2 kw radarbeam

[Aron Tvedt]

There is something I dont understand about radars. I have a JRC 1500 radar
(16 miles), in according to the manual, the antenna is supposed to send out
a radarbeam of 2000 watt. My engines (yanmar 4lha htp) generator produses
12v 80A (1120watt).

I dont use the radar all the time, but if I did, would the engine be able to
produse enough power to my batteries?

Some experienced sailors say my radar cannot have an effect of 2000watt. It
is the same effect of an electical owen.

 

[Dennis Pogson]

There is something I dont understand about radars. I have a JRC 1500
radar (16 miles), in according to the manual, the antenna is supposed
to send out a radarbeam of 2000 watt. My engines (yanmar 4lha htp)
generator produses 12v 80A (1120watt).

I dont use the radar all the time, but if I did, would the engine be
able to produse enough power to my batteries?

Some experienced sailors say my radar cannot have an effect of
2000watt. It is the same effect of an electical owen.

Surely it depends on the voltage at which the 2KW beam is generated?
Remove "nospam" from return address.

 

[Grumpy]

Also consider that the radar sends a pulse of a couple of microseconds so
it's not continuous power drain.

Regards
Al

 

[Aron Tvedt]

aha, Amp=W/V?

Surely it depends on the voltage at which the 2KW beam is generated?
Remove "nospam" from return address.

 

[phil]

Your radar is only transmitting 2000 watts for a very short time, maybe a
microsecond. It also is only transmitting for less than maybe 1% of the
time, so the average power at 1% would only be 12 watts.

 

[phil]

doh....20 watts

Your radar is only transmitting 2000 watts for a very short time, maybe a
microsecond. It also is only transmitting for less than maybe 1% of the
time, so the average power at 1% would only be 12 watts.


able

 

[Peter Bennett]

There is something I dont understand about radars. I have a JRC 1500 radar
(16 miles), in according to the manual, the antenna is supposed to send out
a radarbeam of 2000 watt. My engines (yanmar 4lha htp) generator produses
12v 80A (1120watt).

I dont use the radar all the time, but if I did, would the engine be able to
produse enough power to my batteries?

Some experienced sailors say my radar cannot have an effect of 2000watt. It
is the same effect of an electical owen.

Radar uses a pulsed transmission, and the advertised power is the peak
power during a pulse. Since a radar actually transmits for much less
than 1% of the time, the average power consumption is much less than
1% of the advertised power - for one 2KW radar I had, I calculated
that the average power used by the transmitter was only 1 watt! The
fuse in the power feed to that set was only 2.1 amps, and I could run
the radar for hours on a sailboat (while sailing) with no concern
about running out of power.

Most radars will use more power for the display, and to turn the
antenna, that for the transmitter.


--
Peter Bennett, VE7CEI
peterbb (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

 

[Glenn Ashmore]

THe JRC 1500 has three pulse widths. The fastest is .08uS (.00000008
second) at 2,250 Hz (.000444 second). That means the pulse is about
1/5550 of the cycle. The slowest is .8 uS at 600 Hz or about 1/2000 of
a cycle. Most of the rest of the time a capacitor/inductor circuit
stores up power at a low rate and then blast it out all at one time.

There is something I dont understand about radars. I have a JRC 1500 radar
(16 miles), in according to the manual, the antenna is supposed to send out
a radarbeam of 2000 watt. My engines (yanmar 4lha htp) generator produses
12v 80A (1120watt).

I dont use the radar all the time, but if I did, would the engine be able to
produse enough power to my batteries?

Some experienced sailors say my radar cannot have an effect of 2000watt. It
is the same effect of an electical owen.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

 

[SB]

I work on weather radars that have up to 250kiloWatts out.
this is a peak value.
with the pulse widths we use it's actually only an average of 120Watts or so
out.

Now, don't think that since you have 200W speakers and are safe standing in
front of them, that you are safe sitting in front of your 20W (average)
radar. Just a note for safety...exposure times and all.....

 

[Aron Tvedt]

Yes, I am very aware of that after standing on the deck fishing. Forgot
about the radar, and got a headace. It got away when I switched it off.
thanks

 

[SB]

Do these little guys use magnetrons??

not much for power....would this use some sort of tube??

 

[SB]

What 'primes' the magnetron on these systems?

A maggie will do the work at ampin up the input and all, but I thought there
was a certain threshold you had to achieve before it could to it's work
properly.
In some of our old systems we used thyrtrons to bring up the power a bit
(volts/current?? not sure) and then the maggie would jack it up and kick it
out.

The cavity of our maggies can be adjusted for the frequency you are putting
out, but we also have some external compnents that assist with that and with
the firing rate.
We've gone completely solid state in a black box...so that's a s much as I
know about it!! haha

Fun stuff though! I used to have to shave my head....might be age...or
exposure...but if I keep working on these I won't have to anymore. OH, and
my tan as gotten a lot better! j/k

 

[Bruce in Alaska]

Do these little guys use magnetrons??

not much for power....would this use some sort of tube??

ALL small boat Radars use Magnitrons.
Yes, they are a Vacumn tube.

Bruce in alaska

 

[Bruce in Alaska]

The cavity of our maggies can be adjusted for the frequency you are putting
out, but we also have some external compnents that assist with that and with
the firing rate.

Variable Frequency Magnitorns are not allowed in the Maritime Mobile
Radio Service in the USA. All of the Type Accepted Radars in the US
use fixed Frequency Magnitrons.

Bruce in alaska

 

[engsol]

Question:

In the days of yore, did early marine radars ever use klystrons? We used them
in (very) early microwave communications systems. They were a bear to
keep on frequency, and didn't last long.

Maggies are interesting devices. If you've ever torn one apart, it mostly
looks like a machined hunk of steel, which in fact it is, and surprisingly small.
The magnets account for most of the weight.

As to power, I recall that our airborne radar had a peak power output of
2 megaWatts, but the maggie current was only 18 - 20 milliamps. Of course the
high voltage was 20 kV.

What kind of maggie power supply (voltage & current) is normally found in small
marine radars these days?

Norm

 

[Bruce in Alaska]

Question:

In the days of yore, did early marine radars ever use klystrons? We used them
in (very) early microwave communications systems. They were a bear to
keep on frequency, and didn't last long.

Maggies are interesting devices. If you've ever torn one apart, it mostly
looks like a machined hunk of steel, which in fact it is, and surprisingly
small.
The magnets account for most of the weight.

As to power, I recall that our airborne radar had a peak power output of
2 megaWatts, but the maggie current was only 18 - 20 milliamps. Of course
the
high voltage was 20 kV.

What kind of maggie power supply (voltage & current) is normally found in
small
marine radars these days?

Norm

Back before Gunn Diode LO's, all radars used Klystrons as Receiver LO's.
All the early Commercial Radars that came on the market after WWII used
Klystrons as receiver LO's. 2K25 comes to mind but don't hold me to
that.

Now days the radar receivers use LNA/MMIC's for FrontEnds with intergrile
solidstate LO's driving Double Balanced Active Mixers. This is why
Radars these days can see 48 and 72 miles with less than 6Kw Maggies.
Back in the bad old days it took 20 and sometimes 40Kw to see out 72
miles, because the receivers were KLystron feed Crystal Diode Mixers
with Sky High Noise Figures.

Receivers have become orders of Magnitude more sensitive than 2nd and 3rd
generation receivers of the 70's and 80's. Your Tax dollars at work.
(US MIlitary Electronics Development Dollars)

V and A for common Maggies are in the 2Kv- 3Kv range with peak currents
of an amp, and up to 2 amps PEAK. This all compes from the Pulse
Forming Network that is usually feed by a switching powersupply up in
the T/R Pan that runs on 10-40 VDC Ships Mains, or some such variation
of Power supply for the Radar. 9M502 and 9M503 come to mind for common
3-5 Kw maggies, with the old 2J42 for the 9 - 10 Kw versions. Haven't
kept up on the state of the art for the last 7 or so years, but the
basic's haven't changed all that much in the Tx side of the Antenna Pan.

Bruce in alaska

 

[engsol]

Back before Gunn Diode LO's, all radars used Klystrons as Receiver LO's.
All the early Commercial Radars that came on the market after WWII used
Klystrons as receiver LO's. 2K25 comes to mind but don't hold me to
that.

Now days the radar receivers use LNA/MMIC's for FrontEnds with intergrile
solidstate LO's driving Double Balanced Active Mixers. This is why
Radars these days can see 48 and 72 miles with less than 6Kw Maggies.
Back in the bad old days it took 20 and sometimes 40Kw to see out 72
miles, because the receivers were KLystron feed Crystal Diode Mixers
with Sky High Noise Figures.

Receivers have become orders of Magnitude more sensitive than 2nd and 3rd
generation receivers of the 70's and 80's. Your Tax dollars at work.
(US MIlitary Electronics Development Dollars)

V and A for common Maggies are in the 2Kv- 3Kv range with peak currents
of an amp, and up to 2 amps PEAK. This all compes from the Pulse
Forming Network that is usually feed by a switching powersupply up in
the T/R Pan that runs on 10-40 VDC Ships Mains, or some such variation
of Power supply for the Radar. 9M502 and 9M503 come to mind for common
3-5 Kw maggies, with the old 2J42 for the 9 - 10 Kw versions. Haven't
kept up on the state of the art for the last 7 or so years, but the
basic's haven't changed all that much in the Tx side of the Antenna Pan.

Bruce in alaska

Thanks much Bruce...very helpful info. And I forgot about those diode mixers
in the rx front end. 1N34? Was that the one?
Norm

 

[Bruce in Alaska]

Thanks much Bruce...very helpful info. And I forgot about those diode mixers
in the rx front end. 1N34? Was that the one?
Norm

Yep, 1N34, 1N34A, 1N914, 1N415A, B ,C and E just to name a few.

Bruce in alaska

 

[Bruce in Alaska]

protected by a gas tube

That had a tiny bit of Strontium 90 in it to set a bias
for the Ionization of the T/R tube. Couldn't just toss
those Bad Boys in the trash, as they were a Radiation
Hazard if the were broke open.

Bruce in alaska

 

[SB]

Be aware that both regulation agencies in Canada and the US have
de-regulated certain amounts of radioactive material.

Our TR-limiters at work were de-regulated. We didn't have to worry about
signage or breakage (leave the room for the day if you're worried). As far
as I know they could be toss in the dump. I don't htink you could
incinerate them though (don't know about that!).

sb