FatBoy 1x4 input "dead key"?

[The Jerk]

What would be a starting/minimum radio dead key for a 1x4 FatBoy with all 2879s?

We've got one, and the radio has about a 2 watt dead key on our meter. When benched everything worked fine (maybe higher voltage?), but installed; the dead key from the amp slowly rises from about 10 watts to around 30 watts...it swings to around 600 watts (on a loose meter).

I'm assuming we have too little deadkey, and that's what's causing our issues? The amp swings fine, and gets good radio checks.

 

[mackmobile43]

Possibly your radio is seeing a higher than acceptable input swr from the amp so you may want to put the meter inline before the amp with a halfwave of coax and have the meter as close to the radio as possible via a double male barrel connector.

Anything above 1.5 to 1.7 is unacceptable to me.

As for a drive input to the amp, as much as it takes to give you a 150 carrier from the amp unmodulated if you're truly seeing 600 watts pep on maximum output from the amp which is about normal for 4/2879's at 13.8 volts or so.

 

[The Jerk]

I did a quick check, using the radio's SWR meter as a guide...the SWR does not change from unpowered to powered. I get a 1.3:1 SWR with the radios meter, and I get 1.1:1 on an actual SWR meter actually two of them).

Not saying the radio's SWR meter is anywhere close to accurate, but it should show a change if there was a problem?

 

[mackmobile43]

I did a quick check, using the radio's SWR meter as a guide...the SWR does not change from unpowered to powered. I get a 1.3:1 SWR with the radios meter, and I get 1.1:1 on an actual SWR meter actually two of them).

Not saying the radio's SWR meter is anywhere close to accurate, but it should show a change if there was a problem?

Did you recalibrate your radios swr meter with the amp inline and powered up>?

If you trust your radios readings then you're not trying to find the true answer to your delema .

 

[The Jerk]

Did you recalibrate your radios swr meter with the amp inline and powered up>?

If you trust your radios readings then you're not trying to find the true answer to your delema .

I did recalibrate once I turned the amp on...

No, I don't trust the radio's meter reading; but it can be used as a guide...I would have expected to see a big jump between the before and after readings.

 

[BOOTY MONSTER]

the final four 2879's are go0d for about 500 watts and still being fairly clean and not splattering across the band , and they dont need a driver . put a power meter behind the radio and adjusts the radios deak key a and the amps gain to get the amp to dead key about 125 watts and swing 50 watts .

 

[W5LZ]

Think about it for a minute.
An amplifier used in AM mode has no idea what 'dead key' as compared to 'swing' is. It only knows that it's being fed an input that's either okay or too much. Another aspect of it is if you have diddled the modulation at all, changed that 'normal' ratio of 'dead key' to 'swing', then using a 'dead key' as a tuning power level will tell you nothing about what the max 'swing' will be/should be/ought to be.
So what do you do, or what should you do? Try tuning for maximum power input (swing) rather than 'dead key' and adjust the amount of input power to suit the particular amplifier you are "tuning" for. Okay, so how do you do that? You use a constant level tone to do that tuning. That does not mean your voice, it's never constant. Maybe the most common 'tone generator' available to the average person is a simple dial tone from a telephone. (The average voice tones won't get you into the right city, much less the right ball-park!)
The simple fact of the matter is that under-driving a solid state amplifier does very little, or no harm. Over-driving a solid state amplifier will have bad results. If you aren't capable of adjusting that solid state amplifier ("no tune") you will never get maximum efficiency except by pure accident.
If you're going to do it, why not try doing it right?
- 'Doc

 

[The Jerk]

The problem is, we have almost no dead key from the Amp...our current deadkey/swing ratio is 30/600-ish. We are simply trying to get the deadkey/swing from the amp to a more normal 1/4 ratio.

We are not trying to reach that magical 1k watts stated by FatBoy...

 

[mackmobile43]

The problem is, we have almost no dead key from the Amp...our current deadkey/swing ratio is 30/600-ish. We are simply trying to get the deadkey/swing from the amp to a more normal 1/4 ratio.

We are not trying to reach that magical 1k watts stated by FatBoy...

TRY ANOTHER RADIO

 

[The Jerk]

That's the current plan...we are going to use my DX959 as it has a tad more output and a variable.

 

[555]

even xforce and davemade claim to have magical numbers

for 1 a 2879s into a 4-2879s box
why?
2nd a cobra 25 or 29 into a 2290 will even oversaturate a 4pill 2879s if not setup right
so why a 2879s then a underpowered radio to drive a 2879
so
its all out of whack to start or it might have been whacked

 

[mackmobile43]

That's the current plan...we are going to use my DX959 as it has a tad more output and a variable.

 

[The Jerk]

Hooked up my DX959...we turn the variable so that we were seeing between 100 and 125 watts, and the 959 will swing to a little more than 400, which is perfectly fine by me. This is without the truck running (battery voltage).

The SWR jumps from 1.2 to 1.5 after amp, and stays 1.2 between the amp and radio. This is recalibrating for the amp on.

The key here is a SINGLE watt...the first radio was showing a fixed 2 watts while the 959 is set to 3 watts to get the amp to deadkey 100-125 watts. Any lower and nothing.

 

[The Jerk]

so why a 2879s then a underpowered radio to drive a 2879


so its all out of whack to start or it might have been whacked

I figure its a matter of stocking less components?

BTW, its a brand spanking new amp...just bought last week. I was told it would be a 2290 driver, but it arrived a 2879 driver.

 

[mackmobile43]

Hooked up my DX959...we turn the variable so that we were seeing between 100 and 125 watts, and the 959 will swing to a little more than 400, which is perfectly fine by me. This is without the truck running (battery voltage).

The SWR jumps from 1.2 to 1.5 after amp, and stays 1.2 between the amp and radio. This is recalibrating for the amp on.

The key here is a SINGLE watt...the first radio was showing a fixed 2 watts while the 959 is set to 3 watts to get the amp to deadkey 100-125 watts. Any lower and nothing.

Then the amp probably needs at least 3 watts to turn the amps relay on, there is a sniffer cap at the input socket of the amp that excites the keying transistor of the amps key circuit and depending on which value cap is used there dictates the amount of input from the radio to accomplish that task.

As for the swr jumping with the amp on there is no way to recalibrate the swr meter to compensate for the amps input without recalibrating the meter when the amp is in use and it may still rise while modulating and at what you've stated I wouldn't give it a second thought.