The VK3TJN / VK3XAJ Ultra Sniffer Description

What is it ?

A sniffer is a small handheld radio receiver optimised for location radio transmitters. The Ultra Sniffer is better and easier to use than any sniffer you might have used before. The picture above shows the small size of the sniffer compared to a standard 9V battery.

What makes this sniffer better ?

There are a number of disadvantages with simpler sniffer designs:

• They are too deaf. A typical wideband sniffer is simply no longer adequate for Melbourne Friday night hunt foxhunts. Often they do work well, but when the fox is hidden well away from car access or is a lower powered fox they are useless.
• Interference from Pagers. A 2m wideband sniffer has insufficient rejection of high power paging signals around 148MHz. When run in whoopee mode you can't tell the difference between interference and the real fox.
• No User Feedback. The only indication a sniffer user had of how close they were getting to the fox was the position of the RF-Gain control. In the dark whilst crashing through bushes this is not something easily and quickly determined.
• Tuning in the real fox. More selective super-sniffer designs solved the first two of the above problems but generated a new one of their own. They have an extra knob to tune in the fox. This is not an easy task whilst jogging. It is almost impossible to tune in the fox if is is intermittant such as in Mt.Gambier or ARDF style hunts. It is possible to attempt to tune in in advance using a handheld as a pseudo fox, but changes in battery voltage, temperature and mechanical disturbance all contrive to move the free running oscillator off frequency so some tweaking is usually required. Using a handheld in this way during a hunt itself is very misleading to other hunters, and is not legal in ARDF hunts.
• Insufficient Attenuation. Some designs were great when the fox was weak, but try to DF with them when the fox is using 40W 10 meters away and they fall in a heap. This is the worst sort of sniffer....one that keeps you running for kilometers but won't get you that last few meters.
• Battery Chewers. The super sniffers take more current, especially when used with an audio amp and loudspeaker. Replacing the battery usually involved taking it apart (again!) with risk of damage each time. Also how many times has your sniffer accidentally been left on ?
• Hampering Headphones. You had an option of using a loudspeaker on your whoopee sniffer and waking up all the dogs in the neighbourhood (as well as making it more difficult to direction find), or using headphones with the lead plugged into the sniffer. This dreaded umbilical cord makes climbing obstacles tricky and usually is frequently broken.

Wouldn't it be nice if there was a sniffer that was really sensitive when you needed, but able to become really deaf also, and still let you know how close you were ?

Wouldn't it be great to program in the fox frequency before the hunt and just KNOW it will be correct when you sniff ?

Wouldn't it be neat to be able to use your sniffer as an FM two way handheld on your liason frequency ?

Wouldn't you love to be able to get rid of that headphone cable and fiddly plug ?

How about no more pager noises, no more hopelessly overloaded detectors and a sniffer you can dunk in a bucket of water and afterwards have still work ?

Features at a Glance

• Microprocessor Controlled.
• Programmable Frequency on FOX and LIASON frequencies in 5KHz steps.
• Auto Power Off after 2 minutes of no user activity.
• Sensitivity down to -125dBm. Usable Dynamic Range up to +15dBm.
• Automatic up-ranging to get the best DF performance.
• Range Button to request the sniffer to down-range.
• Range indication (how close you are) by Flashing of a LED, Audible Range
• Clicks and the Frequency of a tone when you push the range button.
• Whoopee, AM and FM modes.
• 10m (28MHz), 2m (144MHz) and EPIRB (121MHz) versions.
• Speaker, Headphones or Wireless FM headphones.
• Remembers the frequencies when turned OFF (only needs to be programmed once).
• Rechargeable Nicad battery with on board trickle charger.
• Simple to use whilst sniffing.
• Two way FM communication on the LIASON frequency.
• Automatic level control on audio when used to transmit on LIASON frequency.
• Fully Waterproofable and Robust.

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