Interfacing a Microphone and a Mixer to a Radio

I’ve been watching videos of guys on ham radio operating (especially some of the guys on the 3.916 nets), and I’ve been wondering how to hook a “regular” microphone through a mixer to my radio. I watched a video by Bob Heil that did a good job of explaining how to do it (LINK). Then I watched a video of why you would want to do it (LINK). I had all of the parts to build a solution in my junk bin!

The first thing I learned was something I basically already knew; I needed to isolate the mixer from the radio using an isolation transformer. I prefer this method so that there are not any ground loops. Back when Radio Shack was alive I purchased two of them to use as a digital interface for my 10m rig. I since upgraded to a SignLink to do that work so the DIY interface went into my parts bin.

This switch looks too cool!

I started my research by looking at some available interface schematics on the web. There were several designs that used chokes, but I decided that I didn’t want to do that. I drew up a schematic in my engineering notebook with a circuit board and box idea. The circuit is quite simple. The 600:600 transformer connects one side to the input jack that comes from the mixer. The other side of the transformer connects to a potentiometer and two resistors. Then the output is fed through another audio jack to the radio. Another momentary switch is used as the PTT. Look at the picture of this switch! It’s from another man’s junk bin. Free and awesome looking.

I added some printed lettering to show what each jack was for. I really like how the volume indicator turned out!

I designed a box to house it in using Tinkercad.com and used my 3D printer to create the box and switch case. Wiring it up was easy. I tested it out on a net the other night before it was put in the box, and audio reports came back good. It works. I don’t have another receiver to listen to it, so I cannot give any info as to how my actual sound “sounds”, but I know that the interface works!

Getting the audio and the PTT to the radio was a different story. Like the SignaLink and other interfaces, there is usually a modular plug that breaks out into a radio’s specific plug so I tried to make my interface similar. I broke the rules just a little

This switch can also be modded to hold in the on position. It is mom-off-on, but I left the on section unwired for now.

with the PTT switch since I wired it straight to the radio. There’s no picture of the plug to the radio. If you’ve seen one you’ve almost seen them all.  What sets my kit apart is this switch. Good night! I love how it looks. I’m pretty sure that is an aircraft switch. I threw most of the crap that I inherited from a guy, but these switches looked too cool to toss. I have more, and I’ll probably do this again for something else!

I’ll leave you with an image of the inside of the box, and an image of the schematic. This was a fun build, and I look forward to using it on the air. The Santa net on 3.916MHz starts tomorrow, so I know the kids and I will be using it. Some upgrades in the future will be a mixer that actually has the right EQ as mentioned in the videos. My main goal was the get where I could actually use my Shure SM-58 and the mixer. Now I can look to upgrade. Perhaps I’ll own a Heil in the future!!!

This schematic is bare bones. You could add filters or beads for RF if you needed them. I added clip on ferrite chokes on the audio cable to my radio (just in case).
It’s a tight squeeze. I promise that I planned it that way.

Astatic D-104 Lollipop Mic Restoration

Astatic D-104 MicEarlier this year (2016) I was on the radio on SSB, and I received an audio report during a longer conversation that described my audio as nasally and difficult to listen to. I did some research on the Astatic D-104, and there was a modification that was supposed to change the characteristics of the mic. I attempted this mod by following a step-by-step PDF which involved using a JFET, but for some strange reason it didn’t work well with my radio. It didn’t have enough audio output to push the finals of my radio! Time to put it back to how it was… The problem is that I don’t remember, and I didn’t document it before tearing it apart the first time. Continue reading Astatic D-104 Lollipop Mic Restoration

Raspberry PI File Server: Backup Ham Radio Data

Prepare for Disaster

It happened once before when I was KK4FGM. I had a logbook on a computer that died, and I lost my entire logbook. It was never uploaded to LOTW, QRZ, eQSL, or anywhere, so I lost all credit for any awards or recollection! Since getting back into HF in December 2015, I have made 100% sure that I have duplicate copies of my logs and other important data on a separate device. Continue reading Raspberry PI File Server: Backup Ham Radio Data

Inverted Vee 40m Dipole and Mast

My Purpose

Antennas in the back yardIt has been a long time since I have experimented with antennas and yard ornaments (tall, antenna holding things like towers and masts), but recently I have been annoyed by the performance of my Hustler 5BTV vertical. I have vertically polarized noise that tends to aggravate me, so I wanted to try an inverted vee dipole to see if conditions improve.

Lately, I have been working CW, and I have had some fading signals and noise, so I figured that the dipole might help some with this. The issue is that I needed somewhere to mount this thing! Continue reading Inverted Vee 40m Dipole and Mast

Solo Hike at Providence Canyon State Park

The back country trail is a beautiful hike. I enjoyed looking at the scenic route, and this spot kept my attention for a snack and rest.
The back country trail is a beautiful hike. I enjoyed looking at the scenic route, and this spot kept my attention for a snack and rest.

The day has come and gone for my first overnight backpacking trip, and it was a 100 percent success. Success did not come without some challenges, though. This was a great trip for me to put my gear to the test before heading out on a two night, three day hiking adventure with some friends on the weekend before Thanksgiving. There were only two weaknesses in my gear that arose during the trip: water and foot gear. There was a third oversight in gear that caused a problem with my foot gear, but it’s almost unrelated; I misplaced my pocket knife. Continue reading Solo Hike at Providence Canyon State Park

Preparing For My First Overnight Hike

Before the Beginning

My first time in a hammock, and I can't wait to sleep in it!
My first time in a hammock, and I can’t wait to sleep in it!

After being invited to go hiking in November, the itch to go hiking before the big trip has taken over. I love camping, and I am extremely excited to get to go hiking with a bunch of guys. I have been looking for a chance to go on an overnight hike before the big one, and the chance has arrived. The paper planning stage of gathering and purchasing gear for hiking is about to bear the fruit of a hike. Continue reading Preparing For My First Overnight Hike

Camping Without Being A Pack Rat

My son and I enjoy coffee around the camp fire.
My son and I enjoy coffee around the camp fire.

For most of my childhood I can remember going on camping trips with my dad, and I remember it being so simple camping as a young man. The stories I can tell of the cold, rainy mornings huddled over coffee or being tormented after dark by my uncles are treasured. The memory of having my eyesight choked out from smoke while blowing on a fresh fire is inescapable. One thing that I can barely recall is how much crap we took with us. I’m almost certain that my dad was a minimalist camper. We probably had the smallest tent, slept on the ground in a sleeping bag, and had just what we needed to cook and eat. I remember it being a no frills trip that was enjoyable. Continue reading Camping Without Being A Pack Rat

Backpacking With Friends

My son opened my new Teton hiking backpack!
My son opened my new Teton hiking backpack!

I was recently invited to go on a men’s hiking trip that is scheduled for Mid November 2015, and I naturally couldn’t say no to the adventure. My boss and friend, Eric, invited me and said that I could borrow his wife’s hiking kit to make sure that I’d like the adventure before investing in my own equipment. I was good to go until I started researching things, and I couldn’t stop myself from diving in head first. Continue reading Backpacking With Friends