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Author Topic: Help narrowing HF antenna options  (Read 857 times)

W9IQ

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Re: Help narrowing HF antenna options
« Reply #15 on: February 26, 2020, 04:52:59 AM »

The ends of a dipole can have relatively high voltage even if you are running just 100 watts. The voltage can be higher than average wire insulation can withstand. You should use some type of insulator - especially near the ends of the dipole. Common plastic or ceramic "egg" insulators with the other end tied to a rafter or truss brace will provide sufficient insulation. Tying the end of the dipole directly to a rope will also work. Use a synthetic rope type that doesn't absorb moisture.

Using insulated wire doesn't hurt or help the dipole. When it is insulated, the dipole will be a couple percent shorter in length due to the dielectric properties of the insulation.

Don't forget to use a good 1:1 choking balun at the feedpoint of your dipole. You and your neighbor's homes will generate a fair bit of RFI from modern household electronics. Using a choking balun will help keep that RFI from coupling into your antenna during receive. It will also keep RF off the shield of your coax when transmitting so that you have less chance of interfering with your household electronics.

There is the possibility that your transmitter will get into the nearby HVAC and other wiring. You may wish to pick up some #31 ferrite toroids or clamp on cores so that you can wind thermostat wires, etc. around them to choke off that problem. The clamp on types are nice in that you don't need to unhook your wires to put the ferrite around them. Don't use any old clamp on core - get type 31 mix to have the best results. If you can wind a few turns around it when you install it, you will increase its choking ability.

- Glenn W9IQ
« Last Edit: February 26, 2020, 04:58:17 AM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

W1VT

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Re: Help narrowing HF antenna options
« Reply #16 on: February 26, 2020, 06:33:31 AM »

Attic dipoles can work, but these days they often suffer greatly on reception from devices in the home.  If you have noisy   ceiling lights wires in the attic will be right next to your antenna!

For best reception I would use an Inverted L.  Run a wire fed at the base of the oak tree, run up the tree, and back to towards the house.  But, the HOA politics may not allow this.

The Freedom to Display the American Flag act typically allows flagpoles despite the objections of HOAs.

A null cancelling device like the Timewave ANC-4 or the MFJ-1025 can be used to provide a receive only input on rigs that don't have that feature.  Just set the gain of the RX antenna to max and the gain of the main antenna to min.

Zak W1VT
« Last Edit: February 26, 2020, 06:36:33 AM by W1VT »
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WA9AFM

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Re: Help narrowing HF antenna options
« Reply #17 on: February 26, 2020, 08:24:08 AM »

The XYL and I 'downsized' about two years ago from 1 acre to a 'zero lot-line' gated community.  When you mentioned the 75' fence, I leaned forward in the saddle as that's what I'm using.  Our perimeter fence makes a dandy antenna support form my EFLW.  I go 50' one direction and 123' the other with the balun ground mounted next to the ATU; sort of a OCFD.  You didn't mention what materials the fence is made of, but if it's a wood stockade structure, running a long wire long the top rail works nicely.  Not a beam at 70', but it gets you on the air on the low bands.  Think out of the box.
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K6AER

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Re: Help narrowing HF antenna options
« Reply #18 on: February 26, 2020, 08:31:38 AM »

Depending on the size of the oak tree you could put up a vertical loop around the circumcise of the tree. Feed the wire with ladder line connected to a 4:1 balun.  Depending on how much wire you can make the loop out of, with a normal antenna tuner, you should be able to operate 40-10 meters.

When placing the wire into the tree uses an insulated Black wire. It is harder to see than a light colored one. You can plae the ladder line next to the trunk away from your neighbors prying eyes.
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K5IDL

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Re: Help narrowing HF antenna options
« Reply #19 on: February 26, 2020, 08:55:27 AM »

I looked up some EFLW and found a couple that would fit in my ~70' run. Forgive my ignorance but are you saying you have a autotuner outdoors and on the ground?

The fence is a standard wood fence but the posts are metal (steel I believe).

The XYL and I 'downsized' about two years ago from 1 acre to a 'zero lot-line' gated community.  When you mentioned the 75' fence, I leaned forward in the saddle as that's what I'm using.  Our perimeter fence makes a dandy antenna support form my EFLW.  I go 50' one direction and 123' the other with the balun ground mounted next to the ATU; sort of a OCFD.  You didn't mention what materials the fence is made of, but if it's a wood stockade structure, running a long wire long the top rail works nicely.  Not a beam at 70', but it gets you on the air on the low bands.  Think out of the box.
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K0UA

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Re: Help narrowing HF antenna options
« Reply #20 on: February 26, 2020, 12:25:05 PM »

I looked up some EFLW and found a couple that would fit in my ~70' run. Forgive my ignorance but are you saying you have a autotuner outdoors and on the ground?

The fence is a standard wood fence but the posts are metal (steel I believe).

The XYL and I 'downsized' about two years ago from 1 acre to a 'zero lot-line' gated community.  When you mentioned the 75' fence, I leaned forward in the saddle as that's what I'm using.  Our perimeter fence makes a dandy antenna support form my EFLW.  I go 50' one direction and 123' the other with the balun ground mounted next to the ATU; sort of a OCFD.  You didn't mention what materials the fence is made of, but if it's a wood stockade structure, running a long wire long the top rail works nicely.  Not a beam at 70', but it gets you on the air on the low bands.  Think out of the box.

Yes, there are many auto tuners that are weatherproof and designed to sit outdoors. Advantage no extra loss in the coax due to High SWR on said Coax.  The coax is matched to the INPUT of the autotuner and extra losses are thus avoided. Many can be fed with power over that same coax via a included (usually) device called a Bias T. A way of inducing DC voltage and RF over the same coax.

These tuners are not to be confused with tuners designed to sit in a nice comfy environment of your shack. They are not the same thing.
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73  James K0UA

WA9AFM

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Re: Help narrowing HF antenna options
« Reply #21 on: February 26, 2020, 04:06:38 PM »

I looked up some EFLW and found a couple that would fit in my ~70' run. Forgive my ignorance but are you saying you have a autotuner outdoors and on the ground?

The fence is a standard wood fence but the posts are metal (steel I believe).

The XYL and I 'downsized' about two years ago from 1 acre to a 'zero lot-line' gated community.  When you mentioned the 75' fence, I leaned forward in the saddle as that's what I'm using.  Our perimeter fence makes a dandy antenna support form my EFLW.  I go 50' one direction and 123' the other with the balun ground mounted next to the ATU; sort of a OCFD.  You didn't mention what materials the fence is made of, but if it's a wood stockade structure, running a long wire long the top rail works nicely.  Not a beam at 70', but it gets you on the air on the low bands.  Think out of the box.
Yes, to keep it low profile.  It's an LDG Z11ProII in a weatherproof case.  I run it off a 12vdc 7amh battery.  Works quite nicely.  The LDG RT-100 remote tuner is a spin off of the Z11.
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K5IDL

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Re: Help narrowing HF antenna options
« Reply #22 on: February 27, 2020, 07:53:27 AM »

Thanks all, this has been very educational. I'm going to put a dipole in the attic to get on the air initially. I'm looking into stealth options for the backyard or possibly getting something I can setup/take down quickly and easily as an alternative down the road. I'll probably have questions about that down the road. A flagpole is tempting but the cost is more than I'd want to spend for now.
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KC9QBY

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Re: Help narrowing HF antenna options
« Reply #23 on: February 27, 2020, 08:29:53 PM »

HOA here too, but they were not wicked.  In my case they approved End Fed dipole between a mast off deck and corner of house, using Ultimax 100, and pretty happy with Rx: 80, 40, 20; just getting feet wet Tx (new General).  Plenty of reviews of that antenna on Eham.  It's a modest start, with pix on my QRZ page.

Agree with other observations on noise. Liberal application of mix 31 toroids helpful, but it's looking like rotatable receiving loop probably wise.

Certainly not HF, but enjoying Yaesu Wires-X for proxy long distance.

Good luck,

73,

Chuck
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73,  Chuck  KC9QBY

K5IDL

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Re: Help narrowing HF antenna options
« Reply #24 on: March 11, 2020, 07:33:55 AM »

TL;DR I think the 20m in the attic was a good place to start. Thanks to all who chimed in.

I've had the 20m dipole in the attic for a couple of weeks now and wouldn't to post a progress report in case anyone else is considering one. The SWR is about 1.12 after quite a bit of trimming. The SWR at HF frequencies higher than 14MHz is about 4.5:1 so higher than my 7300 can tune. I might get a tuner but evaluating antenna options is a higher priority.

When my HVAC system (in the attic) runs it generates enough noise to degrade transmit and receive. Fortunately this time of year it doesn't run much. If I compare the noise on my scope vs watching people operate 7300s on YouTube I'd say it doesn't seem out of the norm. I'm studying RFI mitigation as well as getting an antenna outside.

My propagation on 20m with FT8 seems good compared to other local stations though I probably use more power. From Texas both coasts and much of Canada hear me consistently and I can do QSOs every day (generally 1,000-1,6000 miles distant). I have a few QSOs with ocean locations E.g. Cuba, HI. I periodically hear EU stations but I don't recall managing a QSO with one. For a compromised antenna this seems to be doing "ok" on digital modes.

I haven't put any real effort into phone. From a listening standpoint I hear clearer transmissions on 40m and 80m. I do plan to try another digital mode, maybe PSK31. I just need to make Fldigi happy with my rig.
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K0UA

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Re: Help narrowing HF antenna options
« Reply #25 on: March 11, 2020, 07:56:33 AM »

Years ago I stapled small wire to attic rafters without ill effect for an attic dipole. As long as the wood stays dry it if a pretty good insulator. No attic antenna will work quite as well as an outdoor antenna away from the house, but they will work. Not long ago I made a 40 meter wire vertical suspended from some parachute cord  between two trees with two elevated radials and it works very well.
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73  James K0UA

K1VSK

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Re: Help narrowing HF antenna options
« Reply #26 on: March 11, 2020, 09:25:17 AM »

Lots of hOAs provide for residents to seek and obtain approval of variances or accommodations from various property limitations. My suggestion is to do that first before limiting yourself to an attic antenna which will be problematic given all the duct work and metal contained therein.

It might be possible to run an exterior wire they might approve, any variant being preferable to one in an attic. As you apparently haven't requested a modification from the rules,  you are designing an antenna without first knowing your options. Dont know until you try.
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N2AOO

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Re: Help narrowing HF antenna options
« Reply #27 on: April 22, 2020, 07:13:12 AM »

I live in an HOA community in a suburb of Jacksonville FL.  I put a 40 meter dipole in my attic running it from corner to corner.  It’s attached with plastic cable ties to to nails in the rafters and works surprisingly well.  I did have a 17 meter dipole attached to the same feed but it never worked.  Not sure why.  Meanwhile I’m thinking of attaching a 20 meter dipole to the 40 meter.  In a previous home I had run a dipole under the eves including around corners.  That also worked well.  Regards, John
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N4UM

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Re: Help narrowing HF antenna options
« Reply #28 on: April 22, 2020, 10:10:37 AM »

I have a 40 thru 10 meter EFLW fed with a 49:1 homebrew transformer in my attic.  It transmits well but has difficulty receiving because of all the ambient house noise.  A similar antenna mounted out on your fence could be worth trying.  It will not require a remote autotuner.  Your can wind your own transformer on a ferrite core and house it in NEMA box or purchase a commercially made transformer with wire for about $100.  If you want to go really on the cheap you can construct a PVC "flagpole" and house a quarter wave wire for 20 meters (about 16.5 ft.) onside.  Use lawn staples to install 16 or more radials between 10 and 15 feet in the grass around the "flagpole."  You might even get away with using a fiberglass fishing pole or outrigger pole with a small windsock or flag to house the vertical wire.  I also have a Hustler vertical housed in a homebrew fiberglass flagpole with 50 20 ft. radials as a backup antenna.  Flagpoles up to 20 ft. are permitted in HOAs under Florida law. My verical covers 40,30,20,15 & 10 meters.
My go-to antenna is  an EFLW fed with a transformer as an inverted L.  The 20 ft. vertical wire runs upward stood off a foot away from the back gable end of my house to the peak and then runs across the back yard to a tree.  I have 30 33 ft. radials fanning out in the grass from the feed point in a semi circle. I have had the wire up for a number of years and no one in my HOA has complained about it YET. It's not visible from the street and doesn't seem to bother the neighbors.
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