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Author Topic: An interesting indoor antenna  (Read 2007 times)
W5WSS
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Posts: 1783




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« on: December 12, 2012, 12:18:26 PM »

I built an interesting indoor antenna recently.

The antenna is asymmetrical but I use a wide range T-match manual tuner with an integral 1:1 current balun directly at the broken open gap directly feeding the two vertical halves

The antenna is physically vertical about 16ft broken open and fed off center where 10ft downwards toward the earth and 6ft upwards toward the ceiling.

The topmost vertical part consists of two wiresthat are shorted together at the top connecting that have been expanded to form a square 15ft X15ft shape capacity hat then they are twisted together when returning downwards towards the tuner where they terminate and connect I have crimped and soldered ring terminals attaching both ends to the remaining balanced tuner terminal.

There is NO feedline.

The bottom vertical wire ends about 5ft above earth.
The feedpoint height is about 15ft above Earth surface.
The tip of the pair shorted and then connects to the hat is about 21ft. up.

The antenna looks like an off center fed vertical doublet with a twisted pair forming the top vertical that taps a 15ft X 15ft top hat.

The antenna is working from a frequency range of 20m-10m.

A Asymmetrical vertical doublet with no feedline and a capacity hat on the ceiling
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K3VAT
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« Reply #1 on: December 12, 2012, 12:41:13 PM »

I built an interesting indoor antenna recently.

The antenna is asymmetrical but I use a wide range T-match manual tuner with an integral 1:1 current balun directly at the broken open gap directly feeding the two vertical halves

The antenna is physically vertical about 16ft broken open and fed off center where 10ft downwards toward the earth and 6ft upwards toward the ceiling.

The topmost vertical part consists of two wiresthat are shorted together at the top connecting that have been expanded to form a square 15ft X15ft shape capacity hat then they are twisted together when returning downwards towards the tuner where they terminate and connect I have crimped and soldered ring terminals attaching both ends to the remaining balanced tuner terminal.

There is NO feedline.

The bottom vertical wire ends about 5ft above earth.
The feedpoint height is about 15ft above Earth surface.
The tip of the pair shorted and then connects to the hat is about 21ft. up.

The antenna looks like an off center fed vertical doublet with a twisted pair forming the top vertical that taps a 15ft X 15ft top hat.

The antenna is working from a frequency range of 20m-10m.

A Asymmetrical vertical doublet with no feedline and a capacity hat on the ceiling

Thanks Bob, sounds like an interesting arrangement!

So is this antenna in one room?

Actually you do have a feedline (from what I can gather reading the above) - it goes from the rig to the T match manual tuner.  Of course it doesn't have to be very long ... matching (or tuning) the antenna at the feedpoint is one way to reduce feedline loss due to mismatch.  One still needs to go from the matching device to the transmitter.

What's the resonant frequency of this antenna?  Work any interesting stations?

73, Rich, K3VAT
« Last Edit: December 12, 2012, 12:47:05 PM by K3VAT » Logged
W5WSS
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« Reply #2 on: December 13, 2012, 06:48:08 AM »

Thanks, The antenna is vertical there is no feedline because the tuner is connected directly at the junction or  broke open" point..

Yes working allot with excellent signal reports.

I just built it yesterday and am enjoying very gratifying results.

The system can be viewed in three parts:

Top hat 15ft X 15ft. A square horizontal loop on the ceiling made of wire.

A 16ft vertical Dipole broken open at the 10ft to 6ft point forming two halves

A wide range manual T-Match with an integrated !:! ratio current balun.

The top 6ft section consists of two 6ft length wires twisted together yes it WAS a feedline for a different indoor antenna.now it is pair of wires that are soldered together both at the top and bottom.

It is hard to write a description for a visual .

I am listening to 9a290a (Emil 9a9a) now on 15m.
his signal indoors is very strong.

I have been experimenting with indoor arrangements for 10yrs and this is a better performer.

I press it into multi band service marginal on 20m gets progressively better as move upwards in HF to 10m'

Yes the rig is next to the tuner on the desk and I will relocate the equipment soon.



 

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W5WSS
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« Reply #3 on: December 13, 2012, 06:54:18 AM »

Oh yes I realise afterwards.

The jumper 3ft coaxial cable from the rig to the tuner is not considered a feedline.
The jumper from the rig to the tuner is in the matched zone
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W5WSS
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« Reply #4 on: December 13, 2012, 12:22:23 PM »

Today I did some receive/transmit comparing.The new vertical dipole indoor antenna to an optimised resonant dipole antenna a 15m 1/2 wave horizontal dipole that is 21 ft above poor earth below.and also indoors oriented towards Europe.This dipole is installed and anchored to the ceiling.

The objective: To build an indoor antenna that is useful for DX skywave service.

The premise: Can a horizontal indoor dipole antenna rival an indoor vertical dipole that has also been optimised and both being the same physical height,while listening via skywave on 15m?

Rapid a/b switching methodology.

The dx signals were consistently nonexistent on the horizontal radiating horizontal oriented dipole pointed to favor Eu.

The signals received on the vertical indoor antenna were quite strong plentiful and transmit reports to Eu stations were S-9 and better.

A crude test indeed whether One can ever evaluate two Asymmetrical indoor antennas well enough to predict their respective patterns of either is remarkably difficult but alas is enjoyable.

Preliminary report is advantage vertical dipole.
 
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AA4PB
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« Reply #5 on: December 13, 2012, 12:48:43 PM »

Just curious - what was the noise level difference in the two antennas? If the noise is the same then no copy to S9 gives the vertical something in excess to 50dB gain over the horizontal - which is quite a lot. I wonder if something else is going on like the horizontal being detuned by coupling into horizontal wiring in the attic, etc.
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W5WSS
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« Reply #6 on: December 13, 2012, 01:34:48 PM »

Aa4pb hello, Yeah probably allot of mutual coupling to other conductors etc.

While either antenna is by most part Asymmetrical as a function of conductor proximity and coupling etc. today's results were remarkable on 15m.

Noise ingress as a function of asymmetry at this qth is reasonable and I make no assumptions as to the common mode potential differences at either antenna terminals to tuner terminals.

The two antennas are isolated meaning self contained but when 1 is connected to shielding common Power supply to rig to tuner via the coaxial shield there exists a potential common mode path as opposed to a differential path.

Because

The equipment is floating with 1 exception that the rig external power supply uses a three prong plug and can be driving an ac circuit relative to RF and the unknown power grid of this building.

Otherwise the noise floor relative to either antenna sampled during rapid a/b switching is similar.

The DX signals were dramatically apart between the two.

The proximity mutual coupling of electrical wiring ducting etc can be somewhat overcome

IF

a lucky combination can be found.

The vertical dipole seems" to be better today




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LA9XSA
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« Reply #7 on: December 13, 2012, 01:40:31 PM »

The jumper 3ft coaxial cable from the rig to the tuner is not considered a feedline.
Isn't it?
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W5WSS
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Posts: 1783




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« Reply #8 on: December 13, 2012, 01:56:32 PM »

Isn't it? No a feedline is between the last equipment and the antenna.terminals.

My intended meaning as stated "no feedline" was meant to imply that the tuner and 1:1 current balun are located "at the antenna" feed point therby eliminating the  antenna feedline that is found traveling after the tuner in an unmatched state.to the antenna.

As opposed to a matched 3ft coaxial jumper serving as a link between the rig and the tuner.

Perhaps I can be more clear to state that there exists no feedline between the tuner ,balun and the antenna.
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KC4MOP
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« Reply #9 on: December 13, 2012, 04:22:42 PM »

Do you have a photobucket account to share some pics? It is totally baffling somewhat to picture in my mind what you have here. Might be interesting for cliff dwellers....Apartment types

Fred
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W5WSS
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Posts: 1783




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« Reply #10 on: December 13, 2012, 05:41:36 PM »

Hello Fred, Perhaps some day a photobucket account.

A 15ft x 15ft horizontal square loop serving as a top hat is mounted at the ceiling junction to wall.

Two wires are co joined twisted and soldered to the top hat located just above the tuner.dropped straight down and connected together to the hot lead terminal of a balanced T-match and integrated 1:1 current balun that is tabletop.

The two wires are just joined together top and bottom connecting the hat to the tuner.
The two wires are#14 insulated wire,and 6ft in length.and serves as the top hat and 6ft vertical half.

The bottom wire is connected to the other balanced terminal and then drops straight down and ends about 5ft above ground.

The total length of the two halves is 16ft with the top hat added at the top.

Looks like a square with a vertical drop to the tuner.and a second vertical drop to near ground.

No coax or balanced line between the tuner and the off center feed point
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W5WSS
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« Reply #11 on: December 14, 2012, 06:13:04 AM »

The antenna could be top loaded with a resonator inserted inbetween the vertical tip and the top hat.

This would perk up the performance on the lower bands some.

Mulling over some figures to decide what to fabricate.

I have a series of Hustler resonators hmmm.
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