When I lived in Mooresville NC and worked in the industry, we were affiliated with Racing Electronic's. RE
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Working in an environment where most everything is encouraged to be made smaller and smaller - they actually bought into the idea of using a YAGI antenna on the pit box because of all the problems with the UHF frequencies and traveling from town to town and the fact that some tracks are quite large in size.
My suggestion to you is to buy quality products from quality distributors and forget about most anything sold in the Radio Jap.
Racing Radio's is also a good source for any of your communications needs.
If this race is a one time deal, I would suggest that you rent a couple of raceceivers with all the frequencies pre programmed.
The nice thing about them is - you can get one radio or two radios which will have the head sets and boom mic's so you can listen to your favorite teams and yet carry on a conversation between two people sitting in the stands.
A place like Charlotte or Bristol - if you don't have a radio like that - forget trying to have a conversation with the person sitting next to you during the race. Plus it also protects your hearing. If you look at the prices of these set ups - they are quite expensive to purchase.
They will ship them to your house a few days before the race and you can use them as you please and then a couple of days after the race - you send them back and there is only a slight fee for using them for a whole week.
If you have a problem - they usually have a tent set up at the track and they can exchange the broken radio for a different one for no charge.
Or you can take your own quality scanner to the track and they will download the frequencies into your scanner for you - for a price.
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In the long run, it is a lot cheaper to either have them program your radio for you or rent you a radio then what it is for you to buy your own radios - for a one time ordeal or try to program them manually - because the frequencies change from track to track.
At times there is conflicts between some of the teams radio frequencies and locally used frequencies - garbage trucks, local trucking companies, utility companies etc - and that is the reason why they sometimes have to change their operating frequencies from track to track.