GP300 Narrow or Wide Band?

N6ATF · Post by **N6ATF** » Sun Dec 18, 2005 8:14 pm

Already searched, couldn't find it. I have the P94YPC20D2

The reason I ask is because...

I've followed the instructions perfectly for the TM-V7A to prepare it for remote controlling via DTMF with all appropriate responses from the radio...

But Motorola HTs don't have DTMF 'ABCD' on them, the best you get is 0-9 */#, so I either have to carry an expensive and necessarily large UHF HT (not a mini or credit-card HT, which can't fit DTMF pads) or get a DTMF generator like Radio Shack used to sell that would slip over telephone mics. Before getting a DTMF box, which seems to be the better option, I figured I'd see if playing back the access tone sequence with a Java tone generator would work.

I used: http://www.dsptutor.freeuk.com/dtmf/ToneGenerator.html

I had it burst the A###, which I recorded from the speaker into a digital voice recorder, then I played it back into the microphone, but the TM-V7A remained in standby as if it did not receive the tones at all, which is BS, since I saw the s-meter go full strength.

I tried varying the distance of the playback, volume of recording, with no effect, and the best advice I got was to ask here:

Try batlabs.com, or bat-labs.com, whichever it is, it's a Motorola equipment website. I'm sure that someone will know the bandwidth for the GP300 there."

Hartley · Post by **Hartley** » Sun Dec 18, 2005 10:06 pm

Hi,

The model number you have is a "wideband" (5 kHz deviation) radio, so it should work just fine with the Kenwood radio, bandwidth-wise.

DTMF can be tricky stuff, and the most difficult part is ensuring that the "twist" is correct. DTMF consists of two different audio tones, and if the levels of the two tones are too far apart (that is, one tone is much louder than the other), the the decoders won't detect them. ("twist" is the loudness relationship of the two tones).
Decoders also don't like a lot of distortion or noise, so if you have background noise, or if the mic is being driven too hard, it can fail to work.

It can be quite difficult to figure out what is wrong, as it takes a pretty expert "ear" to detect these problems without test equipment.

73 DE Hartley

N6ATF · Post by **N6ATF** » Mon Dec 19, 2005 12:27 pm

I've come to the conclusion that no DTMF through the microphone is decodable by the TM-V7A, if it's not just a piece of junk that won't decode ANY DTMF at all, even though it claims to.

There is no background noise, the mic-to-source distance has been varied, high and low volume, high and low audio gain, short and long length tones, different speakers were used, 3 different DTMF tone sources were used to eliminate possible bad twists... Everything under the sun except throwing both radios in the scrap heap for not working together has been done.

Not being able to afford an HT that does have DTMF ABCD, I cannot verify that the TM-V7A actually works as advertised. All I can say is, if you want to do anything more advanced than amateur radio simplex or voice repeater only work with a Motorola 2-way, you're in the wrong market.

va3wxm · Post by **va3wxm** » Mon Dec 19, 2005 3:09 pm

The GP-68 has those missing alpha keys.

Tho there is the legality of owning one in the US.

N6ATF · Post by **N6ATF** » Mon Dec 19, 2005 3:46 pm

Hey, Jeff.

I think if I limit it to amateur freqs only, it doesn't have to be type-accepted, and is legal for me to use under my ham license.

N6ATF · Post by **N6ATF** » Mon Dec 19, 2005 3:56 pm

Or if I was afraid about people stealing the radio off my belt and jamming police freqs - which I'm not, I could get the AP73.

va3wxm · Post by **va3wxm** » Mon Dec 19, 2005 6:13 pm

If you can find one. They're fairly rare.

I've got both VHF and UHF GP-68's. The keypad programmability is neat but it just doesn't "feel" like a Motorola radio.

More durable than a hammy handheld but nowhere near the toughness of, say, a Saber.

N6ATF · Post by **N6ATF** » Mon Dec 19, 2005 8:31 pm

I don't suppose there's an RSS hack to make one of your GP-68s an AP73 [freq range]? Ha.

As far as Sabers, seems like you get what you pay for... and eBay is like the central repository for batteryless, dusty, bleached-out black as-is Sabers.

AEC · Post by **AEC** » Tue Dec 27, 2005 9:52 pm

This is a misleading post.
Narrowband or wideband....?

Narrow band means channel spacing....6.25 Khz. (452.80625)

Wide band means channel spacing......12.5 Khz. (452.7125)

GP300/P110 portables can NOT do 6.25 Khz. channel spacing, 12.5 is the least they will do, so you can only input say...452.7125 and not 452.80625.

You can get two 6.25 Khz. channels in one 12.5 Khz. 'normal' channel, that's the difference.

Defining narrow or wide band as a DTMF function is improper.

Enterprize.....One to beam up!

N6ATF · Post by **N6ATF** » Tue Dec 27, 2005 9:59 pm

Thanks for clarifying that. I've not seen those long frequencies before.