Batboard

Anyone have any opinions as to the difference between using a public safety mic vs. a regular speaker mic?

I have an MT 1000, and I'm trying to decide which is best...

I think that the public safety mic has a steel cable in the cord to prevent it from braking during a foot chase, ect. ect. ect. along with the antenna connector on the top. It's recommended that it only be used with Uhf and 800/900 Mhz...

It's just a little stronger and a little more $$$$$$ than the normal speaker mic...


Dan...

I've tested a Saber PS speaker/mic (intended for UHF) on VHF through a Bird 43 wattmeter and the reading showed no reflected power with a stubby TNC antenna on the Bird's output. I've always understood that the reason the PS units don't have a coiled cord is that coil acts an inductor on the RF signal which travels up the cable, which would explain, obviously, why the PS units never have a coiled cord.

The actual field use of the VHF stubby on the PS mic proves that it works very well. Just remember to program your power low if you're using simplex at a hamfest, otherwise that RF goes right into your head, and while I don't have much faith in those RF damage theories (at least at 7 watts or less) it still never hurts to use no more power than you need to communicate.

Tom, W2NJS
...in D.C.

I know that a lot of people think those PS mics are great, but I suggest a test.... Put the PS mic on and see how well you recieve the "system" in a weak area. Then try it with the normal radio in the same place. I have yet to find one of the PS mics that was not VERY VERY lossy. ESPECIALLY in the 800/900 bands. Not much better in the UHF. The only place where I have seen that it works ok is the band where it is not recommended. If you really want the portable to work, with maximum effeciency, get an EARPHONE to listen with, and pull the radio up in the air in front of your face with the antenna away from your various body parts, and transmit a good signal. Unless you have a very good radio system (and who has that kind of coverage) speaker mics can be DANGEROUS. (FYI I have been a cop for 25 years).

I agree with PETNRDX about the poor receive sensitivity at 800MHz. We had a customer demo 6 P/S mics with their XTS3000 portables on our SmartZone system. Every one of them showed approx 30 less on the RSSI indicator in the display compared to a regular (6 inch) antenna.

Todd

I would bet that the coax from the mic head to the radio is something like RG174, which none of us ever uses at any frequency unless forced to do so. I wonder what the loss is at 800 mHz; probably phenomenally high, wouldn't you all think?

Now I'm wondering what installers run to roof mounts when doing an 800 mHz install in a vehicle?

Tom, W2NJS
...in D.C.

Installers run to the roof mount? Most installers do not even know what band the radio is in and put on the wrong antenna or mount/cable. I am glad I learned both installation and technician.
I did a lot of 900 Spectra repairs and instalations.

The loss in the RF cable in the PS speaker mics is usally made up for by the higher antenna location. But at 800 or 900 the total losses add up. I did do a security force at a car dealership that we put PS speaker mics on P200's on UHF simplex with very good results. I think training in radio use helps to correct for the poor transmit from portables.

I have an MNM6244B and ave used it on VHF (HT1000), UHF (HT1000 and MT2000) and on 800MHz (MTS2000). I have to say that ironically it is most effective on VHF! I used a Visar antenna on it, and though the 5" whip makes the mike an eyesore, and it is "top heavy", the performance was much better than the heliflex whip being right next to my body at waist level.

On UHF, I had no difference in performace using the standard 5" wideband whip either on the radio or the mike.

800 though, is another story, you can HEAR the difference in the rx noise floor using the 3" stubby on the mike versus using it on the radio directly.

Speaking of PSM's, is it my imagination or whatever happened to the NMN6194's? In my MTS2000 and my MTX8000 user guides, these are mentioned to be "Stanard microphone; inludes antenna (SMA) UHF, 800/900MHz (VHF capable) COILED CORD ASSEMBLY, 3.5mm ear jack, swivel and RECIEVE AUDIO HIGH LOW PUSHBUTTON". I have seen what I believe to be one of these years ago, it looked like your standard NMN6191/6193 Jedi mike head, with an antenna on top and a coiled cord. There is also a mention of a NMN6192 which is a noise cancelling version of the NMN6194. Anyone have experience with these? Are they available?
Our dealer only stocks and sells the NMN6228, NMN6243 and NMN6244, which are all the "Saber" style mikes with cords in varying lengths. I asked about them and they said that they are NLA.

mts2000des wrote:.....Speaking of PSM's, is it my imagination or whatever happened to the NMN6194's? In my MTS2000 and my MTX8000 user guides, these are mentioned to be "Stanard microphone; inludes antenna (SMA) UHF, 800/900MHz (VHF capable) COILED CORD ASSEMBLY, 3.5mm ear jack, swivel and RECIEVE AUDIO HIGH LOW PUSHBUTTON".....

Most Police forces that use MTS2000's in the UK use the NMN6241 Public Safety Spkr/Mic at UHF, it is like the Jedi standard spkr/mic, with a straight cord, SMA aerial socket on the top, with speaker Vol UP/DOWN and Emergency buttons on the side. It is used with either a UHF helical or UHF 1/4 wave whip.