Yaesu FT857D: TCXO-9 Install
27th February 2022I’ve owned my FT857D since passing my Foundation certificate and its still doing me proud for mobile and portable operations where I like to use more than 10w that my Icom IC-705 will give. One thing I have noticed especially on RSGB VHF FT8 contest nights and even more on the UHF frequencies is drifting of a few Hz from when the unit is cold as it heats up-to operating temperatures.
What is a TCXO tho? A TCXO (Temperature compensated crystal oscillator) is a crystal oscillator with a temperature-sensitive reactance circuit in its oscillation loop to compensate the frequency-temperature characteristics inherent to the crystal unit.
From factory the FT857D came with a ‘reference TCXO’ module that provides a basic crystal but doesn’t give a high degree of stability to the frequency as the temperature changes, ambient and internal operating. Yaesu sell a TCXO-9 module that replaces the factory unit and will compensate the frequency of the crystal from the temperature so you end up with a highly accurate output. No so important on lower HF bands, but when using digital modes on higher frequencies having a stable reference frequency is very critical.
The installation was easy to do, with the radio in front of you, there are three screws on the top cover, one top centre and two towards the bottom. Leave the screws top and bottom of the speaker alone. On each side there are two small screws those need to be removed as well. In total you will of removed 7 small screws.
Lifting the top of the case upwards be careful of the attached speaker cable and rest the case top to the side, you’ll be presented with one of the main control boards:
Removal is easy, just grab the two white end connectors and pull upwards gently, the modules sit over two sets of pins. There are no clips or brackets to lock, just a friction fit over the pins.
Now to setup and do some testing on the air!
