Increasing bandwidth on an Inverted V ?

[kc5uta]

Pretty sure this may be an old question, but I've had no luck getting a straight answer on the internet (surprise surprise )
so here it goes.........
Premise: An inverted V dipole is efficient, but at the lower frequencies can be quite narrow-banded. Cut a wire for 1.8, it may not tune well at 1.990 etc. a compromise is to cut it for the center of the bandwidth, and or play with ladder line, baluns, tuners etc.

Question. If you cut a dipole and tune it for say just above 1.8, then cut another one tune for just below 2mhz (sort of like a fan dipole) would it increase that particular bands bandwidth? (it's understood that some pruning may be needed on each wire)

sadly the search engines all direct to either cage dipole, or mutiband dipoles, and NOT that particular way of increasing usable bandwidth.

 

[popnokick]

Forget the center-fed, single-band (mostly), narrow freq range dipole. Use an off-center fed dipole (OCFD). LOTS of info on them here on RR and everywhere else on ham-related sites. Many fewer wires and much less complexity.

 

[N1EXA]

Google the word ( CAPACITANCE HAT ) for an antenna -This will give the antenna some more band width.

Cutting 2 antenna's and getting them to Resonate so close to the same frequency will not work.

Even Resonate traps would be hard so close to gether. The Grid dip meter gets you in the ball park but there is silll lots of tuning.

Pete N1EXA

 

[RU55]

Question. If you cut a dipole and tune it for say just above 1.8, then cut another one tune for just below 2mhz (sort of like a fan dipole) would it increase that particular bands bandwidth?

I would certainly think so. The question that I wonder is how much broader would the bandwidth be. I also wonder if a caged dipole was made with for elements per side, two slightly longer that the others making a caged fan dipole.

 

[RU55]

Cutting 2 antenna's and getting them to Resonate so close to the same frequency will not work.

Could you explain why? I don't have any experience doing this, I'm just curious.

 

[kc5uta]

Google the word ( CAPACITANCE HAT ) for an antenna -This will give the antenna some more band width.

Cutting 2 antenna's and getting them to Resonate so close to the same frequency will not work.

Even Resonate traps would be hard so close together. The Grid dip meter gets you in the ball park but there is silll lots of tuning.

Pete N1EXA

Really? now THIS is the very reason I posted the question. I could NOT find a good answer! Thank you very much....I'm all ears! this may save me an exercise in futility.

 

[prcguy]

A capacity hat will not add much BW but it will shorten the antenna some. If you make the dipole a bow tie shape as in a loop of wire for each element that tapers outward from the feedpoint to 10ft or 20ft wide at the end, that will widen it up quite a bit. Something like this but this example is for 40m.

 

[kc5uta]

View attachment 133819
[/QUOTE]
yeah I considered the Bowtie as well.. I have the acreage for a full size loop for 160, just not a decent way to get it up in the air......yet, plus . my Windom is not cutting it like I want it to

 

[mastr]

I know what the "books" say. I also know that in my experience, this "...If you cut a dipole and tune it for say just above 1.8, then cut another one tune for just below 2mhz (sort of like a fan dipole)..." idea has worked for me on both 160 and 80 meters. The SWR wasn't flat by any means, but the usable bandwidth was increased. All it will cost to try in your case is time, wire and a few insulators- go for it.

 

[kc5uta]

That's what I was thinking, but finding any documentation with online searches was an exercise in frustration. What kind of spacing between elements did you use? I was thinking about about two feet apart.

 

[mastr]

That's what I was thinking,...What kind of spacing between elements did you use? I was thinking about about two feet apart.

It has been a while since I did the 160- I think it was about 4 feet. But I think 2 feet apart would be better than a single wire. Might work even better if you could put spacers between them- like a cage dipole except just 2 wires. 1/2 inch PVC plumbing pipe makes easy spacers.

 

[prcguy]

I would go much wider for a 160m dipole and instead of two individual wires connect them together at the far ends to make a long skinny triangle. Look at the 40m bow tie example above, the ends are over 30ft apart and connected.

That's what I was thinking, but finding any documentation with online searches was an exercise in frustration. What kind of spacing between elements did you use? I was thinking about about two feet apart.

 

[N1EXA]

Could you explain why? I don't have any experience doing this, I'm just curious.

Feed point impedance would be questionable at best -Im sure with a tuner and Balun you could get it down to a point where the radio is not mad.

If 234/2.0=117 feet and 234/1.8=130 feet you can make 1 dipole with some resonat traps at 1.80 so mhz and keep your feed point at a known
number.

Im sure you can cut 2 dipoles like the guy said and spread them out but besides the SWR Issue is getting this pig in the air will require
some property investment and flag poles or tree's

Id go with capacitance hats and resonate traps myself and get a happy spot where it works. make the Traps out of Clorox or Coke plastic Bottles and use rg 8 or 213 legnths as capacitors - the coax is easy to cut to tune and if you mess up just use another piece.
use brass welding rods a capacitance hats -any welding shop sells them by the bunch.
Pete N1EXA

 

[prcguy]

I have a 160/80/40m trap dipole using Reyco/Unadilla traps and its really narrow band on 160. I cut it long to resonate around 1.8MHz then I double back the end wire and shorten it to resonate at other parts of the band. At a low height like 35ft it doesn't work well at all on 160 and a 32ft vertical over some ground radials with an auto tuner at the base works much better. You need to get a 160 dipole up maybe 60ft or more for it to start working and even at 100ft high it would still be a cloud burner.

Feed point impedance would be questionable at best -Im sure with a tuner and Balun you could get it down to a point where the radio is not mad.

If 234/2.0=117 feet and 234/1.8=130 feet you can make 1 dipole with some resonat traps at 1.80 so mhz and keep your feed point at a known
number.

Im sure you can cut 2 dipoles like the guy said and spread them out but besides the SWR Issue is getting this pig in the air will require
some property investment and flag poles or tree's

Id go with capacitance hats and resonate traps myself and get a happy spot where it works. make the Traps out of Clorox or Coke plastic Bottles and use rg 8 or 213 legnths as capacitors - the coax is easy to cut to tune and if you mess up just use another piece.
use brass welding rods a capacitance hats -any welding shop sells them by the bunch.
Pete N1EXA

 

[N1EXA]

Really? now THIS is the very reason I posted the question. I could NOT find a good answer! Thank you very much....I'm all ears! this may save me an exercise in futility.

Capacitive hats on wire dipoles?

Capacitive hats seem to be advertised as an option for mobile vertical antennas. One mentioned advantage is the they can widen the SWR bandwidth, making the antenna easier to tune. What might be ...

ham.stackexchange.com

Here is what you need to read about the topic!
Pete N1EXA

 

[RU55]

Feed point impedance would be questionable at best ...

That is interesting. I've never made a "fan" dipole, but it is easy enough to try. I love to experiment with antennas and wish I had more time to do so. Thanks for the reply.

 

[N1EXA]

That is interesting. I've never made a "fan" dipole, but it is easy enough to try. I love to experiment with antennas and wish I had more time to do so. Thanks for the reply.

On the 160 Topic
Dont think it one or the other antenna is going to resonate seperatly - There is a point in the band say 1.90 for example where both antenna's would be at the non resonate frequency throwing a mean SWR and with now both antenna's radiating the feed point would not be low impedance as expected. Thats when Hams start making counter poises and chokes to fix the problem - Now your just compounding it .
You start with an Auto tuner and get fooled its brought your SWR Low - Yah it did but the antenna will not radiate any energy.
FOr Fun !
Fan Dipoles work great - But remember each antenna is on a seperate band and yah you can get bit that one is 1/4 wave on one and 1/2 wave on another band if you start making be a 1 that does all antenna.

Ive been into the 9:1 balun route lately - Slopers or half verticle / half horizontal - All kinds of legnths give different results.

9:1 Impedance Transformer

I have constructed a 9:1 unbalanced to unbalanced (unun) impedance transformer based on a published design by Peter VK6YSF. Over the next six months or so my plan is to experiment with an Inv…

vk1nam.wordpress.com

Always fun to experiment - Thats how you learn !
Pete N1EXA