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Re: Audio pre-amplifier for microphone?
I bought one of these to experiment with, thinking there may be an op amp gain stage between the electret and the A pin (audio out). Unfortunately, there isn't. So unless you want a VOX, this module doesn't improve over an electret mic insert and a series resistor to the phantom DC supply. Note also that A has DC on it, there is no series capacitor.?
There is apparently a similar Arduino/breakout module, about the same size, with an on-board electret insert, that does have an op-amp gain stage, leading to an audio output.? This could replace the mic amp on a homebrew exciter.? I am not thinking of the SSM2167 modules which are another thing altogether.? ?If anyone knows where these are, please post a URL. 73 from Paul VK3HN.?? |
Re: Antuino manual
开云体育OK, I'll check that. ?The series 1N4148 on the battery line could also be open. I found the schematic. ?Had trouble downloading from github but finally got it. ?Thanks, Jim On Aug 22, 2019, at 9:22 PM, Ashhar Farhan <farhanbox@...> wrote:
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Re: Antuino manual
Jim, The SMD parts are assembled on a Panasonic pick and place. No chance of a reversed diode. What is, however, possible is that the DC connector, which is hand soldered, hasnt been soldered properly. Open up the box, unscrew the PCB and flow solder on the tabs of the DC connector from the component side. I covered this problem a while ago.? A video manual is in the works. I finished a few yesterday, I will start posting th3 videos over the weekend. 73, f On Fri 23 Aug, 2019, 6:17 AM Jim Sheldon, <w0eb@...> wrote:
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Re: Antuino manual
From my post 71040:
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There's an updated schematic in this July 26 2019 post from Farhan along with a list of changes:????/g/BITX20/message/70551 As he states in that post, it all got archived here: ???? The previous version of the Raduino is found here, last updated in May of 2019: ? ?? Here's the manual:?? If the Bitx40 and uBitx are any indication,? there won't be a better manual coming out until you write it. Jerry, KE7ER On Thu, Aug 22, 2019 at 05:47 PM, Jim Sheldon wrote:
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Re: Antuino manual
开云体育That would be nice. ?Mine works fine on the external power input but 6 brand new AA cells in the battery box (9.56V) wont even light it up. ?I did check and have the 9+ volts on the PCB terminals but without a manual and current schematic I don't want to take it apart. ?Not really a happy camper right now. ?Farhan take note I suspect an open ?or reversed diode but without a schematic I can trust, I don't want to destroy it accidentally. Jim, W0EB? ? On Aug 22, 2019, at 6:43 PM, John Norris <jlnorrisjr@...> wrote:
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Re: Bitx40 very loud, high-pitched, low frequency noise
Thank you so much for your help Woody! I'll try to get my hand on a small ceramic cap and let you know if this resolved the problem. I'll also try to salvage the ferrite sleeve from an old cable. I'll also try to power the bitx using 8 AA batteries as a constant DC source to check if the problem is even related to the power supply. Hopefully 8 AA batteries will allow for at least a couple of minutes of RX operation.
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Re: Isolate any jacks/controls from metal chassis?
#ubitx
Used sticky back copper foil to line the plastic case on my SDRPlay. Worked well. Cleaned up some noise issues.
Jim WA3APC |
Moderated
Re: QST September 2019 pg42 to 47
CAREFUL! On Thu, Aug 22, 2019, 2:36 PM Dr. Flywheel <Dr.Flywheel@...> wrote:
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Original firmware upload OK, CEC not so much - what am I doing wrong?
Kim Cary
On my no-mods-yet v5 ?BitX when I upload the?UBITXV5_CEC_V1.200_16P.hex I get 16 block symbols in the LCD upper row and no function or encoder response. When I upload?ubitx_20._org.hex I get a functioning radio but I'm back to where I started.
What am I doing wrong? How can I troubleshoot this? |
Moderated
Re: QST September 2019 pg42 to 47
I took a course from the Mises Institute once on intellectual property. It wasn't until I was IN the class that I found out the professor was an IP contrarian. He didn't agree with copyright and intellectual property laws. I put up with his oh so libertarian claptrap for a couple of weeks, then told him I was dropping the course, because his opinion was that I didn't deserve anything for the effort I put into my own writing and artwork for my comic book and webcomic series.
People who go to THOSE lengths to justify stealing my work then trying to educate me as to why it wasn't really stealing are toads, and I told him so. Gwen, NG3P |
Re: Bitx40 very loud, high-pitched, low frequency noise
Woody
开云体育One more thing.... A ferrite sleeve is useful for common mode RFI a higher frequencies, but has little effect on lower frequencies, like audio.? It provides a series inductance in the supply line, so more that one turn of a supply cable through the sleeve (if will fit) will be more effective than just one pass through. Woody --
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Re: Bitx40 Fuses
Woody
开云体育On 8/22/2019 21:38, Donald wrote:
Jerry Gaffke, in post #44333, suggested using a 1/2A fuse for the main board, and using 2A or 3 A for the PA. Perhaps a little over-kill, but... That would provide the ultimate protection for the board, mostly by avoiding burning of circuit board traces in the event of a short.? As they say, silicon is faster to blow than a fuse ;)?? Reverse polarity power can kill semiconductors, then (if they go shorted) blow the fuse.? That is why a shunt power diode is useful in addition to a only fuse - to blow the fuse before the reverse polarity voltage reaches critical devices.? A series diode will stop the reverse voltage without blowing the fuse but will add about a 0.6 volt drop to the equipment. Woody --
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Moderated
Re: QST September 2019 pg42 to 47
There is a racket going on with college textbooks.
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These days you can wind up spending $300 on a required book for a class. And there's various schemes to discourage a used market, kickbacks to encourage the powers that be to choose specific textbooks, etc Costs can be way more than $1k/yr. Not true everywhere.? Some schools make a policy of of using freely available material where possible. And even make it possible to get credit by "attending" class online. Worth considering when shopping for a University. Generally speaking, I find it best to keep my nose clean with respect to obeying the law. If you feel a law is wrong enough that it needs breaking, then go for it. That can at times be an important civic duty. But don't be surprised if there are consequences. Regarding the ARRL and their grip on those copyrights, that's their privilege. They seem enough of a force for mostly good that it is worth putting up with (YMMV). Though if I spent 6 months on a project that I wanted made easily available to amateurs worldwide, publishing in QST or QEX would not be my first choice. Jerry, KE7ER On Thu, Aug 22, 2019 at 02:05 PM, Ken Hansen wrote:
So textbooks cost $1K/year, tuition is $20K, and it's the TEXTBOOKS that are the problem? |
Re: Bitx40 very loud, high-pitched, low frequency noise
Woody
开云体育On 8/22/2019 20:15, SP9DEV wrote:
Piotr, Lower value capacitors cannot hurt, but they are only useful for Very High Frequencies.? The type of capacitor (electrolytic,? ceramic, silver mica, etc.)? have different characteristics at different frequencies. ? For example, tantalum electrolytic capacitors are typically useful at higher frequencies than aluminum electrolytic capacitors due to the lower ESR at high frequencies.? Lower capacitance ceramic or silver mica capacitors typically have lower ESR at high frequencies than do electrolytic ones. ? For the very lowest ESR, "chip" (SMD) capacitors perform best.? This is because the lead wires on other capacitors add inductance in series with the capacitor, thus increasing the ESR.? In your case. it is doubtful that going below .01 uf will be helpful. A physically small ceramic capacitor of .1 or .01 uf should be low enough to bypass anything less than VHF frequencies or very fast transient spikes.?? Here is a reactance calculator that will give the effective series resistance (ESR) of a capacitor.? This is for an ideal capacitor and does not take into account lead length and the type (construction) of the part. If you have any old computer cables, power supply cables, or similar that have a molded lump in the line, that is a ferrite sleeve.? Many times I have cut away the? molded plastic, pulled out the wire, and used them in my circuits. ? Good luck! Woody - KZ4AK Google translate (maybe): Kondensatory o ni?szej warto?ci nie mog? zaszkodzi?, ale s? przydatne tylko w przypadku bardzo wysokich cz?stotliwo?ci. Rodzaj kondensatora (elektrolityczny, ceramiczny, mika srebrna itp.) Ma ró?ne w?a?ciwo?ci przy ró?nych cz?stotliwo?ciach. Na przyk?ad kondensatory elektrolityczne tantalu s? zwykle u?yteczne przy wy?szych cz?stotliwo?ciach ni? aluminiowe kondensatory elektrolityczne ze wzgl?du na ni?szy ESR przy wysokich cz?stotliwo?ciach. Kondensatory ceramiczne lub srebrowe miki o ni?szej pojemno?ci zwykle maj? ni?sz? ESR przy wysokich cz?stotliwo?ciach ni? elektrolityczne. W przypadku najni?szej ESR kondensatory ?chipowe” (SMD) dzia?aj? najlepiej. Jest tak, poniewa? przewody o?owiane w innych kondensatorach dodaj? indukcyjno?? szeregowo do kondensatora, zwi?kszaj?c w ten sposób ESR. W Twoim przypadku. w?tpliwe jest, aby pój?? poni?ej .01 uf b?dzie pomocne. Fizycznie ma?y ceramiczny kondensator .1 lub .01 uf powinien by? wystarczaj?co niski, aby omin?? cokolwiek mniejszego ni? cz?stotliwo?ci VHF lub bardzo szybkie przej?ciowe impulsy. Oto kalkulator reaktancji, który da efektywn? rezystancj? szeregow? (ESR) kondensatora. Dotyczy to idealnego kondensatora i nie uwzgl?dnia d?ugo?ci o?owiu oraz rodzaju (budowy) cz??ci. Je?li masz jakie? stare kable komputerowe, kable zasilaj?ce lub podobne, które maj? uformowany guzek w linii, jest to tuleja ferrytowa. Wiele razy odci??em uformowany plastik, wyci?gn??em drut i u?y?em ich w moich obwodach. --
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