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Author Topic: 160M Dipole 20 Feet Above ground  (Read 3794 times)
K0BT
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Posts: 181




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« Reply #15 on: February 03, 2013, 02:20:54 PM »

I am going to try the antenna.  I have enough W7FG ladder line to feed it, which should help minimize feedline losses. I'll post back in two or three weeks with the results.  I have to build PVC stand-offs to bring the ladder line over the parapet walls of my flat-roofed house, so this will take a bit longer than it would if I used coax.

I appreciate all of the comments. I learn a lot here.

Bob, K0BT
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W5LZ
Member

Posts: 477




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« Reply #16 on: February 08, 2013, 04:28:49 AM »

Very few people have a 160 meter dipole at anything close to the 'correct' height, almost all of them are fairly low.  Will it be useable?  To some unknown extent, sure.  Don't expect it to work well though.  You will also need to tune the thing, the 'formula' length probably won't be 'right'.  It'll certainly beat no antenna at all...
 - 'Doc
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N4JTE
Member

Posts: 1155




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« Reply #17 on: February 08, 2013, 06:27:37 PM »

Yep go for it, your gonna be 160 and 80 with a lotta wire in the air and that's what counts!
Bob
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W5WSS
Member

Posts: 1694




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« Reply #18 on: February 08, 2013, 07:01:09 PM »

Yes an inverted L pushing against two on top of ground radials will really change your coverage footprint out to longer range DX skywave.

The radial can be a single wire directly beneath the antenna wire both traveling in the same direction.

The antenna wire can slope upwards and away from the point of origin.
If you can route the far upward end of the wire along with a rope that dead ends back on the ground below a tree this simple system will surprise you.

Have fun 73
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K0ZN
Member

Posts: 1544




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« Reply #19 on: February 09, 2013, 03:38:00 PM »


Hi.

Just a thought:  Depending upon your line length, using true 600 ohm line to feed an antenna that has a feedpoint impedance of probably around 10 to 15 ohms
is going to result in an astronomical SWR on that line. 15 ohms to 600 is a huge mismatch and even with that line you may have moderate losses due to very high
SWR. Go ahead and try it, but if results are not good, I would change to a much lower impedance line....even 50 ohm coax is much close to the feedpoint impedance.
An SWR of 3 to 4 on coax at 1.8 Mhz is not all that big of a deal. Again, I would consider using a 50 to 12.5 balun at the feedpoint or even an UNUN in that ratio area
if the antenna is dedicated to monoband use on 160. It is a little expensive, but you could also feed it with two 50 ohm lines in parallel, resulting in a line impedance
that the tuner would see of around 25 ohms.

If you want to use that antenna on all bands, then, yes, the 600 ohm line is lilkely the way to go.  FYI, you could also make the feedline an electrical half wave
length and that will repeat the actual feedpoint impedance at the end of the transmission line, then you could try it with a balun or to a tuner directly. I did that
(made the transmission line 1/2 electrical wavelength long) with a 160 M dipole fed with ladderline and it worked very well and the tuner easily and efficiently matched the line as the apparent impedance the tuner saw on the end of the ladderline was reasonably close to 30 ohms or so which it easily matched.
I would recommend you do some experimenting to see if you can find the most efficient matching set up; just don't be surprised or disappointed if you have issues
trying to feed that antenna with 600 ohm line....you may have to go to a plan "B".

Bottomline:  A 160 M dipole that is 20 ft. off the ground is going to have a very low feedpoint impedance and you may have to work around that.

73,  K0ZN
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N3WAK
Member

Posts: 277




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« Reply #20 on: February 11, 2013, 06:10:26 AM »

I think that Dirty Harry was right.  "Do you feel lucky?" 

Through vast practical experience, and after researching the issue exhaustively in numerous antenna books (athough I confess I never learned how to use ENZEC), I have reached the conclusion that I am able to make more contacts on the low bands using a poor antenna than with no antenna at all.  Try as I might, I made zero contacts on 160 before I put up my "low" Inverted-L.  With no antenna, I couldn't even get the ARRL's WMN Award (Worked My Neighborhood), much less WAS.  (Although the band was always quiet, and I wasn't troubled by atmospheric or manmade noise--a real positive on medium wave.)  Then I put up my antenna.  What a difference!  Even though it is far less than ideal given its relatively short vertical height, I've had tons of fun with it. 

So, put up an antenna!  Maybe you'll be lucky too and have a bunch of fun on 160 meters!  I hope to see you there. 

73, Tony
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EI4KE
Member

Posts: 1




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« Reply #21 on: February 15, 2013, 02:08:13 PM »

I use a doublet dipole approx 120 ft each leg for all bands including 160m, it is 27 ft above ground and works well enough on the lower bands ie 80/40.

To work 160m I just join the two legs of the 450 ohm line to one terminal on the palstar atu, join the station earth to the other, no real dx. A bit deaf,,,like myself,,,

I worked 32 countries messing about in the cqww cw test. Yes it's a cloud warmer but I still worked most of Europe / Russia from sunny Ireland,,,,and on 200 watts....happy enough,,,

Work with what you have, I have ht cables "33000" volts above the property,,, I'm not going any higher,,,,cul..

Seamus GI4SZW / EI4KE
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WH7DX
Member

Posts: 1029




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« Reply #22 on: February 18, 2013, 10:28:46 AM »

Here's a story on a VERY successful low dipole ham.   Perhaps get a beverage or two in there?

http://vss.pl/lf/14.pdf

Bryan,
WH7DX

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