{"id":8801,"date":"2017-01-18T11:01:00","date_gmt":"2017-01-18T00:01:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2017\/01\/18\/n8nms-saved-vfo-30-meter-rig\/"},"modified":"2025-07-22T01:22:54","modified_gmt":"2025-07-21T15:22:54","slug":"n8nms-saved-vfo-30-meter-rig","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2017\/01\/18\/n8nms-saved-vfo-30-meter-rig\/","title":{"rendered":"N8NM’s SAVED VFO 30 Meter Rig"},"content":{"rendered":"
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In early December Steve Murphy N8NM picked up this “mystery box” at a hamfest. Dr. Juliano identified it as an old CB VFO. Even though Steve is deeply committed to the dark side of frequency generation (digital synthesis) I was able to convince him to put this VFO to legitimate and proper amateur radio use AS AN ANALOG VFO. I mean just look at that dial! It would be a sin to connect that beautiful mechanism to a rotary encoder. We see the results below. <\/b> <\/p>\n

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Bill: <\/b>

The 30m rig that I had hoped to have QRV for SKN is finally ready to hit the airwaves! I still have a few odds and ends to tidy up, but it’s essentially done.<\/b> <\/p>\n

Where I ran into problems was my original choice of IF and VFO frequencies: I’d gone with a 13.51 MHz IF because I had the rocks, but that put the 3rd harmonic of the VFO right in the middle of the band. Oops.<\/b><\/div>\n
Moving the IF to 13.56 fixed that problem, but I still had a spur from that harmonic that needed to be filtered. At first, it looked like a trap on the output of the VFO would squish it, but it ended up requiring a few extra poles of bandpass filtering to get it below -40 dB\/c. Now we’re legal.<\/b><\/div>\n
Anyway, here’s a few pics. The chassis are bent from 22 ga aluminum on my trusty Harbor Freight brake. They’re almost square, they look cockeyed because I still need to make brackets to hold the top and bottom together. The heat sink is overkill for 5 watts, but it was cheap \ud83d\ude42<\/b><\/div>\n
Electronically, almost everything between the audio and power amps is straight-up Bitx. The power amp uses a RD16HHF1 driven by my spin on Farhan’s RF-386, and the audio is an LM380 driven by an LM324, with gating between CW and digital mode input handled by a CD4066. The CW tone generator is based on WB0RIO’s “clickless” sidetone circuit, which, while a little complicated, creates perfectly formed CW elements that really sound nice.<\/b><\/div>\n
I’m still amazed at the stability of the LC VFO; I was monitoring JT65 signals over the weekend and noticed zero drift after warm-up. To keep it ready to rock, it’s powered from the “hot” side of the on\/off switch, as is the CW oscillator. <\/b><\/div>\n
I can’t think of much else to say about it… It is what it is \ud83d\ude42<\/b><\/div>\n
73 – Steve N8NM<\/b><\/div>\n
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In early December Steve Murphy N8NM picked up this “mystery box” at a hamfest. Dr. Juliano identified it as an old CB VFO. Even though Steve is deeply committed to the dark side of frequency generation (digital synthesis) I was able to convince him to put this VFO to legitimate and proper amateur radio use … Continue reading “N8NM’s SAVED VFO 30 Meter Rig”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":8802,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[510],"tags":[],"class_list":["post-8801","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-30-meters"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/8801","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/comments?post=8801"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/8801\/revisions"}],"predecessor-version":[{"id":8805,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/8801\/revisions\/8805"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media\/8802"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=8801"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=8801"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=8801"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}