K5LAD - 50+ Years of Ham Radio Memories

Volume XL

 

Careful, Fred………… Here Come the Bloodhounds

By Jim Pickett – K5LAD

Search keywords:  RF probe, Sniff-It, Dycomm

How often have you strolled (or perhaps trolled) through the aisles of a hamfest and seen items that you could not identify?  In fact, you might not even be able to come close to figuring out what a piece is or what could have been its original design and purpose.  Hamfests do lend themselves to the elimination of strange and wonderful items that once graced the shelves of a ham’s garage or attic but are now seeking a new home.  Hams, also, are perhaps higher on the list of folks who spend their extra cash on really odd pieces of flotsam and jetsam.

Perhaps you ask the seller what is this wonderful piece that they’re selling since it looks so neat and would probably look good next to all the other useless things you already have on your garage shelves.  On occasion, the seller is even able to identify the part and give some insight into what it was used for in its early days, which may have been several decades back.

Many, or perhaps “some,” of these items may truly be useful items for a novice ham or an old-timer.  You might envision an immediate use for that “thing” lying on the hamfest table with a scribbled and wrinkled price tag.  On its face it is just about as plain a piece as you might ever find.  During the several years I sold them I never did see a one with any markings or identification.

Such is an item that I’ll describe below.  If you saw it on that hamfest sales counter, you might not realize just what a treasure it really is and quickly pass it by.  The information I’m about to convey is to say to any ham who reads it, “Be on the lookout for one of these.  It could prove its weight in gold for you.”  The item looks like this (minus the meter):

 

 

Front view of the Sniff-It hooked to a 50 microamp meter

 

Rear view of the Sniff-It

 

The official name for this is a “Sniff-It” and was manufactured by a company in Florida called Dy-Comm.  This company, operating during several years in the mid-70s, also sold 2 meter amplifiers for the FM crowd back when there were few amplifiers available for the new 2 meter FM group so this one was popular.  I’m thinking that their amplifier was even sold as a kit but of that fact, it is a bit hazy.  The Sniff-It was always advertised, in the pages of the ham journals, with a big bloodhound dog sniffing out ………. something.

As valuable as this piece was, it only sold for $5.00 retail, which was soon recognized as a real bargain for any electronics experimenter who did much bench work.  The Sniff-It was a very sensitive RF probe which allowed the user to “sniff out” very small levels of RF without affecting the circuit by touching or loading down any of that circuit.  It consisted of a small black plastic tube about 2" long and 1/2" in diameter with about a 3' piece of shielded miniature RG-174/U coax attached.  There was no plug or connector but instead allowed the user to add whatever connector matched their indication and display equipment.

I later learned that the tube contained two Schottky-Barrier hot carrier diodes attached to a metal disk.  It was an extremely simple device without any extra or fancy add-on pieces to elevate the cost.  A customer might see it, perceive the simplicity, and think, “I wouldn’t have any need for that” until they got a chance to try it and discover what a valuable tool it was.  It reminds me of the comment I received from a friend many years ago when I introduced him to the new product called ‘Beano.’    He scoffed at my praise for the product until he actually used it and later told me, “When you introduced me to Beano, you have changed my life.”  I think the Sniff-it ‘also changed people’s lives’   Hmmm……. Strange to be mentioning Beano and Sniff-it in the same paragraph…………… Oh well………..

As a workbench tool, it was an invaluable aid.  My Sniff-It was so sensitive that I once used it to peak the IF string signals of a Motorola 450 MHz radio receiver.  The RF signal there was nearly infinitesimal; yet the Sniff-It could read the small signal enough to be “peak-up-able” in that receiver strip.

 

 

 

 

 

I also built a box with a sensitive meter and a 741 op-amp IC for a meter amplifier to use with my Sniff-It, which increased the “sniffablilty” of the RF probe.  The box required both positive and negative voltage in reference to ground so it required two 9-volt batteries.  You already know how difficult it is to find an extra 9 volt battery around the house when you need it, just imagine how much more difficult it would be to find TWO at the same time.

 

I used my Sniff-It for many years and always wished I had bought several and stuck them in reserve after I had sold my ham radio store.  Alas, I only had the one.  I later loaned the one I had to a ham friend and he got it caught in his car door and crushed it completely.  I was crus…….., well, I was very disappointed.  I tried to find a replacement for several years, always unsuccessfully.

Then, years later, among the items I had to liquidate from the estate of my friend J.B. Stinnett - K5AMT (SK) was a complete surprise to me.  It was a Sniff-It and I didn't even realize J.B. had one; he'd never mentioned it to me.  I have been very happy to, again, have a Sniff-It in my technical arsenal and have used it even several times recently.

If you are wandering through a hamfest or an electronics-oriented yard sale and happen upon one of these strange-looking little devices, I highly recommend that you purchase what you’ve found and begin to take advantage of the myriad benefits from this innocuous little device.  It’s one of those hidden treasures, which are a “once in a lifetime find.”   Also, it’s possible that after this many years (+30) the original owner may not even know what a jewel he has………..but now, you know.  You should make like a bloodhound and try to track one down.

 73,

Jim - K5LAD

 

 Written January 16, 2012 - published TARC Newsletter March, 2012

 

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