40/80 meter antenna - Elmers Forum at eHam.net

$\'\'$

$\'\'$

$\'\'$

eHam.net Forum : Elmers : 40/80 meter antenna

Forum Help

1-7 of 7 messages

Page 1 of 1

40/80 meter antenna	Reply
by VK4TJF on May 24, 2009	Mail this to a friend!
I have a doublet feed with ladder line that is zip tied to my gutter and it works. However I was thinking of just wrapping it around the whole house and thus making it a loop. Now the height above ground is only say 10 feet. 1) will i make more contacts locally and with distant stations by making my doublet into a loop? 2) it will cost some money and effort to raise the loop to say 15 feet and having it off the gutter will doing this make more contacts both locally and with distant stations?

RE: 40/80 meter antenna	Reply
by G4AON on May 24, 2009	Mail this to a friend!
I wouldn't want to wrap an antenna around my house for two reasons (1) it will pick up spurious signals from every switched mode power supply in the house and (2) you will be operating in a strong RF field which isn't such a good idea. Assuming you can't install a mast and get the antenna away from the house, your next best option (at least for 40m) would be a ground mounted vertical. You would need radials with the vertical. A cheap fibreglass fishing pole with a wire taped to the side will work DX on 40m very easily, I have a 32 foot one here in the garden that is tied to a wooden fence post when I need to operate and is taken down afterwards. I have only installed 16 radials in the lawn, these are of various lengths and fit around a patio and some shrubs. 73 Dave

RE: 40/80 meter antenna	Reply
by W4VR on May 24, 2009	Mail this to a friend!
Before you do that calculate the RadHaz harm to your body and others living with you!

RE: 40/80 meter antenna	Reply
by WX7G on May 24, 2009	Mail this to a friend!
If the doublet is a half wavelength or nearly that length on the lowest band of operation it should work as well as the proposed loop. Raising the antenna to 15' from 10' will help your signal. I ran an EZNEC simulation of a 7 MHz dipole and at a take-off-angle of 10 degrees (DX) the higher dipole has 3 dB more signal.

RE: 40/80 meter antenna	Reply
by WX7G on May 24, 2009	Mail this to a friend!
RF levels in the house will most likey be well within FCC limits if you are running 100 watts or less. A check using one of the online calculators should be performed. RF is good for you and if you can't see it it can't hurt you, some say.

RE: 40/80 meter antenna	Reply
by WB6BYU on May 24, 2009	Mail this to a friend!
Try it and see. We don't all know your favorite bands, the size and shape of your roof, etc. I've had good luck in the past with loops around the roof or under the eaves, but they do work better with height. It shouldn't cost much to run the wire the rest of the way around the house. Make temporary connections at the ends so you can try it with and without the extra wire to see which works best for you. It may be that one works best on certain bands and paths but not on others. If you leave a metre or two of the added wire hanging down or folded back when you disconnect the ends it shouldn't affect the performance of the existing antenna.

RE: 40/80 meter antenna	Reply
by KB1LKR on May 24, 2009	Mail this to a friend!
Well FCC limits wouldn't officially apply down under (not sure what the Australian Communications and Media Authority's RF exposure rules are), but they remain a reasonable guideline all the same, see OET Bulletin 65 Supplement B at: http://www.fcc.gov/oet/info/documents/bulletins/#65 also here's a link to Univ of Texas Amateur Radio Club's RF safety calculator: http://hintlink.com/power_density.htm 17m - 15m thru 70cm are the bands where the issue is greatest, however the question addressed an 80m-40m antenna. Presumably you're running only a hundred watts or so (IC-718 your profile says)? Can you get the loop up a bit higher at the same time, maybe w/ fiberglass vertical supports at the corners -- that couldn't be a bad thing in the low bands.

Page 1 of 1

Next Topic: 161?
Previous Topic: echolink - signalink usb - ft817

Email Subscription
You are not subscribed to this topic.

Check our help page for help using Forum, or send questions, comments, or suggestions to the Forum Manager.

$\'\'$