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RT Plus VHF Transmitter

thumb_rtplus_logoThe RT Plus is the standard by which all other falconry transmitters are measureed.  Designed around the reliable 1/3N lithium battery which gives the overall unique shape and size. With its longer battery life and powerful signal, it was developed to be a primary leg mount for larger shortwings and longwings (18oz birds and up). The RT+ was the first of a new generation of transmitters with a short, safe, half-length antenna, yet still puts out more power than others still using long ones. It is also ideal as a secondary (backup) transmitter to the PowerMax backpack mount. Features are now found in the RT+ never before available in a falconry transmitter (see link below).

Each unit is burned-in and Enviro-tested tested from +150F down to -40F prior to shipping. Thousands of the current RT Plus transmitters are in use in the field worldwide with enthusiastic and reliable results.  Available frequencies: 216, 217, 218, 219


“All other features come second to reliability”
For the RT+, it’s at the top of our list. Every aspect of this new circuit had reliability at its core. Everything from the 54 components selected and used in this stable new circuit (some parts have an average rated life of 300 years!), to the processes used in the manufacture (surface mount technology) to the mechanical design makes it the most bombproof design possible.

The crystal-based oscillators of the past have always been vulnerable to failure through crystal breakage when used as a leg mount on hard-hitting birds. Using new generation surface-mounted high-shock oscillators, the risk of having your transmitter fail from a fractured crystal has been reduced to near zero.

What does this mean to you? Tune in once and the signal is always there, same pitch, same sound. This transmitter circuit automatically adjusts to changes in its environment. In addition, temperature and voltage compensation handled by the circuit guarantee you always hear the same tone in extreme environmental changes.

The general rule in producing a powerful radio transmitter antennas has always been: do not cut it shorter than ¼ wave length (which is 13 inches at 216 MHz), or you’ll lose a lot of the radiated power output. But with the Marshall transmitters, we’ve found a way to overcome this barrier and increase the output power while keeping our shorter, much safer antenna.

With the Magnetic On/Off switch, batteries can be left inside the transmitters, until they need to be changed. To turn it on, you simply hold the magnet to the lid or body of the transmitter until you hear three rapid beeps, which tells you the transmitter is on and running. You do the same thing again to turn it back off. This means transmitter can be left on the bird, such as a bird touchy to tail mounts, and then be turned on again just prior to the flight with the tap of the magnet. Tap-on just before flight; tap-off after picking bird up again. This new convenience does not add any risk to the reliability of the design, as it’s fault positive, meaning, if it should fail for any reason, the transmitter is left on. Also, if the magnet is lost, the transmitter can still be turned on and off manually as before.

No more having to ‘test batteries’ with a battery-tester before each flight to see if they are nearing the end of their useful life. The transmitter does all this for you: you get a double-beep on every fifth pulse indicating it’s time to change. And, when you first hear the low battery warning, you still have a 3-4 day reserve to look for a lost hawk.

We’ve found a way to again improve on the efficiency of the circuit, giving the most power output while barely sipping power from the battery thus extending it’s life as long as possible. Using the latest generation of field effect transistors and dynamic resonance circuitry, this new design pumps more energy into the antenna without wasting as much power through internal resistance.

What this actually means is: it lasts longer.

Also, through greater efficiency in the circuit (and some black magic inside), the power output you hear will now be more consistent as the battery drains. This is not the case with the older designs where weak batteries or very cold temperatures mean a correspondingly weak signal or failure.

Intended Use

Using the wire-clip design, the RT+ can be mounted to one of the deck feathers of a large falcon or hawk. The spring can easily be removed in the field to make an emergency switch to a leg-mount.

Still machined from the strongest aircraft alloy available (7075), these carefully crafted cases protect the internal circuitry while giving protection to the batteries as well. For the RT, the overall appearance and weight is similar. But, there’s a new flat ‘fin’ portion at the bottom which now gives better leverage and grip when screwing down cap.

This transmitter is best used as a longer-life tarsus mounted transmitter in combination with a PowerMax or Micro on the tail or BackPack Harness. The leg mount shown here is the most common use for the RT+ due to its shape and size.

Customers Say

kentuttle"I have been a falconer for 40 years. Like most of you, I have lost some good birds over that time. Many were lost before the advent of telemetry, but some were lost with telemetry, due to transmitter failure. In falconry we face many challenges, dealing with inferior telemetry should not be one of them.

"I have used most all of the American products. I have tried many different transmitters and a few different brands of receivers. Some of the transmitters are not reliable, some are not waterproof, some produce a weak signal. I have found that no other falcon transmitter can compare to the power, reliability and beauty of Marshall RT transmitters.

"Marshall products are worth the investment. You can find some cheaper but you may pay through the loss of a valuable bird. I recommend without reservation all of the Marshall products falconry products, including the wonderful new pointing dog collar."
Ken Tuttle, PhD, UT



steve"I've used Marshall RT transmitters since the beginning. I believe I am their toughest customer: I hawk sage grouse 6-days a week from September through February each year with three birds. Grouse hawking is done in dangerous country because if you lose your bird out of sight on a tail-chase for just a few minutes, it will probably be killed by an eagle. I trust Marshall transmitters because, more times than I can remember, I've got my birds back with Marshall transmitters when another one had failed.

"In fact, I have been given free transmitters by other companies, just to say I use them. But I don't. I actually pay for Marshall transmitters because I trust them and they have the best range by far."
Steve Chindgren, WY



darylpeterson"Many falconers have lost a bird for a day or two, or even an afternoon and upon retrieving her, have noticed damage to the transmitter. Most often this happens with the larger birds, and the damage is usually a stripped antenna, curled or bent, or damage to the post of the transmitter. Something to try might be to leave your transmitter on your bird for a while at home and see how she behaves with it while she has free time. Most birds will preen or pick at the transmitter a little bit but seem otherwise content with it. Still, there are those who will go to great lengths to make the antenna look like a pig's tail, or bite it off. My eagle is one such bird. She can tear the hell out of an average transmitter in a short time..........Lot of good that would do me if she had all night up on a mountain. So I had asked the crew at Marshall about some options, and have been using a combination for a while now that is nearly indestructable. The RT transmitter is made out of machined alloy, and is very strong. Marshall also made a delrin attatchment that screws on the base of the transmitter to protect the post. This, coupled with a heavier antenna is super strong, and not too ungangly for the bigger birds. So if you have a ornery female gyr, peales, or an eagle, you may want to ask the folks at Marshall about this set up."
Daryl Peterson

jimmyadamson"I would highly recommend the RT+ transmitter to any falconer looking for the best. As an active falconer for over 40 years, I've seen firsthand the development and first use of telemetry. At first there were those who resented it as a crutch and said a "real falconer" knows where his bird goes. While it's certainly not a replacement for weight management and training, I have to say we've learned so much more about our birds' behavior and abilities with telemetry that we'd never had an idea about without it.

"Nowadays, it's pretty much considered foolish to ever fly without two transmitters. And I'm glad Marshall has come along to produce such high quality equipment."
Jimmy Adamson


shawnhayes"I have used the RT+ for a few years now while training and hunting with my falcons. Every year I travel to different parts of the country to fly & hunt my birds. With all the different types of terrain my falcons and I encounter, I can honestly say that the RT-Plus has the power and range to be used as both a back up or your primary transmitter. I trust mine to the fullest.


"Whether I'm flying Ducks & Sage Grouse in Wyoming or Prairie Chickens in Kansas, my two RT-Pluses have been there when I needed them. And the short antennas give me peace of mind.

"To all of the hard working folks at Marshall . . thanks for hooking my falcons up with the RT-Plus.
Shawn Hayes



stevejohnson"The RT transmitter has the best range of anything I've ever used. And it does it with a short antenna.

"What I also like is that it uses the 1/3N lithium battery which keeps working down to very low temperatures. And since it's a lithium battery, it has a 7 year shelf life so I know I'm always getting a fresh battery."
Scott Johnson


markholmes"When I started looking for telemetry I had no idea what to get or why. When I bought, I chose Marshall because of the compact receiver. The RT+ transmitter was an afterthought. Since then, it has converted me.


"When learning how to use the telemetry, I would have my son take the RT+ transmitter and hide it out in the hills. Once, his hiding place was about 7 miles out of town, on a small ridge, lowered on a string about 3 feet down into a narrow crack in the sandstone. I went right to it and stood on top of it for several minutes before I figured out what he had done.

"And it's tough too. Once I was in a hurry and dropped the receiver on a dirt road as I got in the truck. It had been run over I don't know how many times before I got back to it. The case is scratched up but it still works just like new."
Mark Holmes, Vernal Utah

Q & A

Why do you use a metal case for your transmitters?
The machined aluminum casing is for superior protection. The strength to weight ratio of aircraft aluminum is superior to anything else. We've learned that internal components are shielded from outside RF interferences as well. The screw on lid was designed to let you avoid having to handle the battery every time you turned it on or off and to keep water away from the battery and battery contacts. It also eliminates the risk of a lost hawk tearing off plastic tubing or electrical tape used on the older designs and removing the batteries.

I've heard of people having their transmitters come unscrewed during flight with a canister designs used as a leg mount. How have you solved this on the RT+?
This can certainly happen if the the lid is not screwed down completely. Some people have been told by other companies not to screw down the lids too tight on other canister designs or they would void the warranty. This, and their incomplete lid assemblies, has led to a more than a few birds coming back with only the lids attached.

With the RT+, this will not happen. Our internal gold washer spring has six small prongs that provide very strong back pressure for a lock-washer effect. The RT+ body and lid are machined so that you cannot over-tighten it. There is no flex or damage to the circuit board by screwing it down too tight. Simply screw it down 'till it stops, then push the lid and body together and tighten some more. The new flat body shape actually helps you to get it even tighter, a new process we now call Easy-Crank. It will then not come unscrewed on its own, through normal use on a bird even if it was left out for 100 years.

Another key mechanical improvement: our gold springs are made from beryllium copper that is chemically etched (not stamped) to very tight tolerances of a thousandths of an inch. These are then precision formed into the right spring shape here by us, heated-treated at very high temps for 4 hours, and then gold-plated for best possible conductivity and corrosion resistance. Also new for the RT+ is the direct battery connection through just the spring (not the lid). And the spring is now surfaced-mounted (machine-soldered) for maximum reliability.

Is the magnetic switch reliable?
Yes. We use a solid state Hall effect switch (a quantum magnetic device) that allows you to just hold the magnet to the transmitter for a second to turn it on and off. We've also perfected a way to use this neat little switch without an appreciable increase in battery drain, even if left in (and turned off) for months.

What are the best ways to mount the RT+?
For those still using leg (tarsus) mounts on medium to larger sized birds, the RT+ is the ideal shape and choice. Built around the venerable 1/3N lithium battery, it provides a highly reliable secondary or backup transmitter. However, with the addition of the magnetic tap on switch, it also works well on the new BackPack setup.

What kind of range might I expect from the RT+?
We've hung these transmitters up out in Wendover Nevada and received a good signal line-of-sight back in Utah at the top of Francis Peak, some 115 miles away. But the important measurements are on the ground and in actual hunting terrain where there are obstructions and other conditions that adversely affect the signal. And in every situation that you'll encounter, the RT+ will readily and clearly outperform other transmitters in the US market, excepting of course, the PowerMax.

Image Gallery

Shorter ant...
Shorter antennas make the RT+ a safer leg mount Shorter antennas make the RT+ a safer leg mount
Bottom View
Bottom View Bottom View
RT+ from be...
RT+ from below RT+ from below
The RT+ as ...
The RT+ as a backpack mount The RT+ as a backpack mount
Gary Boberg...
Gary Boberg with RT+ legmounts Gary Boberg with RT+ legmounts
Extra prote...
Extra protection from a custom leather cover Extra protection from a custom leather cover
The aerodyn...
The aerodynamic The aerodynamic
Stephen Lea...
Stephen Lea's tiercel Stephen Lea's tiercel
The Rimling...
The Rimlinger's in Wyoming with RT+ legmounts The Rimlinger's in Wyoming with RT+ legmounts
Durable des...
Durable design takes abuse and lasts Durable design takes abuse and lasts
Two matchin...
Two matching leg mounts on a hybrid Two matching leg mounts on a hybrid
Neck mounte...
Neck mounted RT+ on passage Tundra Peregrine Neck mounted RT+ on passage Tundra Peregrine
Open with b...
Open with battery Open with battery
Steve Chind...
Steve Chindgren with Scottish Hat and RT+ leg mounts Steve Chindgren with Scottish Hat and RT+ leg mounts
RT+ as a ne...
RT+ as a neck mount RT+ as a neck mount
Stanislav s...
Stanislav shows the RT+ on the TrackPack Stanislav shows the RT+ on the TrackPack
Top View
Top View Top View
Closeup of ...
Closeup of RT+ Leg mount Closeup of RT+ Leg mount
The RT+ is ...
The RT+ is the ideal leg mount design The RT+ is the ideal leg mount design
Dorsal moun...
Dorsal mounting of both transmitters Dorsal mounting of both transmitters
RT Plus
RT Plus RT Plus
Gary Boberg...
Gary Boberg's bird Gary Boberg's bird

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