After years of operation, my Elk’s SWR is now very high!
Before we let any Elk leave our shop and do its noble work somewhere on our big blue marble, we test it and make sure it is going to work for you. At some point, I often receive calls in the range of 15 seconds to 15 years after purchase with customers that find their Elk has a really high SWR. I am going to tell you a little secret about antennas – if built and maintained well, they are amazingly simple devices. There are no batteries. There are very few things that can burn out. Historically, the biggest danger to Elk Antennas is your OM or XYL backing over it with the motorhome. The next leading cause of failure are hurricanes.
There are two ranges of high SWR that customers contact me about. The first is in the 1.8:1 to 3:1 range. In most of these cases, there is an issue with one or more elements. An element may have become loose, or some corrosion may have accumulated between the threaded element insert and the threaded element screw. This is generally a really easy fix.
The next range of high SWR that I get calls about (less often) is the 10:1 to 20+:1 SWR range. In most cases (perhaps all?) this is not an issue with the antenna, per se. Here are some items to look at to help troubleshoot the problem.
1. Is the coaxial cable “hamfest special” coax? I don’t want to be the bearer of bad news, but so much of the coax – I’m talking the really cheap stuff – that you pick up at hamfests and swap meets is just not good. I am not talking down to you – I am with you on this. I purchased plenty of it myself only to find that the construction did not lend itself to truly being coaxial cable. I have cut some open only to find a single strand of wire running along where there ought to have been braid. Many customers swap out for known good quality cable and their problems go away.
2. Is the RF connectors (UHF (PL-259) or male N-Connector) screwed on properly to your radio/antenna analyzer and to the antenna. Before you just answer “Yes!”, do yourself a favor and give it a thorough inspection. Many times, the center conductor on your coax does not make contact with the connectors on your devices. You may have to do a continuity check with a VOM (volt-ohm meter, multimeter). N-connectors often make the best connections you could ever hope for, but they can also give you a false sense that they are screwed on tight and that not be the case.
3. Check that the elements are screwed on tightly.
4. DO NOT USE LOCTITE “RED” OR EQUIVALENT! Loctite “red” is a wonderful product to use when rebuilding the differential in your Jeep. It is not such a great product on your Elk Antenna where you want to pass alternating current. There is a place for anaerobic adhesives on your Elk, but there is a dielectric value to each product. Loctite “red” will allow the least amount of current to flow, Loctite “blue” will allow a little more, and Loctite “purple”, while still possessing dielectric (insulating effects) properties, allows the greatest amount of current to flow. I have had customers literally kill their Elks by saturating the element screws with Loctite “red”. The good news was the elements did not fall off! One customer – a decade ago – returned the antenna but had to hacksaw off the elements for shipping…
5. DO NOT PUT WOOD OR OTHER FOREIGN OBJECTS INSIDE THE ELEMENTS! I am not sure why someone would do this, but this has happened a few times. The claim is that it prevents water from getting into the elements. Well, a little bit of water is not usually an issue. However, wet wood adds a capacitive effect to each element and rendered the antenna – well, odd! So, do not put wood in your elements.
6. When connecting your antenna to an antenna analyzer – make sure you are using the correct RF connector for the band you wish to test. This has come up maybe two dozen times where otherwise really smart people have used the wrong analyzer input to test their Elk and received really high readings. Initially, I get called some really rude names, and sometimes they even hang up on me (pretty much never though). However, after re-inspection, they confirm that was the problem and their antenna is “fixed”.
7. When testing your antenna, you do not want to have metal objects – or even you – right next to the antenna. This will change your SWR and the antennas pattern. On a proper antenna range, the ideal is to have ten wavelengths of your testing frequency between the antenna and anything that may affect its performance. Ten wavelengths is not too bad for a VHF/UHF antenna, but if you are building a 160 meter antenna, you may have to rent a flat state for a weekend…
8. The black rubber end caps on the elements actually have an affect on the antennas performance. If you are missing an end cap or two (or three), it’s not the end of the world. The SWR and pattern of the antenna will change a little bit, so please keep those on. After the dual-band Elk 2M/440L5 was designed and tested to as close to perfection as could be attained, it was reasoned that rubber end caps should be added to protect the users eyes and other body parts. No one wants to see core samples of radio operators. Once they were added, the characteristics of the antenna changed, and the element lengths had to be slightly redesigned.
9. I only saw one of these, but the wire on the center conductor of the antenna’s RF connector could have a cold solder joint. Check it with a VOM, and email me. It will be taken care of. You can certainly re-work it yourself, if you like melting metal.
10. The length of the elements matter! Because the length of the elements matters, it is important that you put them on in the correct pattern. On both the dual-band Elk 2M/440L5 and the 70 cm Elk 440L8 antennas, the elements can be installed simply by feel. The antennas are set up like arrowheads – where the shortest elements are at the front (by the RF connector) and they get successively longer as you install the elements to the rear. The 1.25 meter Elk 220L6 antenna is a little different. The very first pair of elements in the front are not the shortest – but the second shortest. Why? Because to make this antenna resonate well with a two-foot long boom assembly, it was necessary to create what would otherwise be called a Log-Yagi antenna.
11. Check your coaxial cable for water intrusion. This can be challenging to find, but your antenna analyzer may be a great tool for this.
12. Remember, not all antenna analyzers are equal. Most will have your SWR fluctuating around. You may seen and SWR bouncing around from 1:1 to 1.6:1. The reality is your antenna is not magically changing, but your antenna analyzer actually is. Your antenna analyzer is a transceiver radio that injects a signal and does a number of tests – really quickly – to determine your SWR. All things being equal, and SWR should not be bouncing around, at least not due to the static devices of an antenna and feedline. If you are in an RF rich environment while testing, then all bets are off. You may ask me, “What are you using?” Well, I have one of just about every antenna analyzer that has been introduced in the last 20 years. My quick (and seemingly accurate) goto device is the Comet Antenna Analyzer. When I need more detail, or am actively designing new antennas, then I use a spectrum analyzer, signal generator, and return loss bridge. I have a couple of MFJ analyzers. I think they are pretty nifty because of their rich features and the price, but not as stable or accurate as several other devices that I have.