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Author Topic: HF Antenna Suggestion for Small Areas  (Read 904 times)

N7TWL

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HF Antenna Suggestion for Small Areas
« on: May 11, 2021, 07:13:25 AM »

Greetings!

I live in my 30ft travel trailer full-time; it's up on blocks and skirted. My lot is only slightly larger than my trailer. I've tried a variety of antennas over the last few years, but success has been really limited. I have lots of noise and no room for radials. A friend of mine suggested an end-fed half wave with the element trimmed for 40m. So I built one. I have a small tree right behind my trailer and was able to get the element (~66ft) up about 20ft, and then over the top of my trailer by another tree's branch and down a little bit to my porch roof. It's sort of an inverted L, and it works - I am on the air! I can even hear my favorite beacon - "K" - off the eastern coast of Russia. I used 14 gauge stranded wire with black insulation, and I can barely see it, so it's pretty stealthy. The design is from a Dutch ham: PD7MMA. You can go to his website and see it and all the specifications and construction diagrams. http://pa-11019.blogspot.com/2012/04/149-transformer-for-endfed-antennas-35.html

I've seen many EFHWs on eBay, but I like to make my own stuff if I can, not to mention it's much cheaper that way. Amazon has the toroids and wire for both the windings and the element. One of the pluses for EFHWs is that their general shape is not that critical, nor is the height from the ground. On mine, I did run a 30ft ground wire to a ground rod that happened to be there already. Using an MFJ antenna analyzer, I trimmed for ~ 7.050mhz and got a 1:1 match. It also tunes for 20m and 10m with about a 1.4:1 match. However, I mostly use 40m. Something for you to think about if you are cramped for space and want something kind of stealthy.

73,
Todd, N7TWL
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K6SDW

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Re: HF Antenna Suggestion for Small Areas
« Reply #1 on: May 11, 2021, 08:13:00 AM »

I too live full time in an RV parked in a highly restrictive (no antennas) controlled environment.

That said I've had great success using an endfed dipole and the simple 1/4 wave vertical with 6 ground radials. And things are getting much better as the bands are opening up to dx.

GL/ed
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N8NK

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Re: HF Antenna Suggestion for Small Areas
« Reply #2 on: May 11, 2021, 09:58:46 AM »

Hi Tood-
If you like to make  your own antennas, you should check out my work I've done using homebrew multi-tap UNUNs with end-fed antennas. The versatility is shocking. I'm also convinced that you could use your 40m EFHW on 80 as a 1/4 wave radiator. I do this with my 80m EFHW on 160, and it works fantastic. You could use your home and any other objects as a counterpoise. I only have 3 counterpoise wires for 160 and it works like gangbusters.
I have a total of $25 invested in my multi-tap UNUN and EFHW and i use it on all bands harmonically related to 80m.
My stuff is all on YouTube if you want to see.. just search fo N8NK QRP.
Chuck
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KC9QBY

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Re: HF Antenna Suggestion for Small Areas
« Reply #3 on: May 11, 2021, 02:28:17 PM »

Bound by antenna covenants here, but received reasonable accommodation from developer.  Ultimax100 (24ft) and Wolf River Coils (multi-band tunable) in use here.  The mix of take-off patterns is decent, not optimal yet it works.

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73,  Chuck  KC9QBY

W1ITT

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Re: HF Antenna Suggestion for Small Areas
« Reply #4 on: May 12, 2021, 07:43:40 AM »

Todd...  One thing that will improve the operation of any end fed antenna is to improve the RF ground.  I'm sure you are grounded for 60hz AC safety, but an RF ground will involve lots of capacitance to earth.  First, tie the ground lug on your RV  frame into your ground system.   The metal skin of most RVs is generally a mess of enameled unconnected sheets, so don't depend on it.  Drive a rod into the ground, even if it's only a four footer.  This makes a handy common point.  Then go to the farm store and get a length of welded wire fence....maybe 4 feet high by whatever length will fit under your RV.  It's actually wide enough for a pair side by each under there.  Solder pigtails onto these and connect them to the system.  You now have a stealth counterpoise.
I have used this method under an RV with good result, and I use  critter fence  ...longer lengths...under my 160m vertical at home with good results.  Just make sure it's galvanized after fabrication.  Most common chicken wire is not, and will corrode in many environments.
Any end fed antenna is only half an antenna.  You have to help it out with the other half.
73 de Norm W1ITT
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