Hi,
What's all this business I hear people talking about blasting people's
car stereos or killing cars altogether with high-power RF? I run 2m,
10m, and 11m in my jeep and I'd like to sort out the fact from the
legend and find out what kind of power I can use without risking
damage to my jeep or cars around me. At what power level is front-end
overload to a nearby radio likely? At what power level is damage
likely, and to what componets?

I am currently using only 50 watts on a 5/8 wave (2m), 25w on a 1/4
wave (10m), legal 4w on a 1/4 wave (11m)

Thanks,
Nelson KE5MBX

"KE5MBX" wrote in message
ups.com...
Hi,
What's all this business I hear people talking about blasting people's
car stereos or killing cars altogether with high-power RF? I run 2m,
10m, and 11m in my jeep and I'd like to sort out the fact from the
legend and find out what kind of power I can use without risking
damage to my jeep or cars around me. At what power level is front-end
overload to a nearby radio likely? At what power level is damage
likely, and to what componets?

I am currently using only 50 watts on a 5/8 wave (2m), 25w on a 1/4
wave (10m), legal 4w on a 1/4 wave (11m)

Thanks,
Nelson KE5MBX


I think over 100W you may have problems with HF and VHF. It can be a
problem.

One thing that works real well is to transmit near the x-ray radar band
where you have privileges. The traffic may slow down a bit as you set off
the radar detectors :-)

Stefan Wolfe wrote:
One thing that works real well is to transmit near the x-ray radar band
where you have privileges. The traffic may slow down a bit as you set off
the radar detectors :-)

A number of years ago (I forget exactly what year) a
ham friend of mine discovered that he could cause a
new Cadillac to stall simply by keying his transmitter
as the Cadillac was passing his camper. That design
problem was probably fixed rather quickly.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote in
et:

Stefan Wolfe wrote:
One thing that works real well is to transmit near the x-ray radar
band where you have privileges. The traffic may slow down a bit as
you set off the radar detectors :-)

A number of years ago (I forget exactly what year) a
ham friend of mine discovered that he could cause a
new Cadillac to stall simply by keying his transmitter
as the Cadillac was passing his camper. That design
problem was probably fixed rather quickly.

Back in the '70s I was working on a project that saw me reading papers on
the effects of EMR on various things. Amongst the papers was one dealing
with the susceptibility of the electronic anti-skid technology introduced
on heavy transport vehicles to meet (then) newer more stingent braking
distances. The braking systems were susceptible to ingress of RF,
resulting in wheel lockups. You can imagine the results of a 22 wheeler
at highway speed when a chook alongside comes up with "Breaker, Breaker,
any taker?" and locks up most of the wheels on the transport. I read
other papers on rear wheel lockups in a certain brand of passenger
vehicle due to RF induced downshift of the (electronically controlled)
automatic transmission at highway speeds.

The EMC issue seems better understood by vehicle manufacturers today,
though you still hear of RF triggered airbag deployments from time to
time.

I won't go into the papers on effects on aircraft, some of you may fly
from time to time! A paper on propagation of EM waves through rectangular
slots in thin sheet metal looks innocuous enough until you realise that
it is talking about an aircraft window (in the days when almost all
aircraft had a metal skin).

Owen

Dear Owen: Well do I remember the onset of EMC awareness that came with
the early anti-skid systems. One horror case took place in Chicago with a
bus. One of the many short bridges in Chicago has metal decking and a bus
stop at the far end of the bridge. The bridge also is aligned with the
Sears tower (in downtown Chicago it is difficult not to be aligned with some
strong RF radiator - it is worse than a carrier). Bus starts onto the
bridge. Patrons stand to get off at the next stop. Breaks fail while on
bridge. Driver fully asserts the brakes. Bus arrives at the end of the
bridge and the brakes start to work. People go flying.

I was a witness of the (very early and crude) method used to test
systems. Not anymore! Today, whole cars are zapped from all directions,
all frequencies, and at huge amplitudes. A huge effort was made to find out
what sort of signals a car might encounter. I once rode in a van all the
way to Chicago glued to a SA to record strong signals. The worst that I saw
was a VOR signal (few hundred watts at ground level with a very good radial
screen and near the road) and a CB signal. Others in the project measured
at VOA and LORAN sites. An FM broadcast antenna was found to radiate a huge
signal onto a public street - see, you know that antenna design would be
worked into the discussion - in this case an incompetent, but not unusual,
antenna design.

At work, we have a big RF amplifier used to zap devices in order to find
out where they die. Had to get a waiver from FCC because, even though the
amp requires three-phase, it could be used on 27 MHz.

Critical equipment is much more EMC capable today.

73, Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Owen Duffy" wrote in message
...
Cecil Moore wrote in
et:

Stefan Wolfe wrote:
One thing that works real well is to transmit near the x-ray radar
band where you have privileges. The traffic may slow down a bit as
you set off the radar detectors :-)

A number of years ago (I forget exactly what year) a
ham friend of mine discovered that he could cause a
new Cadillac to stall simply by keying his transmitter
as the Cadillac was passing his camper. That design
problem was probably fixed rather quickly.

Back in the '70s I was working on a project that saw me reading papers on
the effects of EMR on various things. Amongst the papers was one dealing
with the susceptibility of the electronic anti-skid technology introduced
on heavy transport vehicles to meet (then) newer more stingent braking
distances. The braking systems were susceptible to ingress of RF,
resulting in wheel lockups. You can imagine the results of a 22 wheeler
at highway speed when a chook alongside comes up with "Breaker, Breaker,
any taker?" and locks up most of the wheels on the transport. I read
other papers on rear wheel lockups in a certain brand of passenger
vehicle due to RF induced downshift of the (electronically controlled)
automatic transmission at highway speeds.

The EMC issue seems better understood by vehicle manufacturers today,
though you still hear of RF triggered airbag deployments from time to
time.

I won't go into the papers on effects on aircraft, some of you may fly
from time to time! A paper on propagation of EM waves through rectangular
slots in thin sheet metal looks innocuous enough until you realise that
it is talking about an aircraft window (in the days when almost all
aircraft had a metal skin).

Owen

Owen is right-- When a radio-man , had a guy come
into the shop, complaining about his truck
stalling when he transmitted. (freq around 160
MHz) Ran his truck, (idle), keyed rig, NO
Problem! Said to take it for test run- in low
gear, (abt. 2000-2500 rpm), and keyed the
transmitter, the rig STALLED! Wasn't a problem
when I installed radio- turned out they had
modified the truck to an Electronic Ignition!
This around 25 years ago. Tried various cures
but, they went back to the original "Points &
coil" system and worked fine! (this before these
were common on vehicles). Translation: YES, can
effect a vehicle, but times have changed: might
not be so supsceptable now a days (more problems
with the built in computer that they seem to
like to hide-- drill a hole in these- turn a car
into a thrashing machine! ). But BOTH can cause
problems. btw the power level for the problem was
a 50 Watt radio. and the SECOND problem (think
they more standardized now), could be placed
as the manufacturers stated, (ANYWHERE in the
vehicle) ! Now days must be within 3 foot of the
OBD2 Plug (used for smogging)! At least in the
U.S. As info, Jim NN7K

Owen Duffy wrote:
That design
problem was probably fixed rather quickly.

Back in the '70s I was working on a project that saw me reading papers on
the effects of EMR on various things. Amongst the papers was one dealing
with the susceptibility of the electronic anti-skid technology introduced
on heavy transport vehicles to meet (then) newer more stingent braking
distances. The braking systems were susceptible to ingress of RF,
resulting in wheel lockups. You can imagine the results of a 22 wheeler
at highway speed when a chook alongside comes up with "Breaker, Breaker,
any taker?" and locks up most of the wheels on the transport. I read
other papers on rear wheel lockups in a certain brand of passenger
vehicle due to RF induced downshift of the (electronically controlled)
automatic transmission at highway speeds.

The EMC issue seems better understood by vehicle manufacturers today,
though you still hear of RF triggered airbag deployments from time to
time.

I've heard that as well with Japanese cars. I think the computer gets
RFI'd out and shuts down the ignition system. Maybe something for the
Mythbusters TV show to check out...

Scott



Cecil Moore wrote:

Stefan Wolfe wrote:

One thing that works real well is to transmit near the x-ray radar
band where you have privileges. The traffic may slow down a bit as you
set off the radar detectors :-)


A number of years ago (I forget exactly what year) a
ham friend of mine discovered that he could cause a
new Cadillac to stall simply by keying his transmitter
as the Cadillac was passing his camper. That design
problem was probably fixed rather quickly.

On Feb 12, 5:50 pm, "Stefan Wolfe" wrote:
"KE5MBX" wrote in message

ups.com...

Hi,
What's all this business I hear people talking about blasting people's
car stereos or killing cars altogether with high-power RF? I run 2m,
10m, and 11m in my jeep and I'd like to sort out the fact from the
legend and find out what kind of power I can use without risking
damage to my jeep or cars around me. At what power level is front-end
overload to a nearby radio likely? At what power level is damage
likely, and to what componets?

I am currently using only 50 watts on a 5/8 wave (2m), 25w on a 1/4
wave (10m), legal 4w on a 1/4 wave (11m)

Thanks,
Nelson KE5MBX

I think over 100W you may have problems with HF and VHF. It can be a
problem.

One thing that works real well is to transmit near the x-ray radar band
where you have privileges. The traffic may slow down a bit as you set off
the radar detectors :-)

Where the heck do you get a 3cm transmitter, though? ha.

On Feb 12, 5:15 pm, "KE5MBX" wrote:
On Feb 12, 5:50 pm, "Stefan Wolfe" wrote:



"KE5MBX" wrote in message

oups.com...

Hi,
What's all this business I hear people talking about blasting people's
car stereos or killing cars altogether with high-power RF? I run 2m,
10m, and 11m in my jeep and I'd like to sort out the fact from the
legend and find out what kind of power I can use without risking
damage to my jeep or cars around me. At what power level is front-end
overload to a nearby radio likely? At what power level is damage
likely, and to what componets?

I am currently using only 50 watts on a 5/8 wave (2m), 25w on a 1/4
wave (10m), legal 4w on a 1/4 wave (11m)

Thanks,
Nelson KE5MBX

I think over 100W you may have problems with HF and VHF. It can be a
problem.

One thing that works real well is to transmit near the x-ray radar band
where you have privileges. The traffic may slow down a bit as you set off
the radar detectors :-)

Where the heck do you get a 3cm transmitter, though? ha.

10.525 GHz is an amateur band, and is the same band used by the X-band
radars, and transmitters are readily available for $100. Gunnplexers
are one example, but people also use modified "microwave door openers"
to experiment in X band.

Uh, not quite. While the X Band police radars are at 10.525 GHz, the
ham band is only from 10.000 to 10.500 GHz. Plus, pulse modulation is
not allowed on the 3cm band. We CAN use MCW, phone, image, RTTY, data,
SS, and test modulations. Hmmm, I wonder about plain old vanilla CW???
I don't see it mentioned...maybe "data" covers that nowadays (and with
a bandwidth limit of 100 KHz, we could smoke along at a LOT of WPM!!).

Scott
N0EDV

wrote:





10.525 GHz is an amateur band, and is the same band used by the X-band
radars, and transmitters are readily available for $100. Gunnplexers
are one example, but people also use modified "microwave door openers"
to experiment in X band.