I have been trying a couple external Tuners with my IC-7300 transceiver, with mixed results. They actually both worked, but operation is a little confusing. The tuners I have tried so far are:
- Elecraft KAT-500
- LDG Electronics IT-100
The Elecraft Tuner is made for the K3-line but Elecraft has also made sure that it can be used with other Rigs. The LDG IT-100 is specifically made to be compatible with ICOM radios that use the standard 4-pin antenna tuner interface. This is a great interface, allowing flexibility to use a tuner with many Icom rigs. I do HATE the 4-pin connector that connects to the radio. It is a friction-mounted connector (no keys or tabs to press), but it is extremely hard to remove. Every time I remove it, I am afraid I am going to damage the radio. if you have to remove it from the rear of a radio that is on your desk, reaching over the back of the radio, good luck!
Every time we discuss external tuners on reflectors, a few people have to jump in and say that you need to have resonant antennas, so why would you ever used an external tuner, when the IC-7300 has a built-in tuner. The internal tuners in Icom radios will usually only match an SWR mismatch of 3:1. This is unfortunate, as Elecraft has had built-in tuners that handle 10:1 SWR mismatch for years. I had one in my K2. If you just need a slight tweak of your antenna to cover entire HF Bands, you may not need an external tuner at all. For the rest of us, external tuners allow us to greatly expand the Bands and Modes we can use with compromise antennas.
Elecraft KAT-500 Tuner
This is a great tuner, although not inexpensive. It is built to handle 500 watts, as a companion to the Elecraft KPA-500 500W HF Linear Amplifier. It has 3 antenna ports. It does a great job of tuning and, like most automatic antenna tuners, it is very LOUD when it has to search for a match. In fact, this is the loudest tuner I have ever seen. That is really my only complaint about it. If you go to a previously-used frequency, tuning is very quick and you barely notice the noise.
I do not use the power from my IC-7300 to power this tuner. The maximum current needed by the KAT-500 is close to the 1 Amp maximum current that the Icom rigs normally supply on the antenna tuner port. So I suggest using your separate station power supply for an external tuner such as the KAT-500. I connect the 4-pin connector to the radio, then connect the data plug to the Tuner and the power connector to my Station 12-volt power supply.
I had a chance to run this setup in the recent ARRL CW DX contest and have some new findings. during the Contest, I had to use the TUNE button on the KAT-500 to start the tuning cycle. Although the IC-7300 is supposed to disable the internal tuner when an external tuner is connected, it is not obvious to me that this happens. Even if I click the Tuner button on the 7300 to disable the internal Tuner, every time I tune on the KAT-500, it comes on again. I am looking into this and have had some discussion on the IC-7300 Forum. This no longer seems like an issue that is solved by correct power-sequencing of the 7300 and the KAT-500.
IMPORTANT UPDATE – After the ARRL CW DX contest, I discussed this with several others who use the Elecraft Tuner with ICOM rigs. What I found (with help from Fred WB4QOC) is that if you want to use the TUNER button on the IC-7300 to start tuning on the KAT-500, you must provide the 12 volt DC power from the Radio. Apparently the IC-7300 uses current draw on the Tuner Voltage pins to determine that there is an external tuner connected. I have now done this with success. Once you get it setup correctly, the KAT-500 integrates very nicely with the IC-7300 and the IC-7600 transceivers.
LDG Electronics IT-100 Tuner
This LDG Tuner is a perfect match for the IC-7300. If you do not need the flexibility of the KAT-500 or the increased power handling capability, this is what I would recommend. It comes with the cable you need to connect it to the Radio. So it is really just plug-and-play. With this Tuner, I do connect the power from the Radio. It is made to mate with the IC-7300 radio. Since it is being powered directly by the IC-7300, there is no power sequencing issue. Operation is simple – you just press the TUNE button on the Radio or on the Tuner and it seems to do the same thing. It can take several seconds to tune on a frequency for the first time. It is a little loud, but much quieter than the KAT-500 Tuner. I used an early version of this Tuner with my Ic-7000 in a Mobile setup for a number of years. It just worked flawlessly. I just bought the new one with hopes of installing it for Mobile use with the IC-7300.
UPDATE – The IT-100 Tuner, while it is a great partner for the IC-7300, is only rated for 30 Watts in Digital Modes. With the popularity of digital modes like FT8, especially with new Hams, this is something you must consider. I normally like to run 50-75 Watts when I use a 100 Watt-rated radio. If I use this Tuner, I have to cut the power by another 3 dB. I do not use Digital Modes when operating Portable or Mobile very often, but this would be an issue in my Main Fixed station.
Other External Tuners
It has been mentioned to me that there are other Tuners that can also be used with the IC-7300. MFJ makes some fine tuners. I have a remote MFJ tuner that I plan to try at some point. I have used it successfully with an IC-7600 and a Yaesu FTDX-3000. I suspect it will work fine with the 7300, but I will need to resort to the forced tone output by using RTTY or AM mode when Tuning for a match. That is a bit of a pain, but usually works with any RF-sensing tuner. If only all Tuner manufacturers would offer an Icom AH-4 compatible tuning interface.
Summary
Both of these tuners, and surely many others, may be used with the IC-7300. Operation of the Elecraft tuner with the IC-7300 is a little confusing, but it works fine, once you get the hang of it. Operation of the LDG IT-100 with the IC-7300 feels very natural and foolproof. It integrates as nicely as an internal tuner. If you are buying a Tuner just for the IC-7300, I would recommend the LDG IT-100. If you are using the KAT-500, you probably already have it to use with other radios.
The IT-100 integrates so nicely with the IC-7300 that it will be staying with that radio permanently, especially in a Mobile installation. I will be keeping the Elecraft KAT-500 matched with my IC-7600. I may try using the KAT-500 with my IC-7300 in a Mobile/Portable setup to take advantage of the higher power provided by the KPA-500 Amplifier.
Kg3v Ham Radio Blog 
With the 7300, do you need to turn the power down prior to starting the tuner?
Absolutely no need to do that. It reduces the output power for tuning and protects the radio from any problems with the antenna.
What is the difference between using a IT-100 and a Z-100Plus connected to the IC-7300 with a IC-PAC interface cable? Do they function identically?
Hi, I have no experience with the Z100 Plus, but it looks to me like it would work fine with the IC-7300. You would need the cable, as you said. I have had great luck with these small LDG Tuners. I had one in my truck with an IC-7000 for about 5 years.
Im having issues with connecting 7300 to LDG AT600 PRO. The tuner button on the readio dose not work but using controls on the tuner is fine. Are there any settings to consider with 7300?
I have not used this exact Tuner, but if you have the ICOM cable, it should certainly work. I am assuming the Tuner is getting its 12 Volt power through the 4-pin ICOM-to-Tuner cable. If still nt working from the IC-7300 front panel, I would call LDG. They have been very helpful in th epast, and I am sure they will get you going. I have used other LDG Tuners with the 7300, and was very happy with my results.
73, Tom
No one has mentioned the tuner extender that MFJ has made for a long while now. I did use it on an earlier LDG tuner a few times and it seemed to be able to tune almost anything anywhere. Of course the efficiency is alway is an issue. I am considering getting back on air and all my radios are beyond vintage now so a newer rig may have to be bought and the IC 7300 seems a reasonable choice and the internal tuner is limited so using the extender or the ability to do so is of importance as opposed to buying another external tuner.
Thank you for posting this very useful information. I’m a new ham, got my Technician license last May and have been on a Yaesu ft 60r. I passed my General exam yesterday and am looking at the IC-7300. Now I know the LDG IT-100 is a good compliment. Thank you.
Scotty KI5FBZ
Well, congratulations on being a new Ham. The IC-7300 is an incredible HF Radio at a great price, and the IT-100 is a great companion to your 7300. Enjoy the many aspects of Ham Radio. There are so many different things you can do, that one of the hardest things is to decide where to start. Nice problem to have. Enjoy many years of Ham Radio fun, learning, and friendhips.
73,
Tom, KG3V
I just got a new IC-7300 and a new LDG Z-100 Plus. The ic-7300 manual says if you use a NON ICOM external tuner, you must DISCONNECT the radios INTERNAL tuner. There is NOTHING in the manuals for both the ic-7300 and the ldg Z-100 plus that says a thing about turning the radios internal tuner off. The LDG Z-100 Plus was specifically designed to work with the IC 7300. Advice????
There have been some long discussions about this on the IC-7300 GROUP. I went through a period where I was afraid that the Internal Tuner was not being taken off line when I connect an External Tuner. If you are using the standard 4-pin MOLEX plug and a Tuner from a Company with major experience with the AH-4 Tuner interface, like LDG, I would not worry about it. Use the ICOM cable they supplied, and it will work fine. I believe the 7300 looks for an external Tuner at power-up, so just don’t plug in the Tuner to a the rig when it is already powered-up. You probably would not do that anyway.
73,
Tom, KG3V