I am using MFJ hamsticks for 20m and 40m bands in dipole configuration(s), i.e. installed in MFJ-347 mount. Here is the first post in this blog on MFJ-2220 and MFJ-2240 dipoes on 38ft/10+m Max-Gain fiberglass pole I use. In a word, 20m dipole works well for me. I use it to make DX as well as stateside contacts. It is not beam antenna, it has inherent loss and not all power makes it to the far field, but it definitely works. It also has some directivity at the height I use it (again 33-38ft, i.e. a little more than 10m). As for 40m dipole at this height, it doesn't work very well, and finally I became curious enough to overcome my laziness and did some modeling in 4nec2 (4nec2 is popular free antenna modeling software -- get your copy).
MODELING 20M HAMSTICK DIPOLE (MFJ-2220)
Now, let's start from the model for 20m. No hamsticks were harmed during my experiments as I did not disassemble any, I also did not take any measurements, electrical or otherwise, apart from physical length. Instead, I cheated: I started from the published model for 40m hamstick-dipole: http://www.qsl.net/kp4md/whf40dp.nec and changed/re-tuned it for 14.250 MHz (I am licensed as general so I do not have access to the band below 14.225 MHz, hence the frequency).
First, let's consider the results for the horizontal configuration. The SWR:
As you see, the inherent loss is high at about 50% and the bandwidth of acceptable (under 10) SWR is quite narrow -- around 100KHz. The bandwith I measured on the actual antenna is much wider:
...which means that my model is not approximating the existing antenna close enough...probably the inductance/stray capacitance/resistance numbers I use for the loads are off. But, the important thing -- it resonates where it should and there is a hope that as a model, it is not completely useless.
Behavior in Far Field:
In far field the antenna exhibits some directivity and low angle of radiation and yes, I noticed and used it while making DX contacts. So, the model is confirming the real antenna's behavior. Good. Now, this is a Far Field pattern at 33ft/10m up in the air. The lower the antenna gets, the more uniform the pattern become. Here is the same Far Field picture at 16 ft / 5m:
The horizontal dipole losing any directivity at the height lower than 1/2 wavelenght is a well known fact; the solution is to change the antenna's orientation to vertical, i.e. like this:
The changing of the orientation is usually not an option for a full- or even half- size dipole, but for MFJ-2220 it is very easy as it is short -- 15 ft / ~ 4.5 m.
Here is Far Field pattern of the same antenna model in vertical configuration at the same height of 20 ft / 6.3 m:
As you see, there are some nulls in vertical plane, plus the take off angle is much lower. It is still unidirectional in horizontal plane, but that's what expected. Judging by the patterns above I think that horizontal polarization of 20m dipole at 10m is better for DX compared to the same antenna in vertical configuration at lower heights, but it is (1) subject to test and (2) I am going to try it when I do portable.
Before going to the 40m hamstick dipole, I have to tell the one finding I stumbled upon while using my 20m dipole: to my surprise, it worked for 40m, too, with help of my LDG IT-100 tuner. Now, the tuner is good for SWR up to 10, which means that the antenna I have also has SWR minimum around 7.175-7.300 MHz (my range for 40m bands). The model doesn't exhibit this behaviour, but the actual antenna does. The model shows a resonance on 10m though:
MODELING 40M HAMSTICK DIPOLE (MFJ-2240)
I used the 40m version of the same antenna in horizontal configuration on the same 33-37ft /10-11m pole and did not like it. There was no directivity, the clouds were obviously happy and warm but that's about it. No good for DX. All this is expected from 40m dipole at this height, and the model confirms it:
It also shows a much better picture at the same height in vertical configuration:
The high loss exhibited here I attribute mostly to poor optimization of the model (it should be somewhat lower than for 20m but not by the order of magnitude as it is here); but the low takeoff angle and nulls in vertical plane are all there. I have to try the antenna mounted vertically, it should work better.
The model of 40m hamstick dipole shows a resonance around 14MHz, this has to be checked with the actual antenna and if so, it can be used on both bands with just one coax run! Advertized as uniband, it is essentially (subject to test) a 40/20m multiband antenna, just like MFJ-2220 is 40m/20m/10m antenna! Here is the SWR graph for 20m:
4NEC2 MODELS
Here are the models I created and used here: download, use, change, let me know if there are any errors etc.
MFJ-2220 horizontal model:
----------copy the text below this line and until end line into your 4NEC2 notepad editor--------------------- CM Emir Shabashvili, KK4MJA CM MFJ-2220 hamstick dipole model tuned for 14.25 MHz CE SY L=4.838526 'Dipole Length SY h= 5 'Mounted on mast SY WL=1.223 'Wip's lenght in m SY LH=0.000031304 'Inductance of the loads in H SY CF=0.00000000000401 'Parasitic capacitance of the inductive loads in F SY freq=14.25 'frequency in Mhz SY r=0.223 'resistance in Ohm GW 1 21 -L/2 0 h -L/2+WL 0 h 0.0012446 'St Steel wip 1 GW 2 43 -L/2+WL 0 h -0.05 0 h 0.0004064 '1st half GW 3 3 -0.05 0 h 0.05 0 h 0.0004064 'center GW 4 43 0.05 0 h L/2-WL 0 h 0.0004064 '2nd half GW 5 21 L/2-WL 0 h L/2 0 h 0.0012446 'St Steel wip 2 GE 1 LD 5 1 0 0 1390000 '1st steel wip LD 5 2 0 0 58000000 '1st half LD 5 3 0 0 58000000 'center LD 5 4 0 0 58000000 '2nd half LD 5 5 0 0 1390000 '2nd steel wip LD 0 2 2 42 r LH CF 'load 1 LD 0 4 2 42 r LH CF 'load 2 GN 2 0 0 0 4 0.003 EK EX 0 3 2 0 1 0 0 FR 0 0 0 0 freq 0 EN ------------------------------------------end of model -------------------------------------------------------
MFJ-2220 vertical model:
----------copy the text below this line and until end line into your 4NEC2 notepad editor--------------------- CM Emir Shabashvili, KK4MJA CM MFJ-2220 hamstick dipole model tuned for 14.200 MHz CM Vertical orientation CE SY L=4.838526 'Dipole Length SY h=6.3 'Mounted on mast SY WL=1.223 'Wip's lenght in m SY LH=0.000031304 'Inductance of the loads in H (0.000031304 H) SY CF=0.00000000000401 'Parasitic capacitance of the inductive loads in F (4.01e-12) SY freq=14.25 'frequency in Mhz SY r=0.223 'resistance in Ohm GW 1 21 0 0 h+L/2 0 0 h+L/2-WL 0.0012446 'St Steel wip 1 GW 2 43 0 0 h+L/2-WL 0 0 h+0.05 0.0004064 '1st half GW 3 3 0 0 h+0.05 0 0 h-0.05 0.0004064 'center GW 4 43 0 0 h-0.05 0 0 h-L/2+WL 0.0004064 '2nd half GW 5 21 0 0 h-L/2+WL 0 0 h-L/2 0.0012446 'St Steel wip 2 GE 1 LD 5 1 0 0 1390000 '1st steel wip LD 5 2 0 0 58000000 '1st half LD 5 3 0 0 58000000 'center LD 5 4 0 0 58000000 '2nd half LD 5 5 0 0 1390000 '2nd steel wip LD 0 2 2 42 r LH CF 'load 1 LD 0 4 2 42 r LH CF 'load 2 GN 2 0 0 0 4 0.003 EK EX 0 3 2 0 1 0 0 FR 0 0 0 0 freq 0 EN ------------------------------------------end of model ---------------------------------------------------------
MFJ-2240 horizontal model:
----------copy the text below this line and until end line into your 4NEC2 notepad editor----------------------- CM Emir Shabashvili, KK4MJA CM MFJ-2240 hamstick dipole model tuned for 7.25 MHz CE SY L=4.8061 'Dipole Length, m (4.8385) SY h= 10 'Mounted on mast, in m SY WL=1.2082 'Wip's lenght, m SY LH=0.0000782 'Inductance of the loads in H SY CF=0.00000000000631 'Parasitic capacitance of the inductive loads in F SY freq=7.25 'frequency in MHz SY r=0.42 'Load's resistance (Ohm) GW 1 21 -L/2 0 h -L/2+WL 0 h 0.0012446 'St Steel wip 1 GW 2 23 -L/2+WL 0 h -0.1 0 h 0.0004064 '1st half GW 3 3 -0.1 0 h 0.1 0 h 0.0004064 'center GW 4 23 0.1 0 h L/2-WL 0 h 0.0004064 '2nd half GW 5 21 L/2-WL 0 h L/2 0 h 0.0012446 'St Steel wip 2 GE 1 LD 5 1 0 0 1390000 '1st steel wip LD 5 2 0 0 58000000 '1st half LD 5 3 0 0 58000000 'center LD 5 4 0 0 58000000 '2nd half LD 5 5 0 0 1390000 '2nd steel wip LD 0 2 2 22 r LH CF 'load 1 LD 0 4 2 22 r LH CF 'load 2 GN 2 0 0 0 4 0.003 EK EX 0 3 2 0 1 0 0 FR 0 0 0 0 freq 0 EN ------------------------------------------end of model ---------------------------------------------------------
MFJ-2240 vertical model:
----------copy the text below this line and until end line into your 4NEC2 notepad editor----------------------- CM Emir Shabashvili, KK4MJA CM MFJ-2240 hamstick dipole model tuned for 7.25 MHz CM Vertical orientation CE SY L=4.8061 'Dipole Length, m (4.8385) SY h=10 'Mounted on mast, in m SY WL=1.2082 'Wip's lenght, m SY LH=0.0000782 'Inductance of the loads in H SY CF=0.00000000000631 'Parasitic capacitance of the inductive loads in F SY freq=7.25 'frequency in MHz SY r=0.88 'Load's resistance (Ohm) GW 1 21 0 0 h+L/2 0 0 h+L/2-WL 0.0012446 'St Steel wip 1 GW 2 23 0 0 h+L/2-WL 0 0 h+0.1 0.0004064 '1st half GW 3 3 0 0 h+0.1 0 0 h-0.1 0.0004064 'center GW 4 23 0 0 h-0.1 0 0 h-L/2+WL 0.0004064 '2nd half GW 5 21 0 0 h-L/2+WL 0 0 h-L/2 0.0012446 'St Steel wip 2 GE 1 LD 5 1 0 0 1390000 '1st steel wip LD 5 2 0 0 58000000 '1st half LD 5 3 0 0 58000000 'center LD 5 4 0 0 58000000 '2nd half LD 5 5 0 0 1390000 '2nd steel wip LD 0 2 2 22 r LH CF 'load 1 LD 0 4 2 22 r LH CF 'load 2 GN 2 0 0 0 4 0.003 EK EX 0 3 2 0 1 0 0 FR 0 0 0 0 freq 0 EN ------------------------------------------end of model -----------------------------------------------------------
Hi; I was looking at my MFJ Octopus 4 band horizontal. It uses two MFJ Ham Sticks per band, mounted in opposing positions around an 8 sided center hub. Mine is equipped with 1., 15, 20, and 40 meters. Each pair of HamSticks were tuned separately for the lowest SWR, then when all were combined, the SWR was acceptable on all of the bands listed. I was considering making an antenna similar in electrical design and using the MFJ Ham Stick antennas mounted in a straight line, more or less a "beam" shaped set up as opposed to the Octagonal shape of the Octopus. I know nothing about the modeling software or how to use it. So far, no one I have inquired of has any idea of a working distance between the Ham Sticks as mounted as elements along each side of a boom for the shape of the beam. I am considering using a similar wiring scheme, so that the center connector of the Ham Sticks on one side, with the shield of all the Ham Sticks connected on the opposite side. I had envisioned this to look like a 4 element beam, but I have no knowledge of how one would try to model it. Is there any way you might assist in that, and whether this configuration if properly constructed would work well enough to put forth the effort to build it. I feel it would work, but have no idea how it compares to a long wire for the same bands. 73 W4WLW
Hello Walt, making a beam out of shortened loaded dipoles is not a very good idea in my opinion. It is better to do the actual beam, for instance moxon (a two-element yagi) or something like it. That said, the monoband beam out of hamstickts had been attempted before, see for instance here: http://www.hamuniverse.com/20minibeam.html
It works, but how well is not known. My guess is that the improvement compared to the hamstick dipole is marginal, if any.
I have a modified 40-meter dipole in the attic. One element is a 1/4-wavelength wire and the other element is a 40-m hamstick. There is 1:1 balun connecting the elements. I wonder how that would look on a model? Dave WD9DWT
Hi Dave, sorry I was thinking about restoring my modelling setup after I read your comment but I don't have time to do it right now (work, work and more work), but I have an advice based on my experience: my attic is very small (6.2mx7.5m or 20x24 ft) and very hot most of the time, so I had hard time placing anything HF-meaningful there and turning it for a resonance. Instead, I put a choke at the antenna end and run coax into the tuner at the radio end. The antenna is a moxon cut for 17m and tuned to resonance on 17m (sort of). It works with the tuner on 20,15,12,10 and 6m as a dipole. It works as a beam on 17m.
Cheers!
Emir K4MJA