Wizard GI-46B

[dxhound]

The tuned inputs act a pre band pass filters. And on your more expensive amps, they exist on the outputs as well. This should answer any and all question about filtering and how it should be done!!! How to select an HF tube amplifier ?

Also the carrier situation has alot to do with biasing and duty cycle, But in general, the carrier should be kept 1/4 of the peak grid disipation for longevity and linearity purposes.

 

[HiDef]

The tuned inputs act a pre band pass filters. And on your more expensive amps, they exist on the outputs as well. This should answer any and all question about filtering and how it should be done!!! How to select an HF tube amplifier ?

Also the carrier situation has alot to do with biasing and duty cycle, But in general, the carrier should be kept 1/4 of the peak grid disipation for longevity and linearity purposes.

A tuned input with a typical Q of 2 as used in triode hambone amps does not resemble a bandpass filter in operation.

 

[dxhound]

A Q of 2 would be this Q=freq/bandwidth (2= 27MHZ/13.5Mhz) So it is in fact a band pass filter (allowing only that band to pass) Just a very wide one allowing anything between 20.25 MHZ and 33.75 Which technically would stop the 2nd and 3rd order harmonics.

But as stated, a Q of 12 is the accepted and widely used measurement. which would be

12= 27MHZ/2.25 or a pass band of 24.75 through 29.25

Dont get hung up on the term "BAND" that does not mean 10 meter band or 40 meter band. They use the term Band to describe a portion of continuous frequency between a low and high cutoff point.

 

[HiDef]

A Q of 2 would be this Q=freq/bandwidth (2= 27MHZ/13.5Mhz) So it is in fact a band pass filter (allowing only that band to pass) Just a very wide one allowing anything between 20.25 MHZ and 33.75 Which technically would stop the 2nd and 3rd order harmonics.

But as stated, a Q of 12 is the accepted and widely used measurement. which would be

12= 27MHZ/2.25 or a pass band of 24.75 through 29.25

Dont get hung up on the term "BAND" that does not mean 10 meter band or 40 meter band. They use the term Band to describe a portion of continuous frequency between a low and high cutoff point.

The function of a tuned input is to provide a 50 ohm resistive load to the driver stage. Any filtering is a bonus but it isn't there as a filter. Your stated passband only has 3dB corners. Hardly even worth mentioning.

Newbees who are used to solid state amps needing bandpass filters will buy into mis information that all that "extra" stuff on ham tube amps must be for filtering.

It's becoming an impossible battle to deal with internet radio science.

 

[dxhound]

What you say is correct, The tuned input does play two roles. But think of it this way. The farther you go outside the passband, the higher the impedance is. With higher impededence comes higher supresion. So the attenuation is expodential the farther from the passband you go. By the time you get to double the resonant frequency (2nd harmonic) the attenuation level could be as high as 60db. I dont remember off the top of my head, but the FCC requires a certain amount of attenuation on the harmonics........I think its 40db but not 100% sure

And I agree, not ALL the extra stuff in Ham amplifiers is for filtering of the RF output. There are also DC and AC filters to keep down on interference. Not to mention Inrush protection, Current limiters, ALC tracking, SWR protection, soft start....the list goes on!!! All these pay for them selves the frst time you accidently have the antenna switch on an empty port or have the amplifier loaded wrong and forget to dip the plate/grid current.


Long and short of it is, YES you can do what Wizard is doing and show an input output impedance of 50ohm and that will help limit the amount of harmonics and make the tube happy. The problem is, people are expecting to get a clean 2kw from 1 3cx800a7 and that is just not possible. His amps might be very clean when driven properly. But no one does drive them this way and because no extra precautions for filtering are taken, It splatters all over kingdom come. Keep the tube linear and all will likely be good to go.

 

[Shockwave]

The function of a tuned input is to provide a 50 ohm resistive load to the driver stage. Any filtering is a bonus but it isn't there as a filter. Your stated passband only has 3dB corners. Hardly even worth mentioning.

Newbees who are used to solid state amps needing bandpass filters will buy into mis information that all that "extra" stuff on ham tube amps must be for filtering.

It's becoming an impossible battle to deal with internet radio science.

That's like saying "the motor in your car is there to provide power to move the vehicle. Any heat it developes when running is just a bonus because it's not there as a heater". If heat wasn't a side effect of running the motor, manufacturers would need to add a heater. Just like if harmonic attenuation was not a function of the PI network, you would add additional filtering as with solid state amps.

While the stated Q and bandwidth of the PI network would only provide 3 db attenuation at 33.75 MHz, you know what really matters is the second harmonic of 11 meters. By the time you get out to 54 MHz that attenuation is around 40 db minimum and certainly worth mentioning.

 

[dxhound]

That's like saying "the motor in your car is there to provide power to move the vehicle. Any heat it developes when running is just a bonus because it's not there as a heater". If heat wasn't a side effect of running the motor, manufacturers would need to add a heater. Just like if harmonic attenuation was not a function of the PI network, you would add additional filtering as with solid state amps.

While the stated Q and bandwidth of the PI network would only provide 3 db attenuation at 33.75 MHz, you know what really matters is the second harmonic of 11 meters. By the time you get out to 54 MHz that attenuation is around 40 db minimum and certainly worth mentioning.

WORD!!!!!!!!!

 

[bigred222]

just so you know shock and scott im still alive 222 in the buckeye state!!!!!!!!!!

 

[Mr Clean]

deleate

 

[linearone]

just so you know shock and scott im still alive 222 in the buckeye state!!!!!!!!!!

you moved?

 

[Mr Clean]

This is what a nasty ol wizard built sounded like in dx. May have had the mic alittle on the high side and I dont have the ears I used to but tell me whats wrong with the way this sounds.


YouTube - Mr Cleen & Lip Chopper258 upstate NY

 

[Oatmeal]

Nice gate.....

That Wizard amp sounded good and clean to me....

 

[Number15]

Trippletwo runs one and sounds clean and locks it down in central cal. Too each his own. peace.