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Author Topic: on a adv vhf xmtr, wat is aprrox pwr in/out ratio  (Read 216 times)
KY7R
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Posts: 5




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« on: January 02, 2008, 07:03:15 AM »

IN/Out Pwr ratio at res. with a tuned ant. output circuit?
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AC5UP
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Posts: 3835




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« Reply #1 on: January 02, 2008, 07:25:22 AM »

A special note for new Hams:

ths is wht hppns whn u wrk to mny cw contsts fr to mny yrs.

In answer to the question... Are we talking DC input vs RF output? If so, the mode and amplifier class can be more significant than the VHF thing. FM can tolerate a Class C non-linear amplifier which typically comes in around 50% to 60% efficiency, SSB / ATV needs a Class A or AB1 linear amplifier which can run closer to 45% efficiency... Assuming bipolar silicon devices in each.

I'm not up on the latest technology @ VHF and if FET's have improved those numbers, but the higher efficiencies seen in broadcast gear ain't happenin' at a price the typical OM is willing to pay.


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AC5E
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« Reply #2 on: January 02, 2008, 07:45:34 AM »

Well, from experience, I would guess in the 45 to 50 percent range for a LINEAR tube amplifier with a tuned output stage. A non linear (Class C) amp would do a little better, from 55 to maybe 60 percent.

Theoretically, Class A can be no more than 50% efficient, B no more than 60% efficient, and C no more than 70 percent. Very few practical amplifiers come close to theory, and most of those are distinctly non-linear.

73  Pete Allen  AC5E
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AA4PB
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« Reply #3 on: January 02, 2008, 07:58:16 AM »

The efficiency figures are for the final amplifier DC input only. If you are measuring the DC input to the whole transceiver then there will be extra current taken by many other circuits in addition to the final amplifier.
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WA3SKN
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Posts: 5457




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« Reply #4 on: January 02, 2008, 10:52:01 AM »

Gary,

Not sure what you are looking for here.  Your web page indicates you are using a handheld but have 25 watts output... are you looking for the dB gain of the amp, or the DC input power vs the output power of the amp? Or, something else?

-Mike.
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AC5E
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Posts: 3585




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« Reply #5 on: January 02, 2008, 02:15:12 PM »

Generally, the RF out to DC in ratio is used to determine how much cooling will be needed. Filament current is certainly a part of power consumption, but if wattage drawn is that big a consideration it would be best to leave the amp behind.

However, it would be helpful if we had some guide to your intent besides speculation.

73  Pete Allen  AC5E
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KB9CRY
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Posts: 4284


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« Reply #6 on: January 02, 2008, 06:41:36 PM »

100%

I just love being able to help a helpless Ham!

Especially one that can't communicate!!!!?Huh
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