Antennas

I have experimented with a number different vertical / directional and wire antennas; below are my summarisations of these.
 
Spiderbeam 20/17/15/12/10m HF directional beam


spiderimage






 
 
 
 



I consider this antenna to be an excellent performer and great value for money too. The one shown in the pictures below was constructed and erected over a weekend. There are nineteen wires to cut - these form the driven, reflector and director elements for each band - measure twice and cut once is good advice as the length is critical.
 
The antenna comprises of 4 equal length fireglass spreaders connected at a central hub where the supporting mast is attached. Looking down from above the shape represents an equal sided cross. It is quite a large antenna with a 33 foot wingspan (1/2 wave on 20M) - it is lightweight however weighing approx 7 kg, so ideal for portable or permanent installation on a lightweight tower (as seen in photograph).
 
The common feedpoint for the driven elements can be seen in the photos just above the spreader, all driven elements terminate in a box which is attached to the supporting mast. The driven elements comprise of two equal length wires (di-pole elements) which spread out on two of the opposing fireglass arms and are held in place on the booms with velcro - this allows enough spacing between them to avoid interaction.
  
Individually the reflector and director elements (director elements not used on 12/17m in this example but could be added if wished) are attached to the boom sections and stretched out towards the element ends.
   
There are a number of different configurations available, however the one pictured has:
 
3 elements on 20m
2 elements on 17m
3 elements on 15m
2 elements on 12m
4 elements on 10m
 
Performance should be better than a typical triband yagi as the elements are full size with no traps and they optimally spaced for each band.
  
 This antenna has been used primarily on 20/17/15m as conditions on the higher bands are not good currently (May 2007). I see good front to side/back ratios on all bands tested so far and can hear beacons which were previously inaudiable on a ladder line fed doublet at the same height - 30 feet. 
  
When I operated from this location again in May 2008 I noticed that the antenna had turned on the mast. This caused some tension on the driven element wires where they connect into the balun box - fortunately there was no damage. Once I had taken the antenna down it became apparent that I had not done a very good job of tightening the U clamps which hold the antenna to the mast. This was done correctly before the antenna was put back on the mast.
I did notice that the fibreglass spreaders had lost their black colour where they are exposed to the sun - otherwise the antenna was in good order 12 months after the installation.
 
During several hours of operating; I worked 5U5U in Niger on 17m which is a new one for me. I also worked lots of European stations which enabled me to re-evaluate performance and front to back ratios etc - all appear to be working to manufacturer's spec. Other contacts included: OE2008V, OE2008L, OZ/DL9ABF on EU125, GB1SRI on EU122, EA7DLD - also using a spiderbeam, EA3IM and CT1HZU.
 
 
 
spider1
 
 
  
Direction of radiation is forward from the face on which the feedbox is attached - to the right in this picture 
  
 
 
spider2
 
 
 
This photo shows the size of the antenna compared to the small scaffolding tower used during the construction.
  
 
More information can be found here: http://www.spiderbeam.net
  
 
  
Radioworks Carolina Windom



cw80

  







I have used the following models with good results:
  
CW-80 special  66 feet length and 10 foot vertical radiator


Works well on all bands from 80m to 10m, a few db down on a full sized 80m antenna, but signals are generally very strong on this band anyway. I found this antenna to be outstanding on 12/10m. I believe this is because the radiation pattern is more or less omnidirectional and the take off angle is low. I believe the vertical radiator helps here, it's approximately 1/4 wavelength long on these bands.
I noted that it surprisingly produced stronger signals on 40m than a full sized CW-80. I retired this antenna because I moved house and found room for the full sized 80m antenna.
  
CW-80 / CW-80LP Approx 132 feet long with a 22 foot vertical radiator


An 'S' point or two improvement over the CW-80 special on 80m as expected, but a few 'S' points down on the CW-80 special on 40m.
Other side by side comparisons with the CW-80 showed improvements on 20/17/15m - often an 'S' point more. However on 12/10m the CW-80 special had a distinct advantage. When switching between the two antennas a station on the CW-80 special at S5 would disappear on the CW-80. There was much less background noise on the CW-80 which suggested that it simply did not hear as well on the higher bands.
I prefer the LP (low profile) version of this antenna as the matching sections are much smaller physically, hence is easier to support and less visible.
  
CW-40 performance plus / LP 66 feet long with 18 foot vertical radiator


I have not been able to make any side by side comparisons with the CW-80/CW-80 special. I have used both high power (large matching devices) and low profile models and can confirm they are equal in performance. The LP derivative has a 600 watt power handling which is more than enough for the UK limit of 400 watts. I did use this antenna until recently, it was supported on a fibreglass pole at a minumum of 20 feet with the option of telescoping upto 40 feet high. I didn't see much difference in performance between 20' and 40' , I put this down to the fact that the vertical radiator produces low angle radiation even at low antenna support heights.
  
 
 
  G3TPW Cobwebb 20/17/15/12/10m HF omnidirectional



   cobwebb_g3pw 
 

The Cobwebb comprises of 5 full size resonant dipoles, the elements of which are folded and tapped to provide a 50 ohm feed impedance. The elements are folded into a square shape which produces an omni directional radiation pattern.
This is an ideal antenna where space is at a premium, or where the is only one antenna support available. It measures approx 8 feet per side and is easy for one person to handle.
I have used Cobwebbs at a number of different locations and find them to perform very well. 
  
  
Performance comparisons between the Cobwebb and my CW-80 Special can be found here:
  
  
Quote:
 
'I had been considering one of these antennas for a number of years. I recently found a second hand one at a good price and decided to purchase it. I am very pleased that I did! The antenna is very sturdy, the one I bought was 5-6 years old and was still in A1 condition. My antenna was pre-tuned to the SSB portions of the 20-10m bands, so no tuning required. It is mounted on a push-up mast at about 15 feet with houses nearby. I use my Carolina windom as a reference antenna - I prefer this cobwebb for a number of reasons.
Bandswitching is simple and because the antenna is resonant on all bands, no ATU is required. It only requires a single support, unlike a traditional dipole/windom. It is omni-directional, no nulls. Most of all, it works very well! Switching between my two antennas, there are more times when the cobwebb produces a stronger signal than the windom - on all bands (possibly with the exception of 10m). I listened to the worldwide beacons to make my evaluations. I have just finished working a Japanese station on 12m, and was then called by 4 more! This has never ever happened to me before - infact I have never worked japan on 12m (maybe due to the Windom's null in that direction?). I am looking forward to guying my mast and pushing the Cobwebb clear of my house roof. The Cobwebb paperwork suggests a 3-6 db improvement with a doubling of height - can't wait!! '
  
 
There is more design and technical information on the antenna designer's website:
  
  
  
The cobwebb is easy to home construct too, there are many sites dedicated to this approach. I have built my own 20m and 17m cobwebb which is very light weight and cheap to construct. The components used were from a moxon antenna supplied by Sandpiper antennas.
Performance at 20 feet is very good; with an improvement over my reference 80m windom 75% of the time - by between 1 and 2 's' points. I believe this improvement is partly due the omnidirectional properties of the cobwebb - this helps to fill in the nulls of the windom's radiation pattern. I expect the cobwebb would show even more improvement if it was located at the same height as the windom.
  
  
  
cobwebb2017
   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Home built 20m and 17m cobwebb

 

 
 
Giovannini D2T



d2t











 
 
 
 
 


The D2T resembles a traditional 2 element HF beam antenna, it has a 6 foot boom and two 18 foot long elements - this being approximately the same as a 12m mono bander.
 
 
 
http://www.antenna.it/
The D2T is a broadband antenna which covers between 1.5 - 200Mhz with a feedpoint impedance of 50 ohms. The broadband capabilities are achieved by incorporating a terminating resistor with an RF transformer. It is fair to assume that this configuration will result in some loss of radiation efficiency when compared to a resonant dipole, this is the unfortunate trade off that must be accepted with a broadband type of antenna.
The D2T shares some of the T2FD's theory of operation, which is also known as the tilted folded
dipole. There is very useful theoretical information at:
  

This modelling info confirms that there are losses in the terminating resistor, the loss
increasing at lower frequencies of operation - this being partly due to the antenna's small size in relation to the wavelength on lower bands.
   
See the graph below which shows efficiency increase with frequency - the 'y' axis represents % efficiency:
 
d2tloss
 
 
 
 
 
 
 
 
 
 
 
 
 
I am most interested in 20m and up, so the fact that this antenna will receive and transmit to some extent on 160/80/40/30 is a bonus. It is reported as being very suitable for short wave listening as it is quiet on receive and can be rotated to null interference.
  
The D2T behaves more or less like a dipole on 20m with a bi-directional pattern, on 17m it starts to show forward directivity with some gain, this continues to increase one goes up in frequency, on 10m its pattern is similar to that of a beam antenna with a 6db gain.
It would be unfair to compare the D2T's performance with a monoband HF beam on any band other than 10m, it simply will not equal a monobander's performance. However I'm not aware of another 'directional' antenna that is so compact, has useable directivity and will provide a 50 ohm load throughout this frequency range.
  
I have experience with Cushcraft MA5B and Butternut HF5B minibeams. These are both good 5 band antennas, however the tuning to achieve resonance can be fiddly with the Butternut, in contrast the Cushcraft is straightforward. They are both mechanically more complex than the D2T hence assembly takes longer. It is likely that an ATU will be necessary to cover the full band(s). 20/15/10m each are configured with driven and parasitic elements, 17/12m are dipole elements. The D2T in comparison is directional on 17-10 with no bandwidth restrictions. I have not made any side by side comparisons between the MA5B / HF5B / D2T but whilst acknowledging that they are all compromise antennas, each has it's own advantages.
  
 
  
 
Butternut HF5B
 
butternut hf5
 
 
This antenna has a wingspan of approximately 12 feet, the vertical spreaders are 6 feet long and a boom is 6 feet long. It covers 20/17/15/12/10m. On 20/15/10m it operates as a 2 element beam and on 17/12m a single element dipole.
  
It weights less than 10 Kg and can be mounted on a lightweight mast and turned by a lightweight rotator. The manufacturer recommends a mimimum height on 30 feet - this will help the antenna to achieve the 20db front to back and 30db front to side ratios.
  
The radiating elements comprise of the aluminium horizontal portion, the aluminium vertical spreader and the wire elements which spread from near the centre to the tip of the spreaders. This combination of linear and end loading result is approximately 44 feet of conductive material making up each of the driven and reflector elements. Note that linear and end loading do not result in a like for like physical length and electrical length however. Such a configuration could be considered as being more efficient than the use of coils solely to achieve similar results. The use of capacitors and and a loading coil at the centre of the elements serves to bring the feedpoint impedance to 50 ohms.
  
In order to tune the antenna it is necessary to remove the reflector element and mount the driven element so that the spreaders are parallel to the ground. Using an SWR bridge start with 20m, make the adjustments as specified in the instructions. The instructions explain the tuning process in detail: http://www.bencher.com/pdfs/00159IZV.pdf
  
2:1 VSWR bandwidths are achievable on 1.5 Mhz of the 10m band, throughout 12/15/17m and 200Khz on 20m. These are comparatively good bandwidths for a mini beam. The Cushcraft MA5B in comparison achieves approx 665 Khz on 10m and approx 90Khz of 2:1 VSWR bandwidth on 20m.
  
  
 
20m vertical delta loop Antenna


deltaloop2


Current delta loop using a spiderbeam 12m fibreglass mast (extended to approx 10m as no advantage going higher) which is significantly more robust than the orginal DK9SQ offering. The radiating element and balun are original DK9SQ.


 
DK9SQ can take credit for the first 20m vertical loop antenna system which I tried. This antenns is marketed as a 40-10m antenna. It's designed to be used in conjunction with a 10m fibreglass mast which is also marketed by dk9sq.
The antenna kit comprises of a balun assembly, twinlead feedline, approximately 20m of insulated copper multistrand wire and two equal length fireglass spreaders.
 
Firstly the balun assembly should be slid down the mast from the top of the vertical mast, the spreaders can then be inserted into their mouting positions. Visually the supporting mast and spreaders are positioned in the shape of a cross.
The feedline is run along the length of one of the spreaders from the balun housing and the antenna wire is run around the cross shape. There is a circular electrical wire connector which fits over the top of the vertical mast to secure the wire.
Please note that this antenna is fed at one corner of the diamond shape loop - this will provide low angle radiation vertical radiation which is good for DX. 
  
By connecting 50 ohm coaxial cable using a standard PL259 type plug to the antenna you are almost ready for operation. The antenna may be resonant on some bands, but for multiband use I recommend an ATU.
  
The radiation pattern of a full wavelength vertical delta loop fed 1/4 from the apex when used on its design frequency - 20m in this case is oval in shape. The radiation pattern is broad and I could not detect any difference in signals when I rotated the antenna through 90 degrees on 20m and 17m - modelling does suggest a 3 db variation. There is little or no gain on these frequencies, but the angle of radiation is low at between 16 -17 degrees.  A dipole would need to be approx .9 wavelengths high to achieve the same low angle of radiation - this equates to 18 metres or 60 feet. For optimum performance the lowest part of the delta should be at approximately 10-13 feet from the ground. Depending upon the width of the delta the top would be at approx 33 feet, or 10m.
   
The pattern was less uniform on 15/12/10 and performance analysis suggests an increasing radiation take off angle on these bands.
   
For 40m operation there is a barrel connector parallel to the antenna wire which should be unplugged, this turns the antenna into an electrical half wave length on this band. There is a significant improvement in 40m signal levels when opening the circuit.
I have not yet tested 30m operation with open or closed circuit.
  
I posted a review on eham.net in 2002 when I first experimented with this antenna. Since then I have constructed my own vertical loop with the same dimensions and feedpoint, it continues to provide excellent results with the apex at approximately 25 feet.
  
  
I purchased this antenna for portable use. I was looking for an antenna that could be used on all the higher HF bands, i.e 20m and up. It had to be ground independant, easy to erect and compact. This antenna fits the bill, it's basically a 40m 1/2 wave of insulated flexweave type wire in the shape of a diamond. For 40m operation the loop should be open circuit, but for all other bands the loop is closed. It acts as a full wave on 20m, approx 2 full waves on 10m etc - it does require a tuner.In my testing I have found that it does not show any noticeable directivity, hence no need to rotate the antenna.
I had my antenna temporarily mounted at ground level in a built up area, so it could not see sky at low angles of radiation. The results were outstanding, I was able to make comparisons with my permanent Carolina windom 80 special mounted at approx 20 feet. The loop provided stronger signals on 10m 75% of the time, both European and DX, on 12m the loop was better 60% of the time, on 15m 50%, 17m 25% and 20m equal. These are not scientific calculations, but based upon several weeks of operation.
  
  
Force 12 Sigma 5


sigma5
The Force 12 Sigma 5 is a reduced size vertical antenna which covers the 20/17/15/12/10m bands. The sigma 5 is fed at the centre with 50 ohm coax and has a hairpin match and loading coils to achieve resonance on each band. There is a separate control switch which enables the user to remotely change bands, this connects to the centre via a multicore cable.
The antenna is approximately 10 feet tall and is recommended to be installed at ground level. If it is elevated, the SWR increases as does the radiation angle.


There are many good anecdotal reviews on eham.net which suggest surprisingly good performance for such a small antenna.
 

I have made some tests between my 80m windom at 35 feet with the sigma 5 at ground level the results have been very encouraging. The only bands which were open were 20m and 17m, and only European stations were being heard. These could hardly be described as DX stations, and the radiation angle of these signals would be higher than optimum for a vertical antenna. Infact they would be more suited to a lower horizontal antenna, such as the 80m windom reference antenna. Despite this test being quite 'unfair' the results were very encouraging. Signals on the Sigma 5 were generally 1-2 's' points lower, which I think is a very commendable performance considering the size of this antenna and the nature of the test.
  

 

Shortly after my initial tests I put the antenna back up in the same position to test its DX capabilities. I can hear US and Canada signals on 20m most days, so was relying upon conditions being reasonable.

Fortunately there were a number of US stations on 20m; which enabled me to make some comparisons between antennas.
  
Firstly I generally hear up to S5 of noise on 20m with the windom, the noise floor was marginally higher on the sigma 5.
I listened to 3-4 stations in the US and signal levels were more or less equal between the two antennas. Some signals were higher on the sigma 5 and others on the windom - there was no clear winner. I would say that there was slightly less fading (QSB) on the sigma 5.
  
Force 12 claim more than 90% efficiency. I assume this figure is for the 20m band as the antenna is electrically smallest here and least efficient. With such encouraging results on 20m I would expect even greater results on 17m – 10m.
  
It should be considered that my windom at 35 feet is approx ½ wavelength high on 20m, hence the vertical will produce a much lower angle of radiation. A dipole for 10m at 35 feet is approx 1 wavelength high and therefore may be more comparable with the vertical.
  
I believe this antenna is an excellent choice for portable operations as it breaks down into 2 foot sections. It is also perfect for situations where a wire antenna or yagi etc cannot be used due to lack of space or planning restrictions. I have been pleasantly surprised by the performance of the sigma 5 and would have no hesitations recommending it.
  
 
Diamond CP-6

The CP-6 is compact, lightweight and easy to assemble HF vertical which covers 80/40/20/15/10 and 6 metres.
 The overall length is approximately 4.6 metres, the longest radial being 1.8 metres long. The radials can be arranged in 360 degrees as shown below, or 180 degrees to allow mounting close to a wall / side of tower.
  
This antenna is a trapped 1/4 wave design with a 1/4 wave radial for each band - which can be adjusted for resonance. The operating bandwidths are quite small on 80/40/20m as would be expected with a reduced size antenna of this type. Lets not forget that a 1/4 wave on 80m is approx 66 feet in length, compare that with 15 feet length of the CP-6. You would be excused for thinking that this antenna will not work very well on 80m due to the amount of loading to achieve resonance. In theory it may not appear to be very efficient - however it does work very well.
To find out how it compares with other vertical antennas I would strongly recommend that you obtain a copy of: 
  
"HF Vertical Performance, Test Methods & Results" by Ward Silver, N0AX and Steve Morris, K7LXC and published by Champion Radio Products.
I think you will be surprised how well the CP-6 does compared to larger more expensive vertical antennas.
  
  
cp6_vert
 

 

 

 




  
 









Par end-fed 20m

par_endfed
  
 
 
 
 
 
 
 
 
 
 
 
 
 
Par electronics market a number of mono band end fed half wave antennas and a multiband qrp end fed antenna.
 
 
Performance should be comparable with a centre fed 1/2 wave dipole, the only difference being that the end fed is fed with 50ohm coax at the end rather than the centre.
The build quality is good and the antenna is suitable for temporary or permanent installation. The 20m version is lightweight and would lend itself well to portable operation - something I intend doing too.
 
I have performed tests with the antenna oriented horizontally and vertically. Using my 80m windom as reference antenna results have been interesting. The windom feedpoint is at approx 35 feet, due to a lack of suitable supports the end fed was mounted at 20 feet and oriented horizontally. The windom was stronger in all cases, by at least 2 's' points. Hardly a fair test and I would expect the par end fed to be at least comparable with the windom with signals running parallel to the antenna wire. The end fed presented an SWR or 1:1.5 or less across the 20m band - the windom does not achive this.
 
The second test involved orienting the end fed vertically. This was achieved using a Spiderbeam 40 foot fibreglass mast with the end-fed strung up the length. The feedpoint therefore being at approx 7 feet above the ground. I tuned around the 20m band switching between the windom and the end fed trying to ascertain which was best - the results were far more encouraging.
There was a moderate amount of activity on 20m - this was at 20:00 BST June 2008.
 
60% of local European signals were stronger on the vertical. This was quite surprising as I would have thought that high angle radiation provided by the windom would be better for 'local' contacts. I can only attribute this to the fact that the windom has some deep nulls in certain directions. The stronger signals which were received on the vertical were mainly originated on horizontally polarised antennas - yagis predominantly. This eliminates transmitted polarisation being the contributing factor.
 
There were a couple of quite 'interesting' stations on 20m; one in Morocco which I managed to work on the 2nd call and one in Jordan which was at 's' 5 and a big pile up - I didn't waste any time with that one. These two stations were stronger on the end fed by on average 2 's' points.
 
Second evaluation 22/08/08

Using my 40 foot fibreglass mast with 15 feet of lightweight fishing pole pushed into the top, I put the EF-20 back into service. The top was at approx 55 feet and the feedpoint at 22 feet. This was only a temporary installtion as the mast was only guyed half way up the mast and I would not be confident leaving it overnight.
 
I listened around 20m for a while to asses conditions and to find stations who were putting out CQ calls.
I made contact with AM5KB, IW3SQY, IK4WKU, OK1GHZ, HA4FF and W3RFK (IC7800, 4 element Steppir at 20+ metres and 1 KW!) My signal was comparable with other stations who were recieving reports and in some cases the strength of my signal was reported as being 5/9+.
 
When I switched between the EF-20 and my 80m windom reference antenna, W3RFK's signal dropped the most by approximately 3 's' points. The other stations were equal to or weaker on the windom - none were stronger. 
 
This cost effective, lightweight and simple antenna is becoming one of my favourites!

 
 Hexbeam HXP-20

 
hexbeam
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 









Initial testing with the hexbeam shows 2-4 's' units increase compared to the 80 windom reference antenna. I have broken a couple of pile ups and been given 5/9 and 5/9+ reports - the pileups were at 's' 5 on the windom and 's' 9 on the hexbeam.
 
 
hex_bag
 
 
 Very well designed Hexbeam bag for carrying the HXP components. There is an individual section for each band (optional extras) and all other hardware necessary to construct the Hexbeam. The only other components required are a lightweight mast, coax and transceiver.
 
Assembly is straightforward. There are a selection of colour coded fibreglass sections which make up the necessary structure for the band in question. My first attempt at assembling the antenna took approximately 30 minutes. With practice it should be possible to complete in half that time.
 
Once the supporting lines and elements are in place, the antenna is perfectly balanced and is not noticeably affected by the wind. My supporting mast is a lightweight 40 foot fibreglass telescopic model which is designed for supporting lightweight antennas. I attached 3 guys near the top of the mast so that the mast could be rotated whilst they remain in place.
 
I consider this to be the ultimate fibreglass / wire compact beam antenna. 
 
 
Cushcraft MA5B

 
ma5b
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   
The MA5B is a 5 band beam antenna with 2 active elements on 20/15/10m and thus provides directivity on these bands. The middle element is a trapped dipole for 17/12m, there are no parasitic elements involved therefore is bi-directional.
 
Construction is typical of the quality I expect from Cushcraft. All the holes line up perfectly, all hardware is stainless steel, the boom / elements are good quality aluminium and the traps appear to be well constructed.
 
Assembly takes a couple of hours and I recommend using supports to rest the antenna upon as the capacity hat elements prevent the antenna from being assembled flat on the ground. I set the antenna up as per instructions and found the SWR to be as specified - no need to fine tune.
The antenna weighs approximately 12kg which means that a medium duty rotator and mast is sufficient. I used an ex military Clarke PU12 mast which was adequate - I would however recommend the use of guy ropes if the mast is to be fully extended.
 
At the time of testing I did not have any reference antenna to make comparisons with. However I was impressed with the directivity on 20/15/10 - the front to back ratio seemed higher on 15/10m probably because the antenna was higher in terms of wavelength on these bands. It was also possible to peak / null signals on 17/12m when the antenna was rotated.

A good choice where space is at a premium. Also due to relatively light weight may be possible to place higher than full size (heavier) 5 band alternatives.

  
  

1/2 wave full size centre fed 20m vertical
  
  
  
20m_vert
 
vert_balun
 
 
 
 
 
 
 
 
 
 
 
 
 
 
SGC 239 Autotuner
 
This is a very versatile tuner capable of handling up to 200 watts PEP from 1.8-30 Mhz (it does work on 6m to). It is a very wide range tuner and is able to match my Cobwebb antenna on 10Mhz, 7Mhz and 3.5Mhz - the antenna is inefficient on those bands but I can still hear a lot of stations.
I have fitted my tuner into a waterproof box so that it can be used outside. I have also installed an internal 12 volt power source for portability and convenience.
 
 
sgc239
 
 
My next project a ladder line fed vertical for bands between 10Mhz and 30Mhz as detailed on the Cebik website. Results to follow.
 
 
 
 

 


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