Date   
Papercrafts for project box (BITX20A)

qrpjl1kra
 

Hi all,

To integrate BITX20A into project box,
Two papercrafts are posted in photo area

Dial scale:
http://ph.groups.yahoo.com/group/BITX20/photos/view/a24d?b=14

I attached this scale to 1mm thcikness round board and output
axis of reduction drive. You can use this as fixed scale.

PA finals aligment note:
http://ph.groups.yahoo.com/group/BITX20/photos/view/a24d?b=15

A few month after making kit. I often forget this kind of
important procedure. Save your IRF510s.

Please use if you like it.

Junichi JL1KRA

small reduction drive on eBay.

ah6gi
 

There are three of these things, here's one listing

<http://cgi.ebay.com/VINTAGE-NATIONAL-VELVET-PANEL-MOUNT-VERNIER-DIAL-USED_W0QQitemZ160235926844QQihZ006QQcategoryZ1502QQssPageNameZWDVWQQrdZ1QQcmdZViewItem>


de ah6gi/4 no relation to or knowledge of the seller.

New file uploaded to BITX20

BITX20@...
 

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 : /Antennas/THE MINIMALIST BACKPACK TM ANTENNA SYSTEM.txt
Uploaded by : m_orwell <m_orwell@...>
Description : Link to simple wire constructions

You can access this file at the URL:
http://groups.yahoo.com/group/BITX20/files/Antennas/THE%20MINIMALIST%20BACKPACK%20TM%20ANTENNA%20SYSTEM.txt

To learn more about file sharing for your group, please visit:
http://help.yahoo.com/l/us/yahoo/groups/original/members/web/index.htmlfiles

Regards,

m_orwell <m_orwell@...>

Re: board sucessful

wbdmxbaileybobbuttercup
 

thanks, but been there, I have some 30 gauge wire and 20 turns does fit on the dumbbell form, wonder it that will work,

I was wanting to know of a source for a wire that size.


To: BITX20@...: arvid.evans@...: Tue, 29 Apr 2008 13:33:20 -0600Subject: Re: [BITX20] Re: board sucessful




WB7DMXGo here <http://www.powerwerx.com/wiregauge.asp> to see conversion table for SWG to AWG.Arvwb7dmx wrote:>> --- In BITX20@... <mailto:BITX20%40yahoogroups.com>, > "wb7dmx" <wb7dmx@...> wrote:> >> > well I finely got the bitx20 ver 3 board made, now to drill a lot of> > small holes.> >>> holes all drilled and now to start building.>> I just hit a snag, where in the world do I get sgw 45 wire to wind L 5.>> also do I leave the built-in capicators inside the if transformers or> remove them ?>> -- ======================================Web: http://K7HKL.homelinux.nethttp://bitx20a.livejournal.comhttp://home.earthlink.net/~arvevans/http://www.geocities.com/k7hkl_arv/======================================[Non-text portions of this message have been removed]






_________________________________________________________________
Make i'm yours.  Create a custom banner to support your cause.
http://im.live.com/Messenger/IM/Contribute/Default.aspx?source=TXT_TAGHM_MSN_Make_IM_Yours

[Non-text portions of this message have been removed]

Re: board sucessful

Arv Evans
 

WB7DMX

Go here <http://www.powerwerx.com/wiregauge.asp> to see conversion table
for SWG to AWG.

Arv

wb7dmx wrote:


--- In BITX20@... <mailto:BITX20%40yahoogroups.com>,
"wb7dmx" <wb7dmx@...> wrote:

well I finely got the bitx20 ver 3 board made, now to drill a lot of
small holes.
holes all drilled and now to start building.

I just hit a snag, where in the world do I get sgw 45 wire to wind L 5.

also do I leave the built-in capicators inside the if transformers or
remove them ?

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

Re: board sucessful

wbdmxbaileybobbuttercup
 

--- In BITX20@..., "wb7dmx" <wb7dmx@...> wrote:

well I finely got the bitx20 ver 3 board made, now to drill a lot of
small holes.
holes all drilled and now to start building.

I just hit a snag, where in the world do I get sgw 45 wire to wind L 5.

also do I leave the built-in capicators inside the if transformers or
remove them ?

BITX20A in severe contest operation (Q24 failure)

qrpjl1kra
 

Hi all,

I used BITX20A in All-JA contest.
The contest is known as most dense in spectrum
and big KW staions QRV in populated area.
As my suprize, BITX20A is not overloaded at all
in this QRM receiving. Without AGC I had no plobem.
Bipolar 2N3904 frontend and low gain in RF is
the success of BITX20.

On the other hand I experienced TX trouble.
In latter half of contest, suddenly I had
no power at all. I could not increase bias current
of MOS-FETs. Thus I thought final MOS-FETs are
gone again. But actually, Q24(2N7000) were blown
(please add this to trouble shooting list).

As you see following pix, I noticed the found Q24.

http://ph.groups.yahoo.com/group/BITX20/photos/view/a24d?b=13

5.6V Zenner was break into pieces too.
I replaced them to equivalent and It recovered.

I really enjoyed the contest with the BITX20A.

JL1KRA Junichi

New file uploaded to BITX20

BITX20@...
 

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 : /50 mHzRFGenSch1.PDF
Uploaded by : bkopski <kopskirl@...>
Description : Basic schematic of HB 50 mHz RF Signal Generator

You can access this file at the URL:
http://groups.yahoo.com/group/BITX20/files/50%20mHzRFGenSch1.PDF

To learn more about file sharing for your group, please visit:
http://help.yahoo.com/l/us/yahoo/groups/original/members/web/index.htmlfiles

Regards,

bkopski <kopskirl@...>

ANOTHER APPROACH TO AN RF GENERATOR

bkopski <kopskirl@...>
 

Hi All -

I have for many years been trying to build an RF test source that
would have a reasonably clean signal and be FLAT over a wide freq.
range. I was not able to attain the desired performance until very
recently and in fact just finished building a successful generator
days ago as Ashhar was describing his on this Group. Now that I see
some continuing interest here, I thought I'd share my version for
what it's worth. I am posting the basic schematic in the Files
section, plus some photos.

First, for my purposes, this generator works VERY well. As you can
see in the .pdf schematic, this circuit is basically that of a
buffered, leveled Hartley-variant source. No "voltage gain"
amplifiers are used. Rather, the desired adjustable output level
originates at the oscillator itself and is simply buffered
thereafter. Switched tanks on a FET gate, a single 365 pF variable,
and resistive trimmer-set feedback levels cover from less than 1 mHz
to over 50 mHz in five overlapping bands. The leveling loop holds the
selected output WITHIN 0.1 dB over this range except this increases
to about 0.2 dB variation at the top (50 mHz) range. (My power meter
has a resolution of 0.1 dB.) This level of control holds over all
bands and from band to band over the entire adjustable output power
range.

The output impedance is fixed with a 51 ohm resistor which in turn is
driven by near-zero impedance as dictated by the leveling loop which
samples at the drive to this resistor. I feel the generator is about
as "50 Ohms Resistive" as can be.

The output harmonic content is everywhere more than 30 dB down and
typically more than 40 dB down. It is more than 50 dB down at the
low end of the dial on all bands. The highest harmonic levels are at
the very top end of each band. All this holds over the full output
power range of 0 to over +13. I have no easy way to evaluate phase
noise but this is not an issue in my intended applications.

Power is via a 12 VAC wall wart with +/- 9 volt IC regulators in the
box.

There is a small performance imperfection that is not an issue in the
applications I have in mind for this source, namely the frequency is
pulled slightly as the power output level is adjusted - not a
surprise given the leveling approach. However, this pulling is 5
significant figures down except in the highest band where the
frequency motion over the > 13 dB amplitude range at the top end of
the dial is about 0.4% total.

While I've not looked at this yet, I suspect a variable load (e.g.
going thru Xtal filter resonance) would also tend to pull the
frequency, but this generator is not for that use anyway, and
besides, I can always pad or buffer the output further. However, my
intent is not to use this box for evaluating Xtal filters; rather I
have an HB sweep system for that purpose. Also, this box has a
noticeable housing micro phonic on the highest band – also not a
significant operational issue only discovered accidentally. (Next
one will have relay selected tanks that are better nailed down!)

Here's hoping this offering will be of interest and value to some
BITX Group HB'ers!

Cordially,
Bob, K3NHI

Re: Not BITX : RF Generator

Stanley Grixti
 


Farhan,

What I have done in the past for slow tuning is to put a varactor diode
combined with the main tuning capacitor. This allows you fine control and
also allows you to take the sweep output of the scope so that you can see
the filter shape in real time (sort of poor man's spectrum analyser)

In fact this is a variation on the design in Simple Test Equipment for the
QRPer (GQRP club) for a 'Spectrum Wavemeter'.

for my work, calibrated power output is not required as I am

interested only in relative measurements at the moment. the two things
that I sorely miss in the current build is that the power output is
low for some work (like measuring the Q using the trap method) and I
need slow motion tuning for sharp frequency netting (like measuring
crystal Qs).

- farhan


Re: Not BITX : RF Generator

Tim Ostley
 

Farhan,

What I have done in the past for slow tuning is to put a varactor diode
combined with the main tuning capacitor. This allows you fine control and
also allows you to take the sweep output of the scope so that you can see
the filter shape in real time (sort of poor man's spectrum analyser)

In fact this is a variation on the design in Simple Test Equipment for the
QRPer (GQRP club) for a 'Spectrum Wavemeter'.

for my work, calibrated power output is not required as I am

interested only in relative measurements at the moment. the two things
that I sorely miss in the current build is that the power output is
low for some work (like measuring the Q using the trap method) and I
need slow motion tuning for sharp frequency netting (like measuring
crystal Qs).

- farhan

Re: Not BITX : RF Generator

Ashhar Farhan <farhan@...>
 

quite true about the common base suggestion, i will revise my design
accordingly. this is the benefit of ugly construction, you can revise
as quickly as you can think of it. i will post the results in a few
days.

for my work, calibrated power output is not required as I am
interested only in relative measurements at the moment. the two things
that I sorely miss in the current build is that the power output is
low for some work (like measuring the Q using the trap method) and I
need slow motion tuning for sharp frequency netting (like measuring
crystal Qs).

- farhan

On Tue, Apr 29, 2008 at 4:37 PM, yo8can <yo8can@...> wrote:






To a test generator the output stage is very important. It has to be
unconditioned stable versus the load (which may be reactive), must not
distort the signal and must have a precisely determinated output
impedance (usually 50ohms) in order to not affect the under test
circuit, because this contribute to the results. The common emitter
scheme like Farhan used is not the best. For this function the most
used circuit is a emitter follower, which has a low output impedance
which is adjusted to 50 ohms by means of a series connected resistor.
I've experimented such a scheme with a 2N3866 used as emitter follower
with a 68 ohm resistor between emitter and ground (supplied at 12Vcc,
at Ic=88 mA, lower Ic generated distortions of the signal on a 50 ohms
load, tested by an oscilloscope), and the 50 ohm output impedance is
realized with a 39 ohm series resistor (because the output impedance
of the follower was about 11 ohms). Industrial made signal generators
use most symmetrical emitter followers in push-pull schemes (pnp&npn
transistors). A different principle is used to a russian generator
G4-158 (1-100MHZ/2Vef), by means of a scheme of a RF constant curent
generator debitating on an internal 50 ohms resistor, solution which
assures a truly 50 ohms output impedance, totally regardless about the
load (which may be "very" reactive). So you may add a power emitter
follower to the generator as proposed whith significantly better
results. An other problem is to assure a truly constant output level,
here the solution most used is the AGC. I've used for this a uA723,
the signal being produced with a AD9850 DDS.
73's Romi YO8CAN

Re: Videos

Leonard <bitx@...>
 

--- In BITX20@..., "Arlon Nelson" <anelson@...> wrote:

Ready to align and check out the transmitter
Where can I find the lineup videos that are online.
The kit videos are here:
http://golddredgervideo.com/kc0wox/bitx20avideos.htm
Leonard

Re: Videos

beith.mike <beith.mike@...>
 

--- In BITX20@..., "Arlon Nelson" <anelson@...> wrote:

Ready to align and check out the transmitter
Where can I find the lineup videos that are online.
Thanks

73,

Nels, WØTUP
See the link at the bottom of message 4710

Good luck

mike GM0OXS

Videos

Arlon Nelson <anelson@...>
 

Ready to align and check out the transmitter
Where can I find the lineup videos that are online.
Thanks

73,

Nels, W�TUP
Minot, North Dakota
anelson@... - w0tup@...
http://min.midco.net/ws
Ward County - Grid Locator DN98if
SKCC 31 - Flying Pigs 590 - QRPp-I #760
ARRL - FISTS #8610 - CC #1310 - FISTS WAS #143
FISTS PLATINUM #365 - FISTS SILVER #367
ARRL SSTV WAS #33 - IVCA MIXED BAND SSTV #1
40 MTR CW WAS - DXCC # 39623
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
Two antennas met on a tower, fell in love and
got married. The ceremony wasn't much, but the
reception was excellent.
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*

Not BITX : RF Generator

yo8can
 

To a test generator the output stage is very important. It has to be
unconditioned stable versus the load (which may be reactive), must not
distort the signal and must have a precisely determinated output
impedance (usually 50ohms) in order to not affect the under test
circuit, because this contribute to the results. The common emitter
scheme like Farhan used is not the best. For this function the most
used circuit is a emitter follower, which has a low output impedance
which is adjusted to 50 ohms by means of a series connected resistor.
I've experimented such a scheme with a 2N3866 used as emitter follower
with a 68 ohm resistor between emitter and ground (supplied at 12Vcc,
at Ic=88 mA, lower Ic generated distortions of the signal on a 50 ohms
load, tested by an oscilloscope), and the 50 ohm output impedance is
realized with a 39 ohm series resistor (because the output impedance
of the follower was about 11 ohms). Industrial made signal generators
use most symmetrical emitter followers in push-pull schemes (pnp&npn
transistors). A different principle is used to a russian generator
G4-158 (1-100MHZ/2Vef), by means of a scheme of a RF constant curent
generator debitating on an internal 50 ohms resistor, solution which
assures a truly 50 ohms output impedance, totally regardless about the
load (which may be "very" reactive). So you may add a power emitter
follower to the generator as proposed whith significantly better
results. An other problem is to assure a truly constant output level,
here the solution most used is the AGC. I've used for this a uA723,
the signal being produced with a AD9850 DDS.
73's Romi YO8CAN

Re: Toroid help

Stanley Grixti
 

Hi Mark

Thanks for the info...I shall try it later this afternoon

What did you do for the PA?

73

Stan 9H1LO

Mark Jones wrote:


Hi

My V3 board is on 17M; I used 8 turns bifilar on an FT-37-43.

I changed the VFO to 8MHz and then altered the low pass filter using
"elsie".

There are some OK photos under my call with some details.

Seems to be OK but conditions in the UK are poor at best on 17M right
now - output power as expected and RX hears generated signals but my
ICOM can't hear anything on the band right now either!

Regards,

Mark.

G0MGX

Stanley Grixti wrote:

what toroid could i use and how many turns for T3 (o/p on Q14 collector)
for 18mhz??

i don't have any tv-type cores!

73

9H1LO


Re: sensitivity

Bill Noyce <WBNoyce@...>
 

Remember that the BITX20 has no AGC, so it's not constantly working to
make band noise and weak signals sound as loud as a strong signal.
One rule of thumb for a simple receiver is that it has enough
sensitivity (equivalently, has a low enough noise figure) if you can
hear the noise level increase when you connect the antenna (strictly
speaking, should be when you replace a 50-ohm dummy load with a real
antenna). Do you hear that? Maybe you just want a bit more audio
amplification.
-- Bill

On Sun, Apr 27, 2008 at 9:53 AM, Charlie Ivermee
<charlie@...> wrote:






m0eme432 wrote:
> My Bitx20 seems a little low on RX sensitivity compared to my HF set. I
> was wondering if anyone had placed a small preamp circuit before the
> first transistor? would this help?
> Paul
>
>
>
Paul,

It might be worth further checks, subjectively my 20E is about they same
as my IC 703 with the pre-amp off.

Charlie.

--
M0WYM
www.radiowymsey.org

Wymsey - Ten years Old!
www.wymsey.co.uk

Re: Fig 8.22 - Modular Direct Conversion Receiver of EMRFD

Bill Noyce <WBNoyce@...>
 

You're right, apparently the 10K and 5.6K resistors got swapped by mistake.
You might want to print out the errata found at w7zoi.net -- here's one entry:

p8.14, Fig 8.22. The upper right part of the figure contains the Low
Noise Audio Amplifier consisting of a common base stage followed by a
common emitter amplifier. A follower operates as a capacitance
multiplier to supply low ripple DC to the two LNA stages. The common
base stage is shown with a 10K collector R and a 5.6K/3.3K base bias
network. The collector R should be 5.6K while the base bias should
come from a 10K/3.3K divider. (03Sept06)

Note that this same preamp appears in several schematics in Chapter 9,
with the 10K and 5.6K in their proper places...

-- Bill, AB1AV

Re: Toroid help

Mark Jones <Mark@...>
 

Hi

My V3 board is on 17M; I used 8 turns bifilar on an FT-37-43.

I changed the VFO to 8MHz and then altered the low pass filter using
"elsie".

There are some OK photos under my call with some details.

Seems to be OK but conditions in the UK are poor at best on 17M right
now - output power as expected and RX hears generated signals but my
ICOM can't hear anything on the band right now either!

Regards,

Mark.

G0MGX

Stanley Grixti wrote:


what toroid could i use and how many turns for T3 (o/p on Q14 collector)
for 18mhz??

i don't have any tv-type cores!

73

9H1LO