Does the MFJ-1984MP need a tuner? I put it to the test.

Nice job.

Just remember the physics drives this and is easy to understand: the half wave is like a jump-rope where the displacement (that is the current) is max in the center and goes to zero at the ends. It is half a sine wave. So when you feed it from the end (a 'boundary condition'), theoretically the current is zero there and the impedance is very high. Max current gives min voltage; min current gives max voltage--both sine waves, and out of phase. High voltages at the ends. A good balun/transformer will handle it.

Before good ferrite based toroid transformer cores, doing an end fed half wave was a lossy proposition and generated a lot of heat. If you are running high power, I would always do a burn-in test to see how high the voltage gets and heats up the core. NEVER operate QRO IF the core is HOT. And remember, heat is a tracer of inefficiency.

Because the feedpoint is unbalanced, additional choking (to stop radiating coax) is a good idea. although may or may not be needed. I used them thar chokes religiously.

73
Chip W1YW

 

I’ve been using a Chameleon Emcomm 2 which is an end fed without external tuner, it has a 5:1 matchbox with an 80 feet wire and a 60 feet counter poise running to the opposite way from where the radiating wire is going. No need for an external tuner from 80 to 6 meter. Got 1.5:1 SWR in 40m and 20m 1:1 on 17m and 15m. And 2to 1 on 10 and 6m

 

Hi there. Well that does seem like a good test out of that antenna. I also use a EFHW with a H/Brew 49:1 unun. My wire is a 130 ft sloper. It is my GP antenna for HF and gets me out from Prince Edward Island in the West to Moscow in the N. East. From Norway down to Italy in Europe. So I am very happy with it. I can't wait for the conditions to improve and enable me to cross the pond into the states. 73 de John - G0WXU. in West Yorkshire.

 

Thanks for the testing, great video. After seeing the performance i ordered the MFj1984mp which should get here tomorrow. We just moved into an HOA so my current antennas(homebrew windom for HF) are in the attic. Attic antennas are fun to install said no one, so I'm planning on stringing out the MFJ1984 wire on top of the roof from one side of the house to the other side along the peaks to get it as stealth as possible. I plan to bring up the coax through the gutter downspout to the roof line to connect to the box. i'm also going to bring the counterpoise down through the downspout and bury it in the ground. Should I terminate the counterpoise wire to a ground rod? I'm planning on putting a ground rod from the radio regardless as i haven't done this yet. Thanks again for the video as I would have gone a different direction like a homebrew flagpole antenna which i may still do but the process is longer because have to wait for approval from HOA on flagpole. 73 de fernando

 

Yes I would attach that counterpoise to an earth ground if you can. Make sure the vents face down and you will need to seal that box if its going to be exposed to rain. Just leave the vents open so the toroid can vent the heat.

 

Nice video, as all I have seen from you have been.

First comment is that many confuse all endfed antennas as being one animal. But there are two popular types...
1)The "random wire" antenna cut to an intended non-resonant length and typically fed with a 9:1 unun. This, as WB4JHS suggested is best used with the feedpoint elevated as high as possible. This is because the maximum current (thus radiation) is at the feedpoint. Palomar engineers website has nice diagrams illustrating this.
2) A true EFHW (end fed half wave wire) which is resonant and voltage fed at the end (very high impedance) versus current fed at the center like a half wave dipole. That said the point of maximum current (radiation) occurs at a point elsewhere along the wire. In the case of the 66" EFHW, theory would say the high current point for 40 meters would be close to 33", on 20 meters there would be multiple high current points every 16.5", and so on as we increase even harmonic bands. I've never seen the EFHW modeled, but like a Zepp it must have increasing gain as frequency and thus current points multiply. The feedpoint being elevated makes no difference as it is a high voltage rather than high current point- But care must therefore be taken for accidental contact!!!

I have experimented and successfully used a homebrew 80 meter EFHW, and it also works quite handy as a 160 meter inverted L when I bypass the 49:1 transformer .The transformer is mounted 6' off the ground, wire runs vertical for 50 feet and horizontal for 82'. In my experience with this antenna I have found that a common mode choke at the radio cuts noise by 6 to 12 dB- even though I am out in the sticks in VT. (By the way for some odd reason it is a killer on 17- shouldn't be but is)

One thing that may help the 10 meter issue in the sloper configuration... try putting a small coil (6 turns) a short way up the wire from the transformer. It will not affect the lower bands, but will lower resonance on high bands- have a feeling if you scanned swr up higher in frequency, you would have found it drop.

Gee, I hope I sounded really smart in all that- I'm not!!! There are some great videos on youtube by Steve Ellington, who I consider to be the expert on EFHW's- very sharp guy with a lot of experience. I am simply echoing his work.

Thanks for the videos, keep up the good work and hope to meet you on the air!

Vy 73, Randy N1SP

 

Excellent information Randy, thank you! I am probably going to get choke to put up near the radio to help with some noise and CMC.

 

most of us cannot our get our wires a wavelength above ground. My wire apex is at 20 feet which is the height limit in my community. I regularly work all over the world running 5 watts. My first contact in last weeks wpx was bosnia. You use what you have and if it works great

 

Many years ago there was a sensitivity analysis done to show at what point a dipole has higher gain at lower elevation angles--20 degrees or less-- compared to a quarter wave vertical monopole. That is what gives you the best DX prospects at HF.

Not surprisingly...the transition happens at 1/4 wave high or so. On 20m that is 4m high--roughly 13 feet. So even a low height dipole can have better low angle gain than such a vertical. The ADVANTAGE of a vertical is that it is omni azimuthal and 'sees' in all directions. The dipole sticks you with a figure 8 pattern.

Additionally, verticals have much less HIGH ANGLE coverage, which is where most of the QRN sky noise comes from, Thus they are 'quieter'.

 

Using a Myantennas 7510-2k EFHW. The feed is at 4 ft , the vertical portion runs to 40 ft high. The remaining 100 ft is horizontal at 40 ft.

The antenna works fine on all bands, the Icom 7300 tunes most anywhere. It also works well in most cases on WARC bands. I use it often on 60m as well. The Icom tunes on 60m as long as l do not use the ground terminal on the feed box.

I am perfectly happy with the installation, operation and especially, the performance of this very versatile antenna.

 

Huh? they may be quieter by reducing high angle incoming signals, but isn't most man-made noise vertically polarized?
I've never (in real life) used a vertical that was any quieter than a properly installed dipole. Usually the vertical was noisier...

'splain than...

 

I can't account for your experience, nor shall try. The point is that the solid angle coverage of the vertical nulls at high angles. Right now, with the poor SFI , the SKY NOISE is quite pronounced and has significant contribution from high elevation angles. That sky noise is produced and. or propagated in the atmosphere, with some being cosmic in nature as well. When you cut out that solid angle coverage you cut down that contribution. That is why Yagis (for example)are so prized---they are unidirectional and cut out most solid angles that are not being sought in the link, both at high elevations AND at most solid angle azimuths.

That noise is not man made BTW.

What I described is not a polarization issue. That's separate.

73
Chip W1YW

 

Ah...ok, so not polarization... Sky noise, then, in overly simplified terms is the background noise due to "solar weather / cosmic activity" Does that also include lightning ?

interesting.

I've found that Lightning (and man made) noise is bad enough in summer months that a vertical on the low bands can be almost worthless with the S9+60 static crashes and resulting AGC action. It's why my 160M vertical antenna comes down in March and doesn't go back up until thanksgiving.

 

My point is that a low dipole has some use for DX, and raising it helps. Keeping it below 1/4 wave high does not.