Voice Alert Radio

Hi all,

 

Been working with Bob B to make an APRS Voice Alert radio from an inexpensive two way set.

 

The Kenwoods that can do this run about $1200 each.

 

If this project works, people can make one of these for about $200 bucks or less.

 

Right now I'm working on a 'red lined' drawing that seems to be good.

 

At this time,I have something that seems to meet all the requirements.

 

It's one of my inexpensive 40 watt, under dash Midland units with a bunch of 'mods' in it.

 

It supports the data channel of 144.39 and a number of Northern Virginia area repeaters and simplex channels.

 

I suppose I can stick in some NWS as well.

 

The #1 test radio is built into a 70-342B XL.

The 70-342BLXL is a 'wide space' radio, so the TX and RX will cover all of High band.

 

If you look up Bob WB4APR's web site you can learn more about the Voice Alert system.

 

It transmits APRS packets with a 100Hz tone.

 

The data packet with tone acts like an alert signal to someone with a similar radio.

 

The call sign and a short message (Need to get a photo of the TT3 Programing page with the particulars) will pop up on the Kenwood's text display saying that a Voice Alert station is near by.

 

This radio has no data display section, but the audio chain and the PL decoder are more or less stock. There is room in the design to the later addition of a 'ham hud' like device. At this time I lack the ability to afford one. Voltage and audio can be gotten from the radio, routed via pins on the power cable up to a remote display.

 

The radio receives 144.390 with a 100Hz pl as well, so if someone transmits a short voice message, you get to hear it, acknowledge and move on to a handy frequency like 146.52 . (Channel 52)

 

As it stands now, the radio has the APRS channel in it.

A modified TT3+ controller.

A fair amount of custom wire work.

 

When the radio is not on the APRS channel, the data transmission is inhibited.

 

(A couple of little gotchas.

We are mixing 25 year old comercial radios and more modern APRS controlers.

Some things are not going to fit all that well.

 

Any TT3 when first turned on, has a 'boot up' cycle.

Part of that is a transmit command. No way around it.

The TT3 boots up a touch slower than the radio.

So at cold start up, the radio wakes up on channel, just before the TT3.

 

If the radio is powered up on a voice channel, that data chirp is going to on the air.

No way around it.)

 

This is how I expect the unit to be used.

 

I expect it to be an APRS tracker first.

 

It will spend most of it's time on channel 00 (144.390 100hz tone encode and decode)

 

A voice alert station second.

 

If and when someone hears it, they can call back, then switch and answer to a working channel like 52.

 

General talk around third.

 

Some days we need to talk to each other, not just send data back and forth.

 

At the moment it has a few local channels in it, I can add more, for a total of about 30 voice channels.

 

What I would like is someone who drives a lot in the area to take it for a couple of weeks and see if it works as advertised.

 

My path to and from work most likely won't cut it.

 

What it will need.

 

A 2M Antenna.

A GPS puck (5 volt only, I have one but do not like to loan it out.

They are expensive.)

 

I can program your call sign into the TT3+ and add some of your favorite 2m channels into the program.

 

Catch me off line at

 

KA2ZEV@yahoo.com

 

or

 

703 863 4574 after 1630 and before 2100 eastern time.

 

Thanks in advance.

Mike

 

Done