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Re: Components
Jon Harris
<AOL> Thanks Hans, all arrived safe and sound
toggle quoted message
Show quoted text
Jon H. ----- Original Message -----
From: "William Ford" <ford1@...> To: <BITX20@...> Sent: Friday, June 25, 2004 10:18 AM Subject: Re: [BITX20] Components Component parcel received today.many thanks Jack ----- Original Message ----- From: Hans Summers To: 'BITX20@...' Sent: Thursday, June 24, 2004 4:57 PM Subject: [BITX20] Components 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 Yahoo! Groups Sponsor ADVERTISEMENT ----------------------------------------------------------------- ------------- Yahoo! Groups Links a.. To visit your group on the web, go to: b.. To unsubscribe from this group, send an email to: BITX20-unsubscribe@... c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. |
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BFO Clarification?
Mark
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 |
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Re: The PC as a lab instrument
Hans Summers
I thought this forum was focused on the BITX20.Hey it wasn't *that* far off topic! Have a look back in the archives... It stems from Farhan's questions about PC use which also relates to his telling us previously about him using his computer for some audio and AGC processing. Several people have asked for possible AGC circuits for the BITX20. I'll see what I can find over the weekend. 73 Hans G0UPL |
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Fw: RE: The PC as a lab instrument
I thought this forum was focused on the BITX20. Have I gotten into the wrong forum by accident?
Arv - K7HKL -----Forwarded Message----- From: Hans Summers <Hans.Summers@...> Sent: Jun 25, 2004 7:34 AM To: "'BITX20@...'" <BITX20@...> Subject: RE: [BITX20] The PC as a lab instrument <html><body> <tt> <BR> does anybody have more stories about using PCs in the <BR><BR> Farhan, I don't have a PC at home at all, except an old laptop my XYL uses<BR> for internet access. I prefer to do everything without a PC. I even built my<BR> crazy 30m QRSS beacon project with no PC or microcontroller, see<BR> <a href="></a> and<BR> <a href="></a> . I sit in front of a<BR> computer here in the office every day and somehow prefer that when I am at<BR> home I don't have to be attached to one.<BR> <BR> There's also the problem of the "homebrew only" law which rules my station.<BR> So far the only exception to it is my old 5MHz oscilloscope and my DVM. Some<BR> day I will get my Z80 computers up and running, and will be able to write<BR> some homebrew software for QRSS and PSK31 etc. <BR> <BR> 73 Hans G0UPL<BR> <a href="></a><BR> </tt> <br> <!-- |**|begin egp html banner|**| --> <table border=0 cellspacing=0 cellpadding=2> <tr bgcolor=#FFFFCC> <td align=center><font size="-1" color=#003399><b>Yahoo! Groups Sponsor</b></font></td> </tr> <tr bgcolor=#FFFFFF> <td align=center width=470><table border=0 cellpadding=0 cellspacing=0> <tr> <td align=center><font face=arial size=-2>ADVERTISEMENT</font><br><a href=" alt=""><img src=" alt="click here" width="300" height="250" border="0"></a></td></tr></table> </td> </tr> <tr><td><img alt="" width=1 height=1 src="></td></tr> </table> <!-- |**|end egp html banner|**| --> <!-- |**|begin egp html banner|**| --> <br> <tt><hr width="500"> <b>Yahoo! Groups Links</b><br> <ul> <li>To visit your group on the web, go to:<br><a href="></a><br> <li>To unsubscribe from this group, send an email to:<br><a href="mailto:BITX20-unsubscribe@...?subject=Unsubscribe">BITX20-unsubscribe@...</a><br> <li>Your use of Yahoo! Groups is subject to the <a href=">Yahoo! Terms of Service</a>. </ul> </tt> </br> <!-- |**|end egp html banner|**| --> </body></html> |
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BITX20 & BITX40
Hello to the BITX20 group (this is my first posting on this forum).
Farhan and myself have exchanged a couple of off-forum emails regarding mods to his excellent design. One interesting possibility is replacement of the LM-386 with a discrete component AF Amplifier. He said that he had not had the time to work up a schematic...so I have provided one (see attached .gif file). This can allow those without access to an LM-386 to build the unit. Also, my layout for the BITX20 uses 10.7 MHZ IF transformers salvaged from dead AM/FM radios ( I dislike winding toroids! ). My construction is a BITX40 (40 Meters) and requires 55 pf across the 10.7 IFs to resonate on 7.2 MHZ. These 10.7 IF transformers might be made to resonate on 20M if the internal capacitors were removed ( break them with a screwdriver point ) and a small variable ( 5-25pf ) used to bring them to resonance. 73's Arv - K7HKL |
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Re: More components
Hans Summers
开云体育Thanks
for the offer Bruce. Let's keep it in mind and see how it goes. Over half the
orders I had were from the UK, other than that US, Singapore and New Zealand. I
don't know if that's because I announced the list on the GQRP mailing list and
therefore more UK members joined, or if people were more inclined to buy locally
to keep postage costs down. Though at ?1.31 for postage for the packs to the US
and worldwide, it wasn't too bad.
?
Is
anyone a member of the US QRP-L list? I was but I couldn't handle the huge
volume of email so I unsubscribed. Perhaps someone who's a member might like to
announce the existence of this group, I'm sure the BITX20 would be of interest
to many on that list too.
?
73
Hans G0UPL
?
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Re: The PC as a lab instrument
Hans Summers
There's also the problem of the "homebrew only" law which We should not look askance at ALL "store-bought" technology.Don't get me wrong, I don't look askance at store-bought technology at all, nor have anything against it or any other aspect of amateur radio. Some people are committed QRP enthusiasts. I am mostly QRP but sometimes if condx are bad and I want to get through to a friend I turn the 80m CW TX up to its maximum 10W and I don't feel bad about it. There are so many aspects to amateur radio, each ham has his own areas of interest. Some hate CW, others operate it exclusively. To each his own! But my own passion is to homebrew everything. For really extreme homebrew, I hope one day to build a valve transmitter and matching receiver using components which are all constructed from household items or things that can be purchased from the hardware store. Every component: valves from baby food jars, capacitors from kitchen foil, etc etc. See for the capacitor I built, the only part so far. But that's just me - people who operate QRQ QRO black box contest stations don't bother me either. Unless it's a time such as once happened when I was in QSO with an SM6 on 80m, 2-way QRP CW and both about 339 or something rather marginal, and midnight GMT comes around and suddenly the whole place explodes with contest traffic and the SM6 and myself, well we both got practically vapourised by the volume of the audio in our receivers. Had to curse them a bit then ;-) 73 Hans G0UPL |
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Re: Components
Hans Summers
Mine arrived today too, many thanks Hans.No problem Mark. Sorry list members, Jack's earlier message on this subject and my reply got copied to the whole list when in fact it was intended to be offlist. Note that this list is configured such that the default reply address is the list itself rather than the original message sender. This means that by default replies go back to the list and if you want to reply only to the sender you have to copy and paste their address in. I prefer it this way, it generates more list traffic but I feel that often what is of interest to the original sender will usually be of interest to others, since we are in general all discussing the same rig. If there is any significant feeling about this and you want it set the other way, that can be done. 73 Hans G0UPL |
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Re: The PC as a lab instrument
Jim Strohm
On Jun 25, 2004, at 8:34 AM, Hans Summers wrote:
There's also the problem of the "homebrew only" law which rules my station.We should not look askance at ALL "store-bought" technology. Sometimes, recycled gear is nearly as satisfying as homebrewed, especially if it's recycled from the dust bin. A few months back, I was challenged to write a book describing how to build a transmitter and receiver starting from ZERO technology. So far, I've outlined sections on how to knap flint, how to make fire with sticks, and how to develop the most rudimentary tools for metallurgy. It appears that the shortest route to homebrewing a radio station essentially from dirt is to use gold for the wiring ... so far, I've found much more gold in the dust bin than lying about on the ground. Jim N6OTQ |
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Re: Components
Mark
Mine arrived today too, many thanks Hans.
--- In BITX20@..., Hans Summers <Hans.Summers@t...> wrote: morning. My very best wishes to your wife, and good luck with the project whenyou have time. Nearly 60 years of marriage is wonderful. I am 33, marriedfor 8 years so some catching up to do! We have a 15 month old daughter whotakes most of my time.from three different suppliers. The LM386 was from Farnell because Iwasn't sure that the Rapid Electronics version was the correct LM386N-1version. All components have been counted out and shipped, UK orders by firstclass post (should arrive tomorrow morning) and international orders viaairmail. could be because they are so cheap that counting them precisely costs Rapidmore than giving a few extra. Or it could be that I messed up my owncounting, as the whole process was rather tedious and I have been having a verystressful day. If anyone is missing any then let me know, or needs someextra spares. things to say, but am too busy to do it today so pls QRX< 76/D=gr oups/S=1705063108:HM/EXP=1088241546/A=2128215/R=0/SIG=10se96mf6/*http ://comp anion.yahoo.com> click hereM=295196.4901138.6071305.3001176/D=groups/S= :HM/A=2128215/rand=941782905>Service <> . |
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Re: The PC as a lab instrument
Hans Summers
does anybody have more stories about using PCs in theFarhan, I don't have a PC at home at all, except an old laptop my XYL uses for internet access. I prefer to do everything without a PC. I even built my crazy 30m QRSS beacon project with no PC or microcontroller, see and . I sit in front of a computer here in the office every day and somehow prefer that when I am at home I don't have to be attached to one. There's also the problem of the "homebrew only" law which rules my station. So far the only exception to it is my old 5MHz oscilloscope and my DVM. Some day I will get my Z80 computers up and running, and will be able to write some homebrew software for QRSS and PSK31 etc. 73 Hans G0UPL |
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Re: Components
Hans Summers
开云体育?
No
problems Jack, thanks for the cheque which was received this morning. My very
best wishes to your wife, and good luck with the project when you have time.
Nearly 60 years of marriage is wonderful. I am 33, married for 8 years so some
catching up to do! We have a 15 month old daughter who takes most of my
time.
?
73 de
Hans G0UPL
|
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Re: Components
William Ford
开云体育Component parcel received today.many thanks
Jack
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Components
Hans Summers
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 |
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Re: The PC as a lab instrument
Jim Strohm
On Jun 24, 2004, at 5:37 AM, Ashhar Farhan wrote:
the PC is a powerful a DSP as you can hope to own. the problem is in"Back in the day" ... A decade or more ago, it was trivial to get ISA-bus prototype boards to wire up new gadgets like A/D converters. With the limited bandwidth of ISA and the low frequency of consumer-affordable A/D chips, board layout was not an issue. In fact, some of us were building MIDI interfaces/audio digitizers for Macintosh out of a single A/D chip and a couple of connectors. And it's trivial to use the PC printer port (LPTx) as a data interface. A PCI breadboard is a lot harder to come by nowadays, and it's not even something that an enterprising hobbyist could etch up himself. However, PCI has the bandwidth and the newest consumer-grade A/D chips have sampling rates that were almost unheard of just 5 years ago. But it would be (relatively) simple to design and build a PCI A/D board. The biggest challenge would be to equalize the signal traces from the A/D chip to the PCI connector. Assuming one could etch a PCI connector, this could be done at home. An easier interface would be USB 2.0 or FireWire (IEEE 1394). Most PCs built since 1999 have USB 1.0 or higher; some PCs since 2002 have FireWire (Macs introduced since 1998 or so all have FireWire). The significant advantage to USB is that most consumer OSes besides Mac OS X have drivers for most USB devices built in, so there's a good chance that for any given USB interface chip, the OS will recognize its data stream and be able to provide it _somewhere_. This isn't as easy to implement as an LPTx scheme under DOS, but there are a number of simple programming environments for Windows such as Visual BASIC (yecch) or National Instruments' LabView (hurrah!) that make data acquisition and manipulation easy to set up. And Linux has at least as many drivers, plus the ability to drop to a command-line interface, which makes accessing machine-level functions a whole lot easier than under an MS OS, now that DOS has been effectively buried under Wind0ze. Theoretically, all you need for data capture is -- suitable conditioning and buffering circuitry to deliver your analog signal to your A/D converter, a buffer/interface to your bus, and a suitable bus connector. In the case of USB and FireWire, which are serial interfaces, you need as part of the bus buffer/interface from the A/D -- a data serializer. This would be any scheme that would take the parallel-bus output from the A/D and convert it to a serial stream compatible with USB or FireWire. Some newer A/Ds now have serial outputs, so the interface would be as simple as doing level conditioning and perhaps some timing adjustment. The stuff's out there -- try TI or National Semiconductor. Both companies have reasonable sample policies if you know how to ask. It's harder to design the board than it is to get free parts. (N.B. -- Some parts are US export-restricted, even though they're made or assembled outside the US.) And -- if you have lots of money to throw at the problem, National Instruments has already solved it. Reverse-engineering their hardware at lower performance levels should be within the scope of most savvy home builders -- their catalog offers ample design solutions that show you what CAN be done. After that, it's just a matter of software. Or, if your signal of interest is 20 kHz or narrower, you merely need to convert it to baseband and feed it to your sound card. There's a lot of amateur DSP software available. And again, if you have a lot of money to throw at the problem, there's also MatLab for developing your own DSP software. And -- the modulation characteristics and core DSP source routines to match those characteristics are freely available on the Internet if you are a diligent searcher. Programming in C is an advantage here. If you choose to explore this avenue, you'll soon find that having a stereo input sound card opens up a huge new world of capabilities. Most of them beyond the scope of HF SSB, CW, or PSK31. Jim N6OTQ |
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The PC as a lab instrument
Ashhar Farhan
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 |
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Re: BITX20, 40 or 75 M versions? (fwd)
Hans Summers
Very interesting ideas.
On the subject of VFO's, one addition I am going to make at some point on my rig is a Huff Puff stabiliser. You can see my version, and read much of what has been written about the Huff Puff stabiliser technique since it was developed by PA0SDB in 1973, visit my page . A year or two ago I spent a day in the Science Museum / Imperial College library in London (I am an ex-IC student in fact!). I had all the RSGB RadCom's bought up from the archives on a trolley, and went through and photocopied all the original articles and follow up. RSGB have given me permission to reproduce them on my website. All that remains is to find the time to scan them etc. In any case, these early articles are of historical interest but in practice you will want to read the more recent articles if you are intending to build a stabiliser. Again, the components are simple logic IC's and should be reasonably easy to source. On the BITX20@..., you will see thatMy counter uses one 74HC4060 and one 74HC4040, not two 74HC4040. The 74HC4060 is used for the timebase because of its onboard crystal oscillator. The URL is: . All these components should be easily obtainable anywhere. Here in the UK the component cost is about ?2. The old CMOS 4060 and 4040 should work just as well, but the maximum count frequency will be lower. At the BITX20's VFO frequency, old CMOS implementation would be fine. I am in frequent correspondence with Onno PA2OHH who designed the original 3-chip version of the counter , which inspired my modified and even simpler version. We have been sharing ideas on the counters, a nice collaboration. He is currently performing some very interesting experiments with a 74HC390 dual decade counter instead of the 74HC4040. With the 74HC4040 the LED's indicate 64, 32, 16, 8, 4, 2, 1, 0.5KHz. You get good practice at reading binary. With a 74HC390 it is easy to obtain a different sequence: 80, 40, 20, 10 and 8, 4, 2, 1. The LED's can be arranged in two columns of 4, one to indicate 10's of KHz and one to indicate KHz. The mental arithmetic is faster and easier, but the resolution of the counter worsens from 0.5KHz to 1KHz. Note though that the intensity of the least significant LED acts as a kind of analogue frequency indication, which makes it possible to estimate the frequency to better the resolution by a factor of 2. For example in my design if the LED is half brightness, it is possible to estimate that the frequency being measured is xx,xxx,250 Hz. Another advantage of the 74HC390 version is that it does not require the 100-count detect gate (3 diodes + resistor), nor OR'ing this 100-reset signal onto the reset pin (2 diodes + resistor). Thereby eliminating a further 7 components from the design (5 diodes, 2 resistors). I have installed my Mk1 simple 2-chip frequency counter in the front panel of my BITX20 and marked the tuning dial 14.0, 14.1, 14.2, 14.3 and 14.35. My readout is now accurate using the dial for 100KHz accuracy and the counter to read 0 to 99.5KHz. I have not yet debugged my rig so I can't yet be sure how much effect it has on the rig. There is an on/off switch for the counter so that it could be used to read the frequency then disabled. At the present time I hear hiss in my headphones and a faint tone at about 1KHz (the frequency of the pulse-width-modulated LED's) when the volume is at full. But the counter has no shielding yet. I will report further results as and when I have time to progress the project. Another interesting observation: In my 80/40m polyphase receiver I have installed my 8-digit frequency counter as well as a 24-hour clock . The counter and clock are both built in screened boxes made from PCB stock, and they each have an inductor in series with their power supply. Both of them pulse-width modulate the LED displays to eliminate LED series resistor. Duty cycle is 1 in 6 if I remember correctly. Both the clock and the counter have their own on/off switches because I was worried about digital noise getting into the receiver. But during extensive use I have never found it necessary to switch off the counter or the clock, since they appear to contribute nothing at all to the receiver noise floor apart from possibly the occasional and very faint birdie. But even this I have been unable to conclusively prove to myself. Use of low current LED's in the 2-chip simple frequency counter and lower duty cycle (I use 1 : 64) helps noise, because it means the power supply smoothing is much more effective (all other things being equal). I am currently trying (with only limited success) to source a 16 or 32KHz crystal (yes KHz not MHz) to replace the 4.096MHz crystal in the counter, which I hope will reduce the power consumption even more. For the fun of it I am going to build a miniature version using one of the tiny 6mm long cylindrical 32KHz crystals and surface-mount 74HC4060 and 74HC390. Surface-mount, but "ugly" not on a PCB. I hope it will be about the size of a postage stamp, and a few mm thick, with current consumption < 1.5mA. Rather an extreme project and not recommended. But I do definitely recommend the counter design, use more real-world size components! 73 Hans G0UPL |
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Re: BITX20, 40 or 75 M versions? (fwd)
Ashhar Farhan
---------- 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: (1) One could just change the frequency of the VFO and front-endI 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. (2) Use of an FET for the VFO as you mentioned in the web page isthis 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. (3) A cheap microprocessor employed as a frequency counter (withOn 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. (4) Adding a dual op-amp to the transmit audio section could providethe 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. (5a) Conversion of the unit to include CW capability looks fairlyjust 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. (5b) Adding CW sidetone might involve leaving the receive audiolet 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. (6) Adding VOX capability could be accomplished by sending some ofi 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. (7) If one added CW capability and wanted QSK there are severalquite 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. A BITX for 75 M also seems logical for US hams because a significant amountYes, 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. Since I also play around on the US LF band (the Lowfers group) the thought<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 again for your reply and assistance. Your contribution of the BITXthanks 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 Thanks again & 73's_________________________________________________________________ Pay Cash on delivery on lakhs of products. Only on Baazee.com |
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Re: More components
Bruce Raymond
开云体育I
realize that I'm late getting into the group.? Jameco ()
has 10
MHz, 50 ppm crystals for $0.69/10, $0.59/100+, $0.49/1000.? I
think
that
corresponds to 0,38 L/10, 0,32 L/100, and 0,27 L/1000 (I don't have
a
symbol
for British pounds on my keyboard).
?
Hans,
you're going beyond the line of duty to take on the ordering task.?
If
there's some assistance you need from the US side of the pond I'm willing
to
help.
?
73,
Bruce
Raymond/ND8I
?
?
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