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Message Dear Friends, ? I have just read all of the original posts to this new yahoo group, and I am delighted. This is a fun and exciting project and I am recommending it to all my friends?in the Austin QRP group. We have many builders here who might be delighted to?make?this cool project. Thanks to all for bringing this together, and especially to Ashhar Farhan for all of his work. It is truly a marvelous project :-) ? http://www.phonestack.com/farhan/bitx.html ? ?Regards, ?John ? Austin, Texas ? ============================================= email:????? k5jhf@... photos:???http://photos.yahoo.com/k5jhf@... files:???????http://briefcase.yahoo.com/k5jhf@... webpage:?http://www.geocities.com/k5jhf@... callsign:??? K5JHF =============================================

Reminder everyone: deadline for orders for all the semiconductors + crystals + tuning capacitor + trimmers is tomorrow at 12:00 GMT (13:00 UK Time). 73 Hans G0UPL

Message ? I have now placed the bulk order for BITX20 components. I have emailed all those who asked for the components. If you haven't heard from me then I have probably forgotten you in which case shout. ? Due to a further bulk price reduction on the crystals, and that the price quoted on the telephone ended up less than in the catalogue, they were just ?0.223 each. The 2N2219A were also cheaper because more than 10 were ordered. So the overall price came down a little. ? I have ordered two extra complete sets in case any newcomers want them, as listed below. The price is now ?8.19 for one of these sets + postage at cost (?0.28 UK). I hope someone will want these sets because otherwise I'll have them hanging around here doing nothing. ? I also ordered some extra 10MHz crystals and can provide them at ?2.23 per set of ten, + postage at cost. ? One component set contains: ? Qty 10 of 10.000 MHz crystals, HC49 style Qty 25 of BC547B transistors 2N2219A driver transistor IRF510 MOSFET Qty 15 of 1N4148 diodes 36V Zener diode 9.1V Zener diode 5.6V Zener diode LM386N-1 Audio Amp IC (correct variety) Qty 5 of 2-22pF trimmer capacitor Miniature tuning capacitor* ? * NOTE: The tuning capacitor is one of the miniature kind as used in portable radios. Size is 20.2 x 20.2 x 10.8mm. Control shaft is 6.6mm diameter tapped with 2.6mm thread. Panel mounting is via twwo 2.6mm tapped screws next to the control shaft. Capacitance: AM section 3.0 - 141.6pF, Oscillator section 4.0 - 59.2pF. So in parallel you'd have 200pF which is less than Farhan's design for 350pF. It might therefore be necessary to alter the VFO coil to get the required tuning range. ? 72/3 Hans G0UPL http://www.HansSummers.com

I did a little bit of poking around, and found that Mouser offers these at USD$1.50 each, or $1.24 in 100-pc quantities. For stateside users, it might be possible to set up a volume buy and then distribute them -- US mail is $0.60. A 2 oz. Airmail Letter is $1.55 to India, $1.60 to many places in Western Europe. Mouser has no minimum order, but they ship UPS or Fedex, and it'll probably be around $5.00 for the smallest size pkg. I found some on ebay, but the seller's asking nearly twice the Mouser 100-pc price and he also charges rapacious shipping. For what it's worth ... Jim N6OTQ

---------- Forwarded message ---------- Date: Thu, 24 Jun 2004 10:22:26 +0530 From: Ashhar Farhan <computercorp@...> To: arvevans@... Cc: farhan@... Subject: RE: BITX20, 40 or 75 M versions? dear arv, you have spent a great deal thinking about the design and the possiblities. it is wonderful to see that amongst us the natural need to push the envelope is well and alive. when i had declared to W7ZOI that the design is frozen, he was skeptical and hopeful at once. he said, wait until someone decides to do things with it that you hadn't even thought of. i guess the idea of an 'open source' design like BITX20 is that you have a simple basic design that invites adaptation and evolution. very interesting points, you raised. let me give you my side of the story on these: I didn't want to stray away from 10MHz crystals as they seem to be the cheapest and most universally available of the lot. An interesting variation is that you can use a 10.7MHz standard filter and the same VFO will cover 20 and 40 meter bands. Only the RF preselectors need to be switched. this design was made primarily for Indian hams (although i dont know of any who have started to build this in india yet). DDS chips are hard to come by. The entire transceiver costs about 10 dollars to build in india. the DDS chip costs much more. this brings me to the issue of DDS. My personal taste is for purely analog designs. It is a very personal choice. I spend most of my time writing voice over IP software which is wholly digitally. For me radio is a way of getting away from it all. I would rather spend the evening tempurature compensating a low noise FET VFO rather than fight a noisy DDS. But again, it is a purely personal choice. I have seen some pretty good cleaning PPL loops around a basic DDS. If any, I am inclined to implement a Huff and Puff stabilizer for the VFO as a add-on. On the BITX20@..., you will see that Hans Summers (www.hanssummers.com) has a binary counter made of two 74HC4040s. This seems ideal to me. I have avoided it from the basic design to keep the construction challenge low. I personally use my lab frequency counter along with my transceiver for frequency spotting. I keep the counter separate because i found that unless they are well sheilded, the counter tend to generate a lot of noise that back couples from the VFO into the receiver front-end. the primary filtering is provided by the 10 MHz filter. that is why, the modulator is so sparse. i think two back to back diodes could clip the RF to provide better throughput. The trouble with this approach is that you will have to switch this off for CW and PSK31 to preserve the gaussian shaping of these keyed modes. just upsetting the modulator balance might not give you a full carrier as the carrier oscillator is set to the edge of the filter. a better idea might be to add a sidetone audio oscillator and inject it into the audio amplifier as well as the modulator. probably you can get the mic amplifier oscillating with an RC feedback circuit. let me confess, most of my personal operating of BITX20 has been on CW and PSK31. not ssb. I use a morse generating program running on my thinkpad feed into the mic input of the BITX20. i do this because it allows to be leave the BITX20 running at the other end of the table and continue my mng qth work (i telecommute to work. my 'office' is a server in an underground dungeon of rackspace in boston). if i hear an interesting station on CW, i just have to switch windows and start a ragchew. i now have a two relays working in my own build. i control it through the serial port of the my thinkpad. the thinkpad is programmed to do a lot of things including run an AGC, generate morse, VOX and a bit of voice compression. the code is messy and patchy. i will post this as soon as i get some time from my mng qth. quite true. and i should have done this. too lazy to solder an audio amp together. there is one in the first chapter of EMRFD. i think i will post that circuit on the site. Yes, 75M is too noisy in the tropics. In europe and usa, it seems to be the preferred local band. plus, the indian cities are too congested for a 75M antenna. 75M would mean using VFO at 13.5MHz or at 6.5MHz. If is always preferable to have your VFO running on the higher side of the IF to reduce the birdies but stability threatens. At 13.5MHz, you could use a VCO with a 10 turn pot to for tuning. <Each band will require a different set of coils. If you have worked out a set, do send us the details. this information needs to be deciminated. thanks for the kind words. i think far lesser credit should really be attributed to me. most of these circuit blocks came off standard works like Solid State Design and Experimental Methods in RF Design. W7ZOI gave me a huge lot of encouragment and advice on making the rig better. For instance, having a triple tuned circuit on the input was a small but very important change (two capacitors and a coil) that remarkably improved the overall receiver performance and transmission purity. om hans summers has been an exceptional organiser who is marshalling us all to gather together and get on with soldering. he is organising for components, people and places. i am trying to source him with some key components that are very cheaply available in india. thanks for dropping in the email and do stay in touch. 73s, - farhan _________________________________________________________________ Pay Cash on delivery on lakhs of products. http://go.msnserver.com/IN/50757.asp Only on Baazee.com

I've completed the VFO today, uploaded a couple of pictures to the reflector. Not too sure about L3 - used a fixed choke instead of winding. Any thoughts? Seems to be working OK.

The two extra sets are already accounted for! Seems I should have bought more spares, but I didn't really want to be stuck with components and be unable to do anything with them. I can get more sets, but without the savings from getting 10+, 25+ and 100+ prices on some items, the price would be ?11.64 + postage (compared to ?8.19 for this bulk-purchased set). Alternatively, tell me you're interested and we'll wait say until next Wednesday same time (13:00 UK time) and see how many orders arrive. Perhaps get some quantity discounts again, if there are enough more people interested. What do people think? And if anyone needs any particular component and can't source it locally (e.g. IRF510 being sent to Baino in Singapore) then I can sort that out for you too, just email me. 72/3 de Hans G0UPL

I thought this forum was focused on the BITX20. Have I gotten into the wrong forum by accident? Arv - K7HKL -----Forwarded Message-----

i have been quitely following hans' travails on rec.radio.amateur.homebrew with his digital counter experiments. i dug out a counter from my junk box. it consists of just a 74HC4020. the output of the fed to the sound card of my PC. on the PC i wrote an application to count the zero crossings and multiply the result by 1024. it gave a rough indication of where my VFOs were. the counting took a second. but it is a rough and ready instrument. like most amateur intrumentation. but that brings us to an often overlooked piece of equipment that is present in almost every shack. the PC. i know that a number of us cannot live without spice. i haven't figured out how to use it. but for many of us, designs do start with spice. "can i spice it?" is a regular refrain on the net. a number of excellent design tools written by hams are useful around the home lab. i use a large number of small code snippets to calculate inductances and capacitances from a test oscillator's frequency readout. another useful application of the PC is as spectrum analyser workng at audio frequencies. while this may not seem much at first glance, if you feed the output of direct conversion receiver to the PC's sound card and run a DSP software on it, it turns into a fairly useful measurement. for instance, you can evaluate the crystal filters, tune the front-ends etc. a half unfinished project at my shack is a spectrum analyser that uses this principle. the PC is a powerful a DSP as you can hope to own. the problem is in getting signals in and out of it. the only available means of doing it is via audio (baseband). i have used a PC based scope too. but that is a costly option. costlier than the PC itself. but it might be interesting to see how useful can the ordinary PC become by strapping some home made circutis around it. does anybody have more stories about using PCs in the home lab? - farhan

Hello Just to let you know that all the components arrived this morning, from three different suppliers. The LM386 was from Farnell because I wasn't sure that the Rapid Electronics version was the correct LM386N-1 version. All components have been counted out and shipped, UK orders by first class post (should arrive tomorrow morning) and international orders via airmail. When I'd finished there were 14 BC547 transistors left over. This could be because they are so cheap that counting them precisely costs Rapid more than giving a few extra. Or it could be that I messed up my own counting, as the whole process was rather tedious and I have been having a very stressful day. If anyone is missing any then let me know, or needs some extra spares. I owe quite a few of you emails and also have a couple of other things to say, but am too busy to do it today so pls QRX 72/3 de Hans G0UPL http://www.HansSummers.com

All I'm happy soldering here, but have a question: In the text for the BITX20 it says "If you are using this for 14MHz and above, the BFO will need a coil in series with the crystal". This is what I have done - seems to work OK (see G0MGX folder in pictures on reflector). I just saw the alternative coil data that has been posted on the reflector and that says "L3 was used in series between the crystal and the 22pf trimmer cap plus I added 7pf Mica fixed cap across the trimmer. Needed for USB" I am therefore confused! Can anyone shed any light on this? Mark. G0MGX

Help please... I'm new to this forum thing, so I have to ask "How does one go about posting a schematic or picture of BITX related info"? I sent an attached file with one of my posts and now my email post is there but the attached .gif file is referenced as "Not Saved". )-8 Thanks, Arv - K7HKL _._

G'day Troops, I note that one or two contributors have mentioned attachments (which do not appear). At the same time there are some photographs which CAN be accessed. Being a Bear of Very Little Brain, I would appreciate it if some kind person would explain - particularly as in the near future there will no doubt be proud builders anxious to display their new-born transceivers. Regards, Sam C.

Many thanks Hans - my set of components arrived today! Payment was sent straight away by first class post. Keep up the excellent work! Duncan G4DFV

Anyone checked this - is +V on pin 5 correct? Should it not be on pin 6? Mark.

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.

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

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.

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

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 _._