In the world of ham radio, being able to see the band is almost as important as being able to hear it. A panadapter or spectrum display turns a traditional transceiver into a modern, visual operating experience—but many classic rigs don’t provide an IF output. The KD2C HI-Z IF Tap Board solves that problem by giving you a safe, high-impedance way to grab the IF and feed it to an SDR without upsetting your radio’s IF stages.
What the KD2C HI-Z IF Tap Board Does
The HI-Z IF Tap Board is designed to provide a clean IF output for solid-state transceivers that don’t include one from the factory. The “HI-Z” part is important: the board presents a very high impedance to the IF circuit, so it doesn’t noticeably load or disturb the existing signal path.
Key Benefits:
- High impedance tap avoids detuning IF filters or degrading receiver performance.
- Provides a stable IF output for SDRs, panadapters, or external spectrum scopes.
- Small PCB (about 1" × 1.5") fits easily inside most HF/VHF/UHF rigs.
- Only three connections required: IF in, IF out, and power.
The board comes with model-specific documentation that shows where to pick off the IF in your rig and where to insert the tap. KD2C offers different versions of the board based on IF frequency, so make sure you select the correct one for your radio (e.g., 9 MHz, 10.7 MHz, 455 kHz, etc.) before ordering.
Example Install: Adding a Panadapter to the Yaesu FT-736R
In my case, I upgraded a Yaesu FT-736R by installing a KD2C HI-Z IF Tap Board and routing the IF out to an SDRplay RSP1A. Here’s the high-level process I followed:
- Open the radio and locate the RX unit.
Remove the covers from the FT-736R and identify the receive (RX) board. Remove any RF shielding that’s covering the area where you’ll be working.
- Drill and mount the rear-panel SMA jack.
Choose a clear spot on the rear panel for an SMA chassis mount connector. Carefully drill the hole, then vacuum out all metal shavings so they don’t end up shorting something later.
- Tap the IF input point.
Remove the RX unit and locate the D07 diode. Solder a short, shielded or well-routed wire to the anode of D07. This becomes your IF input to the HI-Z board. Reinstall the RX unit when you’re done.
- Provide power to the tap board.
For power, I used Pin 2 of connector J10, which provides a convenient 12V source when the radio is on. Solder a lead from J10 Pin 2 to the power input on the HI-Z board.
- Wire the IF output to the SMA connector.
Take the IF OUT from the tap board and run it to the rear-panel SMA connector you installed. Keep the run as short and direct as possible to minimize noise pickup.
- Mount the HI-Z board securely.
Using the supplied double-sided tape (or standoffs if you prefer), stick the IF Tap Board in a stable location inside the radio. In my install, ground was provided via the SMA cable, so I didn’t need a separate ground wire.
Pro Tip: Keep the IF input lead from the radio to the HI-Z board as short as practical. The longer that run is, the more opportunity there is for stray coupling, added noise, or instability.
Bringing the IF to Life with an SDRplay RSP1A
With the radio reassembled and the board installed, the final step is to connect an SDR and configure the software:
- Connect the SDR.
Use a suitable coax jumper from the radio’s new SMA IF output to the antenna input of your SDR—in this case, an SDRplay RSP1A.
- Configure SDRUno (or your SDR software of choice).
In SDRUno, go to the SETT. → ORIG tab, enter the correct IF frequency for your rig and board, and then enable the IF mode. This tells the software that it’s looking at an IF, not a direct RF input.
- Verify alignment.
Tune a known signal on the FT-736R and confirm that the signal appears at the correct frequency on the waterfall. If it’s offset, tweak the IF frequency setting slightly until it lines up.
Once configured, your FT-736R now has a full panadapter: you can see the entire slice of spectrum around your operating frequency, quickly spot signals, and visually tune across the band—while still using the FT-736R’s front panel and receiver as usual.
Things to Watch Out For
Important Considerations Before You Start:
- Confirm IF frequency and board version for your radio before ordering or wiring anything.
- Work clean: any leftover metal shavings from drilling can cause shorts later—vacuum thoroughly.
- Mind your ESD and soldering skills: you’ll be working near sensitive IF circuitry and diodes.
- Double-check power: verify voltage on your chosen power pin (like J10 Pin 2) before connecting the board.
- Document your work: take photos as you go so you can troubleshoot or revert if needed.
Conclusion: A Modern Panadapter for a Classic Rig
The KD2C HI-Z IF Tap Board is a small addition that makes a big difference. By adding a safe, high-impedance IF tap and feeding it to an SDR, you can give classic radios like the FT-736R modern spectrum scope and waterfall capabilities without compromising receiver performance.
The installation is very approachable if you’re comfortable opening your rig and doing basic soldering. Once installed and configured, you’ll wonder how you ever operated without a panadapter—especially on crowded bands or during contests and events where being able to “see” signals at a glance is priceless.
If you’ve got a favorite legacy transceiver that you’re not ready to retire, adding a KD2C HI-Z IF tap board and an SDR is an excellent way to extend its life and bring it into the modern SDR era.