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Field Marshall Digital 800 Tracking Receiver

thumb_Field-Marshall_logoThe Digital Field Marshall 800 offers superior performance and amazingly small.  Now equipped with Marshall latest generation HSL "Half Sized Loaded" Yagi antenna.  The Field Marshall 800 offers the best performance of any VHF receiver.  Giving the most sensitivity available in a one-piece compact, rugged and very small design.

The Digital Field Marshall 800 is the premium choice for the falconer looking for additional channel capacity on multiple bands as well as the smallest size of any full performance receiver available today.

This premium tracking receiver offers more sound volume from any position with speakers on top and bottom, an ultra-compact heavy-duty case design featuring a "Quick-Release" handle, LED front lighting of the control panel for night tracking, improved water resistance for use in wet weather, and the latest generation of Marshall's exclusive collapsible HSL yagi antenna.

Also, unique to the Digital Field Marshall is the addition of polyphase filters, our new noise floor reduction technology that reduces the background noise while increasing the effective range and tracking ease.


FM800: $895  Frequency: 4 band selectable 216-219MHz, 200KHz per band, equipped with Half Size HSL Yagi


Since this receiver doesn't rely on crystals to determine the frequencies it can cover, it has more capacity and flexibility. An all-digital circuit allows the same receiver to pick up any frequencies on 4 bands (216 through 219 MHz).  Allowing tracking of dog collars on 217, while falcon transmitters are on the classic 216 and 218 bands.

A broadened, smoothed tuning mechanism means that tuning into the signal is a pleasure and much faster than before.

Tuning with the tune knob is broad and is protected from accidental contact so it's not easily bumped off your tune setting when getting in and out of the vehicle.

Higher Sensitivity: With the Digital Field Marshall offers the industry's best sensitivity (improved by another 3dB over the prior generation), equal to that of the Stealth, long the gold standard of telemetry receivers. This means a significant increase in reception distance for the same transmitter.

The actual sound of the receiver has been improved through the elimination of harsh harmonics and distortion, making it easier to track weak signals and far more pleasant to listen to.

Three red LEDs illuminate the entire control panel for better clarity in the dark without compromising your night vision.

As great as it is to have a handle on long walks or when holding the receiver out the window, there's times when it's better without it. Greater portability and reduced size is achieved without the handle on a third axis.

So, how to have it both ways?

Answer: The Quick-release handle. Improved for even better ergonomics.  Now, you can choose when to use it and when to put it away in another pocket. Even though it's tight and secure with its bracket mount, it takes only seconds to remove it using the thumb wheel screw-on design.

Those who've now used it, love it.

Hold the receiver down waist high and you have a speaker facing up at you. Hold it up high for better reception and you still have a speaker facing down at you. By incorporating top and bottom speakers, the sound on the Field Marshall has optimal sound volume from all angles.

And yet it's also quiet where it needs to be: A narrow-band filtering system is employed rejects noise better without reducing your signal, so you hear the signal more clearly with less distracting background noise, even for the weakest signals.

More importantly, it has improved the sound's omni-directionality which means the volume doesn't change as you rotate the receiver, a definite problem in other receivers that leads to erroneous perception of the signal strength in certain directions.

Nearby transmitters on other channels sometimes cause interference to your reception, but this receiver has special circuits to minimize the effect.

The improved rejection of noise near power lines means you can hear weak signals better and increase your range.

Better Range Estimation: The range settings (Medium and Near) have been adjusted so that you know it's time to start walking. You can therefore switch between these in most situations to get a better idea of how far from you the bird or dog really is.

Electronics are housed in a robust case machined from a solid block of aircraft aluminum.

Purposely made for heavy use outdoors, this tracking receiver is designed to give you more years of trouble free operation through the widest range of temperatures, travel and weather than any other. Sealed connectors, mylar speakers, overlapping seams all make this receiver the most durable design now on the market.

In addition to all the performance improvements made to the Digital Field Marshall, our engineers redesigned and shrunk the receiver board to about 20% less total area, with everything fitting inside the case much more efficiently. We then asked our design team to "vacuum pack" the case down to the absolute minimum required, with no wasted airspace on the inside, no needless bulk on the outside. The result is a smaller overall receiver.

With the handle removed, the slimmed down design fits even better in your hand. Designing the outer case to be hand-held required we make additional changes, like a larger radius on all corners, and counter-sinking the earphone and power jacks to make them flush with the surface of the case, all of which just makes it feel more like an over-sized iPod in your hand.

Turns out the case is much more stout and rugged than even the previous generation Marshall receivers.

Improving the shielding on the case also means an improvement in how the antenna works for you. It's simple now to track up to within inches of a transmitter lost in the grass with the same pin-point directionality you get at a distance. The full-size three element yagi gives the best range and directionality of any antenna, and reduces the "back lobe" which sometimes fools people into tracking 180 degrees backward, in the wrong direction.


It's also designed to use six AAA batteries, available almost anywhere and inexpensive to replace for low operating costs.



Using newest generation electronic components and creative packaging allows us to fit a lot into a small space. And, our commitment has always been to using aluminum alloys which have the maximum strength to weight ratios makes this receiver as light and strong as technically possible.

A key mechanical design breakthrough of all Marshall receivers is the collapsible yagi antenna. The full-sized three element antenna can be reduced in size by half when fully closed.

When collapsed down into its stowaway position, and put into its holster (included with every new receiver), the new Field Marshall makes a small and compact piece of equipment to take with you into the field. With the new HSL Yagi, it literally becomes a "pocket receiver."

Marshall pioneered the collapsible yagi nearly 2 decades ago.  And we've kept the pressure on in developing the most advanced 3 element yagi in the world with our new HSL Yagi.  We kept the same, field proven, collapsible, three-element directional antenna design for maximum directionality, critical when searching for a lost falcon. But with the HSL yagi, we've figured out a way to maintain virtually the same performance while reducing the overall form factor by 50%.  This incredible reduction in size, a huge step forward in ease of use, is now small enough to be used practically inside a vehicle).


HSL Yagi


What is the HSL Yagi?

It is a new design that reduces the overall size and weight of the yagi antenna by half. Since it uses small loading coils to do this, it's called the "Half-Size Loaded" Yagi, or, HSL for short.

It's now standard equipment for the FM800 receiver.





How does this new yagi compare to the regular size Marshall yagi?

For the three key areas that an engineer designs for, the forward gain, the front-to-back ratio and the directionality, it has the same performance as our full-size yagi antenna. And our full-size yagi is virtually optimal in terms of the achievable performance in gain and front-to-back-ratio.




How did you shorten the antenna without losing performance?

The elements have been reduced by 30% in length, but each one now has a tiny structural loading coil designed and produced here at Marshall Radio to accurately maintain the "electrical length" of each one.


Loading_coil_detail_-_350wWhat's a loading coil, and how do they work on a receiving antenna?

Here's an explanation from a recent interview with Dave Marshall: "There are ways of shortening a regular size yagi and maintaining its performance by keeping it electrically at a half wave length. You fool the electrons in to thinking it's a half wave length and they still manage to time their travel across the elements correctly so it's perfectly resonant like the pendulum of a clock that's got to keep in tune with the transmitting frequency as it goes back and forth. We alter the path of the electrons, and there are various ways of doing that using principles of self magnetic induction which slow the electrons down on their path and various other techniques. This is called "loading" the antenna, and it's a combination of adjusting the diameters of the elements and adding certain fixed components in that tend to create a spiral path for the electric current to travel down. As it does so it creates very rapidly changing magnetic fields, that if you get it just right, they kind of speed the electrons on their way just at the right moment and then at the other moment they slow them down, like putting the brake on.

Holding_without_handle_view_-_300wThat part is the little lumpy but really cool looking thing you see now on each of the elements that a normal full size yagi doesn't have. It took a lot of time to design that in such a way that it'd have the right performance and allow the elements to be shortened just the right amount, be structurally sound and rugged and the biggest parameter of all that you have to be careful about is that it's easy when you shorten these antenna element lengths to lose a lot of the efficiency in the antenna itself through certain kinds of electrical losses that occur. The nature of a shortened antenna element is that it involves much higher currents flowing along with much lower voltages. And the result is that these higher currents tend to be dissipated in resistive loss or well just loss as they travel along the elements, and especially this little helical loading element that we created. So it's very important to design that with just the right shape, the right material on the inside, and the right type of metal. All these factors come together to make it a "low-loss loading component." And if you don't do it right, your shortened antenna will be much worse than the full size antenna.

On_receiver_side_view_-_300wIt's that challenge that probably makes it so that loaded yagi are not so commonly seen, as you look around. Even with HAMs (Amatuer Radio enthusiasts), when you look at their yagi antennas and you see these big lumped elements, those are usually not loading coils, they are called traps. They have a different function which is to make the antenna elements assume various different lengths depending on what frequency of energy is fed into it.

I find it interesting that inductively loading yagi antennas I don't see that in the published antenna work very frequently or in practice as I drive around cities, I see all kinds of yagi antennas, but I rarely see this. You see in in the vertical roof top antennas. But is is a challenge to do it just right, and not make it actually worse."

(To read the complete interview, click here)




Customers Say




With Marshall's new smaller antenna and reciever, tracking a falcon in or out of a vehicle now allows you to put even more of your attention into getting to your falcon quickly.

- Hubert Quade, ID








"The new Field Marshall is a remarkable receiver with features that translate into tangible advantages in the field. It is so well shielded and filtered that, not only is range vastly improved, but localizing a signal is so fast you can literally run right to it. This difference is not lost on those of us that have arrived moments before a stalking coyote or eagle!

"In recent years, I have flown well-hacked gyrfalcons that share a rather cosmopolitan view of the sky. This past season, a talented young female, “Sonde” took it upon herself to ring long-billed curlews up to the space station. Fortuitously, I had the new Field Marshall to find her quickly when she drifted back to earth miles downwind.

"Having used or tested most other receivers, even in places as sketchy as the tropics, I think there is nothing that touches this one. The beautiful little unit is also rugged, so it is a no-brainer to always have it along. It is simply an awesome unit."

- Alberto Palleroni, CA

Steve_C_Thumbnail3"I began using the new digital Field Marshall in September and at first I had a little trouble adjusting to the different settings being so familiar to using the Stealth. After giving it a little time I became familiar with the new Field Marshall and found it a very sensitive and much improved receiver. I hawk Sage Grouse and unfortunately some flights result in long tail chases that sometimes end with a kill. Finding your bird quickly is important to protect it from predators. The new Field Marshall receiver is very directional and has a much cleaner signal, filtering out most disturbances. It has three settings far, medium and near. I have found that I only use two of these setting the far and the medium. As far as I can tell the near setting would be useful for locating a lost transmitter that may have fallen off the bird. I have a secure method of attaching transmitters so I never need this setting. When the bird is on the ground over 300 yards away you will not get a reading with the medium setting this tells you your bird is down so I switch to the far it is very directional leading me to the kill. ( I use the medium setting when getting close) If the bird has missed and is still flying I will get a signal on medium, which tells me to stand my ground and wait for the bird to return. I am fortunate to have very nice flying birds although my eyesight is not as good as it used to be and finding my bird when it at a nice pitch is becoming more difficult.

"The new Field Marshall is a dream, better than bells for locating a falcon in the sky. I use the medium setting and the unit is so directional that I can point it skyward and it will tell me where my bird is and then I can spot it. In the past when a falcon was high and over head you would be drowned out with a signal but the FM 100 is so directional that it will point right at the waiting on falcon using the medium setting. If you are hunting and are watching the dog it is hard to keep an eye on the falcon waiting on high above when doing this I have my new receiver folded up in my vest pocket with the unit on, as long as I can hear the signal I know my bird is above. If the signal gets weaker I know the bird is out of position. When this happens I stop and pull out the receiver and flip to the medium setting, which tells me exactly the position of the waiting on falcon.

"I have a hard time giving up old equipment that has worked well for me in the past I used a Marshall Stealth with another Stealth for a back up. Now after a season with the new receiver, I intend to find homes for my old receivers and get another digital Field Marshall for my back up receiver. When you hawk in wild places you know the importance of extra tires, shovels, batteries, water and a back up for anything you want to keep! (your life, bird etc.)!"

- Steve Chindgren, UT

Dave_R_Thumbnail"I was thinking about writing you to say how much I love my new receiver! The new Field Marshall really is an amazing piece of technology and a real quality unit...You should be charging more!

"There are a number of features I like such as the smaller size, quick release handle and improved antenna. But, what I really like is that it's just easier to track a bird. The combination of a very directional unit plus almost no background noise makes this by far the best system I have used and I find that I can track a bird much faster than before. I am happy to say that I haven't had to track my new hybrid much this season but I use it to find him quickly on a duck in the bushes which is important because the red-tails seemed to be more aggressive than ever before. I have also used it to track the birds of my friends and we used it in Wyoming when I was at Steve's in the fall.

"I am very glad I changed my two transmitter frequencies so they each have the same last three numbers. I just switch from 216 to 218 without having to punch in the numbers each time. Thanks very much for helping me with that when Marci and I came by for a visit!"

- Dave Rimlinger, CA

Jeff_B_ThumbnailI am part of the lucky generation that came into falconry just as radio telemetry was becoming affordable and widely available.  Of course, that also means I'm old enough to remember when "innovation" meant your yagi antenna came with a handle.  Over the years, I've bought and used receivers from three different manufacturers.  Each unit had its merits, but each also suffered its disadvantages.  In particular, high signal sensitivity and simple portability in the field seemed an elusive combination.  So I kept trying different units, hoping to eventually find the one that met all of my needs.  Unfortunately, even though appearances changed, basic technology for radio telemetry –receivers and transmitters- seemed to be fixed for most of this time; as if it had been closed in a room, shielded from the digital revolution that was unfolding outside.  Then Marshall Radio Telemetry came along, figured out how to open the door, and everything changed.

There is a business-related paraphrase, taken from Ralph Waldo Emerson, that says "Build a better mousetrap, and the world will beat a path to your door."  In the radio telemetry business, nowhere is that philosophy more clearly on display than at Marshall.  I was first seduced by their marvelous RT transmitters, now called the RT Plus, which coupled a radically shorter antenna with very impressive power and range.  After using RTs for a couple of seasons, I couldn't even bear to look at the antennas on my other transmitters and sold them all on the Raptors Nest.  Of course, if you've been using Marshall transmitters, you know their beauty is far more than skin deep.  Beneath that tough, laser-engraved shell lie new generation surface-mounted high-shock crystals that virtually eliminate the risk of transmitter failure after a hard strike.  Just as important, the circuitry is designed to automatically adjust to changes in temperature and battery life, so that the signal frequency and strength stay constant during my coldest days in the field.  I've suffered serious anxiety –and a few sleepless nights- in the past because my older transmitters didn't stand up to either challenge, and I appreciate the sense of well being my RTs give me each time the hood is slipped.  If I need to locate my bird, I'm confident there will be a signal to track, at the exact frequency I tested before the flight. 

The satisfaction I'd developed using Marshall's transmitters inevitably led me to buy one of their receivers, a Field Marshall FM-15.  My first impression was a lot like what I had experienced with the RT transmitters; I was immediately taken by the incredibly different look of this receiver.  It's slim design and top-mounted pop out yagi antenna took portability to an entirely new level.  More importantly, it was better able to discern a faint signal than the receiver I had been using, and also better at helping me find my bird when I got close because of the signal attenuator.  I loved it.  Over time though, I learned it was not quite as sensitive as Marshall's more expensive Stealth receiver, because on two occasions a friend with one of the latter units was able to pick up my bird's signal when I could not.  I'd be lying if I said this discovery didn't bother me, but the feeling was tempered by the knowledge my FM-15 was still better than the other two brands of receivers I had.  As I've already said, though, high signal sensitivity in a receiver matters a lot to me, so I was pleased to read a few years later that Marshall had incorporated Stealth technology into its next generation of Field Marshall receivers.

Watching Marshall's unrelenting commitment to technological innovation and quality improvement over the years made my choice for a new receiver easy when I discovered my old RB-4 backup had quit working late last season.  I bought the new Digital Field Marshall 800, and experienced "WOW!" all over again.  Everything on this new Field Marshall has been made to be more compact; even the antenna has been miniaturized through remarkable engineering.  The digital tuning technology also adds to the high-tech feel of this unit.  The real question, though, was how it would compare to my FM-15 in the field.  For the remainder of the season, I pulled out both receivers at every opportunity, testing them against one another for signal strength and quality.  I noticed two significant differences right away; I got a stronger signal with the new FM800 receiver, and the pulse had a lot less background noise.  Marshall reports that the latter feature is due to the incorporation of polyphase filters noise reduction technology.  The former, of course, is a result of the superior sensitivity I had expected in the FM800.  In this new receiver, I feel Marshall has delivered the ideal combination of high signal sensitivity and portability in the field.  If you have one of their older receivers, I strongly encourage you to consider upgrading, like I did.  I think you'll be very impressed.  If you've never tried their products, or shied away when the company was young, you really ought to give them a try.  Marshall builds the best telemetry equipment I've ever used (or seen), and I know of no other company that has come anywhere near their level of innovation. 

Thanks Marshall, for showing falconers around the world what it really means to build a better mousetrap.

- Jeff Broadbent, PhD, UT


I have been fortunate enough to have travelled the world in my falconry related ventures. As the director of the falcon hospital for the Project for Falcon Conservation (Pro Fal Con), in Al Ain, United Arab Emirates, I was in charge of veterinary care for the hunting falcons of His Highness the President Sheikh Khalifa Bin Zayed al Nahyan. I also provided  veterinary support for the large falcon breeding project, the main emphasis of Pro Fal Con. My position included supervising, on site, the hacking of 60-70 gyrs, gyr/sakers and gyr/peregrine females during the 2 month hack season in the mountain foothills northwest of Damascus, Syria.  I also lived alongside the falconers in the Syrian desert and trained gyrs and gyr/sakers for the Sheikh each fall. During the month of September, we trained up to 75 young falcons which were then entered on wild quarry.  As a guest of the Sheikh, I hunted houbara in the Cholistan Desert of Pakistan.  When not travelling for the Sheikh, I flew my own passage Black shaheens and Barbaries. In each of these places, the  falcons wore Marshall transmitters. 

Locating hack birds or tracking a falcon lost while chasing houbara, I reached for my Marshall Stealth receiver, while some of the other falconers used other types. The Marshall receiver proved its worth time and time again. I always had a strong, directional signal to follow.  Now back in the US, I spend a lot of my season hunting grouse in the sandhills of Nebraska with my own gyr hybrids (tiercel and female).  While my old Stealth still works fine, I now carry the Field Marshall 4000. The technology packed into this little receiver is amazing. There is virtually no background noise and the transmitter signals come through loud and clear. I have recently added the HSL yagi to my setup and I am very pleased with the overall size and portability. I have been able to track my birds with the yagi fully deployed inside my vehicle, when necessary, which saves me a lot of precious time.  Telemetry has come a long way.  I look forward to your newest innovations! 

- Tim Sullivan, D.V.M.

Mike_Garcia_Thumbnail"I have been using the new Digital Field Marshall  this season. During the last four months I have been on the road through sixteen states covering over fifteen thousand miles attending meets and hunting all over the western United States. I have to say that the Field Marshall helped me out on more than one occasion when looking for that very, very weak signal.

"With the new polyphase filters I was able to push up the volume and still keep the background noise down (static). This allowed me to pick up a beep when other units were only able to receive static.

"The new Field Marshall receiver is just one of the many reasons I think Marshall Radio is number one."

- Michael Garcia, IL




Steve_Schwartz_Thumbnail"I am quite happy with the new Field Marshall. My old Field Marshall is still in great condition but it now collects dust as my trusty emergency spare.

"The new Field Marshall's improved directional sensitivity is a real asset. Much of my daily tracking is at close range. My old hybrid likes to lay down and hide on hun kills, and with just a little ground cover it becomes a pure telemetry game to find him at times...and to avoid stepping on him. I've spent some time practicing with transmitters dropped in snow or grass, and it's real handy to be able to hold the unit (with the antenna closed) by the machined handle's lower loop, and simply skim it (upside down) a few inches above the ground. The receiver seems to be very sensitive to proximity when used in this way, and errant transmitters that find themselves off of the bird are quickly found. (I'll tell you the story of crawling around in the dark in skunk sprayed stubble looking for my micro another time.)

"I am very pleased with the new FM's ability to filter out interfering noise. My old receiver, by contrast, was quite "noisy" when switched to "far", and I regularly had troubles tracking birds while standing close to powerlines. No such problems with the new unit, and not just a minor improvement, but a great one.

"The housing and new antenna are a great package, and the removable handle is nice, but I don't find it necessary. I realize I speak only for myself on this one and I suspect some day I'll realize this advantage as others have. Perhaps pistol-grips are better received up here in Canada. The battery housing is also nicely improved.

"I rarely change channels, as both of my falcon transmitters are on 216.035. I don't understand why more don't use this method. My dog collar is on 219.035, and the switch from bird to dog (with no overlap from one to the other) is infinitely simple."

One Year later: "I really, really like the receiver. My young gyrXbarbary from last year routinely "dispersed" when slips got a little beyond my control. Sometimes he'd miss his intended target, remount, and just fly away. It was common to not see him until 10-12 miles away where he would just be cruising in a straight line, heading out. Two RT+ (with good batteries and straight antennas) and the FM took the stress and anxiety completely out of his little expeditions. A number of times he went on these jaunts when I had other falconers along to spectate. Most of the time once the falcon was recovered, the guests' conversation would end up suggesting that without quality telemetry, a bird like him would be simply impossible to enjoy for long. I tended to agree!"

- Steve Schwartze, Alberta Canada

Pineo_Thumbnail"I've consistently used the new Field Marshall receiver this past season as my primary receiver. It's a significant refinement from the original, which was a breakthrough receiver/antenna combination in its own right.

"Even without considering the improvements in gain and noise reduction, the new Field Marshall is a big improvement over the original in three ways:

  1. You finally took my advice and made the pistol grip a modular element attached with a beautifully machined bayonet fitting. Excellent execution of this concept, beautifully machined;
  2. The new receiver housing is significantly more compact than the original, and therefore easier to hold;
  3. The new folding antenna retains all of the positive, instant deployment of the original, but is much simpler and more robust, as well as being narrower in folded mode and therefore more compact. The machining on this antenna, and the mechanical design with the helical springs is just beautiful. Very elegant design. Excellent!

"I've had quite a few opportunities to recommend the new Field Marshall receiver to a number of customers and friends, without reservation. Its stout design and construction, compact size, and sensitive gain make it the compelling choice. I suspect new technology will soon displace current dominant RF technology in falconry and sporting dog telemetry. Until this happens, the new Field Marshall will be the last word and only choice for falconry or hunting with sporting dogs."

- Doug Pineo, WA

Stalislaz_Thumbnail"I have been using the Marshall receivers 8th years now. Started with Dave Jamieson's Stealth in Nevada deserts. Then after three seasons went back to Czech Republic and start use it here in small hillside with many small villages and towns around. So I had to learn new tracking tactics.
I and mine few freinds tested four different receivers from europe and US and one made here in CZ. The Marshall was on top.

"Now I sold mine two years old FM-10 receiver and and start use the new Digital Field Marshall firs season. In the start it was hard as I was knowing the old receivers sensitivity well. After few chases the receiver start be mine new friend.

"Has very good sensitivity, is more directional, small to carry in mine hawking vest, has nice professional dezine. And it is not like a toy receiver that does not get good direction when you need it because it points to the falcon like no other receiver I have ever tried, straight to the falcon with no mistake.

"I think it is the best in all the world, not just the Czech Republic."




- Stanislav Menclik

Rick_S_Thumbnail"When describing and answering questions about falconry, I have, more than once, said that I would have given up on the endeavor if it wasn’t for radio telemetry. Fortunately, I was able to put a transmitter on the first long wing that I flew in 1979. That eyass female merlin would have been lost in her first season if it wasn’t for a leg mounted unit.

"Today, more than ever, I rely on this equipment to pursue my favorite style of falconry. When flying solo, without the aid of another pair of eyes, I often need to locate a high flying, wide ranging falcon or to make fast tracks behind a tail-chasing grouse hawk.

"Thinking back to earlier models of telemetry receivers, I am so glad that there have been a handful of people with the inspiration to push innovation forward to give us the choices that we have today.

"This last season I had the pleasure of using the new Digital Field Marshall. Some things do get better with time! This new version of the Field Marshall receiver has some developments worth noting. The biggest overall improvement is the use of a polyphase filter to lower the background noise level to improve signal recognition. For those times that you are up on a high point frantically sweeping the horizon, you can count on this receiver to locate that distant beep.
Smooth and sturdy are the first words that come to mind when describing its updated physical characteristics. The antenna with its new helical springs deploys with a quick and concise motion. Another neat change is the addition of two keepers to seat the last elements folded, making a unit that only deploys when intentionally engaged.

"There is also improvements you can really put your hands on. With its slightly smaller size and rounded edges, user comfort has been enhanced! And last but not least, the removable handle offers the option to comfortably palm this extraordinary unit.

"More than once I was able to put it to the test at the end of the ’08 hawking season. Often, my late blooming immature Gyr/Perg. Tiercel would mount wide and disappear from site as I moved in for a flush. With this unit’s super directionality and sensitivity, it was possible to quickly relocate my bird and seize the moment."

- Rick Sharpe, WY

Dave Interview

Interviewer: Tell us about this totally new Marshall receiver, and what you set out to achieve.

DLM: “We started out as a project just to replace the current Field Marshall with one that has a much wider frequency selection. Yet as things went on, we kept finding new possibilities, “Why don’t we change this, why don’t we add that?” Suddenly last year we were spending a lot of time on it, suddenly we were getting very picky about what we wanted to improve. We began thinking it’s a new receiver and it’s got to be really good. And we got lucky in a few instances. We happened to strike a rich vein of potential that will keep it viable for a long time to come. So what you get in the new Digital Field Marshall is a brand new technology, state of the art design, and if I do say so myself, a bit of real precision engineering.

As it turned out, the biggest change was to improve the filtering on this receiver, to make it so much more responsive to a weak signal, so much more sensitive and so much more free of the noise which obscures your signal. Those were breakthroughs.”

Interviewer: Why do you say Breakthrough? That’s a strong word for an improvement.

DLM: “Well, receiver technology has been around for a long time, and the same techniques have been used for decades and decades. But with the latest generation of electronic RF [radio frequency] devices, there are substantially new, profoundly new approaches to issues and it was just natural to take advantage of these. And we used what we think are some novel or clever ways that gave a result that even surprised us.

Interviewer: Describe for us the concept of “Signal-to-Noise Ratio” and how you improved it.

DLM: “The Signal-to-Noise Ratio concept sounds kind of daunting and maybe not so easy to understand, but it’s the essence of a receiver if you’re trying to pick up a weak signal as we do in telemetry a lot. Only one thing stops you from picking up the weakest signal, and that is the amount of noise introduced by the first stages in the receiver. Think about it: if you have a weak signal out there and it’s coming through a good antenna, and suppose you had no noise introduced in your receiver, then it’s simply a matter of amplifying and amplifying until you can hear that weak signal, and that’s very easy to do. But unfortunately there’s always a white noise, that hiss you hear from the receiver, caused by thermal vibrations in the very semiconductors and metals themselves and that hiss is your enemy. It gets amplified along with the signal and ends up obscuring it. You try to amplify the weak signal to no avail. But if you can reduce that noise, then you can amplify and hear weaker signals, so the Signal-to-Noise Ratio is the only measure of how good a receiver is at picking up a weak signal.
Also, in a programmable receiver where you can select your own frequency, you need to have a special kind of oscillator, and inherent in those oscillators is that they generate a lot of noise, which is called “phase noise.”

Interviewer: So this limitation is found in all other receivers, yet you’ve been able to overcome this somehow?

DLM: "Yes, by using new semiconductors, more expensive ones, and the right design parameters and filtering mechanisms, which is all why I used the word breakthrough to describe what we’ve done. With the phase noise, we’ve also taken exhaustive steps to ‘corral’ that and contain it in its own private little place so it cannot spread out and affect channels that are getting amplified. Any receivers on the market that are described as 'synthesized receivers' are limited by this problem."

Interviewer: So is this as sensitive as anything available in the market?

DLM: "Well we compare it to our Stealth. The Stealth receiver that we’ve been producing for the last 8 years or so has always come out on top of any test for sensitivity that we’ve made against any other receiver. “Sensitivity” is another term for the Signal-to-Noise Ratio, or the ability to detect a weak signal. And this new receiver is the same as the Stealth in terms of sensitivity but at a much lower cost. That’s one of the things I should have mentioned earlier that by modernizing and updating a lot of the circuitry, we’ve been able to substantially lower the cost and make it more affordable than the Stealth was."

Interviewer: How is this different from what some call a noise-blanker?

DLM: "A noise blanker is kind of a simple, more primitive approach to just cutting out certain types of noise in the form of big spikes and sudden jumps in the signal level, like noise from car ignitions. But here we’re talking about the more subtle and insidious type of noise, and that’s much harder to overcome than by just using a noise blanker. This white noise is pervasive and it’s mathematically intractable if you’re trying to use simple approaches to getting rid of it."

Interviewer: Can you increase that sensitivity by adding a “preamplifier” on your antenna?

DLM: "Yes, you can. With a receiver that has a poor front-end, you can improve the sensitivity by adding a low noise pre-amplifier. But it isn’t needed with the Field Marshall. It’s kind of a hassle to add an extra piece of equipment, which is why we built it in."

Interviewer: How much of this receiver, then, is completely new?

DLM: "Let me think, I need to do some math . . .  I’d have to say . . . 100%. Starting at the antenna, we took the basic idea of our collapsible yagi antenna which has been very successful over the last ten years and had been very reliable in the field and made it that much more robust and stronger, and more attractive as well. So we’ve gotten rid of the large springs, the pulleys the cables and just streamlined and everything a lot. So you’ll see those differences right away if you’re familiar with our previous antenna."

Inside the receiver, we compressed everything, made the case more rounded and ergonomic, taking advantage of the smaller size and the placement of all the parts inside. We completely changed all the electronics inside the receiver. It looks somewhat similar from the front but inside are all new circuit boards with all brand new parts, all parts that will be available a long time into the future since they’re fairly new designs. And of course in the process we did a few of these magical things to the circuit to improve the performance, improve the range the filtering the pleasantness of the sound and so forth. Those high tones sound sweet as honey."

Interviewer: What makes your yagi so directional? Tell us how you designed your yagi antenna.

DLM: "Well, anyone can throw together a yagi and you can come up with a usable antenna. ‘Homemade’ is the norm among HAMs (Amateur Radio enthusiasts). But if you really want to get a high-performance antenna, you need to spend some extensive time optimizing things. By that I mean the length of every element, the spacing between the elements and the tuning of the matching circuitry and a bunch of things. But the catch is that if you change one of those things, then you have to go back and redo it for all the other ones. It’s just very tedious to get it just right, and that’s why people don’t typically do this. I personally spent weeks outdoors, in lots of hayfields in Malad, Idaho, because the radio noise was quiet there. I remember having bees and grasshoppers on me for days on end…"

Interviewer: Why do you have to be out in a field, for so many days, doing this?

DLM: "Well, we did a lot of computer modeling in advance to kind of get a general idea of the directions we wanted to go, but in the end you don’t trust anything but field trials."

Interviewer: How much do can you really achieve with all this antenna tuning?

DLM: "There’s a trade off between several basic things in antenna tuning. A key one is the front-to-back ratio. That is, how strong the signal is picking up in the forward direction, the direction you want to go versus the unwanted response you get in the reverse direction. Unfortunately in all antennas there’s an unwanted signal from the back that throws people off sometimes to go 180 degrees from where the target really is. But if you minimize that then you also degrade the gain or the magnifying ability of the antenna. So we try to find a good compromise and we try to avoid the side lobes and to get the sharpest beam, which gives you your pinpoint accuracy."

Interviewer: I see here you refer to this new receiver as ‘The Quiet One.’ Wouldn’t most people say that a receiver needs to be loud?

DLM: "Well, you do hear your signal very loud. What you don’t hear is a lot of background noise and this is because of our special filtering. You’ll find that this receiver is especially good at lowering the noise picked up from sources, like TV broadcasting stations which is a terrible source of interference. We’ve been able to use this special filtering technology, the polyphase filters, to lower all that noise and the end result, what you hear, is a clean, loud signal and that’s the ideal thing to be hearing."

Interviewer: Someone new to this receiver might be alarmed if they turn it on, then turn up the volume expecting to hear the loud hissing sound, to gauge how loud the speakers are.

DLM: "What you want to do is first turn on a transmitter and then turn it up all the way and see how it sounds. What you’ll hear is a very loud signal. Again, noise is the number one enemy of a receiver in terms of being able to pick up over a long range. So, it’s a beautiful thing, having a quiet receiver."

Interviewer: What is a polyphase filter?

DLM: "I really can’t explain that, since it would give away our whole secret."

Interviewer: All tracking receivers on the market today expressly warn about getting wet or even having any exposure to moisture. One company even suggests putting their receiver inside a plastic baggie if there’s any chance of rain getting on the receiver. What have you done to this new design to be able to be used outdoors?

DLM: "The biggest risk area with regards to water is getting it into the speaker, as most speakers are made of a certain kind of cloth type of cone. We went to a mylar cone which is entirely water resistant, and we covered it with water resistant speaker cloth as well, so we prevented water from getting through the speakers. But it’s not waterproof, and if you submerge it or if you hold it up so water can accumulate in the front panel area, water will go inside and eventually may stop it from working. You can freely use it in rain, but just keep the front panel shielded from the rain and hold the front down, so water doesn’t accumulate there."

Interviewer: If you happened to fall in a creek or drop it into a stream and totally submerge the receiver, then what?

DLM: "In the user manual we point out that you’d first want to turn it off, then take out the batteries because the batteries are going to swell up if they’re wet. And that’s a bad thing. Then set it down in a warm place, control panel end down, and let it dry out."

Interviewer: It seems like a lot of time, cost and effort to develop a new receiver. Why not just use one that’s already available in the market, like a Tracker or Wildlife Materials or some other and then do some modification to it?

DLM: "We’ve gone down that road before. We used to sell the Wildlife Materials receivers, the TRX1000, the TRX3 and 16, and they were fine receivers, we’d re-package them so they looked attractive, added our collapsible antenna and the pistol grip and so forth. But in the end it was always compromising one part or the other. We’ve now been producing our own receivers for eight or nine years and have learned a lot. And we just found the opportunity right now to start over yet again knowing that there are many, many new and spectacular developments in terms of  the core technologies that are here and available now these days. Wireless technology has just bloomed and taken off in the last ten years.

"It seems like it should be straightforward to design a receiver, and the basic idea is. But there are so many subtleties involved, little intricate things. We find out that if we move a certain component over one half inch we get a dramatic different response because of the proximity to this other part that’s way over there. A wire going this direction instead of that means it doesn’t pick up the magnetic field of that trace on the circuit board. I couldn’t even begin to list all the different trade-offs. We literally do hundreds and hundreds of tests on a product like this to find these little things. It takes us a lot of time, actually.

"Designing a new receiver is not something I’d want to go through very often. We have hundreds of pages of intricate notes and experimental results of ideas that we tried, and it just takes a huge part of your life and your brain capacity to go through a project like that. So we hope to make this new receiver design a core technology to which we’ll add new features in later versions."

Interviewer: We’ve talked about the insides, but it’s also clear a lot of thought went into packaging and reducing the size and clever ways for the user to re-configure it.

DLM: "You know that Marshall Radio Telemetry has always considered packaging a very high priority, and this receiver exemplifies that. It’s a delight to hold, it’s a delight to handle and a pleasure to use. And, to look at. We could have gotten by with a cheaper case with bent sheet metal and screws sticking out and a much cheaper antenna. But just take a look around at cars for example. Do you see cars that have square, metal box shapes? With screws poking out, without paint? Every car’s got paint on it, because that’s the minimum acceptable level that people will even buy. We just hope that’s the way customers will feel about packaging. And then they’ll quickly discover that what’s on the inside is just as great …"



General: Dual conversion, superheterodyne, synthesized receiver

Dimensions: Height 2 inches, width 3 inches, Length 14 inches

Weight: 2 pounds

Frequency Range:

1 MHz within either of the following ranges:

150.790152.490 MHz

173.300173.999 MHz

1 or 4 MHz within one of the following ranges:

216.000219.999 MHz

232.300237.999 MHz

432.000 435.999 MHz

Fine Tuning: +/- 1.3 KHz continuously variable w/ analog control

Center Frequency Variation relative to Specified Frequency: Less than +/- .5 KHz.

Long Term Frequency Drift: .2 KHz

Power Supply: 12-14 VDC through external power jack. 9V (internal, using six AAA batteries)

RF Impedance: 50 ohms

Sensitivity: Typical minimum discernable input level: -150 dBm. Input level for 10 dB S+N+D/N –131 dB maximum. Noise Figure: 2.5 dB typical with 50 ohm source.

Image Rejection: > 45 dB

Spurious Emissions: < .2 nW



Beam Width: 38 Degree 3dB Down Point

Gain: 6 dBd

Front to Back Ratio: 14 dB


Complete ma...
Complete matched system Complete matched system
New receive...
New receiver case is 30% narrower New receiver case is 30% narrower
Shipping bo...
Shipping box for new receiver Shipping box for new receiver
Holster in ...
Holster in the field Holster in the field
Side view w...
Side view with handle Side view with handle
View of han...
View of handle bracket attachment View of handle bracket attachment
Narrow desi...
Narrow design fits in the hand Narrow design fits in the hand
Simple anal...
Simple analog controls Simple analog controls
Removable H...
Removable Handle Removable Handle
Spare Parts...
Spare Parts kits included Spare Parts kits included
Each case i...
Each case is machined from aluminum Each case is machined from aluminum
Holster in ...
Holster in the field Holster in the field
Field Holst...
Field Holster included with every receiver Field Holster included with every receiver
Removable H...
Removable Handle Removable Handle
Softcase fo...
Softcase for the receiver Softcase for the receiver
Profile vie...
Profile view with handle off Profile view with handle off
Simple anal...
Simple analog controls Simple analog controls
Holster in ...
Holster in the field Holster in the field
Panel view ...
Panel view 2 Panel view 2
Take it all...
Take it all with you using the Field Holster Take it all with you using the Field Holster
Control pan...
Control panel view Control panel view
Profile vie...
Profile view Profile view
Full size t...
Full size three element yagi Full size three element yagi
BNC cable o...
BNC cable option to use Marshall yagi BNC cable option to use Marshall yagi

Price with discount $895.00
Sales price $895.00
Sales price without tax $895.00