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TKM Mx 300 Slide-In Replacement NAV/COM Radio Black Cover

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Part# 11-18835
MFR Model# MX-300B


The TKM MX 300 Nav/Comm is designed to replace the RT 328T, RT 308C, RT 328T, RT 328A, RT 528A, RT 328C, RT 528E, RT 328D, and RT 508A. The MX 300 is available in the black face plate shown left or in a beige face plate to match many Cessna panels. The MX 300 operates on 13.75 vdc w/7 Adc max current in transmit.

Note: We do not offer 8130 forms on these units.
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  • 760 Channel COM
  • 200 Channel NAV
  • Digital display with active/standby frequency with "Flip-Flop"
  • 100 Channel Memory
  • 8 Watt Min.
  • Noise Adaptive Squelch
  • 14 Vdc
  • 6 month Factory Warranty


  • Frequency Range Comm: 760 channels 118.000 to 136.975 Mhz Nav - 200 channels 108.00 to 117.95 Mhz Preselect channel storage capacity - 100
  • Frequency Stability: +/- .003%, -20C to 50C
  • Transmitter Power: 8 watts min.
  • Modulation: 85% min. with limiting at 90%
  • Sidetone: Adjustable to 20 mw into 500 ohms
  • Receiver Sensitivity: 1.5uV (soft) for 6db s+n/n or 1/2 flag Nav
  • Comm Selectivity: 6db @ +/- 7.5 Khz; 50db @ +/- 17.5Khz; 60db @ +/- 25 Khz
  • Nav Selectivity: 6db @ +/- 15 Khz; 50db @ +/- 35Khz; 60db @ +/- 50 Khz
  • Squelch: Noise adaptive squelch with manual override
  • Audio Output: 5 watts into a 4 ohm speaker; 40 mw into 500 ohm headphones
  • Demod Output: VOR adjustable from .25 to .75 arms
  • Weight: 5 lbs
  • Size: 6.03" wide x 2.875" height x 10.375" mounting depth
  • TSO: C34e, C36e, C37e, C38c, C40b
  • Frequently Purchased With
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Globalmex A Verified Purchase


January 19, 2024

Easy to use. Easy to install. Works well. Great alternative to invasive avionics install.

Rodney J Verified Purchase


June 8, 2021

works perfect!

Mike B
March 25, 2020

I’ve had an MX300 as my #2 NAV/Com since 2011–as long as I’ve owned my airplane. I recently had to send it out for repairs. Cost was $650 for repairs, plus labor for the local avionics to remove, ship and re-install. Still a lot cheaper than buying a new or used Nav/Com unit to replace it.

Lee C
September 27, 2020

I have owned two MX300 and two more of their other model which replaced Narco units. The radio is a good solid performer. I have had great luck in the past. HOWEVER, I understand TKM has been sold to a new owner. I see a 50% increase in the prices of radios, parts, and repairs.

January 22, 2020

I have 2 of these units. I had 5 repairs over the years. All repairs must be done by the TKM factory - no one else repairs these radios. Now TKM factory tells me they wont repair either radio because they are too old. They consider any radio older than 20 years old to be obsolete. They have chosen to not support 70% of the products they have sold.

Edward H
August 13, 2019


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Does the mx300 directly replace the Narco 12D?

The TKM MX 300 Nav/Comm is designed to replace the RT 328T, RT 308C, RT 328T, RT 328A, RT 528A, RT 328C, RT 528E, RT 328D, and RT 508A.

Q: Hi my airplane has an MX-300 and I am looking for a working spare. My cessna 152 has a 28VDC system. Is this MX-300 similar with the one on my airplane or is there a 28 VDC version of the same radio?

This is a 14 volt radio and will require a converter to work with your system.

Q: Does the TKM MX 300 have glide slope capabilities?

Per the owner's manual: The NAV receiver provides frequency selection for remote mounted Distance Measuring Equipment and Glide slope Receivers.

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