Transponder Antenna Research Articles

Determination of Parameters of Radio Frequency Identification Transponder Antennas Dedicated to IoTT Systems Located on Non-Planar Objects

Integration of Radio Frequency Identification (RFID) technology with conductive textiles has greatly expanded the possibilities for creating smart devices that fit perfectly into the concept of the Internet of Things. The use of e-textiles for antenna manufacturing has enabled the development of a textronic RFID tag. Integration of such tags into products with often non-flat surfaces may result in exposure to changes in antenna geometry caused by bending. As a result, the antenna parameters may change, resulting in disruption of the entire tag operation. The authors, through simulation and experimental studies, analyzed the effects of bending the antennas of RFID tags operating in the HF (High Frequency) band.

Predator presence influences survival and behavior of translocated stream fish in ponds

Abstract Small artificial impoundments such as farm ponds have recently been recognized as potential habitat for threatened native fish species. However, factors influencing translocation or colonization success into these environments, including connectivity to stream networks and interactions with existing fish community, are largely unknown. In this study we conducted a controlled experiment to quantify the influence of piscivorous Largemouth Bass Micropterus salmoides on the survival of a translocated native minnow species that we used as a surrogate for federally endangered Topeka Shiner Notropis topeka. We translocated or released 100 Bluntnose Minnow Pimephales notatus into each replicate treatment ponds with and without Largemouth Bass in the summers of 2020 and 2021. Each minnow was implanted with a passive integrated transponder (PIT) tag. Translocated populations were monitored using stationary and mobile passive integrated transponder antennas and estimates of apparent survival and probability of detection for each pond were derived from open population mark-recapture models. Apparent survival was nearly two times higher in ponds without bass suggesting predation by bass leads to higher mortality. Additionally, probability of detection was nearly 10 times higher in ponds without bass, suggesting reduced movement of translocated minnows when bass were present. While the direct effect of mortality impacts translocated populations, the indirect effect of altered behavior may also be impactful on translocation success. These results confirm that Largemouth Bass can limit the success of translocated minnow species.

Novel application of two- and four-lobed noise-canceling passive integrated transponder antennas for tracking fish in areas of high ambient electromagnetic interference.

Passive integrated transponder (PIT) technology is a leading tool for tracking fish in freshwater systems. PIT is highly applicable for assessing fish passage at anthropogenic infrastructure (e.g., dams and floodgates); however, there are often complications in operating PIT antennas near these structures due to the ambient electromagnetic interference of metal and power-supply equipment. We designed a PIT antenna that is resistant to the effects of ambient electromagnetic interference (AEMI). This design uses lobes with balanced polarity within the antenna to neutralize AEMI within the vicinity of the antenna. This novel PIT antenna provides a more effective and cost-efficient option for researchers tracking fish in environments with high AEMI.

Estimating migration timing and abundance in partial migratory systems by integrating continuous antenna detections with physical captures.

Many populations migrate between two different habitats (e.g. wintering/foraging to breeding area, mainstem-tributary, river-lake, river-ocean, river-side channel) as part of their life history. Detection technologies, such as passive integrated transponder (PIT) antennas or sonic receivers, can be placed at boundaries between habitats (e.g. near the confluence of rivers) to detect migratory movements of marked animals. Often, these detection systems have high detection probabilities and detect many individuals but are limited in their ability to make inferences about abundance because only marked individuals can be detected. Here, we introduce a mark-recapture modelling approach that uses detections from a double-array PIT antenna system to imply movement directionality from arrays and estimate migration timing. Additionally, when combined with physical captures, the model can be used to estimate abundances for both migratory and non-migratory groups and help quantify partial migration. We first test our approach using simulation, and results indicate our approach displayed negligible bias for total abundance (less than ±1%) and slight biases for state-specific abundance estimates (±1%-6%). We fit our model to array detections and physical captures of three native fishes (humpback chub [Gila cypha], flannelmouth sucker [Catostomus latipinnis] and bluehead sucker [Catostomus discobolus]) in the Little Colorado River (LCR) in Grand Canyon, AZ, a system that exhibits partial migration (i.e. includes residents and migrants). Abundance estimates from our model confirm that, for all three species, migratory individuals are much more numerous than residents. There was little difference in movement timing between 2021 (a year without preceding winter/spring floods) and 2022 (a year with a small flood occurring in early April). In both years, flannelmouth sucker arrived in mid-March whereas humpback chub and bluehead sucker arrivals occurred early- to mid-April. With humpback chub and flannelmouth sucker, movement timing was influenced by body size so that large individuals were more likely to arrive early compared to smaller individuals. With more years of data, this model framework could be used to evaluate ecological questions pertaining to flow cues and movement timing or intensity, relative trends in migrants versus residents and ecological drivers of skipped spawning.

Optimized design of wide band polarization diversified compact microstrip transponder antenna for satellite communication

AbstractA major limitation of microstrip antenna is its narrow impedance bandwidth (1%–5%) which makes it unsuitable for the operation over C band, used for various satellite communications, Wi‐Fi devices, some surveillance, and weather radar systems. Furthermore, increasing bandwidth (BW) can cause a reduction in radiation efficiency and antenna gain making it unsuitable for some particular applications. Nonplanar and defected ground structures may provide enhanced BW but it also creates distorted radiation pattern, unwanted loss of power, and mechanical mounting hazard. Polarization diversity also gives flexibility in use for various applications. A unique compact dual band and Ultra‐Wide Band (viz., 4.29–5.32 and 6.04–8.77 GHz) and polarization diversified (viz., circular and dual polarization) perturbed square microstrip patch antenna has been proposed here overcome the above shortcomings. Innovative corner parasitic loading and shorting via implementation ensures the fulfillment of the above features with improved 24.45% and 33.75% BW.

Body condition metrics explain fish movement in experimental streams

AbstractBody condition refers to an array of physiological or nutritious states in animals, but body condition is typically measured using a single metric in animal behavior studies. In this paper, we conducted a three‐day laboratory study to evaluate whether metrics of body condition affected movement of wild‐caught creek chub (Semotilus atromaculatus) at 16 and 22°C. Movement was counted between two circular tanks connected by a straight corridor, which was equipped with a pair of passive integrated transponder antennas. Fish movement was most frequent during periods of darkness in a simulated photoperiod, and more mobile individuals consistently moved more frequently across the 3 days. In general, individuals in better body condition were more mobile than those in poorer condition, and different metrics of body condition affected movement to different degrees. Specifically, per cent weight loss and dry matter content (ratio of wet versus dehydrated weight) were better predictors of movement than weight‐at‐length, which is most typically used as a surrogate of body condition in animals. In addition, body condition and length interacted to affect fish movement, where body condition affected movement of smaller individuals more significantly than that of larger individuals. Body condition effects on activity were similar at 16 and 22°C. This study demonstrates that body condition metrics may not always affect certain behavior in a similar way. Body condition metrics need to be carefully selected when used in the context of animal behavior, and more than a single metric should be tested when feasible.

A perched culvert and natural obstructions limit fish dispersal in an intermittent prairie stream

Poorly constructed road crossings block upstream movement of fish into stream reaches that provide critical habitat or connect isolated populations. Although removing these barriers is often a conservation priority, quantifying fish passage following removal has not been well studied, particularly in intermittent streams. In this study, we sought to understand how barriers influence the dispersal of fishes in intermittent prairie streams. We used passive integrated transponder tags and antenna stations to quantify fish movement of 3 prairie-stream fishes (Central Stoneroller Campostoma anomalum [Rafinesque, 1820], Southern Redbelly Dace Chrosomus erythrogaster [Rafinesque, 1820], and Creek Chub Semotilis atromaculatus [Mitchill, 1818]) through a road crossing in an intermittent prairie stream for 3 y before and 3 y after removing a perched culvert. We verified that no upstream fish movement occurred through the culvert, despite large aggregations of tagged fish in the intermittent reach below the culvert. In contrast, tagged individuals of all 3 species were detected above the road crossing in each of the 3 y following removal. We also tracked the recovery of these species, plus the Orangethroat Darter Etheostoma spectabile (Agassiz, 1854), following a severe drought in 2018 in 2 spring-fed tributary reaches, 1 without a downstream barrier and 1 with the removed downstream culvert. Surveys of the tributary reaches showed rapid recovery of fish densities following drought in the tributary without a downstream barrier. However, recovery at the site above the removed culvert appeared to be limited by a natural waterfall. Our observations suggest barrier removal allowed access to spawning habitat within the intermittent reach immediately upstream of the site, but other obstacles or shear distance to perennial spring-fed tributary reaches also limited recolonization following severe drought. Increased connectivity between perennial and intermittent reaches in prairie streams likely benefits fishes by increasing their resilience following disturbance and providing habitat during critical life stages.

A Small Warm Tributary Provides Prespawning Resources for Colorado Pikeminnow in a Cold Dam-Regulated River

Abstract Riverine habitat mosaics, including tributaries, are an important reason the Green River subbasin supports the largest remaining population of federally endangered Colorado Pikeminnow Ptychocheilus lucius in the Colorado River Basin. Upstream Colorado Pikeminnow distribution is limited by Flaming Gorge Dam and few typically occurred in the reach immediately downstream of the dam, which is the reach most affected by thermal and hydrologic alterations. However, fish captures and passive integrated transponder (PIT) antenna sampling of previously tagged individuals from 2011 to 2021 revealed seasonal congregations of up to 75 Colorado Pikeminnow annually in the mouth of Vermillion Creek, a small tributary in the regulated reach. Approximately 11% (N = 93 individuals) of the entire 2017–2018 Green River basin population were encountered in Vermillion Creek over the 11-y study, an underestimate of use considering that untagged fish were not detected by antennas. Colorado Pikeminnow used Vermillion Creek primarily when Green River spring flows from Flaming Gorge Dam were high and cold in May through mid-June when the confluence was a large, deep backwater warmer than the main channel and supported forage fishes. Intra-annual encounters revealed seasonal residence times for individual Colorado Pikeminnow up to 91 d, and multiple inter-annual encounters indicated site fidelity. Frequent detections of individual Colorado Pikeminnow in a Yampa River spawning area soon after their detections in Vermillion Creek indicate this tributary may be an important resource for reproductive adults. The intensive and basin-wide PIT tagging and detection program for Colorado Pikeminnow enhanced our understanding of the importance of small habitat nodes such as Vermillion Creek in the Green River drainage network. Understanding and protecting these seasonally available riverine habitat mosaics used for prespawning conditioning may assist with recovery of Colorado Pikeminnow.

Upstream and Downstream Dispersal Behavior of Hard‐ and Soft‐Released Juvenile Atlantic Salmon

AbstractFailure of reintroduction efforts of extirpated populations is thought to be linked to maladaptive behaviors exhibited by captive‐bred individuals in the environment where they are released. Soft‐release conditioning tactics attempt to reduce maladaptive behaviors by providing reintroduced animals an acclimatization period prior to release. We used implanted passive integrated transponder tags and antennae to monitor the spatial and temporal dispersal behavior of captive‐bred Atlantic Salmon Salmo salar that were acclimatized for 6 d prior to release (soft‐release), with fish that were directly released (hard‐release) into East Duffins Creek in Ajax, Ontario, Canada. In total, 232 of the 610 tagged fish (38%) dispersed from the release site. Downstream spatial dispersal did not differ significantly between the hard‐release (32%, n = 98 of 310) and soft‐release fish (30%, n = 91 of 300), but the hard‐release fish were significantly more likely to move upstream (11%) than were the soft‐release fish (3%). Timing of dispersal also significantly differed between the two groups: soft‐release fish were detected dispersing, on average, approximately 15 d earlier than hard‐release fish. These results suggest that soft‐release tactics do affect dispersal behavior, and the findings will be of particular interest to fisheries management agencies that are charged with improving the success for stocking salmonids as part of reintroduction efforts.

Comparison of Electrofishing and PIT Antennas for Detection of Hatchery-Reared Roundtail Chub (Gila robusta) Stocked into a Desert Stream

Stocking of rare native fishes for conservation purposes is a common practice in the southwestern United States. Monitoring typically occurs after hatchery-reared fish are released to assess post-stocking movement and survival. We conducted a two-year study, in which tow-barge electrofishing and portable, flat-bed passive integrated transponder (PIT) antennas were used to monitor PIT-tagged, hatchery-reared roundtail chub (Gila robusta) following release into the upper Verde River in Arizona. Specifically, our study aimed to compare the performance of PIT antennas and electrofishing in detecting PIT tagged fish released in a small desert river and to examine the behavioral response of hatchery-reared roundtail chub after stocking. In both years, more fish were detected by antenna arrays (84%) than by electrofishing (30%). roundtail chub were significantly more likely to be detected by antennas than electrofishing each year; however, when antenna data were evaluated only during the few days in which electrofishing took place, there was no significant difference (Year 1, p=0.1784; Year 2, p=0.6295) in detection between gear types for the same time interval, suggesting that electrofishing and antennas are equally likely to detect fish during 48-72 hour time frames. Within 72 hours of release, antennas detected 100% of fish that moved upstream and 93.8% of fish that moved downstream from the stocking location. Overall, less than half (45.6% in Year 1; 41.1% in Year 2) of the stocked roundtail chub were detected using both methods in both years. Utilization of both active capture gear (electrofishing) and passive gear (antennae) had advantages over monitoring with a single method. PIT antennae can be especially useful for managers who lack the personnel or time to implement more intensive methods of capture but want to monitor post-stocking movement and survival of stocked fish.

Simulation Analysis of Transponder Power Based on Target Flight Trajectory

The directional angle of the exterior trajectory measurement equipment in the transponder antenna coordinate system is an important basis for interpreting the transponder antenna gain, analyzing the uplink and downlink power of the transponder, and evaluating the measurement and tracking ability of the equipment. The mathematical model established in this paper deduces the direction angle of the exterior trajectory measurement equipment in the transponder antenna coordinate system according to the track information of the flight target, and then obtains the transponder power received by the exterior trajectory measurement equipment combined with the installation position of the transponder, the antenna pattern and the secondary radar formula. It can effectively evaluate the tracking ability of the equipment in measuring segment and adjust the working state of the equipment according to the actual situation. At the same time, it provides a theoretical basis for the ground measurement equipment to receive the transponder power is too low, resulting in the measurement data accuracy is not up to standard, or even lost.

Design and Simulation of Microstrip Patch Single Element, 1*2 Array Design and 1*4 Array Design for SART Applications

The Search and Rescue Transponders are used to search for the lost ship and aircraft. The transponder antenna resonates at the frequency of 9 GHz. The design is considered using FR4 (Flame Retardant) substrate of dielectric constant 4.4 and loss tangent 0.0019. A micro strip line fed rectangular patch antenna is designed in such a way that it resonates at 9 GHz. The return loss and gain for the designs are, Single Element Design: Return Loss is -24.291 dB, Gain Total is 5.9083 dB, 1*2 Array Design: Return Loss is -19.3635 dB, Gain Total is 8.5915 dB, 1*4 Array Design: Return Loss is -34.4773 dB, Gain Total is 9.4879 dB. Other antenna parameters such as VSWR, Radiation Efficiency, Gain 2D, Specific Absorption Rate are observed. The antenna structure is simple, flat and straightforward. The design can be embedded easily in Search and Rescue Transponder Transmitter because it is geometrically small. The simulation and analysis were done using High Frequency Structure Simulator (HFSS).

Passage Performance of Technical Pool-Type Fishways for Potamodromous Cyprinids: Novel Experiences in Semiarid Environments

Endemic freshwater fish from semiarid environments are among the most threated species in the world due to water overexploitation and habitat fragmentation problems. Stepped or pool-type fishways are used worldwide to reestablish longitudinal connectivity and mitigate fish migration problems. Many of them are being installed or planned in rivers of semiarid environments, however, very few studies about fish passage performance through pool-type fishways has been carried out to date on these regions. The present work focuses on the passage performance of two potamodromous cyprinids endemic of these regions, with different ecological and swimming behavior: southern Iberian barbel (Luciobarbus sclateri) and Iberian straight-mouth nase (Pseudochondrostoma polylepis). These are assessed in two of the most common types of stepped fishways: vertical slot and submerged notch with bottom orifice fishways. Experiments were carried out during the spawning season in the Segura River (southeastern Spain), using a passive integrated transponder (PIT) tag and antenna system. Ascent success was greater than 80%, with a median transit time lower than 17 minutes per meter of height in all trials, and for both species and fishway types. Results show that both types of fishways, if correctly designed and constructed, provide interesting alternatives for the restoration of fish migration pathways in these regions.

Integrating PIT technology into gear evaluation in an unregulated desert tributary

Fish characteristics and behavioral response to gear influences catchability. Monitoring of native fishes including bluehead Sucker Catostomus discobolus, flannelmouth Sucker Catostomus latippinis, and the endangered humpback chub Gila cypha occurs throughout the Grand Canyon and its tributaries. To quantify species-specific conditional capture probability (p^ ; probability of capturing an individual fish being conditional on the individual occupying the site), we placed a flat plate passive integrated transponder (PIT) antenna 1.5 m downstream from a hoop net and processed fish during monitoring activities for three years (2011–2013). The capture probability was conditional on fish presence as determined by PIT tag detection from the flat plate antenna. We used logistic regression to test for effects of trap response, and a non-parametric bootstrap routine was used to evaluate differences in p^ among years and fish species. Pooled p^ was similar between humpback chub (mean = 0.10, 95% CIs = 0.04–0.20) and flannelmouth sucker (mean = 0.13, 95% CIs = 0.05–0.26), while bluehead sucker were never recaptured (p^ = 0). Integrating antennas into gear evaluation has broad implications to other systems as this approach could be used to standardize catch rate estimates among different passive entrapment gears of various sizes, and among different habitat types. Obtaining catchability estimates among gear types is useful when assessing modifications to long-term monitoring programs and key to stock assessment. Here, we integrated PIT tags and antennas into gear evaluation to quantify conditional capture probability, and provided a test-of-concept for larger, broader studies that can use the underlying principles and techniques shared in this study.

Beaver activity increases habitat complexity and spatial partitioning by steelhead trout

Freshwater habitat restoration is a major conservation objective, motivating efforts to restore habitat complexity and quality for fishes. Restoration based on the engineering activities of beavers (Castor canadensis) increases fish habitat complexity, but how this affects fish habitat use and movement behaviours is not well known. We used a network of passive integrated transponder antennas to quantify small-scale movement and microhabitat use of 175 individual juvenile steelhead (Oncorhynchus mykiss) in a stream channel with a complex bathymetric profile resulting from a beaver impoundment and in a simplified channel devoid of beaver activity. Our results show that juvenile steelhead exploit microhabitat heterogeneity by employing a range of behaviours that maximizes available habitat via spatial and temporal partitioning among individuals. These results suggest spatial resource partitioning as a potential mechanism for the previously established positive correlations among steelhead density, survival, and production with beaver-based restoration within the study watershed. More broadly, our findings provide insight as to how populations can exploit habitat complexity through spatial partitioning that can be informative for planning restoration and management actions.

Passage performance and behaviour of wild and stocked cyprinid fish at a sloping weir with a Low Cost Baffle fishway

Weir construction has fragmented many rivers, resulting in the exclusion of some fish populations from suitable habitat. A cheap retrofit fishway for small, sloping weirs is the Low Cost Baffle (LCB) solution – A series of notched baffles perpendicular to flow on the downstream weir face, generating an angled passage route across the weir face. To test the degree to which LCBs can pass upstream-moving, lowland-river fish at steep weirs, LCBs were fitted onto a 1:3.3-sloping gauging-weir face, in an urban tributary of the River Thames, England. The study also compared the passage of wild and stocked fish (the latter are employed to facilitate population recovery in restored English rivers). Passive Integrated Transponder (PIT) antennas were positioned on the weir to record the upstream movement of PIT-tagged barbel (Barbus barbus; nstock = 120), chub (Squalius cephalus; nstock = 119; nwild = 194), dace (Leuciscus leuciscus; nwild = 50), and roach (Rutilus rutilus; nwild = 30). Over six months, more stocked fish attempted passage (58.9%) than wild (14.6%; χ21 = 26.7, p < 0.001), but there was no difference in successful passage of those that attempted (stock = 34.0%; wild = 40.0%; χ21 = 0.5, p = 0.49). Successful passage was achieved under a range of flow conditions. This study finds that LCBs have the potential to facilitate passage for cyprinid fishes at steep urban weirs that cannot readily be removed, but there is need for design improvements. This study also indicates that stocked and wild fish exhibited similar passage success, a finding with important management implications for achieving dispersal of stocked fish as a rehabilitation measure.

Fine-scale movement and habitat use of a prairie stream fish assemblage.

Measuring an organism's movement and habitat use is highly dependent on the spatial and temporal scale of the study, with most studies measuring distributions once a day or at less frequent intervals. Yet, to fully understand the rates of intra- and interspecific encounters among individuals, observations at finer spatial and temporal scales might be necessary. We used passive integrated transponder tags and antenna arrays to continuously monitor habitat use and vagility of three stream minnows; southern redbelly dace Chrosomus erythrogaster, central stoneroller Campostoma anomalum, and creek chub Semotilus atromaculatus, among and within pools of an intermittent stream. Most fish remained in the pool where they were caught and released, or returned after emigrating from the pool. Despite largely remaining within the release pool, distribution among four microhabitats differed significantly over six, 4-h time periods for all three species. Vagility, the summed distance moved among antennas, differed significantly among species. Individual vagility (mday-1) increased significantly with body length for stoneroller and chub, but not dace. Some individuals moved as much as 110mday-1 within the pool, showcasing extensive movement at fine scales. Finally, we found no evidence that feeding activity changed as a result of differential habitat use over a 24-h period. Our findings indicate considerable variation in habitat use and movement occurs among species over a 24-h period. This suggests ecologists can broaden the interpretation of processes influencing community structure (e.g., resource partitioning, avoidance of predators) by quantifying species distributions across a range of spatial and temporal scales.

Patterns of fish movement at a desert river confluence

AbstractQuantifying fish movements in river networks helps identify critical habitat needs and how they change with environmental conditions. Some of the challenges in tracking fish movements can be overcome with the use of passive integrated transponder (PIT) tagging and antennas. We used PIT technology to test predictions of movement behaviour for four fish species at a mainstem–tributary confluence zone in an arid‐land river system. Specifically, we focused on the McElmo Creek tributary confluence with the San Juan River in south‐western Utah, USA. We quantified variation in species occurrences at this confluence zone from May 2012 to December 2015 relative to temporal and environmental conditions. We considered occurrences among species relative to tagging origins (tributary versus mainstem), season and time of day. Generally, fishes tagged in the focal tributary were more likely to be detected compared to fish tagged in the mainstem river or other tributaries. Additionally, adults were most likely to be detected across multiple years compared to subadults. Based on a Random Forests model, the best performing environmental variables for predicting seasonal detections included mainstem discharge during run‐off season (razorback sucker Xyrauchen texanus), tributary discharge during monsoon season (Colorado pikeminnow Ptychocheilus lucius) and mainstem water temperature (flannelmouth sucker Catostomus latipinnis and channel catfish Ictalurus punctatus). The variable responses by endemic and introduced fishes indicate tributary habitats provide several key functions within a fish community including spawning, rearing, foraging and refuge.

Summer habitat and movements of juvenile salmonids in a coastal river of Washington State

AbstractWe investigated the summer ecology of juvenile steelhead trout Onchorhynchus mykiss and Chinook salmon O. tshawytscha in the context of habitat use and movement behaviour. The study area was a 14.8 km section of the Chehalis River, Washington, and is of particular interest due to recent proposals for both a flood retention dam and restoration actions in this watershed. Ten study reaches were paired in distance upstream and downstream from a central point where a passive integrated transponder antenna array was operated between late June and September 2014. Juvenile densities for each species were associated with reach‐scale habitat and temperature characteristics. Juvenile steelhead underwent upstream and downstream movements up to 7 km, although more fish from further away moved downstream than upstream. Juvenile steelhead repeated horizontal movements throughout the study period, but daily detections were not associated with temperature or flow. The majority (81%) of steelhead movements occurred between the hours of 04:00–07:00 and 18:00–21:00. Juvenile Chinook underwent a downstream migration that was nearly complete by the end of August. Most juvenile Chinook were detected just once and movements occurred on days with warmer stream temperature and higher flows. The majority of Chinook movements occurred at night. Although juvenile salmonids are often thought to have small home ranges during summer months, our results suggest that horizontal movements may be more prevalent than previously thought. Summer habitat should be defined by a network of suitable rearing reaches with connectivity available in both upstream and downstream directions.

Evaluating Path Loss by Extended Squitter Signals for Aeronautical Surveillance

For the successful deployment of the aeronautical surveillance systems, it is important to select the appropriate path loss model that is used in the coverage design. While the flight experiment is a traditional approach to evaluate the path loss models, the passive measurement of the 1090-MHz extended squitters (1090 ESs) broadcast by target of opportunity is a new complementary approach. This letter examines the feasibility of the 1090 ES measurement for evaluating the aeronautical path loss models. First, the effect of the alternate transmission using two transponder antennas is removed to extract the effect of the propagation channel. Then, the measurement result during the flight experiment is compared to the reference values given by free-space path loss in order to show the relevance of using the 1090 ES.