same. The interfering rf is probably coming from either his own car or other "noisy" cars or radiators nearby when he's having the problem. Not much one can do about the other cars when you're in traffic.

 

1) It's a portable, he's not tied into the car's electrical system.

 

Clearly a good thing!

[Boudy]

Happy 4th to all! No radio talk today, only beer, BBQ, and bench racing.

 

Boudy

[Tom A]

That's generally not a location problem, since if you can close the link in one direction you should be able to close it in the other direction from the same site (assuming similar radios on both ends of the link).

Yes, both have the same radio. We tried a bunch of different locations inside the car, none seemed to work any better than any other.

If you're transmitting the same power as the other guy it's not a propagation or location problem if you can hear but can't transmit. It's more likely to be a problem with getting the radio to key or with the mic-radio connection.

Definite possibility. The strange thing is 2 cars with essentially the same setup have the same problem. Some days it works great' date=' others not so much.

 

Actually, your thinking is correct but the car and pit wall are not equal. The driver suffers no less than a 6dB signal loss (75% loss) leaving the car.

Yikes. That could be the problem right there.

Hense' date=' there are areas of the track where he can't reach pit wall but pit wall can reach him. Tom's idea is well founded to get the radio as near to the window as possible. However, the cure to his problem is probably an external antenna. Unfortunatly, I think he's using GMRS/FRS radios and the FCC prohibits it.[/quote'] I am and they do. We are using Midland GXT500s and 550s. http://www.sportsmansguide.com/cb/cb.asp?a=201680

I've got a special running for NASA members on a radio package that won't break the bank. Details can be found here if interested:

http://www.camaromustangchallenge.com/cmcbb/viewtopic.php?t=1916

That is actually what got me thinking about trying to get our existing setup working. If we can't, we are looking pretty hard at your setup, or the entry-level setup from Shawn.

 

When you wrote "... because it works fine in the pits.", did you mean when the engine is not running, as opposed to the radio performance when the engine is running?

Both. Initial radio check, with the car off, but we have driven around the paddock, and had good coverage in the flat, (for those familiar with Thunderhill, we were paddocked at the back near the maintenance shed/pit-in, and had coverage all the way to the fuel pumps). My thought is the car makes a lot more RF noise at 5000 RPM than just off idle tooling around the paddock.

If so' date=' (and assuming a spark ignited engine, and assuming that the radio works equally well whether it is in the aluminum box or not) I would consider that the trouble might be radio frequency noise coming from the ignition system. For instance, are you using solid metal core ignition wires, rather than the other type which suppresses radio frequency noise?[/quote']I don't remember off the top of my head, but I think they are solid.

 

easy test- take the radio out of the car and start the car. bring the car up to RPM speed and then move the radio back towards the car... Does the radio start braking up when you move towards the car???

Good question, one I don't have the answer to. I'll try that.

 

YES- you could have a ground or ign problem or you need to get higher power (5watt) radios.

 

No (its still a problem)- are you running race tested equip, ie, shielding in car harness, noise cancelling helmet kit w/ transducer ear buds, does your crew headset have a noise cancelling mic, etc?

We are already running 5watt radios, the same Midland units you use in your GMRS based setup. None of it is shielded/noise canceling.

 

FYI- A set of 5 Watt GMRS radios should run you about $70 and you can add professional parts that are built for racing communications all for under $500 total. See the Starter System below for an example- Also, look at the "The Expert" for a super value on a long track system only $799

 

http://www.sampsonracing.com/sampson_racing_new/home_f.htm

Dumb question: If I buy your setup to work with my existing radios, could I switch to VHF/UHF radios later, or would I have to replace the harness? The GMRS solution is attractive because I already have the radios. I have enough of them that we can have spotters in a couple places on the track plus the pit wall, something really nice for endurance racing.

 

Word of Advice... make sure you understand the limitation of what you are buying and wheather it will work properly for your needs... If not, it might be just wasted racing funds that could of been used in a much better way... like beer for the crew

That is pretty much where we are now. How much more time and effort do we want to sink in to this, or do we just cut our losses and start over.

 

Thanks all,

[Tom A]

I agree 100%. I only add that "this" link is not symetrical in that it has a 3000 lb reflection problem on one end. From what I've read, it just seems to me that his problem is RF, not electrical interference.

 

1) It's a portable, he's not tied into the car's electrical system.

2) It works fine in the pits and wonderfully at times.

3) It covers most of Thunder Hill.

4) Other times it has poor TX with good RX.

 

That is what is really frustrating. When it works, it is great, and I really miss it when it isn't working.

 

Shawn's last post is the best next step.

 

Let us know what you find, Tom.

 

Boudy

I will. Thanks again.

[SRC/SampsonRacingComm.]

Hey Tom - The radios you have will do a fine job but you need to really look at setting yourself up for success w/ the correct racing communications gear in conjunction w/ your current radios.

 

FYI- before we sell any of our systems we test them all. From our testing at T-Hill w/ the Starter System you can get good communication coverage (70%) around the track but you will have complete loss over on the back side as you go up the hill.

 

All of our systems are upgradeable w/ most major brands of radios on the market, so you will never have to throw away your communication system because you decide to upgrade your radios at a later date.

 

Hope this helps, Happy 4th

[rabbit_diesel]

... My thought is the car makes a lot more RF noise at 5000 RPM than just off idle tooling around the paddock.

I think so too.

 

I don't remember off the top of my head, but I think they are solid.

Solid core ignition wires are well known to radiate lots of RF noise from an ignition system.

 

easy test- take the radio out of the car and start the car. bring the car up to RPM speed and then move the radio back towards the car... Does the radio start braking up when you move towards the car???

Good question, one I don't have the answer to. I'll try that.

This sounds like a good test.

 

Will

[Tom A]

This sounds like a good test.

I tried this Tuesday, it worked just fine. I sat in the car and held it at about 5000 RPMs, my partner started about 10 feet away and called his wife on the radio. He kept getting closer until he was leaning in the window, holding the radio where it is normally mounted. She had no problem hearing him, and he could hear her the whole time.

 

This is really frustrating.

[SRC/SampsonRacingComm.]

Hey Tom-

 

The good news is that your current radios will work w/ your current car no problem

 

The bad news it sounds like you are having a communication gear problems at this point.

 

Thoughts: get a incar NASCAR harness, PTT and a NASCAR helmet kit w/ ear buds. At that point, you will have good comm. between driver and crew at the least. Next item would be a racing crew headset w/ noise cancelling mic to match your drivers helmet systems.

[Tom A]

Thoughts: get a incar NASCAR harness, PTT and a NASCAR helmet kit w/ ear buds. At that point, you will have good comm. between driver and crew at the least. Next item would be a racing crew headset w/ noise cancelling mic to match your drivers helmet systems.

Thanks Shawn.

 

What is the difference between the NASCAR and the IMSA setups you list on your page? Is it just the connectors? Any reason to choose one over the other?

 

So for a bare minimum, I need:

Complete NASCAR(or IMSA) Flex Boom Helmet Kit, With Ear Buds $140

Car Harness $71

Car Harness to Radio $17

Velcro Mount PTT $40

 

I assume the ear buds double as hearing protection, is this correct?

 

Thanks,

[SRC/SampsonRacingComm.]

that will set you up for sure-

 

Go w/ the NASCAR as its a metal jack and plug for the incar set-up.

[Ev]

Another option is a MURS setup (google "murs radio").

 

They are 2 watts, have the ability to have an external antenna, no license required and are reasonably priced. I have seen Vertex VX-210 radios (about $100 on ebay) programmed to MURS frequencies work very well and since you can get all the headset/helmet goodies, they are great for racing.

[SRC/SampsonRacingComm.]

Please... what ever you do, try to stay w/ UHF. I think the MURS radios are only VHF.

Edited July 7, 2006 by Guest

[Eric J.]

This sounds like a good test.

I tried this Tuesday, it worked just fine. I sat in the car and held it at about 5000 RPMs, my partner started about 10 feet away and called his wife on the radio. He kept getting closer until he was leaning in the window, holding the radio where it is normally mounted. She had no problem hearing him, and he could hear her the whole time.

 

This is really frustrating.

 

While on the track you may be getting interference from other cars. Even if your car is reasonably quiet electrically, if you're next to somebody else that's generating a lot of noise you'll still have the problem.

 

Also, with unlicensed bands like GRMS uses it could be that the presence of other GRMS radios during an event is contributing to the problem. Have you tried changing channels when you are experiencing problems?

 

It sounds like the problem is either headset/key or interference related, and I'm betting it's interference. If you can't find a clean channel when you're experiencing interference then there isn't much else that can be done, other than switching to radios in quieter bands or licensed spectrum ($$).

[Ev]

Please... what ever you do, to stay w/ UHF. I think the MURS radios are only VHF.

Why do you say that?

 

According to my research, VHF is better for outdoor applications because the longer wave form can bend around objects and over hills. UHF is better indoors because it will go through walls and such better than VHF.

 

Here is just one link I found that says that http://www.49ercom.com/thumbnail.asp?offset=0&deep=1&cat_id=144 third FAQ down....

 

BTW, NASA MA and others I am an official for use VHF with no problems.

[SRC/SampsonRacingComm.]

maybe the size of a roof mount antenna, VHF vs. UHF... See the last sentance in that example-

[Eric J.]

According to my research, VHF is better for outdoor applications because the longer wave form can bend around objects and over hills. UHF is better indoors because it will go through walls and such better than VHF.

 

Here is just one link I found that says that http://www.49ercom.com/thumbnail.asp?offset=0&deep=1&cat_id=144 third FAQ down....

 

Yikes! Regardless of what that site says, material penetration (i.e., the ability to go through walls, tree leaves, etc.) generally gets better with increasing wavelength (decreasing frequency). This is partly why you're more likely to need an external antenna to pick up UHF TV stations than VHF.

 

But I don't think that's a problem in this case unless there are trees, buildings, etc., marginally in the way enough to make a difference. For the most part the difference between VHF and UHF isn't that great. Compared to 2.4GHz, 5GHz, or even 60GHz unlicensed bands VHF and UHF is cake, and the amount of transmit power allowed in VHF and UHF is pretty high relatively speaking.

[Ev]

According to my research, VHF is better for outdoor applications because the longer wave form can bend around objects and over hills. UHF is better indoors because it will go through walls and such better than VHF.

 

Here is just one link I found that says that http://www.49ercom.com/thumbnail.asp?offset=0&deep=1&cat_id=144 third FAQ down....

 

Yikes! Regardless of what that site says, material penetration (i.e., the ability to go through walls, tree leaves, etc.) generally gets better with increasing wavelength (decreasing frequency). This is partly why you're more likely to need an external antenna to pick up UHF TV stations than VHF.

 

But I don't think that's a problem in this case unless there are trees, buildings, etc., marginally in the way enough to make a difference. For the most part the difference between VHF and UHF isn't that great. Compared to 2.4GHz, 5GHz, or even 60GHz unlicensed bands VHF and UHF is cake, and the amount of transmit power allowed in VHF and UHF is pretty high relatively speaking.

I know little but what I read. I don't create the facts, I just pass them on. Here are some more sites that support VHF is better than UHF out doors.

http://www.benmeadows.com/refinfo/refinfopdfs/tech244.pdf

http://www.spcomm.com/faq.html

http://www.scoden.com/confusedport.htm

http://www.fisherwireless.com/faq.htm

 

I guess on flat land, there is little difference. In areas with rolling hills, VHF wins by just a small amount.

 

I think the point here is what ever you choose, you will get a working system. I still stand by my suggestion of the MURS radios. They are better than GMRS for the simple reason you can run an external antenna and don't have to secure a license and deal with the limitations to remain legal. GMRS at the track will work if the FCC doesn't complain (read the rules, you will see what I mean).

[SRC/SampsonRacingComm.]

you can also read the sky is falling...

 

There are other factors to look at but hey I'm just guy on a chat board w/ no PROFESSIONAL experience to draw from...

 

YES they both will do the job, just make sure you call a professional racing communications company with proper knowledge and find out which ones they offer (for your choice of racing) and why

 

Off to Willow Springs to run w/ NASA in the enduro car- have a great weekend

[Ev]

you can also read the sky is falling...

 

There are other factors to look at but hey I'm just guy on a chat board w/ no PROFESSIONAL experience to draw from...

 

YES they both will do the job, just make sure you call a professional racing communications company with proper knowledge and find out which ones they offer (for your choice of racing) and why

 

Off to Willow Springs to run w/ NASA in the enduro car- have a great weekend

 

I googled "the sky is falling" and only found fiction.

 

Is it better to listen to ONE persons "professional" opinion, or mutiple sources with a different opinion?

 

Best buy from Sampson, they know everything.

 

Have fun at willow..

[Boudy]

I certainly don't want to get tossed under the "he knows everything" bus but I'll try to help shed some additional light on the subject. UHF is the industry standard for racing communications. Who knows why, it just evolved that way. I can say that:

1) At the distances in question, I'd have to whip out a spectrum analyzer and map the RF footprint of the entire track to find a difference between UHF and VHF.

2) Itinerate frequencies are easy to obtain as it's common to license UHF itinerates for racing.

3) There is typically less noise floor at UHF in most areas. This alone would give you better performance.

 

On the subject of MURS, you are correct, they'll work fine for you. They do, however, have limitations:

1) No license required. That means if you show up at a track and there is chatter on all 5 of your channels, you're hosed for the event.

2) Limited to 2 watts. Even with a 3dB gain antenna, you'll probably have problems at some tracks.

3) It's non-standard so very few people have them. If you want to add a crew member or talk to another car, you'll have to buy additional radios. Nobody can loan you these because nobody else has them.

4) As UHF is standard, raceceivers and most scanners are set up for UHF. While NASA doesn't, some series and some tracks require you to monitor race control which is on UHF.

5) To expand your system with a car kit, harness, or nice headsets, you may have difficulty finding accessories to fit non-standard radios.

 

It's wise to purchase equipment that is upgradable without having to duplicate your investment later. General UHF/VHF recommendations are fine, however, Shawn is giving you application based recomendations. If you can live with the limitations, then MURS will be a good choice.

 

Hope that helps,

 

Boudy

[Eric J.]

Other times it has worked poorly, with the usual problem the driver can't transmit out of the car, but can receive.

 

Crap, I've had this backwards in my head the whole time.

 

If the problem is interference the affect is typically to reduce the sensitivity of the receiver closest to the interference. In other words, if it's the pit radio that can't receive, the problem is likely interference near the pit radio.

 

So the electrical noise in the car or near the car probably doesn't have much to do with it. Instead, be aware of what's around your pit radio. Relocating _that_ radio or changing channels may help the problem next time.

 

Are you running the car radio on batteries or jacked into the car power? The most likely way that it would be a problem with the transmitter is if you have a noisy power supply to the radio and it's distorting the transmitter.

[white_2kgt]

Well, I'm going to report on my radios now that I finally got a chance to use them. I have 2 Vertex Standards and 1 Tekk. I run one of the vertex's in car b/c of the external antenna hookup. At summit point this past weekend I could hear my crew around the entire track. One was stationed at Turn 10 and when I was at Turn 5 (furthest from each other and through trees, no hills) I could hear him, but there was some static. I have used GMRS radio's in the past (not in car, just around the track walking), and they don't even come close to reaching that far. I was very impressed by the UHF radio's.

 

On the earbuds. Get the big $$$ ones. I was using some cheap walkman earbuds and not only was it a PITA to get the helmet on w/o the falling out I couldn't really hear w/ the car at full song. On Sunday I picked up a set of the high dollar earbuds, these are like earplugs and earbuds all rolled into one, MUCH BETTER. I could hear my crew while blasting down the straight's.

 

Shaun, thanks for your help reprogramming that Tekk. I got a few useable channels which should work out just fine!

[Zee]

Given the amount of interest shown here for acquiring radio systems, I might be persuaded to part with mine.

 

I acquired my set up with the old ITB racer I just bought. The car needs some safety gear and a good going-over before it takes to the track. And I need personal safety gear before entering Comp school.

 

In short, it might be some time before I'd ever need this radio system, so, maybe someone who needs it sooner would like to buy it.

 

From memory, it is a 3-unit two-way/one-way system featuring three Uniden GMRS100 radios (one-mile range), three headsets, a helmet headset, in-car wiring with rooftop antenna and Tx bottom on steering wheel. Five NiCad batteries. Charger adapter. The incar wiring is simple to install and remove to sell along with the rest.

 

It was designed by Zander Radio Systems

 

http://www.zanderradiosystems.com/

 

At the time when purchased and installed, this system cost $940 before installation.

 

I estimate it would cost $1200 to reproduct it today.

 

Comes its own poly tote box, very rugged.

 

It is designes to provide 2-way communications between driver and Crew Chief, plus one-way fro driver to a second crew member, such as timekeeper.

 

If interested, post here for all to share in.

 

I'll get up some photos.