I built a modulation light by soldering a #47 bulb to a pl259. The problem is that the light is bright when keyed and brighter when modulating. I guess that is really not a problem, but I think it would be easier to tell the difference in modulation if it weren't so bright with the carrier signal, because it is easier to tell the difference between dim and bright than bright and brighter. Any ideas on adding a resistor to dim the light some? In series or parallel? Please keep it simple for stupid (me). thanks.
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modulation light
- Thread starter thetnhillbilly
- Start date
Experiment with it! You're not going to damage anything of high value unless you grab the wrong end of the soldering iron.
You'll probably find that as you make the unmodulated light dimmer, the modulated light will be dimmer in proportion. I could be wrong...
Have you tried this light using SSB instead of AM? Might be instructional...
You'll probably find that as you make the unmodulated light dimmer, the modulated light will be dimmer in proportion. I could be wrong...
Have you tried this light using SSB instead of AM? Might be instructional...
Uh, are you using this bulb as a dummy load? If it's the only thing plugged into the radio's antenna socket, you're transmitting into a pretty high SWR. It's NOT a 50-ohm bulb.
If you call popping the final transistor (at least) when the bulb gets REALLY bright, then goes dark, errrr, "educational".
Memorable, probably.
73
If you call popping the final transistor (at least) when the bulb gets REALLY bright, then goes dark, errrr, "educational".
Memorable, probably.
73
Nomad - I HOPE he's not using it that way! I assumed (yeah, I know 
) that he had a coil/capacitor circuit adjusted for maximum brightness of the bulb, thinking back to my General test back in 1959...at least that's what came to mind when I read his post. Probably not.
) that he had a coil/capacitor circuit adjusted for maximum brightness of the bulb, thinking back to my General test back in 1959...at least that's what came to mind when I read his post. Probably not.I used to build those little modulation indicators using a #47 pilot lamp but later changed them out to a 28 volt bulb to keep them from blowing.I never kept them keyed but for just a few minutes or so ,just for a fast indicator during installations just for the presence of rf on a "Barefoot" cb....none of them are anywhere near 50 ohms...that was in the 60's....barefoot today could be 150 watts .....I can remember one local amp builder here around 1966 or 1967 that used a hundred watt 110 volt (standard household lightbulb) to prove to a prospective linear customer that his linears really "put out" the power!.... see how bright the light is ?
Hehehe... Nomad,are you still using that 100 watt light bullb ? ...LOL.....just a joke nomad
Hehehe... Nomad,are you still using that 100 watt light bullb ? ...LOL.....just a joke nomad
There used to be (maybe still is) a Rat Shack bulb that just happened to make a very nice 50-ohm load for quick modulation tests. I don't know the original number, but I think its mentioned in Lou Franklin's book "Understanding and Repairing CB Radios".
As a matter of fact I was using the bulb directly to the conector without any coil/capacitor circuit. Sorry if my ignorance offended beetle and nomad. I did come here for help after all, not crude criticism. Robogator and DTB, thanks to the two of you for trying to help. The bulb mentioned in Lou Franklin's book is the #47, that is why I used it. It think I remember measuring it at about 40 ohms. I was hoping to get the bulb to shine a little dimmer, like how it is easier to tell a poor signal from a good signal than a good signal from a better signal. At least for me anyway. Robogator, was the 28v bulb similar in resistance while being dimmer? If so, is there a specific part #?
I have a box of them around here somewhere,I think they were #1829 or simular to that,I had some 28 volt bayonet base ones just like the #47 except they had a red plastic covering over the bulb....BTW I have used bright red fingernail polish to do the same thing. makes a nice looking modulation light quick GO/NO GO... not for long keydowns...hehehe...use your bird for that!
About that soldering iron...
I have been soldering for more than 50 years and at one time or another I have "grabed the wrong end of the soldering iron!" by mistake....it won't take you long to look at it and let go!.. but if you happen to make that mistake,grab a can of circuit cooler and spray your fingers down real fast.... See,Circuit Cooler is good for other things too...
I have been soldering for more than 50 years and at one time or another I have "grabed the wrong end of the soldering iron!" by mistake....it won't take you long to look at it and let go!.. but if you happen to make that mistake,grab a can of circuit cooler and spray your fingers down real fast.... See,Circuit Cooler is good for other things too...
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