Thinking about a new HF antenna at home...

[AK9R]

...And, I'd like to tap the collective knowledge of this group.

First image is my current HF antenna arrangement. It's essentially a fan dipole with a Balun Designs bal-un as the feedpoint, but I don't remember if it has a transformation ratio. Could be 1:1 or could be 4:1. My primary issue with the current arrangement is that I'm limited in band coverage and have limited bandwidth within the band. The secondary issue is my antennas are "cloud burners", but I'll talk more about that later.


Here's what I'm thinking about as a future antenna. One thing to keep in mind is that I have covenants to deal with that preclude outdoor antennas. I'm sneaking through the restrictions by maintaining a low profile. Both of the options shown below would be an multi-band end-fed halfwave antenna using a My Antennas balun. Option 2 could be shortened as required with an insulator and rope.

I have mixed requirements with my antennas. I'd like to maintain statewide coverage on 75m and regional coverage on 40m which I do pretty well with my current antenna. But, DX is a real problem. I'm hoping that option 1 or option 2 would be better than what I currently have, though I realize that I'd still be swimming upstream.


So, what do you folks think? Will either option 1 or option 2 work for me? Or, am I going about this all wrong? Is there some other arrangement I should consider?

 

[prcguy]

On option 2 can you fit a 133ft long wire? If so I would recommend the 80-10m MyAntennas OCFD which is what I run at home. Its fed 25ft from one end making it easier to run coax in your situation. This antenna natively resonates in the low end of 80m and there is an easy mod to raise that to cover 3.8-4.0Mhz with a great match that doesn't affect any other band. I don't need a tuner on 75, 40, 30, 20, 17, 15, 12 or 10m, I just connect my 1.2kW amp and transmit. MyAntennas uses the "correct" type current balun in their OCFD that places little RF on the feedline where most antenna mfrs use a voltage balun that lights up the coax with lots of RF. I do use a choke balun in the feedline anyway as insurance.

Here is the antenna which has gone up in price over the years but its the best OCFD I know of.

OCF-8010E-3K – MyAntennas.com

 

[dkcorlfla]

I would keep the cloud burner for the 40 and 80 NVIS and setup a vertical for DX on 20 and up. Maybe a flag poll antenna for the stealth factor.

 

[prcguy]

Here is what my mod looks like, fold the antenna in half, cut in the exact center, install an insulator with a few inches of flying leads and connect a HV 150pf capacitor. I use a doorknob cap but HV disc types work fine. Only the 80m range will be shifted up to 75m with no other affects.

The 400pf cap shown below was to get dimensions right while the 150pf cap was on order and its just to show the mechanical connections.

to

 

[prcguy]

I would keep the cloud burner for the 40 and 80 NVIS and setup a vertical for DX on 20 and up. Maybe a flag poll antenna for the stealth factor.

I supplement my OCFD with a Hexbeam.

 

[AK9R]

On option 2 can you fit a 133ft long wire? If so I would recommend the 80-10m MyAntennas OCFD which is what I run at home. Its fed 25ft from one en

Is that 133 feet total split into legs of 25 and 108 feet?

 

[prcguy]

Is that 133 feet total split into legs of 25 and 108 feet?

Yes. It works out nice for me because the ends of my antenna are basically off the property line and an end fed would have needed coax run off the property. With the OCFD the coax drops down next to my tower and joins a bunch of other coax going into the garage. Looks like a similar situation for you.

 

[prcguy]

I have a spare or two if you want to borrow one for testing, just pay postage. One is factory and the other I bought just the balun and used my own wire. I think both have the capacitor mod.

 

[AK9R]

@prcguy Thanks for the offer. I'll consider it.

First off, I tried a Buckmaster 7-band OCF several years ago, but wasn't happy with the performance. I think the biggest issue was that Buckmaster recommends that the feedpoint be at least 30 feet AGL. I don't think I can do that without attracting unwanted attention. I concluded that my fan dipole worked better on the lower bands, so I took down the Buckmaster antenna and sold it.

I've redesigned the layout for a myAntennas OCF-8010E-3K and show it below. Two concerns: the feedpoint at 20 feet, the 82.5 deg bend in the long element. Aside from my concerns, do you think this will work?

I like your idea about adding the capacitor to move the 80m resonant point into the 75m part of the band.

@dkcorlfla For the higher bands, I've used a 27 foot non-resonant vertical fed with an Icom AH-4 tuner mounted at the base of the antenna. It works OK. Biggest problem is that it's only rated for 120 watts. I'd like to run about 500 watts, but I'd exceed Icom's ratings for the tuner. There aren't many high-power remote-mount tuners on the market.

 

[prcguy]

@prcguy Thanks for the offer. I'll consider it.

First off, I tried a Buckmaster 7-band OCF several years ago, but wasn't happy with the performance. I think the biggest issue was that Buckmaster recommends that the feedpoint be at least 30 feet AGL. I don't think I can do that without attracting unwanted attention. I concluded that my fan dipole worked better on the lower bands, so I took down the Buckmaster antenna and sold it.

I've redesigned the layout for a myAntennas OCF-8010E-3K and show it below. Two concerns: the feedpoint at 20 feet, the 82.5 deg bend in the long element. Aside from my concerns, do you think this will work?
View attachment 187365
I like your idea about adding the capacitor to move the 80m resonant point into the 75m part of the band.

@dkcorlfla For the higher bands, I've used a 27 foot non-resonant vertical fed with an Icom AH-4 tuner mounted at the base of the antenna. It works OK. Biggest problem is that it's only rated for 120 watts. I'd like to run about 500 watts, but I'd exceed Icom's ratings for the tuner. There aren't many high-power remote-mount tuners on the market.

All OCFD antennas should radiate about the same on the harmonic related bands at any given height, so the Buckmaster 30ft recommendation is not specific to their antenna. Many versions with a lousy balun will radiate off the vertically hanging coax and that can be beneficial for DX in some cases if you choke it at a resonant point in the coax. MyAntennas has found a feed point a little different than most OCFDs giving them more useable bands and very little RF on the coax. I've used my 80-10m OCFDs camping at around 20ft high, mostly on 80/40m and they put out a good signal.

I think the redesigned layout is not a good idea and will degrade performance creating less than a 90deg bend. These antennas should not make much of a bend and option 2 above looks ok to me. At 20ft high it will be a good NVIS antenna on the lower bands but its a little low for optimum DX on 20m and above and that holds true for any horizontal antenna at that height. I think 30-35ft high is optimum for an 80-10m multiband giving the best DX on 20m and above and its about 1/4 wavelength high on 40m being the best compromise for 80-40m NVIS.

 

[devicelab]

Here's what I'm thinking about as a future antenna. One thing to keep in mind is that I have covenants to deal with that preclude outdoor antennas. I'm sneaking through the restrictions by maintaining a low profile.

Any restrictions on flag poles?

ZeroFive Antennas | Vertical Antennas For HF Radio and Ham Radio Communications

 

[AK9R]

Any restrictions on flag poles?

No. I have used Zero Five's 27-foot vertical tuned with an Icom AH-4 at the base of the antenna as I mentioned in post #9. Worked Hawaii on 80m with it. But, it's useless for 80m at short distances.

 

[devicelab]

Roger that. Sorry I didn't read the entire thread. Verticals aren't ideal for NVIS operations.

You could try the Chameleon MPAS antenna. They have NVIS hybrid configurations that could be stealthy.

The MPAS uses high quality parts but it can be a bit finicky to get max performance.

 

[prcguy]

Roger that. Sorry I didn't read the entire thread. Verticals aren't ideal for NVIS operations.

You could try the Chameleon MPAS antenna. They have NVIS hybrid configurations that could be stealthy.

The MPAS uses high quality parts but it can be a bit finicky to get max performance.

The Chameleon MPAS has a 5:1 balun and there is no configuration that would come even close to an 80-10m OCFD. I have an MPAS and have tested it in end fed mode with its 60ft of wire side by side against a 64ft 40M EFHW and on 40m the MPAS was only down a dB or so but on higher bands the MPAS got much worse. The MPAS with 60ft of wire will be waaaay down on 80m compared to a 133ft OCFD or EFHW.