Mirage B - 310 - G 2 meter amplifier

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N2BRI

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According to the instructions for this amplifier when you shut it off it is a direct through how much power is it safe to run through the amplifier with it off I've only been running 5 or 10 watts through it was wondering if it's safe to run 50? Also with the amplifier off I'm able to transmit with 440 on Five Watts and checked the SWR and it is fine but there's quite a bit more loss then on two meters is this safe to do? I thought it would be safe to run because the SWR reading was good going from the radio to the amplifier off any thoughts appreciated thank you

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prcguy

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I would not risk running any more than what the amplifier is rated for its maximum input when its amplifying. There are RF sense circuits with components optimized for very low power up to the maximum rated input power of about 8w. If you run 50W through the amp when its off these components will be subjected to almost 10X the power they were designed for.

I bought a B-310-G new and used it very little but did hit it with 5W for awhile until it burned up its final output transistor. I replaced it with a slightly higher rated one, gave it a good tune up for max power with minimum current draw and now it seems pretty bullet proof. I keyed down for nearly an hour with 5W drive and about 118W out with no problem then transmitted for several minutes with no load a full power and it survived just fine. Just an FYI since I've heard of many burned up B-310-Gs.

Also, why would you run a 100W amplifier on a radio that can put out 50W? There is very little difference to the receiving party going from 50 to 100W.
prcguy
 

N4KVE

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I would not risk running any more than what the amplifier is rated for its maximum input when its amplifying. There are RF sense circuits with components optimized for very low power up to the maximum rated input power of about 8w. If you run 50W through the amp when its off these components will be subjected to almost 10X the power they were designed for.
When the amp is off, these components are not in line. The signal goes into the amp, & right out. But also if I had a 50 watt radio, I wouldn't waste my time with a 100 watt amp. Going from 50 to 100 watts MIGHT get you an extra mile.
 

prcguy

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The RF sense components are always in line, otherwise it would not be able to detect when you transmit to key the amp. There will be a cap or resistor coupled point that feeds a diode or two and a couple of transistors to drive the relays. The coupling cap or resistor values are chosen for reliable operation over the expected input range up to maybe 8w and if you run 50w through it turned off you may exceed the voltage ratings for the diodes in the RF sense circuit.
prcguy

When the amp is off, these components are not in line. The signal goes into the amp, & right out. But also if I had a 50 watt radio, I wouldn't waste my time with a 100 watt amp. Going from 50 to 100 watts MIGHT get you an extra mile.
 
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cmdrwill

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Also there is a low pass filter in the amp and transmitting into it on UHF the signal will get sucked up in the filter.
 
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