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Version 53.1 by UT2UK on 2026/05/06 17:01
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1 == Internal latency measurement of the ERMAK-TT transceiver ==
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3 * Transmit mode (microphone input -> RF output): **45ms**
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7 [[image:1777980550259-754.png]]
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10 * Receive mode (RF modulator output -> headphone output): **52ms**
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14 [[image:1777980668036-257.png]]
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17 == Internal latency measurement of FLEX radio ==
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19 * [[https:~~/~~/community.flexradio.com/discussion/8027536/signal-in-to-audio-out-rf-to-audio-latency>>https://community.flexradio.com/discussion/8027536/signal-in-to-audio-out-rf-to-audio-latency]]
20 * [[https:~~/~~/www.n1kdo.com/sdr-delay-measured/>>url:https://www.n1kdo.com/sdr-delay-measured/]]
21 * [[https:~~/~~/community.flexradio.com/discussion/6865953/>>url:https://community.flexradio.com/discussion/6865953/]]
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25 [[image:1778007502882-224.png]]
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27 [[image:RackMultipart20151208-21021-1jin1qg-scope_1000_inline.png||alt="image"]] [[image:RackMultipart20151208-13976-moh3cq-scope_800_inline.png||alt="image"]] [[image:RackMultipart20151208-7743-183a2a1-scope_400_inline.png||alt="image"]]
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30 [[image:1778007575902-770.png]]
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34 [[image:image.png]] [[image:https://us.v-cdn.net/6032377/uploads/OB7NPE9JDLNX/image.png||alt="image.png"]]
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37 Thanks to [[Mike-VA3MW>>url:https://community.flexradio.com/profile/Mike-VA3MW]] and [[W7NGA>>url:https://community.flexradio.com/profile/W7NGA]]
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39
40 == Total latency measurement of the ERMAK-TT transceiver + EAX (USB) ==
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42 Measurements were performed on a Windows 11 PC Host + VAC by Eugene Muzychenko. The original VAC from ERMAK can also be used. They provide slightly lower latency due to optimized buffers.
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44 **Important note** - the original ERMAK VAC drivers are signed with a self-signed certificate. Therefore, driver signature verification must be disabled on the PC host.
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46 1. [[EAX audio control - release history>>https://sdr-ermak.com/xwiki/bin/view/Main/ERMAK-TT/EAX%20aduio%20control%20utility%20releases/]]
47 1. [[EAX VAC Windows 10>>https://nx8619.your-storageshare.de/s/pdeEJr5mG4ix7PQ?dir=/EAX%20VAC]]
48 1. [[Installing and configuring EAX on WINDOWS>>https://sdr-ermak.com/xwiki/bin/view/Main/ERMAK/%D0%A0%D1%83%D0%BA%D0%BE%D0%B2%D0%BE%D0%B4%D1%81%D1%82%D0%B2%D0%BE%20%D0%BF%D0%BE%D0%BB%D1%8C%D0%B7%D0%BE%D0%B2%D0%B0%D1%82%D0%B5%D0%BB%D1%8F%20%D0%95%D0%A0%D0%9C%D0%90%D0%9A/EAX%20-%20%D1%83%D1%82%D0%B8%D0%BB%D0%B8%D1%82%D0%B0%20%D0%BE%D0%B1%D0%BC%D0%B5%D0%BD%D0%B0%20%D0%B0%D1%83%D0%B4%D0%B8%D0%BE%D0%BF%D0%BE%D1%82%D0%BE%D0%BA%D0%B0%D0%BC%D0%B8%20%D1%81%20PC/%D0%A3%D1%81%D1%82%D0%B0%D0%BD%D0%BE%D0%B2%D0%BA%D0%B0%20%D0%B8%20%D0%BD%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%B9%D0%BA%D0%B0%20EAX%20%D0%B2%20%D1%81%D1%80%D0%B5%D0%B4%D0%B5%20WINDOWS/]]
49 1. [[Installing and configuring EAX on LINUX>>https://sdr-ermak.com/xwiki/bin/view/Main/ERMAK/%D0%A0%D1%83%D0%BA%D0%BE%D0%B2%D0%BE%D0%B4%D1%81%D1%82%D0%B2%D0%BE%20%D0%BF%D0%BE%D0%BB%D1%8C%D0%B7%D0%BE%D0%B2%D0%B0%D1%82%D0%B5%D0%BB%D1%8F%20%D0%95%D0%A0%D0%9C%D0%90%D0%9A/EAX%20-%20%D1%83%D1%82%D0%B8%D0%BB%D0%B8%D1%82%D0%B0%20%D0%BE%D0%B1%D0%BC%D0%B5%D0%BD%D0%B0%20%D0%B0%D1%83%D0%B4%D0%B8%D0%BE%D0%BF%D0%BE%D1%82%D0%BE%D0%BA%D0%B0%D0%BC%D0%B8%20%D1%81%20PC/%D0%A3%D1%81%D1%82%D0%B0%D0%BD%D0%BE%D0%B2%D0%BA%D0%B0%20%D0%B8%20%D0%BD%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%B9%D0%BA%D0%B0%20EAX%20%D0%B2%20%D1%81%D1%80%D0%B5%D0%B4%D0%B5%20LINUX/]]
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53 * Receive mode (RF modulator output -> EAX -> PC audio output): **197ms**
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57 [[image:1778050748939-595.png]]
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60 * Receive mode (RF modulator output -> USB audio -> PC audio output): **220ms**
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64 [[image:1778051095734-567.png]]
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66
67 == Total latency measurement of the ERMAK-TT transceiver + EAX (USB) and Flex radio in remote mode ==
68
69 **Measurement program**
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71 * **ERMAK-TT** — local connection to PC + EAX
72 * **FlexRadio** — remote connection (~~5000 km), RTT ~~100 ms, DAX v2, "long" filters. Propagation speed ≈ 3×10⁸ m/s → latency over 5000 km (one-way) ≈ 16.7 ms; network RTT 100 ms → one-way ≈ 50 ms; total ≈ **67-70 ms margin**
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74 **Measurement subject:**
75 Reception of one-second pulses at 4999 kHz
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77 [[image:1778072528651-371.png]]
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80 * Red ERMAK-TT
81 * Blue - FLEX radio. "Fast" filters (51ms)
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83 Result: 104ms-70ms=**30ms**, ** ERMAK-TT provides lower latency**
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85 [[image:1778072986007-908.png]]
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88 * Red ERMAK-TT
89 * Blue - FLEX radio. "Fast" filters (167ms)
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91 Result: 40ms+70ms=**110ms** latency difference, **FLEX radio** **provides lower latency**
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93 [[image:1778073107052-698.png]]
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95 **Conclusions**
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97 * When using **short filters** and **DAX v1**, the latency of **FlexRadio** and **ERMAK-TT(Phoenix) ** + **EAX) **is approximately comparable.
98 * The main contribution to latency in **DAX v1** comes from the audio stack buffers and the VAC driver; in **DAX v2 **this contribution has been substantially reduced thanks to the redesigned VAC.
99 * In **DAX v1**, the original VAC — Virtual Audio Cable by Eugene Muzychenko was used. ([[https:~~/~~/community.flexradio.com/discussion/8027376/smartsdr-2-8-1-and-bsod>>https://community.flexradio.com/discussion/8027376/smartsdr-2-8-1-and-bsod]])
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103 [[image:1778074304325-846.png]]
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106 * In **DAX v2**, a solution based on Thin Audio Gateway (the same author) is used, which provides smaller buffers and lower latency.
107 * **DAX v2** delivers a latency improvement of approximately **~~100 ms** compared to DAX v1.
108 * **We plan to migrate to a similarly architected VAC/low-latency audio engine by autumn 2026.**