Yagi Multiple Element Comparison

Yagi Multiple Element Comparison

By Kelvin Marsh, M0AID

November 2013

Back in October, following a discussion on the Active Elements reflector, I thought I would try an experiment gradually reducing the number of elements on my beam, and recording the results. I looked for the most distant station I could find, and it happened to be V6P in Micronesia on 20 metres.

The bearing was 22 degrees, and the distance was 8000 miles. Also, this was in the middle of the afternoon, and I would expect him to perhaps be stronger at other times.

The recording starts with the SteppIR antenna using 3 elements, and this is marked on the recording with 3 beeps. I then fully retract the Director, and the result has 2 beeps. Finally, I pull in the Reflector and this has one beep. I then repeat the sequence, but this time pull in the reflector first, followed by the Director. The final 3 beeps indicates a return to 3 elements.

I have to say, the difference is not huge between each retraction, but the difference between 1 and 3 elements is probably the difference between making a successful contact within a reasonable time, or spending significant time calling him without making yourself heard.

By the way, the signal strength on 3 elements was 7, and the signal strength on a single element was about 4. You
can judge the readability for yourself!

The MP3 recording can be heard by clicking the following link:
V6P on 20 metres

The following day, I conducted a similar test with KH0M, but this time on 12 metres. The bearing was 30 degrees, and the distance 7500 miles. The entity is the Mariana Islands.

This time I worked him quite comfortably using 400 watts before making the recording. The difference between 1 and 3 elements is much more noticeable. Again, you will hear 3 beeps for the 3 elements, and so on. In the first few seconds you will also hear how I reduce the HF hiss by turning back the RF Gain, and during the two and single element recording you can distantly hear a Brazilian station calling on the frequency from behind me. Using the Director and Reflector dramatically reduces any signal from the back of the beam. Whilst
KH0M was actually working split in the recording, attenuating unwanted signals from
behind you can be extremely useful.

The MP3 recording can be heard by clicking the following link:

KH0M on 12 metres

HamPod SteppIReader Accessibility Revieww

Evaluation of the HamPod SteppIR Reader

By Kelvin Marsh M0AID

March 2013

Photo of SteppIReader Keypad

I have been using a 3 element SteppIR antenna since Autumn 2010. It is a large antenna, and requires a rotator and a substantial mast. In other words, it represents a significant investment, both financially and in execution. The advantage of the SteppIR antenna is its ability to automatically adjust the element lengths, giving a perfectly matched aerial system on the majority of HF frequencies. As the antenna itself is outside, the operator will be controlling it by interacting with the SteppIR control box. This will sit on the bench, and in General mode will automatically adjust the antenna as needed. You can read the accessibility evaluation of the SteppIR controller elsewhere on this site.

If the transceiver interface board is fitted, the antenna is automatically adjusted by the radio, and Apart from the Power button, the only button in very regular use is the Direction button. On the original controller, this button cycles through Forward, 180, and Bi-directional modes. As my normal method of working DX Is to Search and Pounce, the ability to have the rotator pointing West, but within seconds have the beam electrically rotate to the East, is a terrific feature of the SteppIR. Within seconds you can check both the Long and Short paths, Whereas it might take you minutes to swing a traditional beam through 180 degrees and back.

The downside to using the Direction button, for a blind operator, is the constant need to check its status! Because the Direction button cycles through 3 positions on the original controller, I found I very easily lost track of my button presses, and constantly needed to remind myself of the direction.

I did this using an audible light probe. This is a pen shaped device that emits a tone when pointed at a light source. My SteppIR controller uses LEDs to show the direction of the Yagi, and I found I was feeling for the slight indentation of the LEDs, and then checking their status, on almost every long distance QSO. As a DX operator I’m listening for signals on the absolute limit, often 10 thousand miles away. If I found a weak signal in the Pacific, it was natural to also check the Long path, and to press the Direction button to rotate the antenna by 180 degrees. The result of all this was that I was using my light probe literally hundreds if not thousands of times over the course of a year!

OK, it’s taken me a page of meanderings to get here, but you can understand why the SteppIReader, http://www.hampod.com, caught my attention. It seemed I could send my SteppIR control box to Rob K6DQ, and he would make it talk!

If you have read my accessibility evaluation of the SteppIR controller, you will know the Setup menu is not accessible. The need to Calibrate, and create or modify the element lengths requires sighted help. Whilst you can live without this access, the SteppIReader gives you spoken feedback, and complete independence.

My SteppIR control box took less than three weeks to travel to Rob K6DQ and back. I don’t think I have been so excited to receive a parcel
for a long time!

The control box functions in exactly the same way as it did before the modification, but is now fully accessible. I think I would have purchased the mod just to
have the directional modes spoken, but of course there is so much more to it.

The SteppIReader comes with a 4 button keypad and speaker unit that plugs into
the rear of the controller. The only visible modification to the SteppIR control box itself is the addition of the port for the new keypad.

The LCD display on the SteppIR control box has two lines of 16 characters. The first button on the SteppIReader keypad reads both lines of the display, plus the antenna direction which is taken by new internal connections to the LED’s.

Button one therefore reads the control box mode, the frequency, and the direction.

Typically, it might say:
‘General Mode, 18.050mHz, 180.’

Button 2 reads the top line of the display, and button 3 reads the bottom line. Button 4 toggles automatic speech on and off.

I have the original SteppIR control box, and in Ham mode the antenna can be adjusted manually. As the band buttons are pressed, the controller’s frequency is now spoken by the SteppIReader. ** I understand the terminology for General and Ham modes has changed in the new SDA 100 controller.

In general mode, the antenna is adjusted automatically if the interface board is fitted. In this scenario, the frequency is now spoken as new bands are selected using the radio, and is again spoken as the antenna adjusts every 50kHz, as you tune through a band. I really like this feature, as it is wonderful to have the SteppIReader unobtrusively telling me what the antenna is doing.

There is a potential to damage the antenna if high power is used while it is adjusting, and it can be very easy to miss the visual indicator, even for sighted users. The SteppIReader handles this by beeping when the antenna elements are moving.

With the introduction of the SDA 100 controller, the little used Options menu has moved to the main Setup menu. This means the Option menu is now displayed on the LCD display, and is spoken by the SteppIReader. The options menu is still accessible using a light probe on the original controller, and I would imagine the inclusion of spoken prompts would have required a lot of complex internal connections for very little benefit.

Undoubtedly, the major achievement of the SteppIReader is the complete access it gives to the Setup menu. The real excitement for a blind operator is to now be able to use the Create/Modify menu. This allows the operator to independently adjust any of the elements, and save the setting. I won’t write pages on the Setup menu, but its use is much more easily explained in the audio demonstration on this page. Also, if you own the original SteppIR controller, the SteppIReader gives you full control over the Calibration and Retraction functions.

Finally, I need to mention the SteppIReader’s own Configurability. The volume of the voice can be raised or lowered by holding buttons 1 and 2, and the configuration menu is entered by holding button 3. Hear you can tailor the voice to your requirements with Volume, Rate, and Tone adjustments, and change a host of parameters. the configuration even allows you to enable or disable speech for various constant indicators on the display, such as the letter M that is shown when the antenna lengths have been modified, or the letter P that is shown when the 6m passive element has been added. Just in this respect, the understanding that there might be a need to suppress unnecessary repetitions on the display is outstanding.

In my experience, it is unusual to find a third party accessibility solution for a piece of amateur radio equipment, and almost unheard of to fine one with this level of technical integration. This is a 10 out of 10 product, and is truly breathtaking in its concept and application.

Related Downloads

HamPod SteppIReader MP3 Demonstration
HamPod SteppIReader Text Manual

MFJ 1786 Accessibility Review

Active Elements – working to improve accessibility for radio amateurs with disabilities

Review of MFJ-1786 Magnetic Loop

By Ian DJ0HF

March 2013

Hi,

my name is Ian, my callsign is DJ0HF/G3ULO and this is a review of the MFJ-1786 Magnetic Loop antenna for the Active-Elements web-site.

The MFJ loop is approximately 1 metre in diameter, made from thick aluminium tubing and the tuning capacitor and motor of the loop are enclosed by a thick black ABS plastic housing which also allows the loop to be bracketed onto a mast and it can be used on any frequency between 10 and 30Mhz.

The coaxial cable from the loop carries both the RF signals and the voltage to drive the motor and tune the loop and connects with the controller unit which is mounted in the shack.

I have owned the loop for a number of years and have it mounted in the loft on a short wooden stub mast, my loft is not very large but I have mounted it as far away from any metal as possible and oriented for maximum radiation in the East/West direction. My loft doesn’t have any metal foil lining in the eves so there is just the heavy concrete roof tiles between it and the outside world.

For those who have never used a loop, they are usually mounted vertically and if you look at the loop rather like a polo mint, then the minimum radiation occurs through the hole which for me is North/South and the maximum radiation off of the ends of the loop (for me East/West) and the radiation pattern has the typical dipole figure eight pattern which I can confirm is the case with the MFJ loop.

The advantages of a magnetic loop are that you get a fairly effective antenna in a very small space (1 meter diameter), the disadvantage is that you have to tune the loop very accurately for the frequency you are working on. Though for reception you can listen plus or minus 100Khz or so on most bands and still hear most signals but for transmitting you do need to get the tuning on the nose for good results.

The tuning is done using the remote controller in the shack which requires a 12 volt power supply, which normally comes with the controller and is for 220V AC. The controller has 7 buttons and a crossed needle SWR meter. There is a power on button and lamp on button to illuminate the meter. There is also a Range High/Low button to set the SWR meter for 300W or 50Watts full scale deflection. The maximum power allowed for the loop is actually 150 Watts. I did once try 300 Watts and the loop was fine but the controller didn’t like it and started to smoke. Normally I use 100 Watts which is no problem.

The other 4 buttons are 2 coarse up/down and 2 fine up/down buttons and there is more than one way to tune the loop but this is how I usually do it.
On receive I depress either the coarse up or down button which locks depressed and the motor starts and begins rotating the butterfly capacitor on the loop. In the receiver I hear a weak interference signal from the motor (typical motor hash) and as the loop approaches resonance the interference gets louder and louder on my receiver normally ending up around S8 to S9 and I then press the coarse up or down button again to release it. I’ve usually then gone just past resonance so I press and hold the fine tune up or down button to go back to the resonant point where the S meter reading is highest and that’s it for receive. On transmit I then send a carrier and just use the fine tune up or down button to reduce the SWR to minimum, usually below 1.2:1 and I’m ready to transmit. Of course if I wander up or down the band or change bands then I need to retune the loop but that’s the price you pay for using a Magnetic loop.

The other way to tune the loop is to transmit say 10 watts or so of carrier through it and depress either the coarse up or down button depending on the direction you want to travel and wait until the controller issues a tone indicating it has found the resonant frequency, it then automatically stops the motor and you just have to press the coarse up or down button again to release it. In reality you may still have to jiggle the fine up and down buttons again to get the minimum SWR. A VI operator would need some sort of audio indication of minimum SWR to be able to tune the loop effectively.
There is an adjustment for the speed at which the motor rotates so you can set it to whatever you are comfortable with. A slow speed will make tuning easier but takes a bit longer. I tend to use a relatively slow speed though too slow and the fine buttons may not start the motor at all so there is a minimum you can realistically use.

But the important thing is how well does it work in practice and my first comment would be surprisingly well. Obviously if you can get up a multi-band 3 Element beam then you are not going to bother with a Magnetic loop antenna but many of us are not that lucky and in this situation the Magnetic loop can be a useful solution.

Here I have an FD4 Windom antenna running down the garden, this is an 80 metre dipole but fed offset (about 1/3rd of the way along it’s length) with a step down Balun to match the 50 ohm coax and has a fairly low SWR on 80, 40, 20 and 10 metres. Though works on the other bands with an ATU. I also have a 10 Metre Dipole in the loft.

The lowest usable frequency with the MFJ-1786 is 10Mhz and on this band it is usually around 2 S points or so down on the FD4 at best which is not surprising. Though as 10Mhz is nearly all CW the 12db drop in signal strengths still allows lots of contacts around Europe and beyond, but obviously I normally use the FD4 on this band.

The loop starts to do much better when you get to 14Mhz on this band the signal strength on the Loop is normally around the same as the FD4 in the East/West direction but a couple of S points down for stations located North or South, showing that the loop has real directivity. Whereas the FD4 being really an 80 metre dipole has lots of lobes and becomes almost omni-directional on all the HF bands from 20 Metres up.

In the direction of the loop East/West signals are rarely much down on the FD4 and sometimes up to 3db stronger on the loop. This applies to most signals around Europe and also most of the USA, though I notice that the loop does less well on the very distant DX such as Japan etc. Indicating that the radiation angle of the loop is not really low enough for this DX. I had thought about trying to tilt the loop to lower the angle of radiation but have never got around to trying it. I’ve worked many W/K stations on 20 Metre SSB with the loop.

On 15 metres my best DX is VK and again the loop works as well or better than the FD4 on this band in the East/West direction. On 10 metres it is the same though the 10 metre Dipole usually out performs the loop by 3 to 6db.

Commercial loops are not cheap and the MFJ-1786 is no exception but it really can allow you to put out a reasonable signal on 10 to 30Mhz from a very small space indeed. If you mount it somewhere where it can be touched then be very, very careful indeed as there are thousands of volts generated on the loop which can result in very nasty RF burns even on quite low power. If you really want to get the maximum out of the loop then being able to rotate it through 90 degrees is the way to go and you can either peak the signals in a particular direction or null out signals you don’t want to hear. I’ll get around to doing it one day.

Would I buy the MFJ-1786 loop again if I was looking for a compact HF antenna, the answer for me is a most definite ‘yes’. Just don’t expect it to compete with Kelvin’s (M0AID) SteppIR.

Related Downloads

None

SteppIR Antenna Controller Accessibility Review

Active Elements – working to improve accessibility for radio amateurs with disabilities

Accessibility Evaluation of SteppIR Antenna Controller.
href=”https://kelvinsite.files.wordpress.com/2013/03/steppir-control-box-photo-for-review.jpg”>picture of steppir control box

By Kelvin Marsh M0AID

March 2013

In Summer 2010 I was looking to replace my 3 element 3 band HF Yagi, and I wanted the new beam to work on as many HF bands as possible. The SteppIR antennas were very attractive as they mechanically adjust the length of the elements, giving a good match on the chosen band. I wanted the 3 element SteppIR, with the 30m and 40m option. This would give me coverage from 6m to 40m. The elements are adjusted by moving a metal tape inside a hollow fibreglass tube, and the lengths are measured accurately with the use of stepper motors. I felt the antenna would be ideal, provided I could operate it without sight! After a lot of research, and a long chat with Tim GI4OPH, I was reassured, and I went ahead and bought the SteppIR.

In 2010 SteppIR were selling their antennas with the original control box, and this has now been replaced with the SDA 100. I am basing this evaluation on the original controller, but the new SDA 100 controller has similar accessibility issues, albeit with some noticeable changes. Although I have not used the SDA 100, I have read the manual, and feel able to add a few comments.

The original control box has an LCD display top left, and below the display are a row of square buttons for band selection. To the right of the display is the Direction button, and below this the Up and Down buttons. At the top right is the Power button, and below this the Mode and Select buttons. My controller has 6 band buttons and I understand this will vary depending on the configuration of the SteppIR you purchase. ** The SDA 100 controller has up and down buttons for band changes, but does not have dedicated buttons for each band. Please listen to the MP3 recording for a description of the SDA 100 control box layout.

In its basic configuration, the control box is used manually to select the element lengths for the operating band. The Up and Down buttons will move the elements by 50kHz for fine adjustment. ** Adjustment can be finer on the SDA 100.

In reality, it is slightly more complicated than this, as some of the band buttons cover two bands. For example, on my controller, the first button is used for both the 30m and 40m bands, and the sixth button is used for the 10m and 6m bands.

The 4 remaining dedicated band buttons can be used to cycle through preset points within the band. For example, a press of the 15m button can adjust the antenna for 21.050mHz, the next press moves to 21.200mHz, and a further press moves to 21.350mHz. To complicate things further, if a press of the 15m button took you to 21.200mHz, and you then moved to another band, the frequency would again be 21.200mHz when you next press the 15m button. This behaviour can be extremely useful, but because you do not always returned to the same known point, for example 21.050mHz, using this system without sight requires a good memory and a lot of discipline, mainly because you might not use 15m again for several weeks, and might easily forget it was last on 21.200mHz. If you use this manual approach for adjusting the elements, one solution is to use an accessible SWR meter to determine when the SteppIR is resonant. Tim GI4OPH explains his own ingenious approaches in the Comments following this evaluation.

Saying all this, you will imagine my appreciation when I discovered the control box can be fitted with a transceiver interface board! This is an optional extra, and the interface allows your SteppIR antenna to be driven by your radio. As you switch to a band, the SteppIR automatically adjusts. As you tune through a band on the radio, the antenna automatically adjusts every 50kHz. This means there is no need to ever press the band buttons! If you accidentally press a Band button or the Up and Down buttons, the antenna will attempt to change length, but will then immediately return to the correct setting as the radio is polled. This is how I use the SteppIR controller, and the transceiver interface removes any concerns over frequency adjustment.

There are however several other features on the SteppIR control that either cannot be used at all, or require other strategies. One of the most useful features of the SteppIR beams is the ability to electrically rotate the antenna by 180 degrees, in just a few seconds. The Direction button allows you to select forward, 180, and bi-directional modes. The same button is used to cycle through the three directions, and the status is indicated by two small LEDs. The LEDs are slightly recessed and can be located and interrogated with an audible light probe. ** The SDA 100 controller now has three buttons for selecting the direction. “Norm” for normal forward direction, “180” for reverse direction, and “BI (3/4)” for Bi-directional when controlling a Yagi antenna or three quarter wavelength mode when controlling a vertical.

The Options menu is the place you perform one off setup, such as telling the control box you have the 30m/40m kit, and the extra passive element for 6m. The status of these options can also be determined using an audible light probe. The Options menu is accessed by holding the Mode button for three seconds. ** Access to the Options menu on the new SDA 100 controller has been integrated into the main Setup menu.

Undoubtedly the area with the least accessibility is the Setup menu. Here you can Test the motors, return to factory defaults, select the make of radio, Create and Modify antenna lengths, and Calibrate and Retract elements. Whilst it is possible to memorise the key strokes for some of these functions, the antenna customisation options available in the Create Modify menu are not accessible.

It is likely you will occasionally want to Calibrate the antenna. If you have a power cut when the SteppIR is adjusting, you may find a calibration is required to get back to the correct element lengths. Also, you may more frequently want to retract the elements if there is an electrical storm, or the system is not to be used for a while. Fortunately, I found I could program one of my band buttons to memorise the retracted position, and so just one button press would achieve this without the need to enter the Setup menu. ** The SDA 100 controller has a dedicated button to Retract the elements.

The SteppIR antenna can be damaged if more than 200 watts is transmitted while the antenna is moving. There is a visual indication on the display for element tuning, but no audio cue. There can be some electrical noise on the receiver itself when elements are moving, and Tim GI4OPH describes how this can be useful in the Comments below.

There are a couple of options available to add reliable aural feedback for element movement. These include the SteppIR Tuning Relay Unit from N8LP, and the HamPod SteppIReader from K6DQ. Both of these units are soon to be evaluated on the Active Elements site. ** An additional tuning relay board can be fitted to the SDA 100, and this will prevent RF damage, by interrupting the amplifier’s PTT circuit when the elements are moving.

In theory, you do not need to use an ATU with this antenna. As the antenna can be adjusted for every frequency, you should always have a perfect match. If required, it is very easy to make small adjustments to element lengths and get a low SWR, but you will of course need an accessible SWR meter to check the resonance.

In summary, The SteppIR antenna works automatically if a transceiver interface board is fitted, but there is no accessibility to the Setup menu. The antenna can be used manually with the aid of an aural SWR meter, but the interface board makes adjustment automatic. For complete spoken accessibility, please read the shortly to be published evaluation of the HamPod SteppIReader from K6DQ.

Comments

From Tim GI4OPH:
I also have the rig interface capability, however as I tend to do a fair bit of hopping around from band to band, I prefer to adjust the Steppr manually when I need it to be resonant.
Regarding the status of the 30/40M selection button, one can normally tell by comparing the loudness of received signals, and indeed even by the general noise level, on which band the antenna is currently resonant.
If in any doubt, one dit at low power is enough to trigger an audible warning from my P2000 swr/power meter. Again I use the P2000 meter as an indicator to ascertain which segment is
selected on those bands with multiple frequency ranges. When the tapes are moving, the motors seem to produce some electrical noise, which is picked up by the receiver. This has been a source of some complaint on the Steppir reflector, however I personally find it advantageous, in that whenever the hash is present it informs me the antenna is tuning.
I suppose some of these methods are a little unorthodox, but it works for me smile!

Related Downloads

SteppIR OriginalControl Box MP3 Manual
SteppIR SDA 100 Control Box MP3 Manual

HF Inverted L, dipole, and Yagi MP3 Comparison

One of the most common questions from any amateur new to the HF bands is, what antenna is the best? This is a question that is almost impossible to answer simply, and you can guarantee everyone has a different opinion! By the way, the word ‘antenna’ is interchangeable with ‘aerial’, they both mean the same!

Generally, a large aerial is best for the low end of the HF spectrum, where the wavelength is long, and a much smaller antenna will give you better results on the higher HF frequencies, where the wavelength is shorter.

This is the main reason many amateurs will use more than one antenna, but just as many will use one aerial, either a large wire one giving better results on the low bands, or a small aerial favouring the higher bands. As they are using just one antenna, they accept it will be a compromise and work better on certain bands than others.

If the aerial is resonant on a given frequency, this means it is exactly the right length. This also means the correct impedance is seen by the transmitter, and all of the power generated by the transmitter can be radiated through the antenna. The aerial is said to be a good match.

If you have an aerial that is too long or too short for the given frequency, the aerial will not be resonant, and the transmitter will not be able to transfer full power, the aerial is therefore a poor match.

Fortunately, if the antenna is not too far away from resonance, it can be matched with a matching unit, otherwise known as an Antenna Tuning Unit.

The same is true for received signals, the longer or shorter the antenna is from the resonant length, the poorer the incoming signal will be unless matched. If the aerial is far too long or far too short it may be impossible to match, depending on the matching unit.

If you have a small garden, the most practical solution will be to have just one antenna. Fortunately, one antenna can be made to have multiple band characteristics, and there are a variety of methods employed to give low impedances on multiple bands. The antenna will still be a compromise on certain bands, but not everyone has the space needed for an Antenna Farm!

In my experience, it can be important for a blind operator to use a low impedance antenna. If the aerial has low impedance characteristics on multiple bands, it is likely the operator will be able to match the aerial using the automatic antenna tuning unit built into the radio. This built in antenna tuning unit or ATU will only have a limited range, and only be able to deal with small impedance variations.

The aerial I have used for many years is the trapped dipole. It is a wire antenna and is T shaped in profile. The feeder rises vertically to a T piece at 40 feet high, and the signal is radiated by the wire element, extended each side of the T piece. The overall length of the wire is 106 feet, or 53 feet each side of the T piece. Each leg of the element contains a 40m trap. This means that moving from the T piece, the wire extends for about 33 feet, there is then the trap, and the wire extends approximately a further 20 feet. On the 40m band, the traps isolate the final 20 feet of wire on each side of the dipole, but the whole length of the antenna is used on each of the other bands. Because of the 40m traps, The trapped dipole can be tuned on multiple bands with an internal Antenna Tuning Unit.

My second HF antenna is a Yagi beam. It is a Steppir 3 element Yagi, and the elements mechanically adjust to the correct length for the chosen frequency. The advantage of a beam is its ability to focus the signal in the chosen direction. Whilst most serious DXers (hams wanting to work long distances) will use a beam, they are relatively large, and require a strong mast and a method of turning or rotating the beam. The Steppir is a 3 element beam on 10m to 20m, and a rotary dipole on 30m and 40m.

The subject of this review is the trapped inverted L with very limited grounding. This antenna is more suited to a smaller garden, and gives access to all the HF bands. I literally wince at the prices of some of the small multi-band verticals, but my trapped inverted L was homebrew.

Basically, the trapped inverted L is equivalent to just one leg of my trapped dipole. The length is 53 feet, and the 40m trap is about 33 feet from the feed point, with a further 20 feet of wire to the end.

The feeder, or in this case the coax, runs along the ground to the base of the aerial. Here we mounted a small connections box on a copper ground rod driven into the earth. The coax is split, with the outer screen connected to ground, and the inner conductor bonded to the base of the inverted L wire.

With all antennas, it is important to get it off the ground and as far from surrounding obstructions as possible. In my case we used the bough of a tree to take the wire vertically up by about 20 feet to a pulley, and the remaining 33 feet was pulled horizontally to another support. If you don’t have a tree handy, your pulley could be at the top of a 20 foot pole.

As you can see, you now have an inverted capital letter L. Ideally, the vertical section needs to be at least 20 feet high, but can be as high as you can get it. The higher it is, the less wire will be left to pull horizontally.

So, my inverted L rises vertically 20 feet. Turns at a right angle and runs for about 13 feet to the trap, and then continues horizontally for the remaining 20 feet.

Ideally, the antenna’s grounding would be much more than one ground rod. I have no doubt it can be improved by adding radials, but this review is to see how the basic aerial performs. If you have a small garden, you will not have the space for radials.

In this RX comparison of the trapped inverted L with my other HF aerials, I have made recordings on each of the HF bands. I have marked the start of the inverted L with one beep, the dipole with two beeps, and the Steppir with three.

On 80m you will hear LY1TR in Lithuania, some 1100 miles. Firstly the inverted L followed by the stronger dipole, and then the sequence is repeated. Interestingly, RA4LHD in European Russia calls in at a distance of 1800 miles, and I think he is slightly stronger on the inverted L.

80m LY1TR

On 40m we hear GB4C in England, this is a local contact. Firstly he is quite faint on the inverted L, primarily because the inverted L is vertically polarized, and will favour a longer distance. There is not much to choose between the trapped dipole and the rotary dipole of the Steppir which is broadside to the station.

40m GB4C

Again on 40m we hear Jr1CFP in Japan at a distance of 6000 miles. The inverted L is slightly stronger than the trapped dipole, and the Steppir is the strongest, rotated towards the station.

40m JR1CFP

On 30m we hear SD7W in Sweden on IOTA EU-138 at a distance of 1000 miles. I think the inverted L is slightly stronger than the dipole.

30m SD7W

Again on 30m we hear ZP6CW in Paraguay at 6200 miles. Here, the inverted L is noticeably stronger than the trapped dipole.

30m ZP6CW

On 20m we hear EG5INT on a Spanish IOTA Island with a distance of about 800 miles. Here the inverted L is stronger than the dipole and not far off the beam. We hear the inverted L followed by the trapped dipole, then the Steppir, and finally the inverted L again.

20m EG5INT.

On 17m we hear VK2DX in Australia at about 9500 miles. Following The sequence of three, the inverted L is repeated.

17m VK2DX

On 15m we hear W7VJ in Washington at 4800 miles. The inverted L is receiving almost as clearly as the 3 element at over twice the height. I’m sure the beam would be showing a higher signal strength, but in terms of clarity there is not much to choose between them.

15m W7VJ

Again on 15m we hear W0IZL in Nebraska some 4200 miles.

15m W0IZL

On 12m we hear KU1T in West Virginia some 3700 miles. The inverted L is much stronger than the dipole, but there is noticeably much less noise on the beam.

12m KU1T

On 10m we hear 9A3TY in Croatia at 1000 miles. We hear the three antennas, and then the inverted L again. The inverted L is a workable strength, but with heavy QSB on the final clip.

10m 9A3TY

Again on 10m we hear KH7Y in Hawaii a distance of 7200. Faint on the inverted L, no copy on the dipole.

10m KH7Y

In summary, the trapped inverted L is suitable for a small garden, and is relatively low profile above ground, and has a tiny footprint on the ground. My antenna cost less than the 20m of coax used, and the 40m trap can be bought if you can’t make one. My inverted L was positioned down the garden, and pulled back to the house. I mention this because the horizontal part of the aerial is directly above the coax lying on the ground, and I recall reading somewhere this is desirable. Perhaps the coax acts as a counter poise.

HF Vertical, dipole, and Yagi MP3 Comparison

I thought the following might be interesting for the newcomers to the hobby, and help explain why many amateurs use more than one aerial. I took delivery of one of the low cost verticals this week, and made some comparisons with my trapped dipole. For interests sake, I also included my yagi, just to see if the cost and effort was justified .

We mounted the review X80 vertical, from the Snowdonia Radio Company, on Wednesday evening 15 March 2011. It’s on a metal stake next to the corner of my fish pond. We used an antenna analyser, and established the 80m SWR was 6 to 1, but all the other HF bands 40m to 10m were well under 2 to 1. There were no radials used, in line with the suppliers recommendation, but I think this type of vertical might indeed benefit from them…

As expected, the X80 performed better as I went from 80m to 10m, and the dipole was better in the reverse direction.

As signal strengths are difficult for me to determine accurately, I’ve recorded MP3 comparisons over the last three days on 80m through to 10m. I’ve deliberately selected signals right on the limit, to show the capabilities of the aerials, after all, there’s little point in comparing strength 9 signals on the doorstep. I’ve used 3 antennas in the comparison.

A trapped dipole, which is 108 feet long, trapped for 40m, and fed with balance 75 ohm twin feeder, at a height of 10 metres. It is connected to the rig via a 1 to 1 ballun. I have marked this with one ‘beep’ in the recordings.

The second antenna is the Snowdonia Radio Company X80. It is a 5.8 metre tall aluminium vertical with a 9 to 1 un-un at the base. It is fed with 20 metres of RG213 coax. I’ve marked the SRC X80 with two ‘beeps’ in the recordings.

The third antenna is a 3 element Steppir at 11 metres. It is a rotary dipole on 40m and 30m, and a 3 element yagi on 20m to 10m. It is fed with 30 metres of Westflex 103, and there is a 1 to 1 ballun at the feed point to the aerial. I’ve marked this with three ‘beeps’ in the recordings.

I used an ATU once, for the X80 recording on 80m. All other recordings
are without any tuning.

On 80m, you will hear SV2HJQ in Greece. Firstly my trapped dipole, then the X80, then back to my trapped dipole. The dipole gave strength 9, the X80
strength 1.
80m
On 40m, you will hear VE2TC in Canada working some Spanish stations. I have changed the order of the antennas, so they progressively get better. Firstly, you hear the X80 with 2 beeps, then my trapped dipole with 1 beep, and then the Steppir with 3. I then repeat the X80, dipole, and Steppir sequence again.
40m
On 30m, you will hear VP2V/G3PHO in the British Virgin Islands. Firstly, the trapped dipole, then the X80, then the Steppir.
30m
On 20m you will hear HZ1ZH in Saudi Arabia. First the trapped dipole, then the X80, then the Steppir.
20m
Also on 20m, you will hear zl1BD in New Zealand, first the dipole, then the X80, then the Steppir.
20m
On 17m, you will hear KH2/WX8C in Guam. Firstly the dipole, then the X80, and then the Steppir
17m
On 15 m, you will hear V521NAM in Namibia. First, the dipole (no copy), then the X80, finally the Steppir.
15m
On 12m, you’ll hear ST2AR in Sudan. Firstly the trapped dipole, then the X80, and then the Steppir.
This station was worked using the X80 and 10 watts.
12m
On 10m, you will hear LU2NI in Argentina. Firstly the dipole, then the X80, and then the Steppir.
10m