Introduction: Why Modify the Yaesu FT-857D?
The Yaesu FT-857D is one of the most compact and versatile HF/VHF/UHF transceivers on the amateur radio market. Beloved for its portability and all-band capability, it’s a go-to rig for mobile setups, QRP expeditions, and base stations with space constraints.
But despite its reputation, many seasoned hams know that the FT-857D has some quirks — particularly with CW key clicks, ALC behavior, and PTT interfacing with linear amplifiers.
In this post, we dive deep into real-world experiences and Yaesu’s own documentation to offer practical solutions. You’ll learn how to:
- Apply the key click modification
- Manage and measure external ALC voltage
- Secure internal wiring without damaging components
- Safely interface with Acom linears and other amplifiers
- Avoid short circuits during tricky soldering jobs
Let’s get into it.
1. Understanding the Key Click Problem in the FT-857D
What Are Key Clicks?
Key clicks are sharp, unintended sounds that appear at the leading or trailing edge of CW (Morse code) transmissions. They can cause interference and often extend several kilohertz beyond your actual signal — which is not only annoying to other operators but also a violation of spectral cleanliness.
Why Does the FT-857D Suffer From It?
Some older batches of the Yaesu FT-857D suffer from key click issues due to:
- Insufficient waveform shaping in the keying circuit
- Fast switching with minimal filtering
- Design limitations on earlier board versions
2. Yaesu’s Official Fix: The Key Click Modification
After complaints from users, Yaesu quietly introduced a hardware modification to address key clicks in newer FT-857D models — specifically from main board revision 07 onwards.
How Do You Know Your Board Version?
Unfortunately, Yaesu did not label these boards visibly with mod indicators. Even lifting the main board often doesn’t help identify the modification unless you know what to look for.
For older radios, you’ll likely need to perform the fix manually or send it to a certified Yaesu technician.
Download the Mod Instructions Here
FT-857 Key Click Modification PDF
Note: This mod is Yaesu-supplied but not officially endorsed for DIY. You perform it at your own risk.
3. DIY Mod Warning: It’s Not for the Faint of Heart
This is a surface-mount-level mod. The components are tiny. Without the right tools — such as a fine-tip soldering iron, magnification, and ESD protection — you risk damaging your rig beyond repair.
But if you’re confident, here’s a summary of what the process entails:
- Lift the main board to access the central underside.
- Locate the capacitor and resistor values as described in the PDF.
- Apply precise soldering without creating any bridges.
- Test the waveform after mod to confirm reduction in spectral artifacts.
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4. Securing Internal Wiring: Glue for Safety, Not for Life
Working with the mini DIN socket on the FT-857D is a lesson in patience. These tiny solder pads are crammed together, and even experienced hands can slip and create a short.
Here’s a simple trick:
After successfully soldering your wires:
- Apply a small amount of hot melt glue to the back of the pins.
- This stabilizes the joint and prevents strain on the delicate pads.
- The glue is non-permanent: if you ever need to rework it, you can peel it off cleanly.
Pro Tip:
Use low-temperature glue sticks to avoid heat damage to nearby components.
5. Adding a Phono Socket to TX Ground for Linear Amplifiers
Many hams want to connect their FT-857D to a linear amplifier, such as the Acom 1000 or 1500. Instead of tapping PTT lines from the mic or ACC port, a more reliable and clean method is to:
- Connect a phono socket to the TX ground pin of the mini DIN plug.
- Mount the phono socket on the rear panel or inside a small external control box.
- This offers a clean, dedicated feed for amplifier switching.
Why It Matters:
A poor or unstable PTT trigger can result in:
- Hot switching (damaging relays)
- Erratic amp behavior
- Clicking noises and RF spikes
6. External ALC Control and W8JI’s Insights
One of the world’s most respected amateur radio technical experts, Tom Rauch (W8JI), has done extensive work on ALC (Automatic Level Control) systems and their effects on linear amplifiers.
According to W8JI:
- Excessive or poorly filtered ALC can overdrive the amplifier.
- The FT-857D’s external ALC port often sends unpredictable voltages, especially under high SWR or mismatched loads.
Learn More:
Browse Tom’s site at https://www.w8ji.com and look up “ALC control” or “Yaesu ALC problems” for deep insights.
7. Visual Reference: Board Location and Connector Layout
While a diagram isn’t included in this post, many guides and user forums have posted underside board photos of the FT-857D. These images show:
- The capacitor location for key click fixes
- The central underside section for accessing solder points
- How the mini DIN plug pins are arranged for proper wiring
You can search QRZ forums, eHam.net, and ModMyRig for photo references.
8. Community Advice and Forums to Follow
Many users have added value to the FT-857D mod process with their contributions. Helpful forums include:
- QRZ Forums – https://forums.qrz.com
- eHam.net Reviews – https://www.eham.net/reviews/detail/2499
- Groups.io Yaesu lists – Particularly useful for Q&A on modding.
9. Final Recommendations: Should You Modify Yours?
Here’s a decision guide:
| Condition | Recommended Action |
|---|---|
| You own an FT-857D < board 07 | Proceed with key click mod (if skilled) |
| You use an external amplifier | Add phono socket for TX ground |
| You experience poor ALC control | Explore W8JI’s external ALC ideas |
| You’re not confident with SMD soldering | Send rig to Yaesu or avoid risky mods |
Remember, if the rig is functioning well for your operating style, you may not need to change anything. But for contesters, CW ops, or amplifier users, these tweaks can dramatically improve performance.
Conclusion: A Legendary Rig Worth Perfecting
The Yaesu FT-857D remains a favorite because it packs multi-band capability, remote mounting options, and solid TX performance into a compact form. But like many rigs, it benefits from a few aftermarket tweaks.
Whether you’re dealing with key clicks, ALC quirks, or just want a more stable PTT line, these modifications — though technical — are worth exploring.
But proceed wisely:
- Back up your settings
- Label your wires
- Test before full assembly
Your FT-857D can become a polished, clean, amp-friendly station with just a bit of care.
