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Author Topic: 160M Antennas in Limited Spaces  (Read 8557 times)
W3AGT
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« on: September 19, 2012, 03:41:50 AM »

I would really like to get into the 160M band but am severely, let me restate that, SEVERELY hampered by space restrictions on my city lot (40' width).

I am unable to use any antenna requiring radials.

I presently use a zero-five 10-40 aerial which has served me well.

Hanging wires from tree is pretty much out of the question.

Yard has to remain free for humans on orders from the XYL so slopers seem to be out of the question.

Homebrew or commercial solutions welcomed.

Is there any help/hope?

Thanks

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I am the King of My Castle When the Queen Lets Me
N3OX
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« Reply #1 on: September 19, 2012, 07:28:48 AM »

I am unable to use any antenna requiring radials.

Is this an independent constraint, or are you just concerned about not having enough space for a usable radial field?
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
K9IUQ
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Posts: 1626




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« Reply #2 on: September 19, 2012, 07:49:45 AM »

Is there any help/hope?

No. Unless you enjoy frustration find another band.

When I first got my license (many years ago  Wink  )  160 meters was used for local work in my area. Many hams used 160 meters in their car. The band was used much like 2 meters - local chit chat. Did mobile antennas work on 160 meters? Yes, but not very far distances.

I never did mobile as I was only 15 years old and did not have a car. I did get a BC-669 160/80 mtr AM (xtal controlled) transceiver (WW-II vintage) along with a 160 meter whip which I think had been mounted on a WW-II Jeep. At that time I did not know what radials were. I just ran a wire to the outside faucet for ground. I did make many many QSoes with this setup, proving that whip antennas will work on this band without radials. They just do not work very well.

http://www.radiomuseum.org/r/military_scr_543_bc_699.html

Stan K9IUQ
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W8JI
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« Reply #3 on: September 19, 2012, 08:08:00 AM »

Is there any help/hope?

Thanks



Not without radials or at least multiple ground rods.
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WX7G
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Posts: 5917




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« Reply #4 on: September 19, 2012, 10:56:09 AM »

Yes you can get on 160 meters. The ARRL contest is in early December and is a good introduction to top band.

As stated by the others without radials performance will suffer. But, you will still put out a useable signal.

DX Engineering has what you need. A Hustler 5BTV vertical with a DX Engineering Hot Rodz top hat. Here is what you need:

Huster 5BTV, $159.95
HRHUB-1P, hub, $27.50.
RODZ-72P, 72" spokes, $34.95

The radiation resistance of this 20', top loaded vertical is about 2.5 ohms. The RM-80S resonator adds 20 ohms of loss and with many 15-20' radials the ground loss can be 10 ohms. The radiation efficiency is then 2.5/(2.5+20+10) = 8%. With 100 watts in it will radiate 8 watts.

How about with no radials? With a ground rod (or several as Tom suggests) let's say the ground loss resistance is 50 ohms. Now the radiation efficiency is 2.5/(2.5+20+50) = 3.5%. With 100 watts in it will radiate 3.5 watts.

So, what can one do with 3.5 watts radiated on top band? I used to compete in the ARRL 160 meter contest in the QRP category running an antenna having a radiation efficiency of 25%. While my station was radiating only 1.25 watts I worked coast-to-coast and would make 200+ QSOs.

Without radials the 2:1 VSWR bandwidth of this antenna is roughly 30 kHz. With radials it is 10 kHz. For the ARRL and CQ contests you need to be able to work 100 kHz of the band. An antenna tuner at the shack will allow you to do this.

« Last Edit: September 19, 2012, 11:03:35 AM by WX7G » Logged
KC4MOP
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Posts: 729




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« Reply #5 on: September 19, 2012, 03:49:07 PM »

I have a PDF that I would share for an antenna 60 feet in length, but uses 120 feet of wire.
Has worked for the ham who designed it for many years.
eHam forums is severely limited to attach anything or paste any pictures in a reply.
I do not have a website or a photo-bucket for you to look in.
Apparently you are still new here and I cannot send a PM. Probably cannot attach anything there either.

OK here is the original link from a Ham forum AMFONE

http://amfone.net/Amforum/index.php?topic=22396.0

scroll down and look for a mini picture named MYANT.JPG Clik on it and save it to your computer, if interested.
It really works!!

Fred
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K0ZN
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« Reply #6 on: September 19, 2012, 06:49:49 PM »


"Yard has to remain free for humans on orders from the XYL so slopers seem to be out of the question."


  Seriously.... WHY ?   Does she spend a lot of time out in the back yard or do you entertain guests a lot??
  Seems to me there needs to be some give and take in this area. It is not like a piece of #18 wire is some huge eyesore.
  You don't need "cables" and towers !!  Worst case might be a piece of coax on the ground to the antenna base.
  If you can bury a few short radials and install some ground rods below the surface, you probably can bend something around
  to work. In this situation, you are probably going to have to homebrew. Some time with an older ARRL Antenna Book would be
time well spent.

  Unless she is paying the mortgage or owns the house in her name, I think I would head back to the negotiating table !!
  .....it ain't like you want to put a Utility substation back there.....

   Good luck!    73,  K0ZN
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WB6BYU
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« Reply #7 on: September 20, 2012, 12:44:56 PM »

A balloon or kite?
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WX7G
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Posts: 5917




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« Reply #8 on: September 20, 2012, 12:53:34 PM »

I've used balloon verticals several times on top band. They work well until the wind comes up but until then much fun is had by all.
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K3ANG
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Posts: 177




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« Reply #9 on: September 21, 2012, 09:11:54 PM »

Go to http://www.ekrs.co.uk/7.html
It's the projects page for the East Kent (UK) Radio Society.
Look for the project labeled COMPACT 160M ANTENNA.
It's a document with a picture of a 32-foot long dipole with two coils.
The coils have 140 turns on them but hang down and then another 8 feet below for tuning.
I haven't tried it, but it's on my list of antennas to try.
73
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W3AGT
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« Reply #10 on: September 22, 2012, 12:23:58 AM »

Many, Many Thanks for all the responses.

I appreciate all the advice except for the one challenging my wife for control of the back yard.

I'd rather do another tour in Vietnam before taking her on.
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I am the King of My Castle When the Queen Lets Me
W3AGT
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Posts: 31


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« Reply #11 on: September 22, 2012, 12:26:43 AM »


How about with no radials? With a ground rod (or several as Tom suggests) let's say the ground loss resistance is 50 ohms. Now the radiation efficiency is 2.5/(2.5+20+50) = 3.5%. With 100 watts in it will radiate 3.5 watts.

So, what can one do with 3.5 watts radiated on top band? I used to compete in the ARRL 160 meter contest in the QRP category running an antenna having a radiation efficiency of 25%. While my station was radiating only 1.25 watts I worked coast-to-coast and would make 200+ QSOs.

Without radials the 2:1 VSWR bandwidth of this antenna is roughly 30 kHz. With radials it is 10 kHz. For the ARRL and CQ contests you need to be able to work 100 kHz of the band. An antenna tuner at the shack will allow you to do this.

If 15' to 20' radials is all that is needed I may be able to pull that off.

How many ground rods do you think it would take to maximize radiation efficiency?

TIA

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I am the King of My Castle When the Queen Lets Me
WX7G
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Posts: 5917




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« Reply #12 on: September 22, 2012, 02:01:26 PM »

Yes many short radials will help considerably. I would use a single ground rod with this and it can be the support post for the antenna.

If this is mounted on a lawn I highly recommend the biodegradable plastic lawn staples from DX Engineering. I run #12 stranded THHN wire (green) radials and staple them to the lawn every 4'. I mow the lawn very short first. Then I don't mow for at least 2 weeks and set the mower on high. After a few months the radials seem to have sunk into the ground and cannot be seen. Amazing, at least to me.

Another way to put the 5BTV on top band is to attach a ~20' horizontal wire to the top of the RM-80 resonator. It works exactly like the top hat. It must be trimmed just as the Hot Rodz spokes must be adjusted.

I've run 600 watts into this and the Hot Rodz and the tips will exhibit corona and burn the ends. Other than that the RM-80 seems fine with it. Running the RM-80 and the top hat on a 12' mast at 600 watts I've worked some decent DX. It was radiating about 25 watts but that is enough to have plenty of fun on top band.
« Last Edit: September 22, 2012, 02:04:12 PM by WX7G » Logged
KG4WXP
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Posts: 165




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« Reply #13 on: September 24, 2012, 05:05:16 AM »

Many, Many Thanks for all the responses.

I appreciate all the advice except for the one challenging my wife for control of the back yard.

I'd rather do another tour in Vietnam before taking her on.

Backyard, eh? Tell her you're taking control of the FRONT yard, then. *eg*
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AD4U
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« Reply #14 on: September 24, 2012, 07:46:06 AM »

For all practical purposes radiating a really good signal on 160 meters requires a rather large antenna - period. 

That is not to say that you cannot make a contact on 160 here and there with a small antenna.  Heck, with the proper "tuner" you can load up a paper clip to a 1:1 SWR on 160.  Whether you radiate much of a signal or make many contacts is another matter.

Also a properly designed very small antenna for 160 usually receives much better than it transmits.  Take the tuned ferrite antenna inside most AM transistor radios as an example.  At night you can hear AM broadcast stations over 1000 miles away on a 4 inch long antenna.  But if you tried to transmit on such a small antenna, you would not be heard a mile away.

Try what others have suggested above.  If you do, accept your limitations up front so you do not get frustrated when many stations that you can hear do not respond to your call.

Dick  AD4U
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