Mayf,
I have always admired your knack for introducing subjects that are stored in
boxes marked "Pandora". LOL... Below are some of our many lessons
learned on this subject. They may not be perfectly accurate but they seem
to serve us well:
First, the salt plays havoc with certain radio spectrum and the "advertised"
distance of various radios will not even be close. I do not know why this
is, but is sure seems to be true.
There are two types of applicable radio spectrum - "business licensed" (the
FM radios used by police, lumber yards, BNI, etc.) and "public use" (CB,
MURS, FRS/GMRS). Since "business licensed" cost money and require compliance
documentation, etc. we choose to leave this spectrum to the likes of the
SCTA/BNI. Although it should be noted that you can rent radios & spectrum
from reputable race radio shops, we still place this in the expensive
category. In addition, there are other publicly licensed spectrum for things
like Amateur radio, 900Mhz phones, etc. but again they are not applicable to
most racers. We have noted that all of these are in use at Bonneville by one
group or another.
Of the applicable public spectrum:
-CB1 - HF range(~27 Mhz) @ ~ 5 watts pr/handheld
-MURS or CB2 - VHF range @ ~ 5watts (~151 Mhz range) pr/handheld
-FRS/GMRS - UHF range @ either .5 watt (FRS) or 5 watts handheld/50 watts
GRMS (~460Mhz) mobile & base respectfully. This band also has some other
benefits and restrictions.
The ubiquitous CB1 "hugs the earth" and therefore travels the farthest.
The down side is it requires a very large antenna, is very prone to skip and
other interference as can be seen I the number of times a day BNI has to
change the channel. Additionally, radios both mobile and handheld are not
generally designed for headsets and may suffer from a lack of ruggedness.
Because of the low frequency, they are also the most susceptible to engine
[electrical] noise making them not so practical for a race car. However,
with work it could be done.
CB2 or MURS is a VHF band that can use just about any commercial or surplus
VHF radio. We used military/law enforcement surplus radios for a few years
and reprogramed them to the MURS channels in hopes we would have the range
of the CB but with the privacy of little used spectrum. Unfortunately this
experiment did not work well. They were fine around the starting line, but
would only carry a couple of miles. Ultimately the issue with our CB2 setup
was lack of proper antennas. Again like CB1, the CB2 VHF band is a very
long wave length and requires a reasonably long antenna to work well. Since
this is not practical on handhelds or race cars, and we loss most of our
signal in the car do to distance between the antenna and the lower powered
radio (5w), we gave up on this band.
FRS/GMRS is the newest of the bands to be used. Many people use the FRS
radios and they will work for sometimes up to a mile. Since FRS radios must
have permanently fixed antennas and are limited in wattage to 1/2 watt, they
are great for the starting line or at a theme park, but not so practical for
bouncing the full length of the course.
This leaves GMRS. GMRS is FRS on steroids. It is intended for family's to
talk via handhelds, mobiles and base stations at reasonable distances - just
like the business bands. Radios can have detachable antennas so you can
have a high gain antenna on your vehicle roof, transmission power of up to
50 watts for vehicles and base stations and most importantly, repeaters are
allowed just like business band. Last year we noticed that there were many
teams running GMRS - the most traffic I had heard on this band in one place
ever. Without the repeater, we carried about half the course with our
radios. This year well will have a GMRS repeater in the center of the pits
and anyone using our pair of frequencies should be able to carry the course.
I should note that this band dose require a FCC license for GMRS at about
$85 which is good for 5 years. Radios are available new or surplus at
reasonable costs.
I have rambled on to long for sure...
John
569
-----Original Message-----
From: land-speed-bounces@autox.team.net
[mailto:land-speed-bounces@autox.team.net] On Behalf Of Larry Mayfield
Sent: Wednesday, January 18, 2012 10:46 AM
To: land-speed@autox.team.net
Subject: [Land-speed] IN Car Communications
Many times when I am ou watchng cars and not in line waiting my turn, I hear
the tow crew come on the CB line with comments like the driver reports he
lost the motor or blew a tire or some other disaster in the run downrange.
My question is: How does the driver talk to the crew in the tow truck? I can
see big utility in having an in car comm system to notify the tow that
something is amiss but I have never looked to see
what could and can be used. I can also see where a peer to peer ad hoc
network on the salt might also be helpful for data gathering and
communication as well.
So, I'd like to hear from any and all about their systems in car and in pit
and tow that they might have. I think I would like to invest in one also if
I don't have to rob the main Chinese bank (ours don't have any money,
lol)...
Comments? Thoughts?
mayf
--
______________________________
drmayf
Worlds Fastest Sunbeam, period.
204.913 mph flying mile
210.779 mph exit speed
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