Thought on a Receive Only 2nd COM Radio

[blaplante]

Recently I've encountered a couple of RV owners looking to add a second COM radio, mostly to listen to ATIS.

Given my experience with STRATUX, I got to thinking... why not use a Raspberry Pi and a SDR radio dongle to do this?

Turns out, not exactly a new thought. Well, a new thought to put in IN an airplane perhaps. There is already software - rtl_fm and after some fooling around I am listening to airband from my home desktop machine. A side advantage is that the SDR can also receive broadcast FM stations (using software "softFM"). And that is working well for me.

I did have issues with the Pi Zero. Way too much local noise. There are some reports that the Zero is noisy. Need to test with something else (a 3B or 3B+).

So all up, you need:
Raspberry Pi 3B - about $60
Nooelec SDR - about $50
SD card - about $5
Software - free
Display - maybe a 2x20 character LCD for $20 or less
Some sort of user interface for input... (not command line).
My thoughts are to use a bluetooth Numeric Keypad $20 (Amazon)
Volume control $5 or so
------------------------------------
Total about $160
so for under $200 an Airband / FM receiver
plus some software to take keyboard entries and do the tuning.

Thoughts folks?
Anything anyone is interested in? I can share where I've gotten to.

I think this won't be the solution for either of the buddies... for one he really wants a real radio for IFR redundancy, the other I think we'll hookup his handheld to the intercom and an external antenna.

And I don't think I need a 3rd radio just to pick up FM.

-Bryan

PS for future reference ... frequency calibration of the cheap SDR radio is the key to airband reception. Mine was far enough off (4 khz) so that I heard nothing until I fixed that.

 

[PaulvS]

Thoughts?
It would be an interesting exercise if you have time to tinker and enjoy the challenge, but it would be less expensive to buy a ready-made receiver e.g. this one is about $70:
https://www.aircraftspruce.com/catalog/avpages/radio_11-19180.php
or this one for about $125:
https://www.aircraftspruce.com/catalog/avpages/airlitepro.php

(Apologies Bryan I don't mean to be a party pooper!)

I've got a nooelec SDR on order to experiment with testing an ADS-B installation on the ground. The plan is to use Dump1090 or similar to decode the ADS-B messages and view SIL, SDA, NIC etc. A commercial ADS-B ramp tester like the IFR6000 is many thousands of dollars, so it's worth trying a low cost solution using one of the USB dongles and some free software.

 

[blaplante]

Thoughts?
It would be an interesting exercise if you have time to tinker and enjoy the challenge, but it would be less expensive to buy a ready-made receiver e.g. this one is about $70:
https://www.aircraftspruce.com/catalog/avpages/radio_11-19180.php

(Apologies Bryan I don't mean to be a party pooper!)

...

Well the reviews of the $70 solution aren't exactly outstanding. It depends on the earbud wire to double as an antenna. Which means it doesn't have an antenna jack - hence no ability to hook to a real external aircraft antenna.

The $123 unit looks reasonable. Although unclear if it has an antenna jack.

 

[PaulvS]

Hi Bryan

There's also this one for $125 that appears more rugged. Also several others on eBay and electronics shops.

https://www.aircraftspruce.com/catalog/avpages/airlitepro.php

Anyway those are my thoughts, I don't believe there is much $ to be saved by rolling your own, but it could be a fun project. For $195, Spruce has a Yaesu transceiver that can be connected to aircraft antenna and headset, so if I wanted to spend $200 then that is the way to go.

 

[rolivi]

I'm not sure I understand the use case.

When my plane was single nav/comm I flew VFR only (duh) and even on flight following it took a couple seconds to say "N1234 will be off freq for a minute to pick up the ATIS at Kxyz" and then check back with "N1234 is back w/ the weather" (or the info code if applicable)

I now have two nav/comms, and fly IFR.

Single PILOT IFR is one thing. Single nav/comm IFR is quite another.

Why would a seperate radio, with it's probable downsides, be advantageous to any pilot?

Edit to add: Even the SL40 has standby monitoring, so you could get the ATIS on standby monitoring, just as you get GUARD if you set that it standby with standby monitoring. That's not exactly new tech.

 

[Ed_Wischmeyer]

Edit to add: Even the SL40 has standby monitoring, so you could get the ATIS on standby monitoring, just as you get GUARD if you set that it standby with standby monitoring. That's not exactly new tech.

I can't recall that I've ever been denied a request to ATC to go off frequency.

You're right about ATIS, but going into airports with ASOS/AWOS, when ATC asks me to get the weather and the NOTAMs, ADS-B FIS-B often does the trick.

These days, I fly IFR all over the place with the single GTN650 NAV/COMM, but it does have the monitor function.

 

[BobTurner]

In my area, trying to hear ATIS on the monitor frequency with the primary on ATC is an exercise in futility - ATC is so busy that it takes 10 minutes to get the whole atis. But a separate #2 receiver, running at the same time as #1 on ATC, works fine. The human ear/brain is pretty good at listening to atis while also listening for your call sign, and, if you hear it, shifting your attention to #1. The newer audio panels that channel different radios to different ears work even better, but really aren’t needed. I will say that having a full #2 com is just for backup. I cannot remember the last time I actually transmitted on #2. I guess I should try it, just to be sure it works!

 

[blaplante]

A LOT of Com radios in the installed fleet do not have simultaneous listen on a 2nd frequency.

Oh, yeah, we can just swap out the old King / Narco / whathaveyou for a new radio that has that function... for oh, say $1400...

At least in SoCal, trying to get in edgewise to *ask* to go off frequency is often an exercise in frustration.

Yes, this is an edge case application. You need to be a VFR pilot / plane, and have an older single Com, and have some better uses for your spare $1K.
AND, not want to be asking to go 'off frequency', for whatever reasons.

 

[blaplante]

Sharpening my pencil a bit more, I think it can be built for closer to $120 if you have a 3D printer to make your own case.

FWIW...
looks like zero interest.