New PCB available for WA2EBY linear amp #linear-amp
After running my uBITX barefoot for the past 18 months (with 1700 FT8/FT4 contacts) I decided it was time to add a little more power. The ever-popular WA2EBY linear amp seemed like a good route, except that nobody offered the circuit board anymore. On a whim, I sent an email to amateurradiokits.in to see if they had even one board left over. Sunil, VU3SUA responded that the old boards were gone, but they were just a few weeks away from releasing a totally new board for this design. I asked to be their first customer, and very shortly had the new board in hand. Here's my review (unsolicited, uncompensated):
Having seen pictures of the earlier board in past construction articles, I can safely say the new board is a big improvement. Cosmetically, it has all the professional elements that were previously missing: plated-thru holes and vias, solder masking and comprehensive silk-screening. The size is a few tenths of an inch longer and narrower than the original, which turns out to be an excellent match for an inexpensive 150 x 60 x 25mm heatsink that is widely available on EBay as of this writing.
Before you start building, you need to make two design choices. First, your input attenuation – pads and traces are provided for a standard pi-network attenuator, but it’s up to you to choose the amount of attenuation needed for your setup and then compute the appropriate size/wattage resistors. Plenty of websites can help with these calculations. Likewise, space is provided for a single band low-pass output filter, but the L and C values are up to you. Again, no problem – go to any WA2EBY article/website/blog published in the past 11 years and you’ll find them listed.
A few notes related to the photo:
As a final note, the original QST articles (Mar, Apr 1999) provide an excellent analysis of the thermal challenges that come with running a pair of IRF510’s at 40+ watts. Based on this, I've decided to run my amp at 30 watts output for the time being, until I have time to construct a better cooling system. A couple of dB output power just seemed like a small price to pay to spend my time operating instead of replacing IRF510’s.
The WA2EBY PC Board can be ordered from amateurradiokits.in. It is currently available as a bare board only, but will eventually be sold as a semi-kit as well. Until it’s added to their website, you can email an inquiry to the address shown on their Contacts page, they’ll respond with the details.