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Super sensitive RF Sniffer Device




 
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Author Topic: Super sensitive RF Sniffer Device  (Read 1258 times)
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WA2SQQ
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« on: March 17, 2017, 08:49:30 AM »

About 40 years ago I purchased, what was advertised as, “a super sensitive RF sniffer”. It was a small black capsule with a short length of RG-142 coming out of it – no power required. You simply attached it to your Simpson and selected the “ua scale”. It cost me $5. I’d have to assume it was a diode and a few other mystery components.

It was sensitive – just getting within a few inches of the 455 oscillator circuit would give you a mid-scale reading on the meter. Does anyone remember these? Any idea what made it so sensitive?

Over the years it got misplaced - I'd sure like to find another or build something similar.
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WBear2GCR
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« Reply #1 on: March 17, 2017, 11:20:03 AM »

No idea, but perhaps the same as the Heathkit "RF Probe" for their VTVMs??
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_-_- bear WB2GCR                   http://www.bearlabs.com
Steve - K4HX
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« Reply #2 on: March 17, 2017, 11:51:42 AM »

 Take any hi-z probe an put it close to your circuit. I bet you see the same thing.
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W1ITT
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« Reply #3 on: March 17, 2017, 12:22:54 PM »

I have one of those, probably bought in '69 or '70.  I think it was advertised in 73 Magazine. There was a cartoon picture of a hound dog in the advertisement, as I recall.  It lives in the drawer of my rollaround scope cart, has been a handy little device over the years and I wouldn't sell it for anything less than the price of a Bentley. Well, maybe...  Perhaps someone could X-ray one (my Sweetie is a lab tech, not an x-ray tech, but both come in handy at times.)
I have always assumed the it was a couple turns of inductance, probably a 1N34, and perhaps a high ohm load resistor. Using some type of tubular plastic form and some epoxy, one could be cobbled up pretty cheap.  I don't know any X-ray babes, and I wouldn't want to try any other form of autopsy.
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WA2SQQ
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« Reply #4 on: March 17, 2017, 01:16:59 PM »

That's it! Any name on it, or on the packaging?
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W1ITT
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« Reply #5 on: March 17, 2017, 02:50:35 PM »

Bob...
I just checked.  There's no name or logo on it, and I don't believe there ever was.  After 45 years, what packaging there may have been is gone.  If someone has a 70s era 73 Magazine copy they may be able to leaf through and find it.
I think there may have been some sort of wattmeter substitute jig sold with it as an option too, but I'm stressing my memory banks on that one.  As I recall, there was a coax section and a clamp that placed the Sniffer a precise distance from the inner conductor of the coax with a chart that indicated a particular voltage corresponding to RF power.  I wonder how frequency dependent it was.  Anyhow, that was beyond my financial resources as a kid so I never found out.
I'm not sure how hot the market would be for such a critter today but, if it has what I suspect for innards, it might make a nice ham project.  I'll bet there's some outfit in China that could make them by the pail full for not much money.
Norm W1ITT
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W1ITT
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« Reply #6 on: March 17, 2017, 06:20:52 PM »

If I try to remember something and fail, it usually comes to me later as long as I don't worry on it too much.  That was either called the Sniff-It  or Sniffit.  I got rid of my collection of 73 magazines so I can't be of any help there, but I'm fairly certain it was advertised in there as that was the only magazine I could afford at the time.
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Pete, WA2CWA
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« Reply #7 on: March 17, 2017, 08:53:01 PM »

Ramsey had this one:



Triplett also has a "sniff-it" tool:

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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
WA4WAX
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« Reply #8 on: March 19, 2017, 11:03:45 AM »

Put a neon bulb in a little wand.  Bias it just a hair below the firing voltage.  Regulated DC is good as there is no drift.  You want a pot that allows fine control.
 
Now put it in proximity to an RF field.

Old timer's trick.
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WA2SQQ
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« Reply #9 on: March 20, 2017, 08:29:15 AM »

Really? I'll have to try that. Thanks
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Pete, WA2CWA
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« Reply #10 on: March 20, 2017, 01:21:25 PM »

I've never found a neon bulb to be effective down in the milliwatt region even when you manually adjust the fire voltage using an external DC source. A simple RF sniffer is a microammeter with a 1N34 or equivalent diode across the terminals and short length of stiff insulated wire connected to the positive terminal of the diode and meter.
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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
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« Reply #11 on: March 20, 2017, 03:15:59 PM »

I'm building this one:)

https://youtu.be/uVkJqqZroN0
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WA2SQQ
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« Reply #12 on: March 21, 2017, 01:00:16 PM »

I watch his videos regularly - quite a guy!
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WA4WAX
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« Reply #13 on: April 29, 2017, 11:07:21 PM »

Here is something you might like.  From the UK.

http://americanradiohistory.com/Archive-Practical/Wireless/70s/PW-1972-01.pdf
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WA4WAX
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« Reply #14 on: April 29, 2017, 11:09:53 PM »

Page 811 in the magazine.
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