## Black Cat Amplifier 1*Likes* | |
01-09-2011, 09:22 AM
| Senior Member | | Join Date: Jul 2006 Location: 6000 feet above the Mojave Desert, Tehachapi, Ca
Posts: 481
| | Quote:
Originally Posted by **n0zna** on a real wt meter like a Drake w4 or a Bird and see what they realy do...hehe 74s de n0zna/John |
Comparing the Drake to a Bird is like comparing a Kenwood to a Cobra.
--Toll_Free |
01-23-2011, 07:34 AM
| Member | | Join Date: Apr 2010
Posts: 81
| | This is the same one he is selling but the lettering was not all there but thanks for the web site .... |
01-24-2011, 03:02 PM
| Senior Member | | Join Date: Aug 2008
Posts: 2,260
| | The 300 is really more of a model number not a wattage number. When you sell them though they sell better when you call em a 300 watter and point to the number on the front. |
01-25-2011, 10:53 AM
| Senior Member | | Join Date: Jul 2006 Location: 6000 feet above the Mojave Desert, Tehachapi, Ca
Posts: 481
| | Quote:
Originally Posted by **9C1Driver** The 300 is really more of a model number not a wattage number. When you sell them though they sell better when you call em a 300 watter and point to the number on the front. | No, they really do pull about 300 watts peak from the power supply. It IS a wattage number, most CBers are just not educated as to the difference between input and output power.
Hence them believing an SB220 should swing to 2 grand, as well.
--Toll_Free |
01-26-2011, 09:08 AM
| Senior Member | | Join Date: Dec 2010
Posts: 320
| | My legal limit amp makes a little over 5 amps of rf. Quote:
Originally Posted by **Toll_Free** After reading your last post, I'm telling you to do a little research, learn about input power, output power, efficiency, etc.
It's a bit more complicated than me throwing a couple sentences at you.
BUT, since you stated you'd have no use for such information, I can tell you have NO idea about how an amplifier works. They aren't rated in amps.. They are rated in watts.
--Toll_Free | |
01-26-2011, 09:23 AM
| Senior Member | | Join Date: Jul 2006 Location: 6000 feet above the Mojave Desert, Tehachapi, Ca
Posts: 481
| | Quote:
Originally Posted by **Kamikaze** My legal limit amp makes a little over 5 amps of rf. | That's a statement that doesn't make any sense..... Even if you're talking about it at 50 ohms, it's only 1250 watts of RF output. 1500 is the legal limit.
I can measure my 4CX5000A output amplifier with a 5A meter, too. Of course, I'm only putting 5 amps into a 600 ohm ladder line.
5 amps at 600 ohms is 15 grand output. 5 amps at 50 ohms is only 1250.
Stating your amplifier makes 5 amps is a worthless number, since it's not referenced to anything. Is that into a dummy load, a reactive load, etc?
I'm NOT trying to be an ass here, I know what you're saying, I believe, I just want OTHER people who might pull up this thread in the future to realize, just because you can state ONE number doesn't mean anything.
5 amps of RF can be 100 watts, 1000 watts, 15,000 watts or 150,000 watts. You need to know either the voltage at that point, or the TRUE resistance (or 'normalized resistance', which is a complex math formula to get there, but it basically takes the R (+/-) j and turns it into a straight R number, so you can plug it into ohms law and get a reading.
I hope that helps people understand. The OTHER thing that matters is that an AMMETER is ONLY accurate at 50 ohms. As SOON as you enter any reactance, it requires a lot of math to figure out where you're REALLY at. That means, if you move the ammeter (just like an SWR meter) in the feedline, you can change the amount of RF amps it shows... IE, in my 600 ohm feeders, I can move the ammeter 20 feet in either direction, and it will show BIG differences in the induced current: Which makes sense, an Ammeter is ONLY a voltmeter calibrated across a known precision value shunt.
--Toll_Free |
01-26-2011, 10:53 AM
| Senior Member | | Join Date: Dec 2010
Posts: 320
| | Everyone in the world uses an amplifier normalized into 50 ohms. Every type accepted ham amp made is 50 ohms source impedance. Same for every radio.
This isn't 1945.
I said a little over 5 amps. Please read carefully net time. Even less than 5 amps steady state can be 1500 watts P.E.P. on amps with marginal headroom. Since an Rf ammeter will not show fast peaks one experienced with this device will assume carrier conditions.
I'm not trying to be anything here. Just sayin'
An rf ammeter ignores reactance so scratch that off the list.
If your running 600 ohm feeders and are not terminating them with 600 ohms YOUR 5 amp reading is not going to tell much about power out. Almost nobody used 600 ohm transmission line terminated by 600 ohms. Do you? Your tuner matches the antenna system, not the feedline.
What the heck is TRUE resistance. The word true is pretty scary. Are you talking about the resistive portion of an impedance. What formula. Yes, it must be complicated.
You only have a 4CX5000? Quote:
Originally Posted by **Toll_Free** That's a statement that doesn't make any sense..... Even if you're talking about it at 50 ohms, it's only 1250 watts of RF output. 1500 is the legal limit.
I can measure my 4CX5000A output amplifier with a 5A meter, too. Of course, I'm only putting 5 amps into a 600 ohm ladder line.
5 amps at 600 ohms is 15 grand output. 5 amps at 50 ohms is only 1250.
Stating your amplifier makes 5 amps is a worthless number, since it's not referenced to anything. Is that into a dummy load, a reactive load, etc?
I'm NOT trying to be an ass here, I know what you're saying, I believe, I just want OTHER people who might pull up this thread in the future to realize, just because you can state ONE number doesn't mean anything.
5 amps of RF can be 100 watts, 1000 watts, 15,000 watts or 150,000 watts. You need to know either the voltage at that point, or the TRUE resistance (or 'normalized resistance', which is a complex math formula to get there, but it basically takes the R (+/-) j and turns it into a straight R number, so you can plug it into ohms law and get a reading.
I hope that helps people understand. The OTHER thing that matters is that an AMMETER is ONLY accurate at 50 ohms. As SOON as you enter any reactance, it requires a lot of math to figure out where you're REALLY at. That means, if you move the ammeter (just like an SWR meter) in the feedline, you can change the amount of RF amps it shows... IE, in my 600 ohm feeders, I can move the ammeter 20 feet in either direction, and it will show BIG differences in the induced current: Which makes sense, an Ammeter is ONLY a voltmeter calibrated across a known precision value shunt.
--Toll_Free | |
01-26-2011, 12:03 PM
| Senior Member | | Join Date: Jul 2006 Location: 6000 feet above the Mojave Desert, Tehachapi, Ca
Posts: 481
| | Quote:
Originally Posted by **Kamikaze** Everyone in the world uses an amplifier normalized into 50 ohms. Every type accepted ham amp made is 50 ohms source impedance. Same for every radio.
This isn't 1945.
I said a little over 5 amps. Please read carefully net time. Even less than 5 amps steady state can be 1500 watts P.E.P. on amps with marginal headroom. Since an Rf ammeter will not show fast peaks one experienced with this device will assume carrier conditions.
I'm not trying to be anything here. Just sayin'
An rf ammeter ignores reactance so scratch that off the list.
If your running 600 ohm feeders and are not terminating them with 600 ohms YOUR 5 amp reading is not going to tell much about power out. Almost nobody used 600 ohm transmission line terminated by 600 ohms. Do you? Your tuner matches the antenna system, not the feedline.
What the heck is TRUE resistance. The word true is pretty scary. Are you talking about the resistive portion of an impedance. What formula. Yes, it must be complicated.
You only have a 4CX5000? | 1. Not everyone uses 50 ohm stuff. CBers use 50 ohm stuff, lots of appliance operators use it, and people lucky enough to have the $$$s to put up a resonant antenna for every band, then coax feed it... Or those lucky enough for the property, etc. Myself, I'm lucky enough to have 11 acres, so I play with all KINDS of antennas. As such, OWL works BEST for me, since I don't have to worry about building a matching network. I know of PLENTY of people that DON'T. HOWEVER, it was brought into the discussion to show how an ammeter is NOT the panacea that some proclaim, as well as for those NOT that involved in electronics to realize that placement, AND impedance plays a difference in what it reads.
Complex impedance (you know, the -/+ j numbers) WILL cause ammeters to show a different reading, because they CHANGE the voltage minima and maxima. The ammeter is NOT a directional device, so if you are at a current MAXIMA for the reverse power being reflected, then you're NOT measuring Pout. Moving a ammeter, like a wattmeter, WILL cause the readings to change. This is COMPOUNDED when their is ANY reflected power (read this as reactance on the line)...... If their is no reactance at the feedpoint, no reactance on the line. Just because the METER isn't effected by reactance doesn't mean the MEASUREMENT POINT isn't effected as well. The basic accuracy of the meter isn't changed, but by measuring it at anything other than a current maxima on the forward, and current MINIMA on the reflected will you be anywhere near accurate. Or, use a dummy load.
No, all my antennas are NOT 600 ohms. I never said they where, and I also stated that if you moved the ammeter in the 600 or the 50 ohms line it would change the reading.
WTF is your 1945 comment about? People don't use OWL anymore? Tell that to The Wireman, AES, HRO, etc. that deal in open wire, ladder and window line. There is a time and place for everything...... Not to mention balun mfgs, tuner mfgs, etc.
True resistance is the R part of the complex impedance. Normalized impedance is the impedance presented, taking the reactance out of the equation. IE, 40 ohms antenna +j10 would appear nearly as a 1:1, but it is NOT 1:1, and depending on where you measure it, it will change... AND cause the voltages maxima / minima (and current) to change along the feedline.
My 4CX5000 is the driver. It hits the grid of a 3CX30,000. HOWEVER, I'm considering offing that box and going to a pair of 10's or 15s, tetrode, push pull and link coupled to 4 inch line. HOWEVER, it's your power company that decides HOW 10-8 you can be, and I've learned mine won't be powering the big box here... I CAN get 3 phase, but they only want to put up 3X10KVA xformers. WTF?
I wasn't trying to jab you at all. I was trying to show people that DIDN'T understand how things can be skewed, as well a stating you have 5 amps of RF being meaningless because who knows what the impedance is, or the voltage at the measurement point is. Just as I pointed out, and you repointed out, if you change the position of the ammeter on the feedline (OWL or coaxial ), it's going to change / skew the readings.
Have a good day!
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