I have been a ham for almost sixty years and in all that time I have owned two antenna tuners. My first introduction to an antenna tuner was a Heathkit AC-1 a perfect companion for the Heathkit AT-1 transmitter.
In those days power of the transmitter was rated in input power and the transmitter was rated at 30 watts. Not out, but input power. With a class C amplifier since this rig was CW only the efficiency was around 80%. This meant of course that about twenty to twenty five watts reached the antenna. Or did it? Considering at the time I had only an end fed Zepp and the swr was horrid in comparison to what we have today.
By taking a rather poor antenna and coupling it to the antenna tuner I was satisfied at that time with state side contacts. After all, radio was new to me then and I was a Novice class op thrilled to work any one outside my location. I did not own an SWR meter, or watt meter I was 15 years old and a very limited income.
So, with that tuner and a Heathkit transmitter I wanted to experiment with various and unusual antennas. I recall one day I loaded up a coat hanger, it was supported by two shade tassels and I was on the second floor of my mother and dad’s house. Much to my surprise another Novice returned my call in North Carolina. I have his qsl card to this day. Another day I loaded up some bed springs just to see if I could get out using such combinations. I did work a few fellows in the Louisville area with 599 reports on 80 meters. My next tuner I owned was a Johnson Matchbox, some of you old timers will recall this product. It was good for about 300 watts! At the time I had a much better antenna system then the Zepp. I had my first beam for 15 meters and inserted the tuner in the line.
I then noticed in bypass the swr was only a slight rise at worst a 1.2 to 1. In fact, most of the time the tuner remained off and I seldom used it for the next couple of years. I finally sold the Johnson Matchbox that was in the early sixties. I have not owned an external tuner since that time other then the built in tuners with our transceivers.
In reading this article you might ask yourself a question before you plank down your hard earned cash for a Tuner. The big question being if I really need an antenna tuner for my shack?
Let’s take a quick look at a few tuners on the market today and see about prices. MFJ has a 1500 watt tuner the MFJ 989 sells for $409.95. Vectronics $469.95 and of course the big prize a Palstar HF.Auto tuner for $1600 this one of course does everything except brush your teeth.
The added cost of the Palstar is automatic tuning, power and SWR meter and I do think this one has a frequency counter as well. All these features add to the price, the lower priced units are manual tune, work well and do what they promise. I suppose if you have become complacent in having to perform tuning chores and want it done automatically this one is for you.
We all know most hams are rather obsessed with idea of their antennas must have a 1:1 ratio, or I have heard many explanations for that statement. “You will not work out unless the swr is 1:1. Or”,“You can make your antenna much better if you have 1:1 ratio!” and the list goes on forever. If we review some facts about the loss of power forward to power reflected we come up with some interesting figures. Using 1500 watts as the output power and thirty watts as a reflected power our SWR is 1.33. If we increase the reflected power to 40 watts we have 1.39.
At fifty watts reflected this amounts to 1.45 and plus the maximum amount of reflected power I calculated using 70 watts of reflected power, the SWR becomes 1.55.
At 1500 watts output and a loss of 70 watts on your SWR is not a catastrophe. In figuring the loss of the amount of power lost in SWR, and the power factor involved Is that 70 watts going to make the slightest bit of difference in your signal with the station receiving your rf emissions?
No it will not, if we look at the db power factor it takes six db to raise your receiver s meter one s unit. Now six DB is four times the power, so if you are using a 100 watt rig, increasing the power from 100 watts to 400 watts will produce a rise of one s meter unit.
If you have some doubt that 70 watts of loss will make a difference in a kw output try this method. Next time you work a friend of yours, reduce your power from 1 KW to 930 Watts do not of course mention what you have done. Your friend’s s meter will remain the same reading as before. Of course do this with someone who has a steady signal so you will not be subjected to QSB. However, do you still need a tuner, well let’s take this example.
Tuners will not increase, or decrease the physical length of your antenna system.
Tuners will not add any more signal to your antenna system.
Tuners do one thing and that is match the impedance of your antenna to the same as your transmitter impedance.
With that you recall I mentioned I had loaded up a coat hanger, or bed springs. In this scenario let’s use a short piece of wire say eighteen inches long. Ok, this wire is not resonant or impedance matched for even the ten meter band. So, we grab our tuner, tune the SWR down to 1 to 1 and proudly proclaim to the world we have an antenna with 1 to 1 ratio. SO WHAT? We still have a very lousy antenna with high SWR without the tuner, it will not radiate any better in terms of what actually reaches the antenna system at the received station.
Your rig is fooled into thinking it has a perfect match, and you might convince yourself because you have a flat SWR you will get out fine. Granted someone will hear you even with a poor signal.
The real solution is to cut the antenna length properly for the bands you want. You recall 468/FMhz As you might recall the length for a 40 meter antenna with resonance at 7.1 mhz is 65 feet, or 32 1/2 feet for each leg. However, this antenna known as a dipole is the simplest of antennas to construct.
In my case I took the 40 meter antenna a step further and instead of a simple dipole I built a folded dipole. This antenna gives me a three DB gain over a dipole and it rests at the 70 foot level on my tower. How is the Frequency versus SWR curve?
This antenna is set for the middle of the band 7.150 kHz so this gives me both CW and side band operation. This antenna without the aid of an external tuner is 1: 1 until I reach the top end of the band around 7.297 kHz. At the apex of the band the SWR shows 1.2 SWR very good overall. Does this antenna work without a tuner, of course and do I need one for the folded dipole? No, it would be of no use I would gain little. What are the results with this antenna on 40? Well, being an avid Dxer you would expect over a 100 countries worked on this band. Let us say I have that figure doubled and almost tripled by using my folded dipole.
So how does my triband beam work without a tuner of any type attached to it? My triband beam works well at 80 feet, and has since I installed it. Again, 20/15/10 meter bands were set in the middle of the band and the SWR at the bottom of the CW band is I.3 SWR while in the center of the band the SWR meter barely moves, in fact measuring the reflected power indicates about two watts.
On the bottom of the cw band, the antenna shows about 30 watts reflected power, no big loss with one KW output. How has this antenna worked with no tuner? Let us say that my country total is over 3 1/2 times the minimum requirement for DXCC.
My six meter beam at 75 feet works well in the same manner, I do not work the very bottom of six, nothing there. Most cw takes place from 50.080 to 50.100 and phone interest on ssb falls off at 50.300. However, my beam is tuned to 50.125 and has about 300 kHz bandwidth on each side of the center frequency. Again, a tuner is just not needed since the SWR is around 1.2.
Point proven, but one more technical bit of information and that is the insertion loss of an external tuner. I have not found any one that really lists this information in the specification sheet of their product. Dropping back a few years with QST magazine I did find one insertion loss figure of .7 db or less. As an example say we have a ten watt transmitter and using a tuner we measure on the output side of the tuner only 8.5 Watts. I assume this is determined by the output of the tuner into a dummy load.
This translates to .7 db loss, so in effect even with a slight SWR you could lose as much power as you gain, or come out even? If you really want to determine loss in your tuner attach the output to a dummy load and then switch between operate and stand by. Why the loss of power, well tuners use a large inductor in the matching network. Inductors produce a loss. Same holds true for your trap dipole or tri-band beam some loss will occur.
Now I am not saying all tuners are bad, they have their place and if you are limited in space, or restrictions of your subdivision then a tuner might be your saving grace. No room for wire antennas, then go straight up with a good vertical and there are several on the market.
If you find you really need a tuner, then by all means buy one, but after careful review of your system if it does not merit the use of a tuner, well do not buy one.
As to built in tuners in my two Yaseu rigs, they work, but again I do not need them in the circuit. Just about all the time I am on the air I am driving one of two linear amps. My linear amps present an excellent match to the input circuits of the amplifier and no need to have them on at all.
However, on a few moments of wanting to try other bands, I have attempted to make my 20/15/10 meter beam work on 17. I have not been happy with the results since the SWR is around 3 to 1. One of these days I may construct something for 17 meters that is much more efficient. Until that time, well we just work the four bands I have with the present antenna.
Just a couple more items of mention, now we all know that solid state finals are not as forgiving as vacuum tubes. We also know that with high SWR some rigs, or linear amps have fold back circuits. The power is reduced in order to protect the final stages and prevent damage to other associated components.
My THP HL 2.5 allows up to 100 watts reflected power, this should be close to 2:1 and the protection circuits will shut down the amp. In most transceivers fold back protection is used and will reduce the power output if the SWR goes high.
Using a tuner after the linear will indeed fool your system, but at the same time mask the real problem. That is being a poor antenna, start at the basics, tune, prune, or add more height, but the real problem is the antenna.
With that I will leave this to be your own decision if indeed you need a tuner, or will you be fine without one?
Bill, K4LRX
