Updated June 11, 2026.
When we opened pre-orders for the RF.Guru RF Current Meter, we knew there was demand. The discontinued MFJ-854 had left a real gap in the practical ham-radio toolbox, and many operators were asking for a modern replacement that could be used in the field, not just on a lab bench.
Still, the response surprised us. In less than one month, more than 50 units were pre-ordered. That is a strong signal from the ham-radio community: operators want a simple, passive, analog way to find RF current where it should not be flowing.
The pre-order launch is now closed. The introductory launch price ended on June 1, 2026, and the RF.Guru RF Current Meter is now moving through production and fulfillment. We are building them as fast as we can to get the first units out to operators all over the world.
Why This Tool Matters
Many station problems are not caused by a bad transceiver, a mysterious tuner, or a cursed antenna. Very often, the real problem is RF current flowing on cables and conductors that were never meant to be part of the antenna system.
That unwanted current can appear on the outside of a coax shield, on USB cables, audio leads, CAT cables, tuner lines, power wiring, grounding conductors, tower control cables, or even metalwork near the station. Once that happens, the station wiring starts becoming part of the RF system.
The results can be familiar and frustrating: RF in the shack, hot microphones, noisy receive performance, distorted radiation patterns, unstable tuners, USB dropouts, audio problems, or SWR behavior that changes when you move a cable.
Not a Lab Ammeter ... A Field Tool
The RF.Guru RF Current Meter is a fully passive analog RF current indicator. It does not need a battery, charger, firmware update, app, or menu system. You clamp it around a cable or conductor, transmit carefully, adjust the sensitivity, and watch what the meter tells you.
It is not a calibrated laboratory RF ammeter. That is intentional. In real station troubleshooting, the most useful question is often not “what is the exact current in milliamps?” but “where is the current strongest, did the choke reduce it, and is this cable carrying RF when it should not?”
That makes it very useful for relative comparison:
- before and after adding a current choke,
- near the feedpoint versus near the shack,
- with and without a counterpoise,
- with different cable routing,
- on the coax shield versus control or power cables,
- at low power first, then higher power only when needed.
What the Meter Actually Detects
A coaxial feedline carrying only the intended differential RF current has equal and opposite currents inside the cable structure. From outside the cable, those intended currents mostly cancel.
But when RF current flows on the outside of the shield, or when a cable becomes part of an unintended return path, that balance is broken. The RF Current Meter senses the net RF current through the ferrite core. That is why it can show current on the outside of a coax shield while ignoring much of the wanted differential-mode current inside the cable.
This is exactly what makes the tool useful. It helps you see the current that should not be there.
Built Around Real Station Use
The RF.Guru RF Current Meter uses a large #31 ferrite-core sensing assembly, chosen for practical broadband common-mode current work across HF, VHF, and into lower UHF. It is designed for real installations, not only for tiny test leads on a lab bench.
The opening can handle cables or cable bundles up to approximately 2 cm / 0.7 inches in diameter. That means it can be used on many common ham-radio coax feedlines, station cables, control lines, grounding conductors, and cable bundles without dismantling the entire installation.
| Feature | Practical Meaning |
|---|---|
| Passive analog design | No battery, no firmware, no charger, no app. |
| Large #31 ferrite core | Useful for broadband RF current hunting from HF through VHF and into lower UHF. |
| Analog meter movement | Easy to see changes while moving along a cable or comparing choke positions. |
| Front sensitivity control | Lets you set a readable indication for relative comparison. |
| Three operating ranges | SENS / Low Power, MID / General Use, and QRO / High Power. |
| Approx. 2 cm cable capacity | Suitable for many coax lines, control cables, and station wiring bundles. |
Why Choke Placement Should Be Measured, Not Guessed
One of the most useful applications is choke placement. Many operators install a choke because they know they need one, but they still have to guess where the unwanted current is strongest.
The RF Current Meter changes that. Move it along the feedline and look for where the current rises, falls, or peaks. Add a choke, move the choke, change the cable routing, or add a second choke near the shack, then measure again.
That makes the tool especially useful with EFHWs, off-center-fed antennas, verticals, inverted-Ls, multiband wire antennas, portable stations, field-day setups, and high-power installations where small layout changes can make a big difference.
Why Analog Still Makes Sense
For this job, analog is not old-fashioned. It is practical.
When you are walking along a feedline, moving a choke, checking a USB cable, or comparing current on different station leads, an analog needle gives immediate feedback. You can see trends quickly. You can see peaks. You can see whether a change helped or made things worse.
No menu diving. No boot time. No batteries. No Bluetooth pairing. Just clamp, transmit carefully, compare, and learn what the RF is doing.
Building the Launch Batch
The first production run is now on the bench. Each unit is being assembled and prepared by hand in Belgium. The demand has been higher than expected, with more than 50 units pre-ordered in less than a month, so we are working through the batch as quickly as possible.
We know many of you are waiting for your meter, and we appreciate the trust and patience. This product exists because operators kept asking for a practical replacement for the discontinued MFJ-854-style tool, and because common-mode current remains one of the most misunderstood and under-measured problems in amateur radio.
The first batch is not just another product run for us. It is a sign that the community still values simple, honest RF diagnostic tools that help explain what is really happening in a station.
What It Is Not
To avoid confusion, it is worth being clear about what this meter is not:
- It is not a calibrated laboratory RF ammeter.
- It is not a VNA replacement.
- It is not a spectrum analyzer.
- It is not a magic SWR tool.
- It is not a lightning protection device.
- It is not meant to prove antenna efficiency from one reading.
It is a practical diagnostic meter for one of the most common real-world RF problems: current flowing on cables and conductors that were never meant to radiate, return, couple, or carry RF.
The Bottom Line
The RF.Guru RF Current Meter was built because hams asked for it, because the old tool disappeared, and because the problem it solves did not disappear at all.
Unwanted RF current is still one of the biggest reasons stations behave strangely. It changes patterns, raises noise, causes RFI, couples into equipment, and turns cables into accidental antenna parts.
The pre-order launch is now closed, the first production batch is being built, and fulfillment is underway. More than 50 units were pre-ordered in less than a month, and we are working hard to get them out into real stations around the world.
Thank you to everyone who pre-ordered, shared the product, asked technical questions, and trusted us to bring this tool back in an RF.Guru version.
Mini-FAQ
- Is this a replacement for the discontinued MFJ-854? Yes. It was developed as a practical RF.Guru alternative for the kind of RF current meter many operators missed.
- Does it measure exact RF current? No. It is a relative RF current indicator, not a calibrated laboratory RF ammeter.
- Does it need a battery? No. It is fully passive and uses an analog meter movement.
- What is it mainly used for? Finding unwanted RF current on coax shields, station wiring, control cables, power leads, grounding conductors, and other cables.
- Can it help with choke placement? Yes. It is very useful for comparing current before and after a choke, and for finding better choke locations.
- Is the pre-order launch still active? No. The pre-order launch discount ended on June 1, 2026. The product has now moved into regular production and fulfillment.
- How many were pre-ordered? More than 50 units were pre-ordered in less than one month during the launch period.
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