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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sun 14, 2016 7:40 pm 
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Might be another option; soda bottle preforms. They are the blanks that are heated and blown into molds to make soda bottles. Made of PET with a standard soda bottle cap. According to one of the answers the dimensions are:

"They are 5 3/8 deep. The inside diameter is 13/16" to a depth of 1 1/16", from 1 1/16" to 1 11/16" the inside diameter reduces to 11/16".

They are fairly plentiful and cheap. Here is one source;

https://www.amazon.com/Soda-Bottle-Pref ... B008MB1QNY

Philip; thanks for starting this useful topic.

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Sun 14, 2016 8:20 pm 
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Those also look like good candidates.
I like the transparency. When it fills with smoke I will know I stuck the probe end in the wrong place. LOL
Bill

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Mon 15, 2016 12:06 pm 
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Rick, I didn’t start this thread; Steve T did. But with the other thread I have tried to post sufficient information to enable construction of signal injectors, which are exceedingly useful, even if one has a radio room full of laboratory equipment.

With regard to batteries: The blocking oscillator is well known to work at very low voltages. It can work with almost dead batteries. Thus, an injector can easily be made to work from one or two AA, AAA, or N cells. And of course button cells of all kinds can be used.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Mon 15, 2016 12:27 pm 
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Philip Colston wrote:
Rick, I didn’t start this thread; Steve T did.


My bad! Thanks to Steve for starting and Philip for the contributions. I appreciate both.

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Mon 29, 2016 1:20 pm 
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Update on using the Micronta circuit. I had an AA5 on the bench and was poking it with the probe and was not getting a clean audio signal in the IF / audio sections even though the radio was working properly. I noticed as I got the probe near the chassis that the radio had the signal injector audio in the speaker fairly loud. Makes sense with the large inductor on the probe radiating rf. This radio has a couple of inductors in the bottom of the chassis that appear to be picking up the signal rather well so that touching the probe to a test point did not increase the sound level at all. After some time experimenting around I tried putting an O'scope probe in line with the injector. Since it is shielded it does not act like a long antenna and it has both a sharp pointed tip and a small spring hook. With the signal injector away from the chassis and using the probe the radio had almost no audible signal until I touched a test point and it produced a good solid tone. May not be true for every radio but based on this one I plan on putting a panel mount BNC on my injector and use the probe which has a removable ground clip that could be useful. I can then use a BNC cable end and solder a solid probe into the end of it. That way I can use it hand held with a short metal tip or keep the oscillator remote and use the scope probe.

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Aug Wed 31, 2016 8:44 am 
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Yes, the Micronta circuit is particularly potent, and has a larger coil than most, so has a strong external magnetic field. I have used these injectors for ages, and this is rarely a problem. Once in a blue moon, I have attached a long lead, in order to move the probe away from the circuit under test, as you have done.

To varying degrees, this is a factor in the use of all signal injectors, except the multivibrator type, which has no inductor. In some cases, it is actually a helpful feature.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Jan Sun 08, 2017 7:36 pm 
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I got this circuit to fit in an old felt tip pen, using 2 LR 44 batteries. I had to file the corners on the battery holder so it would fit.
I also found some 100 uh 300ma inductors on ebay costing about 3 for a quarter. They seem to work good with 3 volts.
I am also using an ac 128 transistor.
Bill


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Jan Sun 08, 2017 9:11 pm 
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Nice adaptation and good form factor. Also; easy to find.

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Jan Thu 12, 2017 8:01 am 
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With this thread in mind, I stumbled across a Gernsback Library book published in 1953 entitled Radio and TV Test Instruments, over on Pete Millett's excellent tubebooks.org site.

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link to high-res image
It has a chapter written by Robert E. Altomare on how to build the Signal Launcher, a hand-held vacuum-tube signal injector that is possibly the prototype of all of the pen-style electronic signal injectors.

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link to high-res image
The Signal Launcher uses a 3A5 dual triode tube in a classic multivibrator circuit.

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link to high-res image
Robert E. Altomare was quite creative in packaging the circuit.

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I've hosted a PDF file containing the excerpted chapter on my web-site.

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Last edited by stevebyan on Jan Thu 12, 2017 4:35 pm, edited 2 times in total.

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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Jan Thu 12, 2017 1:31 pm 
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Steve, many thanks for adding this excellent material to the discussion.

Signal injectors for radio work originate over a hundred years ago, in the form of an electro-mechanical buzzer, sometimes with a small condenser to couple the signal. They were used initially to adjust crystal and other forms of detectors to maximum sensitivity. Some crystal receivers and wave-meters of the era had the buzzer built in, or mounted on the front panel. Buzzers were commonly used for signal injection in the years that followed, and they still work well for this.

When did self-contained probe-type signal injectors first appear? In the first page of this thread, Lou deGonzague showed a pen-style signal injector, containing a tiny buzzer. The name, Oscil-O-Pen, was submitted for copyright by Lux Industries in 1950. But the instrument was previously called the Pen-Oscil-Lite, and was introduced in the December 1940 issue of Radio Today. It appears likely that this was the first probe-type signal injector commercially marketed.

Here is the article:
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Pen-Oscil-Lite Radio Today December 1940 S.JPG
Pen-Oscil-Lite Radio Today December 1940 S.JPG [ 94.99 KiB | Viewed 481 times ]

The Signal Launcher could well be the first electronic self-contained injector. The book was published in 1953.

I have here a two-tube (octal types 6J5G and 6SD7GT, both military surplus) signal injector, using a multivibrator circuit similar to the Signal Launcher. It is built on a small printed circuit board (there was never a cabinet), and is mains powered by means of a tiny selenium rectifier. It is a kit made by Progressive “Edu-Kits”, Inc. in 1959. Despite the circuit board, it has an appearance of a much earlier era.

It would be marvellous to locate an original Signal Launcher.

I think that subminiature tubes would be ideal for constructing probe-type injectors.


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 Post subject: Re: Anybody remember the penlight signal generator?
PostPosted: Jan Thu 12, 2017 4:09 pm 
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Philip Colston wrote:
When did self-contained probe-type signal injectors first appear? In the first page of this thread, Lou deGonzague showed a pen-style signal injector, containing a tiny buzzer. The name, Oscil-O-Pen, was submitted for copyright by Lux Industries in 1950. But the instrument was previously called the Pen-Oscil-Lite, and was introduced in the December 1940 issue of Radio Today. It appears likely that this was the first probe-type signal injector commercially marketed.

Thanks for the Pen-Oscil-Lite article, Phillip. I had forgotten about the electromechanical buzzer injectors.

Philip Colston wrote:
The Signal Launcher could well be the first electronic self-contained injector. The book was published in 1953.

And thanks for pointing out the date of the article; I had also forgotten to include that.

As a child, I learned about hot-chassis radios from a Progressive Edu-kit. After I figured out what was going on, I abandoned the rest of the Edu-kit project and never finished the series of circuits. They were too dangerous for my taste.

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