Today’s antenna analyzers are probably the handiest piece of test gear a ham radio operator can own. Let’s turn the clock back 50 years. If you wanted to check to see where your antenna was resonant, you had only three tools to choose from. The inline SWR meter was probably the most common tool. Today, almost every HF radio has an SWR meter built in. Some hams would use a GDO (grid dip oscillator). This was and still is a very handy tool. It has various uses. To check your antenna you would attach a coupling loop to the feed point of your antenna and use the GDO to look for a dip in the meter as you swept across the numerous bands. This was mostly used for mobile antenna work. You could even use it to check the actual resonant frequency of you tower. The last piece of test gear that was used 50 years ago was a noise bridge. This is a very simple hand held instrument to use. But, if you were to go to a military installation or a commercial AM broadcast station’s antenna site, you would see a much more sophisticated type of Noise Bridge. The noise bridge would not only tell you the feed point resistance of your antenna, but it would also tell you what the capacitive or inductive reactance was of your antenna.
Remember one thing when it comes to using either of the above instruments or any of the antenna analyzers below, to get an accurate reading, you must be sampling at the feed point of the antenna. With some of the analyzers today, you don’t have to climb to the top of your tower to do so. More on this subject later.
With some of the analyzers today, you don’t have to climb to the top of your tower
Today we have the stand alone antenna analyzer. You no longer need to run a power cable from your house to the driveway to use your GDO to check your mobile antenna. You no longer need a radio to use either a noise bridge or an SWR meter. You actually don’t even need to have your ham ticket to design, built and test your antenna.
Today’s antenna analyzers take two readings, just like a noise bridge does. It reads resistance and reactance. R=resistance, X=reactance. From that point on, the onboard processor takes that information and feeds back so much more information to the end user. It calculates SWR, phase, return loss, and displays a smith chart and so much more.
Before you even think about what antenna analyzer you should purchase, you have to ask yourself one question. “What are you going to use your antenna analyzer for?” Are you going to sweep a frequency range, read the SWR and then just trim the antenna to get the lowest SWR at a given frequency? If so, you do not need a sophisticated type of an antenna analyzer. I see a lot of used expensive antenna analyzers posted for sale on the internet. They almost always reads the same. “I bought this not too long ago and now it just sits on the shelf collecting dust.” So many hams spend a lot of money purchasing what they think is the best antenna analyzer on the market and then just look at the SWR on the analyzer and nothing else. For some hams, that is more than enough information for their needs.
If you are serious about designing, building and matching more than a simple dipole to coax, you need an elaborate antenna analyzer. You can do some many things with an antenna analyzer. You are not limited to using it strictly with antennas. You can use it to adjust a trans match, adjust tuned inputs for an amplifier, set up a tank circuit in an amplifier, check a balun to see if is working, and check for return loss and more.
Before you even think about what antenna analyzer you should purchase, you have to ask yourself one question. “What are you going to use your antenna analyzer for?”
Rather than turn this into a, “how to use antenna analyzer” article, I suggest you do a search on the internet for, “MFJ-259B user manual” and look through it. It will show you how to use their antenna analyzer for more than just checking SWR.
One of the easiest and least confusing antenna analyzers to use are the MFJ-259 and 269 series analyzers. All you have to do is, hook the coax coming from your antenna to the analyzer, turn the analyzer on, turn the left knob to the frequency range you want to check and then turn the fine tune knob of the right while looking at either the display or the two analog meters to check for the lowest SWR. It’s that simple. The one down side of either of these two antenna analyzer is, it does not show if the antenna is capacitive or inductive reactant. Capacitive meaning the antenna is too short, inductive meaning the antenna is too long.
Let’s look into the more expensive antenna analyzers and focus on why one would need one. I’ll use myself as an example and where I needed more than just an SWR curve. I use a half sloper, fed off of the top of my tower for working DX on 160 meters.
The antenna’s feed point resistance is 40 ohms and has some reactance. This equated to a 2 to 1 SWR. At the base of the tower I wanted to see R=50 and X=0, zero means the antenna is resonant. I wanted 1850 kHz to be my resonant frequency. Once I knew what R and X was, I had enough information to design an LC network to be placed at the base of the tower. To build the LC network, I needed to know if the antenna was capacitive or inductive reactant. This provided me with enough information so I could build my network. As mentioned above, the MFJ’s I talked about earlier do not show whether the antenna is capacitive or inductive reactant.
And now it’s time to purchase your needed antenna analyzer. So here are some suggestions. As mentioned above, the MFJ 259 and 269 series analyzers are reasonably priced, easy to use and give you a lot of useful information.
NanoVNA
You don’t have to save your lunch money for months on end to own one of these. They have two models that I would suggest, the standard NanoVNA, $60 and the NanoVNA H4, $90. You have to watch out for clones when it come to the little Nano’s. Stay off of Ebay unless you know for sure you are not getting a clone. I’m not trying to promote a business, but R&L Electronics sells only the original NanoVNA’s.
These little guys give you the same information as some of the most expensive VNA’s do. There is only one down side to this item and that would be that it’s very menu driven and a little on the confusing side. Once you learn how to navigate the menu, it’s super easy to use. You can even carry it around in your shirt pocket. I chose the H4 model. First off it has a bigger display and second it can be programmed to use up to 401 sampling points. Sampling points has a lot to do with accuracy. The higher the rate the more accurate the readings will be.
Rig expert antenna analyzers: These are on the expensive side but very good hand held analyzers. The newer Zoom models are the ones you want to focus on. The reason being, these models use a higher sampling rate. I would suggest the AA-230 Zoom.
SARK
There are two models I want to address. First the SARK 100. I’ll keep this simple….JUNK. Stay away from this model. Now the SARK 110 is a top of the line and highly accurate analyzer. The only down side is its very menu driven. The one big upside is you can go as high as 10,000 sampling points as a stand-alone unit. It’s small and will fit in your shirt pocket.
Earlier I talked about taking your antenna readings at the feed point of the antenna. Enter OSL calibration. OSL (open, short, load) calibration is a way of canceling out your feed line. Let’s take a 100 foot length of coax. Hook it to your analyzer and then run OSL calibration by putting your open, short and load on the antenna end of the coax. Once calibrated, you can hook your coax to the antenna under test and the coax will be canceled out so the readings you see are the same as if you were to hook your antenna analyzer to the antenna’s feed point. Not all antenna analyzers have this feature. The NanoVNA, the Rig Expert and SARK110 have this feature. These three models can also be used in conjunction with your computer.
TDR (time domain reflectometer)
TDR is a really neat feature. The antenna analyzer sends a trace down the coax to look for a fault. Suppose a squirrel chews through your coax and you have no idea where the fault is? TDR will tell you. Again I will use my station as an example. My forty meter antenna crapped out, the SWR went through the roof. I knew the total length of my coax was 150 feet to the top of my tower. I ran a TDR plot and it showed I had a fault at the 60 foot point in the coax. The 60 foot point is at the base of my tower. At that location I had coupled two length of coax together with PL 259’s and a barrel connector. I took the connection apart and found the barrel connector was burnt and melted. I replaced both of the PL 259’s and bought a better quality barrel connector. Problem solved. The above three mentioned antenna analyzers have this feature.
There are so many antenna analyzers on the market and I cannot review or list them all. Stop by the club’s station most Wednesday evenings and I would be more than happy to discuss antenna analyzers and their usage.
