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Author Topic: Hidden antenna options ?  (Read 34167 times)
VE3FMC
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Posts: 982


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« Reply #30 on: January 09, 2013, 04:47:32 PM »

Quote from: VE3FMC

If that is the case why is all of the antenna wire listed at Wireman copper coated steel wire? Yes the copper coating may be thicker, that could be the only difference.



True CopperClad(R) wire as is used for antennas is 30% copper.  MIG may be
about 0.05% to 0.30% copper by weight (thinner gives better results.)  So there
is a difference of 100 : 1 or more in the coating thickness.

For a 1mm wire, the thickness would be about 60um for copper clad vs. 0.6um
maximum for copper plated (and perhaps 0.1 microns for the better quality
MIG wire - that's 1000 Angstroms, or roughly 400 atoms thick.)


Another important difference is the skin depth at the frequency of operation.
The types of 450 ohm twinlead using CopperClad(r) wire have higher losses on
160m than regular copper because the copper isn't thick enough to keep the
RF currents out of the lossier steel core.  (Magnetic materials have hysteresis
losses at RF because the magnetic field can't switch as fast.)  A thinner copper
coating will have higher losses, especially at higher frequencies where the
depth of the copper is no longer less than the skin depth.


Not that you can't try it out if you already have the wire - it may still work.
But even in a sheltered location I would expect the losses to be higher for
the MIG wire due to the skin depth. This particularly becomes an issue when
antennas are smaller than full-sized, because of the increased currents.
Your 15' x 18' loop may be OK on 20m and higher frequencies, but pressing
it into service on 40m will cause high currents and I think the losses will
increase significantly.

But try it and see.

Thanks for the information Dale.
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SV1ENS
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Posts: 124


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« Reply #31 on: January 09, 2013, 06:06:01 PM »

Back to the store the wire goes, it's a good thing returning stuff in Canada is really easy...

Anyway, I located proper antenna copper wire, a little expensive, but real copper :-)

Thanks for the info

73
Demetre - VE3/SV1ENS

Quote from: VE3FMC

If that is the case why is all of the antenna wire listed at Wireman copper coated steel wire? Yes the copper coating may be thicker, that could be the only difference.



True CopperClad(R) wire as is used for antennas is 30% copper.  MIG may be
about 0.05% to 0.30% copper by weight (thinner gives better results.)  So there
is a difference of 100 : 1 or more in the coating thickness.

For a 1mm wire, the thickness would be about 60um for copper clad vs. 0.6um
maximum for copper plated (and perhaps 0.1 microns for the better quality
MIG wire - that's 1000 Angstroms, or roughly 400 atoms thick.)


Another important difference is the skin depth at the frequency of operation.
The types of 450 ohm twinlead using CopperClad(r) wire have higher losses on
160m than regular copper because the copper isn't thick enough to keep the
RF currents out of the lossier steel core.  (Magnetic materials have hysteresis
losses at RF because the magnetic field can't switch as fast.)  A thinner copper
coating will have higher losses, especially at higher frequencies where the
depth of the copper is no longer less than the skin depth.


Not that you can't try it out if you already have the wire - it may still work.
But even in a sheltered location I would expect the losses to be higher for
the MIG wire due to the skin depth. This particularly becomes an issue when
antennas are smaller than full-sized, because of the increased currents.
Your 15' x 18' loop may be OK on 20m and higher frequencies, but pressing
it into service on 40m will cause high currents and I think the losses will
increase significantly.

But try it and see.
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WB2RCB
Member

Posts: 6




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« Reply #32 on: January 10, 2013, 05:07:29 AM »

I recently installed a High-Sierra HS-1500 Screwdriver in the crawl space of our condo here in Ft. Myers Florida. Added 3 quarter wave radials each for 40, 15 & 10 meters. While not a directional antenna, I have worked many European and stateside stations with great success on 10 & 15 meters.

The antenna itself fully extended with a 6 ft whip is 10.5 feet in length. You can see the installation at my website (www.wb2rcb.com) Use the 1965-2012 tab at the bottom of the page and scroll to the bottom.

Using a system such as this, you should have a fairly efficient antenna on 40 thru 10 meters.
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WD4ELG
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Posts: 860




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« Reply #33 on: January 10, 2013, 09:33:22 AM »

WB2RCB, that's awesome.  I was looking for some ideas if we get a condo.  (And we were just in Fort Myers this past weekend, what a wonderful couple of days of weather!)
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ONAIR
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Posts: 1732




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« Reply #34 on: January 11, 2013, 08:21:54 PM »

WB2RCB, great antenna setup for a condo!  Your web page was a wonderful half century time machine into the past.
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SV1ENS
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Posts: 124


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« Reply #35 on: January 14, 2013, 02:06:17 PM »

While having decided to go with a horizontal loop once I get the chance to work outdoors (the wet weather and the local electric company working to fix a cable problem In my back yard has delayed my plans considerably), I came up with this interesting project:

http://www.zerobeat.net/g3ycc/squalo.htm

Although the loop being a much superior antenna to the dipole, I'll give this one a try also, just so I can have a comparison data...

BTW How far apart would be good to keep the two antenna wires if they are to share the same fence area ??

73
Demetre - VE3/SV1ENS
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WB6BYU
Member

Posts: 12974




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« Reply #36 on: January 24, 2013, 10:47:57 AM »

That's the same principle as the Cobweb antenna:  a half wave dipole bent into
a square.  Feedpoint impedance is low, typically about 12 ohms, so the antenna
is often fed using a step-down transformer or by using a folded dipole for the
elements.

Here is one description of a multi-band design:
http://www.karinya.net/g3txq/cobweb/

Of course, the open half wave loop is just a full wave loop for twice the frequency
open at the far end, so if you put up a 40m loop you can remove a jumper at the
far end to make a half wave loop for 80m.  Because of the high voltage I wouldn't
use an ordinary switch at that point, but a couple feet of wire with banana plugs
or Anderson connectors should do the job, while allowing separate adjustment of
the wire length on both bands.

The performance is the same if you don't open the far end, because the geometry
is the same.  That puts the high impedance at the feedpoint, which can be difficult
to match in some cases, but might be easier if you can't reach the far corner
to open/short the wire when changing bands.

Because of the low impedance due to folding the antenna, ground losses are probably
going to be higher when the antenna is mounted at low heights than with a straight
dipole or a full wave loop.  I'll have to model it to quantify the difference.
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KB2FCV
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« Reply #37 on: January 24, 2013, 01:36:44 PM »

I would try the flagpole antenna and the outside look/dipole on the fence. You may find one may work better than the other depending on what band. I would save the indoor antenna as a last resort. Certainly explore the outdoor options first.
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WA6MJE
Member

Posts: 71




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« Reply #38 on: January 31, 2013, 08:51:47 PM »

I recently installed a High-Sierra HS-1500 Screwdriver in the crawl space of our condo here in Ft. Myers Florida. Added 3 quarter wave radials each for 40, 15 & 10 meters. While not a directional antenna, I have worked many European and stateside stations with great success on 10 & 15 meters.
I have also had great luck with a vertical screwdriver and elevated quarter wave radials either in my attic, or outside temporarily elevated at about six feet. A short vertical has very limited bandwidth, and the screwdriver allows me to adjust the antenna remotely to overcome this. I have tried many tricks to push the most out of it I can.  Actually I cut the radials to slightly less than quarter wave so that when I adjust the screwdriver, I am actually Off Center Fed (OCF) which helps match the impedance which starts off lower than 50 ohms at the center. Playing with the size of the radials slightly off of quarter wave can feed the antenna a point closer to 50 ohms, so I avoid a tuner. Check out the Hi-Q brand of screwdrivers as you may find their refinements make incremental differences in efficiency such as a Hi-Q coil. The bigger diameter of the coil is more efficient.  Having the coil higher than the bottom, (i.e. center fed) is more efficient than having it right at the bottom. Also the longer the whip the more efficient.  I have an 8.5 foot stainless whip at the minimum, and using Buddipole parts, I can add sections and have had as much as a 16 foot whip when I used it outside. Putting one section below the coil is one way of improving the location of the coil more toward the center. On lower bands experiment with a capacitive hat one or two feet above the coil. Hi-Q sells them, they look like stainless steel egg beaters. Capacitance to a short antenna adds efficiency.  In essence, the longest whip you can get away with, adding capacitance, using a Hi-Q coil that is 5" in diameter, placing the coil above the bottom feed point and elevated resonant radials will do the trick. These refinements add a small amount of efficiency, which then can make a difference in a needed contact that is marginal. Using these methods I am making the best out of a compromised situation, and have worked all over the world with it.  No one has ever seen it in my yard, or in my attic.

Rene - WA6MJE
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SV1ENS
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Posts: 124


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« Reply #39 on: February 15, 2013, 05:38:36 AM »

Back to the drawing board...  

A full 20meter loop was installed around the perimeter of my back yard fence, roughly 6 feet from the ground, a 4:1 ballon was used to bring the antenna in the house via RG8x coax. All was well until a chipmunk decided to have a
taste of the copper wire !!

A new chipmunk safe antenna design is required !

73
Demetre - VE3/SV1ENS
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K1WJ
Member

Posts: 450




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« Reply #40 on: February 15, 2013, 07:02:02 AM »

Try a MFJ-1979 17ft telescoping whip. Can adjust for 6m to 20m. A true 1/4 wave on band set up for. Retracts to two feet when not in use. Mine is set up at 17ft for 20m with a single elevated radial also cut 1/4 wave 20m, 4 feet off the ground. Works well.
Can see pics on QRZ under K1WJ, will also see 2m/440 Camo Ivy top j-pole, Vertical base in bucket with cement - wood dowel - Have 8 ferrite beads at antenna feedpoint.
Better than Buddi-this & Trans-that-,Screw-this,Trap-that.......
73 K1WJ David - (HOA COVERT OPS EXPERT) Grin
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WB6BYU
Member

Posts: 12974




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« Reply #41 on: February 15, 2013, 08:49:07 AM »

Quote from: SV1ENS

A full 20meter loop was installed around the perimeter of my back yard fence, roughly 6 feet from the ground, a 4:1 ballon was used to bring the antenna in the house via RG8x coax. All was well until a chipmunk decided to have a
taste of the copper wire !!



We're in the process of moving into a new house, and that is what I'm
considering for my first HF antenna:  a 40m loop around the eaves of the
house, possibly extended to 80m running along the wood fence.

But the neighbor feeds the local squirrels on top of the fence, so I'm
considering ways to discourage them.  Running the coax in flexible
electrical conduit would work, of course, but I'm also looking at
coatings for cables that will discourage them.  An ultrasonic rodent
repeller or recorded raptor cries are other possibilities.
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SV1ENS
Member

Posts: 124


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« Reply #42 on: February 15, 2013, 11:48:19 AM »

Ultrasonic pest repellers don't work, it's annoying to the them until they get used to it, and then back they come...

Untreated plastic is a delicacy to rodents, they will get though it eventually. Back when I was building a fiberoptic based wan for a University, the only thing that kept mice/rats away from the cables was a biter tasting gel that was added between the outside jacket and an internal armour, a little messy during termination, but really affective !

What were you thinking of using to coat the cables with ?

73



We're in the process of moving into a new house, and that is what I'm
considering for my first HF antenna:  a 40m loop around the eaves of the
house, possibly extended to 80m running along the wood fence.

But the neighbor feeds the local squirrels on top of the fence, so I'm
considering ways to discourage them.  Running the coax in flexible
electrical conduit would work, of course, but I'm also looking at
coatings for cables that will discourage them.  An ultrasonic rodent
repeller or recorded raptor cries are other possibilities.
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K1WJ
Member

Posts: 450




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« Reply #43 on: February 15, 2013, 11:58:52 AM »

How about coating the cables with Rat Poison......73 K1WJ
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SV1ENS
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Posts: 124


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« Reply #44 on: February 15, 2013, 12:13:43 PM »

How about coating the cables with Rat Poison......73 K1WJ

That would work, till it rained or till the neighbours cat/dog was unexplainably poisoned  Grin
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