cdm dekey

[33kracing]

i got a question for the young and young at heart... i own three cdm1250's (two of which are uhf 403-470 MHz and one vhf 136-174 MHz) and one cdm1550 vhf 136-174 MHz. when you dekey any of the three cdm1250's regardless of mic used, (i have like 6 mics of different kinds) it doesnt de-key immediately. it almost sounds like a quick "thump" upon listening to it. the cdm1550 that i own as well as every pd or anyone else that uses them just de-keys quickly, (almost like a cb or something) no noises or thumping of any kind heard. is there something programming wise or mic style wise that will take this out of it on the cdm1250 radios? thanks in advance.


ps-you really notice it when mdc-1200 signalling is set to post-id.

 

[CommJunkie]

ps-you really notice it when mdc-1200 signalling is set to post-id.

That's exactly what it is. When you unkey, the radio sends the MDC signal, so the red TX light will remain lit until that's done.

 

[Gezelle007]

Older post but certain mics do make a difference. I noticed this when testing a CM300: Using a smaller, MCS style mic (HMN4069D) with it would make it dekey almost immediately when you let go. However using the larger, standard mic (HMN3596A) with it would leave a very pronounced thumping sound like you described (regardless of how you treat it in your hand) and it would take twice as long for the radio to dekey. I much preferred the shorter option..

 

[kayn1n32008]

Wirelessly posted (Mozilla/5.0 (BlackBerry; U; BlackBerry 9900; en-US) AppleWebKit/534.11+ (KHTML, like Gecko) Version/7.1.0.1047 Mobile Safari/534.11+)

It may also be caused by having PL reverse enabled as well.

 

[33kracing]

Older post but certain mics do make a difference. I noticed this when testing a CM300: Using a smaller, MCS style mic (HMN4069D) with it would make it dekey almost immediately when you let go. However using the larger, standard mic (HMN3596A) with it would leave a very pronounced thumping sound like you described (regardless of how you treat it in your hand) and it would take twice as long for the radio to dekey. I much preferred the shorter option..

yeah i figured out that the "stock" black mic does in fact make the dekey shorter without the "bump" or "thump" sound haha. i forgot all i have is the older, white mics besides the stock black one that came with radio. they also make a mic that resembles the speaker/mic from the HT1000 type series radios... and that REALLY makes for a delayed dekey...

 

[33kracing]

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It may also be caused by having PL reverse enabled as well.

im pretty sure i have that disabled with no avail...but will entertain that function in the future...where is it located in CPS??

 

[Gezelle007]

yeah i figured out that the "stock" black mic does in fact make the dekey shorter without the "bump" or "thump" sound haha. i forgot all i have is the older, white mics besides the stock black one that came with radio. they also make a mic that resembles the speaker/mic from the HT1000 type series radios... and that REALLY makes for a delayed dekey...

Lol I've seen those on ebay! Both the keypad version and the ones that look exactly like the regular RSM's. The keypad ones are probably a lot harder to find though.

im pretty sure i have that disabled with no avail...but will entertain that function in the future...where is it located in CPS??

And I should have mentioned this as well, I tried it both with the burst and without, with PL and without PL, and even though it will make it shorter, you will still hear the thumping sound. And that feature is programmable in each conventional personality.

 

[cmdrwill]

Some microphones switch the Mic Hi lead and the "thump" you hear is the mic amp being disconnected from the radio, in simple terms. The later mics do not switch in the same way so you may not hear the "thump", the mic disconnecting from the DC bias in the radio..

Remember these radios use a "amplified" mic. Motorola has used the same mic circuit in the radio which was a carbon mic since the 50's. The CDM is no different. One person who did not like the "thump" in Maxtracs changed the value of a capacitor in the radio which greatly reduced the "thump".

 

[33kracing]

Some microphones switch the Mic Hi lead and the "thump" you hear is the mic amp being disconnected from the radio, in simple terms. The later mics do not switch in the same way so you may not hear the "thump", the mic disconnecting from the DC bias in the radio..

Remember these radios use a "amplified" mic. Motorola has used the same mic circuit in the radio which was a carbon mic since the 50's. The CDM is no different. One person who did not like the "thump" in Maxtracs changed the value of a capacitor in the radio which greatly reduced the "thump".

dang man thanks for the not-so-technical, technical answer lol and I didn't want/feel the need to ask on here about it but it bugged me long enough I knew there would be someone on here to post an answer. consider it "case closed" haha