Using Magnum S-9 with a linear amplifier ?

[Pilsener]

I just got a linear amp (Zetagi B300P), which I intended to use with my Magnum S-9.
However, the manual for the amp says that input power should not exceed 10 W for AM/FM use.

How do you guys avoid blowing the input of your amps ?
I mean, even at the lowest power-setting, the Magnum can easily give 20 W (or more) on AM if I talk loud enough into the mic.

 

[freecell]

it's NOT A LINEAR AMPLIFIER.

 

[Pilsener]

It says so on the box, but who cares, really ?
Even YOU should know what kind of device I'm referring to.

 

[davegrantsr]

'How do you guys avoid blowing the input of your amps'-figure out what INPUT the amps' transistors will handle.....and apply no more. sure helps keeping mine from blowing up.

 

[Chop]

you'll prolly have to take it to a tech and have them detune the radio to drive the amp.

 

[freecell]

"Even YOU should know what kind of device I'm referring to."

just enough to steer people away from them. they're junk.
if you don't like the answers don't ask the questions.

 

[cbradiomagazine.com]

Those amps are basically right along the same lines as the RM products - the KL300P would be it's cousin with 2 x 1446's inside.

Generally I wouldn't suggest running a Magnum S-9 into a 2 x 1446 box unless it is detuned and not running at max.

Can you run it with that box - YES, but you'd need to make sure you only deadkey less than 1 watt and you wouldn't want to swing more than 25-30 watts into it - the magnums usually swing 35-40.

Ideally for that radio minimum you want a box with 2 x 2290's or 2 x 2879's in it.

Personally I would not run that combo as the amp will be getting it's ass kicked.

 

[Pilsener]

Thank you, cbradiomagazine.com.

Is there any easy mods for fixing the Magnum's output power ?

(My option B is to just use my other transmitter, so any extensive modding of the Magnum is out of the question.)

 

[freecell]

the S9 can be matched for proper drive into 2XSD1446's and idiot-proofed so that no overdrive situation is ever allowed to exist. no circuit modifications are required.

 

[Pilsener]

and idiot-proofed

Sounds nice.
I'm an idiot.
Any links ?

 

[bob85]

the kl300p is class c the b300p is unregulated class ab, its closest rm equivalent is the rm kl351p and kl400,
unlike rm the later 300p's have a simple low pass output matching network,
1w swinging 25-30w into a b300p lmao, there are less expensive ways of making smoke.

 

[mackmobile43]

Sounds nice.
I'm an idiot.
Any links ?

All of the adjustment pots are clearly marked inside the S-9 if you care to have a twittle.

With the radio power connected and the radio's antenna port connected to either an antenna or dummy load.
Rotate the rf power knob to full output, usually fully to the right.

With the speaker side of the radio removed you will adjust VR13 for high AM rf power limit .

With the RF power knob full left adjust VR-16 for low AM rf power limit.


Vr-12 is your SSB high power limit which you might consider reducing also so switch radio to SSB mode and with rf power knob full right adjust SSB high power for the max or min you would like.

You can tune your rig with or without the amp inline and functioning, your choice but if you have an idea of how much output you need from your radio this will not be necessary.

 

[freecell]

"You can tune your rig with or without the amp inline and functioning, your choice but if you have an idea of how much output you need from your radio this will not be necessary."

aye, there's the rub. better yet, you need to have an idea of how much output you need from the amplifier. in the high power position with unregulated bias the ideal would be @ or just under 180WPEP from 45W of carrier on AM and the same PEP for SSB operation. the transmitter should be adjusted with the rf power control in the maximum clockwise position to obtain these power levels so that the maximum drive values cannot be exceeded. AMC will have to be backed down to control PEP using 30 mv. (-18dbm) of microphone signal input with the mic gain wide open. that's the idiot-proof method.

(i was not implying that anyone in this thread was an idiot.)

since the SD1446's come in 6 different flavors, (beta-gain) J, K, L, M, N and O, attempting to determine just exactly what amount of carrier an pep are required by the transmitter to produce the numbers above is almost impossible without making adjustments with the amplifier inline and operating.

in addition, you don't want to make any of these adjustments into an antenna system unless you know with all certainty that the load represented by the antenna is as equal to Z=50, X=0 as possible if you want any accuracy at all from your power/watt meter.

the 10W AM/FM drive rating for the amplifier mentioned earlier is best and most accurately interpreted as 10WPEP (Modulated) AM, 10WCarrier FM. a review of the POut VS. PIn Graph for the SD1446 operating @ 30Mhz. makes this rather clear.

 

[Pilsener]

But can't the "swing" feature be disabled, so it will only transmit with deadkey power at AM ?

 

[freecell]

i'm afraid i don't understand the question.