REVIEW: RAMSEY QAMP20

Ramsey Electronics has several inexpensive easy to assemble electronic kits. Some are specifically amateur radio related and others are not. The QAMP20 is a 20 meter 20 watt linear amplifier. Being linear it will run CW, SSB, or AM. It can be driven with ½ to 2 watts with a power requirement of 12 VDC at 4 Amps.

Ramsey’s estimated assembly time is 4 hours for beginner, 2 hours for intermediate, and 1.5 hours for advanced builders. I did not time myself but I would say that their timing estimate is fairly accurate.

The instruction booklet, as with all their kits I have assembled so far, is very well done and can be followed by anyone even with no electronic knowledge.

Alignment is very easy. Basically it is just a matter of setting the bias.

The work horses of the amplifier are two P16NF06 MOSFET transistors. They are run in Push-Pull format so as to reduce potential second harmonic output. It has a 3 stage pi network low pass filter output to further reduce the harmonic output. The input and output to the transistor are both through ferrite wideband transformers.

The exciter input uses a T-R relay circuit which is operated by a simple diode detector to sense when RF is applied and a two transistors amplifier circuit to drive the relay. If the power switch is not on the relay will not actuate and thus the exciter can be run “bare foot” but when the power is on it will switch on as soon as the exciter is keyed.

When testing the QAMP20 I found that ½ watts in gave 5 watts out and 1 watt in gave 10 watts output. An IFR service monitor’s power meter was used for the test. The efficiency is about 30 to 35% which is about where a class AB amplifier should run.

Over all, with the exception of the plastic box to house the unit, I would give this unit a very high rating considering the cost.

 

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