I have tried this method and it works well with my non-BITX 5w CW
transmitter. My receiver has an RF preamp and a post mixer
amplifier. I found that if I grounded both transistor bases during
transmit with a transistor switch, the transmit signal would be
attenuated enough to be used as sidetone (no audio section mute.) I
think this would work for SSB with lower audio output.

Troy
KC8AFU

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

Those BITX builders who want to have QSK operation without relays

might

want to
look at the web site of Miguel PY2OHH

<>

He shows and explains his simple diode based TR switching method.

This

should
be adaptable to the BITX design.

Arv
_._

--
Expore all the Ideas...Exploit the good ones!

Those BITX builders who want to have QSK operation without relays might want to
look at the web site of Miguel PY2OHH

<>

He shows and explains his simple diode based TR switching method. This should
be adaptable to the BITX design.

Arv
_._

--
Expore all the Ideas...Exploit the good ones!

Troy

H&P stabilisation would hold your frequency to within a Hz or two for
the long term, thus minimizing even a slow drift after warm up. Hans
has come up with several minimalist stabilizer designs (a "One-Chip",
a "two-chip" and a minimalist version of the "Fast Stabilizer").
These circuits may be found on the <HUFFPUFFVFO.yahoogroups.com> forum.
Hans' stabilizer circuits may be made to lock onto 16, 32, or 64 Hz
tuning steps. The one and two chip designs use a 32.768 KHz watch
crystal (salvage one from a cheap watch purchased at the local dollar
store).driving a 74HC4060 binary counter for the timebase.

I have looked before at that receiver and counter on the web page you
suggested. Hans G0UPL's web page also has some minimalist counters that
could be adapted to your L.O. output, as does Onno PA2OHH
<www.qsl.net/pa2ohh/sfreq.htm> and Miguel PY2OHH
<>.

Arv
_._

--
Expore all the Ideas...Exploit the good ones!

Thanks Arv,

I've had the AFU callsign for about ten years and you're the first
person to comment on it. I thought it was funny when it was first
assigned to me but nobody seemed to share my sense of humor. Thanks
for noticing!

Thanks for the huff&puff invite. I've also been looknig at Hans
Summers website and I'm thinking about trying it out. My current CW
rcvr is the popcorn rcvr from the qrp homebuilder homepage. It has
an LO freq of approx 2.5 MHz (4.433 MHz IF)and is pretty stable ( I
think I remember about 2Hz per minute after warm-up but it's been a
while since I measured it so I could be wrong) but I am intrigued by
the H&P. Lately I have been finishing up a presettable frequency
counter that I can run directly off of my VFO. Now I know where I am
on the band. It can be found at:



It's at the bottom of the homepage.
Thanks for the invite and I will start checking out the H&P group.

73's & HPE CUL.

Troy
KC8AFU
--- In BITX20@..., "Arv Evans" <arvevans@e...> wrote:

Troy

The BITX has also been used for CW. Several builders have added

a

center-of-the-filter
BFO oscillator that serves both send and receive CW functions. I

took the

simple way and
just added a keyed AF oscillator that plugs into the mike jack.

Love the callsign. I'll bet you get a few comments about it

though!

I did not see your name in the members list for the Huff and Puff

group so

I will go
over there and send you an invite. The Huff & Puff VFO group

forum is a

logical
extension to the BITX because using an H & P circuit to stabilize

your

BITX oscillator
makes it into a very stable but still inexpensive rig that is

capable of

working with
narrow filters for CW and PSK/MSK contacts.

Arv K7HKL

Now you have the benefit to read for example every day ten (for you
new) postings!
Often it is better to follow also what happened before, preventing
that the same questions are asked more often.
Hear you on the band ;-)
Chris, PA3CRX

Troy

The BITX has also been used for CW. Several builders have added a center-of-the-filter
BFO oscillator that serves both send and receive CW functions. I took the simple way and
just added a keyed AF oscillator that plugs into the mike jack.

Love the callsign. I'll bet you get a few comments about it though!

I did not see your name in the members list for the Huff and Puff group so I will go
over there and send you an invite. The Huff & Puff VFO group forum is a logical
extension to the BITX because using an H & P circuit to stabilize your BITX oscillator
makes it into a very stable but still inexpensive rig that is capable of working with
narrow filters for CW and PSK/MSK contacts.

Arv K7HKL

--
Expore all the Ideas...Exploit the good ones!

Hello all,

I just wanted to say what a fine group I think this is. I have not
built a BITX (I do mostly CW homebrew projects) but most of the topics
here have been pertinet to my homebrewing. My only regret is that I
didn't join when the group was started (I've only been tuning in for
the last two months). This group gets my approval as the best
homebrewing group on the web. Keep up the good work guys!

Troy Hunt
KC8AFU.

Hi Ron,

QRPPPP = 5mW in my book! Every additional "P"= 1/10 power level..

I worked USA and a lot of EU with 1mW + small beam.. so you are running QRO!!!

Good Dx with Bitx

73 Raj VU2ZAP

with an adjustable matching network (pi-filter). No reply/qso yet
>(but the band was very dead after 10'o-clock in the evening in
>Holland and 2 Watt is QRPPPP).

---

Do you Yahoo!?
Yahoo! Sports - for Fantasy Baseball.

Hi Ron,

QRPPPP = 5mW in my book! Every additional "P"= 1/10 power level..

I worked USA and a lot of EU with 1mW + small beam.. so you are running QRO!!!

Good Dx with Bitx

73 Raj VU2ZAP

with an adjustable matching network (pi-filter). No reply/qso yet

Dear BITX homebrew-heroes!,

I combined the ideas of Ruud and Alf and, to my surprise, the IRF510
is not self-oscillating anymore (at all DC bias settings) !!
I did following (20 min work):
Added 3 decoupling C's and 2 rf chokes to pa and driver circuitry and
added a ferrite bead (from an old videoplayer) over the gate of the
MOSFET. Also added a cap of 68 pF between drain of mosfet and gnd.
I think the 10 cents ferrite did most of the job.
RF power is still too low (appr. 2 Watts RF), so there is still
something to do. Driver circuit needs an additional RF transisitor I
guess. I found a nice 2SC1384 from an old CB-transceiver.
Furthermore I can gain by further shielding the PA driver and improve
the trifilair mosfet coil (I have one made, but it's behaviour seems
to be similar when compared to the bifilair coil).
Did some RTTY transmissions with 2 Watt yesterday though and the
BITX17 sounds beautifully. Good USB, no remainders of carrierwave
noticeable. I used a full lambda one-fed wire antenna (in the garden)
with an adjustable matching network (pi-filter). No reply/qso yet
(but the band was very dead after 10'o-clock in the evening in
Holland and 2 Watt is QRPPPP).

73 and lots of homebrew fun
Ron
PA2RF




--- In BITX20@..., "alf" <fpdbase@e...> wrote:

Hi to all homebrew BITX20 members,
Hope everybody is having fun building their version of the

BITX radio.

After attending local hamfest at the end of February, collecting

all the relevant parts, started assembly of BITX20. The chassis, L
shape was salvaged from the power supply of a old Fax machine and
it's circuit board was used a source of some of the parts for the
BITX20. Lot's of good parts in old equipment hi hi. A piece of single
sided pcb was fitted to the chassis, copper side up, and ye old ugly
style construction began. The VFO was built first and a compartment
of double sided PCB surrounds it. A red LED is used to fine tune the
frequency and gives about 4khz range. Various coils were tried at L4
to improve frequency stability, ended up using a ferrite bobbin from
the salvaged Fax board. The Receiver front end was built next,
opposite side of VFO partition. T1 mixer transformer is mounted on
the crystal filter side (IF) via a feedthru capacitor. The IF, BFO
and audio stages assembled and tested next. Used 2N2222A
transistors throughout except for the PA amplifier of course, the
audio output device is a TDA2002. The PA amp was built on a small
heat sink salvaged from a old TV chassis, size 8 X 4.5 cm . The
2N2218 driver coupled to IRF510 using TV balun taken from TV tuner,
and some instability occurred when driving a reactive load. This was
cured by fitting a ferrite bead directly onto the gate leg of IRF510
Fet. The receiver audio is very clear and sensitivity better than 0.5
uV. Don't procrastinate, if your thinking it's all too much trouble,
just have a go, you will learn more by doing.

Many Thanks to Asher for allowing me too much fun..

Best regards to all BITX members

Alf VK2YAC

开云体育

Hi Farhan,

You can see in the schema's in the Files box under PE2BS or in the
Photos box how I used the trifilair transformers. The first trifilair
transformer (13 wdg on an T37-43 lookalike) is the output of the
driverstage and is placed on its "print". The last trifilair
transformer is made of 14 wdg trifilair on an T50-6. Like I wrote to
Ron it is difficult to say what exactly solved the problem but I got
rid of all the oscilations after the shielding AND the trifilair
transformers.

73

Ruud.
PE2BS

--- In BITX20@..., "ashhar_farhan" <farhan@p...> wrote:

hi all,

looks like the instability problem has something to do with the

phase

of the input to the IRF510 too.
can those who have tried the trifilar windings also suggest the

phase

used in the transformer?

- farhan

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

Hi Ron,

I just read your message. There is something in the message I
recognize: 'Found that the IRF510 has a tendency to start

oscillating

when set at a higher bias-level.' I had that problem too. In mine
BITX-PSK it was not enough to lower the bias-level. The PA seems

to

work OK when I was tuning from the computer and there was no

output

when there was no modulation. Unfortunately the PA worked in

class C.

The whole problem turned out to be an instability in the
driver==>PA==>antenna system. I solved it the way I discribed in
my message a few weeks ago:
First I biased the IRF 510: with no modulation and carrier nulled

by

the trimpot of the balanced modulator, the Id should be about 80

mA.

(from: "A simple SSB tranceiver" by Ashar Farhan

www.antentop.bel.ru/)

Second: a lot of decoupling.
Third: shielding the driver stage (see picture in the picture box
PE2BS)
Fourth: change the impedance matching between driverstage and PA

and

between the PA and the pi filter. Make it trifilair instead of
bifilair (see the remarks of Chris in the filebox Modifications).

The

result is also more watts RF.

Now the rig is working OK. When there is no modulation, there is

no

output in the SWR meter and a little on the spectrumanalyzer.

Even

with mismatching the system to the antenna the PA does not

generate.

It is the first HF-QRP rig I build and the results are amazing.

In CW

(Hamscope and CWget on the computer) and only 5 watt I worked

UA3,

YO, ER, HA!

Succes and like to hear from you.

73

Ruud
PE2BS

--- In BITX20@..., Ron Brink <pa2rf@y...> wrote:

Thanks for reply Chris,
Ja in de Zoetermeerse polder waren (kei) harde signalen in de

17 m

band te horen!

I think your 6 Watts RF should be fine for digimode use. Or am

i

wrong?

I hope to experience this myself on short notice. Yesterday did

first trials with the IRF510 endstage. I had 4 Watts RF out with

a

RTTY test signal connected. Hope to increase output level with a

few

Watts (increase supply voltage and adjust pi-filter) and do some

real

trials (hopefully 2-way comms) this weekend. Found that the

IRF510

has a tendency to start oscillating when set at a higher bias-

level.

Should fix that too. Also found that my (bureau) desk-light when

30

cm above the VFO gets this VFO change frequency; but when Huff

and

Puff circuit is connected, VFO frequency is corrected in a quick

and

fine way..

My appreciation for the BITX is growing ...
Bye
Ron 73
PA2RF

vdberghak <vdberghak@z...> wrote:

Hi,
responding to the messages below:
- Ron, in the Netherlands, I heard also several stations with

very

strong signals, form Russia but also from the States.
However, the 6 watt I have on 17 mtr is a bit little in

combination

with my sloping dipole. Stations in (for example) Bulgaria are
answering: 'only outside Europe'....
- Rahul, I use a small 8 Ohm speaker (removed from an old

transistor

radio). When I connect the antenna, a loud noise is comming out

of

the speaker. When I receive a weak station, it is just above

the

noise but at the moment a strong station enters, I really have

to

turn down the volume potmeter immidiatly!
In fact, the volume is never on its maximum.
By the way, I use the real, original BC107, metal can ;-) For

the

stage before the LM386 I use a BC109.
Best regards,
Chris.

Interesting are you using a speaker or heaphone. Secondly

what

transistors are you usingBC547s or 2n3904s

73
Rahul VU3WJM

Bye the way, RX signals on 17m were fine this afternoon,

heard

ssb

voice, rtty, psk31 and cw. With a one-lambda (17 m) long-wire

antenna

connected. Some signals clear enough to decode...
Does anybody have experience with one wave-length antennas

(up

till

now I have only used half or quarter lambda ant's..)

Bye bye and have a good Easter weekend (for what's left)
Ron
PA2RF

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The imput impedance of the IRF510 is very low. Therefore I made the
coil trifilar resulting in a lower impedance then originally. This
gives more output but seems also give a better stability?
I remember I have a low iddle current, (30 mA?) to have it stable.
Higher iddle current brought not much benefits, the output increased
slightly but not worth the additional heat up. Modulation is fine,
several SSB contacts made with good result.
Good luck, Chris.

hi all,

looks like the instability problem has something to do with the

phase

of the input to the IRF510 too.
can those who have tried the trifilar windings also suggest the

phase

used in the transformer?

- farhan

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

Hi Ron,

I just read your message. There is something in the message I
recognize: 'Found that the IRF510 has a tendency to start

oscillating

when set at a higher bias-level.' I had that problem too. In

mine

BITX-PSK it was not enough to lower the bias-level.

what kind of chokes did you use?

73s
- de farhan

--- In BITX20@..., Ron Brink <pa2rf@y...> wrote:

Thanks Ruud,
Congratulations with your CW QSOs. A fantastic achievement!
I will keep your hints and tips in mind when I continue to

experiment this weekend.

I will start shielding the driver and make the trifilair coil.
You mentioned 'decoupling' ; did you do this by adding RF chokes?

Where exactly?

Bye
Ron
pa2rf


Ruud Jongeling <pe2bs@t...> wrote:

Hi Ron,

I just read your message. There is something in the message I
recognize: 'Found that the IRF510 has a tendency to start oscillating
when set at a higher bias-level.' I had that problem too. In mine
BITX-PSK it was not enough to lower the bias-level. The PA seems to
work OK when I was tuning from the computer and there was no output
when there was no modulation. Unfortunately the PA worked in class C.
The whole problem turned out to be an instability in the
driver==>PA==>antenna system. I solved it the way I discribed in
my message a few weeks ago:
First I biased the IRF 510: with no modulation and carrier nulled by
the trimpot of the balanced modulator, the Id should be about 80 mA.
(from: "A simple SSB tranceiver" by Ashar Farhan www.antentop.bel.ru/)
Second: a lot of decoupling.
Third: shielding the driver stage (see picture in the picture box
PE2BS)
Fourth: change the impedance matching between driverstage and PA and
between the PA and the pi filter. Make it trifilair instead of
bifilair (see the remarks of Chris in the filebox Modifications). The
result is also more watts RF.

Now the rig is working OK. When there is no modulation, there is no
output in the SWR meter and a little on the spectrumanalyzer. Even
with mismatching the system to the antenna the PA does not generate.

It is the first HF-QRP rig I build and the results are amazing. In CW
(Hamscope and CWget on the computer) and only 5 watt I worked UA3,
YO, ER, HA!

Succes and like to hear from you.

73

Ruud
PE2BS

--- In BITX20@..., Ron Brink <pa2rf@y...> wrote:

Thanks for reply Chris,
Ja in de Zoetermeerse polder waren (kei) harde signalen in de 17 m

band te horen!

I think your 6 Watts RF should be fine for digimode use. Or am i

wrong?

I hope to experience this myself on short notice. Yesterday did

first trials with the IRF510 endstage. I had 4 Watts RF out with a
RTTY test signal connected. Hope to increase output level with a few
Watts (increase supply voltage and adjust pi-filter) and do some real
trials (hopefully 2-way comms) this weekend. Found that the IRF510
has a tendency to start oscillating when set at a higher bias-level.
Should fix that too. Also found that my (bureau) desk-light when 30
cm above the VFO gets this VFO change frequency; but when Huff and
Puff circuit is connected, VFO frequency is corrected in a quick and
fine way..

My appreciation for the BITX is growing ...
Bye
Ron 73
PA2RF

vdberghak <vdberghak@z...> wrote:

Hi,
responding to the messages below:
- Ron, in the Netherlands, I heard also several stations with very
strong signals, form Russia but also from the States.
However, the 6 watt I have on 17 mtr is a bit little in combination
with my sloping dipole. Stations in (for example) Bulgaria are
answering: 'only outside Europe'....
- Rahul, I use a small 8 Ohm speaker (removed from an old

transistor

radio). When I connect the antenna, a loud noise is comming out of
the speaker. When I receive a weak station, it is just above the
noise but at the moment a strong station enters, I really have to
turn down the volume potmeter immidiatly!
In fact, the volume is never on its maximum.
By the way, I use the real, original BC107, metal can ;-) For the
stage before the LM386 I use a BC109.
Best regards,
Chris.

Interesting are you using a speaker or heaphone. Secondly what

transistors are you usingBC547s or 2n3904s

73
Rahul VU3WJM

Bye the way, RX signals on 17m were fine this afternoon, heard

ssb

voice, rtty, psk31 and cw. With a one-lambda (17 m) long-wire

antenna

connected. Some signals clear enough to decode...
Does anybody have experience with one wave-length antennas (up

till

now I have only used half or quarter lambda ant's..)

Bye bye and have a good Easter weekend (for what's left)
Ron
PA2RF

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To visit your group on the web, go to:


To unsubscribe from this group, send an email to:
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---------------------------------
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---------------------------------
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hi all,

looks like the instability problem has something to do with the phase
of the input to the IRF510 too.
can those who have tried the trifilar windings also suggest the phase
used in the transformer?

- farhan

Hi Ron,

The decoupling was made by C's of varouis values (100 n, 22n, 47 u and 100
uf) in Vcc lines, the biassystem for the IF510, the relais for the PA, etc.
See the schema in the file box (PE2BS schema's). In the Vcc I did addd RF
chokes of 22 uH. It is difficult to say what solved the problem. The shielding
and the better impedance matching were the most effectiv but I did this after
decoupling.

73

Ruud

-- Oorspronkelijk bericht --
To: BITX20@...
From: Ron Brink <pa2rf@...>
Date: Wed, 30 Mar 2005 22:17:15 -0800 (PST)
Subject: Re: [BITX20] Re: Small mistake
Reply-To: BITX20@...


Thanks Ruud,
Congratulations with your CW QSOs. A fantastic achievement!
I will keep your hints and tips in mind when I continue to experiment this
weekend.
I will start shielding the driver and make the trifilair coil.
You mentioned 'decoupling' ; did you do this by adding RF chokes? Where

exactly?

Bye
Ron
pa2rf


Ruud Jongeling <pe2bs@...> wrote:

Hi Ron,

I just read your message. There is something in the message I
recognize: 'Found that the IRF510 has a tendency to start oscillating
when set at a higher bias-level.' I had that problem too. In mine
BITX-PSK it was not enough to lower the bias-level. The PA seems to
work OK when I was tuning from the computer and there was no output
when there was no modulation. Unfortunately the PA worked in class C.
The whole problem turned out to be an instability in the
driver==>PA==>antenna system. I solved it the way I discribed in
my message a few weeks ago:
First I biased the IRF 510: with no modulation and carrier nulled by
the trimpot of the balanced modulator, the Id should be about 80 mA.
(from: "A simple SSB tranceiver" by Ashar Farhan www.antentop.bel.ru/)
Second: a lot of decoupling.
Third: shielding the driver stage (see picture in the picture box
PE2BS)
Fourth: change the impedance matching between driverstage and PA and
between the PA and the pi filter. Make it trifilair instead of
bifilair (see the remarks of Chris in the filebox Modifications). The
result is also more watts RF.

Now the rig is working OK. When there is no modulation, there is no
output in the SWR meter and a little on the spectrumanalyzer. Even
with mismatching the system to the antenna the PA does not generate.

It is the first HF-QRP rig I build and the results are amazing. In CW
(Hamscope and CWget on the computer) and only 5 watt I worked UA3,
YO, ER, HA!

Succes and like to hear from you.

73

Ruud
PE2BS

--- In BITX20@..., Ron Brink <pa2rf@y...> wrote:

Thanks for reply Chris,
Ja in de Zoetermeerse polder waren (kei) harde signalen in de 17 m

band te horen!

I think your 6 Watts RF should be fine for digimode use. Or am i

wrong?

I hope to experience this myself on short notice. Yesterday did

first trials with the IRF510 endstage. I had 4 Watts RF out with a
RTTY test signal connected. Hope to increase output level with a few
Watts (increase supply voltage and adjust pi-filter) and do some real
trials (hopefully 2-way comms) this weekend. Found that the IRF510
has a tendency to start oscillating when set at a higher bias-level.
Should fix that too. Also found that my (bureau) desk-light when 30
cm above the VFO gets this VFO change frequency; but when Huff and
Puff circuit is connected, VFO frequency is corrected in a quick and
fine way..

My appreciation for the BITX is growing ...
Bye
Ron 73
PA2RF

vdberghak <vdberghak@z...> wrote:

Hi,
responding to the messages below:
- Ron, in the Netherlands, I heard also several stations with very
strong signals, form Russia but also from the States.
However, the 6 watt I have on 17 mtr is a bit little in combination
with my sloping dipole. Stations in (for example) Bulgaria are
answering: 'only outside Europe'....
- Rahul, I use a small 8 Ohm speaker (removed from an old

transistor

radio). When I connect the antenna, a loud noise is comming out of
the speaker. When I receive a weak station, it is just above the
noise but at the moment a strong station enters, I really have to
turn down the volume potmeter immidiatly!
In fact, the volume is never on its maximum.
By the way, I use the real, original BC107, metal can ;-) For the
stage before the LM386 I use a BC109.
Best regards,
Chris.

Interesting are you using a speaker or heaphone. Secondly what

transistors are you usingBC547s or 2n3904s

73
Rahul VU3WJM

Bye the way, RX signals on 17m were fine this afternoon, heard

ssb

voice, rtty, psk31 and cw. With a one-lambda (17 m) long-wire

antenna

connected. Some signals clear enough to decode...
Does anybody have experience with one wave-length antennas (up

till

now I have only used half or quarter lambda ant's..)

Bye bye and have a good Easter weekend (for what's left)
Ron
PA2RF

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---------------------------------
Yahoo! Groups Links

To visit your group on the web, go to:


To unsubscribe from this group, send an email to:
BITX20-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of

Service.

__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around

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---------------------------------
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To visit your group on the web, go to:


To unsubscribe from this group, send an email to:
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_____________________________________________________________________

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een domeinnaam bij Tiscali. Ga naar

Hi Ron,

I just read your message. There is something in the message I
recognize: 'Found that the IRF510 has a tendency to start oscillating
when set at a higher bias-level.' I had that problem too. In mine
BITX-PSK it was not enough to lower the bias-level. The PA seems to
work OK when I was tuning from the computer and there was no output
when there was no modulation. Unfortunately the PA worked in class C.
The whole problem turned out to be an instability in the
driver==>PA==>antenna system. I solved it the way I discribed in
my message a few weeks ago:
First I biased the IRF 510: with no modulation and carrier nulled by
the trimpot of the balanced modulator, the Id should be about 80 mA.?
(from: "A simple SSB tranceiver" by Ashar Farhan www.antentop.bel.ru/)
Second: a lot of decoupling.
Third: shielding the driver stage (see picture in the picture box
PE2BS)
Fourth: change the impedance matching between driverstage and PA and
between the PA and the pi filter. Make it trifilair instead of
bifilair (see the remarks of Chris in the filebox Modifications). The
result is also more watts RF.

Now the rig is working OK. When there is no modulation, there is no
output in the SWR meter and a little on the spectrumanalyzer. Even
with mismatching the system to the antenna the PA does not generate.

It is the first HF-QRP rig I build and the results are amazing. In CW
(Hamscope and CWget on the computer) and only 5 watt I worked UA3,
YO, ER, HA!

Succes and like to hear from you.

73

Ruud
PE2BS

--- In BITX20@..., Ron Brink wrote:
> Thanks for reply Chris,
> Ja in de Zoetermeerse polder waren (kei) harde signalen in de 17 m
band te horen!
> I think your 6 Watts RF should be fine for digimode use. Or am i
wrong?
> I hope to experience this myself on short notice. Yesterday did
first trials with the IRF510 endstage. I had 4 Watts RF out with a
RTTY test signal connected. Hope to increase output level with a few
Watts (increase supply voltage and adjust pi-filter) and do some real
trials (hopefully 2-way comms) this weekend. Found that the IRF510
has a tendency to start oscillating when set at a higher bias-level.
Should fix that too. Also found that my (bureau) desk-light when 30
cm above the VFO gets this VFO change frequency; but when Huff and
Puff circuit is connected, VFO frequency is corrected in a quick and
fine way..
> My appreciation for the BITX is growing ...
> Bye
> Ron 73
> PA2RF
>
> vdberghak wrote:
>
> Hi,
> responding to the messages below:
> - Ron, in the Netherlands, I heard also several stations with very
> strong signals, form Russia but also from the States.
> However, the 6 watt I have on 17 mtr is a bit little in combination
> with my sloping dipole. Stations in (for example) Bulgaria are
> answering: 'only outside Europe'....
> - Rahul, I use a small 8 Ohm speaker (removed from an old
transistor
> radio). When I connect the antenna, a loud noise is comming out of
> the speaker. When I receive a weak station, it is just above the
> noise but at the moment a strong station enters, I really have to
> turn down the volume potmeter immidiatly!
> In fact, the volume is never on its maximum.
> By the way, I use the real, original BC107, metal can ;-) For the
> stage before the LM386 I use a BC109.
> Best regards,
> Chris.
>
> > Interesting are you using a speaker or heaphone. Secondly what
> transistors are you usingBC547s or 2n3904s
> > 73
> > Rahul VU3WJM
> >?
> > Bye the way, RX signals on 17m were fine this afternoon, heard
ssb
> > voice, rtty, psk31 and cw. With a one-lambda (17 m) long-wire
> antenna
> > connected. Some signals clear enough to decode...
> > Does anybody have experience with one wave-length antennas (up
> till
> > now I have only used half or quarter lambda ant's..)
> >
> > Bye bye and have a good Easter weekend (for what's left)
> > Ron
> > PA2RF
>
>
>
>
>
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>
>
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---

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Hi Ron,

I just read your message. There is something in the message I
recognize: 'Found that the IRF510 has a tendency to start oscillating
when set at a higher bias-level.' I had that problem too. In mine
BITX-PSK it was not enough to lower the bias-level. The PA seems to
work OK when I was tuning from the computer and there was no output
when there was no modulation. Unfortunately the PA worked in class C.
The whole problem turned out to be an instability in the
driver==>PA==>antenna system. I solved it the way I discribed in
my message a few weeks ago:
First I biased the IRF 510: with no modulation and carrier nulled by
the trimpot of the balanced modulator, the Id should be about 80 mA.
(from: "A simple SSB tranceiver" by Ashar Farhan www.antentop.bel.ru/)
Second: a lot of decoupling.
Third: shielding the driver stage (see picture in the picture box
PE2BS)
Fourth: change the impedance matching between driverstage and PA and
between the PA and the pi filter. Make it trifilair instead of
bifilair (see the remarks of Chris in the filebox Modifications). The
result is also more watts RF.

Now the rig is working OK. When there is no modulation, there is no
output in the SWR meter and a little on the spectrumanalyzer. Even
with mismatching the system to the antenna the PA does not generate.

It is the first HF-QRP rig I build and the results are amazing. In CW
(Hamscope and CWget on the computer) and only 5 watt I worked UA3,
YO, ER, HA!

Succes and like to hear from you.

73

Ruud
PE2BS

--- In BITX20@..., Ron Brink <pa2rf@y...> wrote:

Thanks for reply Chris,
Ja in de Zoetermeerse polder waren (kei) harde signalen in de 17 m

band te horen!

I think your 6 Watts RF should be fine for digimode use. Or am i

wrong?

I hope to experience this myself on short notice. Yesterday did

first trials with the IRF510 endstage. I had 4 Watts RF out with a
RTTY test signal connected. Hope to increase output level with a few
Watts (increase supply voltage and adjust pi-filter) and do some real
trials (hopefully 2-way comms) this weekend. Found that the IRF510
has a tendency to start oscillating when set at a higher bias-level.
Should fix that too. Also found that my (bureau) desk-light when 30
cm above the VFO gets this VFO change frequency; but when Huff and
Puff circuit is connected, VFO frequency is corrected in a quick and
fine way..

My appreciation for the BITX is growing ...
Bye
Ron 73
PA2RF

vdberghak <vdberghak@z...> wrote:

Hi,
responding to the messages below:
- Ron, in the Netherlands, I heard also several stations with very
strong signals, form Russia but also from the States.
However, the 6 watt I have on 17 mtr is a bit little in combination
with my sloping dipole. Stations in (for example) Bulgaria are
answering: 'only outside Europe'....
- Rahul, I use a small 8 Ohm speaker (removed from an old

transistor

radio). When I connect the antenna, a loud noise is comming out of
the speaker. When I receive a weak station, it is just above the
noise but at the moment a strong station enters, I really have to
turn down the volume potmeter immidiatly!
In fact, the volume is never on its maximum.
By the way, I use the real, original BC107, metal can ;-) For the
stage before the LM386 I use a BC109.
Best regards,
Chris.

Interesting are you using a speaker or heaphone. Secondly what

transistors are you usingBC547s or 2n3904s

73
Rahul VU3WJM

Bye the way, RX signals on 17m were fine this afternoon, heard

ssb

voice, rtty, psk31 and cw. With a one-lambda (17 m) long-wire

antenna

connected. Some signals clear enough to decode...
Does anybody have experience with one wave-length antennas (up

till

now I have only used half or quarter lambda ant's..)

Bye bye and have a good Easter weekend (for what's left)
Ron
PA2RF

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Hello BITXers

I finish,last weekend, my BITX40 it works very fine...
I use beads for all trifilar coils, 10 turns 0.15mm diameter wire
twisted.
The VFO is a HiperVXO running with 3 parallel xtals of 3020kHz,
covering from 3010 to 2700kHZ (300kHz), the inductor series with xtal
and varible capacitor (2x140pF parallel) is a 10mm red head OM
oscillator. Look in my homepage at



The ladder filter are made with "CQ" Brand xtals and the values are
For CW a build a second BFO connected with a attenutor to the input
of the IF amplifier (just after the ladder filter) it is opereted
directly with the key (ground keying), I dont use a switch to change
from CW to DSB I disconnect the mike...
I put another switch to change from USB (trimmer to grond) to LSB
(inductor commercial 4.7?H series with a trimmer 4.6 -50pF yellow).
I will plan to make it a multi band ... then I make the 7MHZ filter
outside and this filter are build with 3 x 4.7?H commercial inductors
(looks like a 1/4W resistor) ....
The PA I will change to a bipolar 2SC1173 and it devellops about 9W
output... I build also a RF pre-amplifier thinking in others bands.
The LPF are also build in another box...
I made few QSOs CW and SSB with good reports,
I will make some pictures and discription ....

73 from Brasil

PY2OHH Miguel

Hi,
responding to the messages below:
- Ron, in the Netherlands, I heard also several stations with very
strong signals, form Russia but also from the States.
However, the 6 watt I have on 17 mtr is a bit little in combination
with my sloping dipole. Stations in (for example) Bulgaria are
answering: 'only outside Europe'....
- Rahul, I use a small 8 Ohm speaker (removed from an old transistor
radio). When I connect the antenna, a loud noise is comming out of
the speaker. When I receive a weak station, it is just above the
noise but at the moment a strong station enters, I really have to
turn down the volume potmeter immidiatly!
In fact, the volume is never on its maximum.
By the way, I use the real, original BC107, metal can ;-) For the
stage before the LM386 I use a BC109.
Best regards,
Chris.

> Interesting are you using a speaker or heaphone. Secondly what
transistors are you usingBC547s or 2n3904s
> 73
> Rahul VU3WJM
>?
> Bye the way, RX signals on 17m were fine this afternoon, heard ssb
> voice, rtty, psk31 and cw. With a one-lambda (17 m) long-wire
antenna
> connected. Some signals clear enough to decode...
> Does anybody have experience with one wave-length antennas (up
till
> now I have only used half or quarter lambda ant's..)
>
> Bye bye and have a good Easter weekend (for what's left)
> Ron
> PA2RF

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