Date   
Re: Audio amp schematic

Ashhar Farhan <farhan@...>
 

mark,
check the corrected schematic on http://www.phonestack.com/farhan.
the earlier circuit had a typo.
- farhan

On Sun, 27 Jun 2004, Mark wrote:

Anyone checked this - is +V on pin 5 correct?

Should it not be on pin 6?

Mark.





Yahoo! Groups Links




Audio amp schematic

Mark <Mark@...>
 

Anyone checked this - is +V on pin 5 correct?

Should it not be on pin 6?

Mark.

PCB

Bill Schofield <g0bak-m@...>
 

Hi all. I have posted a pic, I hope in the photos section. This is my
first attempt at using Press & Peel to create PCB's as I usually use
the island method etc for my projects. I was so impressed with the
results, to say this was my first attempt, I made the effort to tell
you all about it. See the site at
http://www.ronlin.co.uk/pressnpeel.html
I wish everyone good luck with the project. While I think on, Plumb
Centre in the UK have a 1/2" Delta Tap Washer Cat No C54018 in stock.
The price is £1.80 plus VAT for 10 washers. Not sure if they will
post but they have branches everywhere. All the best, de Bill G0BAK.

Re: Audio amp schematic

Charles Darley
 

Hi
 
according to my diagram  +V should be on pin 6 as mentioned ..
 
looks like pins 5 and 6 need to be changed for each other as output must be on 5 and volts in on 6
 
Charles G4VSZ

-----Original Message-----
From: Mark [mailto:Mark@...]
Sent: 27 June 2004 09:47
To: BITX20@...
Subject: [BITX20] Audio amp schematic

Anyone checked this - is +V on pin 5 correct?

Should it not be on pin 6?

Mark.


filter shielding?

Chris van den Berg
 

Hi all,
I had the intention to build this transceiver when a friend of me
brought this Yahoo group under my attention.
Too bad, now I spend all the time on reading all information instead
of building it ;-)
The nice thing I like is that the design is so basic, so
straightforward and everything (except the final stage) broadband
that it can be adjusted easily to everyones needs.

Because I have several x-tals with a frequency of 4.9152 MHz this
will be the IF frequency and because I want to make it for 18 Mhz, I
will try to cover the phone part with a VXO on about 13 MHz.

Looking at the pictures of other builders, I see several 'islands',
I do not build that way, I just solder every component to each other
(above the copper surface, only connected to it where needed).

What I also saw is that the x-tal filter has no kind of shielding.
Is it worth seperate the input/output of the filter with a kind of
shielding to prevent the signal passing it?

Good luck all,
Chris, PA3CRX

Re: PCB

Hans Summers <Hans.Summers@...>
 

While I think on, Plumb Centre in the UK have a 1/2"
Delta Tap Washer Cat No C54018 in stock. The price
is £1.80 plus VAT for 10 washers. Not sure if they
will post but they have branches everywhere. All
the best, de Bill G0BAK.
What is a "delta" tap washer? I'd be careful... When I bought my tap washers
there were "delta" washers and ordinary ones. But I don't recall what the
difference was. Anyone know?

I got my (non-"delta") washers at my local hardware store where they sell a
pacl of 3 for £0.45 including VAT. I'm happy to send some to whoever wants
them. Farhan is also talking of sending me 1000 from India, and the TV
baluns.

73 Hans G0UPL

(Again owing many people emails, pls QRX)

Re: filter shielding?

Jim Strohm <jstrohm@...>
 

On Jun 27, 2004, at 6:16 AM, vdberghak wrote:

Looking at the pictures of other builders, I see several 'islands',
I do not build that way, I just solder every component to each other
(above the copper surface, only connected to it where needed).
The only reason(s) I can think of _not_ to make 'em float in the air is that this technique has the potential to make the circuit sensitive to microphonics. And in a high-vibration or high-shock environment such as portable or mobile use, the solder joints would tend to fracture and eventually cause intermittent failures long before any visual breakage was apparent.

What I also saw is that the x-tal filter has no kind of shielding.
Is it worth seperate the input/output of the filter with a kind of
shielding to prevent the signal passing it?
Well, you could take the PCB scraps you saved by not using "island" construction, and use it to make shielding.

What's that old bromide -- "You can never be too rich, too thin, or have too many friends" -- add to that the idea that your electronics can never have too much shielding.

Jim N6OTQ

Re: Please suggest for alternative 'linear amplifier module'

Jim Strohm <jstrohm@...>
 

On Jun 26, 2004, at 11:03 PM, MILAREPA wrote:

Dear forum,
The IRF510 and 2N2218 is not available here in INDONESIA,
 
-Could you suggest an alternative for 'linear amplifier module' ?
 
-Can I just use:
HF BANDS QRP LINEAR AMPLIFIER - 4WATT or
TEN WATT LINEAR AMPLIFIER all by Harry Lythall - SM0VPO
Since 2SC.....( Japanese) transistors are available here.
Both those circuits will work fine, as will most any other QRP amp
circuit. A broadbanded circuit is easier to build and use because it
requires no tune-up and is less likely to have a parasitic oscillation.
Be aware that those two amps NEED a low-pass output filter. For 20M,
the BITX20 filter will be fine. For other frequencies, most popular
radio handbooks have equations and design examples for the frequency of
interest.

Readers are reminded that Harry SM0VPO likes to share his work, but
doesn't like seeing others pirate it or claim it as their own. So be
sure to provide attribution (as was done here) when you share his
stuff. He has the best homebrew radio site in the world, and we'd like
to encourage him to keep it online, by respecting his work and his
copyright.

Jim N6OTQ

IF amp pcb

vk3bfa <ablight@...>
 

Hello Fello wBuilders,
think I stuffed up a previous message post - anyway, have posted a
photo of my humble efforts at kitchen sink PCB making for the BITX20
IF Amp - its in the VK3BFA folder. Any comments on probable mistakes
welcome - will try and load it with components tomorrow if I can
ignore customer jobs already on the work bench hi hi. I build on the
track side of the PCB (semi ugly/manhattan) - so much easier to
troubleshoot.....
73 de VK3BFA Andrew

Re: IF amp pcb

John Fisher <k5jhf@...>
 

Very nice PCB, I'm certainly enjoying these photos :-) Thanks to all for your interesting posts :-) Being somewhat of a photographer, I always say "One can never be too rich, too thin, or have too much light" :-) But of course one can never have too many friends or too much shielding :-) Thanks for the bandwidth :-)

 Regards,
 John
 
=============================================
email:      k5jhf@...
photos:   http://photos.yahoo.com/k5jhf@...
files:       http://briefcase.yahoo.com/k5jhf@...
webpage: http://www.geocities.com/k5jhf@...
callsign:    K5JHF
=============================================

-----Original Message-----
From: vk3bfa [mailto:ablight@...]
Sent: Sunday, June 27, 2004 7:45 AM
To: BITX20@...
Subject: [BITX20] IF amp pcb

Hello Fello wBuilders,
think I stuffed up a previous message post - anyway, have posted a
photo of my humble efforts at kitchen sink PCB making for the BITX20
IF Amp - its in the VK3BFA folder. Any comments on probable mistakes
welcome - will try and load it with components  tomorrow if I can
ignore customer jobs already on the work bench hi hi. I build on the
track side of the PCB (semi ugly/manhattan)  - so much easier to
troubleshoot.....
73 de VK3BFA Andrew


"delta" washers & Pads versus point-to-point wiring

Arvid Evans <arvevans@...>
 

Hi

After reding over today's posts...here are a couple of thoughts and
comments:

1) The manufacturer and model number for the faucet washer used in
BITX20 coils is probably much ado about a triviality. The requirement
for air-core (or nylon core, to be more correct) toroid coils in your
BITX20 is a reference to the shape and to the absence of ferrite
material in the magnetic field. I suspect that if you wanted you
could use 'slices' from the body of a plastic ball-point pen. I used
1/4 inch wide slices from a piece of 1/2 inch PVC pipe (a bit larger
than the faucet washers, but also required a few less turns). No, I
don't know what effect the different dielectric constant of the PVC
had on the result.

2) Many years ago I obtained some PCB material that is quite thin
and flexible. My method for making the "pads" is to punch them out of
this material with a conventional paper punch (the pliers shaped type
you can buy for a couple of USD in many local stores). I sometimes
punch out a handfull when I have a few free minutes (it makes a great
distraction during those boring commercials on US Television), or if
none are immediately available I will punch out just what I need as I
build a circuit.
At times I have made pads from thicker PCB material by just punching
them out from PCB scrap(and from used boards when parts have all been
removed) by using the larger lever-operated paper punch on my desk.
Also, in the US Harbor Freight sells a compound-action pliers type
punch (about $10 USD) complete with different sized dies, see
<www.harborfreight.com> and search for "punch".
FYI: My "pads" using the thin PCB material measure 1.4 PF between the
circuit connection and underlying PCB substrata. I'm using "Super
Glue" to stick them down.

3) Yes, when I am in a hurry, like assembling my first BITX20, I
resort to point-to-point self-supported wiring...the UGLY method. It
is quick and effective, but nearly impossible to repair if the
defective part is two or three layers deep in the rats-nest of
connections.

4) My initial BITX20 effort did not use the LM-386 AF amp. Instead
I just used a 741 Op-Amp and relied on headphones-only for the audio
output. I guess I neatly sidstepped the schematic error regarding the
wrong pin being indicated for the + voltage! ;-) Since then I have
added an NPN (2N3904) driving an NPN-PNP (2N3904 & 2N3906) pair for
1/2 watt of audio to the speaker.

Maybe I am different but I see Farhan's elegant design as very
interesting because it allows the builder to match up his particular
incantation of the rig with the contents of his junk box.

My BITX40 is coming along quite well. Several modules have been
assembled and tested with just the IF filter, VFO, and the linear amp
left to finish. I am waiting for an order to be delivered from "Dan's
Small Parts" before I can continue. My junk box became severly
depleted of the more commonly used parts!

73's
Arv
_._

Tap Washers

Bill Schofield <g0bak-m@...>
 

Hi All, Just to clarify, the Delta Washers I mentioned in the earlier
post are shaped more like a standard Torroid a little bigger than a T
50 and not as big as a T68 so I guess around a T55????? A standard
1/2 inch or basin tap washer in the uk is much bigger and the hole in
the centre is quite small. I did purchase some of these also to
compare, Catalogue no C54012 £1.29 + VAT for 10 same Supplier. I use
a PIC LCD Capacitance and Inductance meter that I made last year to
give me the values of the coils, as yet I have not made them for the
BITX. As mentioned in another posting, the core for the winding can
be made out of various things, ball point pen plastic etc. When I
wind the coils I will give some uH values from my meter. All the best
and happy constructing, de Bill G0BAK.

Rig photos

Hans Summers <Hans.Summers@...>
 

Hi

I uploaded my BITX20 pictures into the photographs section
http://photos.groups.yahoo.com/group/BITX20/lst

I also re-organised in there a little, so that the photos which were at the
top level are now sorted into directories by callsign.

Some notes on my version:

You will see the first picture has the BITX20 in the foreground and my
80/40m homebrew receiver
http://www.hanssummers.com/radio/polyphase/index.htm in the background. The
frequency counter of the receiver (also homebrew, see
http://www.hanssummers.com/radio/sfreq/index.htm ) is hooked up to the
BITX20 VFO on 4.278.16MHz. You can see the same frequency reading on the
BITX20 readout, i.e. 14.2 from the dial + binary 64 + 8 + 4 + 2 + 0.5 =
14.278.5.

The other picture shows 14.175MHz. I fitted an on/off switch, tx/rx switch
and frequency counter on/off switch (in case the counter generates an
objectionable birdie or other noise). A greed LED indicates power is on, the
red LED indicates TX.

I included a photo of my simple 2-chip 8 LED binary readout frequency
counter that I installed in the BITX20 front panel. The details of this
counter can be found at http://www.hanssummers.com/radio/sfreq/index.htm .
It costs approx £2.00 in parts.

I constructed my BITX20 as a series of 15 modules. The VFO is built directly
on the main chassis behind the tuning controls. The remaining modules are
each built "ugly" on a 2 x 1 inch piece of PCB stock, mounted at right
angles to the chassis. This method will allow me to experiment easily with
variations on the different modules. If necessary I could easily move all
the modules around because they are just soldered to the base board at
either end of their 2-inch length. This method also provides for some
"automatic" screening between each stage. All the modules except the product
detector/exciter are shown in the "modules" photo subfolder. Sorry for the
low resolution images of the modules. Some of the main pictures were taken
on a friend's camera. if you have an old unwanted digital camera which is
less old than my 640 x 480 resolution dinosaur, you know where to send it
;-)

The rig is now awaiting testing and debugging but due to family commitments
there may be some significant delay.

72/3 de Hans G0UPL

Re: manhattan style pads

Hans Summers <Hans.Summers@...>
 

 
> I agree with Hans -- I have really seen no difference between
> construction on a ground plane when using pads and building
> without them, other than building without is faster.     
> There is rarely a need to go as high as 10M with the
> resistors if you don't have them around.   Something
> much smaller values will work just as well.
 
Yes, true - I found that Rapid Electronics sell a very useful resistor variety pack containing 1000 resistors in 63 values from 4.7ohms to 10M. The number of each varies from 5 to 30 depending how common they think they are. E.g. they have 30x 10K, 100K etc, and only 5x 830K. Price is £9.75. I just *KNOW* I probably won't want the 10M and they've put 20 of them in. Thought I'd start at the top and work my way down through 6M8, etc.
 
72/3 de Hans G0UPL
http://www.HansSummers.com

Block Diagram

Charles Darley
 

Hi

I have just posted a block diagram of the BITX - I hope I have
correctly identified all the section of the main schematic diagram.

Let me know of any errors.

This will be used as part of a teaching aid to Amateur Radio Students
in UK.


Charles

Off topic - i am blocked out

Ashhar Farhan <farhan@...>
 

for the last 48 hours, groups.yahoo.com has been blocked out by the two
major bandwidth providers to india. most of my internet accounts belong to
isps that in turn take their bandwidth from either of these two (i have
several).

this has been done as the indian govt. asked the isps to block certain a
fanatic group (read 'hate') from being accessed from india. some of us
are fighting this with the govt. and i hope that the access will be
restored soon.

until such a time, i cannot see the pictures that are being uploaded
although access the emails (the emails are to and from my server located
in boston). i cannot wait to see all the lovely efforts being made by
everybody and it feels like being left out of the party.

though a number of users have suggested using proxies to gain access to
the site, i want to regain my right to free exchange of ideas and
information as much as i believe the fringe hate group should. the issue
has become significant to a number of us in india.

- farhan

A tale of two tap washers

Hans Summers <Hans.Summers@...>
 

...in which G0UPL travels to his local hardware store to further investigate
the nature of the infamous tap washers, and in particular the differences
between ordinary and "delta" washers. Samples were successfully returned to
my office and analysed in the photocopier next to a ruler then via the
scanner ;-)

Attached is a picture. For the benefit of those who don't get emails but
read this on the Yahoo group website, I've put it in the G0UPL photos folder
too. Note: Ruler measurements to the left of the 6 inch mark are in 16'ths,
to the right are in 10'ths.

Both are know as 1/2 inch tap washers but both measure more than 1/2 inch
(12.7mm). As close as I can measure with my ruler:

"normal" "Delta"

Outside diameter: 23/32 (18mm) 19/32 (15mm)
Inside hole diam: 5/32 (4mm) 3/16 (5mm)
Thickness: 5/32 (4mm) 3/16 (5mm)
Price: £0.45 per 3 £0.45 per 2

72/3 de Hans G0UPL
http://www.HansSummers.com

Re: BITX20 component list

ik1zyw <pcravero@...>
 

--- In BITX20@..., "ik1zyw" <pcravero@a...> wrote:

It's me again.

Has anyone attempted to list all BITX20 components? I haven't found
any link on Ashan's page. Here is my attempt at listing all
components, except for the IRF510 PA (had no time).
I have uploaded in the Files section a TXT file with a component list
for BITX20. It DOES include driver/PA section but it DOES NOT include
inductors. The list is meant to be a list you give to the shop
attendant and then return home with everything you need to build a BITX20.

Tap washers can be purchased at a hardware store, which usually
doesn't sell electronic components. Coils wire can be salvaged from
old transformers.

Please someone cross-check my work!

73,
Paolo IK1ZYW

Re: Off topic - i am blocked out

Hans Summers <Hans.Summers@...>
 

Farhan

Sorry to hear of your problems. I'm sure you are right to fight for the free
exchange of information.

One possible solution is to use an anonymisation service such as
http://www.anonymization.net . In this case the URL to the BITX20 group
would become
http://www.anonymization.net/http://groups.yahoo.com/group/BITX20/ .

I work for a US company. One might expect freedom of information to be
assured. But they insist nevertheless on blocking any website which meets
some criteria of being pornographic, related to betting and gambling, or any
terrorist activity. I don't know if they thought that perhaps we would sit
here in the office in full view of our colleages watching porno movies or
something. Anyway be careful I'm getting on my soapbox here...

To cut a long story short, I had a big battle and I lost, they still refuse
to change it. The battle arrived when I tried to look at the website of
Thomas OZ2CPU, whose excellent web page http://www.webx.dk/ I have visited
many times in the past. Only to find that it was blocked, with a message
something like "if you feel this web page has been wrongly blocked, please
contact the IT helpdesk". You can contact them as much as you like, and if
they don't feel it is related to your business requirement they won't
unblock it, even if it IS wrongly blocked. A colleague wanted to buy
something from a camping store. Couldn't access it. So had no option but to
take a long lunchbreak of 2 hours, on company time, to visit the store. Even
if it's non-business, it can assist business by making the employee's life
easier.

All of which led me to write my own internet browser application, which
enclosed an Internet Explorer component. On coming across the hated IT
helpdesk message, it redirects its enquiry to anonymization.net which
(nearly always) gets the page Ok. This is all done in an invisible way, the
actual real address at anonymization.net is hidden from the user. So I was
able to give the application to my friends in the company to assist them in
streamlining their non-business related activities, in the knowledge that if
the information finds its way back to the IT dept, at least it won't be
instantly evident how it works, though I don't doubt that they would be able
to trace it eventually, having access to everything.

Sorry to have got on my soapbox even though I tried to stay off it - this
issue touches a raw nerve. Good luck with battle which is much more serious
than my little problem here.

73 Hans G0UPL

-----Original Message-----
From: Ashhar Farhan [mailto:farhan@...]
Sent: 28 June 2004 12:59
To: BITX20@...
Subject: [BITX20] Off topic - i am blocked out



for the last 48 hours, groups.yahoo.com has been blocked out by the two
major bandwidth providers to india. most of my internet accounts belong to
isps that in turn take their bandwidth from either of these two (i have
several).

this has been done as the indian govt. asked the isps to block certain a
fanatic group (read 'hate') from being accessed from india. some of us are
fighting this with the govt. and i hope that the access will be restored
soon.

until such a time, i cannot see the pictures that are being uploaded
although access the emails (the emails are to and from my server located in
boston). i cannot wait to see all the lovely efforts being made by everybody
and it feels like being left out of the party.

though a number of users have suggested using proxies to gain access to the
site, i want to regain my right to free exchange of ideas and information as
much as i believe the fringe hate group should. the issue has become
significant to a number of us in india.

- farhan






Yahoo! Groups Links

TV Balun

g4dfv2004 <duncan.walters@...>
 

Hello, I have uploaded a photo of a two-hole "binocular" ferrite
core (see G4DFV album). Ashtar, please can you tell me if this is
anything like the TV balun that you have used?
My core measures 13mm x 7mm x 6mm, the holes are 3mm diameter and
the centres are spaced 6mm.

Duncan G4DFV