Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: Prev 1 [2]   Go Down
  Print  
Author Topic: Neon lamp antenna match indicator  (Read 6586 times)
VE3LYX
Member

Posts: 141




Ignore
« Reply #15 on: December 21, 2012, 07:28:43 PM »

I built a multi loop antenna just for experiment, for transmitting. I tried several methods of feeding including a 5 turn winding inside or between two shorter windings . When the coupling didnt pan out I disconnected it but rather then take it all apart I just left it. In a moment of whimsy I soldered a # 40 bulb accross the two leads of the unused coil.  I can see the antenna out the shack window of my basement and sure enuf it works perfectly as a tuning indicator. I have used neon lamps in screen grid modulation to drop the voltage so there was room to modulate the screen. It was in series with a pot and varied in brightness. It is quite possible a neon bulb would also work as an rf indicator but  havent tried it. I use on all my 1920s and 1930s Hb rigs a single turn loop with a 40 bulb installed. ,One side to the base and one to the tip of course (as are the others) It is in the tank circuit. just near, about 1/2 inch away and is very handy for tuning. I also made just today a twin lamp SWR indicator for 52 ohm coax using two 150pf caps instead of the "gimmick" type coupling used with twin lead years ago. It appears to work and also indicates power and tuning. I duplicated the old twin lamp circuit electrically although not mechanically the same. Why? Because I have three different swr meters and none agree. not even close. I am fed up with them and needed a more reliable method. It appears to work as it is supposed to but I will check further. 
I just made a load base mobile style 80M antenna for the patio railing and am seriuosly thinking about trying a loop and indicator lamp there to see if I can make it work. Lamps are great indicators .
Don VE3LYx
Logged
K8AXW
Member

Posts: 3592




Ignore
« Reply #16 on: December 21, 2012, 10:16:21 PM »

The neon bulb tuning method was used decades ago to tune antennas fed with twinlead, and I think, open ladder line.
Logged
VE3LYX
Member

Posts: 141




Ignore
« Reply #17 on: December 22, 2012, 04:50:12 AM »

I still have a couple of neon lamps from RS. I will try using them instead of the 40s just for fun. thanks
Don VE3LYX
Logged
N4EF
Member

Posts: 30




Ignore
« Reply #18 on: December 22, 2012, 06:31:11 AM »

Regarding bulbs as RF indicators, I was testing my Galaxy 5 MK III transceiver one day in 1975 using a 75 w incandescent bulb connected to the output of my rig. The bulb was on the table next to me.

I was transmitting, "Hello, test. Testing. Testing. Helllllooooooo". When I released the mic button,  I was called by W4CMI (SK) who was about a mile away. We chatted for awhile, then I rode my bike to his house and we had a nice eyeball.

Dave
Logged
WB6BYU
Member

Posts: 12974




Ignore
« Reply #19 on: December 22, 2012, 07:47:50 AM »

Quote from: VE3LYX
I still have a couple of neon lamps from RS. I will try using them instead of the 40s just for fun.


As long as you don't expect them to work in the same circuit.

The #40 is a low voltage bulb (6 - 8V @ 0.15A), basically #47 with a screw base.  My first
transmitter used a #49 ( 2.0V @ 0.06mA) link coupled to the output stage because it took
less power.  However, I was always burning them out.  Low voltage bulbs are a good
current indicator.

Neon bulbs require high voltage (typically 70 - 90V) at very low current, so are used to
indicate the presence of RF voltage.  The typical AC power indicator uses a NE-2
in series with about 100K to limit the current:  neon bulbs are similar to VR tubes or
zener diodes in that, once the breakdown voltage is reached, there is no inherent
current limiting.

I remember a friend testing for 220VAC by holding one end of a neon indicator and
touching the other end to the wires.

A series low-voltage bulb will be a better indicator for low impedance loads, and a shunt
neon for high impedances.  For a given antenna, this may vary from one band to the
next, of course.  I've heard of hams adding both in their antenna, and using whichever
one gives the best indication on each band.  Required voltage and current will depend
on impedance and power:  sometimes it may be useful to provide an way to adjust the
sensitivity.  But if the antenna is fixed, either a series or shunt bulb will increase in
brightness as more power is delivered to the wire.

A low voltage bulb can often be clipped across a few inches of antenna wire to give an
indication of current:  then you can change the spacing between the clips to adjust
the sensitivity.  LEDs can also be used this way, though the require a series resistor.
(The "Ultra-Bright" LEDs can show an indication at very low levels of current.)

A fluorescent tube will light all on its own from an electromagnetic field, so you can
hold it in your hand and wave it around your antenna to find where the field is
strongest (if you have enough output power.)


And all of these are distinct from using a light bulb as a dummy load, or the old
"twin-lamp" SWR meter.  There are lots of ways that lamps can be used as indicators,
and they are much cheaper than a meter when you only need a relative reading.
Logged
VE3LYX
Member

Posts: 141




Ignore
« Reply #20 on: December 22, 2012, 03:31:16 PM »

Thanks. Very good info. I couldn't find any in my junk box (neon) but I did install a two turn loop just below the loading coil on my newly minted base loaded short vertical now clamped to the second story deck railing (steel framed and outer braid of coax grounded to the decks steel frame) The bulb works nicely as a tune up indicator. Very definite indicator.
I also rigged up an in shack power indicator made from a similar bulb and 150pf cap. It works very well.
I like bulbs better then meters myself. They don't ly. I'll skip the neon experiment as I have under 30 watts in this TX and the other one down there is a 3 watt AM 40m rig. I still use a 60 watt bulb for a dummy load and am not the least bit ashamed of it. It has never lied to me. Cant say that about the meters which don't know which way stuff is going  or if it is just stray RF or whatever. With the bulb, "If it don't light it ain't right", period.  And the urban myth that they transmit?  Never worked anyone on a bulb yet and been at this 30 years so? Hard enuf somedays with a good antenna. If you have, lets set up a sked. I wanna talk to you on your bulb.
Don VE3LYX
Logged
K7KBN
Member

Posts: 2753




Ignore
« Reply #21 on: December 22, 2012, 07:05:10 PM »

Used to work from Las Vegas to quite a few places in southern CA, UT and northwest AZ using a DX-100B and a 75 watt light bulb right on my desk.  The receiving antenna was a 15 foot length of bell wire.

I personally witnessed another ham working the same range with just the output of a Heathkit VF-1.
Logged

73
Pat K7KBN
CWO4 USNR Ret.
VE3LYX
Member

Posts: 141




Ignore
« Reply #22 on: December 24, 2012, 06:24:40 PM »

I see. Well I havent had such luck.
Today I built a new version of the old twin lamp indicator but for 52ohm coax. All I had was 150 ma bulbs. Too strong. I will have to find some 40ma ones or 60 ma's(or try it on the big rig.)  Should work I think. We shall see.
Don VE3LYX
Logged
VE3LYX
Member

Posts: 141




Ignore
« Reply #23 on: December 27, 2012, 07:52:56 PM »

I finished the twin lamp for coax. I dont have the low ma bulbs(20 or 40 ma)yet but it should work. I opened the shield and fastened a wire to the centre core bringing it straight up and onto both the bulb tips connections. The bulbs are back to back. I cut two 2 1/2 inch pieces of 3/8 copper tubing and slid each over one end of the coax leaving a space in the middle about 1 3/4 inches. I bridged it on the bottom with hook up wire so electrically it is the same.  Centre core connected to tip of both bulbs. Shell of each bulb capacity coupled through the skin of the coax to the copper tubing sleeves which are interconnected as it was in the old 300 ohm twin lamp deal. I probably should have made the copper tubing lengths about 6 inches each but I didnt this time. I took photos but this site doesn't use them . Using a chunk of 2x4 I made a holder for the deviceby cutting a slot in the wood. I painted it battleship grey then mounted the device in the slot. I built two wooden straps to secure it. I have coax connections at each end. One mail , one female.
I also took the two turn loop/ indicating lamp from my base loaded vertical and made it a three turn loop. I taped all bare spots the tucked it in my antenna tuner/ Pi output network. No more watching meters and listening. Tune up is now a snap and I am getting better results .(tune up is bang on right away, doesnt need extra tweaking. )
Don VE3LYX
« Last Edit: December 27, 2012, 08:04:50 PM by VE3LYX » Logged
ZL1BBW
Member

Posts: 346




Ignore
« Reply #24 on: December 29, 2012, 12:19:06 PM »

I still use a neon for a quick power check, hold it close to a terminal on the 4:1 balun that goes to 300 ohm twinlead out of the shack and it will light up real good.

If you are ever kite portable, try putting a small fluorescent tube on the kite, launch it, AT NIGHT and start operating, then watch the reports of UFO's start to flock in.

Have seen this done many years ago in the UK, best laugh out for years

Logged

ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
AA4HA
Member

Posts: 1376




Ignore
« Reply #25 on: December 29, 2012, 01:59:28 PM »

That little neon bulb can also do double-duty as a static electricity detector-dissipator, if it light up when you are not transmitting and there are no other obvious RF sources it might be time to put the radio away for the night and to disconnect the antenna feedline.

As it has been mentioned they are usually installed in indicator light installations in series with a resistor to limit current. Just like an arc-gap surge protector tube, once they go into conduction they can draw lots of current. Fluorescent bulbs need a ballast for the same reason, to limit current when they go into conduction.

While in university in the lab we hooked up an NE-2 across a 0-400VDC supply and gradually dialed up the voltage while we recorded the current and observed the level (and color) of illumination. There was an area when the voltage exceeded 300 volts or so where the normally sedate orange/red color started to turn rather "ultra-violent" and took on tinges of blue, green and probably lots of other non-visual spectra (kinda cool). The NE-2 also became smoking hot until the electrodes began to blacken and the bulb fractured. (university was long enough ago that asbestos was still classified as an edible substance  Cheesy )
Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
W0BTU
Member

Posts: 1552


WWW

Ignore
« Reply #26 on: December 29, 2012, 05:48:44 PM »

... we hooked up an NE-2 across a 0-400VDC supply and gradually dialed up the voltage while we recorded the current and observed the level (and color) of illumination.  ... The NE-2 also became smoking hot until the electrodes began to blacken and the bulb fractured.

My experience years ago with dialing up the voltage on an NE-2 was a lot different. When I reached the voltage where the lamp conducted (roughly 60+ volts) the NE-2 exploded before I ever saw it light up. Little pieces of glass everywhere.

It was a 0-150 VDC 3 amp lab supply, the kind you could adjust the limit current. I forget where that was set, but after the first lamp exploded, I did adjust the limit current down twice, and exploded an NE-2 each time.


On another note, I certainly have used neon lamps as a sort of match indicator; but the first "match indicator" I ever used was a military surplus RF ammeter.
Logged

AA4HA
Member

Posts: 1376




Ignore
« Reply #27 on: December 29, 2012, 06:09:52 PM »

Just tossing this idea out there but I wonder if you could make your neon lamp flash at a variable rate depending upon the tuning. It would be a variation of a "relaxation oscillator". A diode in series with a resistor to the neon lamp that goes to ground. Parallel to the neon lamp you would have a capacitor.

Depending upon the rectified DC voltage it would form an RC circuit. Every time the voltage climbed to the point where it would fire the neon lamp the capacitor would discharge and extinguish the lamp, then the capacitor would recharge through the diode/resistor and when the firing voltage was reached the neon lamp would turn on again.
Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
VE3LYX
Member

Posts: 141




Ignore
« Reply #28 on: January 03, 2013, 06:15:22 PM »

Used to work from Las Vegas to quite a few places in southern CA, UT and northwest AZ using a DX-100B and a 75 watt light bulb right on my desk.  The receiving antenna was a 15 foot length of bell wire.

I personally witnessed another ham working the same range with just the output of a Heathkit VF-1.
I spent the day doing some tests with my dummy light bulb. Very helpful device . Since I had it all there I also tested if this was possible. My conclusion is you should go back on your medication.
Don VE3LYX
Logged
Pages: Prev 1 [2]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!