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Re: BITX17

Ron
 

Hi Ruud,

First of all; hartelijk dank voor alle info, leuk om ham uit PA-land
hier te ontmoeten!
I really appreciate the good information you provided. Had a quick
look at your interface drawings which look very profi. I am in the
early stage of building the rig. I choose for the 18MHz WARC band
because I do not have equipment for this part of the spectrum yet and
i do not know what to expect (which is exciting). I finished PSU, LF
amp, (mechanics and part of electronics) for VFO which I think is not
stable enough yet (shortterm drift of 300Hz); so next step is to
include the huffandpuff circuit ("bijsloffer") from om pa0ksb in
order to obtain a drift less than 10 Hz (optimistic??). I started
with this module yesterday; found a nice 32MHz local oscillator on an
old PC board for reference oscillator which works fine. Rest of
hufenpuf components to be shipped in next week.
OK about PSK... I have very nice experience with MixW2.1 with
digimodes (rtty, psk31) and cwget and cwtype running on an old
Celeron 266 MHz pc ;i coupled this pc to a Kenwood TS515 from 1972
with tubes and made lots of qso's past year (on 80-40-20-15m) and cw
qso on a homebrew 30m xtal trscvr. I will keep all your good advice
in mind when i will be working on the interface, but first things
first. I am surprised you are using the vxo on 24 MHz. Did you
already make a qso with your bitx? Or are you still in the building
phase?
Bye for now and till next time,
Ron
PA2RF


--- In BITX20@..., "Ruud Jongeling" <pe2bs@t...> wrote:

Hi Ron,

Although al bit late I may have some suggestions for PSK. I also
build a BITX20 for PSK. Last weekend I completed the interface from
the TRCV to the soundcard. The schema is uploaded as a PDF file in
the file-box.

Some remarks:
- To avoid "earthloops" effects I used two tr's 1:1 from an old
computerswitchingsupply. I also used an optocopler from the same
supply. You can recognize the optcoplers by the DIL6 package. (pin
1
Anode D, pin 2 Cathode D, pin 3 NC, pin 4 Emitter T, pin 5
Collector
T, pin 6 Base T).
- You can easily check for low frequency sounds (earthloop and
others, special lower than 500 Hz!!) by using the waterfalldiagram
in
HamScope. No lines no sound. To avoid every possibility I used 3u3
capacitors between the stages of LF. The low frequency's below
500Hz
are almost blocked. (See picture HamScope in picture box).
- The signal send to the computer by Line in comes back by Line
out.
To my suprise came peaks of the signal through T6 and T5 to T4.
Oscillation was the result. T3 was added as a switch.
- When I used SpectrumAnalyzer I saw a peak in the signal I first
could not explain (see picture in the picture box). After a while I
discovered that the output impedance of the LM386 did not match
with
Tr2. First I added a variable resistance. The value had great
affect
on the frequency spectrum! Check with SpectrumAnalyzer. R18=33 ohm
was the best in my situation.
- The oscilator in my BITX20 will (if possible) be a VXO on 24MHz.
The reason for this is simple: lots of cristals in the junkbox and
a
good supression of the signal by the Pi-filter. I can vary tot 5
kHz
when I use three crystals. But the frequency of the oscilator also
goes about 5 Kc up when a crystal is added!
The VXO is not ready yet. I still have to work for enough output
for
the balance mixer.
With CWGet it is possible to decode CW in the first part of the
band.
When everything is working well iI wil order a special crystal for
PSK.

73,

Ruud
PE2BS


--- In BITX20@..., Ron Brink <pa2rf@y...> wrote:
Dear bitx20 homebrewers,
I intend to build the BITX for the 17m WARC band (18.068-18.168
MHz). My ultimate goal will be to work psk31 with this splendid
rig.
Has anyone suggestions to convert bitx20 to bitx17. VFO must be
changed of course and RF filters... I intend to keep my progress
updated on my website (see below).
73 de Ron
PA2RF
pa2rf@y...





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Re: BITX17

Ruud Jongeling
 

Hi Ron,

Although al bit late I may have some suggestions for PSK. I also
build a BITX20 for PSK. Last weekend I completed the interface from
the TRCV to the soundcard. The schema is uploaded as a PDF file in
the file-box.

Some remarks:
- To avoid "earthloops" effects I used two tr's 1:1 from an old
computerswitchingsupply. I also used an optocopler from the same
supply. You can recognize the optcoplers by the DIL6 package. (pin 1
Anode D, pin 2 Cathode D, pin 3 NC, pin 4 Emitter T, pin 5 Collector
T, pin 6 Base T).
- You can easily check for low frequency sounds (earthloop and
others, special lower than 500 Hz!!) by using the waterfalldiagram in
HamScope. No lines no sound. To avoid every possibility I used 3u3
capacitors between the stages of LF. The low frequency's below 500Hz
are almost blocked. (See picture HamScope in picture box).
- The signal send to the computer by Line in comes back by Line out.
To my suprise came peaks of the signal through T6 and T5 to T4.
Oscillation was the result. T3 was added as a switch.
- When I used SpectrumAnalyzer I saw a peak in the signal I first
could not explain (see picture in the picture box). After a while I
discovered that the output impedance of the LM386 did not match with
Tr2. First I added a variable resistance. The value had great affect
on the frequency spectrum! Check with SpectrumAnalyzer. R18=33 ohm
was the best in my situation.
- The oscilator in my BITX20 will (if possible) be a VXO on 24MHz.
The reason for this is simple: lots of cristals in the junkbox and a
good supression of the signal by the Pi-filter. I can vary tot 5 kHz
when I use three crystals. But the frequency of the oscilator also
goes about 5 Kc up when a crystal is added!
The VXO is not ready yet. I still have to work for enough output for
the balance mixer.
With CWGet it is possible to decode CW in the first part of the band.
When everything is working well iI wil order a special crystal for
PSK.

73,

Ruud
PE2BS


--- In BITX20@..., Ron Brink <pa2rf@y...> wrote:
Dear bitx20 homebrewers,
I intend to build the BITX for the 17m WARC band (18.068-18.168
MHz). My ultimate goal will be to work psk31 with this splendid rig.
Has anyone suggestions to convert bitx20 to bitx17. VFO must be
changed of course and RF filters... I intend to keep my progress
updated on my website (see below).
73 de Ron
PA2RF
pa2rf@y...





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Re: Recycling monitors

Hans Summers
 

P.S. For those who don't get attached pictures, they're also in the group
photos under G0UPL/recycle

73 Hans

-----Original Message-----
From: Hans Summers
Sent: 08 February 2005 17:56
To: 'BITX20@...'
Subject: OT: Recycling monitors



Latest news, following Paolo's influence: I have commenced dismantling of
the previously mentioned 19-inch DELL monitor, which the IT department
failed to remove from the cupboard next to my desk here in the office!

Inside I found a secondary RF shielded box made from thin sheet metal. Very
difficult to remove. Attached are the pictures so far. You can see that I
managed to open 1 side of the RF shield box and see the back of the PCB.
Still haven't glimpsed the front of the PCB. I will make a page on my site
about this, following Paulo's example, and list the useful things I find
inside! Later, I will add links to that pages, to other projects on my
website, to show where I used the parts. Recycling is fun! I've been using
old recycled parts for all of my electronics hobby since I was 5 or 6 years
old. Now it's time to document this side of things!

73 for now

Hans G0UPL


-----Original Message-----
From: Paolo Cravero as2594 [mailto:pcravero@...]
Sent: 03 February 2005 17:52
To: BITX20@...
Subject: Re: [BITX20] Stability?



Hans Summers wrote:

IT department still haven't taken it, I might be found harvesting
useful
components from the monitor for homebrew projects! The wire in the field
deflection coils are useful for winding coils from. There must be other
useful stuff in there too!
Been there! :-) And written about it. See


Also featured: VCR, CD-ROM and laptop. One day I will add TV and
floppy-disk drives as well.

Paolo IK1ZYW

PS: when I dismantled that monitor I was not yet into winding coils, so
I just kept the inductors, which I am now using as wire source.

PPS: hot-air guns are a great tool for part scrounging! (but you MUST do
it in open-air and dry WX ;-) )



Yahoo! Groups Links
OT: Recycling monitors

Hans Summers
 

Latest news, following Paolo's influence: I have commenced dismantling of
the previously mentioned 19-inch DELL monitor, which the IT department
failed to remove from the cupboard next to my desk here in the office!

Inside I found a secondary RF shielded box made from thin sheet metal. Very
difficult to remove. Attached are the pictures so far. You can see that I
managed to open 1 side of the RF shield box and see the back of the PCB.
Still haven't glimpsed the front of the PCB. I will make a page on my site
about this, following Paulo's example, and list the useful things I find
inside! Later, I will add links to that pages, to other projects on my
website, to show where I used the parts. Recycling is fun! I've been using
old recycled parts for all of my electronics hobby since I was 5 or 6 years
old. Now it's time to document this side of things!

73 for now

Hans G0UPL

-----Original Message-----
From: Paolo Cravero as2594 [mailto:pcravero@...]
Sent: 03 February 2005 17:52
To: BITX20@...
Subject: Re: [BITX20] Stability?



Hans Summers wrote:

IT department still haven't taken it, I might be found harvesting
useful
components from the monitor for homebrew projects! The wire in the field
deflection coils are useful for winding coils from. There must be other
useful stuff in there too!
Been there! :-) And written about it. See


Also featured: VCR, CD-ROM and laptop. One day I will add TV and
floppy-disk drives as well.

Paolo IK1ZYW

PS: when I dismantled that monitor I was not yet into winding coils, so
I just kept the inductors, which I am now using as wire source.

PPS: hot-air guns are a great tool for part scrounging! (but you MUST do
it in open-air and dry WX ;-) )



Yahoo! Groups Links
Far Circuit Board

[email protected]
 

Is it possible for someone to post a picture of the FAR BITX PCB ?
Or is there a website that shows it ? I would like to see what it
looks like before ordering one.
Thanks,
Steve
K1EL
Re: LF amp for BITX17

Ron
 

Hi agn!
I just added circuits of the LA4185 audio amplifier and ( intend to
build) pa0ksb huff & puff to the Photo directory. Audio amp is
working fine now. Still waiting for the huff&puff components
(Conrad... wakie-wakie !.
Demolished a defective AV-unit from akai yesterday (found the box
near a carbage lit) and there were a lot of nice components in it
like three nice ring-cores, LEDs, relais, cooling profile, cinch
busses lots of screws and washers and so on .
Bye
Ron
PA2RF
Re: Typo in suggested RIT circuit?

Arvid Evans
 

Paolo

I just uploaded a corrected file. Sorry about the confusion. That
error came from my use of a then new CAD program, not from anything on
K8IQY's web page, so it was my mistake.

Arv
_._

--- In BITX20@..., Paolo Cravero as2594 <pcravero@a...> wrote:
Hi (Arv)
While browsing through the files repository for BITX20 I found a
mistake
in "K8IQY RIT Circuit.png" at


D2 and D3 are zeners, which are drawn backwards in the diagram, or am I
wrong?

73,
Paolo IK1ZYW
New file uploaded to BITX20

[email protected]
 

Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the BITX20
group.

File : /MODIFICATIONS/RIT-K8IQY.png
Uploaded by : k7hkl_arv <arvevans@...>
Description : RIT Circuit from K8IQY's Web Page

You can access this file at the URL:


To learn more about file sharing for your group, please visit:


Regards,

k7hkl_arv <arvevans@...>
Typo in suggested RIT circuit?

Paolo Cravero as2594
 

Hi (Arv)
While browsing through the files repository for BITX20 I found a mistake in "K8IQY RIT Circuit.png" at

D2 and D3 are zeners, which are drawn backwards in the diagram, or am I wrong?

73,
Paolo IK1ZYW
LF amp for BITX17

Ron Brink
 

Hello fellow homebrewers,
While waiting for the huff and puff components, i decided to finsih the LF amplifier. Instead of the LM386, I found an LA4185 in my junkbox from an old demolished transistor radio. Google helped me to find the proper circuit for it, and I ended up with a nice 4 Watts LF amp with very few extra components (of course I used the ' dead bug' method to combine the components). I like the internet !! Nice hum and rattle while using the wet finger on the LF amp's input! Hopefully the extra LF watts provide me comfortable listening in future.
Bye for now and enjoy homebrewing
and remember do not throw away or waste old electoronic stuff. there comes a moment you are going to use the components derived from the boxes !
Ron from Holland
73
PA2RF
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Non inductive resistors

Raj
 

Jim,

We used to make non inductive resistors specially for some clients in the '80's. In general purpose carbon or metal film resistors, the body is spiral cut at least 60% of the body length. Less than 60% cuts results in lower temperature stability. This is not a problem in low values, so we slowed the cutting spindle and allowed the blade to spiral less than one turn.. this means that the path of least resistance was a straight line.. therefore minimum inductance. We used to charge a lot for them because the production was slow.

Actually there was a magical smoke test on the final paint line. We applied a brief 250V pulse to the resistors, defective ones went up in a flash.

A bit of trivia, in small resistors the major cost is the copper leads! the end user cuts most of it and discards.

73 Raj vu2zap

At 06/02/2005, you wrote:


On Feb 5, 2005, at 10:58 AM, Raj wrote:

Nope, I was in the resistor manufacturing field. I was
managing a
factory some years ago.. from the time the resistive element is put on
to
the end of painting the value on it.. the orientation of clockwise or
anticlockwise is lost.
Where I work, we have a problem w/ some fiber optic transceivers so
we're hand-testing parts for one customer to provide parts that work
just for them, and binning the rest by performance numbers. I think
it's by 0.1 dB on one component of RGB, but I'm just the technical
writer.

Where we're at in amateur radio, we essentially hand sort EVERY part,
and I think it'd be fun to pick through a batch of surplus resistors,
turn them this way and that, and install them in the best direction and
orientation for the application at hand.

You ARE right -- if your manufacturing process delivers a wire-wound
resistor core that can be turned either way in its final enclosure, and
it's not specified for inductance or direction of winding, then
there's no reason to care.

For wire-wound resistors used as RF chokes, like the Ohmite Z-series
resistors used for parasitic suppression in sweep-tube RF amplifiers in
the 1960s and 1970s, the winding orientation did not matter because
they were not close enough to anything to induce coupling.

It's really good to know that we have people on this group who know
what's inside our electronic components.

Besides that magical smoke ...


72/73

Jim N6OTQ
Re: Hi power resistors from switching PSU

[email protected]
 

On Feb 5, 2005, at 10:58 AM, Raj wrote:

Nope, I was in the resistor manufacturing field. I was managing a
factory some years ago.. from the time the resistive element is put on to
the end of painting the value on it.. the orientation of clockwise or
anticlockwise is lost.
Where I work, we have a problem w/ some fiber optic transceivers so we're hand-testing parts for one customer to provide parts that work just for them, and binning the rest by performance numbers. I think it's by 0.1 dB on one component of RGB, but I'm just the technical writer.

Where we're at in amateur radio, we essentially hand sort EVERY part, and I think it'd be fun to pick through a batch of surplus resistors, turn them this way and that, and install them in the best direction and orientation for the application at hand.

You ARE right -- if your manufacturing process delivers a wire-wound resistor core that can be turned either way in its final enclosure, and it's not specified for inductance or direction of winding, then there's no reason to care.

For wire-wound resistors used as RF chokes, like the Ohmite Z-series resistors used for parasitic suppression in sweep-tube RF amplifiers in the 1960s and 1970s, the winding orientation did not matter because they were not close enough to anything to induce coupling.

It's really good to know that we have people on this group who know what's inside our electronic components.

Besides that magical smoke ...


72/73

Jim N6OTQ
Re: Hi power resistors from switching PSU

Raj
 

Jim,

Nope, I was in the resistor manufacturing field. I was managing a factory some years ago.. from the time the resistive element is put on to the end of painting the value on it.. the orientation of clockwise or anticlockwise is lost.

On wire wounds of certain types. The wire is clearly visible below the paint and it may be possible to determine whether its going clockwise or not and allow you to select them accordingly..

73 Raj vu2zap

At 05/02/2005, you wrote:


I suspect that if you wired the resistors in parallel on a 50-ohm
stripline PC board with the connectors X-ed on opposite sides of the
board, you could cancel out a lot of the inductance. It would also be
theoretically possible to add a variable capacitor to cancel out the
inductive reactance and get a higher usable frequency at lower SWRs, at
the penalty of making the load frequency-dependent.
Re: Hi power resistors from switching PSU

[email protected]
 

On Feb 4, 2005, at 1:12 AM, Paolo Cravero as2594 wrote:

I'd like to remind you a simple study I made on two
100ohm 5W resistors found in a PC monitor PSU.

See (part
of the page is in Italian, ROS=SWR in tables)

Basically those "inductive" resistors can be used to form cheap QRP *HF*
dummy loads, with SWR <1.3:1 at 30MHz.

I installed my RF voltage probe on that load, and that is the way I
measure (ehm, estimate) my circuits' output power.
A wonderful idea!

I suspect that if you wired the resistors in parallel on a 50-ohm stripline PC board with the connectors X-ed on opposite sides of the board, you could cancel out a lot of the inductance. It would also be theoretically possible to add a variable capacitor to cancel out the inductive reactance and get a higher usable frequency at lower SWRs, at the penalty of making the load frequency-dependent.

An indexed dial for the variable capacitor would fix that. If it were a fixed-frequency load. tune it once and forget it.

Jim N6OTQ
Re: From the mouths of babes...

Hans Summers
 

开云体育

?
That's fantastic Farhan!
?
I didn't even know that polo's could be found outside the UK! When my brothers and I were kids and used to visit our Grandparents, my Grandmother would always give us each a tube of polo's to eat on the drive home. I love the idea, I will have to try it sometime! A tube of polos would have enough mints to build more than one BITX20, and are much cheaper than tap washers!
?
73 Hans G0UPL

-----Original Message-----
From: Arv Evans [mailto:arvevans@...]
Sent: 03 February 2005 19:41
To: BITX
Subject: Re: [BITX20] From the mouths of babes...

Farhan

That has got to be the sweetest transceiver I have ever heard of!

Arv
_._
On Thu, 2005-02-03 at 00:27, Ashhar Farhan wrote:
i was fooling around with a direct conversion receiver in my shack today
when my four year old daughter came in with her friends to play
'wheelie train' (a noisy sport where each participant sits in an office
chair holding onto the next one's chair and the front engine pulls
everyone around the room).

i was just about to ask them to go out to play, to let me play my thing,
when i was offered ... a polo. the mint with a hole.

it immediately went into the direct conversion receiver as a VFO coil.
quite stable.

now, a single roll will be enough to build the entire BITX, although I am
not sure of the losses. You will have to cover it with some epoxy
paint/glue to make sure that ants dont eat up your rig.

i will report back from the toroid sucking convention soon.

- farhan




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Re: Stability?

Hans Summers
 

Thanks Paolo!

Reading your web page has inspired me to bring forward my imaginary deadline
to the IT department! The monitor is now on death row, awaiting demolition.
Those IT boys now have very little time remaining to rescue their monitor
and transport it to safety... I will let you know what I find inside!

73 Hans G0UPL

-----Original Message-----
From: Paolo Cravero as2594 [mailto:pcravero@...]
Sent: 03 February 2005 17:52
To: BITX20@...
Subject: Re: [BITX20] Stability?



Hans Summers wrote:

IT department still haven't taken it, I might be found harvesting
useful
components from the monitor for homebrew projects! The wire in the field
deflection coils are useful for winding coils from. There must be other
useful stuff in there too!
Been there! :-) And written about it. See


Also featured: VCR, CD-ROM and laptop. One day I will add TV and
floppy-disk drives as well.

Paolo IK1ZYW

PS: when I dismantled that monitor I was not yet into winding coils, so
I just kept the inductors, which I am now using as wire source.

PPS: hot-air guns are a great tool for part scrounging! (but you MUST do
it in open-air and dry WX ;-) )



Yahoo! Groups Links
Hi power resistors from switching PSU

Paolo Cravero as2594
 

While I am at it, I'd like to remind you a simple study I made on two 100ohm 5W resistors found in a PC monitor PSU.

See (part of the page is in Italian, ROS=SWR in tables)

Basically those "inductive" resistors can be used to form cheap QRP *HF* dummy loads, with SWR <1.3:1 at 30MHz.

I installed my RF voltage probe on that load, and that is the way I measure (ehm, estimate) my circuits' output power.

Have a nice day,
Paolo IK1ZYW
Re: Stability?

Ron Brink
 

OK Hans,
Tnx for advice. Nice dds design, but i will first try what is possible with the 4-ic huff and puff (2x 74hc4060, 74hc74+opamp). I do not want to make things too fancy for a starter. Maybe later.
Yesterday i inserted some polysterene cap's and glued (bizon kit!) ?the fixed value coil to the pcb. Stability really improved. A trial of one hour showed about 300 Hz drift. Adding the huff and puff circuitry should further improve the situation. Maybe soldering a box from unetched pcb material around the vfo helps too.
Good homebrewing and best wishes from Holland
Ron
PA2RF

Hans Summers wrote:
?
Ron, Raj...
?
I have a simple DDS design too, which doesn't need microprocessors: ?. It would be possible to replace the DIP switches with up/down counters, driven perhaps by an optical shaft encoder. Not an optical encoder you buy very expensively! There are two in every computer mouse, available usually as free scrap. Just a little work required to convert it into a shaft encoder.
?
Personally though I am still nervous about the noise and spurious outputs from DDS generators. I'm Ok with using it in a transmitter but I'd worry about using it in a receiver and degrading performance. Perhaps I'm just paranoid. Mine is currently driving my QRSS beacon ?which is currently QRV on 10,140,050 MHz with 250mW to an indoor attic dipole.
?
73 Hans G0UPL
-----Original Message-----
From: Raj [mailto:ggrk@...]
Sent: 03 February 2005 15:04
To: BITX20@...
Subject: Re: [BITX20] Stability?

Ron,

????????Reminds me of the old days as a youngster building Valve VFO, enclosing it in a box etc.. For PSK: I suggest that you take this requirement to the another extreme and build a DDS VFO !!! Not Joking, its actually the best of both worlds.. Its tough to make a VFO with 10Hz stability.

????????Try replacing the 56pf next to Q5 with polystyrene.. it should give your major improvement.

????????No recent experience with digital. I used to run a bbs till some years ago..

73 Raj vu2zap

At 03/02/2005, you wrote:

?
attachments from unrecognized senders? ***

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Re: Stability?

Raj
 

Good idea and simple too, the digital activity is in a narrow part of the spectrum on 20M. A VXO should be good enough. 2 xtals should cover sub-band confortably..

I expect that the VFO coil can be replace with a xtal and it should work with minor change of values.

Farhan?

73
Raj

And how about a VXO?
Chris.

For PSK: I suggest that you take this
requirement to the another extreme and build a DDS VFO !!!
Re: Stability?

Raj
 


????????I fixed a ICOM735 encoder with LED parts from an old hi-res mouse. The LED inside the encoder was identical to the one in the mouse.

????????I have seen some enterprising chaps make TV's out of old monitors. Throwing away things goes against the grain in India.

73 Raj vu2zap


At 03/02/2005, you wrote:

?
Arv
?
That's right! I remember reading about that too. Works very well apparently. I've never tried it. Neither have I ever tried it with the computer mouse, though I've thought about it several times and got as far as opening some mice up. There are some websites about converting computer mice and stepper motors into shaft encoders. If I have time to dig them up I'll let you know, otherwise, Google should find them.
?
In fact, I have a dismantled one here on my office desk right now. It was on the cupboard next to my desk, along with a keyboard and a big old 19-inch monitor, which I was using for something else for a couple of months. So I called the IT department 5 times to take this rubbish away from here, because I don't like my view being spoiled by looking into the back of an old CRT. Since I got no respone I dismantled the mouse. Next time I saw someone from IT I showed them the inside of the mouse. I told them that next to go was the keyboard. After that, if they still hadn't removed it, the monitor was going to get dismantled. So, in a few days (or weeks) time when my arbitrary time limit has expired and if the IT department still haven't taken it, I might be found harvesting useful components from the monitor for homebrew projects! The wire in the field deflection coils are useful for winding coils from. There must be other useful stuff in there too!
?
73 Hans G0UPL
-----Original Message-----
From: Arv Evans [ mailto:arvevans@...]
Sent: 03 February 2005 17:13
To: BITX
Subject: RE: [BITX20] Stability?
Ron, Raj...

Let me add another comment to Hans' response suggesting the use of optical encoders from dead mice (the computer kind!) to tune a DDS system.? You can also remove stepper motors from disk drives (floppy and/or older hard disk types) and use these to derive up and down stepping pulses for your DDS system.? The head position motors in newer hard disk drives are not suitable because they are not real step motors and do not rotate the full 360 degrees.

Arv K7HKL
_._
On Thu, 2005-02-03 at 08:45, Hans Summers wrote:

Ron, Raj...
?
I have a simple DDS design too, which doesn't need microprocessors: . It would be possible to replace the DIP switches with up/down counters, driven perhaps by an optical shaft encoder. Not an optical encoder you buy very expensively! There are two in every computer mouse, available usually as free scrap. Just a little work required to convert it into a shaft encoder.
?
Personally though I am still nervous about the noise and spurious outputs from DDS generators. I'm Ok with using it in a transmitter but I'd worry about using it in a receiver and degrading performance. Perhaps I'm just paranoid. Mine is currently driving my QRSS beacon which is currently QRV on 10,140,050 MHz with 250mW to an indoor attic dipole.
?
73 Hans G0UPL
-----Original Message-----
From: Raj [ mailto:ggrk@...]
Sent: 03 February 2005 15:04
To: BITX20@...
Subject: Re: [BITX20] Stability?


Ron,

??????? Reminds me of the old days as a youngster building Valve VFO, enclosing it in a box etc.. For PSK: I suggest that you take this requirement to the another extreme and build a DDS VFO !!! Not Joking, its actually the best of both worlds.. Its tough to make a VFO with 10Hz stability.

??????? Try replacing the 56pf next to Q5 with polystyrene.. it should give your major improvement.

??????? No recent experience with digital. I used to run a bbs till some years ago..

73 Raj vu2zap

At 03/02/2005, you wrote:
I really appreciate your quick reply Raj,
No you did not confuse me.
This forum is alive !
Yes I used the ceramic ones for initial trails. I have some polysterene ones (old!! from Philips radios) in my junkbox and will do some trials coming days.
What is your feeling about making the 2 transistor vfo as shown in the original schematics working with a freq. drift of 10Hz or less (this is a tough requirement for digimodes like psk31).
Is there experience with the bitx working with digimodes (rtty, psk31...) as far as you know?
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73 and again tnx fer advice!
Ron


Raj wrote:
Ron,

???????? This is probably because of ceramic capacitors being used the
oscillator stages. Components that determine frequency must be ultra-stabe.
Use NP0 caps, brown ceramics with a black top. You can also use
polystyrene, they are transparent plastic with a silver foil visible
inside. They were only available in the old days in small pF values less
than 5Kpf.

???????? I usually pour bees wax on top of oscillator components to keep
them thermally isolated and keep them from shaking.

???????? Avoid ceramic caps in audio stages, it causes microphonics. Tap
them and you will hear a thump in the speaker/transmission. Use
mylar/polyester.

???????? Do not use mylar/polyester type caps in RF stages for bypass,
instead use ceramic. Polyester work well in audio for coupling.

???????? Ceramic = brown round disks
???????? Polyester/Mylar = green like a chewing gum with leads.

???????? Hope I have not confused you..

73 Raj
vu2zap

>MHz IF will give the proper range) Frequency range seems to be ok but
>stability is bad. After 20 minutes waiting freq shift of 1 KHz still
>exists. I think I will order some components for a HuffAndPuff
>circuit for stabilizing purposes. 

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