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Author Topic: 2m amplifier output question.  (Read 3492 times)
VE2PIO
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Posts: 17




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« on: July 30, 2016, 10:17:45 AM »

Hi, question for amp. I have a radioshack hta-20 30w 2m amplifier.
I check the output with power meter and have around 18-25 watt max .
Around all the band 144-148 and any voltage (12-14v).
With 1 watt in i have 18 w out and 25 watt with 5 w in.
Do you think the amplifier begin to be bad because i dont have the rated output?
Thanks for info
73
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W9IQ
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Posts: 3388




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« Reply #1 on: July 30, 2016, 11:59:38 AM »

Given the accuracy of your test equipment and some allowance in the specification, I would say you have a fully functioning amp.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
VE2PIO
Member

Posts: 17




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« Reply #2 on: July 30, 2016, 12:44:04 PM »

I made this interrogation because i have 2 them (hta-20) . One that make 35w output fine and the other maximum 20-25w.

I want to know if one the watt drop beacause some part begin to be bad?
Thanks
73
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K8AXW
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Posts: 7037




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« Reply #3 on: July 31, 2016, 09:19:46 PM »

Could be because the assembly tech didn't adjust the drive to the final transistor(s) to rated output or a component in the final drive circuit is changing value.  At this point, I wouldn't concern myself with it.
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K6AER
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Posts: 5720




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« Reply #4 on: August 01, 2016, 07:09:44 AM »

These amplifiers are biased class C and their is no bias adjustment per say. On the transistor base connection there will be a choke and a resistor going to ground for the bias. Their might be a couple of trim capacitors (input one output)  that can be adjusted for maximum output. Also check the output filter, a series of coils and fixed capacitors to see if they are adjusted the same with indicial coil configurations. Output power will change with supply voltage. You could pick up 5-7 watts with a change of 2 volts.

In class C the efficiency should be a bit below 60%.  Output wattage divided by input  wattage. Input wattage is volts supplied times the input current.
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VE2PIO
Member

Posts: 17




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« Reply #5 on: August 02, 2016, 03:56:47 PM »

 Thank you for your feedback.
In summary, do i need to worry or the amplifier will work for
time even if the output is reduced?

Thanks a lot for your help.
73
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KK5DR
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Posts: 631


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« Reply #6 on: August 02, 2016, 07:18:08 PM »

Nobody will notice your deficient signal strength.
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AA2UK
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Posts: 915




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« Reply #7 on: August 26, 2016, 06:41:02 AM »

I would try comparing the input return loss (VSWR) between the 2 amplifiers.
Differences between the 2 amps might shed some light on the varying outputs.
I seriously doubt the output devices are deteriorating.
73, Bill AA2UK
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