ASL Success Part 3

This just keeps getting better and better! Love this thing already.

Preamp Built

From the previous post, I talked about building a preamplifier stage for the dynamic mic. The first iteration didn't go so well, and it may have been more to do with the construction, power delivery and choice of parts. 

Initially, I built the preamp around a C945, which could have worked I imagine if I used a different value of capacitors. Not only that, but I learned so much about Class A amplifiers, namely the basic 2 resistor-2 capacitor one that I've mentioned before.

In the end, I've chosen to stick with a 2N3904 as they're readily-available and they do pretty well at audio frequencies. I also changed the 10k resistor to 2.2k, as this provided the best halfway bias voltage for the transistor. Finally, I swapped out the 100nF input and output ceramic capacitors with 1uF electrolytics. In addition, I also decoupled the power line with 100nF ceramic and 10uF electrolytic capacitors.

The result? Relatively quiet transmit audio with the occasional low frequency hum. And my voice can be heard clearly at the halfway mark of the mic gain knob and clips at the max position. Right now the preamp is breadboarded but I've designed a board on JLCPCB and am going to purchase that once I feel that the preamp is ready.

Echolink

I've also chosen to add Echolink onto my node. Echolink is the predecessor to AllStar, and was one of the first IRLP modes available for repeaters. Several repeaters, links/nodes, and users already adopt Echolink, so why not just add this on to reach even more people?

Echolink dials much differently than AllStar. To dial in node 9999 (Echolink test node), you'd assume to type *39999. But what if I told you this isn't correct?

On Echolink, we need a few things. 

First, start your node number with 3.

Next, count how many numbers the node is. Echolink works with 6-digit node numbers. Fill preceding spaces with 0s.

Finally, put it all together.

So for 9999, it looks like (dial *3)3009999. That'll connect you to the test node. When you're done, disconnect with (dial *1)3009999. If you ever look at node maps, you may see 300xxx nodes that aren't in the database. These nodes are most likely to be Echolink nodes, which are also possibly connected to other users and links.

You'll also want to port forward UDP 5198 and 5199, as well as TCP 5200. These ports are needed for Echolink to communicate remotely with the servers. ASL3 already has firewalld set up for these ports, so a firewall isn't necessarily needed if you have ASL3. If you're using HamVoIP, for sure get a firewall installed and running ASAP. Networking threats are no joke, especially in 2026.

"S-Meter" and OLED

Not mounted yet, but I downloaded a VU meter on my phone and it looks really cool when held up to the external speaker. I can only imagine what it will look like in the original S-meter window. I have yet to make a bezel but I'll have it soon. Same story for the OLED, which is just hanging out of the old channel selector :)

I've also added on a Midland logo and an Echolink logo to the OLED, which is very appropriate for the chassis that it's in and the secondary service that it provides. The OLED sometimes needs refreshed after a period of inactivity but that's to be expected. I might add a reset button to the panel but I'm not quite sure yet.

iaxrpt

This softphone works GREAT with my setup. I usually listen in to the WW7PSR net when work is super slow. It works but I can definitely tell there's stuttering from the internet instability. Once I get an external antenna I bet it'll get better.

Audio Output

I swapped the LM386 for the PAM8302. Hash noise? Gone. No annoying analog-NTSC-scan-sounding hissing anymore!!! Class D is truly the way, and while the LM386 does have its uses, I wouldn't use it in this application if you don't have to.

So that's it! I've pretty much completed this project and am very happy with the results. Overall, and again I'll say it, I would do this project again. It's my hope that if and when my younger cousin gets licensed, I can build him his own radioless node out of the other spare CB chassis I have!

Stay tuned for photos, because I'm confident the final result will be well worth the labor.