Recent content by Rick Miller

I prefer a NanoVNA, it allows you to sweep through the bands and gives a nice view of the impedance bandwidth.

The PCB should mount directly to the heatsink. The white masking on the bottom of the PCB should insulate just fine. I've heard others have tried to add a bit of insulating material only to discover oscillations. I suppose if you're worried about it you could use some nail polish to thicken up...

Sorry for taking so long to respond. I had a hell of a time getting a good picture. I've attached a pdf file that I have marked up so you can see exactly where I cut.

I must apologize, I will not be able to get any decent pictures tonight. My daughter is coming over tomorrow night and I'll have her bring her camera. My phone just cannot seem to get any detail close up. I will post them as soon as I can...

It's just a plain single sided PCB The ones that wouldn't bias up would only show around 30ma max no matter where you set the pot. I had to bring the voltage up to nearly 5v before they would start pulling current. I was running a yaesu ft-817 into it, on SSB that amounts to about 10W peak. On...

Hi Joe, I used a 'CBS-4' package from ICA Manufacturing as my starting point. https://www.icamanufacturing.com/cbs-packs/cbs4m. I then cut out a hole in the PCB to allow the PA-100 kit to fit into the hole. Thus the 9120 mounts directly to the aluminum heatsink below. I decided to do this to...

How timely, I haven't logged in for a while. I was just given a 300a without the transformer. For now it's a shelf decoration, but I'll be looking for a transformer soon myself...

I'd say start with the keying circuit. It's not uncommon for the keying transistor to die.

Ok, this is a long shot, but seeing DoctorAudio made me think of an old friend. His name is Lee and called himself DocAudio. Would your name be Lee?

My next project will use a pair of MRF300AN/BN transistors running 50V. I started assembly this weekend but am waiting on components for the bandpass filter which will take over a month to get here. In the meantime I will get the pallet assembled and tested. I'm quite interested in this...

I didn't add any attenuation, I was concerned that I may need to, but after testing it seems to run like a champ. I blasted away on FT8 for 2hrs straight until my radio was way too hot. The amp however was only slightly warm to the touch. So based on how it's working I think it's fine with 5W...

I got mine from eBay/China, took about 3wks to get them. I bought three of them total, and have now built two. Both seems to be working great, I did not modify or have to do any tuning at all. The only thing I changed was the wire on the transformers, opting for ptfe wire instead of whatever the...