ARRL 250W Solid-state Amp

[Nashua Area Radio Society]

I’m thinking about building the 250-watt solid-state amplifier that appears in recent ARRL Handbooks.  I’m wondering if any other club members have built this amp, or are interested in doing so.

Roughly looking at the budget, the expensive parts , with order-of-magnitude costs, appear to be:

• RF transistors $100/pair
• LPF capacitors $100/set
• Power supply $100
• Heat sink *
• Printed circuit boards *

The boards are available from ExpressPCB, but the cost per set depend strongly on how many sets one orders: there is a setup fee of about $250, and then each board set costs about $20.  So one set costs $270, two are $145 each, three are just over $100 each etc.

Similarly, the heat-sink extrusion is available as a 4-foot length for about $100, but the amp needs only 7 inches, so splitting the cost among several builders would help.

Other parts include toroids, ordinary R’s and C’s, and semiconductors.  I haven’t priced these out, but I’d be surprised if they add up to more than another $100, with only slight economies of scale.  And the case needs some sheet aluminum.

So, is anyone interested in splitting costs of the PCB’s and heat sink?  Or has anyone built this amp and has extra bits left over?

[Fred Kemmerer]

Seems like an interesting project Bill. What is the frequency range of the amp?

[Nashua Area Radio Society]

It covers 160 thru 6 meters (including 60m & the WARP bands).

[Author]

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