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Title: PTT and TX/RX timing circuit progress! Post by: KJ4OLL on February 14, 2016, 07:15:52 PM Hi,
Working on the "final" circuits for the homebrew! Amp is a simple design, one tube only, (3CX3000A7), driven by a 32V-2. Receiver is an R-390. - PTT using a relay sequencing-timing circuit from Don K4KYV. https://www.youtube.com/watch?v=ueeq4h888tc - Vacuum relay to switch antenna between TX/RX Discovered that the lugs on the vacuum relay are made of something that I can't solder. Considered using the TIG machine, but... Anyway, resorted to the lathe and a microscopic tap & Bristol screws/wrench to fabricate the connectors. (http://i180.photobucket.com/albums/x257/fish1_07/am/schematics/DSC00032_zpsubxjmecc.jpg) (http://i180.photobucket.com/albums/x257/fish1_07/am/schematics/DSC00033_zpsvx2s2jmo.jpg) Next will be the relay & related parts to provide the PA cutoff circuit as part of the PTT operation. 73 Frank KJ4OLL Title: Re: PTT and TX/RX timing circuit progress! Post by: w1vtp on February 14, 2016, 07:45:58 PM Outstanding! Nice work. Keep the posts & pics coming. Don has a good sequencing circuit for sure
Al Title: Re: PTT and TX/RX timing circuit progress! Post by: KJ4OLL on February 16, 2016, 12:45:38 PM In the interest of others learning from my mistakes w/ the Kilovac-Gigavac H8 vacuum relay!
Too much force on the lugs is "bad". (http://i180.photobucket.com/albums/x257/fish1_07/am/schematics/broke_zpso8kut8y4.jpg) Fixed: (http://i180.photobucket.com/albums/x257/fish1_07/am/schematics/fixed_zpsdeovnl32.jpg) Will try again with substantially more flexible conductors. Frank KJ4OLL Title: Re: PTT and TX/RX timing circuit progress! Post by: w1vtp on February 16, 2016, 01:56:58 PM That's sad. :( Yes, zero bending moment at all times is absolutely important on these and expensive transmitting tubes
Al Title: Re: PTT and TX/RX timing circuit progress! Post by: KJ4OLL on February 24, 2016, 07:21:26 PM Hi, AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
Today's progress on the PTT and PA cutoff bias relays & circuits! (http://i180.photobucket.com/albums/x257/fish1_07/am/PTT/ptt_and_pa_cutoffbias_zpsz30uuxso.jpg) Mounted one of the spare Kilovac H8 vacuum antenna relays so as to not break another one....he said optimistically (http://i180.photobucket.com/albums/x257/fish1_07/am/PTT/flexible_antennarelaymount_zpsftagntn4.jpg) Tomorrow some actual power up testing, and possibly installation in the amp...very exciting..... 73 Frank KJ4OLL |