My location is simply not very amenable to installing a permanent HF antenna that covers 80m.  40m and up is fine.  I am this close to saying screw 80m and putting in a nice 40m/20m dipole of one sort or another.  Besides the narrow 80m bandwidth on a multi-band antenna, I know there are also more lobes & nulls for a given freq compared to a single or dual band antenna.  My location would support a temporary 80m NVIS antenna if the situation demands it.

My goal/context for HF radio is extended comms & situational awareness in a disaster/crisis environment.  I realize that propagation conditions vary and nothing is guaranteed, but does 80m really outperform 40m/20m often enough to justify the hassle?

"permanent 80m isn't worth the hassle" <-- change my mind.

Short answer,, yes 80 is worth it.  

You can coil load a 40M dipole so it will work reasonably well on 80.  It won't be as efficient as a full size antenna, bit it will work surprising well.  

Also, you don't have to keep your antenna runs straight.

YES!

If it truly was limited to NVIS I would skip it.  

Nothing says you cannot keep an 80m dipole on hand in a go/field box.  A home brew dipole is not a heavy investment to have on hand.


My first antenna works really well it is an MFJ 2012 OCFD. 6,10, 20, and 40m.  They have a lighter gage wire version too, the MFJ 2010.

My current antenna is a BTV5 that has a minuscule 80m loaded tip.  I finally got my through wall connection done yesterday so I won’t be passing my coax through the window.  I actually feel like I have a station now.  Still need some improvements down the line like a laptop for the station.  Running thing off an Ipad is hokey and just doesn’t work foe most software things.  

My MFJ 2012 will come down and be my spare or field antenna.  I still want to build a fan dipole with 75 and 80 m legs.  

For now I will run what I got.   So many half finished projects on hand,

I really like 80m for statewide comms. It fills that 100-400 mile range really well. A narrow bandwidth antenna works okay for me as there is only a couple frequencies I ever use. If you're using digital modes on 80m you can get away with a pretty short/compromised antenna and the software/error correction will make up the difference. My first 10 years I never really used 80m but I finally put up an antenna for it, and now that I see it's capabilities I will always try to have 80m coverage moving forward.

It's useful.

My vertical is narrow on 80. But I have my old end fed mounted on the top of my fence and it works fairly well. I have it up mostly just for 80.

Definitely worth it, but during the summer months the QRN can get pretty bad.
On CW, I can still make contacts druing the summer months with 5 Watts, but often have to crank it up to 50 or even 100 Watts for reliable copy.

One possible solution to your space problem is the Alpha Delta DX-CC 5-band loaded antenna.
It's only 82' overall and can be installed either as in a flat top or inverted-V configuration. It works on 80, 40, 20, 15, and 10 Meters but, because of the nature of the loading coils, has a narrow bandwidth on 80.

ETA: if you do decide to go with the 40/20 dipole, it can be made to perform on 15 by using Capacitance Hats.

I like 80m, the general portion sucks as it's so crowded but down in the extra allocation you can make some good contacts. As a previous poster said, it's the best way to make less than 400mi contacts. If your a general and don't care about regional nets / contacts then a 40m and up antenna is probably fine.

I have been on HF for 20 years.  99% of my activity is on HF.  I have exactly 1 80m QSO.  Some Arfcommers Brother in LA cause I needed it for WAS.  I somehow tuned my 40m dipole to 80m.  I have antennas capable of 80m now.  Just never get on it.  Maybe I should...

This is an interesting bit of info.

See that, SteelonSteel? We might have a QSO if both of us had 80m antennas.

This. I have another ARF ham about 150 miles from me and 80m is always the best bet for contact between us.

Given your need for relatively close range communications I would agree with others that 80 meters is going to be your best bet.  Needs vary from person to person and honestly the only one that can answer that question is you.

Lobes and nulls are pretty simple on a dipole, they look like a tube.  The nulls are off the ends because there is no wire to radiate in that direction.  The RF energy radiates off the wire perpendicular to the length.

Personally I'd seriously consider a multiband vertical if you are strained for space or some Inverted Vees for 80 and 40 if you are not.

That's about all I use 80 for to be honest. We have a group of us who will chit chat on 80. It's kind just an ongoing rag chew in the evenings. Then for regional comms. Otherwise I stay on 40 and up.

we should try it tomorrow!  

I am testing for extra in the morning.  I have been doing practice tests and am hitting 80-90% with a an outlier above and below.  Hopefully I don’t choke and can move my band limiter stops on the 7300.

LOL, yeah, but I do not have an 80m antenna yet! I only have that MFJ-2012 and my SWR on 80 is like 11, so I can't transmit. I do want to get something I can use for 80, though. I just don't know what to get yet.

The 2012 is an OCFD, and extensions to each side to make it resonant on 80. One of my portable antennas is a 4:1 current balun and wires to set it up for 40 & 80.  

Attached File


*Note the ratios for 80 and 40 are different.

Good luck!

op how much room do you have to work with?

As far as I'm concerned 80 is mandatory. 80 is often the only thing there when the rest die and 160 is such an oddball flake band with insane antenna requirements it's not really practical.

Ha, I was listening to the Tuesday net for the 80m on the MFJ 2012 this week.  My BTV5 was tilted down and all my radials were rolled up as I was spreading dirt and clay over my bald bed rock spots.  It rained all day and I didn’t want to tramp around in soaked clay (that stinks as it came from the bottom of my pond a couple years ago).   It listens to 80m fine.  Transmit....ahhh no.

and another good news is my dirt guy showed up yesterday to size up how much top soil I need to cover all my bad area ground projects....4 10 wheeler loads,   Yea there is the cost of an amp.  lol

I need the antenna area, my side lawn and a good chunk of my front lawn topped.  My soil is crap.

The good news is I can now go to the basement, plug in the power, flip on the power supply, warm up the IC7300, rotate the antenna switch and be in business.  No more flopping wires through the window after taking a screen out.

Well time to hit the shower and off to my exam!

PS I want to build that 75/80m fan dipole by August!

If I have to pay three test fees to pass I will.

Good luck!

In a display of my vast ignorance:

1. If I were to extend my 2012's wires to be resonant on 80, it would no longer be resonant on the other bands, right? In other words, it is an "either or" proposition rather than adding 80 and keeping the others resonant?

2. I don't understand your markings. Does it mean that I want to end up with the 2 OCFD legs at 85' 2", and 47' 9" ?

Generally speaking, that is correct.  It's been a long time since I messed with that stuff but it seems like the third harmonic will once again be resonant.  I say that because it seems like I used a 40 meter inverted vee on 15 meters (7 mHz x 3 = 21 mHz = 15 meters).  Looking back in my first log I see a few entries on 15 meters so it must have worked.  All I had up at that time were two inverted vees for 40 and 80 meters.  My guess is that it worked but didn't work very well since there aren't many 15 meter entries in the log.

Also, extending the wires doesn't have to be permanent.  I didn't have a tuner so I crimped and soldered ring terminals on the ends of my wires.  I then cut short sections of wire with a matching ring terminal crimped and soldered on one end.  I bolted the wires together and trimmed the stubs for resonance on different parts of the 80 meter band.  That way I could change the resonant point by removing one stub and bolting a different one of the appropriate length on to the main wires.  Since they were inverted vees the ends were near the ground making it a 5 minute project to change my resonant frequency.

You could do the same with yours and quickly and easily get back to where it is now by just unbolting the extensions.

https://www.ar15.com/forums/outdoors/Let-s-Make-an-OCFD/22-690848/

An 80m OCFD works fine on many bands, not as efficient as a doublet but it's easier. I use one with a bigger balun for my base antenna.

Those lengths marked on my balun are for my particular wire which is braided bare copper wire, YMMV. I have some powerpoles on the ends of the sets that are color coded to make it easier to link the extensions.

I enjoy the trivia on 80m in the evening.  Never can get in to answer as I dont have an amp.

That is a lot of fun. The amp made it easier too. I've gotten into the bucket once too.

If you can fit a 40/20 dipole you can likely fit a DX-CC. 75m is king for statewide comms in Alaska.

Does anyone know how narrow the bandwidth is on 80? I read some online reviews but nobody spelled out the details.

3.500 to 4.000 would be the full band.

I am considering how to add 80 to my capabilities, but am thinking I would prefer getting the whole band.

I am no expert but it is wide.  Too wide for a single antenna for me.   I am centered on 3.885.   My SWR meter graph shows 3.810 as SWR of 3, and 3.840 as SWR at 1.7,   on the high side of center 1.7 SWR is at 3.900 and 3.0 SWR is at 3.930.

This is on the puny tip top antenna in my Hustler BTV5.


A dipole would give you more width but I doubt the whole thing.  

My idea (stolen) is to put up a fan dipole with four legs, one pair cut for the 75m CW area and the other up in the 80m area,...maybe not where my Hustler is cut.  Might give me three choices between the two antennas.

Too many projects going now to get on that one just yet.  [img]/images/smilies/icon_smile_blush.gif[/

https://wireless-girl.com/Projects/Antennas/Broadband80mDipole.html

If you have room for 132', a doublet of that length and a tuner will get you the whole band (and several others).

Unless your 80m dipole is 150+ feet up in the air, it's mostly NVIS anyways.

The higher a dipole the lower the take-off angle, to a point of diminished returns.

80m dipole 1 wavelength above ground is 260 feet up in the air and will provide the lowest possible take-off angle for a dipole.  Most people don't do this and simply use 80m dipoles as high as they can which is usually under 50ft.  The
80m dipole is NVIS at that elevation.  Works really well for local (ground wave) and regional (400-600miles) depending on time of day and conditions.

My 80m OCFD at 50ft covers all of 80,40,20,17,15,12&10 using the tuner in my 7300. As you get more multiples of the fundamental the radiation pattern gets spikey but that's the nature of a multiband antenna.

Sorry, I meant how narrow is the workable bandwidth on 80 when using that Alpha Delta DX-CC antenna. Was curious about how much of the band I could use if I got that antenna.



I need to go out and measure how much space there is between my end trees that already have pullies. For me, the best solution would be if I could simply lower my MFJ-2012 and swap it out for another multi-band antenna that also does 80.



Your home-made one, or a commercial item?

When I ran my HF6V last month the 2:1 range was from 3.543mHz to 3.601mHz or 58kHz wide. The 3:1 range was from 3.510 to 3.629mHz or 119kHz.  The minimum SWR point was 1.565:1 at 3.573 mHz.

Shouldn't matter, they are all basically the same. Only difference is in the quality of the balun used.

I'd try extending your 2012 and see what you get. You have to get it resonant at the bottom of 80m to have the higher bands work out right.

You get about 100khz below 3:1. I can scope my DX-DD for you when I get home

I'll have to dig into the gigantic book about antennas that my buddy gave me to figure that out. Could I clip on various lengths of wire (copper to copper) to experiment?  Like using a metal binder clip as a temporary clamp to test the length. Also, does it matter if the wire has insulation on it? My antenna wires are bare and are claimed to be 67 feet long.



Cool. Thanks! No rush.

Insulation will slightly lower the resonant frequency.
IOW, it'll be shorter for a given frequency.

I'd tie another length of wire to each insulator and use an alligator clip to attach the new wire to the original one. Make total length ~137ft long with the feed point at 36%, so one side is 49'4" and the other 87'8" and see what it looks like on your VNA.

I believe you answer your own question. For regional communications I believe 80 is where you need to be.  My expectation of 2 meter repeater networks are great nearby comm but reliability may be an issue in "adverse" conditions. My efhw works great in an inverted v and I have gotten both coasts from here in WI on it. Yes it  was a struggle until I figured out where I wanted to be and frankly I turned out to really enjoy a couple of the regional nets around here. So much so I took my second radio and put up a dedicated double bazooka for 80 meters but I don't have issues with permanent placement.
I recommend keep at it you can get something to work. I had an 80 meter pota contact last Friday the the contact was working 80 meters on a Chameleon mini portable and worked great for him.

Does insulation affect RF output?



Thanks for those dimensions! currently, at each end, I have "tree > rope > insulator > antenna wire". Would it work (temporary to get lengths right) to alligator clip new wire to old wire, then run new wire out over top of the insulator and clip wire to the rope? That way, I would avoid untying the insulator until I know exactly how long to make it.

If the insulation does make a difference, it'll be so slight you'll never notice it. Remember that you must increase/decrease power by a factor of four to make one S-unit difference at the other end.

As for the difference in length, it falls into the same category. It'll be compensated for when you tune the antenna.

And yes, using the rope as a insulator will be okay unless the rope gets wet and you're running high power.

Insulation does not affect RF output. What it does is decrease the velocity factor of the wire ( that is how it is referenced but the reality is more complex than that ) so to be resonant at the proper frequency it needs to b 3-6% less length depending on the thickness and composition of the insulation. The thickness of the wire also effects the velocity factor. The thicker the wire the less the velocity factor and the shorter the wire for the same resonance.

The slowing affect of the wave propagating down the wire ( less velocity factor ) is caused by a dielectric affect of the insulation. That dielectric effect is due to a capacitance change between the wire and the free space outside the wire. Air has a dielectric constant and so does any insulation and that difference causes a difference in capacitance between the wire and the surrounding air which is the medium of propagation. It works just like changing the dielectric in a capacitor.

Just like larger plates in a capacitor increases the capacitance, so does increasing the wire size increase the capacitance between the wire and the free space outside the wire. With the increase in capacitance either from increased wire size and / or air (bare wire ) vs insulation increasing the capacitance of the boundary between the wire and free space, the resultant increase in capacitance makes the wire resonate at a lower frequency so the wire must be shorter for the freq you want compared to a thinner and / or non-insulated wire.

There are also other things that affect the resonant frequency also. Anything in the near field of the antenna, the closer the more effect it has,  such as buildings or trees is said to de-tune the antenna, the effect is a result of changing the velocity factor of the wire so to speak. People also call this coupling. Usually meant to mean making it look like the wire is longer for metal objects ( part of the radiating elements ) and shorter for non-metal objects. ( part of the dielectric effect ).  You can see a big example of this in the moxon antenna where the gap space between the driven element and the reflector is critical as it affects the resonant frequency due to capacitance between the driven and reflector elements. Same with traditional yagis where the distance between elements affects the capacitance and therefore the resonance changing the needed lengths of the elements.

At least that is how I understand it.



Yes I think your clip idea would work as long as the clip makes good RF contact with the wire


I use insulated wire on all my wire antennas because it reduces static buildup on the wire due to the metal of the wire being insulated to the air. Bare wire collects a static charge depending on conditions and insulated wire prevents much of that. MA especially along the coast is relatively humid, so there isn't much static build up to begin with. Static build up gets worse with dry dusty air and a wind blowing, ie desert conditions. Along the coast with little dust, there should be minimal static, then add insulated wire and it should reduce static build up to almost non-existent.