RADAR set gurus please

[Opcom]

I'm trying to figure out the average and peak ERP my RADAR on 9415MHz. I'm really only interested in the second case since that is where the average power goes up.

The general specs are:
It has a peak power of 1500W.
V beamwidth 25 deg
H beamwidth 6 deg
sidelobes @ -21db


case 1: close range settings:
pulse of 0.08uS / repetition of 2250Hz
duty cycle 0.00018
avg power 0.27W


case 2: long range settings:
pulsed of 0.5uS / repetition of 750Hz
duty cycle 0.000375
avg power 0.5625W

Do the antenna beamwidths give me the power gain of 864x (29.36 dB)?

My reasoning is that there are 360 degrees Horizontal and 360 degrees Vertical. The area is divided into 129600 square degrees. The beamwidth occupies 150 of these degrees, or 1/864 of the total area.

1. (360 degrees * 360 degrees) / (25 degrees * 6 degrees) = (129600 / 150) = 864
    meaning all the power is concentrated into 1/864 of the total spherical area

2. power ratio of 864 = voltage ratio of 29.39
   sqrt 864 = 29.39 for the voltage ratio

3. voltage ratio of 29.39 = power gain of 29.36 dB

So, taking the second case, of avg power 0.5625W, the average ERP is 0.5625W * 864 = 486W,
and the peak power of 1500W makes the ERP 1.29MW. - that does not sound right, but maybe due to the big number. It is still only 1/2 watt average.

Finally,
can anyone tell me the emission type? what a mess that might be..

assuming a 1MHz bandwidth for the magnetron.. actually the FCC said to list only the center frequency in my application and never mind the bandwidth, but the first section is mandatory in the emission designation.

1M00P0N--

1M00 - 1 MHz bandwidth

P0N - a simple pulsed signal carrying no information.

-- the last characters don't apply, since there is no muxing or information carrying or other shennanigans going on.

I should state that I highly doubt the magnetron is that narrow. It's probably a few MHz wide, the spec in the book says 9415 +/-30MHz.

Thanks for any comments.

[K3ZS]

Looks like the system bandwidth in case 1 is 12.5 MHz (1/PW) and case 2 would be 2 MHz.  Your antenna gain seems OK relative to isotropic, not relative to a dipole.    The magnetron spec is probably its frequency accuracy or slow frequency drift, the receiver must either be manually peaked or have an AFC to track the transmitter. 
It has been quite a while since I designed and developed radar systems but that is what I recall, my books are packed away in my garage somewhere.
The average and duty cycle calculates to the peak power you stated of 1500W in case 2.

[Opcom]

Thanks very much! The FCC wants to know the ERP. They don't state if it is versus isotropic or vs a dipole. I guess I need to figure out that difference.

[K3ZS]

Usually the antenna efficiency is around 50% so your erp would roughly be about 1/2.
The only way is to measure the antenna gain and compare to the calculated aperature gain.    With radar antennas, the reflector is usually under illuminated by the beam width of the feed antenna.   This lowers the gain but lowers sidelobe levels and radiation leakage
around the reflector.    If you state your erp at about 50% you would be close enough for government work.

[K3ZS]

What is your radar by the way.    At the power and frequency, it seems like an aircraft or ship weather avoidance radar.

[K3ZS]

In radar the gain is usually referred to as isotropic which would be aperature gain reduced by the antenna efficiency.    Another factor is the reflectors construction tolerance, wave guide loss from the transmitter to the feedhorn but these usually don't add up to much.

[Opcom]

The RADAR is a Raytheon R10X on 9415 MHz. Peak power is 1500W. It is a unit from a boat. The range is 16 miles radius. Seems to be OK on that, I was seeing buildings and stuff out to 9-12 miles when I took it out to the country to test it. I can't legally operate it on land without a license specifically for that. I need to show the the FCC that it is supporting my business because apparently they don't just allow anyone with $265 to get a license.. I am working on that at the moment. This is real crude but is a start. http://www.radartruck.com/

The unit uses a patch antenna made of a pc board. Since the V beamwidth is 25 degrees, half of it is hitting the ground and this needs to be raised in elevation in order to look for rain and hail. I need to tilt the patch antenna back about 10-12 degrees so the machine looks mostly at the horizon and above. This is a little challenge. I am not sure if it should be done with a machined shim wedge or with some educated bending of the array mounting brackets and the piece of wire that takes the RF from the probe in the center of the waveguide and carries it to the array. I would hate to mess up the matching and not have a way to tell. I should take pics of this area, as it is too hard to describe.

[K3ZS]

That is an interesting use for the radar truck.   Most of my work was for the armed services through research projects at Penn State U.    We usually got experimental licenses for the radars we developed because we built them from parts and claimed an educational use for the completed units.   The last one I developed was a Doppler radar at 94 GHz.    It had a three foot dish, at 3 mm wavelength it had a gain around 60 dB.    The dish had to be made to almost optical precision at that wavelength.    It was the first millimeter Doppler radar to have a real time FFT spectral processor.    We could see precip and clouds with it.   That is what it was for, a cloud radar.    Using the technology, a similar unit is now running on a satellite, except no FFT processor.

http://www.nasa.gov/mission_pages/cloudsat/main/index.html