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JustStan a48758a943 Initial commit: OpenVTX project setup

Open-source 5.8GHz analog VTX with software-defined OSD based on OpenOSD-X firmware.
KiCad 9 project with complete component library (14 symbols, 14 footprints, 13 3D models),
all datasheets, reference schematics, and design documentation ready for schematic capture.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

2026-03-26 14:44:38 +01:00

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Analog FPV VTX Market Analysis (2025-2026)

Research compiled March 2026 for open-source VTX design reference.

1. Current Top VTX Products

Premium Tier ($25-40)

Product	Power	Size	Weight	Connector	Protocol	Input V	Price
TBS Unify Pro32 HV	25-1000mW	Compact standalone	~6g	MMCX	SmartAudio, Crossfire, USB	7-36V (2-6S)	~$35-40
TBS Unify Pro32 Nano	25-500mW+	Ultra-compact	~2g	MMCX	SmartAudio, Crossfire	7-36V	~$30
Rush Tank Solo	PIT/25/400/800/1000/1600mW	37x24x6.7mm	12g	MMCX	SmartAudio V2.1	7-36V (2-6S)	~$30-35

Mid-Range Tier ($15-25)

Product	Power	Size	Weight	Connector	Protocol	Input V	Price
Rush Tank Mini	25-800mW	20x20mm	~4g	MMCX	SmartAudio	7-36V	~$20
HGLRC Zeus VTX PRO 1.6W	PIT/25/400/800/1600mW	25x37x6.5mm	13g	MMCX	SmartAudio	7-36V	~$22
HGLRC Zeus 800mW	PIT/25/100/200/400/800mW	37x37x5mm (20x20/30x30)	4.8g	MMCX	SmartAudio	7-36V	~$18
SpeedyBee TX800	25-800mW	20x20mm	2.6g	u.FL	SmartAudio	5V only	~$15
SpeedyBee TX1600 Ultra	25-1600mW	Standalone	~10g	MMCX	SmartAudio	7-36V	~$22
RDQ Mach 3	25-1000mW	20x20mm	~4g	MMCX/u.FL	SmartAudio	7-36V	~$20

Budget Tier ($8-15)

Product	Power	Size	Weight	Connector	Protocol	Input V	Price
AKK Race	25-200mW	Compact	~2g	u.FL	SmartAudio	5V	~$10
Eachine Nano VTX V3	25-400mW	Nano	~2g	u.FL	SmartAudio/Tramp	5V	~$10
Eachine TX805	25-800mW	Compact	~5g	SMA	SmartAudio	7-24V	~$13
BetaFPV A03	25-400mW	16x16/20x20	~2g	u.FL	OpenVTx/SmartAudio	5V	~$12

Micro/Whoop Tier

Product	Power	Size	Weight	Connector	Protocol	Price
Rush Tiny Tank	25-350mW	12.5x17mm	1.4g	u.FL	SmartAudio	~$15
HGLRC Zeus Nano	25-350mW	16x16/20x20/25.5x25.5	~1.5g	IPEX/u.FL	SmartAudio	~$12

High-Power / Long-Range

Product	Power	Connector	Notes	Price
Foxeer Reaper Extreme	2500mW	SMA	Includes fan/heatsink, massive heat	~$35
AKK Race Ranger 1.6W	PIT/25/400/800/1600mW	MMCX	Used in military FPV drones	~$20
AKK X2 Ultimate	25-1200mW	MMCX	Long-range budget option	~$18

Key Observations

TBS Unify Pro32 is the "gold standard" -- clean signal, honest power ratings, but most expensive
Rush has eaten significant market share with competitive quality at lower prices
HGLRC Zeus line dominates budget-to-mid segment
Chinese manufacturers (AKK, HGLRC, SpeedyBee) have driven prices down dramatically
The 800mW sweet spot serves 90% of pilots; 1.6W is niche for long-range

2. Feature Comparison: Premium vs Budget

Feature	Premium (TBS/Rush)	Budget (AKK/Eachine)
Signal cleanliness	Clean, minimal bleed to adjacent channels	Often "dirty," interferes with nearby pilots
Power accuracy	Honest rated output	Often overstated by 20-50%
Frequency accuracy	Precise, tight tolerance	Can drift, especially when hot
Build quality	Aluminum enclosures, conformal coating	Bare PCB, no protection
Thermal management	Integrated heatsink/case	None or minimal
Pit mode	Reliable, <1mW	Often unreliable or absent
Connector quality	Solid MMCX	Cheap u.FL that detaches in crashes
Firmware updates	USB/SmartAudio updates	Usually none
Audio/microphone	Built-in mic on some	Rarely included
Voltage range	Wide (2-6S direct)	Often 5V only (needs external BEC)

3. Common Complaints from Pilots

Signal Quality

Cheap VTXes bleed into adjacent channels, ruining group flying / races
Electrical noise from ESCs causes video noise on throttle-up
Power filtering on budget VTXes is inadequate
Actual output power often doesn't match rated specs

Heat

VTXes overheat on the bench without airflow (especially >400mW)
Overheating causes reduced range, video degradation, and permanent damage
High-power VTXes (1W+) get dangerously hot even in flight
No thermal shutdown protection on most units

Connectors

MMCX connectors deemed "the worst" by some pilots -- can be pulled out in crashes
u.FL connectors pop off in flight or after crashes
SMA is robust but too large/heavy for modern builds
No universally loved connector exists

Reliability

Powering VTX without antenna attached = instant death for most units
Water/moisture ingress kills VTXes
Crash damage is common, especially to antenna connections
Budget VTXes (especially Eachine) have poor longevity

Configuration

SmartAudio and Tramp are proprietary and sometimes flaky
Protocol detection can fail, leaving VTX unconfigurable
No standardized way to configure without FC (standalone config)
Button-based channel/power selection is tedious and error-prone

Size/Weight

High-power VTXes are too large for tight builds
Mounting pattern variety means adapters are often needed
Stack-mount VTXes add height to already tall FC stacks

4. Power Levels

Common Power Steps

Level	Typical Use	Range (approx)
PIT (<1mW)	Pits at races, bench testing	~5m
25mW	Indoor, whoops, racing pits	~200m
200mW	Park flying, casual freestyle	~500m
400mW	Freestyle, general purpose	~1km
800mW	Long-range freestyle, penetration	~2-3km
1000mW (1W)	Long-range	~3-5km
1600mW (1.6W)	Long-range dedicated	~5km+
2000-3000mW	Extreme long-range (AKK)	~10km+

What Pilots Actually Use

Racing: 25mW (mandatory at events) with pit mode
Freestyle: 400-800mW most common
Long-range: 800mW-1.6W
Whoops/micro: 25-200mW
Most common default: 400mW -- good balance of range and heat

Regulatory Notes

US: 1W (1000mW) limit without HAM license on 5.8GHz
EU: 25mW limit in many countries (widely ignored in practice)
HAM license allows higher power in most jurisdictions
Many VTXes ship with "US" and "international" firmware variants

5. Form Factors

Mounting Patterns

Pattern	Use Case	Notes
16x16mm	Micro/whoop builds	Tiniest builds, usually low power
20x20mm	Standard racing/freestyle	Most popular for 3-5" quads
25.5x25.5mm	Some racing frames	Less common, legacy
30x30mm (30.5x30.5)	Larger builds, long-range	Higher power VTXes
Standalone (no stack)	Anywhere, zip-tied/taped	Rush Tank Solo style, aluminum case

Antenna Connectors

Type	Size	Durability	Mating Cycles	Use Case
SMA/RP-SMA	Large	Excellent (500+)	500+	Legacy, long-range, ground stations
MMCX	Medium	Good	~500	Standard for 5" builds, replacing SMA
u.FL (IPEX)	Tiny	Poor	~30	Micros/whoops only, fragile

Connector Trends

MMCX is now the dominant standard for 5" builds
u.FL accepted only on micro/whoop builds where weight matters
SMA being phased out on quad VTXes but still used on ground-side
Some pilots solder antenna pigtails directly to avoid connector failures

6. VTX Control Protocols

SmartAudio (TBS)

Developer: Team BlackSheep
Versions: V1.0, V2.0, V2.1, Lite
Connection: Single-wire (TX pin of UART)
Features: Change channel, band, power, pit mode via Betaflight OSD
Market share: Dominant -- most VTXes support this
Issues: Proprietary, version fragmentation, power levels use coded values (not mW)

IRC Tramp (ImmersionRC)

Developer: ImmersionRC
Connection: Serial (UART TX+RX)
Features: Same as SmartAudio but sends power in mW directly
Market share: Declining, mostly ImmersionRC and some budget VTXes
Issues: Less widely supported, dying out

MSP (Betaflight native)

Developer: Betaflight / OpenVTx
Connection: Serial UART
Features: Vendor-neutral, self-configuring VTX tables, auto-detection
Status: Preferred protocol from Betaflight 4.4+ and OpenVTx 0.2+
Advantage: No proprietary lock-in, VTX can push its own capability table to FC

ExpressLRS Serial VTX

Connection: Via ELRS receiver serial passthrough
Features: Control VTX settings through ELRS link
Status: Growing adoption

Recommendation for Open-Source Design

MSP should be the primary protocol, with SmartAudio V2.1 and Tramp as fallback for legacy compatibility. MSP is vendor-neutral, self-describing, and the direction Betaflight is heading.

7. OSD Integration

Current State

FC-integrated OSD is the universal standard -- MAX7456/AT7456E chip on the FC overlays telemetry onto analog video
Standalone OSD boards (MinimOSD) are dead/legacy
VTX with built-in OSD is rare and generally unwanted -- pilots want FC OSD
The VTX just passes video through; OSD overlay happens on the FC

What Pilots Want

VTX should NOT have built-in OSD (adds cost, complexity, potential failure)
Clean video passthrough from camera to antenna
FC handles all OSD via MAX7456/AT7456E chip
VTX status (channel, power, pit mode) displayed via Betaflight OSD menu

Exception: tinyFINITY / All-in-One

fishpepper's open-source tinyFINITY combines VTX + OSD on 16x16mm board
Uses STM32F3 + RTC6705, software OSD (35 chars x 13 lines, 8 gray levels)
Draws only 10mA for OSD vs 120mA for MAX7456
Niche: ultra-micro builds where FC doesn't have OSD chip

8. Pit Mode & Race Features

Importance: Critical for Racing

Pit mode reduces output to <1mW (~0.001mW, ~5m range)
Without pit mode, powering up a VTX in the pits blinds other pilots on adjacent channels
Required for organized racing (MultiGP, etc.)
Two variants:
- POR (Pit Out of Range): Transmits on fixed frequency 5584 MHz
- PIR (Pit In Range): Transmits on set frequency at minimum power

Race Features Pilots Want

Reliable pit mode on boot (not just via SmartAudio command)
Pit mode switch on transmitter (Betaflight mode switch)
Quick power switching without VTX restart
Clean signal that doesn't bleed into adjacent Raceband channels
Accurate frequency output (no drift under heat)

Raceband

8 channels spaced 37 MHz apart: 5658, 5695, 5732, 5769, 5806, 5843, 5880, 5917 MHz
Allows 6-8 pilots to fly simultaneously without interference
Cheap VTXes with dirty signals reduce usable pilot count

9. Heat Management

The Problem

VTXes at 800mW+ generate significant heat
PA (power amplifier) stage is the primary heat source
Operating above 80C degrades performance and shortens lifespan
On the bench with no airflow, high-power VTXes can fail in minutes

Current Solutions

Approach	Used By	Effectiveness
Aluminum enclosure as heatsink	Rush Tank Solo, TBS Unify	Good -- doubles as protection
Clip-on aluminum heatsink	SpeedyBee TX800, aftermarket	Moderate
Thermal pad to frame	DIY	Moderate -- uses carbon frame as sink
Active cooling fan	Foxeer Reaper Extreme	Best, but adds weight/complexity
Thermal throttling	TBS Crossfire Sixty9	Reduces power when hot
Bare PCB (nothing)	Most budget VTXes	Poor -- relies entirely on airflow

Design Recommendations

Aluminum enclosure with thermal pad coupling to PA is the best passive approach
Exposed copper pad on bottom of PCB for frame-mount heat sinking
Thermal shutdown protection should be standard (it currently isn't on most)
Auto-throttle power when temperature exceeds safe threshold
Temperature telemetry via MSP/SmartAudio would be valuable

10. Price Points Summary

Segment	Price Range	Typical Products
Ultra-budget	$8-12	AKK Race, Eachine Nano, no-name clones
Budget	$12-18	HGLRC Zeus Nano, BetaFPV A03, SpeedyBee TX800
Mid-range	$18-25	Rush Tank Mini, HGLRC Zeus 800/1.6W, SpeedyBee TX1600
Premium	$25-40	TBS Unify Pro32 HV, Rush Tank Solo
Extreme	$35-50	Foxeer Reaper Extreme, high-power niche

Key Pricing Observations

Analog VTX prices have collapsed -- $15-20 gets a very capable 800mW unit
TBS commands a premium based on reputation and signal quality
Chinese manufacturers have made high power (1.6W) available for ~$20
The entire analog VTX is often the cheapest component in a build
Digital VTX starts at $50+ (HDZero) to $100+ (DJI/Walksnail)

11. Frequency Agility

Standard Bands (5.8GHz ISM)

Band	Channels	Frequency Range	Notes
A (Boscam)	8	5865-5945 MHz	Legacy
B (Boscam)	8	5733-5866 MHz	Legacy
E (Lumenier)	8	5705-5945 MHz
F (ImmersionRC/FatShark)	8	5740-5880 MHz	Popular
R (Raceband)	8	5658-5917 MHz	Racing standard, 37MHz spacing

Channel Counts

40-channel: Standard (5 bands x 8 channels) -- A, B, E, F, R
48-channel: Adds extra bands (D, U, O, L, H) -- some outside legal allocations
37-channel (US locked): Only ITU Region 2 legal channels (5650-5925 MHz)
Unlocked: All 48+ channels available, user responsibility for legality

Regulatory Bands

US (ITU Region 2): 5.650-5.925 GHz -- Raceband fits, some upper A/B channels do not
EU: More restrictive, 25mW power limits in many countries
L/U/O bands: Often fall outside legal allocations; avoid for a legal product

Design Recommendation

Support all 40 standard channels (A/B/E/F/R) minimum
48-channel unlocked mode as optional firmware feature
Default to region-appropriate channel/power limits
Raceband is the most important band for competitive pilots

12. Reliability Issues / Common Failure Modes

Ranked by Frequency

No antenna = dead VTX -- Running without antenna load reflects power back into PA, burns it instantly. No consumer VTX has antenna detection/protection.
Crash damage to antenna connector -- u.FL pops off; MMCX can be ripped from pad
Overheating -- Prolonged high-power bench operation without airflow
Water/moisture ingress -- Rain, dew, grass landings
Solder joint failure -- Vibration cracks joints, especially on signal wires
Voltage spike damage -- LiPo voltage spikes on plug-in, inadequate input filtering
ESD damage -- Static discharge during handling
Firmware corruption -- SmartAudio misconfiguration leaving VTX in broken state

What's Missing in Current Designs

No antenna VSWR detection -- Could protect PA from no-antenna condition
No thermal shutdown -- VTX runs until it dies
No reverse polarity protection on most budget units
No brownout protection -- Voltage sag during flight causes VTX reset/reboot
No self-diagnostic capability -- No way to know if VTX is degraded

13. What's Missing -- Features Pilots Wish Existed

Hardware

Antenna detection / VSWR protection -- Refuse to transmit (or limit power) if no antenna detected
Thermal shutdown / auto-throttle -- Reduce power before burning out
Temperature telemetry -- Report VTX temp via MSP to OSD
Better connector than MMCX -- Something crash-resistant but still swappable
Conformal coating standard -- Weather resistance on all units
Integrated LC filtering -- Clean power input without external caps
On-board DVR -- Record analog video locally (exists on some digital, not analog)
Dual-band (5.8GHz + 1.3GHz) -- Niche but desired for long-range
True power calibration -- Factory-calibrated output power per channel

Firmware / Software

Open-source firmware -- OpenVTx exists but limited hardware support, last release Oct 2022
MSP as primary protocol -- Self-describing VTX tables, no proprietary lock-in
Web-based configurator -- USB-C direct config without Betaflight
Per-channel power calibration tables -- Compensate for frequency-dependent PA gain
Spectrum analyzer mode -- Use VTX receiver chain to scan 5.8GHz band
Smart power management -- Auto-reduce power near home, increase at range
Blackbox-style logging -- Record VTX state (temp, power, channel) for debugging

Quality of Life

Standardized mounting -- One board that fits 16x16, 20x20, and 25.5x25.5
LED status indicators -- Clear indication of channel, power, and pit mode
Audible beeper -- Help find downed quad (some Rush models have mic but no beeper)
Boot-to-pit-mode -- Always start in pit mode for race safety

14. Analog vs Digital Trend

Analog Is Still Relevant For:

Racing -- Cheapest, lightest, lowest-latency (though HDZero 540p@90fps now matches at 4ms)
Whoops/micros -- Weight matters; analog VTX can be <2g vs digital at 5-10g+
Budget builds -- Complete analog video system for ~$70 (goggles + VTX + camera)
Military/disposable drones -- Ukraine conflict drives massive demand for cheap analog VTX
Training/beater quads -- Cheap enough to not care about crashes
Legacy pilots -- Huge installed base of analog goggles

Digital Is Winning For:

Freestyle -- Image quality matters for enjoyment
Cinematic -- HD recording from goggles
Long-range -- Digital error correction outperforms analog at range edges
New pilots -- Digital is the default recommendation for newcomers in 2026

Analog declining but not dead; still ~30-40% of new builds (est. 2026)
HDZero gaining in racing due to low latency + HD
DJI O3/O4 and Walksnail dominate freestyle/cinematic
OpenIPC emerging as open-source digital alternative
Military demand (Ukraine) keeps analog production volumes high

Implications for Open-Source Analog VTX

There is a viable market, especially for:
- Racing (cost-sensitive, weight-sensitive)
- Military/commercial disposable drones
- Open-source/hackable community
- Education and DIY
The design should optimize for: low cost, reliability, clean signal, light weight
Don't try to compete with digital on image quality -- compete on cost, weight, openness, and reliability

15. Existing Open-Source VTX Projects

OpenVTx (Firmware Only)

Repo: github.com/OpenVTx/OpenVTx
Status: Last release v0.2.0 (October 2022) -- appears stalled
Features: MSP + SmartAudio + Tramp auto-detection, race mode (boot to pit)
Hardware: EWRF E7082VM (V1/V2) at 500mW max, limited board support
Language: C (75%) / Python (25%)
Gaps: Limited hardware support, no active development, no high-power boards

tinyFINITY (Full Hardware + Firmware)

Author: fishpepper.de
Hardware: STM32F3 + RTC6705, 16x16mm PCB
Features: Software OSD (35x13 chars, 8 gray levels, 10mA draw), full open-source
Limitations: Low power only (~20mW from RTC6705 internal PA), no external PA, micro-only

OpenHD

Focus: Digital FPV (not analog)
Relevance: Shows community appetite for open-source FPV video

16. Core Chipsets Used in Analog VTXes

RF Transmitter

RTC6705 (RichWave) -- The universal 5.8GHz FM transmitter IC
- Built-in VCO, PLL, modulator
- Internal PA: +13dBm (~20mW) max
- SPI-programmable frequency
- 3.3V supply, 40-pin QFN
- Every analog VTX uses this or its variants (RTC6705SP)

Power Amplifiers (External)

SKY85728 (Skyworks) -- Common in mid-range VTXes
SE5004L (Skyworks) -- Used in higher-power designs
RFX2401C -- Budget PA option
Various Chinese-made PAs for ultra-budget units
PA selection determines max output power, efficiency, and spectral cleanliness

Microcontrollers (for protocol handling)

STM32F0/F1/F3 -- Used in OpenVTx-compatible boards
EFM8 (SiLabs) -- Used in some TBS products
Many budget VTXes use simple logic or small 8-bit MCUs

17. Design Specification for "Ultimate Open-Source Analog VTX"

Based on this market analysis, here is what the ideal open-source analog VTX would look like:

Target Specs

Parameter	Specification	Rationale
Output power	PIT / 25 / 200 / 400 / 800mW (1W stretch)	Covers all use cases; 800mW is the sweet spot
Input voltage	7-36V (2-6S direct)	No external BEC needed
5V output	5V @ 1A regulated out	Power camera and other accessories
Frequency	40ch minimum (A/B/E/F/R), 48ch unlocked option	Raceband essential
Control protocol	MSP primary, SmartAudio V2.1 + Tramp fallback	Future-proof + legacy compatible
Mounting	20x20mm primary, breakout/adapter for 25.5 and 30x30	20x20 is the standard
Antenna connector	MMCX primary, u.FL variant for micro builds	MMCX is the current standard
Weight	<5g (board only), <12g (with enclosure)	Competitive with Rush Tank Mini
Thermal	Aluminum enclosure as heatsink, thermal pad to PA	Proven approach (Rush Tank Solo)
Audio	Built-in AGC microphone	Nice-to-have, pilots like hearing motors
Firmware	Open-source (OpenVTx-based or new), USB-C config	Key differentiator
MCU	RP2040 or STM32	RP2040 aligns with your toolchain

Safety Features (Differentiators)

Feature	Implementation
Antenna detection	VSWR sensing on PA output; limit to 25mW if no antenna
Thermal protection	Thermistor on PA; auto-throttle power at 70C, shutdown at 85C
Temperature telemetry	Report via MSP to Betaflight OSD
Boot-to-pit	Always start in pit mode; require explicit power-up command
Reverse polarity protection	MOSFET-based on input
Brownout hold	Capacitor bank to maintain clean shutdown on voltage sag

Bill of Materials Core

Component	Part	Notes
RF TX	RTC6705SP	Universal 5.8GHz FM TX IC
PA	SKY85728 or SE5004L	Determines max power; needs evaluation
MCU	RP2040	Dual-core, PIO for protocol handling
Regulator	TPS62xxx series	High-efficiency buck for 2-6S input
Connector	MMCX	Standard, pigtail to SMA for external antenna

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