Radio

Radio Interface for Phone/Tablet

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The MicroAvionics MM005 powered radio interface required a little extra effort to get working good with my tablet and phone. My Note 5 did not like the phone adapter, apparently the 1k Ohm resister across the microphone was insufficient to make the Note think a microphone was connected. This was not a huge problem since I planned on making my own cable anyway.

My Nexus 7 ( 2nd gen 2013) microphone input did not like the high level output by the MM005 from the phone or the AUX OUT port. The level was so high that it caused lots of clipping resulting in some horrible sounding recordings. My Note 5 did not seem to care and recorded well from both ports. The cable I made for the Nexus 7 included an additional resister to convert the line level output of the MM005 to microphone level. Maybe not the best way to deal with this but was certainly the easiest. The resisters fit inside the audio connector ends resulting in a nice clean looking cable. 


The other end of the cable goes to a dash mounted 3.5mm TRRS / USB port.
A short audio cable connects the tablet. 

To power the phone and tablet I used a ZeroLemon USB charger. I picked this particular model because it did not cause RF interference with the radio. Every other charger I tried caused tons of RF noise when tuned to around 132Mhz, the closest airport to me is CMH on 132.7 so it was only by chance that I even noticed this problem. I did take the charger apart so I could hard wire the power, I did not want to rely on it staying plugged into a cigarette lighter.

Not decided how our where I will mount this adapter but I’m thinking of just drilling a couple holes and using a zip tie. 

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Toner Transfer

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I’m still not happy with the dash so time for the fourth iteration. This time I designed it in CAD using OnShape.com, including all of the labels. To fabricate it and apply labels I thought using a tuner transfer method might be nice.

First the wood was vanished and sanded smooth. I only had A4 size toner transfer paper so I had to print multiple pages to cover the whole dash. PosteRazor was very helpful in printing the pages, just don’t forget to mirror your CAD image before printing.

Starting with the center bottom page I taped it to the board and used the wife’s iron to transfer the toner. To align the next page I pushed T-pins into various reference points.

Pins to mark index locations
Pins to mark index locations

Those same reference points were poked through the paper.

Pins to mark index locations
Pins to mark index locations

Then using the holes the next page was aligned using multiple reference points.

Aligning the transfer paper
Aligning the transfer paper

Then the page was tapped in place and toner transferred with the iron. This process was repeated until the whole dash was completed. The nice thing is if you mess up just sand off the mistake and try again!

Since all the holes were marked with toner it was really easy to cut out all of the holes precisely where I wanted then.

Toner transfer also marked hole locations
Toner transfer also marked hole locations

I might want to add some more text or switches before I complete the airplane so for now I am leaving off the final coat of varnish. But once completed I plan to add a couple of coats to help protect the toner from abrasion.

Preview of final dash
Preview of final dash

I recently started working on the electrical wiring and quickly discovered that most 12v USB phone chargers emit RF interference like crazy. When tuned to around 132Mhz the interference makes reception impossible. Anyone know of a decent priced charger that does not emit tons of RF?

Mounting the Radio

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After sitting in the cockpit trying different locations I decided to mount the radio on the dash. I had to make a small spacer of 1/8″ ply because the back of the radio is recessed where the screws are located.

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Spacer for radio
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Back of radio

It fits well in this location with the modified Yaesu adapter I made.

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Radio mounted

This location did block one of the two switches I had on the dash and the one unblocked switch cannot have a cover because the radio adapter keeps the cover from opening. I plan to enlarge the blocked switch hole to feed the radio wires through the dash. I’m undecided on what I want to do about switches. I really only need one switch but if my generator fails it would be nice to be able to turn off non-essentials to preserve battery power.

At this time I will go with just one switch next to the starter key. The dash is looking really nice so far.

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MiniMax dash with radio mounted

Yaesu Radio Adapter

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The Yaesu radio adapter for my MicroAvionics powered radio interface sucks. It sticks straight out the side blocking access to other parts of my dash.

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MicroAvionics MM014DD same as Yaesu CT-91A adapter

The Yaesu came with a really nice adapter but it was made for general aviation connectors making it useless for the MicroAvionics powered radio interface. So I cut the general aviation connectors off of it.

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Yaesu SCU-15 headset adapter with headrest ends cut off

Dropped by Radio Shack and picked up a 1/8″ female stereo cable connector. The white wire connects to the tip and of course the braid connects to the ground.

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1/8" stereo female jack

The other connector is a 3/32 and the Shack did not have any so I stole the connector from the MicroAvionics adapter. Red wire to tip, black to center and braid to ground.

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3/32 female stereo jack

I cut down one edge of each connector to ensure they both fit onto the MicroAvionics MM005 interface cable.

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Cut down to fit MM005
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Connect adapter to MM005

Before:

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Yaesu FTA-550 with MicroAvionics MM014DD

After:

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Yaesu with modified SCU-15 adapter

Push to talk

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The push to talk button will allow me to transmit on the air band radio. Having a convenient way to transmit and making it look attractive is my goal.

I used my hobby knife to cut a pocket in the plastic plug that goes in the top of the control sick.

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Control stick cap

The switch was installed and attached to the plug.

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PTT switch

I drilled a small hole near the bottom of the control stick.

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Hole for wire to exit

Added a grommet for the wire to exit.

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Rubber grommet

Finished product looks good.

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Finished control stick with PTT switch