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Homebrew PTO/VFO question.
I was curious if anyone has had any experience w/ homebrewing the PTO/VFO
from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif .. I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX |
J Shrum wrote:
I was curious if anyone has had any experience w/ homebrewing the PTO/VFO from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif . I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX It's not that they're tricky to look at -- it's that they're tricky to get everything working right. This looks like it's a basically good design. It's common-source, which is a bit odd. There's no buffer indicated, which will be necessary. Really what makes VFO construction difficult is getting the thing stable with respect to nearly every effect in the known universe, and that has more to do with component selection and construction methods than it does with the schematic. If I were going to recommend a VFO I'd recommend a series-tuned colpitts. You can probably find one in the ARRL handbook and build away. If the designs look complicated it's because to be useful a VFO needs the oscillator itself, a buffer amp and usually a power amp. The schematic you have leaves off the buffer and power amplifiers; by the time you stick those on your schematic will be as complex as any other VFO design you've seen. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
J Shrum wrote:
I was curious if anyone has had any experience w/ homebrewing the PTO/VFO from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif . I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX It's not that they're tricky to look at -- it's that they're tricky to get everything working right. This looks like it's a basically good design. It's common-source, which is a bit odd. There's no buffer indicated, which will be necessary. Really what makes VFO construction difficult is getting the thing stable with respect to nearly every effect in the known universe, and that has more to do with component selection and construction methods than it does with the schematic. If I were going to recommend a VFO I'd recommend a series-tuned colpitts. You can probably find one in the ARRL handbook and build away. If the designs look complicated it's because to be useful a VFO needs the oscillator itself, a buffer amp and usually a power amp. The schematic you have leaves off the buffer and power amplifiers; by the time you stick those on your schematic will be as complex as any other VFO design you've seen. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
I think I several hours building mine from an ARRL handbook design of some
sort, then maybe a half hour a day for a couple of weeks with a 50 Watt lamp for heating and a fan for cooling until I tweaked the drift with various N750, etc. ceramic caps. A real challenge but whatever drift I have now is virtually nil . I think I quit tweaking at about 200 Hz "cold" to "warm" drift. BTW, my transmitter is a hetrodyne affair, 5.0 to 5.2 MHz VFO + keyed crystal oscillator, both feeding Mini-Circuits DBM. If you are interested, I can put to schematic what I ended up with as I need to do it anyways for my own reference. kb8tl at arrl dot net Bob |
I think I several hours building mine from an ARRL handbook design of some
sort, then maybe a half hour a day for a couple of weeks with a 50 Watt lamp for heating and a fan for cooling until I tweaked the drift with various N750, etc. ceramic caps. A real challenge but whatever drift I have now is virtually nil . I think I quit tweaking at about 200 Hz "cold" to "warm" drift. BTW, my transmitter is a hetrodyne affair, 5.0 to 5.2 MHz VFO + keyed crystal oscillator, both feeding Mini-Circuits DBM. If you are interested, I can put to schematic what I ended up with as I need to do it anyways for my own reference. kb8tl at arrl dot net Bob |
Check out this very nice PTO/VFO from WA6OTP
http://www.wa6otp.com/pto.htm "J Shrum" wrote in message ... I was curious if anyone has had any experience w/ homebrewing the PTO/VFO from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif . I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX |
Check out this very nice PTO/VFO from WA6OTP
http://www.wa6otp.com/pto.htm "J Shrum" wrote in message ... I was curious if anyone has had any experience w/ homebrewing the PTO/VFO from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif . I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX |
That PTO is actually exactly what I would want to build, however, ordering
the kit is pretty much against the point. Does anyone by chance have the schematic for the PTO/VFO by WA6OTP? "Brian" wrote in message ink.net... Check out this very nice PTO/VFO from WA6OTP http://www.wa6otp.com/pto.htm "J Shrum" wrote in message ... I was curious if anyone has had any experience w/ homebrewing the PTO/VFO from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif . I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX |
That PTO is actually exactly what I would want to build, however, ordering
the kit is pretty much against the point. Does anyone by chance have the schematic for the PTO/VFO by WA6OTP? "Brian" wrote in message ink.net... Check out this very nice PTO/VFO from WA6OTP http://www.wa6otp.com/pto.htm "J Shrum" wrote in message ... I was curious if anyone has had any experience w/ homebrewing the PTO/VFO from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif . I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX |
"J Shrum" wrote in message ... That PTO is actually exactly what I would want to build, however, ordering the kit is pretty much against the point. Does anyone by chance have the schematic for the PTO/VFO by WA6OTP? Look he http://www.amqrp.org/kits/tin_ear/ The vfo in this simple receiver uses the same type of PTO construction. And the manual includes a schematic. 73, "PM" |
"J Shrum" wrote in message ... That PTO is actually exactly what I would want to build, however, ordering the kit is pretty much against the point. Does anyone by chance have the schematic for the PTO/VFO by WA6OTP? Look he http://www.amqrp.org/kits/tin_ear/ The vfo in this simple receiver uses the same type of PTO construction. And the manual includes a schematic. 73, "PM" |
Why is ordering the kit against the point?
It's a manhattan style construction product. All you get is a baggie of parts, the schematic, and some PCBoard material to work with. A fun and challenging build no matter how you look at it. "J Shrum" wrote in message ... That PTO is actually exactly what I would want to build, however, ordering the kit is pretty much against the point. Does anyone by chance have the schematic for the PTO/VFO by WA6OTP? "Brian" wrote in message ink.net... Check out this very nice PTO/VFO from WA6OTP http://www.wa6otp.com/pto.htm "J Shrum" wrote in message ... I was curious if anyone has had any experience w/ homebrewing the PTO/VFO from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif . I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX |
Why is ordering the kit against the point?
It's a manhattan style construction product. All you get is a baggie of parts, the schematic, and some PCBoard material to work with. A fun and challenging build no matter how you look at it. "J Shrum" wrote in message ... That PTO is actually exactly what I would want to build, however, ordering the kit is pretty much against the point. Does anyone by chance have the schematic for the PTO/VFO by WA6OTP? "Brian" wrote in message ink.net... Check out this very nice PTO/VFO from WA6OTP http://www.wa6otp.com/pto.htm "J Shrum" wrote in message ... I was curious if anyone has had any experience w/ homebrewing the PTO/VFO from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif . I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX |
Point taken.
But my goal at this point is to build w/ salvaged parts from my mound of junk... But thanks for all the input. It is much appreciated. "Brian" wrote in message k.net... Why is ordering the kit against the point? It's a manhattan style construction product. All you get is a baggie of parts, the schematic, and some PCBoard material to work with. A fun and challenging build no matter how you look at it. "J Shrum" wrote in message ... That PTO is actually exactly what I would want to build, however, ordering the kit is pretty much against the point. Does anyone by chance have the schematic for the PTO/VFO by WA6OTP? "Brian" wrote in message ink.net... Check out this very nice PTO/VFO from WA6OTP http://www.wa6otp.com/pto.htm "J Shrum" wrote in message ... I was curious if anyone has had any experience w/ homebrewing the PTO/VFO from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif . I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX |
Point taken.
But my goal at this point is to build w/ salvaged parts from my mound of junk... But thanks for all the input. It is much appreciated. "Brian" wrote in message k.net... Why is ordering the kit against the point? It's a manhattan style construction product. All you get is a baggie of parts, the schematic, and some PCBoard material to work with. A fun and challenging build no matter how you look at it. "J Shrum" wrote in message ... That PTO is actually exactly what I would want to build, however, ordering the kit is pretty much against the point. Does anyone by chance have the schematic for the PTO/VFO by WA6OTP? "Brian" wrote in message ink.net... Check out this very nice PTO/VFO from WA6OTP http://www.wa6otp.com/pto.htm "J Shrum" wrote in message ... I was curious if anyone has had any experience w/ homebrewing the PTO/VFO from http://www.qrpp-i.com/projects/ka8ma...-schematic.gif . I am pretty new to homebrewing, and was wondering if anyone knew of any problems w/ this design that I may watch for. I have read that VFO's can be very tricky, but this one looks incredibly simple. I'm just looking for anyway to get out from under the rock that I'm bound to. Thanks for any input... James Shrum - KC9FFX |
I prefer building stuff out of my junk pile. I do get a greater feeling of
satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 "J Shrum" wrote in message ... Point taken. But my goal at this point is to build w/ salvaged parts from my mound of junk... |
I prefer building stuff out of my junk pile. I do get a greater feeling of
satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 "J Shrum" wrote in message ... Point taken. But my goal at this point is to build w/ salvaged parts from my mound of junk... |
Agreed!
Paul, That tin ear is perfect... That is exactly the PTO I was looking for. I'll give that one a shot. Thanks for everyone... KC9FFX "Brian" wrote in message nk.net... I prefer building stuff out of my junk pile. I do get a greater feeling of satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 "J Shrum" wrote in message ... Point taken. But my goal at this point is to build w/ salvaged parts from my mound of junk... |
Agreed!
Paul, That tin ear is perfect... That is exactly the PTO I was looking for. I'll give that one a shot. Thanks for everyone... KC9FFX "Brian" wrote in message nk.net... I prefer building stuff out of my junk pile. I do get a greater feeling of satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 "J Shrum" wrote in message ... Point taken. But my goal at this point is to build w/ salvaged parts from my mound of junk... |
I grabbed the Tin Ear docs too...I think I will try to build this little
receiver from my parts pile. I need another receiver like I need a hole in the head but what the heck...looks fun. "J Shrum" wrote in message ... Agreed! Paul, That tin ear is perfect... That is exactly the PTO I was looking for. I'll give that one a shot. Thanks for everyone... KC9FFX "Brian" wrote in message nk.net... I prefer building stuff out of my junk pile. I do get a greater feeling of satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 "J Shrum" wrote in message ... Point taken. But my goal at this point is to build w/ salvaged parts from my mound of junk... |
I grabbed the Tin Ear docs too...I think I will try to build this little
receiver from my parts pile. I need another receiver like I need a hole in the head but what the heck...looks fun. "J Shrum" wrote in message ... Agreed! Paul, That tin ear is perfect... That is exactly the PTO I was looking for. I'll give that one a shot. Thanks for everyone... KC9FFX "Brian" wrote in message nk.net... I prefer building stuff out of my junk pile. I do get a greater feeling of satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 "J Shrum" wrote in message ... Point taken. But my goal at this point is to build w/ salvaged parts from my mound of junk... |
Brian,
Just by looking at that schematic, where would I stop building if I only wanted the VFO to use on a simple transmitter? I looked it over, and have a pretty good guess, but I'm not certain. Thanks. "Brian" wrote in message nk.net... I grabbed the Tin Ear docs too...I think I will try to build this little receiver from my parts pile. I need another receiver like I need a hole in the head but what the heck...looks fun. "J Shrum" wrote in message ... Agreed! Paul, That tin ear is perfect... That is exactly the PTO I was looking for. I'll give that one a shot. Thanks for everyone... KC9FFX "Brian" wrote in message nk.net... I prefer building stuff out of my junk pile. I do get a greater feeling of satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 "J Shrum" wrote in message ... Point taken. But my goal at this point is to build w/ salvaged parts from my mound of junk... |
Brian,
Just by looking at that schematic, where would I stop building if I only wanted the VFO to use on a simple transmitter? I looked it over, and have a pretty good guess, but I'm not certain. Thanks. "Brian" wrote in message nk.net... I grabbed the Tin Ear docs too...I think I will try to build this little receiver from my parts pile. I need another receiver like I need a hole in the head but what the heck...looks fun. "J Shrum" wrote in message ... Agreed! Paul, That tin ear is perfect... That is exactly the PTO I was looking for. I'll give that one a shot. Thanks for everyone... KC9FFX "Brian" wrote in message nk.net... I prefer building stuff out of my junk pile. I do get a greater feeling of satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 "J Shrum" wrote in message ... Point taken. But my goal at this point is to build w/ salvaged parts from my mound of junk... |
James,
I printed out the docs today....lemme look at it. Good question... "J Shrum" wrote in message ... Brian, Just by looking at that schematic, where would I stop building if I only wanted the VFO to use on a simple transmitter? I looked it over, and have a pretty good guess, but I'm not certain. Thanks. "Brian" wrote in message nk.net... I grabbed the Tin Ear docs too...I think I will try to build this little receiver from my parts pile. I need another receiver like I need a hole in the head but what the heck...looks fun. "J Shrum" wrote in message ... Agreed! Paul, That tin ear is perfect... That is exactly the PTO I was looking for. I'll give that one a shot. Thanks for everyone... KC9FFX "Brian" wrote in message nk.net... I prefer building stuff out of my junk pile. I do get a greater feeling of satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 "J Shrum" wrote in message ... Point taken. But my goal at this point is to build w/ salvaged parts from my mound of junk... |
James,
I printed out the docs today....lemme look at it. Good question... "J Shrum" wrote in message ... Brian, Just by looking at that schematic, where would I stop building if I only wanted the VFO to use on a simple transmitter? I looked it over, and have a pretty good guess, but I'm not certain. Thanks. "Brian" wrote in message nk.net... I grabbed the Tin Ear docs too...I think I will try to build this little receiver from my parts pile. I need another receiver like I need a hole in the head but what the heck...looks fun. "J Shrum" wrote in message ... Agreed! Paul, That tin ear is perfect... That is exactly the PTO I was looking for. I'll give that one a shot. Thanks for everyone... KC9FFX "Brian" wrote in message nk.net... I prefer building stuff out of my junk pile. I do get a greater feeling of satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 "J Shrum" wrote in message ... Point taken. But my goal at this point is to build w/ salvaged parts from my mound of junk... |
Just by looking at that schematic, where would I stop building if I only
wanted the VFO to use on a simple transmitter? I looked it over, and have a pretty good guess, but I'm not certain. IMHO, it to me as if: Q1 is the local oscillator VFO Q2 is the mixer (it's the only xstr that gets anything from Q1; because of capacitors C9 and C10, the bottom end of R3 and the bottom end of Q3 are essentially at ground potential to RF) Q3 is the RF amplifier Q4 is the AF amplifier Qrest are elements of a push-pull AF output amplifier --Myron A. Calhoun, W0PBV. -- Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
Just by looking at that schematic, where would I stop building if I only
wanted the VFO to use on a simple transmitter? I looked it over, and have a pretty good guess, but I'm not certain. IMHO, it to me as if: Q1 is the local oscillator VFO Q2 is the mixer (it's the only xstr that gets anything from Q1; because of capacitors C9 and C10, the bottom end of R3 and the bottom end of Q3 are essentially at ground potential to RF) Q3 is the RF amplifier Q4 is the AF amplifier Qrest are elements of a push-pull AF output amplifier --Myron A. Calhoun, W0PBV. -- Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
"Brian" wrote in message nk.net... I prefer building stuff out of my junk pile. I do get a greater feeling of satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 Cheaper, too. There's three dollars worth of parts there. |
"Brian" wrote in message nk.net... I prefer building stuff out of my junk pile. I do get a greater feeling of satisfaction when I can dive into the pile on hand and build something that works. It's more fun that way! 73 Cheaper, too. There's three dollars worth of parts there. |
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