5kW Mobile tube or solid-state?

[Mustang 131]

I'm inclined to think that either 50V LDMOS or a tube is the way to go and not 12V or volting them higher that 14 for long term reliability and reasonable IMD numbers. Nomad, there is a faily big difference between average and peak power draw and with a brace of decent AGM or Lithiums and a capacitor or three they will I'm sure keep voltage droop to a minimum on speech peaks. Sideband is relatively easy on mobile power supplies as compared to balls to wall class C, over-driven, over volted AM.
So is there just a low voltage primary winding on such a mobile Dahl or is there some black magic in the windings?

Unit 148

Just a 3 phase step up xfmr.

 

[Shadetree Mechanic]

What I want to know is how does a step up transformer work on DC power? Or is connected to the alternator before the rectifier? In which case, no amount of extra batteries will help.

 

[2NC995]

how does a step up transformer work on DC power?

They don't. A transformer on DC is direct short.

"Alternator" literally means alternating current generator. Our car alternators generate 3 phase AC power.

We think of them as DC simply because in auto applications (nowadays) they have built-in rectifiers.

 

[2NC995]

Also, outside passenger cars you run into alternators with AC taps, or with no internal rectifiers at all.

In other words, you hit the nail on the head.

 

[Mustang 131]

What I want to know is how does a step up transformer work on DC power? Or is connected to the alternator before the rectifier? In which case, no amount of extra batteries will help.

3 phase

http://www.extremecb.com/2_250.htm

 

[peterwo2e]

I currently run an old 8 x Toshiba 2879 mobile amplifier which will be shortly going to a new home.

I would like to step up to the next level in mobile power. Mobile power supply is not a problem as can add alternators and or batteries as required.

I operate mainly on sideband so will use an AB amp.

Would you look at a solid-state or tube amplifier? Either way I would like a high gain unit so I do not have to have boxes driving boxes.

I have up to 100W pep drive and would like a clean 5kW+ pep output

Unit 148

wow $$$$

 

[Phantom Wolf]

Solid

 

[Phantom Wolf]

Solid state linear

 

[linearone]

Once you try to build a proper 32 pill mobile going ac makes alot of sense. Especially with the pills nowadays.
There is loads of trapped potential in an alternator once you make it unregulated and tap the ac. If you have never run ac you just have no idea what can be done . One alt on an ac box can make soooo much more power soooooo much eaiser than a pile of dc alts. The power comes so easy so fast you will sit there being mad that you ever did anything else. I mean shit, guys ran them in chevettes and mustangs right @Mustang 131 ?

 

[Phantom Wolf]

Either will do

 

[Enterprise312ok]

Once you try to build a proper 32 pill mobile going ac makes alot of sense. Especially with the pills nowadays.
There is loads of trapped potential in an alternator once you make it unregulated and tap the ac. If you have never run ac you just have no idea what can be done . One alt on an ac box can make soooo much more power soooooo much eaiser than a pile of dc alts. The power comes so easy so fast you will sit there being mad that you ever did anything else. I mean shit, guys ran them in chevettes and mustangs right @Mustang 131 ?

I know you have a big mobile @linearone What are you running?

 

[linearone]

I know you have a big mobile @linearone What are you running?

Had a 3000, now ive got a 6000. Thinking of changing to two 3000s. My daily driver is working on getting a 3 tube 3-500z

 

[nomadradio]

3 tube 3-500z

Just don't drive them hard enough to break the spot weld on a grid wire. The loose wire end is less a hazard in a base amplifier. If the loose end of a grid wire gets jostled and touches either the plate or grid, bad news for the other two tubes.

Maybe.

Far likelier in a mobile.

73

 

[buickid]

Anything like a 3CX3000A7 is going to require just as much drive since the gain is similar and then you have to worry about where your RPM's are when you key and unkey. Forget seeing any power at an idle too. The number of large tetrode mobile amplifiers I've seen successfully built are one, by Wolf many years ago. That's about as rare as a hens tooth.

Never run AC mobile, probably never will. I think I understand RPMs affect the plate voltage, but why when you key and unkey? Is it because of the loading and unloading of the alternator/engine?

 

[Shockwave]

Never run AC mobile, probably never will. I think I understand RPMs affect the plate voltage, but why when you key and unkey? Is it because of the loading and unloading of the alternator/engine?

You are correct. The unloaded plate voltage will typically be much higher than the loaded plate voltage. You want to bring the RPMs up, only after the load is applied. The most critical part is when you unkey and remove the load. You want to be off of the throttle before you unkey the microphone otherwise the possibility of a large voltage Spike exists. Most of these systems are not voltage regulated and the ones that are, still experience what's called overshoot when the load is removed. That causes a brief voltage Spike which tends to take out rectifier diodes and capacitors. There are ways to avoid this like installing a large choke in the DC line however, the whole system is a bit of an inconvenience to operate.