Farhan,

The 10 turn pots will give you a "pling pling" tuning effect.
The Blue pots are wire wound. I would suggest a tuning cap and a slow
motion drive. I will be happy to send you one set for your personal Tcvr.

When you are in town, give me a call 2226-5668 / 6787

73 Raj, VU2ZAP

rahul,

do go ahead with the schematics. i have no 'property claims' on the design. i am right now doing a bit of upgrading of the design myself. i ill probably share this with the group as soon as i have made some progress.

this time around, i am make a rig for my personal use. hence, i am expending more effort on this piece as well as slightly higher cost. my main areas of imporvment are the following:

1) high amount of shielding between stages especialy the oscillators and the filters.

2) i am using FET based VFO for lower oscillator phase noise, tuning it with a bank of four 1N4001 diodes with a 10 turn potentiometer for good slow motion drive.

3) digital binary counter for low counter noise (thanks hans! ur site is a treasure).

4) the RF front-end mixer changed to doubly balanced configuration (one more coil to wind).

5) the detector/modulator connections are reversed as discussed previously in the group.

6) reworked the entire audio from detector onwards. the new audio pre-amp is based on w7el design of a common base stage directly coupled to a common emiiter stage. both the stages decoupled by an active decoupler. the audio amp, though not done yet, will be a class-A amplifier with low distortion (instead of the LM386).

7) two IRF510s in push-pull to deliver 10 watts pep (The legal limit for qrp).

8) switching for 7MHz/14Mhz bands, making it a dual-band transceiver.

the low-sensitivity that some have complained about, according to my analysis, is due to the mismatch between the detector and the audio pre-amp.

hence the rework on the audio.

as an aside, are planning to attend the hamconvention in bangalore in october? if you are, we might have an eyeball.

- farhan

---

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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??????? : /KB1GMX/Epiphyte3Mnl.pdf
? Uploaded by : ajparent1
? Description : Epiphite-3 manaul for those interested in similar radios.

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---

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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 : /KB1GMX/Epiphyte3Mnl.pdf
Uploaded by : ajparent1 <kb1gmx@...>
Description : Epiphite-3 manaul for those interested in similar radios.

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开云体育

?

You are right Alison indeed. In one old fujitsu monitor video stages,
I found 3 1,2ghz hitachi wide band transistors 2sc4308, 4pf
capacitance. There is also several wats output video amplifier
transistors 2s3953 by sanyo ft 400mhz 2,7 pf capacitance 8w.
Also driver for them is 2sc2705 by toshiba pct based technology, 1,8pf
ft 200mhz, 0,8w. Comonly used universal transistor in most of the
stages is 2sc458, hitachi, 3,5pf ft around 200 mhz. In my opinion
2sc945 has the most linear characteristics upon current change. So
this is good guideline for salvaged parts. cs9018 and cs9016 from old
disfunct radio receivers of taiwaniese origina are excellent and have
love noise figure.

73 de

Max 4N1ZM

--- In BITX20@..., "ajparent1" <kb1gmx@a...> wrote:

--- In BITX20@..., "Max" <m_orwell@y...> wrote:

I dont agree. PCT process is newer than used for 2n2222. As far

as I

remeber of some article from 1982. This gave lower capacitance

and

noise than usuall transistor technology.

Yes it did yeild both lower noise and better gain. That still does
not make the 2sc1815 a good transistor at more than 1/10th it's Ft
in other than common base circuits. However there were other
transistors developed with that process that were good to much

higher

frequencies.


As to the 1982 process for the 2n2222. That was then. There is
such a thing as the 2n2222A and the process is epitaxial planar
which over time evoled and also produces very good devices good
to GhZ range. The problem is that current (last 10 years)
manufacture devices are likely to be far better than earlier
do to process changes that must be implmented to keep the
manufacturer profitable.

Also most metal can transistors often ehhibit higher capacitances
as a side effect of the much higher power dissapation capability.

However:

The 2n2222 is a 300mhz Ft with a 500mw power dissipation and can
switch 800ma. Noise figure is 4db at audio.

The 2n3904 is a 350mhz Ft with 500mw power dissipation and can
switch 300ma. Noise figure is 5db at audio.

The 2sc1815 is a 80mhz Ft (at 1ma) and increses to 500 at 150ma.
It has a 400mw dissipation and can switch 150ma. Noise is 1DB at
audio with a maximum of 10db. Looking at the curves the device
is also optimized for 6V applications. The gain curves and Ft
curves indicate this device as optimal for amplifiers which use
negative AGC (gain reduction with reduced bias).

While the 2n2222 maybe a rough call due to origins (not all are
good quality) the 2sc1815 is not suitable for the bidirectional
amplifiers without paying close attention to applied bias and
collector load impedence. Myself I'd not use it in a feedback
amplifier those as a oscillator I'd expect excellent results.


Allison

--- In BITX20@..., "Arv Evans K7HKL" <arvevans@e...>
wrote:

Hi

The 2SC1815 is the 2N2222 of transistors in Japan. It is even

more

plentiful and readily available there than the ubiquitous

2N2222 is

in

other countries. While they are usually of quite high quality,

I

suspect

the main reason that Sunamura JF1OZL uses so many of them is

that

they are

plentiful and relatively inexpensive.

Arv
_._

On Thu, 25 Aug 2005 19:06:45 -0600, Max <m_orwell@y...> wrote:

2SC1815

--
Life is too short to be serious. 8-)

Both are a variation of the Vackar osc and transistor choice,
operating point and component quality make a difference. For that
VFO the 2SC1815 is a vastly better device than the 2sc372. I know
as becuase I have a ARS (Allied RadioShack) AX190 (ca1974) reciever
that I replaced all the 2sc372s in oscillators that had proved
drifty. Also a few caps were replaced with polystyrene as well and
the result was far better.

Allison


--- In BITX20@..., BITX20@... wrote:

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 : /BJT VFOs/ft707 gnd base vfo.pdf
Uploaded by : vu3wjm <vu3wjm@y...>
Description : This VFO is on cheaper rig , still beats me why it

works better than one on FT11107

You can access this file at the URL:

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


Regards,

vu3wjm <vu3wjm@y...>

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 : /BJT VFOs/ft707 gnd base vfo.pdf
Uploaded by : vu3wjm <vu3wjm@...>
Description : This VFO is on cheaper rig , still beats me why it works better than one on FT11107

You can access this file at the URL:


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


Regards,

vu3wjm <vu3wjm@...>

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 : /BJT VFOs/ft107 gnd base vfo.pdf
Uploaded by : vu3wjm <vu3wjm@...>
Description : This one is on my old pricy rig

You can access this file at the URL:


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


Regards,

vu3wjm <vu3wjm@...>

--- In BITX20@..., "Max" wrote:
> I dont agree. PCT process is newer than used for 2n2222. As far as I
> remeber of some article from 1982. This gave lower capacitance and
> noise than usuall transistor technology.
>
>?

Yes it did yeild both lower noise and better gain.? That still does
not make the 2sc1815 a good transistor at more than 1/10th it's Ft
in other than common base circuits.? However there were other
transistors developed with that process that were good to much higher
frequencies.


As to the 1982 process for the 2n2222.? That was then.? There is
such a thing as the 2n2222A and the process is epitaxial planar
which over time evoled and also produces very good devices good
to GhZ range.? The problem is that current (last 10 years)
manufacture devices are likely to be far better than earlier
do to process changes that must be implmented to keep the
manufacturer profitable.

Also most metal can? transistors often ehhibit higher capacitances
as a side effect of the much higher power dissapation capability.

However:

The 2n2222 is a 300mhz Ft with a 500mw power dissipation and can
switch 800ma.? Noise figure is 4db at audio.

The 2n3904 is a 350mhz Ft with 500mw power dissipation and can
switch 300ma.? Noise figure is 5db at audio.

The 2sc1815 is a 80mhz Ft (at 1ma) and increses to 500 at 150ma.
It has a 400mw dissipation and can switch 150ma.? Noise is 1DB at
audio with a maximum of 10db. Looking at the curves the device
is also optimized for 6V applications.?? The gain curves and Ft
curves indicate this device as optimal for amplifiers which use
negative AGC (gain reduction with reduced bias).

While the 2n2222 maybe a rough call due to origins (not all are
good quality) the 2sc1815 is not suitable for the bidirectional
amplifiers without paying close attention to applied bias and
collector load impedence. Myself I'd not use it in a feedback
amplifier those as a oscillator I'd expect excellent results.


Allison









>
> --- In BITX20@..., "Arv Evans K7HKL"
> wrote:
> > Hi
> >
> > The 2SC1815 is the 2N2222 of transistors in Japan.? It is even
> more?
> > plentiful and readily available there than the ubiquitous 2N2222 is
> in?
> > other countries.? While they are usually of quite high quality, I
> suspect?
> > the main reason that Sunamura JF1OZL uses so many of them is that
> they are?
> > plentiful and relatively inexpensive.
> >
> > Arv
> > _._

> >
> > On Thu, 25 Aug 2005 19:06:45 -0600, Max wrote:
> >
> > > 2SC1815
> >
> >
> >
> > --
> > Life is too short to be serious.? 8-)

---

To help you stay safe and secure online, we've developed the all new .

I released a "near" final software revision and put it under files
section. I also put a software manual and an updated PLL design.

I put the source code under the GNU public license with the aim to
provide the hobbyst with a piece of software modifiable to facilitate
QRP software control. You can modificate the software but you must
distribute the modified source code.

You can use the software to control any QRP rig. I am working in the
multiband and multimode modifications and yet work in progress... :-(

Comments welcome.
Greetings.
Manuel
EA7ARX

--- In BITX20@..., "Max" <m_orwell@y...> wrote:

I dont agree. PCT process is newer than used for 2n2222. As far as I
remeber of some article from 1982. This gave lower capacitance and
noise than usuall transistor technology.

Yes it did yeild both lower noise and better gain. That still does
not make the 2sc1815 a good transistor at more than 1/10th it's Ft
in other than common base circuits. However there were other
transistors developed with that process that were good to much higher
frequencies.


As to the 1982 process for the 2n2222. That was then. There is
such a thing as the 2n2222A and the process is epitaxial planar
which over time evoled and also produces very good devices good
to GhZ range. The problem is that current (last 10 years)
manufacture devices are likely to be far better than earlier
do to process changes that must be implmented to keep the
manufacturer profitable.

Also most metal can transistors often ehhibit higher capacitances
as a side effect of the much higher power dissapation capability.

However:

The 2n2222 is a 300mhz Ft with a 500mw power dissipation and can
switch 800ma. Noise figure is 4db at audio.

The 2n3904 is a 350mhz Ft with 500mw power dissipation and can
switch 300ma. Noise figure is 5db at audio.

The 2sc1815 is a 80mhz Ft (at 1ma) and increses to 500 at 150ma.
It has a 400mw dissipation and can switch 150ma. Noise is 1DB at
audio with a maximum of 10db. Looking at the curves the device
is also optimized for 6V applications. The gain curves and Ft
curves indicate this device as optimal for amplifiers which use
negative AGC (gain reduction with reduced bias).

While the 2n2222 maybe a rough call due to origins (not all are
good quality) the 2sc1815 is not suitable for the bidirectional
amplifiers without paying close attention to applied bias and
collector load impedence. Myself I'd not use it in a feedback
amplifier those as a oscillator I'd expect excellent results.


Allison

--- In BITX20@..., "Arv Evans K7HKL" <arvevans@e...>
wrote:

Hi

The 2SC1815 is the 2N2222 of transistors in Japan. It is even

more

plentiful and readily available there than the ubiquitous 2N2222 is

in

other countries. While they are usually of quite high quality, I

suspect

the main reason that Sunamura JF1OZL uses so many of them is that

they are

plentiful and relatively inexpensive.

Arv
_._

On Thu, 25 Aug 2005 19:06:45 -0600, Max <m_orwell@y...> wrote:

2SC1815

--
Life is too short to be serious. 8-)

I dont agree. PCT process is newer than used for 2n2222. As far as I
remeber of some article from 1982. This gave lower capacitance and
noise than usuall transistor technology.



--- In BITX20@..., "Arv Evans K7HKL" <arvevans@e...>
wrote:

Hi

The 2SC1815 is the 2N2222 of transistors in Japan. It is even

more

plentiful and readily available there than the ubiquitous 2N2222 is

in

other countries. While they are usually of quite high quality, I

suspect

the main reason that Sunamura JF1OZL uses so many of them is that

they are

plentiful and relatively inexpensive.

Arv
_._

On Thu, 25 Aug 2005 19:06:45 -0600, Max <m_orwell@y...> wrote:

2SC1815

--
Life is too short to be serious. 8-)

Max

I think you did not understand my comment. I was referring to the fact that the 2SC1815 is very readily available in Japan...even more so than the 2N2222 is in the US, and probably the rest of the world. Sunamura san has referred to their being readily available at reasonable prices in some of his writings, and thus the reason for them appearing frequently in his homebrew projects.




Whether they are better or worse than the ubitiquous 2N2222 may be somewhat dependent on the circuitry involved. As Farhan has stated several times, the gain for each stage is fixed by the feedback, not by the particular device being used (assuming it has enough gain at operating frequency to function properly in the BITX design).

In my first BITX I found that my batch of 2N2222s did not have an adequate Ft to work at HF frequencies. That was due to a bad batch of transistors which were supposed to be 2N2222s but did not meet the specifications for that device (they were cheap and unmarked devices from an EBay dealer). Once I changed the RF & IF BJTs to 2N3904s, things worked much better.

Sorry about the confusion, but my original comment was about availability of the 2SC1815s, not about quality or suitability for the task.

Arv K7HKL
_._

--
Life is too short to be serious. 8-)

over years, i have visited kazuhiro's site. his work output continues to amaze me each time. he experiments fearlessly, then documents it all too. quite a volume of work. i find his designs interesting but they take minimalism to an extent where reproducability and performance become difficult to sustain.

my favourite from his site is the no-power AM transmitter which is literally powered by your speech. extreme qrp!

...

the general idea of using transistors with feedback is that the amount of gain extracted is much less than what the transistor is capable of. In such cases as BITX20, there are just two really important parameters to be considered: the Ft should be above 150 Mhz, the noise figure should be less than 6dB at low currents. Using a 1GHz transister will not make a difference as the gain of the stage is pegged at 16dB regardless of the actual Ft or the beta of the transister. It might fall below 16dB if the Ft is any lower, but wont exceed 16dB in anycase.

The inherent stability (and hence the reproducability) of the BITX is due to the fact that transistor types dont matter much, and the negative feedback assures that the individual stages dont self-oscillate.

- farhan

Hello,

Yes 'OZL is a fantastic and very active constructor. Indeed I've
been aware of his projects for many years now. The site for JF1OZL
is one of about 40 I have bookmarked as they represent both active
homebrewed (autoconstructed) and good application of theory.

www.qrp.pops.net is another worth looking along with www.k8iqy.com.

As to the 2SC1815, I do have a good quantity of them and it is a
very good and useful device. It only one of many I chose from
for various projects. I have an unusually good selection of new
devices as I used to provide service in commercial space for a
variety of electronic gear. I also have databooks for most major
makers of transistors as well as a detailed on line data sheet
archive. For BITX I don't think it is as good a choice for the
feedback amplifiers. For tuned amplifiers it is very good.

Most BJT devices can be used in common (grounded) base circuits
as the Alpha cutoff is much higher. I used to take advantage of
this ways back when transistors capable of HF or low VHF were very
hard to get.

Allison
KB1GMX

JF1OZL in most of the constructions even on 50mhz is using this type
of trasistor. As with the increasing of colector current ft getting
higher. Also comon base ft is several times bigger than comon emiter
circuit in the contrarry with comon colector design.

More information about 2sc1815 and implementation of generall purpose
trasistors.




--- In BITX20@..., "ajparent1" <kb1gmx@a...> wrote:

The 2SC1815 is a good device but it's Ft is only 80mhz. For
HF VFOs that is adaquate but for the BITx if it may be a bit
weak. Other devices of the era are the 2sc784, 2sc930 and 2sc945
all good and easily found in salvaged equipment.

As to transistor capacitance in VFOs, it's is easy to bury the
device in configurations that overwhelm the devices capacitance.
By doing so you make the VFO less dependent on the device used and
it can aid stability. The series tuned Colpits VFO used in
orginal BIT-x is such an oscillator. The 500pf across Base to
Emitter is far larger tha the transistors internal capacitance.
The second 500pf capacitor from emitter to ground (collector is
at RF ground due to the .1uf from Collector to ground) swamps any
capacitance from Collector to Emitter.

One trick that I've used for VFOs that helps with stability is
a form of compensation. For most BJT VFOs there is a voltage
where the initial drift is neutral or nearly so. Often this is
easily found by using a LM317 variable voltage regulator and
starting at the design voltage and noting startup drift. Then by
adjustment of the voltage to the VCO it's possible to reduce or
even eliminate that drift. What it achieves is to find a point
where the transistors internal heating due to feedback and junction
heating is minimal or at least stable.

NOTE 1: This is not temperature compensation. There will still
be drift from warming or cooling of other components. The
inductor, capacitors and if used Varactor(Varicap) diodes are
still contributors to thermally drift. The Varactor diode is a
significant source of thermal drift in most VFOs.

NOTE 2: from testing I've found three terminal regulators
provide a more stable voltage than zener diodes due to temerature.


Allison
KB1GMX

--- In BITX20@..., "Max" <m_orwell@y...> wrote:

2sc1815 is toshiba pct process based transistor. so this mean

lower

capacitance and noise figure. this japanese design remind on

comon

base vfo used in the 70's in swan trx. schematics are in file

section.

73 de 4N1ZM

Hi

The 2SC1815 is the 2N2222 of transistors in Japan. It is even more plentiful and readily available there than the ubiquitous 2N2222 is in other countries. While they are usually of quite high quality, I suspect the main reason that Sunamura JF1OZL uses so many of them is that they are plentiful and relatively inexpensive.

Arv
_._

--
Life is too short to be serious. 8-)

The 2SC1815 is a good device but it's Ft is only 80mhz. For
HF VFOs that is adaquate but for the BITx if it may be a bit
weak. Other devices of the era are the 2sc784, 2sc930 and 2sc945
all good and easily found in salvaged equipment.

As to transistor capacitance in VFOs, it's is easy to bury the
device in configurations that overwhelm the devices capacitance.
By doing so you make the VFO less dependent on the device used and
it can aid stability. The series tuned Colpits VFO used in
orginal BIT-x is such an oscillator. The 500pf across Base to
Emitter is far larger tha the transistors internal capacitance.
The second 500pf capacitor from emitter to ground (collector is
at RF ground due to the .1uf from Collector to ground) swamps any
capacitance from Collector to Emitter.

One trick that I've used for VFOs that helps with stability is
a form of compensation. For most BJT VFOs there is a voltage
where the initial drift is neutral or nearly so. Often this is
easily found by using a LM317 variable voltage regulator and
starting at the design voltage and noting startup drift. Then by
adjustment of the voltage to the VCO it's possible to reduce or
even eliminate that drift. What it achieves is to find a point
where the transistors internal heating due to feedback and junction
heating is minimal or at least stable.

NOTE 1: This is not temperature compensation. There will still
be drift from warming or cooling of other components. The
inductor, capacitors and if used Varactor(Varicap) diodes are
still contributors to thermally drift. The Varactor diode is a
significant source of thermal drift in most VFOs.

NOTE 2: from testing I've found three terminal regulators
provide a more stable voltage than zener diodes due to temerature.


Allison
KB1GMX