Rm Italy KL-503 watts vs amps

[Slowmover]

I know this is an old thread but....would upgrading from a 203p to a 503 be worth it?

I’ve changed from a KL203P velcroed to a Uniden 880 or 885 installed in my Petebilts provided overhead location, to a KL7505v installed in a radio carrier that sits on the passenger seat.

203 was 70W (with 1-reflected) on MFJ 945 mobile Tuner in a co-phase setup (FL Cascadia), to bench test notes showing 180w (and up depending on 3-position power) with the 7505 with variable power on a 99v2 Galaxy set at 2.25w

12A fused to 30A fused (change).

Accessing power and running coax today’s job on this 579 Pete during a 34-hour HOS “re-set” while on the road (Cullman, in Alabammy)

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[Batteryman]

Typical RM rating IOW bullshit rating. They typically rate something at nearly twice what it will put out. The big clue is the fuse rating. Mulitply the fuse rating by 13.8 volts and then divide that result by two and you will be close to the actual power output. That amp draws 30 amps so 30 x 13.8= 414 watts 414/2 = 207 watts which is more inline with reality. A typical 100 watt ham transceiver requires about 20 amps of current. Some need 25 amps. Getting 450 watts with just 30 amps draw absolutely defies the laws of physics since it would require the amp to be MORE than 100% efficient. RM is one of the worst for overstating ratings however most CB amp manufacturers do the same thing.

My RM Italy KL503HD ( high drive version) puts out 450 watts max PEP on SSB and draws only 30 amps ( checked with a certified Fluke meter).

 

[kopcicle]

So, let's review
30A x 13.8 Volts = 414
414÷2 = 450 watts max PEP on SSB

 

[Cutlass327]

I have allway got 250 avg and 400ish peak on my kl503 however just blew transistors by keying up before remembering i disconnected my antenna due to lightning.

Might I recommend a dummy load? Disconnect antenna, connect to dummy load. May take a while to figure out why no receive, but is will save on $$$ parts burning out.

 

[loosecannon]

So, let's review
30A x 13.8 Volts = 414
414÷2 = 450 watts max PEP on SSB

and that's not even taking amplifier class efficiency into account!
LC

 

[KD2GOE]

and that's not even taking amplifier class efficiency into account!
LC

like a Class D audio AMP ROFL

 

[El Kabong]

Anyone know what the "new version" of the 503 has new about it? This is not the high drive version.

Thanks!

 

[CbRadiosPRONTO]

There’s a high drive version???

 

[El Kabong]

There’s a high drive version???

Yes. There is.

 

[davev8]

So, let's review
30A x 13.8 Volts = 414
414÷2 = 450 watts max PEP on SSB

then you have to divide by 2 again as rf amps are only about 50% efficient ...1/2 of the power is heat hence the big heat sink ...so about 225w

 

[Big Kahuna]

I'm testing a KL 7505 right now 4 x 455 (60 watt) and output is around 200-220 driven with 1 watt deadkey 12 watt swing.

On high setting - 1 watt in 60 watt deadkey / 10 watt swing around 200 watts.

I did test 2 watts in and it keyed 100 watts so no way I'd run more than a 1 watt deadkey into a KL7505.

 

[Slowmover]

I'm testing a KL 7505 right now 4 x 455 (60 watt) and output is around 200-220 driven with 1 watt deadkey 12 watt swing.

On high setting - 1 watt in 60 watt deadkey / 10 watt swing around 200 watts.

I did test 2 watts in and it keyed 100 watts so no way I'd run more than a 1 watt deadkey into a KL7505.

Had these on the bench at Clays 01/19:

Radio (Galaxy 99v2)
Low setting on a Galaxy 99v2
2.25w, swing 15w
(High: 15w, to 30w; not used)

Amp (RM ITALY KL-7505)
Low: 40w, to 180w
Med: 80W, to 225w
High: 125W, to 250w

Used it this way while mobile for several months. Double that of a KL203. I wanted over 100w with a margin.

Set the radio to lowest.
Set the amp to lowest.
Just fine.

The install was the pain. Potential amp draw + voltage loss led to use of 4-AWG cable. Must have weighed 30# due to near 30’ length. Coax another near 30’. Past $200 DIY.

Will go into my pickup where the install is pretty much permanent (versus big truck I don’t own).
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[9C1Driver]

And all that for maybe 1/2 of an S unit increase over the kl203.

 

[Big Kahuna]

125w carrier swinging 250 is not what I’d recommend for running that amp. I’m surprised clays set it up like that.

 

[Slowmover]

125w carrier swinging 250 is not what I’d recommend for running that amp. I’m surprised clays set it up like that.

A bench check. Didn’t actually “set” anything.