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

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