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Off topic - i am blocked out
Ashhar 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 |
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Re: manhattan style pads
Hans Summers
开云体育?
> 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 |
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Rig photos
Hans Summers
Hi
I uploaded my BITX20 pictures into the photographs section 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 in the background. The frequency counter of the receiver (also homebrew, see ) 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 . 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 |
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Tap Washers
Bill Schofield
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. |
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"delta" washers & Pads versus point-to-point wiring
Arvid Evans
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 _._ |
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Re: IF amp pcb
John Fisher
开云体育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:??? files:??????? webpage:? callsign:??? K5JHF =============================================
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IF amp pcb
vk3bfa
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 |
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Re: Please suggest for alternative 'linear amplifier module'
Jim Strohm
On Jun 26, 2004, at 11:03 PM, MILAREPA wrote:
Dear forum,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 |
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Re: filter shielding?
Jim Strohm
On Jun 27, 2004, at 6:16 AM, vdberghak wrote:
Looking at the pictures of other builders, I see several 'islands',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.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 |
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Re: PCB
Hans Summers
While I think on, Plumb Centre in the UK have a 1/2"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) |
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filter shielding?
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 |
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Re: Audio amp schematic
开云体育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----- Anyone checked this - is +V on pin 5
correct?From: Mark [mailto:Mark@...] Sent: 27 June 2004 09:47 To: BITX20@... Subject: [BITX20] Audio amp schematic Should it not be on pin 6? Mark. |
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PCB
Bill Schofield
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 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. |
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Re: Audio amp schematic
Ashhar Farhan
mark,
toggle quoted message
Show quoted text
check the corrected schematic on . the earlier circuit had a typo. - farhan On Sun, 27 Jun 2004, Mark wrote:
Anyone checked this - is +V on pin 5 correct? |
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Please suggest for alternative 'linear amplifier module'
MILAREPA
开云体育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. ?
?
-What? module ( coil, capacitor, x-tals) to
change?if need another band say 10MHz ?
?
Thank you. |
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Re: manhattan style pads
Wes Hayward
开云体育Hi All,
?
Actually, I think that the Manhattan in the QRP
construction method really refers to the use of straight wires on a 90 degree
grid.?? At least that is where the term
originated.?????Typical integrated circuits use a
layout that follows a Manhattan format.? A recent reference is John Baliga,
"Chips Go Vertical," IEEE Spectrum, March, 2004,
pp43-47.????
?
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.
?
My son and I picked the term "ugly" on our 1981 QST
paper "The Ugly Weekender" for a specific reason:?? We wanted to
emphasize that there is no relationship between circuit performance and the
"pretty" nature of the construction, including that on a printed
board.?? In this case, it is the use of extensive ground plane that
makes the circuitry work well.
?
73, Wes
W7ZOI
?
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Re: manhattan style pads
Bruce Raymond
开云体育Mark
& Hans,
?
Many
thanks for your replies.? Small rectangular pads should work
just
fine,
and those I can come up with - I don't know why it didn't occur
to
me.
?
Thanks
for your help,
Bruce/nd8i
?
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