Topics

BitX17 IF Frequency


Greg Derda
 

Now that I have completed my BitX20a, I have started another BitX using the Far Circuits boards, and I would like to build this one for 17 meters. I've found some very useful information in the messages, files, and photos archives of this group, but so far, I have not seen mention of the IF frequencies people have used for 17m. Although I have a couple of potential DDS options available to me, I don't know that I want to use such a "valuable resource" on the narrow bandspread of a 17m rig.

Options that come to mind for a traditional IF/LO combination are (presuming a 18.1Mhz target):

IF LO
---- ----
10 8.1
12 6.1
16 2.1
14.76 3.34 (chosen as an oddball example using available oddball crystals).

I don't see many HF VFO's in the 8Mhz range, so I am guessing it is not common. I have crystals for the latter two options easily available to me and am leaning toward one of them.

I guess that instead of babbling on with guesses, I'd like to just ask......

Does anybody have suggestions for a good IF/LO combination?

Thanks,
Greg
ki4mmm


Martien <sproet01@...>
 

--- In BITX20@..., Greg Derda <gderda@...> wrote:
Hello Greg,

You could use the 10MHz standard with an 8Mhz VFO. This VFO can be
easily stabilised using a "Huff and Puff" circuit. There are many
examples on the web. I used this simple one (fig.1 schematic)):
http://home.hetnet.nl/~brink120/huf2.htm
VFO is rock solid, PSK 31 is no problem.

Text is in Dutch but the schematics are quite clear.

Martien PE1BWI


Ron [W5RCM / ZS1MCD] <w5rcm@...>
 

10 MHz IFs in the US can be problematic with WWV broadcasting there.
--
72, Ron McDowell - W5RCM / ZS1MCD
Austin TX / Hermanus ZA
w5rcm [at] Ham-Stuff [dot] NET

Greg Derda wrote:

Now that I have completed my BitX20a, I have started another BitX using the Far Circuits boards, and I would like to build this one for 17 meters. I've found some very useful information in the messages, files, and photos archives of this group, but so far, I have not seen mention of the IF frequencies people have used for 17m. Although I have a couple of potential DDS options available to me, I don't know that I want to use such a "valuable resource" on the narrow bandspread of a 17m rig.

Options that come to mind for a traditional IF/LO combination are (presuming a 18.1Mhz target):

IF LO
---- ----
10 8.1
12 6.1
16 2.1
14.76 3.34 (chosen as an oddball example using available oddball crystals).

I don't see many HF VFO's in the 8Mhz range, so I am guessing it is not common. I have crystals for the latter two options easily available to me and am leaning toward one of them.

I guess that instead of babbling on with guesses, I'd like to just ask......

Does anybody have suggestions for a good IF/LO combination?

Thanks,
Greg
ki4mmm


Greg Derda
 

Martien,

Thank you for the reply and info. I have considered a stabilizer, and
I have tried to learn more about them, but what is not clear to me is
where to tap the VFO for the output to, and input from, the stabilizer.
For example, if a person wanted to add one to the Farhan-circuit VFO,
where would you tap it?

Greg
ki4mmm

On Feb 15, 2008, at 10:25 AM, Martien wrote:

--- In BITX20@..., Greg Derda <gderda@...> wrote:
Hello Greg,

You could use the 10MHz standard with an 8Mhz VFO. This VFO can be
easily stabilised using a "Huff and Puff" circuit. There are many
examples on the web. I used this simple one (fig.1 schematic)):
http://home.hetnet.nl/~brink120/huf2.htm
VFO is rock solid, PSK 31 is no problem.

Text is in Dutch but the schematics are quite clear.

Martien PE1BWI



n7ve <dan.Tayloe@...>
 

I would think a 13 MHz IF would reasonably work well with a 5 MHz VFO.
There are 13 MHz crystals available in the 13 MHz range.

Mouser has 12.96 MHz crystals in stock, 520-HCU1296-18X. This would
place the 3rd harmonic of the VFO at 15 MHz, and the 4th at 20 MHz, to
move it as far as possible from 18 MHz. Running the VFO at 5 MHz is
not too bad.

- Dan, N7VE

--- In BITX20@..., "Ron [W5RCM / ZS1MCD]" <w5rcm@...> wrote:

10 MHz IFs in the US can be problematic with WWV broadcasting there.
--
72, Ron McDowell - W5RCM / ZS1MCD
Austin TX / Hermanus ZA
w5rcm [at] Ham-Stuff [dot] NET

Greg Derda wrote:
Now that I have completed my BitX20a, I have started another BitX
using
the Far Circuits boards, and I would like to build this one for 17
meters. I've found some very useful information in the messages,
files, and photos archives of this group, but so far, I have not seen
mention of the IF frequencies people have used for 17m. Although I
have a couple of potential DDS options available to me, I don't know
that I want to use such a "valuable resource" on the narrow
bandspread
of a 17m rig.

Options that come to mind for a traditional IF/LO combination are
(presuming a 18.1Mhz target):

IF LO
---- ----
10 8.1
12 6.1
16 2.1
14.76 3.34 (chosen as an oddball example using available oddball
crystals).

I don't see many HF VFO's in the 8Mhz range, so I am guessing it
is not
common. I have crystals for the latter two options easily
available to
me and am leaning toward one of them.

I guess that instead of babbling on with guesses, I'd like to just
ask......

Does anybody have suggestions for a good IF/LO combination?

Thanks,
Greg
ki4mmm


Arv Evans
 

Greg

My latest BITX20A H&P stabilizer taps the VFO output at the junction of
R-27 and Q-6 collector (top of R-27 on the kit circuit board). I fed
the common point between H&P integrator caps to a 150K resistor that
connects to the junction of R-38 and D-9.

At present I am using the G8SEQ idea

<http://downloads.hanssummers.com/sprat122b.pdf>

of an intact watch unit providing 32 Hz reference with half a 74HC74 as
the latch. The other half of the 74HC74 is used as a buffer to square up
the VFO output.

The Ron Brink PA2RF circuit is probably a more elegant solution, but
this simpler method seems to work well enough for my needs.

Arv
_._


Greg Derda wrote:


Martien,

Thank you for the reply and info. I have considered a stabilizer, and
I have tried to learn more about them, but what is not clear to me is
where to tap the VFO for the output to, and input from, the stabilizer.
For example, if a person wanted to add one to the Farhan-circuit VFO,
where would you tap it?

Greg
ki4mmm

On Feb 15, 2008, at 10:25 AM, Martien wrote:

--- In BITX20@... <mailto:BITX20%40yahoogroups.com>,
Greg Derda <gderda@...> wrote:
Hello Greg,

You could use the 10MHz standard with an 8Mhz VFO. This VFO can be
easily stabilised using a "Huff and Puff" circuit. There are many
examples on the web. I used this simple one (fig.1 schematic)):
http://home.hetnet.nl/~brink120/huf2.htm
<http://home.hetnet.nl/%7Ebrink120/huf2.htm>
VFO is rock solid, PSK 31 is no problem.

Text is in Dutch but the schematics are quite clear.

Martien PE1BWI




--
======================================
Web: http://K7HKL.homelinux.net
http://bitx20a.livejournal.com
http://home.earthlink.net/~arvevans/
http://www.geocities.com/k7hkl_arv/
======================================


Jim Kortge <jokortge@...>
 

n7ve wrote:
I would think a 13 MHz IF would reasonably work well with a 5 MHz VFO.
There are 13 MHz crystals available in the 13 MHz range.
Mouser has 12.96 MHz crystals in stock, 520-HCU1296-18X. This would
place the 3rd harmonic of the VFO at 15 MHz, and the 4th at 20 MHz, to
move it as far as possible from 18 MHz. Running the VFO at 5 MHz is
not too bad.
- Dan, N7VE
Another combination that might work well is a 22.11 MHz Super VXO (with two matched crystals) and the IF at 4 MHz. The VXO should eliminate the need for that H&P circuitry. There are probably other combinations that would also work well.

72,

Jim, K8IQY


Greg Derda
 

Thanks to all who have replied so far!

Arv,

Thank you, this is what just I needed to help visualize the whole
process! Now i can stare at the schematics and figure out what is
going on. I actually have a "spare" stabilizer from my build of a WN5Y
ELR kit (long story - I ended up with two stabilizers). Picture is
here...

http://jezebel.ucns.uga.edu/~derda/elr/P6200001.JPG

I thought about using it (once I figured out "how") with my BitX20a,
but I am very happy with the stability of that radio. Of course, I am
telling myself that I might build my third Bitx (I ordered the version
3 boards from Sunil) for PSK31, so I might want to use it there ;-).

Anyway, thanks again, I think I have enough information to keep my
noodle turning for a while.....

Greg
ki4mmm

On Feb 15, 2008, at 2:16 PM, Arv Evans wrote:

Greg

My latest BITX20A H&P stabilizer taps the VFO output at the junction
of
R-27 and Q-6 collector (top of R-27 on the kit circuit board). I fed
the common point between H&P integrator caps to a 150K resistor that
connects to the junction of R-38 and D-9.

At present I am using the G8SEQ idea

<http://downloads.hanssummers.com/sprat122b.pdf>

of an intact watch unit providing 32 Hz reference with half a 74HC74
as
the latch. The other half of the 74HC74 is used as a buffer to square
up
the VFO output.

The Ron Brink PA2RF circuit is probably a more elegant solution, but
this simpler method seems to work well enough for my needs.

Arv
_._

Greg Derda wrote:
>
> Martien,
>
> Thank you for the reply and info. I have considered a stabilizer,
and
> I have tried to learn more about them, but what is not clear to me
is
> where to tap the VFO for the output to, and input from, the
stabilizer.
> For example, if a person wanted to add one to the Farhan-circuit
VFO,
> where would you tap it?
>
> Greg
> ki4mmm
>
> On Feb 15, 2008, at 10:25 AM, Martien wrote:
>
> > --- In BITX20@... <mailto:BITX20%40yahoogroups.com>,
> Greg Derda <gderda@...> wrote:
> > Hello Greg,
> >
> > You could use the 10MHz standard with an 8Mhz VFO. This VFO can be
> > easily stabilised using a "Huff and Puff" circuit. There are many
> > examples on the web. I used this simple one (fig.1 schematic)):
> > http://home.hetnet.nl/~brink120/huf2.htm
> <http://home.hetnet.nl/%7Ebrink120/huf2.htm>
> > VFO is rock solid, PSK 31 is no problem.
> >
> > Text is in Dutch but the schematics are quite clear.
> >
> > Martien PE1BWI
> >
> >
> >
>
>
>
>

--
======================================
Web: http://K7HKL.homelinux.net
http://bitx20a.livejournal.com
http://home.earthlink.net/~arvevans/
http://www.geocities.com/k7hkl_arv/
======================================





Ashhar Farhan <farhan@...>
 

it is best to use as high an IF as is possible. At higher frequencies, the
pass-band appears to be narrower, hence the phase delay is better and the
skirt is better. I would imagine that the PC's standard 14.318 MHz crystals
are ideal. going higher in IF would compromise your Image rejection (for
instance, with 16MHz IF, the 18 MHz will have an image at 14 Mhz).

- farhan

On Feb 16, 2008 1:14 AM, Greg Derda <gderda@...> wrote:

Thanks to all who have replied so far!

Arv,

Thank you, this is what just I needed to help visualize the whole
process! Now i can stare at the schematics and figure out what is
going on. I actually have a "spare" stabilizer from my build of a WN5Y
ELR kit (long story - I ended up with two stabilizers). Picture is
here...

http://jezebel.ucns.uga.edu/~derda/elr/P6200001.JPG<http://jezebel.ucns.uga.edu/%7Ederda/elr/P6200001.JPG>

I thought about using it (once I figured out "how") with my BitX20a,
but I am very happy with the stability of that radio. Of course, I am
telling myself that I might build my third Bitx (I ordered the version
3 boards from Sunil) for PSK31, so I might want to use it there ;-).

Anyway, thanks again, I think I have enough information to keep my
noodle turning for a while.....

Greg
ki4mmm

On Feb 15, 2008, at 2:16 PM, Arv Evans wrote:

Greg

My latest BITX20A H&P stabilizer taps the VFO output at the junction
of
R-27 and Q-6 collector (top of R-27 on the kit circuit board). I fed
the common point between H&P integrator caps to a 150K resistor that
connects to the junction of R-38 and D-9.

At present I am using the G8SEQ idea

<http://downloads.hanssummers.com/sprat122b.pdf>

of an intact watch unit providing 32 Hz reference with half a 74HC74
as
the latch. The other half of the 74HC74 is used as a buffer to square
up
the VFO output.

The Ron Brink PA2RF circuit is probably a more elegant solution, but
this simpler method seems to work well enough for my needs.

Arv
_._

Greg Derda wrote:

Martien,

Thank you for the reply and info. I have considered a stabilizer,
and
I have tried to learn more about them, but what is not clear to me
is
where to tap the VFO for the output to, and input from, the
stabilizer.
For example, if a person wanted to add one to the Farhan-circuit
VFO,
where would you tap it?

Greg
ki4mmm

On Feb 15, 2008, at 10:25 AM, Martien wrote:

--- In BITX20@... <BITX20%40yahoogroups.com> <mailto:
BITX20%40yahoogroups.com>,
Greg Derda <gderda@...> wrote:
Hello Greg,

You could use the 10MHz standard with an 8Mhz VFO. This VFO can be
easily stabilised using a "Huff and Puff" circuit. There are many
examples on the web. I used this simple one (fig.1 schematic)):
http://home.hetnet.nl/~brink120/huf2.htm<http://home.hetnet.nl/%7Ebrink120/huf2.htm>
<http://home.hetnet.nl/%7Ebrink120/huf2.htm>
VFO is rock solid, PSK 31 is no problem.

Text is in Dutch but the schematics are quite clear.

Martien PE1BWI




--
======================================
Web: http://K7HKL.homelinux.net
http://bitx20a.livejournal.com
http://home.earthlink.net/~arvevans/<http://home.earthlink.net/%7Earvevans/>
http://www.geocities.com/k7hkl_arv/
======================================