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Title: It works! Post by: K8DI on February 04, 2023, 05:37:25 PM My RCA Broadcast type BTA-1R1, serial no. 1162, is, finally, alive..
Today, a little after 2pm, I made its first ever ham contact, with Cid/K8JLY, on 40m at about 300w carrier. It’s taken a long time and a lot of unexpected hiccups, along with some good advice and help from everyone here, to get here. Thanks, guys! Ed The photo is testing into the dummy load at 1100w, with sine wave modulation. At 300w, the plates are pretty much dark. Title: Re: It works! Post by: KD6VXI on February 05, 2023, 07:36:42 AM It's a good idea to blush the tubes at least awhile every month. Keeps the tubes 'gettered'.
It's your choice if this happens into a dummy load at full modulated power 😂😂😂 Would be good to blow insects off the feedpoint, you know. --Shane WP2ASS / ex KD6VXI Title: Re: It works! Post by: Todd, KA1KAQ on February 07, 2023, 10:33:55 PM Hey Ed - it was good to work you the other night. The RCA was pounding into VA with a strong, solid signal.
I do think you had a bit of feedback on your signal, wonder if anyone else mentioned it? I didn't because initially I thought it was someone screwing around on frequency to disrupt us. It was almost like a church organ sound, and it followed your carrier perfectly without overlap, which is why I think it might've been feedback. Title: Re: It works! Post by: K8DI on February 08, 2023, 06:24:02 AM Hey Ed - it was good to work you the other night. The RCA was pounding into VA with a strong, solid signal. I do think you had a bit of feedback on your signal, wonder if anyone else mentioned it? I didn't because initially I thought it was someone screwing around on frequency to disrupt us. It was almost like a church organ sound, and it followed your carrier perfectly without overlap, which is why I think it might've been feedback. Being the thing’s first round into an antenna instead of a dummy load, there were a bunch of RF issues to be sorted. The first round was RF into the control system, which I fixed Saturday morning. That stopped the random overload relay trips…it was bandswitching mid-transmission, with the expected plate current spike and some sparks…. The next was RF getting into the mic preamp, which I fixed Sunday morning, after our Saturday contact. I had a scope on the audio and RF envelope to get an idea of the modulation, and after another mentioned it I watched between the words and saw the waveform… Unfortunately by the time I was done, so was the band…. But thanks for the contact and the report. Next time it should sound better! Ed |