{"id":10838,"date":"2022-08-17T10:48:00","date_gmt":"2022-08-17T00:48:00","guid":{"rendered":"https:\/\/www.homebrewradio.us\/blog\/2022\/08\/17\/daylight-again-on-the-sunrise-net-walter-ka4kxx-builds-a-pto\/"},"modified":"2025-07-22T18:03:25","modified_gmt":"2025-07-22T08:03:25","slug":"daylight-again-on-the-sunrise-net-walter-ka4kxx-builds-a-pto","status":"publish","type":"post","link":"https:\/\/www.homebrewradio.us\/blog\/2022\/08\/17\/daylight-again-on-the-sunrise-net-walter-ka4kxx-builds-a-pto\/","title":{"rendered":"Daylight Again on the Sunrise Net! Walter KA4KXX Builds a PTO"},"content":{"rendered":"

<\/span><\/p>\n

<\/a><\/div>\n
<\/div>\n

Dear Bill: <\/b><\/p>\n


<\/b><\/div>\n
I had never built a PTO, but after reading Farhan’s Daylight Again Transceiver<\/a> article I cobbled one together with parts and pieces I had on hand. My observations so far are as follows. <\/b><\/div>\n

<\/b><\/div>\n

<\/b><\/div>\n
1. The frequency-determining capacitors (shown on the schematic as three 470 pf) are very critical, so I feel the usual experimental cut-and-try technique is a must, even using all NP0 and C0G types. <\/b><\/div>\n

<\/b><\/div>\n
2. After I built the 2 MHz version like the article (see first photo), the stability was terrific, but when I tried building the companion Daylight Again crystal filter, I was only able to get a bandwidth of 1.6 kHz, which is too narrow for my taste in an SSB radio, so I decided to build the same filter design but with 11 MHz crystals, where I could easily achieve a 2.8 KHz BW. <\/b><\/div>\n

<\/b><\/div>\n
3. Therefore, now I needed a higher frequency VFO, so I merely reduced the capacitance (from about 1200 to 370 pf) without changing the coil and I am very impressed with the performance of my 4 MHz PTO (see second photo). The bandspread easily covers the entire 40M band, CW and Phone. <\/b><\/div>\n

<\/b><\/div>\n
4. However, whenever I transmit on the 40M Phone band, I like to first set my VFO within 10 Hz of the operating frequency. That way, if I talk for five minutes or so and get up to 15 Hz of drift (which is quite common with many radios when I operate portable outdoors in the sun and wind), it will not be noticable and I avoid receiving any “you are off-frequency” chastising. But the shortcoming I have with this PTO inductor is that the 1\/4-20 bolt has a coarse thread, so it is very difficult for an old fellow like me to get within even 20 Hz of a particular frequency just using this common bolt. Therefore I believe a better choice would be the fine thread 1\/4-28 two-inch brass threaded bolt which is available from industrial supply houses like McMaster-Carr. However, for CW use or those with a very steady hand, the 1\/4-20 works well enough. <\/b><\/div>\n

<\/b><\/div>\n
5. I solved my fine tuning problem by adding a varactor circuit using a common 1N914 diode in series with a 100 pf capacitor, operating from 0 to 6 volts. Another advantage to adding this feature is that since I have not so far enclosed my PTO, I can mount the varactor potentiometer several inches from the PTO so my hand capacitance does not affect the frequency like when tuning with the bolt. <\/b><\/div>\n

<\/b><\/div>\n
6. An easy way to “do the math” in my case with the common Sanjian counters is to simply create a small lookup table listing half a dozen common frequencies and stick it on the radio. For example, 90% of the time in the morning I am tuned to my favorite SouthCars Net frequency of 7251, so using a BFO setting of 10,999.900, I simply set the PTO to 3,748.90 on the 6-digit 10 Hz resolution counter I normally use (see third photo). <\/b><\/div>\n

<\/b><\/div>\n
7. I am currently using my Daylight Again PTO on a daily basis with an NE602 receiver, and I am thinking of adding a locknut to the bolt so it does not wiggle when I jostle or move the radio, essentially giving me a crystal replacement oscillator that I can use for any single 40M frequency. To date I have been able to listen for hours at a time indoors without even any touch-up of the varactor fine tuning. <\/b><\/div>\n

<\/b><\/div>\n
8. Also, if continuous frequency readout is desired without building a noise filter circuit board, a separate power supply for the counter is a solution. For portable operation I use Lithium Polymer radio control model airplane batteries which are light, small, and cheap, so one 12V 2000 mAH battery for the transceiver (allows a half hour of transmitting at 15 watts) and a much smaller 12V 350 mAH battery with a series resistor to reduce the current and brightness of the counter has worked well for me. <\/b><\/div>\n

<\/b><\/div>\n
73, Walter KA4KXX <\/b><\/div>\n
Orlando, FL<\/b><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Dear Bill: I had never built a PTO, but after reading Farhan’s Daylight Again Transceiver article I cobbled one together with parts and pieces I had on hand. My observations so far are as follows. 1. The frequency-determining capacitors (shown on the schematic as three 470 pf) are very critical, so I feel the usual … Continue reading “Daylight Again on the Sunrise Net! Walter KA4KXX Builds a PTO”<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[42,66,16,174,365,53],"tags":[],"class_list":["post-10838","post","type-post","status-publish","format-standard","hentry","category-40-meters","category-farhan","category-filters","category-frequency-counter","category-pto","category-vfo"],"_links":{"self":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/10838","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=10838"}],"version-history":[{"count":1,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/10838\/revisions"}],"predecessor-version":[{"id":10841,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/posts\/10838\/revisions\/10841"}],"wp:attachment":[{"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/media?parent=10838"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/categories?post=10838"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homebrewradio.us\/blog\/wp-json\/wp\/v2\/tags?post=10838"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}