Other SOTA sites: SOTAwatch | SOTA Home | Database | Video | Photos | Shop | Mapping | FAQs | Facebook | Contact SOTA

Seven SOTA antennas compared using WSPR on a summit


#21

Pedro, “adding a 2nd radial” must not be read as “adding a 2nd radiator”, hi.
So the existing 9.15m radiator (without 1:9 unun) with newly 2 radials of 4m each could be used as a vertical, inverted-L or inverted-V.

This antenna would then look very similar to my compact 60-10m vertical (inverted-L or -V) consisting of a 9.10m radiator, 4 radials of 4.20m each, fed through a common mode choke (photos). The antenna base is usually attached to the mast at about 0.5m over ground or, if the mast is fixed to a metallic structure, kept away some meters and fixed on a tent peg. This antenna connected to a KX3/ATU performs very well.


#22

That’s really interesting, Manuel! Great project! It would be interesting to also have some more compromised antennas tested and compared in the future as well. I recently bought a HF-P1 portable antenna especially for SOTA and WWFF activations. It’s basically a clone of the well known Super Antenna MP-1. It’s a vertical of about 2.5 meters in length and can be used from 80 to 10m HF. It’s loaded with an adjustable coil and has 4 radial wires connected to its base. I’m sure it will not perform as well as the HyEndFed 10/20/40 EFHW wire antenna I normally use, but I bought the HF-P1 because it’s much easier to carry and take up on a mountain, it’s easier to set up, and with its tripod it’s self-supporting (not always there’s a structure available to strap the 10m fiberglass pole to for the EFHW)
Would be interesting to see how the HF-P1 compares to the other antennas in a WSPR analyses as you presented here, especially on 40m. I’ve been making some CW QSOs at 5 Watt on 40m with the antenna in my garden surrounded by houses and other structures everywhere, so it does work, but what will the difference be compared to the other antennas?

Keep up the good work!

Vy 73 de Michael PA7MDJ


#23

Heinz, I am always impressed by the standard of your construction, and the nice touches like the BNC dust cover in this case. Seeing such things encourages me to raise my construction standards!

I have to ask you, what is the thinking behind three bolts to mount the BNC connector? In your case it cannot be an oversight, or saving the effort of drilling another hole! Of course three is mechanically sound, but the manufacturer has provided four holes… Saving weight? :smile:

Adrian
G4AZS


#24

Thanks, Adrian!

Re: "Dust protection"
The cap for the BNC jack was added primarily as a protection against damage in the backpack.

Re: "Three mounting bolts"
You almost guessed it, hi.
First, this connector type was choosen because of its low installation height.
Second, two screws would suffice from mechanical and electrical point of view but because for practical reasons the 2 screws (soldering lugs) for attaching the coax shield should be close to each other, a third screw was installed. Of course, from a purely cosmetic point of view, a fourth screw could be installed, hi.


#25

Ah, yes - I didn’t notice the two lugs! I knew there would be a good reason, thanks Heinz.


#26

Hi Heinz

I misunderstood your text and the fact that is complementing the one of ON7DQ. SRI

Now, and with the pictures and did another reading it’s clear. :slight_smile:
Your building skills are top notch! Congrats!

Do you performed any comparison with other antennas or modeled it in in the eznec or similar ?
That would be interesting.

73 de Pedro, CT1DBS


#27

Good work guys…this kind of real time comparison is really useful. Of course, all sorts of local anomalies can impact results; different aerial heights, different orientations, take off et al but this at least gives some sort of baseline empirical guide and with more people repeating the comparisons we should build up a useful indicator of ‘real’ performance.
I was particularly impressed by the consistency of the vertical with one counterpoise. Looking a the lengths of the radiator and the counterpoise is this simply a random length wire mounted vertically?
I’m inspired to try this one out…

Michael (G0POT)


#28

I guess one could look at it that way… The performance of this arrangement has impressed me as well, especially since the radial was lying in the grass and not elevated. What wasn’t mentioned in the PDF is that the KX3 was placed right at the base of the pole, so the radiator wire coming down from the mast could be connected directly, without any balun or coax whatsoever. This may not always be convenient.


#29

Useful and informative. Thank you


#30

Thank you. Good work. Please consider including a dipole in you future tests. It is a common SOTA antenna.

73
Doug W1DMH


#31

I just wanted to add a comment to the conversation. I activated Saturday with a 9m long wire end-fed through a 9:1 UNUN (homebrew) into a KX3 ATU and it performed EXTREMELY well on 20M. My impression was that it was the equal of my usual antenna, a resonant EFHW (through an 81:1 UNUN)

I suspect the issue with the EARC antenna was the matchbox.

73, Barry N1EU


#32

Barry,
Any sort of counterpoise with the 9m end feed?

Malen
VE6VID


#33

No, that’s the beauty of it. The coax shield serves as the counterpoise.

Barry N1EU


#34

What I do not understand about the EARC design is why they use a coax cable from the 8:1 UNUN to the tuner. Since the impedance at the transceiver-side of the UNUN will be different from 50 Ohm, coax cable will likely cause higher losses. Wouldn’t it make sense to attach the tuner directly to the UNUN and use a separate wire as the counterpoise?

At least that is what I am trying with my new SOTA vertical: Attaching the T1 tuner directly to the mast in ca 80 cm height above ground in order to avoid any coax between the unmatched radiator and counterpoise and the tuner.

Martin


#35

I played with an efrw last summer with zero results. 9 metres of wire and the only time that my KX2 's tuner like it was with a 5 metre counterpoise. I guess it’s time for me to revisit this over the cold months. I will start with the 9:1 and go from there.


#36

Barry,

How well did that antenna work on other bands? Nine meters of wire is getting pretty close to 1/2 wavelength on 20 meters. I’ve used this type of antenna (EARC) for quite a while at home and on the two activations I’ve done so far and have been happy with it. It may well be a compromized design regarding the coax length between the ATU and the unun, but it is compact and easy to set up, and seems to have acceptable performance.

Patrick - ac0sr


#37

Patrick, I’m activating tomorrow with 9m EFRW on 17M and 30M cw (and maybe 40M) fed with 6ft of RG58 through a 9:1 UNUN (wound on a -61 core) into KX2 ATU. I’ll let you know how it goes.

Barry N1EU