KMC-38GPS vs KMC-47-GPSD

[bigRoN18]

I am curious, but can't seem to find anywhere, what the difference is between these two GPS microphones that are both supposed to work for my TK-2180K2 portable. I have tried a Google search, as well as these forums with both product numbers but didn't find anything other than it appears the KMC-47D replaces the KMC-38GPS. Is the 47D more accurate? Does the "D" stand for differential or just digital, for the Nexedge/DMR/P25 radios? I found the older KMC-38GPS listed on Amazon for $40 and ordered one, but just curious if I "get what I pay for" by going with the older model. My radio is for Search and Rescue purposes and I don't see us going digital; as we give and receive mutual aid with other counties frequently and the move would mean fewer radios helping if involved in a large search... if the entire state doesn't choose the same digital pathway. We are now using FleetSync to send a short GPS blast at the EOT (along with Caller ID BOT/EOT) for as many radios have GPS capability; we have 10 microphones for our 24 Kenwood TK-2170 cache radios and I added a GPS unit to my personal TK-7360H mobile radio. I'm assuming I will have no issues but just curious if anyone had any first-hand knowledge of the differences.

 

[mmckenna]

Here's the differences in the GPS:
Sensitivity
KMC-38 = -142dBm (tracking), -136dBm (acquisition)
KMC-47 = -155dBm (tracking), -140dBm (acquisition)

Cold Start
KMC-38 = 70 seconds at room temperature.
KMC-47 = 40 seconds at room temperature.

Warm Start
KMC-38 = 38 seconds at room temperature.
KMC-47 = 38 seconds at room temperature.

Hot Start
KMC-38 = 8 seconds at room temperature.
KMC-47 = 8 seconds at room temperature.


Accuracy is listed as the same, both have 12 channel parallel receivers. Not sure what the D stands for. Both GPS receivers appear to be identical/same part numbers.

The last price guide that listed the TK-2180/3180 (that model has been discontinued) showed the KMC-47 as the GPS speaker mic option, so it appears that the KMC-38 was superseded by the 47.

KMC-47 can be driven a bit harder with audio than the KMC-38.


Many of the internal components are identical, a few differences that I noted above.

 

[bigRoN18]

Thanks. It looks like I won't lose much other than a slower cold start. I don't view that as too terribly important. Considering my newly acquired radio has been discontinued, I'm thinking that my $40 microphone may have been a decent deal. Yes, it is more expensive than knock-off brand non-GPS microphones, but it is a new (old stock) Kenwood-brand mic.

 

[mmckenna]

Thanks. It looks like I won't lose much other than a slower cold start. I don't view that as too terribly important. Considering my newly acquired radio has been discontinued, I'm thinking that my $40 microphone may have been a decent deal. Yes, it is more expensive than knock-off brand non-GPS microphones, but it is a new (old stock) Kenwood-brand mic.

Yeah, if that 30 seconds is a deal breaker, you are probably doing something wrong.

If it really is a genuine Kenwood, then that's a pretty good deal. Finding new/old stock KMC-41's at that price isn't always easy.

 

[bigRoN18]

GPS Mic battery

I finally found more info on the mic I ordered and notice that it has a built-in rechargeable lithium battery. Out of curiosity, do you know WHEN it is needed to change the battery? Does the radio tell you that it needs to be replaced? It looks like it requires a soldering iron to do so, so I'm guessing that it is relatively rare that it needs to be replaced, but just curious what signs to look for. Not only will I have my own KMC-38GPS for my TK-2180, I am also on the team that manages a cache of 24 TK-2170 portables, 10 of which have brand-new KMC-48GPS microphones. From what I've read, it appears that the GPS unit is powered by the radio and the radio charges the battery for when it is disconnected from the radio. What information needs to be maintained in the GPS unit when not connected to a radio? I just want to fully understand my radio and the radios we, as the communications unit, maintain.

 

[mmckenna]

The lithium battery in the mic will retain the last known position for up to 5 days with the radio shut off or the mic removed from the radio. Basically it's there to speed up acquisition time.

From the service manual:
If a Cold Start occurs frequently (the transceiver cannot
start GPS positioning after the transceiver is turned ON) even
though the transceiver has been continuously used, the internal
battery may be degraded. In this case, the internal battery
must be replaced using the following procedure.

Basically that procedure is to disassemble the mic, desolder the battery and replace it with a new one.

I don't know what the equivalent battery is for that mic, but the Kenwood part number is W09-1040-08 Lithium Cell. List price for the battery is $6.74, however it's shown as "obsolete" on the parts price list.
The replacement cell for the KMC-47 "looks" like it may be similar. P/N W09-1072-08, list price is $80.32(!!!), I suspect finding an after market replacement would be the way to go.

Soldering batteries takes some skill, it also requires static strap, appropriate iron, steady hand, etc. Something you could do, but if this really becomes an issue, it might be worth having someone else do it, or just buy a new mic.

 

[bigRoN18]

Thanks again. I just looked and saw that Kenwood Part W09-1040-08 is also known as Seiko Instruments Part No.: MS614S-FL29E. While listed as "Obsolete", it suggests MS614SE-FL28E, which is an active part number. Digi-Key lists them for $2.10 or Amazon for $7.51 (with free shipping for Prime members... I don't know about Digi-Key's shipping). I am wondering if the battery for the KMC-38GPS and the KMC-47/48GPS mics are actually the same but changed the part number to reflect one part being obsolete and being replaced by the other. The specs on MS614S-FL29E and MS614SE-FL28E are otherwise identical.