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

the 1 Khz drift is more of a construction problem that a design problem.
I would suggest that you try the following:
1. make all the components connect to each other with short leads and without any 'jiggly' wires.
2. put an epoxy glue over the coil and stick the coil to the board with a drop of expoy.
3. put a sheild around the vfo (i know it is too much work).
4. Are u connecting to the tuning capacitor with flexible wire? use a short stiff copper wire or a resistor tail end.The ground end should be directly in contact with the chassis.
5. Make sure that your regulator is actually regulating. Check the diode (i have often mistakend 1N4148s for other zeners).

Unfortunately, an open VFO on a work-bench is rarely stable. Especially, if your coil has an low permeability like the tap washers.

- farhan

Thanks for advice dear Chris,
Saw on the forum that the BITX17 already seems to exist!
OK, past couple of days I started to setup the power supply unit
capable of delivering the required voltages.
Also did some trials with a VFO working from 8.060 - 8.180 MHz. (+ 10
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.
Or maybe a FET Hartley oscillator. We'll see.
Bye for now and till next time.
Dank voor je reactie Chris. Leuk om te zien dat andere om druk met de
bitx in de weer zijn.
73 de Ron
pa2rf


--- In BITX20@..., "vdberghak" <vdberghak@z...> wrote:

Dear Ron,
splended idea to make it for 17 mtrs.
In your message you asked for suggestions, you want to have more
suggestions then all the postings in this newsgroup, including
Photos, Files etc?
Can you be more precisely what else you need?
By the way, you can show your progress in this newsgroup, you do

not

need an other website for it.
Best regards,
Chris.

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...





---------------------------------
Do you Yahoo!?
Yahoo! Search presents - Jib Jab's 'Second Term'

Dear Ron,
splended idea to make it for 17 mtrs.
In your message you asked for suggestions, you want to have more
suggestions then all the postings in this newsgroup, including
Photos, Files etc?
Can you be more precisely what else you need?
By the way, you can show your progress in this newsgroup, you do not
need an other website for it.
Best regards,
Chris.

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...





---------------------------------
Do you Yahoo!?
Yahoo! Search presents - Jib Jab's 'Second Term'

---

Do you Yahoo!?
Yahoo! Search presents -

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 : /MFJ-9420-CW-module-1.gif
Uploaded by : vu3wjm <vu3wjm@...>
Description : MFJ Trvelradio CW section that may be adapted for BITX

You can access this file at the URL:


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


Regards,

vu3wjm <vu3wjm@...>

---

Do you Yahoo!?
Get it on your mobile phone.

How does one go about with full QSK on BITX20?
There is very little switching around.

the most crucial point to me is that the receiver input needs to switch from the linear amp's output to input. that makes for possible feedbacks if not isolated properly.

on TX, the bitx's output has to be routed to the linear's input and the linear's output to the antenna. we should assume that this is how it is permanently wired. during tx, the linear amp's output should not get back into input via the electronic switching that will connect the bitx directly to the antenna.

any ideas?

- farhan

--- In BITX20@..., "vu3wjm" <vu3wjm@y...> wrote:


Hi Rahul

Here we have completed 2 BITX 20s. We used the ver. 2 layout for
PCB. PCB is thankfully without any mistakes however Pin 2 of LM386
also needs to be grounded to ground plain nearby to avoid ground
loop. (Will correct and upload corrected PCB shortly)

Look's really nice, can't wait to make one.!!

73 de OZ2AFY

paul,

the PCBs have been printed component side! to mark the correct side, i had put the letters BITX in the middle of the PCB as a reminder so that it reads properly.

I guess the fault is partly mine, I am used to imagining the circuit from topside, so i designed it from component side. This is my first PCB and i designed it using the Microsoft Paint program. I should have flipped the entire image over before uploading it. I felt that the builder would figure out the correct side looking at the "BITX" text.

Now, there are two resolutions:
1) for the existing boards, put the LM386 on the foil side.
2) bend all the IC legs by 180 degress so that they are all pointing up rather than down, then flip the IC over and solder it in place on the component side.

The new boards will have take care to flip the circuit around.
It might be a good idea for those buying from FAR to be refered to the BITX20@... for updates and help with assembling the board.

- farhan

---------- Forwarded message ----------
Date: Sun, 23 Jan 2005 13:43:05 -0500 From: paul daulton <k5wms@...>
To: farhan@...
Cc: farcir@...
Subject: Assembling Far bitx boards

Ashhar, I have nearly finished assembly of the main board I received from
Far Circuits
a couple of weeks ago. I am copying Fred Reimer( FAR CIRCUITS) . I am in
no way
disapointed with the design or quality of the boards. I'll review the
experience I had and
recommend a solution to one problem.
See attachment bitx2.jpeg . Looking at the board from the top view with
the Band pass
filter in the upper left hand corner of the board, the circuit proceeds
left to right through
the first bi amp, diode mixer , 2nd bi amp, filter, 3rd bi amp, then bfo
on right side of picture. Lower edge of board in picture left to
right,has tx amp vfo, and rec audio. Your text stated the transistors in
the bi amps face each other and all other transistors face to the
rightexcept the mic amp. All of this agrees and makes sense as the layout
follows the schematic. The exception is the LM386 stage where the IC
layout is a mirror image. I dont know if I speified the orientation
wrong to Fred or if there is an error on the rx amp layout. There is an
easy solution: I mounted the LM386 IC on the bottom side of the board to
achive the correct pinout for the lm386. You can advise Fred if the
layout was printed as a mirror image or if there is a mistake on the 386
stage. It would be helpful to
add a notation like "viewed from foil side" or "viewed from component
side". Personally I like the board as it is reversed I could translate
the mirror image but it would take more time. Fred has made a quanity of
boards rather than scrap these I would advise him to
ship with a note on correctly installing the audio IC.See attachment bitx1
for Ic placement.
Two other minor descrepancies. 1. there is a trace missing from L1 in the
bandpass filter to the pad where the top of l1 solders in , no problem
just poke the wire through the hole
and run it to the trace going between the 10pf cap and the 2.2pf cap. 2.
there is a diode shown on the schematic from the 12r connection to the
junction of the 100 ohm and 220 ohm resistors that supply the Audio
output IC and the driver, I did not find a place for this
on the circuit board. This shouldn't be a problem and the circuit will
function fine without
it.
Thanks to both of you for your time and efforts on this project. What you
see in the pictures took me about 7 hours time. I dont know the cost as
almost every thiing came from my stock. I bought a few resistors and a
half dozen 2n2222's form local RADIO SHACK store., I usually buy .1uf and
such in bulk.
I am leaving tonight and wont be back until Friday. I have every thing on
board except zener and coils. Testing will have to wait untill next
weekend.

Hi!

Here we have completed 2 BITX 20s. We used the ver. 2 layout for
PCB. PCB is thankfully without any mistakes however Pin 2 of LM386
also needs to be grounded to ground plain nearby to avoid ground
loop. (Will correct and upload corrected PCB shortly)

First we tried local coils type similar to Toko, 11 turns of 45 SWG
were used. later we replaced these with 10.7Mhz IF coils with link
coupling and slightly lower resonating capacitor. Overall
improvement was noticed.

Playing around I also tried replacing the IF amp in RX chain with a
2 transistor shunt feedback type adjusting few components to
maintain the impedances. Now the signals come booming in even on a
very inefficient antenna system.

VU3SUA Sunil my friend here was first to fire his rig while I kept
fiddling with mine. Hope to post pictures soon.

Thanking all for their invaluable contributions on this project.

73

Rahul VU3WJM

Kumar

Please see message 102: for
some details of the tap washer I used. I bought some samples of ordinary
"1/2-inch" tap washers and "delta" tap washers, and measured the size of
both. There is a photograph in the G0UPL folder of the photos section
, showing both types of
washer next to a ruler. The larger is the "ordinary" washer (left hand side)
but the "delta" washer on the right is thicker.

73 Hans G0UPL

hello,
any one help me for bitx-20 tap-washer, it's size ,
it's thikness and it's inner and outer length.
if any one have details in this regard then please
help me.
with 73's
de kumar gautam

________________________________________________________________________
Yahoo! India Matrimony: Find your life partner online
Go to:

What you also can do after following the advice of Arv, is combining
the tap washers to a bigger thickness. If the diameter differs a lot
from the normal dimension, it would not make sense but is only the
thickness is the point, amass more together and the inductance will
be increased.
Good luck,
Chris.

I bought a pack of 20
deferent tap washers, wound a coil and measure inductance. The
inductance is very low, about 1,2uH at 70 turns. I guess the tap

washer

is simply to thin. What are dimensions for tap washers that you use?

开云体育

FYI...

Here in the US, tap washers (i.e. faucet washers) come in various sizes, from over 1 inch OD down to less than 1/4 inch OD.?? For my first BITX20 I used those that were for bathroom basin faucet's and are about 1/2 inch OD and about 1/4 ID by almost 1/4 inch thick.? I had to use #40 AWG wire to have room for all the windings on the VFO coil.

For my second BITX (a BITX40) transceiver I used some unknown black toroid cores from my junk box and just added turns until I was close to the correct inductance.? Then using a variable capacitor that has a calibrated (Pf) dial I found the capacitance necessary to reach resonance, then substituted the correct fixed capacitor, and it all worked as anticipated.? My guess is that something like this procedure could also be used with the "tap washer" toroid forms.? Just add turns until one is close to the correct inductance, then add a fixed capacitor to bring it into proper resonance.?

Of course for the mixer coils one does not want to add any capacitors as these are intended to be broadband transmission-line transformers.? On these I used the number of turns specified by Farhan and everything worked fine.

I hope this helps.

Arv K7HKL
_._
On Mon, 2005-01-17 at 10:19, vdberghak wrote:

Fixed value coils can not be used for this application.
Regards,
Chris.

Somebody also said that he used fixed value rf chok it's that

efficient?

73, Uros S56WVT

Hello Everybody

Yesterday I have almost finished my BitX - mainboard. I have etched pcb board. I have only problems with tap washers, I bought a pack of 20 deferent tap washers, wound a coil and measure inductance. The inductance is very low, about 1,2uH at 70 turns. I guess the tap washer is simply to thin. What are dimensions for tap washers that you use? Somebody also said that he used fixed value rf chok it's that efficient?

73, Uros S56WVT

I received two main boards from Far Circuits yester day Jan 8,2005
excellent workman ship, well worth the money. Dave w5dsb and I plan
to build two rigs for 40 meters. Will post pictures when available.
73 Paul Daulton K5WMS

Far Circuits is offering the BITX20 PCBs.

- farhan