How feasible would it be.....

[kopcicle]

"Dirt" comes from a variety of sources.
power supply
overdrive
bias
VSWR mismatch
linearity

Basically there are two areas other than power supply (under/over volt, poor regulation) that create crud.

IMD is in band, near transmitted frequency.
or
Harmonic energy at multiples of frequency.
First deal with harmonic energy.

Unfortunately any discussion about IMD (inter-modulation distortion) leads back to linearity first then falls rapidly into an esoteric black hole of advanced mathematics or endless cut, fit, try, (it's the English way...).

What I'm suggesting is that application and design go hand in hand with device characteristics. I can go deeper into this but if you want to go ahead on your own , compare input-output graphs for popular transistors. What you're looking for is a nearly straight line. There will be some surprises. Hint, I really like the 2SC2290.

Some non-linearity can be straightened out with negative feedback networks. Lately a process "pre-distortion" inputs non-linear gain to the input in order to create a linear transfer function.

 

[Shockwave]

Do MOSFETS have the same characteristics as the old "pills" do? By which I mean the ungodly interference to everything in a 20 mile radius or are they cleaner? I know the radio tune has practically everything to do with that as well but from my experience, the pills were just dirty on their own. I would LOVE to have 700 W that was so clean that unless you were right beside me, you'd never get any bleeding one channel up or down.

Once you move up from 12 volts, higher voltage MOSFET's typically have a cleaner signal output than 12 volt bipolar devices with respect to IMD. Stay stuck on 12 volts and use re-branded switching transistors, marketed towards 11 meters and the "dirt" quickly appears. Even though they look similar, there is a world of difference between the "ERF" line and parts like the NXP MRF300 that Kopcicle has posted about. I'm also a fan of running higher voltage MOSFET's in the vehicle with an AC inverter.

The biggest contributor to "bleedover" on 11 meters is the result of over-modulation on the negative peaks which produces negative peak RF cutoff. Using an old school radio "upgraded" with a MOSFET final that has not been properly re-biased, is a disaster in this area although it looks good with the "swing" on the watt meter. Leave ALC and AMC intact at all times. When needed, adjust or modify the circuit to provide the desired range without hitting negative peak cutoff or flat topping on SSB.

One last note. If your negative peaks are consistently stronger than your positive peaks and the transmitter carrier is correctly set, you may see this situation completely invert itself by simply reversing the two wires on a non polarized microphone element in order to flip the phase for AM use!

 

[Handy Andy]

Got an old Cougar?



They used to run a specialty laminated windshield that used a separate power system to heat the windshield to melt snow ice and clear fog without the use of Heater Defroster or AC - the system used a separate Alternator without the Diode Trio and generated AC current thru two electrodes embedded in that glass sheet laminate.

That system was easily powerful enough to poke you if you weren't careful working on the car while the engine ran.

 

[2NC995]

"Dirt" comes from a variety of sources.
power supply
overdrive
bias
VSWR mismatch
linearity

Somewhat random thought, and no directed at Kop...

But I used to bleed all over everything with BJTs years ago. Even with 200ish watts. TVs, phones, intercoms...whatever.

You could probably hear me in a blender or toaster oven at the right time and place.

By driving things modestly and running a non-hack job radio, that is all now in the past.

 

[Handy Andy]

I often wondered why they called the morning meal "Breakfast" - I always thought it was the toaster was calling us for "Break" - because it said so...

You could probably hear me in a blender or toaster oven at the right time and place.

 

[2NC995]

I often wondered why they called the morning meal "Breakfast" - I always thought it was the toaster was calling us for "Break" - because it said so...

If you’re bleeding all over hell, you must be getting out right?

I heard a sweet sounding station one day...said on the air, the secret to “getting out” is keeping your power on the intended frequency.

Now, I don’t know who that was, or necessarily agree 100%, but it did make me think about how many of my precious watts were working for me.

DX got MUCH better for me when I stopped worrying about the wattmeter.

 

[Handy Andy]

I actually appreciated the times when the Toaster and Can opener talked to each other - interesting to know that your experience was related to actually making the radio do the work and not hearing the yelling at the Opener for the spilled Can of Beans and the Toaster getting chastised for burning the Strudel.

All this time I thought that's what Remote Control meant...

It's good to know that putting the effort into making your radio do the work versus sounding like someone else whom, didn't know much about radio - worked on it instead.

You attract more Bees with Honey, than Vinegar...

At least in that process of thought, it keeps the crowds with the Pitchforks and Burning Torches away...

I used to call it, Worked All Neighbors award. Especially to hear about what was talked about on the neighbors Stereo while he was enjoying a beer while listening to the White Sox Home game that night.

Can make you cringe...

 

[2NC995]

At least in that process of thought, it keeps the crowds with the Pitchforks and Burning Torches away...

I’d take pitchforks and torches over some of what I’ve seen....hahaha

Bleeding over certain things, and at certain times, can make folks mighty mad.

Girls at the local C store might have thought it was cute...others didn’t.

 

[Onelasttime]

DC-DC transformer.....Look at 50V Mosfets....Cheers!

 

[Onelasttime]

P.S. If you want to go higher than 50V look at how we generate and build devices for high performance aircraft with high freq. power generation and if need be the use of transformers and inverters. It is not hard to rework an alternator for high freq. use. Just things to think about.

 

[WECSOG]

The inverter is no problem. It's best to use an auxiliary battery setup; better still is to add a second alternator just for charging those batteries.
You can easily get a 5KW inverter with either 120 or 240 volts output, then use that to drive whatever amp you want. Solid state 1500 watt amps are available, or tube amps for much higher output. Personally I would rather use a ceramic tube amp. I would also probably make the battery bank 24V with its own separate 24V alternator.
Btw this is not conjecture on my part.

 

[Onelasttime]

Im just pointing out that it’s additional expense with 50v devices.

The price of power on the device input power side is not a big deal. If you decide to go that route you make the shift and do not look back. You invest in quality so it lasts not cheap junk. A quality supply will lost a long long long time if used properly. You can even buy alt. designed for 24V/28V/75V/110V/150V etc......Typically you will see them applications like RV's, Yaghts, and the like. You can go DC to DC up convert or you can use switchers/inverters. My only point is that people make it sound as if using anything other than 12V device is so huge a hurdle to be overcome but really it is not a big deal. A lot of 12V ham radio's have used finals that are not 12V finals.

A properly designed amp being feed by a properly aligned radio with a sound antenna system will not interfere with much of anything. A splatter box is a sign of either poor design or poor operation. On top of that TV's and phones are completly different today as are electric garage doors!LOL