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Home > Forum > Triathlon Forum > Does SRM PM9 work with Head Units that are only ANT+

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Does SRM PM9 work with Head Units that are only ANT+
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rockdude
Apr 29, 24 9:27
Post #1 of 7 (469 views)
In the SRM documentation it says that the SRM PM9 works with ANT+ or Bluetooth, but then it has a contradictory statement saying the Head Unit must have Bluetooth for the SRM PM9 to work. Has anyone pair the SRM PM9 to a Head Unit like a Garmin 500 that does not have Bluetooth?
BoulderCyclingCoach.com
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Re: Does SRM PM9 work with Head Units that are only ANT+ [rockdude] [ In reply to ]
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BergHugi
Apr 29, 24 10:07
Post #2 of 7 (454 views)
It will work, the PM9 broadcasts in the ANT+ PowerOnly protocol.
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Re: Does SRM PM9 work with Head Units that are only ANT+ [BergHugi] [ In reply to ]
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rockdude
Apr 30, 24 5:00
Post #3 of 7 (404 views)
Thanks, I called SRM and the person didn't sound confident in his answer but said it would not work with an ANT+ only head unit because it would not work with their older ANT+ only SRM head units.

BergHugi wrote:
It will work, the PM9 broadcasts in the ANT+ PowerOnly protocol.
BoulderCyclingCoach.com
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Re: Does SRM PM9 work with Head Units that are only ANT+ [rockdude] [ In reply to ]
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BergHugi
Apr 30, 24 5:26
Post #4 of 7 (397 views)
rockdude wrote:
Thanks, I called SRM and the person didn't sound confident in his answer but said it would not work with an ANT+ only head unit because it would not work with their older ANT+ only SRM head units.


Like you, some months ago I had a conversation with a SRM guy, but he was a competent one at the headquarter in Germany, knowing all technical internals, and I could talk to him in German.

I wanted a track PM. He explained to me that SRM has turned to the ANT+ Power Only protocol (the ANT+ protocol every bike computer and every powermeter with the ANT+ logo on it should understand) with the PM9. SRM kipped their Crank Torque Frequency (CTF) protocol with the PM9. I than ordered an “old” PM7 for a good price, because I very much prefer the Crank Torque Frequency protocol.

The SRM head units up to the PC7 understood only the SRM CTF protocol. The PC8 since about 2016 knows every ANT+ power, speed and heart rate protocol.
Last edited by: BergHugi: Apr 30, 24 5:38
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Re: Does SRM PM9 work with Head Units that are only ANT+ [BergHugi] [ In reply to ]
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Bdaghisallo
May 1, 24 9:12
Post #5 of 7 (336 views)
BergHugi wrote:
rockdude wrote:
Thanks, I called SRM and the person didn't sound confident in his answer but said it would not work with an ANT+ only head unit because it would not work with their older ANT+ only SRM head units.


Like you, some months ago I had a conversation with a SRM guy, but he was a competent one at the headquarter in Germany, knowing all technical internals, and I could talk to him in German.

I wanted a track PM. He explained to me that SRM has turned to the ANT+ Power Only protocol (the ANT+ protocol every bike computer and every powermeter with the ANT+ logo on it should understand) with the PM9. SRM kipped their Crank Torque Frequency (CTF) protocol with the PM9. I than ordered an “old” PM7 for a good price, because I very much prefer the Crank Torque Frequency protocol.

The SRM head units up to the PC7 understood only the SRM CTF protocol. The PC8 since about 2016 knows every ANT+ power, speed and heart rate protocol.


What's the advantage to sticking with the SRM CTF protocol over going with the new ANT+ Power only protocol? Is it the ability to statically calibrate the PM with weights with the CTF Protocol?
Last edited by: Bdaghisallo: May 1, 24 9:12
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Re: Does SRM PM9 work with Head Units that are only ANT+ [Bdaghisallo] [ In reply to ]
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BergHugi
May 1, 24 10:49
Post #6 of 7 (315 views)
With power only one is restricted to a time controlled ~1 Hz sampling rate. Power only is a black box, the receiver just gets the processed power value in Watt. One doesn’t know if or when a tare was done … .

With the event controlled CTF and a SRM track PM the sampling rate can go up to ~ 4 Hz. A dedicated receiver can process the higher sampling rate (for example a WASP for velodrome aero testing) and hence one has better synchronization with fast speed sensors. The slope and the tare / zero value is / can be stored on the receiver, thus one has control over it. CTF is closer to the hardware, it is only a grey box.
Last edited by: BergHugi: May 1, 24 10:51
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Re: Does SRM PM9 work with Head Units that are only ANT+ [BergHugi] [ In reply to ]
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Bdaghisallo
May 1, 24 11:18
Post #7 of 7 (305 views)
Cheers.
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