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Re: Small mistake
Hi,
responding to the messages below: - Ron, in the Netherlands, I heard also several stations with very strong signals, form Russia but also from the States. However, the 6 watt I have on 17 mtr is a bit little in combination with my sloping dipole. Stations in (for example) Bulgaria are answering: 'only outside Europe'.... - Rahul, I use a small 8 Ohm speaker (removed from an old transistor radio). When I connect the antenna, a loud noise is comming out of the speaker. When I receive a weak station, it is just above the noise but at the moment a strong station enters, I really have to turn down the volume potmeter immidiatly! In fact, the volume is never on its maximum. By the way, I use the real, original BC107, metal can ;-) For the stage before the LM386 I use a BC109. Best regards, Chris. Interesting are you using a speaker or heaphone. Secondly whattransistors are you usingBC547s or 2n3904s 73antenna connected. Some signals clear enough to decode...till now I have only used half or quarter lambda ant's..) |
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Re: mixers
Rahul Srivastava
Hi!
?
On issue of torroids if you cant buy them salvage them. A common source is defunct CFL lamps. Half bridge drivers use a torroid based transformer, I am sure Argentina must be seeing plenty of the cheap Chinese CFLs.
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Balun cores are fairly common you can salvage from old TV tuners and another source? is cable TV splitter and tap offs, get a few from your local cablewallah.
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Yet another solution, since mixer do not involve high power, one can easily fashion out of ferrite beads. The site of Intio OZL ham from JF land gives a very clear picture how to make a DBM based on beads.
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These two links I feel can provide simple alternatives given non availbility of recommended ferrites.
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Lately I made a new layout Ver3 with shunt feedback type IF amp for Q3 and doubly balanced mixer. The layout is yet to be tested but anyway I will soon post it for your analysis.
?
73
?
Rahul VU3WJM
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streamerhart wrote:
Send instant messages to your online friends http://uk.messenger.yahoo.com |
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Re: mixers
HI HAM PALS :)
IN FIRST PLACE THANKS MR EVANS FOR YOUR REPLY . SOMETIMES IS VERY IMPORTANT TO THE PEOPLE WHO LIVE OUTSIDE USA OR EUROPE TO FIND ALTERNATIVES TO TOROIDS AND OTHER ELECTRONICS COMPONENTS NOT SO COMMON HERE AL LEAST IN ARGENTINA AS ONE TIME SAYS ONE SALES PERSON IN A LOCAL ELECTRONICS COMPONENTS SHOP WHEN i ASK ABOUT COIL FORMS AND TOROIDS '' RADIO AMATEURS ARE NOT BUSSINES '' JULIUS WHAT ABOUT IN ENDING THE MIXER WHIT A DIPLEXER AND TRY A DOUBLE BALANCED ONE IN THIS SITE YOU CAN FIND SOME DATA WITHOUT HEAVY MATHEMATICS SEE THE DIPLEXER PAGES WHIT A FEEDBAK OF W7ZOI --- In BITX20@..., "Wijaya, Julius" <ubberalles@y...> wrote: speaking about mixers, how to make it good, i got a whistlingsound, farhans said its about bad post mixer signal. any tips..cm) Turns usedinside diameter PVC water pipe for the 10 MHz trifilar cores. made thewere the same as Farhan specified in his original design. theretransformer for diode mixer in no ferrite toroidal core I thin winding inare a picture of this in the photo section .- this duea pvc water pipe and it work I can follow experimenting with Service.to a lack of instrumental .-
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Re: mixers
Wijaya, Julius
speaking about mixers, how to make it good, i got a whistling sound, farhans said its about bad post mixer signal.
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any tips.. rgds julius * REPLY SEPARATOR * On 3/28/2005 at 10:44 PM Arv Evans wrote:
Fernando |
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Re: mixers
Arv Evans
Fernando
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I used a 1/4 inch (about 6mm) wide slice of 1/2 inch (about 1.25 cm) inside diameter PVC water pipe for the 10 MHz trifilar cores. Turns used were the same as Farhan specified in his original design. The number of turns does not seem to be very critical. Arv K7HKL On Mon, 28 Mar 2005 21:47:40 -0000, streamerhart <fernandocasari@...> wrote:
--
Expore all the Ideas...Exploit the good ones! |
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mixers
Dear all:
I slow work in a 80 mts bitx20 and i have a dude some of you made the transformer for diode mixer in no ferrite toroidal core I thin there are a picture of this in the photo section .- Is this posible one time I made a diode mixer with trifilar winding in a pvc water pipe and it work I can follow experimenting with this due to a lack of instrumental .- any help on this topic is very appreciate. Best rgds Fernando LW5DNC Bs.As Argentina |
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Re: Small mistake
Rahul Srivastava
Hi!
?
Interesting are you using a speaker or heaphone. Secondly what transistors are you usingBC547s or 2n3904s
73
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Rahul VU3WJM
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Ron wrote:
Do you Yahoo!? |
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Small mistake
Ron
Hi members of the bitx20-homebrew-fellowship !
Found some hours to spent on the BITX17 this Easterweekend and discovered a major mistake I made. I had connected a 2k2 resistor of Q13 between e and c instead of between b and c. Stupid me...I corrected this and now i have fb quality SSB on Q14 with a signal level of 200mV over 47 ohms. That should be fine. This explains the strange things I saw, like the impossiblity to adjust the level of the carrier wave component in the ssb signal with the variable resistor. And the strong 2nd harmonic of the VFO (26.2 MHz). I did not even have a proper ssb signal on 18 MHz ! I included a low-pass filter (cut-off freq at about 9 MHz) after the VFO to kill the odd and even harmonics Now I have to hook-up the MOSFET and its surrounding components and see if i can get the rig on-air. Bye the way, RX signals on 17m were fine this afternoon, heard ssb voice, rtty, psk31 and cw. With a one-lambda (17 m) long-wire antenna connected. Some signals clear enough to decode... Does anybody have experience with one wave-length antennas (up till now I have only used half or quarter lambda ant's..) Bye bye and have a good Easter weekend (for what's left) Ron PA2RF |
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DDS as LO
MILAREPA
Dear forum,
I have a DDS ( PA2OHH's ) and want to try this as an LO of my BITX. for reason I don't need to add a frequency counter, and he PA2OHH is succeed used DDS as 5 to 5.5 MHz VFO (for an old TS520,stability is good enough now for PSK31) for schematic of DDS please see : But I don't know where to connect this DDS to my BITX point, How about before coupling capacitor 0.1 of Q7 ? please advice. I have measured my DDS output and the specification is : 4.1 ~ 5.6 MHz = 22 mW 5.5 ~ 7.8 MHz = 16 mW 7.4 ~ 10.7 MHz = 14 mW 10.6 ~ 15.2 MHz = 12 mW 14.5 ~ 20.3 MHz = 34 mW 20 ~ 29 MHz = 6 mW Thanks. |
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Re: faucet washers forms
Arv Evans
Hi
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Due to similar observations with my original BITX20, I used 1/4 inch wide slices of 1/2 inch ID PVC pipe as the formers for my BITX40. The results caused me to recently replace black plastic faucet washer formers on my BITX20 with some white (apparently nylon) ones from Home Depot Stores (this is not an endorsement of Home Depot faucet washers...their store is simply closer to my home than is the Lowes store). In one of Farhan's recent emails he mentioned using a "Polo Candy" (much like our "Life Savers" hard candy in the US) as the former for a VFO inductor. These might also be an alternative to questionable tap washer material. If you have access to a wood turning lathe it would be possible to turn small wooden cores for your BITX inductors. One could even simply whittle them from scrap wood if a lathe were not abvailable. Arv _._ On Sat, 26 Mar 2005 03:18:40 -0000, pgdaulton <k5wms@...> wrote:
--
Expore all the Ideas...Exploit the good ones! |
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faucet washers forms
pgdaulton
It would seem not all faucet washers are created equal.
After completing my bitx20 main board I was disappointed with the rec gain. I upped the audio gain by increasing the feedback cap on the lm386 to 10uf. Noticable improvement but still seemed to be loosing sensitivity in frontend. The washers I used were a black rubbery plastic 1/2 in od purchased at Lowes (home supply retailer in us). I suppected these might be lossy so I put one in a microwave oven. At 20 seconds the washer was too hot to handle. I wound new coils on 1/4 in ferrite (red) cores. the faucet washers measured 2uh with a q of 70 on my heathkit q-meter. 18 turns #30 awg on Ft37-2 form measured 2uh with a q of 140. Gain picked up about 3 s units. I can now hear signals on a speaker. I plan on replacing the 2n2222's with 2n3904's as suggested. minimum discernable signal is less than 1 microvolt but I want another 10 to 15 db gain overall. tuning on trimmers is very sharp now. The nylon washers Farhan used are not available in my area.What I used was a poor substitute. Thanks to those who sent suggestions. |
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Re: Band Pass filter adjustment
I used a dip meter to roughly adjust the individual LC's to the
correct frequency. Then I connected them together and peaked them. May be adding the capacitor on one coil, did change also the resonance frequency of the other resulting in zero throughput? I would suggest to listen to a signel in the band and then tune the trimmers to maximum sound. Good luck, Chris. --- In BITX20@..., "David WardenDurkee" <dwarden2@c...> wrote:
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Band Pass filter adjustment
David WardenDurkee
I am adjusting the receive BPF using a sine wave generator and
oscilloscope. The first of the three sections peaks at about 14.2 Mhz, but the second peaks at 16 Mhz. I tried to add 12 pF additional capacitance to lower the resonant frequency, but the sine wave disappears completely. Is my problem mutual inductance canceling the 14.2 Mhz signal? Any ideas or help is appreciated. Thanks, Dave |
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Re: LF BITX
Rahul Srivastava
Dear Arv and friends,
?
Hi!
?
Here in keeping with common availablity I went ahead with BITX20 version using off shelf components. I used BC547s available, probably Chinese varients. The performance was not upto the mark. Only with beam antennas could we hear something. Hoping this as one off case? made 3 more units and all gave similar results, Now it is confirmed the stock components need some careful selection. All on BITX V2 PCB and one on copper clad as per Farhans by VU2DAD Dev an?80 yr OM.?
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Ultimately I made few changes cause 3 other units were made by few of my friends least not their efforts go waste. I realised that frontend gain was optimum to overcome losses so I worked on adding some gain in IF stage.
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Q3 instead of single? device?added one more and?made it a shunt feedback type amp achieving slightly higher gain and still keeping with RC amp topology. Surprisingly similar approach has been followed in Norcal 20 design this makes things nice and good. A 220E resistor in series at input helps in maintaining the required impedance by brute force method.
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?Replacing the Rf preamp transistor by 2SC2570A a cheap cable TV amp transistor improved the noise figure. BFR91-96 could be slightly expensive substitute.
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?The coils are commercial 10.7Mhz?FM?IF?tuned to 14 using 33-39pf caps (plus strays),
?original at 2.7uH they requred abt 68pf for 10.7mhz and 47pf for 14 as per calculations.
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In audio stage I have seen many homebrew design using LM386 chip but of all the ones I made?,?were running at full gain / open Vol most of the time (probably at max distortion level). I also feel the OP coupling capacitor is bit low at 50uF a 220 or 470 would be?slightly better choice.
?Picking up from another design and incorporated into one txcvr that I am making I find much better performance if we follow the PD into 3 pole RC network using 1k and .01 caps (omit preamp transistor).
?For preamp now we use the LM386 as used in Elecraft K1 with the anti hiss mod of ,01 and 10K resistor in series from pin?5 to 8.? I follow it up with a TDA2003 amp chip and?now whole? rig?rocks.?
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I am working on new board my BITXV3 PCB this also has link coupled 10MM coils and provision for doubly balanced mixer ie another balun added.
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2N3904 I feel would be better choice for transistors mainly there are less chances off getting it sub standard. Secondly it has a much lower capacitance in comparision to BC547. All in all this has been a good learning experience and some brain?excersicing project rather than just component stuffing kit projects off late.
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Thanks to all for support.
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73
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Rahul VU3WJM
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Arv Evans wrote: Paul
Do you Yahoo!? Yahoo! Small Business - |
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Re: LF BITX
See also in the Files directory 'modifications', 'clear LF' to
improve the loop gain of the LM386. The capacitor should be made 10uF. My BITX17 is not generating a loud noise but when a station is heard it is a lot of volume. Chris. at lowI have pc board from far circuits for bitx. Have rec working but I haventvolume, Had to repair signal gen also had much time to evaluate attenuation |
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Re: LF BITX
Arv Evans
Paul
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On my BITX20, and the BITX40, I used an AF design that is different from the LM386 that Farhan specified. There are some schematics of this in the BITX20 Group files section under K7HKL. My AF section uses two NPN's (2N2222)as AF amps, driving an NPN/PNP pair of power transistors for about 4 watts peak AF output. With this the AF level is more than adequate. There have been cases of low receive volume in BITX20 units being traced to RF transistors that showed less than optimum gain at 10 & 14 MHz. That was the case on my first BITX20 unit. I found that supposedly good 2N2222's from a surplus source were much inferior to some 2N3904's that I used to replace them. In another BITX20, VFO instability was traced to use of a transistor having too low an hfe factor. Work on my BITX-LF is going slowly, due to other more pressing work on (1) a 74HC4046 based H&P circuit, (2) installing and configuring DSL for Internet access, and (3) it is now spring in Idaho and outdoors activities are competing with ham radio activities! So far, my BITX-LF has the receiving AF, BFO (3.579 MHz), BFO-mixer, transmitter AF, and Solid-state T/R switching sections completed. I have a basic 3.579 MHz IF filter soldered together but not yet tested for shape factor. The above-mentioned 74HC4046-based H&P VCO will become the BITX-LF VFO if all works as anticipated. It will be interesting to see how your LF version of the BITX evolves. One major problem I have encountered thus far is finding suitable miniature inductors for 160 KHz work. Arv K7HKL _._ On Sat, 19 Mar 2005 16:44:20 -0500, paul daulton <k5wms@...> wrote:
A couple of years ago I built a transmitter strip using two ne602 chips --
Using Opera's revolutionary e-mail client: |
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Re: BITX ON 80 MT
Hans Summers
开云体育?
Ron
?
> OK Hans, you gave me plenty of
info to start
> with the minimalist
Huff&Puff. I know that there
> is a direct relation between
power consumption
> and applied frequency, but is an
eye-opener to
> read that you were able to
reduce vfo current
> as low as microamps using the
clock crystals.
> Your hints for changing certain
component
> values will certainly be of
use.
?
I'm
referring to the current consumption of the crystal oscillator timebase, not the
VFO. With a 4.096MHz crystal it was about 3mA, with the 32kHz it is about 30uA.
I don't remember what the current consumption for the whole VFO + Stabiliser
was.?I should have been more careful to record it!
?
73
Hans G0UPL |
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Re: BITX ON 80 MT
Ron Brink
Dear Paolo and Hans,
?
Sure Paolo, in general a mixer circuit (whether passive or active) generates both sum and diff. frequencies. Proper filtering after mixer selects your required (set of) frequencie(s). And yes, the levels of even harmonics are far below that of the odd ones (in general). Good luck with your BITX20. I have finished my BITX17 apart from the PA stage, but up till now I have great fun with receiving experiments (rtty, psk31, usb, cw in combination with mixw2.1?on a celeron 266 MHz and trying various VFOs).
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OK Hans, you gave me plenty of info to start with the minimalist Huff&Puff. I know that there is a direct relation between power consumption and applied frequency, but is an eye-opener to read that you were able to reduce vfo current as low as microamps using the clock crystals. Your hints for changing certain component values will certainly be of use.
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Hope to find some hours to spend on homebrewing this weekend but there are some obligations like cleaning the rabbit cage
 ?
Ciao Paolo and cheerio bye bye Hans
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Lots of homebrew fun de Ron PA2RF
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Hans Summers wrote:
Do you Yahoo!? Yahoo! Small Business - |
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Re: BITX ON 80 MT
Paolo Cravero as2594
Ron wrote:
Thanks for your research and the good www. information dr Paolo,Don't forget: 2*8.1 - 10 = 6.2 MHz 3*8.1 - 10 = 14.3 MHz (that would make it a dualband BITX changing output filter... should check the diagram, I am fantasizing) The mixer returns both sum and difference of input signals, right?! Too bad even harmonics (*2, *4, *6, ...) are not as strong as odd, otherwise a BITX20 could become a BITX17 changing output filters. I did find some x2 frequency multipliers, though... :-) But first of all, I have to start building my BITX20, then modifications can be applied! Please someone correct me if I'm writing nonsense. 73, Paolo -- QRPp-I #707 + www.paolocravero.tk + I QRP #476 \ Skype: pcravero / |
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Re: BITX ON 80 MT
Hans Summers
Hi Ron
If used for the BITX design, do you think the squarewaveI think it should be fine. If you look at the waveform at the mixer port of the original BITX it isn't very sinusoidal anyway. When I get a chance, I will put my homebrew spectrum analyser on the original VFO and see how the harmonic content looks. About the timebase. Compared to the original Huff&Puff (timebaseThe design should continue to work. The distance between lock points simply increases. In the extreme with distances of several kHz between lock points, you would need to increase the range of the correction loop - this means decrease the series resistor between the integrator and the varicap (1M in my original). The maximum division ratio of the 74HC4060 is 2^14 therefore with a 1MHz crystal the smallest lock step you could attain would be 61Hz, which is still quite acceptable. Of course, if you are prepared to add a third IC for more timebase division, you can have whatever division ratio you like! Note if you decide to use MHz crystals: for higher frequencies, you should decrease the resistances in the oscillator circuit: I suggest 2K2 and 1M in place of 330K and 10M. The advantages of the 32.768kHz crystal are: 1. They're cheap and everywhere, (clocks and watches) 2. They're ordinarily very small physical size 3. Small stages of division required to get good step size 4. Low power consumption On the latter point of low power consumption, this is the original reason that I started considering the low frequency watch crystals. Originally, I wanted to build a better version of my 2-chip frequency counter . The Mk2 version of that frequency counter, with the low current LED's, consumed between 4 and 5mA current, depending on how many LED's were lit. However, fully 3mA of that was spent on the crystal oscillator! It seemed highly unreasonable to spend so much current consumption on the timebase when normally one would expect that the most important place to spend power would be the LED display. The reason for the relatively high power consumption in the oscillator was that the CMOS logic must work hard to whip the capacitance back and forth, 4,096,000 times a second. The only solution: lower frequency crystal. The 32.768kHz circuit consumes a matter of some tens of uA. After much correspondence with Arv K7HKL he inspired and encouraged me make a combined Huff Puff and frequency counter, which eventually resulted in the current minimalist designs. Have fun and let us know how the results are 73 Hans G0UPL |
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