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Author Topic: End Fed Half Wave under concrete tile roof - should I bother?  (Read 422 times)

KO4EGA

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End Fed Half Wave under concrete tile roof - should I bother?
« on: September 09, 2021, 12:21:01 PM »

Hello everyone.
I have a slightly used MFJ 1984 LP 10-80 end fed and I'm considering an attic install. I will be using a Xiegu G90 for a radio, with max 20 watts.  My roof is plywood with tarpaper, covered by concrete tile. The house is older and the central air ducts are made of sheet metal.   I'm I asking too much from 20 watts to deal with the tile and metal ducts?  Working primarily FT-8, but would like to try working phone in the future.  Thanks in advance for your opinions.
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GRUMPY2021

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Re: End Fed Half Wave under concrete tile roof - should I bother?
« Reply #1 on: September 09, 2021, 01:39:55 PM »

You'll get 45 replies with 75 different answers.  No one knows your exact conditions.  In the spirit if amateur radio here's an idea... TRY IT.    Let us know how it works.   I bet you'll be surprised.   
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G8FXC

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Re: End Fed Half Wave under concrete tile roof - should I bother?
« Reply #2 on: September 09, 2021, 01:50:47 PM »

There are many better antenna solutions - but are any of them available to you? If this is the best that you can implement, then yes, it's worth it! It will certainly work better than a dummy load...

Martin G8FXC
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K6SDW

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Re: End Fed Half Wave under concrete tile roof - should I bother?
« Reply #3 on: September 09, 2021, 02:19:43 PM »

As the new QST technical columnist (KE0OG) often says, everything affects everything. I live in an RV community and highly controlled environment as regards to antennas so I use an endfed (9:1) dipole hidden as best as I can and with the SFI numbers going up I'm working the world at night running FT8. From many years of hamming phone operation would be very frustrating indeed, but hey, someone will hear ya! From FT8 I would suggest CW instead of SSB.

I've always been of the mind to put up the most efficient hf antenna I can and go for it. Heck, you're set up to work from a local park table using the G90 and a portable antenna. I've also had good success with a 40-10 meter mag loop antenna installed both inside and outside.

GL/73
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W1ITT

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Re: End Fed Half Wave under concrete tile roof - should I bother?
« Reply #4 on: September 09, 2021, 02:22:56 PM »

Why not give it a try?  How much effort is it to drag the open end of the EFHW under the rafters and give it a go?   I suspect that, if you are considering this, your other options are not better.  Twenty watts won't be any danger of setting the world on fire, but FT8 is known for being a weak signal mode.
Half a century ago when I was in a firetrap off-campus apartment I had few options to get on the air.  There was a red-green pair of wires coming into my apartment and going across the road to a pole and, as I couldn't afford a telephone anyway, I loaded them up with a homebrew tuner.  The antenna worked, not well, but it worked and I was on the air.  If half a loaf is better than nothing, I suppose the end slice on the loaf is OK if it's the best you can do.
James Clerk Maxwell is famous for his equations on wave theory.  However there was one principle that never made it into his notebook.   It is "RF gotta go somewhere".    And it will.  Let us know.
73 de Norm W1ITT
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K6AER

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Re: End Fed Half Wave under concrete tile roof - should I bother?
« Reply #5 on: September 09, 2021, 04:32:26 PM »

I live in an RV community and highly controlled environment as regards to antennas so I use an endfed (9:1) dipole hidden as best as I can and with the SFI numbers going up I'm working the world at night running FT8.


What is a 9:1 dipole? Do yo mean an End Fed Half Wave!
« Last Edit: September 09, 2021, 04:35:25 PM by K6AER »
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K0UA

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Re: End Fed Half Wave under concrete tile roof - should I bother?
« Reply #6 on: September 09, 2021, 04:43:24 PM »

I live in an RV community and highly controlled environment as regards to antennas so I use an endfed (9:1) dipole hidden as best as I can and with the SFI numbers going up I'm working the world at night running FT8.


What is a 9:1 dipole? Do yo mean an End Fed Half Wave!

Well, actually with a 9:1 transformer they are used to feed end fed random length wires. You MUST avoid 1/2 wave length on all frequencies as these will have impedances in the 2500 ohm range.
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73  James K0UA

K6SDW

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Re: End Fed Half Wave under concrete tile roof - should I bother?
« Reply #7 on: September 09, 2021, 05:20:52 PM »

For an excellent explanation on endfed dipoles, 9:1 vs 49:1 I refer you to KE0OG's website.

GL/73
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K6AER

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Re: End Fed Half Wave under concrete tile roof - should I bother?
« Reply #8 on: September 10, 2021, 01:08:45 AM »

A wire fed at the end is not a dipole.
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W1VT

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Re: End Fed Half Wave under concrete tile roof - should I bother?
« Reply #9 on: September 10, 2021, 08:15:09 AM »

Phone is a lot harder than FT8.  You can use FT8 to see if you get out really well or not.
If FT8 is hard you may need a better antenna.

I'd suggest an optimized single band antenna for operating phone.  Every little bit helps on HF voice.

Zak W1VT
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