{"id":7880,"date":"2022-09-16T15:01:00","date_gmt":"2022-09-16T05:01:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2022\/09\/16\/fixing-up-an-old-homebrew-rig-barebones-superhet-and-vxo-6-watter\/"},"modified":"2025-07-22T18:02:55","modified_gmt":"2025-07-22T08:02:55","slug":"fixing-up-an-old-homebrew-rig-barebones-superhet-and-vxo-6-watter","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2022\/09\/16\/fixing-up-an-old-homebrew-rig-barebones-superhet-and-vxo-6-watter\/","title":{"rendered":"Fixing Up An Old Homebrew Rig — Barebones Superhet and VXO 6 Watter"},"content":{"rendered":"<\/p>\n
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I’m not exactly sure why I pulled this old rig off the shelf, but I’ll write up what I did — I often use this blog as a kind of notebook. I can look back and easily see what I did on my last encounter with the rig. <\/b><\/div>\n
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The receiver is Doug DeMaw’s Barebones (aka Barbados) Superhet<\/a>. This was my first superhet receiver. I built in in 1997. The transmitter was my first real homebrew project — it is the VXO 6 watter from QRP classics. I built it in the Dominican Republic, probably in 1993 or 1994<\/a>. I built the power supply so that I could say that the entire rig is homebrew. <\/b><\/div>\n

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This rig is getting a bit long in the tooth: The receiver is built with 40673 Dual-Gate MOSFETs, an some of the transistor cans have gotten rusty. The frequency readout on the receiver is the top of a coffee can fitted onto the reduction drive behind the tuning knob from a Drake 2-B (not MY 2B!). <\/b><\/div>\n

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Here are two 2013 videos that I did on this receiver: <\/b><\/div>\n
https:\/\/soldersmoke.blogspot.com\/2013\/03\/video-of-my-barebones-superhet.html<\/a><\/b><\/div>\n

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— I put the crystal filter back in CW mode. I had widened it so that I could listen to 20 meter SSB, but I decided to go back to its original configuration. When I built the receiver in 1987, I didn’t characterize the crystals — I just used the capacitor values that Doug DeMaw had in his article. I pretty much did that again this time, just putting caps that are close in value to what Doug had. DeMaw used color burst crystals at 3.579 MHz. So I guess this would be a GREAT receiver for the Color Burst Liberation Army! <\/b><\/div>\n

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— I used My Antuino (thanks Farhan!) to check the passband. Here is what it looks like. I just put the Antuino across the 10k resistors on either side of the input and output transformers. The coil cores had become very loose — I just tried put them in the right place. I may need to put some wax in there to allow them to better stay in place. I think they could have used toroids instead — that would have been easier. One of the transformer connections was open — they don’t work well that way, once I fixed that, the passband looks like this: <\/b><\/div>\n
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— Each of the horizontal divisions is 500 Hz. The passband is not pretty, but it is OK, and I didn’t feel like doing too much work on this to get it in better shape. <\/b><\/div>\n

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— The filter peak was a bit lower in frequency than expected. I found that trimmer cap C3 in series with the BFO crystal would not allow me to lower its frequency sufficiently. So I moved C3 to a position in parallel with the crystal. With this mod, I could get the BFO frequency to 3578.69. This produces a 690 Hz tone when the received signal is at the peak of the IF passband. Opposite sideband rejection is quite good. <\/b><\/div>\n

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March 2013 Rebuild of the VXO 6 watter<\/span><\/b><\/div>\n

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— I didn’t have to do any real work on the transmitter. The RF amplifier in the transmitter had served for a time as the RF amp in by 17 meter DSB rig (I had added a bias circuit, which I removed when I put the amplifier back in Class C). Some time ago I rebuilt the oscillator circuit (which had been literally cut off the board when I used the amplifier in the DSB rig). <\/b><\/div>\n

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— I did have to reconfigure the muting circuit — the T\/R switch in the transmitter switches the antenna and also — through a two wire circuit — cuts off 12 V DC to the transmitter when in receive mode. <\/b><\/div>\n

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— For sidetone I just put a small piezo buzzer through a 1k resistor between 12 V DC and the key line. <\/b><\/div>\n

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It all worked fine — I talked to three stations on the high end of the 20 meter CW band. <\/b><\/div><\/p>\n","protected":false},"excerpt":{"rendered":"

I’m not exactly sure why I pulled this old rig off the shelf, but I’ll write up what I did — I often use this blog as a kind of notebook. I can look back and easily see what I did on my last encounter with the rig. The receiver is Doug DeMaw’s Barebones (aka … Continue reading “Fixing Up An Old Homebrew Rig — Barebones Superhet and VXO 6 Watter”<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":7881,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[109,199,317,7,19,66,16,87,57],"tags":[],"class_list":["post-7880","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-antuino","category-barbados","category-cbla","category-demaw-doug","category-dominican-republic","category-farhan","category-filters","category-qrp","category-superhet-receivers"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/7880","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\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/comments?post=7880"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/7880\/revisions"}],"predecessor-version":[{"id":7885,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/7880\/revisions\/7885"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media\/7881"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=7880"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=7880"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=7880"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}