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Re: BITX15 QSO got 1000Km
Arv Evans
EA7ARX
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Congratulations on your license upgrade, and on the recent DX with the BITX15/20 transceiver. I wonder what the distance per watt record might be for a BITX design? Is your 500 Km per watt the best accomplishment thus far? It might be interesting to hear from others regarding their DX accomplishments with BITX, and if there have been any BITX-to-BITX DX contacts yet? Arv K7HKL _._ On Sunday 31 July 2005 10:28 am, vdberghak wrote:
--- In BITX20@..., "eb7hpm" <msraya@t...> wrote: |
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Re: BITX15 QSO got 1000Km
Concratulations with you extended licence and the experience of working
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on HF with the BITX. May be we will meet, Chris. PA3CRX --- In BITX20@..., "eb7hpm" <msraya@t...> wrote:
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Re: Modulator mod and dual conversion BITX
ajparent1
Hello,
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Turning the moddulator around should not negatively impact operation. My proto(20M) and testing the second (6m) show the revised is prefered for many reasons. The high noise suggests several things. You may have RF getting into the audio amplifier or one or more stages are oscillating when they should not. As to 6 meters, I've done enough building of transceivers for that band that dual conversion is viable with care. The reason I say with care is that more stages and more oscillators require good shielding more undesired signals are likely. Also more stages means more gain and that increses the possibility of unwanted oscillation. I am working on 6M and to date I have the entire audio, and IF section working and tested. I will use doubly balanced mixer (mixer with two transformers). Local oscillator will use PLL of my design. Another approach for those not wishing to build PLL is to take a crystal osc such as 35mhz and mix that with VFO of 5mhz to get 40mhz at good stability. In any case after 4 prior VHF radios the local osciallator system must be shielded and well filtered to keep undesired signals away from the rest of the reciever. Basic lineup for the 6m radio is 9.6mhz IF and filter (have those crystals). Q1 and Q13 transistors are 2n3866 (good VHF device) and the power amplifier chain willl not use IRF fet. I plan to use a VHF power transistors 2SC1970 and 2SC1971. Allison KB1GMX --- In BITX20@..., "eb7hpm" <msraya@t...> wrote:
Hello, BITXs!! |
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Re: BITX15 QSO got 1000Km
Ron Brink
Congratulations with those results in 15m band !!
73 de Ron
PA2RF
 eb7hpm wrote:
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BITX15 QSO got 1000Km
Yesterday Afternoon I make contact in 21.190 with the Canary Island
Station EC8AUZ, from the south of Spain Huelva, it make more than 1000Km!! Signal reply was 55. I am very happy. Mi BITX(15+20) with PLL outputs only 2W (I have IRF520 instead IRF510) in a dipole antenna in a building 30 m over ground. The propagation helped a lot. P.D: I am in error in my last post. The oscilator is 22MHz for a second FI of 10MHz. Greetings EA7ARX, ex EB7HPM/EC7ALV |
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Modulator mod and dual conversion BITX
Hello, BITXs!!
I'm sorry but the modification by Allison doesn't work in my dual band BITX (15 and 20meters). It makes great white noise in the receiver. Without the modification the noise is little and the band sound is good. After the modification the white noise is loud and the band sound is muffled. I test also to add another coil to the ring diodes mixer. But this modification don't make diference aparently. The band sound and sensibility remain unchanged. I am working in an dual conversion BITX, after the "disaster" of 32MHz FI due to the bidirectional amplifier feedback configuration I work in a dual conversion. First FI 32MHz, second FI 10MHz. The mixers are identical ring diodes based, the oscilator is 12MHz cheap and easy to source. I want to mantain the bidirectional architecture. I will use a bidirectional amplifier made up of dual gate mosfets and resonating coils for 32MHz. I will post the result of works and schematic. I will like to make VHF with this configuration. Greetings I got my all band ticket!! EA7ARX, ex EB7HPM/EC7ALV |
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Re: modulator mod
ajparent1
Good old PSP was the tool.
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Finally got DIA to crack using gunzip with no shortage of complaints, installed it and it crashed hard after looging a long list of errors. Apprently it has a lot of dependancies on MS products. The system here is NT4 with SP6A but NO MS loaded products including OE and IE. Its' a security thing. I'll hunt around for a decent too to eiter convert the DXF files from cadd6 or maybe a different cadd tool that really works for schemtaic capture. I have more schematics comming but I need a better tool for the PC environment. Allison KB1GMX --- In BITX20@..., "Arvid Evans" <arvevans@e...> wrote:
Allison |
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Re: modulator mod
Arvid Evans
Allison
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Thanks for posting the schematic of your BITX modulator modification. With the different languages and varying skill levels involved in the BITX forum, sometimes a picture or schematic is necessary for all to understand the more technical aspects of some design & construction activities. Arv K7HKL _._ - -- In BITX20@..., "ajparent1" <kb1gmx@a...> wrote:
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Re: modulator mod
ajparent1
Dia was a dud, could not get a file that would unzip from any of the
hosts. The other two are really poor for schematic capture. I found the libraries more suited to digital design. I'll keep Eagle around for digital stuff. For analog that has lots of passives like trifilar transformers, forget it. I'd forgotten how horrid PC based schematic capture tools are. Last one I used a lot was CADD6 (G-cadd) I have that but the files are not easily viewed without cadd or autocadd. Microcadd was easier to use but didn't run well under NT but is decent on a simple dos machine wich also limits portability as you need microcadd to view files (it's a really small program). Much too much time spent on this already. I may just take paintshop and tweek and existing image. Allison KB1GMX --- In BITX20@..., Arv Evans <arvevans@e...> wrote: Allisonit to make .png (Portable Network Graphics) output. You have to save acopy in native .dia format first, then "export" the drawing and set the filetype to ".png" or ".jpg" as desired.some Dia built schematics at BITX20/FILES/K7HKL/...NT-4.x available the textual> > I'd built> > > description. wiper to> > > > was the presence of audio getting into the IF amp on solution was> > attenuator> > > > staring me in the face and also eliminates the PI feed noise to use Service.
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Re: modulator mod
Arv Evans
Allison
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All can produce posting quality files. I usually use "Dia" and set it to make .png (Portable Network Graphics) output. You have to save a copy in native .dia format first, then "export" the drawing and set the file type to ".png" or ".jpg" as desired. There are examples of Dia produced schematics on my web sites <www.k7hkl.webhop.net> and <www.qrp.webhop.net>. There are also some Dia built schematics at BITX20/FILES/K7HKL/... Arv _._ On Friday 29 July 2005 09:36 am, ajparent1 wrote:
Ok, Looks good which one produced the most usable output |
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Re: modulator mod
ajparent1
Ok, Looks good which one produced the most usable output
for posting? Afterall I can post gerber files and vectorlists but they are hardly easily seen. Allison KB1GMX --- In BITX20@..., Arv Evans <arvevans@e...> wrote: Allisoncan be obtained via the following URLs:windows (and for Linux) that would be suitable to use in drawing a partialschematic for the changes you have made in the BITX design. Of these three,EagleCAD from CadSoft is probably the closest to a professional CAD program,but the other two are certainly adequate and may be easier to learn.These are just the ones that I know about and use frequently.changes and transmit and IF adding an> > noise in to the audio on recieve. I'd gone the route of pleasing and> > 47uh RF choke from the intersection of the balance pot wiper to the sort> > also elimiates a number of components. As an engineer I'm as well.> > that looks at a design and says "what if..?". The solution was the IF> > The change is to turn the balanced modulator around and feed potentiometer> > in on the transformer and RF (bfo) in at the balance resistors> > via the .1uf capacitor. This eliminated the need for the 3 and more> > and the rf choke. I noted cleaner modulation, less RX noise this> > gain available in both RX and TX. Service.> > mod in the 6M version.
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Re: modulator mod
Arv Evans
Allison
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Free Schematic CAD software that should run on your Microsoft NT-4.x can be obtained via the following URLs: All of these sites provide freeware schematic drawing software for windows (and for Linux) that would be suitable to use in drawing a partial schematic for the changes you have made in the BITX design. Of these three, EagleCAD from CadSoft is probably the closest to a professional CAD program, but the other two are certainly adequate and may be easier to learn. And...Yes, there are other schematic drawing programs available. These are just the ones that I know about and use frequently. Arv K7HKL _._ On Thursday 28 July 2005 09:52 pm, ajparent1 wrote:
The best I can do would be jpeg photo of hand drawn paper page. |
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Re: modulator mod
ajparent1
The best I can do would be jpeg photo of hand drawn paper page.
Even that takes some effort as only one PC supports USB and this is not that one. All my schematic capture cadd stuff runs on VAX/VMS and is generally incompatable with PCs. I may add the change is not very big. I just turned the circuit around to reverse the LO and IF ports. The transformer T3 feed IF and Q9 feeds the balance pot through the .1uF cap. If there is a prefered PC schematic capture I may investigate but it must run under NT4 on a slow machine as this box is generally accessable. Allison KB1GMX --- In BITX20@..., Arv Evans <arvevans@e...> wrote: Allisonstore it in the FILES section of this forum? That way it will be availablefor others who might not understand all that was changed from just the textualground which helped greatly. However, it always bothered me. |
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Re: modulator mod
Arv Evans
Allison
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Would it be possible for you do a quick schematic of the changes and store it in the FILES section of this forum? That way it will be available for others who might not understand all that was changed from just the textual description. Thanks, Arv K7HKL _._ On Thursday 28 July 2005 09:20 pm, ajparent1 wrote:
One of the things I didn't like in the 20m proto BITX I'd built |
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modulator mod
ajparent1
One of the things I didn't like in the 20m proto BITX I'd built
was the presence of audio getting into the IF amp on transmit and IF noise in to the audio on recieve. I'd gone the route of adding an 47uh RF choke from the intersection of the balance pot wiper to ground which helped greatly. However, it always bothered me. So I opened it up and tried a design change that I find pleasing and also elimiates a number of components. As an engineer I'm the sort that looks at a design and says "what if..?". The solution was staring me in the face and also eliminates the PI attenuator as well. The change is to turn the balanced modulator around and feed the IF in on the transformer and RF (bfo) in at the balance potentiometer via the .1uf capacitor. This eliminated the need for the 3 resistors and the rf choke. I noted cleaner modulation, less RX noise and more gain available in both RX and TX. Might as well add this mod to the collection. I plan to use this mod in the 6M version. Allison KB1GMX |
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Re: Pre driver output
ajparent1
Hi,
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2mw is very low from the driver. Mine I see nearly 1mw at the output of the bandpass filter (L1, L1,L3). The driver stage brings that up to near 300mW on mine. I don't use the IRF510 as the output is more than sufficient to drive a TenTec 1208 transverter at 100mW, 1mW however was not adaquate. Driver transistor used on mine was 2N2219A with bifilar transformer wound on a 2 hole core of -43 material to match 50 ohms. Without the 5db output attenuator it measures as 3.8V rms across 50 ohms which is actually 288.8mW using a HP rf voltmeter. Thats close enough to 300mW. If you are using a trifilar transformer on the driver and measure the power to the IRF then the driving impedence is around 10-12 ohms and a 50ohm power meter will be inaccurate. Even then I'd expect to see about 1.7-1.9V of rf at that point. In any case 300mV is invalid. The gate of IRF needs to be driven with several volts of RF to develop expected power without instability. On mine the Q14 (predriver) device is 2N2222A and driver is 2N2219A both have FT ratings of 350mhz which is adaquate to get good gain at 14mhz. Measurements at the output of the filter (at 50ohms) is .9-1mw. After Q14 I get 40mW. Adding the driver brings that to 300mW. I used ferrite loaded transformers at T1, t2 and T3 as well as collector of 2n2219A. Also added a choke coil (DC return) at RF mixer (100uh molded type) and at modulator. Transistors used are Q1,Q13,Q7 are 2n2222A, Q2,3,12,11,9,8,10 are all 2n3904. This version uses a different VFO (Hartly with fet buffer). All circuits are bypssed with more than shown is schemtic and some sections are shielded (modulator and bfo). Construction is dead bug (ugly on ground plane OF unetched PCB). A newer version is being built that will use a PLL to provide LO and the output will be for 6m using 9.6mhz filter, 40mhz LO and I may try commercial DBM (anzac MD108) for both modulator and mixer. Since this one is to be small power will be limited to around 3-5W and use a RF transistor 2sc1971 for the final. More information than asked for but, measurements are how I know a circuit does indeed perform as expected. Allison --- In BITX20@..., "vdberghak" <vdberghak@z...> wrote:
Hi Milarepa, |
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Re: Pre driver output
Hi Milarepa,
based on my measurements, it is only a few mw, so the oposite of what Allison measured. I searched for you in the older postings (I have often the feeling that older messages are not red) and you can find my answer in message 375 (containing a mistake) and 387. Good luck, Chris. --- In BITX20@..., "ajparent1" <kb1gmx@a...> wrote: Based on my proto 300mW is correct. If there were 300mV the powerof pre driver should be about 300 mWatts, |
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Re: Pre driver output
ajparent1
Based on my proto 300mW is correct. If there were 300mV the power
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would be about 2mW which is way to little. Allison KB1GMX --- In BITX20@..., "MILAREPA" <MILAREPA@T...> wrote:
Dear forum, |
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BITX PA
Folks
I am working from the (c)2004 circuit on Ashar's web page and have very low output from PA. I am using cheap general purpose transistors (ME4003) and changed pre-driver for 2N2222. Better but still only about 1W out. I have used a very similar PA in the TCF transceiver by VK3XU and it works fine. That is on 40m though. I have read through previous postings and applied mods by Chris, PA3CRX. I now have full 6W output. Well done Chris! I see Ashar has adopted the trifilar transformer and the extra 200pF capacitor in his simple dual band transceiver design. Is there a definitive revision, or is it a case of 'suck it and see'? 73, Steve, G0FUW ___________________________________________________________ Book yourself something to look forward to in 2005. Cheap flights - Bargain holidays - |
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