Fan dipole fed with OWL?

[W8EJO]

I am putting up a fan dipole for 75 and 40 meters. wondering if there's any advantage to feeding it with open wire line vs coax. has anyone here fed a fan dipole with open wire line and or 450 ohm twin lead?

[N2DTS]

The advantage of a fan dipole is it works on 2 or more bands without tuning if you cut it right.
I use one for 80 and 40 meters and its got a low swr at 3870 and 7290 so I use no tuna.

OWL will always need a tuna, so why not just make the antenna as long as you can and use the tuna?

[flintstone mop]

The advantage of a fan dipole is it works on 2 or more bands without tuning if you cut it right.
I use one for 80 and 40 meters and its got a low swr at 3870 and 7290 so I use no tuna.

OWL will always need a tuna, so why not just make the antenna as long as you can and use the tuna?

That is the simplest way to do it.

Fred

[WZ5Q]

snip...

OWL will always need a tuna, so why not just make the antenna as long as you can and use the tuna?

That is the simplest way to do it.

Fred

And works FB with a LCT.

[W8EJO]

I'm thinking that it would give me lower total system loss while QSYing within each band vs coax.

Also cleaner more predictable patterns over a single wire..

[W4EWH]

I am putting up a fan dipole for 75 and 40 meters. wondering if there's any advantage to feeding it with open wire line vs coax. has anyone here fed a fan dipole with open wire line and or 450 ohm twin lead?

On 75 and 40, it won't make much difference: the big advantage of OWL is that it doesn't have as much loss as coax when the SWR is high, so it's good to use if you have a good tuner and need to work on a lot of bands.

For 75 and 40, though, since you have two dipoles, coax will be fine.

W1AC

[WD8BIL]

One problem I see happening with the OWL/tuner setup is, which impedance are you matching? The tuner will see the combined impedances of both dipoles. Sure one will be much higher but still in the mix. So you really have to find a way to determine if you are tuning the high or low impedance.

 This could also distort the pattern you are trying to accomplish. Maybe not a big problem but if you're gonna cut separate dipoles anyway take the little extra time to tune them, stick coax on 'em and be done.



 

[KA2DZT]

One problem I see happening with the OWL/tuner setup is, which impedance are you matching? The tuner will see the combined impedances of both dipoles. Sure one will be much higher but still in the mix. So you really have to find a way to determine if you are tuning the high or low impedance.

 This could also distort the pattern you are trying to accomplish. Maybe not a big problem but if you're gonna cut separate dipoles anyway take the little extra time to tune them, stick coax on 'em and be done.



 

I agree,  that was the first thing I thought when I first read this post yesterday.  I've used fan dipoles and used coax for the feed line.

Fred

[K1JJ]

I am putting up a fan dipole for 75 and 40 meters. wondering if there's any advantage to feeding it with open wire line vs coax. has anyone here fed a fan dipole with open wire line and or 450 ohm twin lead?

Probably more of a disadvantage with OWL, since you need a tuner.

As previously mentioned, tune the individual fan legs for your favorite part of the bands and use coax - that's the easiest way.  The difference in feed line loss is negligible once matched well.

As for OWL with a dipole single wire....  To avoid having a cloverleaf pattern, be sure the highest band used does not have more than 1.2 wavelengths of total length.  For a 160 - 40 M multiband dipole, then this means the dipole cannot be longer than 166' or the pattern on 40 M will start to break into a cloverleaf.

For an OWL  160 -75M dipole, then the total length cannot be more than 310' to satisfy 75M having a standard (but sharp) figure eight pattern.

For a  75 - 40M OWL dipole, then 150' total length to satisfy a figure 8 on 40M is required.  You get the idea.

So the advantage here of using a fan dipole with coax is that all bands that have a dipole pair of legs will more or less be a figure eight pattern. The patterns will not be perfect because of interactions, but pretty close to a single dipole.

The bottom line is that we really want a PREDICTABLE  pattern on all bands. If we are looking NE and SW, to have one or two (higher) bands with a huge null in those directions is a great disadvantage because these nulls can drop us down 10-20 DB or more at times.  A simple dipole pattern is really ideal for general HF band use.

T

[flintstone mop]

I'm thinking that it would give me lower total system loss while QSYing within each band vs coax.

Also cleaner more predictable patterns over a single wire..

Predictability of pattern for 75M at anything lower than a half wave length (height above ground), is still a cloud warmer. NOW at 40M you can start thinking about patterns.

Fred

[W2PHL]

I have an inverted V with 70' on each leg with 14 gauge OWL and a Johnson KW matchbox. The high impedance on 40 made tuning squirrelly. Changing feed line length to address the tuning problem wasn't an option for me so I added a 68' parasitically coupled wire to the antenna. This fixed the tuning issue and EZ-NEC modelling shows the gain on 40m improves from 5.01 dBi to 6.8 dBi.

Phil

[W1AEX]

Back in 2007 I used a 250 foot center-fed with a pair of 65 foot elements tied to the same feedpoint hanging underneath it for 160 meter and 75 meter coverage using 4 inch spaced OWL and a tuner. It worked pretty well with decent broadside lobes on those bands. It would also tune fine on 40 meters but it had a horrendously complex pattern with many lobes and nulls that made working that band very sketchy. Now and then the wind would toss the 75 meter wire elements (weighted to prevent this) up over the 160 meter elements and I would end up tack welding the wires together where they were crossed when I transmitted. When a storm brought that antenna down I never put it back up because of the poor performance on 40 meters. I ended up with a 180 foot center-fed with 4 inch spaced OWL that works very well on 160-75-40 meters with decent broadside lobes on all three bands. I suppose any multi-band wire antenna is a compromise but I've gotten lazy...

Rob W1AEX

[W3GMS]

Interesting thread since I run a single 250' dipole with open wire line feeders.  I have to agree with the 40M performance with that much wire in the air.  It has not been to much of a problem on 40M but I run QRO and that will "somewhat" mask a directional antenna issue and I can work anything I can hear.   I have considered going to either a separate 40M dipole or possible shortening the 160M half wave to make it less lobby on 40M.  At first I thought about adding some 40M elements to the antenna but not sure if that would solve the problem.  Coax fed muti-band antennas always look for the lower impedance resonant pair of wires.  It would be nice to see someone model that.  Then the OWL feed-line length gets into the equation since being a mismatched transmission line would offer its own impedance transformation.  

Joe

[K1JJ]

That's a good question about what patterns a fan dipole will produce with OWL and a tuner.

Normally when fed with 50 ohm coax, the resonant dipole leg closest to 50 ohms will hog most of the power and produce the figure eight pattern.  This gets more complex when we have a 40M fan leg used on 15M - so even though it is 1.5 wavelengths, it is still close to 50 ohms on 15 M and will show an undesirable  cloverleaf.

But what happens when we use a fan dipole that has 50 ohm resonant legs and the 600 ohm OWL feed line is looking for legs to dump its power?  It seems rather complex to me because depending on the feedline's length on a particular frequency, the swr, resistance and impedance could vary all over the place. Would the 75M dipole start to hog power on 40M because of a better 600 ohm  +j  random power transfer match and particular tuner settings?

I don't know. It would require modeling the OWL specific length with the fan legs to see.

In fantasy, it might work if we were to make 600 ohm fan legs using triple folded dipoles, but then the interactions would be a nightmare I think.

The safe way to get the predictable figure eight patterns would be to use coax with fan legs OR  use a single dipole flat top fed with OWL /tuner that is short enough to stay out of the cloverleaf length as already discussed.

I've always believed that a coax-fed fan for 160-40M  and a separate one for 20-10M was a reasonable compromise multi-band approach for decent horizontal figure eight patterns and vertical take-off angles.

T

[W8EJO]

I found this antenna site. interesting dual-band antenna. this should get me very close to my objective.
http://www.w5dxp.com/HEDZ/HEDZ.htm

[K1JJ]

Hi Terry,

Looking at the link, that looks like an end-fed Zepp, correct?  You might be better off sticking with a center fed dipole with controlled patterns, if you can swing it.

At the same link, there was another antenna shown as an all band dipole fed with 450 ohm line using pre-cut open wire line lengths in the shack to tune the system. No tuner. It also had a balun in the shack to go to the 50 ohm rig.

http://w5dxp.com/notuner/notuner.htm

If done up right, I can see how this could be an easy and fast pre-set knife switch system to cover all bands, including WARC - and the balun would actually work well in that situation because it was matched to the openwire via the pre-sets.

Interesting design.     Walt, W2DU, was given credit as one of the designers, which is very FB.

(The disadvantage is that the patterns on the higher bands (above 40M) break into multiple lobes, as expected)

T

[W8EJO]

Hi Terry,

Looking at the link, that looks like an end-fed Zepp, correct?

T

No, its center fed - 148' in length, fed with about 90' of ladder line.See text in paragraphs 7-10 of the article.

[WB4AIO]

A 150' inverted L will give nearly omnidirectional patterns on 160 and 75, and a pretty broad bidirectional pattern on 40. I even feed mine with OWL using a current balun at the (8-foot elevated) base so that the unbalanced antenna can be fed with balanced line.

73,

Kevin, WB4AIO.

[W8EJO]

A 150' inverted L will give nearly omnidirectional patterns on 160 and 75, and a pretty broad bidirectional pattern on 40. I even feed mine with OWL using a current balun at the (8-foot elevated) base so that the unbalanced antenna can be fed with balanced line.

73,

Kevin, WB4AIO.

I really  don't want to deal.with all those radials.

[WB4AIO]

A 150' inverted L will give nearly omnidirectional patterns on 160 and 75, and a pretty broad bidirectional pattern on 40. I even feed mine with OWL using a current balun at the (8-foot elevated) base so that the unbalanced antenna can be fed with balanced line.

73,

Kevin, WB4AIO.

I really  don't want to deal.with all those radials.

I use two elevated radials. Works beautifully.

73,

Kevin, WB4AIO.

[flintstone mop]

A 150' inverted L will give nearly omnidirectional patterns on 160 and 75, and a pretty broad bidirectional pattern on 40. I even feed mine with OWL using a current balun at the (8-foot elevated) base so that the unbalanced antenna can be fed with balanced line.

73,

Kevin, WB4AIO.

I really  don't want to deal.with all those radials.

I use two elevated radials. Works beautifully.

73,

Kevin, WB4AIO.

Hey Kevin you know the secret of elevated radials...........
I wish I had the space for a system like that. It would be a hazard here cutting grass and the deer roaming around.

[WB4AIO]

[...]

Hey Kevin you know the secret of elevated radials...........
I wish I had the space for a system like that. It would be a hazard here cutting grass and the deer roaming around.

No big secret -- just get them up 7 or 8 feet, that way the efficiency goes way up and people and most animals can walk under them unhindered. Place them symmetrically 180 degrees apart at the base so they don't radiate or pick up noise. That's about it!

73,


Kevin, WB4AIO.

[KD6VXI]

Elevated radials rule!   I put them at the eave level on the house.   4 of them.

As to owl feed,  what I found most important was having a counterpoise tha was resonant.   Or at least nearly so.

Ie,  I ripped the matching network put of an old Cb ground plane.   Worked well tuning ten and 11.  Tried 12, got all kinds of rf in the shack,  etc.   Extended the radials to be resonant on 12 meters and the antenna worked great,  ladder line fed,  ten and twelve.

--Shane
KD6VXI