O.K. I have done a test on my power supply a Mega-Watt switching 33amp for use on my base station to power alone a RM Italy KL-503 running behind a Cobra 148GTL Malaysia "Brand new old stock a real find" Anyway I am getting readings of nearly 500 watts with forward swing on several different meters all reading the same I know something doesn't sound right so I wanted to see if I could get even more watts possibly my power supply was inadequate so I hooked up my linear alone to a portable jump start box and then checked my watt meter with the KL-503 on max setting 225 watt max reading now OK so maybe the jump box might be weak it is a couple of years old so I have a fairly new truck battery being stored right now fully charged a top of the line battery with 1000 cca about the max in batteries so I again hook up the KL-503 alone to the battery and I get the same exact watt reading again 225 watts on max setting. Now I tend to believe the 225 watt reading but how is this possible that I get such a higher watt meter reading from my power supply I don't believe I am getting more power but why do the meters show this 500 watt reading when linear is powered by the power supply?
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250 watt difference btwn power supply&battery?
- Thread starter hammer0630
- Start date
I think you need to keep in mind a couple of things here:
*Cheap meters aren't dependable. You noticed all by yourself that there was a variation. There is also another factor about meters, called meter deflection. if you whistle into the mic and make it swing quickly, it is the inertia of the needle that will cause it to keep traveling beyond a real reading. Most readings are taken with a steady tone from a signal generator. Or using an even, continuous, and steady single tone whistle for 4-5 seconds and let the needle stabilize.
*You cannot test amp power thru an antenna/meter. It is done with a 50 ohm dummy load that can operate for 3-5 seconds - like a 100 watt dummy load will do. Antennas have reactive resistance; dummy loads do not. That will change the outcome.
*You cannot get 500 watts from 33 amps @ 13.8 volts; the results are skewed due to the first two factors mentioned above. Maybe 33 amps @ 18 volts; but you wouldn't want to do that. Things go 'south' real fast that way.
*Cheap meters aren't dependable. You noticed all by yourself that there was a variation. There is also another factor about meters, called meter deflection. if you whistle into the mic and make it swing quickly, it is the inertia of the needle that will cause it to keep traveling beyond a real reading. Most readings are taken with a steady tone from a signal generator. Or using an even, continuous, and steady single tone whistle for 4-5 seconds and let the needle stabilize.
*You cannot test amp power thru an antenna/meter. It is done with a 50 ohm dummy load that can operate for 3-5 seconds - like a 100 watt dummy load will do. Antennas have reactive resistance; dummy loads do not. That will change the outcome.
*You cannot get 500 watts from 33 amps @ 13.8 volts; the results are skewed due to the first two factors mentioned above. Maybe 33 amps @ 18 volts; but you wouldn't want to do that. Things go 'south' real fast that way.
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Well 33 amps at 13.8 volts is about 455 watts and since most amps are about 50 % efficient I would say that that it would make about 225-250 watts out on that supply.While it is possible to get a bit more power from a power supply as they are normally 13.8 volts and not 12 volts like a battery is, you would not gain that much to see 500 watts.
500 watts OUTPUT will require almost 1000 watts DC INPUT which is about 72 amps at 13.8 volts. No way a 33 amp supply will do that.
Hi Hammer, I don't think you will see 500 watts out @ 33amps 13.8 volts? SSB, Butt I never say never, the watteg increase is do to higher volteg out of the power supply, on my meters i see 400 to 425 watt's pep ssb 15.5 volts droping to 14.5 at 45 amps load into a 1kw load, the pills are 4xMRF492, good luck, Scott.
What I am trying to show is that when I power my KL-503 I get a reading on am dk. 480 watts from my 33 amp swithching power supply: note only the KL-503 is powered by the power supply alone. Second test is powering my KL-503 to a fully charged 1000cca truck battery and getting a more realistic wattage reading of 225 watt dk. The only item tested are the power supply powering the KL-503 amp and getting a 480 watt dk. reading. And then testing the KL-503 powered by a 1000cca truck batterey and then getting a 225 watt reading dk. I believe the 225 watt reading when powered by the batterey is a correct reading of wattage but my question of why am I getting a 480 watt dk when powering the KL-503 with my 33 amp power supply and then getting a wattage reading of 225 watt dk. when powered by a truck battery fully charged? My Cobra 148GTL is powered alone with a different power supply. I believe it would be accurate to say my wattage reading of 225 watt output when powered by a very capable truck battery is an accurate reading of wattage produced by a RM Italy KL-503. How is it possible that a different source of power (33amp switching power supply) to the amplifier would give me a false higher reading of wattage?
I would question your test methods once again.
Dummy load OR antenna?
You cannot trust the antenna as a load in a test; you need to use a dummy load.
You are testing this with a battery and a power supply and you are seeing a huge variation. It is impossible to see that many watts out of that amp on AM (see specs below). It would FRY before it gave you those figures.
http://dd182003.wordpress.com/2011/01/12/another-amp-to-look-at/
RM Italy KL-503:
Input power AM 1-6 W
Input power SSB 2-12 W PEP Max
Output power AM 250 W Max
Output power SSB 450 W PEP Max
BTW - This amp doesn't use two 'pill' type bipolar transistors. It uses nine IRF-520n MOSFET devices instead (one driving eight). Very cheap to build or fix this amp; as these devices sell for about ~$3/ea. One could probably buy ten of these IRF's for about $25 if need be. Not a bad idea; just don't know how this amp sounds on air. They are capable of ~35 watts/ea peak watts. So; 280 watts is all anyone could expect from them - depending on the quality of the heat sink. After that, it is all smoke. In this case - snap, crackle, and pop . . .
Dummy load OR antenna?
You cannot trust the antenna as a load in a test; you need to use a dummy load.
You are testing this with a battery and a power supply and you are seeing a huge variation. It is impossible to see that many watts out of that amp on AM (see specs below). It would FRY before it gave you those figures.
http://dd182003.wordpress.com/2011/01/12/another-amp-to-look-at/
RM Italy KL-503:
Input power AM 1-6 W
Input power SSB 2-12 W PEP Max
Output power AM 250 W Max
Output power SSB 450 W PEP Max
BTW - This amp doesn't use two 'pill' type bipolar transistors. It uses nine IRF-520n MOSFET devices instead (one driving eight). Very cheap to build or fix this amp; as these devices sell for about ~$3/ea. One could probably buy ten of these IRF's for about $25 if need be. Not a bad idea; just don't know how this amp sounds on air. They are capable of ~35 watts/ea peak watts. So; 280 watts is all anyone could expect from them - depending on the quality of the heat sink. After that, it is all smoke. In this case - snap, crackle, and pop . . .
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Hi Hammer, All i can say is the incrase in watteg is do to the incrase in volteg out of the power supply. why you have seemingly unbelievable DK watts AM is anybody's guess. as Robb said test methods? one thing i would do is turn down my dial a watt before i let the smoke out of my box Tell you figure it out. Scott.
I hope your post is a mis-print. Are you getting 225 and 480 watt AM DEAD KEY READINGS? If so that is way way beyond what that amp is supposed to do.
Yes I am getting a 480 watt dead key reading when the KL-503 is powered by a 33 amp switching power supply. Now with out changing anything except taking the KL-503 power leads and hooking them up to a 1000cca truck battery which has way more amps and power than my power supply has I get a more realistic dead key reading of 225 watts. My Cobra 148GTL is set to 2 watts dead key. This KL-503 has hours of talk time it never gets hot but I am running two 5X5 fans for cooling. What I am saying is I don't believe it is producing 480 watts am but why am I getting this false reading (480 watts dk) when my KL-503 is powered by my 33amp switching power supply? And this truck battery shows a voltage reading of 14.2 And it would seem that even with out a dummy load that just by using a different power source only whether the wattage reading may be inaccurate that they would be similar. I was just trying to see if my power supply was adequate to fully power the KL-503 and I do not own a more powerful supply so I used one of the most powerful truck batteries made I mean think about it this battery could power my radio, amp,stereo and amp, multi halogen lights, heater fan,and even more electrical demands all at the same time and still turn over a V/8 engine try to find a power supply that could do that but yet I get a 225 watt reading when powering my amp off of it which I believe is the correct wattage output this is very close to what the specs are from RM Italy. How a power supply can lead to a false wattage reading I thought was interesting and makes me wonder about how many false readings are out there that people believe are correct and wouldn't believe else wise because of the equipment they use and the brand names etc.
It really is irrelevant what he is using for a load if the only thing that changes is the power source. If you are looking for 100% true readings then yes you should use a dummy load however for comparative testing it means nothing.
What happens to the output voltage of the power supply when the amp is keyed? Some power supplies will go nuts in the presence of a strong RF field and the regulator will not function properly. The usual result is that the voltage goes sky high. I have a Tripplite PR-40a linear type power supply that has the ability to remote sense the output voltage. I found out the hard way that this sense line is quite prone to RFI in the right conditions. I accidently ran the voltage sense wires too close to the antenna tuner and when I keyed the radio the meter lights went super bright and the radio shut down. The shut down was due to over voltage. The power supply was loosing regulation and the voltage was shooting from 13.8 volts up to the pre-regulator voltage of 22 volts. I fixed that issue in a hurry. Perhaps your power supply is doing the same thing. Stick a volt meter on it and see or if you don't have a volt meter use a 12 volt light and watch the brightness of it.
Very sensible reply, I also think this is a rf by product I can't imagine what else it could be? I would have loved to get 480 watts dk out of this amp and be able to power this with only a 33amp supply what is also interesting is there is no indication of anything wrong, every key down same precise readings day in day out if I didn't use this truck battery I would have never known. I got this high reading with a different watt meter also! I am going to try your idea also. I power my 148GTL with a separate regulated power supply I forget the name But is well known and uses a transformer. I do not know if I am doing any damage to the KL-503 but it runs so cool it is hard to believe but I am running two 5x5 fans mounted to it also.
Sounds like your meters are reading high, but what you described with the power supply vs. charger/battery scenarios sounds correct.
Those megawatt power supplies work pretty well, I've now had mine for 6 months with almost full time use and it's still working perfectly. They are cheaply assembled but for the price I'm impressed, no noise, solid power.
Those megawatt power supplies work pretty well, I've now had mine for 6 months with almost full time use and it's still working perfectly. They are cheaply assembled but for the price I'm impressed, no noise, solid power.
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