Hi Charles! I want to design 20W VHF power amp. for my FM TX because I found an already designed one at a website, but I couldn't found the required values of...
A good source for ham project parts is Dan's Small Parts http://www.danssmallpartsandkits.net/ ahmed73500273 <ahmed73500273@...> wrote: Hi Charles! I...
I bet I couldn't find those trimmers in my "big" town, either! Those are pretty big values and a small trimmer is likely to not be very stable or able to...
Hi Folks, I'm playing around with building a small frequency generator that I could use in the field to check/drive speakers. I took a measurement last night...
What DC voltage does your frequency generator require? Or, how much audio power do you need and what is the speaker impedance? Could you step the 7.5 volts...
Hi Charles, Well...I don't have a frequency generator, so I'd have to build that too. I've been using an old Yamaha TX802 (FM synth) but I don't want to lug...
I'm guessing that the 1.5 amp draw was at 12 volts which is 18 watts. Some of that is lost to inefficiency so lets pretend that 14 watts reaches the load....
Squarewave would be perfect. It's not rocket science, it's just jolting the thing at different frequencies, and I think those 4 batteries could pull that off...
I didn't realize these batteries are available up to 11v/3400ma! http://www.shulmanaviation.com/E-Tec.html That's got to have a good sock to it. Maybe use 2 of...
Don't confuse mAh with mA. mAh is the product of mA and hours but it doesn't mean that the battery can only supply that much current. It simply tells you how...
Hi Charles, Thanks, I'll dig into it tomorrow... Yes, I didn't realize mAh was hours! But if I can only get 1 minute of performance, that's good enough for...
You really like the idea of paralleling batteries? charleswenzel <charles@...> wrote: I'm guessing that the 1.5 amp draw was at 12 volts which is 18...
No, but it isn't necessary for that current drain. The 1100 mAh lithiums are bound to have an acceptable discharge rate of several amps. I don't like putting...
Ok, I'm back. :) Keeping in mind that I'm really bad at this, here is a "draft" of the modified circuit: http://www.400gt.com/technical/misc/circuit2.jpg I...
Hummm...already I see a problem. There's no way +12v will go straight to the speaker. oops. But anyway, maybe you can point out what I need to change to get...
You have the speaker wrong. Connect the top of the speaker to the negative side of the 1000uF capacitor and not to +12. Connect the bottom of the speaker to...
I have invented a new energy source whereby heat is converted directly into electrical power. The heat is absorbed from background air or water that is of...
Thanks Charles, it's starting to make sense. I think next step is for me to breadboard it. I have a feeling some of those resistors will need to be power ...
Hi Charles, I finally got around to building the circuit: http://www.playerviolin.com/misc/speaker_driver/speaker_driver.htm Unfortunately, nothing much...
You might want to add a resistor in series with the frequency pot, maybe a 100k or so. Also, some of those prototyping boards split the power strips right in...
Got it running Charles! And it works great. I forgot to tell you something very important, which would have clued you in to the problem (because I forgot...
I think that wire is OK! Something else must be wrong. Perhaps one of the transistors is shorted or the wrong type. ... myself ... wire ... concerned. ... ...
Thanks Charles -- that makes a huge difference! Now the circuit is really hammering the speaker even with the battery. I'm goign to play around with values...
I think I would just let the circuit run "full blast" and control the volume by adding a low value potentiometer, maybe 25 ohms, at the speaker (one end to amp...
Thanks Charles. I've been playing around with the circuit and it works great. I hooked up an oscilliscope and have been watching all the "inverting" pulses....
Oh, one more question. The positive/negative pulses are of unequal duration throughout the system (viewed with my oscilloscope). Sometimes the positive...
