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Light Bulbs for Ladder Line Current Indication




 
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Author Topic: Light Bulbs for Ladder Line Current Indication  (Read 7979 times)
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aa5wg
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« on: September 07, 2010, 09:24:29 AM »

Hi to all:
What is the difference in a 250ma 12 volt incadesent bulb and a 250ma 120 volt incadesent bulb?  Are the filiments different?
73,
Chuck - AA5WG
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W2PFY
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« Reply #1 on: September 07, 2010, 09:37:40 AM »

I think it would be just a matter of of the wire gauge of the materials used assuming the bulbs in question are identical in function. The two types of bulbs could have different gasses used for their intended roles due to the voltage differential.

There's probably a lot of stuff on the net about light bulbs.       
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WBear2GCR
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« Reply #2 on: September 07, 2010, 10:12:05 AM »


Simple:

0.25 x 12 = 3 watts

0.25 x 120 = 30 watts

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k4kyv
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Don
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« Reply #3 on: September 07, 2010, 10:20:29 AM »

Mainly resistance.  Just use Ohm's law. The higher voltage bulb will measure higher DC resistance and have a higher wattage rating.

One characteristic of incandescent bulbs is that the filament resistance may vary widely from cold to hot condition, so measuring the resistance of an unlit bulb with an ohmmeter will give meaningless results relative to its lit condition.

The best way to use a bulb as  current indicator would be to clip it in parallel with a section of line - preferably two bulbs, one on each feeder.  That way, you are not inserting a resistance into the line.  A sensitive bulb is required to get any kind of indication.  One possibility would be one of the miniature bulbs used in series-strung  Xmas tree lights. Each one of those bulbs operates at a few volts and the current is very low.  The bulbs conveniently have wire leads  coming out the base, which can be readily soldered into a circuit.  A few inches of line ought to be enough to get an indication with one of those bulbs.  The white  lamps work best.

Look in some of the older handbooks for details of how to use a light bulb in this configuration to determine line current, and even SWR.
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WA1GFZ
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« Reply #4 on: September 07, 2010, 10:43:03 AM »

length of wire in bulb if the same alloy is used. Usually a bulb is about 1/10 resistance cold.
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aa5wg
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« Reply #5 on: September 07, 2010, 01:29:04 PM »

WA1GFZ, K4KYV, WBear2GCR, W2PFY and all:
Thank you.  I am looking at page 227 in the 1944 ARRL Handbook and they mention the No, 46 25ma dial light and a 1/4 watt neon bulb.  The photograph shows the lights.  They are very large, about 3 inches in length. 

Does anyone know a source for these larger bulbs?  I have only seen the very short bulbs for flash lights. 
73,Chuck - AA5WG
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Pete, WA2CWA
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« Reply #6 on: September 07, 2010, 01:52:48 PM »

http://www.bulbs.com/Light_Bulbs/results.aspx
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aa5wg
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« Reply #7 on: September 07, 2010, 06:18:55 PM »

Has anyone tried LED lights or Halogen Lights?
Chuck - AA5WG
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WBear2GCR
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« Reply #8 on: September 07, 2010, 06:55:44 PM »

they have this other thing called an RF thermocouple meter that might be of use?

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k4kyv
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Don
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« Reply #9 on: September 07, 2010, 06:57:25 PM »

I doubt that LEDs would work.  Remember, it is a diode

Maybe you need something like this:

http://www.intl-lighttech.com/store/item_1330
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Don, K4KYV                                       AMI#5
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aa5wg
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« Reply #10 on: September 07, 2010, 07:30:12 PM »

bear, K4KYV and all:
I would like to use lights instead of RF amp meters.
International Light looks like a good bet for QRP and maybe barefoot.  They have a lot to choose from.  Both good tips.  Thank you.
Chuck - AA5WG
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ke7trp
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« Reply #11 on: September 07, 2010, 09:50:30 PM »

The radio shack neon bulbs work fantastic.  Not sure if they stock them anymore but you can check.  Years back we used to heat shrink them to the tip of our Antennas on the mobile.  When you key, They Light up bright right and flash when you talk.  For some reason, We all thought this was cool.

C
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W2PFY
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« Reply #12 on: September 08, 2010, 10:57:28 AM »

Quote
Years back we used to heat shrink them to the tip of our Antennas on the mobile.  When you key, They Light up bright right and flash when you talk.  For some reason, We all thought this was cool.

I think I'll try that on my next 40 meter dipole, Maybe that will show the voltage points on the antenna when spaced out along the wire??
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Pete, WA2CWA
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« Reply #13 on: September 08, 2010, 12:33:26 PM »

A long fluorescent tube, and a long arm, will also help you find voltage points along the antenna and transmission line. Also useful to determine if your coax transmission line shield is radiating RF.

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ae6cm
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« Reply #14 on: September 12, 2010, 02:11:07 PM »

I am looking at page 227 in the 1944 ARRL Handbook and they mention the No, 46 25ma dial light and a 1/4 watt neon bulb.  The photograph shows the lights.  They are very large, about 3 inches in length. 

Chuck I don't have a 44 HB handy, but suspect the picture shows the bulbs larger than life.  The 46 is a 6v, 250 ma T-3 1/4 size screw-base bulb that is only about an inch long, and the 1/4w neon bulb is likely slightly smaller.

Here is a bibliography of RF current / power / swr measuring resources using lamp bulbs.  It's likely more than you want to know, but if there is an article there that you want and can't locate a copy, send me a PM.

Some small lamp data here: http://members.shaw.ca/pacifictv1/pldata1.jpg

73, Al


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aa5wg
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« Reply #15 on: September 16, 2010, 10:14:47 PM »

Al - AE6CM:
Thank you for the information.  I will use this.  I am trying sellect light bulbs for very low QRP (less than one watt), normal QRP (1-5 watts), barefoot power (35 -150 watts) mid-high power (100-500 watts) and high power (500 - 1500 watts).

I am looking for incadesent and neon bulbs for the above. 

At present I am going to try a candelabra female socket and if needed socket adapters to plug into the candelabra socket for lower power bulbs.
Thus, I am seeking candelabra threaded bulbs first.

73,
Chuck - AA5WG
Cedar, Michigan
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aa5wg
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« Reply #16 on: October 01, 2010, 08:59:47 PM »

Hi everyone:

Looking for a suggestion for neon bulbs as voltage indicators with link antenna tuner and ladder line.

What voltage for a neon bulb is recommended for 1 watt, 5 watt, 100 watt, 500 watt, 1000 watt and 2000 watt?

Thank you,
Chuck - AA5WG
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