I recently got two older Icom IC-2N HTs (2 meter) for use in decoding
APRS packet radio. Nice radios, but I get less than 10% of packets
decoded with either radio. Compared to 100% of packets using my Yaesu
VX-2R. I know the problem is not the decoder, but the radio audio,
and wondered if there is anything I can do to improve the Icoms.

(And, no, I do not have an oscilloscope.)

Mike

In article ,
Radioactive Man wrote:

I recently got two older Icom IC-2N HTs (2 meter) for use in decoding
APRS packet radio. Nice radios, but I get less than 10% of packets
decoded with either radio. Compared to 100% of packets using my Yaesu
VX-2R. I know the problem is not the decoder, but the radio audio,
and wondered if there is anything I can do to improve the Icoms.

The first and simplest things I'd suggest a

- Make sure that you've turned the HT's power-saving receiver mode
off! A lot of HTs save battery power by spending most of their
time with the receiver "asleep", turning the receiver on several
times per second, and checking for the presence of carrier. This
will play merry hob with packet reception, as you'll almost always
lose most of the packet-synchronization preamble.

- Turn the HT's volume level down fairly low. You want to make sure
that the analog signal coming out of the HT isn't clipping
(overdriving the HT's audio output circuitry) and isn't overdriving
the TNC's input circuit. It's usually a good deal easier for a TNC
(hard or soft) to track a low-level audio signal, than it is for it
to track an overdriven high-amplitude signal full of distortion and
intermodulation.

If neither of these helps, then I'd suspect that there's some nasty
noise or distortion, or excessive receive equalization occurring in
the HT's audio circuitry, and that some substantial circuit mods might
be required. These would probably require a schematic, 'scope, and
some audio analysis tools such as an audio spectrum analyzer to figure
out properly.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

In article ,
Radioactive Man wrote:

I recently got two older Icom IC-2N HTs (2 meter) for use in decoding
APRS packet radio. Nice radios, but I get less than 10% of packets
decoded with either radio. Compared to 100% of packets using my Yaesu
VX-2R. I know the problem is not the decoder, but the radio audio,
and wondered if there is anything I can do to improve the Icoms.

The first and simplest things I'd suggest a

- Make sure that you've turned the HT's power-saving receiver mode
off! A lot of HTs save battery power by spending most of their
time with the receiver "asleep", turning the receiver on several
times per second, and checking for the presence of carrier. This
will play merry hob with packet reception, as you'll almost always
lose most of the packet-synchronization preamble.

- Turn the HT's volume level down fairly low. You want to make sure
that the analog signal coming out of the HT isn't clipping
(overdriving the HT's audio output circuitry) and isn't overdriving
the TNC's input circuit. It's usually a good deal easier for a TNC
(hard or soft) to track a low-level audio signal, than it is for it
to track an overdriven high-amplitude signal full of distortion and
intermodulation.

If neither of these helps, then I'd suspect that there's some nasty
noise or distortion, or excessive receive equalization occurring in
the HT's audio circuitry, and that some substantial circuit mods might
be required. These would probably require a schematic, 'scope, and
some audio analysis tools such as an audio spectrum analyzer to figure
out properly.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!