Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Leroy Buller]

When I was in College at Kansas State, I had a random length long wire out
the window and up into some trees from the basement apartment.   I used a
simple coil and cap with alligator clips to make a LCD tuner on a piece of
pine.  What made it work was the copper pipe water inlet two feet from the
OP desk.  Good ground.   I worked 80 through 10 with my HW100.  No one
never saw the antenna in 5 years.  BS and Masters

Lee K0WA

On Tue, Jan 22, 2019, 2:57 PM Wayne Burdick  I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1
> antenna and a dragged counterpoise. In wide open spaces it’s a blast. But
> urban settings with dogs, wire-eating cacti and overzealous Neighborhood
> Watchers can distract from one’s radio experience.
>
> So, just for grins, I’d like to try something completely incognerdo: no
> visible antenna. A small remotely tuned loop (say 12” diameter) would seem
> to be the best choice, as it would fit entirely inside a small backpack. It
> could have  modest efficiency while not requiring a counterpoise wire.
> Rigid 1” copper pipe formed in a square would be convenient to deploy.
>
> The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP,
> of course.  OTOH, we’re talking about HF. A cellphone by your ear is
> probably worse.
>
> Any other antenna suggestions?
>
> Wayne
> N6KR
>
>
>
> 
> elecraft.com
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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[CUTTER DAVID via Elecraft]

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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[CUTTER DAVID via Elecraft]

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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Paul Wilton]

10+ years ago, we built a HF loop inside a coat.  I can’t really tell you the 
application but the loop was made of copper braid and put between the liner and 
the outer shell of the coat.  It was tuned with a simple L match with a LED to 
indicate peak power.  We operated it on the 80, 60 and 40m bands.  The drive 
was an FT817 at 5w.

We weren’t trying for DX but it worked well for the short distances we needed 
it to work.  It was also pretty easy to tune up and and once tuned stayed there.

73


Paul
M1CNK





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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Dave New, N8SBE]

> Here's another idea.
>
> Run a wire inside your shirt from one cuff across your back and down to
> the other cuff.  Wrap loading coils around each arm just above the
> elbow.  Feed the "dipole" in the center at the back of your neck.
>
> I did a quick model (assuming your arms are held straight out) with 5.5
> feet total length and 2200 inductive ohms for each coil, with each coil
> 30% from their respective ends of the wire.  It "resonates" at around
> 14.15 MHz, but with only about 0.4 ohms real feedpoint impedance.  I
> assume it would take some sort of extra matching network to bring that
> up enough that a KX2 with the internal tuner could drive it.
>
> Ignoring the effect of a person's arm, another quick calculation says
> that the arm coils would need to be roughly 11 turns of 10 gauge wire
> 3.5 inches in diameter ... unless I made a mistake, which is quite
> possible.
>
> It would bring new meaning to the term "compromise antenna", but I bet
> it would be more effective than a super small loop the size of backpack
> frame.
>
> 73,
> Dave  AB7E

Wouldn't that be a 'scarecrow' antenna?

73,

-- Dave, N8SBE


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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Dave New, N8SBE]

The loop would be only 6 to 8” from soft tissue, so you’d want to
run QRP, of course. OTOH, we’re talking about HF. A cellphone by your
ear is probably worse. 

Any other antenna suggestions?

Wayne
N6KR

Who was that guy at the HFPack get-together at HARA a few Daytons ago,
that was running A KILOWATT pedestrian mobile?  It he still on this
planet? :-)

73.

-- Dave, N8SBE
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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[K9FD]

Years back QST had an article that showed a home made 2 meter "filter" made
in a garbage can,   they ran low power and placed a hot dog inside,  
closed the lid

and applied RF,   the hot dog was BBQed in short order,
Perhaps with QRP one could put a sandwhich in one pocket and coffee in 
another

and while hiking to your destination you would have hot food and drink when
you arrived.
Not saying what may happen to the wienie of the person hiking. Your mileage
may vary as they say,  at least you wont have kids to tell the story to.

Merv K9FD

Up the power to 100 W and you’ve got a personal heating appliance. Awesome.

“Without RF, life itself would be impossible.”

Wayne



elecraft.com


On Jan 22, 2019, at 9:04 PM, David Gilbert  wrote:



Here's another idea.

Run a wire inside your shirt from one cuff across your back and down to the other cuff.  
Wrap loading coils around each arm just above the elbow.  Feed the "dipole" in 
the center at the back of your neck.

I did a quick model (assuming your arms are held straight out) with 5.5 feet total length 
and 2200 inductive ohms for each coil, with each coil 30% from their respective ends of 
the wire.  It "resonates" at around 14.15 MHz, but with only about 0.4 ohms 
real feedpoint impedance.  I assume it would take some sort of extra matching network to 
bring that up enough that a KX2 with the internal tuner could drive it.

Ignoring the effect of a person's arm, another quick calculation says that the 
arm coils would need to be roughly 11 turns of 10 gauge wire 3.5 inches in 
diameter ... unless I made a mistake, which is quite possible.

It would bring new meaning to the term "compromise antenna", but I bet it would 
be more effective than a super small loop the size of backpack frame.

73,
Dave  AB7E






On 1/22/19 12:57 PM, Wayne Burdick wrote:
I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1 antenna 
and a dragged counterpoise. In wide open spaces it’s a blast. But urban 
settings with dogs, wire-eating cacti and overzealous Neighborhood Watchers can 
distract from one’s radio experience.

So, just for grins, I’d like to try something completely incognerdo: no visible 
antenna. A small remotely tuned loop (say 12” diameter) would seem to be the 
best choice, as it would fit entirely inside a small backpack. It could have  
modest efficiency while not requiring a counterpoise wire. Rigid 1” copper pipe 
formed in a square would be convenient to deploy.

The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP, of 
course.  OTOH, we’re talking about HF. A cellphone by your ear is probably 
worse.

Any other antenna suggestions?

Wayne
N6KR

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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[kd4iz]

I love the AB7E concept... 

Looks an awful lot like birth of a new character for cosplay and a Comicon run 
to me: 
"EtherMan" - the RF belching steampunk simulacrum of an Isaac Asimov automaton! 
A little work with the 3D printer, an RPi with a 7" display, and some burnished 
10 gauge wire coil gauntlets, chest shield flip down mount for the KX2. Ah the 
possibilities! KA6LMS doesn't stand a chance. Anyone want to give it a go?

Seriously now, has anyone looked at the rf field issues - ie the effect created 
by the position of the person (a 70% water, protein gel matrix) with the 
backpack on?

KD4IZ
Jack Spitznagel
FM19oo




-Original Message-
From: David Gilbert  
Sent: Wednesday, January 23, 2019 00:04
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?



Here's another idea.

Run a wire inside your shirt from one cuff across your back and down to the 
other cuff.  Wrap loading coils around each arm just above the elbow.  Feed the 
"dipole" in the center at the back of your neck.

I did a quick model (assuming your arms are held straight out) with 5.5 feet 
total length and 2200 inductive ohms for each coil, with each coil 30% from 
their respective ends of the wire.  It "resonates" at around
14.15 MHz, but with only about 0.4 ohms real feedpoint impedance.  I assume it 
would take some sort of extra matching network to bring that up enough that a 
KX2 with the internal tuner could drive it.

Ignoring the effect of a person's arm, another quick calculation says that the 
arm coils would need to be roughly 11 turns of 10 gauge wire
3.5 inches in diameter ... unless I made a mistake, which is quite possible.

It would bring new meaning to the term "compromise antenna", but I bet it would 
be more effective than a super small loop the size of backpack frame.

73,
Dave  AB7E



>
>
> On 1/22/19 12:57 PM, Wayne Burdick wrote:
>> I’ve engaged in plenty of ultralight HF pack operation, with a KX2,
>> AX1 antenna and a dragged counterpoise. In wide open spaces it’s a 
>> blast. But urban settings with dogs, wire-eating cacti and 
>> overzealous Neighborhood Watchers can distract from one’s radio 
>> experience.
>>
>> So, just for grins, I’d like to try something completely incognerdo: 
>> no visible antenna. A small remotely tuned loop (say 12” diameter) 
>> would seem to be the best choice, as it would fit entirely inside a 
>> small backpack. It could have  modest efficiency while not requiring 
>> a counterpoise wire. Rigid 1” copper pipe formed in a square would be 
>> convenient to deploy.
>>
>> The loop would be only 6 to 8” from soft tissue, so you’d want to run 
>> QRP, of course.  OTOH, we’re talking about HF. A cellphone by your 
>> ear is probably worse.
>>
>> Any other antenna suggestions?
>>
>> Wayne
>> N6KR



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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Bill Steffey]

how about code to run a screwdriver antenna that is.

I use my k2 /kxpa100 in my VW   screwdriver up on the roof rack,.
woeks great  but could be elecraftmatic 

On 1/22/2019 10:56 PM, Wayne Burdick wrote:

Thanks for the amazing response and great ideas.

If someone wants to build a backpack loop antenna for 20 m sooner than I can, I 
promise to extensively field test it for you. If it works, it could become an 
Elecraft product. (AL1? :)

The KXIO2 option for the KX2 includes two open-drain outputs that could be used 
to slew a C-tuning motor up and down with suitable buffering. I’ll write the 
code for that if/when it’s needed.

Wayne
N6KR


elecraft.com


On Jan 22, 2019, at 7:43 PM, Bill Johnson  wrote:

The back pack frame would be the antenna?  Low power is the game.  I am not 
concerned. In the Vietnam era, I was in a station where we had ~5 10KW 
transmitters using wave guide at ~1.9Ghz and while there were very large 
dishes, the exposure was there.  I would never worry about HF at 10 watts close 
to my body, but there may be studies that dispute that.  I am still alive after 
12 months constant exposure to agent orange.  No problem.  What was I writing 
about? :_)

(Emoji added in case the sarcasm was missed.)

73,
Bill
K9YEQ

https://wrj-tech.com/

-Original Message-
From: elecraft-boun...@mailman.qth.net  On 
Behalf Of Wayne Burdick
Sent: Tuesday, January 22, 2019 2:57 PM
To: Elecraft 
Cc: KX3 
Subject: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1 antenna 
and a dragged counterpoise. In wide open spaces it’s a blast. But urban 
settings with dogs, wire-eating cacti and overzealous Neighborhood Watchers can 
distract from one’s radio experience.

So, just for grins, I’d like to try something completely incognerdo: no visible 
antenna. A small remotely tuned loop (say 12” diameter) would seem to be the 
best choice, as it would fit entirely inside a small backpack. It could have  
modest efficiency while not requiring a counterpoise wire. Rigid 1” copper pipe 
formed in a square would be convenient to deploy.

The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP, of 
course.  OTOH, we’re talking about HF. A cellphone by your ear is probably 
worse.

Any other antenna suggestions?

Wayne
N6KR




elecraft.com
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delivered to k9...@live.com

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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Martin Sole]

Hook it up to your KPA1500 and you've got whole house illumination!

Martin, HS0ZED



On 23/01/2019 13:11, Wayne Burdick wrote:

Up the power to 100 W and you’ve got a personal heating appliance. Awesome.

“Without RF, life itself would be impossible.”

Wayne



elecraft.com


On Jan 22, 2019, at 9:04 PM, David Gilbert  wrote:



Here's another idea.

Run a wire inside your shirt from one cuff across your back and down to the other cuff.  
Wrap loading coils around each arm just above the elbow.  Feed the "dipole" in 
the center at the back of your neck.

I did a quick model (assuming your arms are held straight out) with 5.5 feet total length 
and 2200 inductive ohms for each coil, with each coil 30% from their respective ends of 
the wire.  It "resonates" at around 14.15 MHz, but with only about 0.4 ohms 
real feedpoint impedance.  I assume it would take some sort of extra matching network to 
bring that up enough that a KX2 with the internal tuner could drive it.

Ignoring the effect of a person's arm, another quick calculation says that the 
arm coils would need to be roughly 11 turns of 10 gauge wire 3.5 inches in 
diameter ... unless I made a mistake, which is quite possible.

It would bring new meaning to the term "compromise antenna", but I bet it would 
be more effective than a super small loop the size of backpack frame.

73,
Dave  AB7E






On 1/22/19 12:57 PM, Wayne Burdick wrote:
I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1 antenna 
and a dragged counterpoise. In wide open spaces it’s a blast. But urban 
settings with dogs, wire-eating cacti and overzealous Neighborhood Watchers can 
distract from one’s radio experience.

So, just for grins, I’d like to try something completely incognerdo: no visible 
antenna. A small remotely tuned loop (say 12” diameter) would seem to be the 
best choice, as it would fit entirely inside a small backpack. It could have  
modest efficiency while not requiring a counterpoise wire. Rigid 1” copper pipe 
formed in a square would be convenient to deploy.

The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP, of 
course.  OTOH, we’re talking about HF. A cellphone by your ear is probably 
worse.

Any other antenna suggestions?

Wayne
N6KR

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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Wayne Burdick]

Up the power to 100 W and you’ve got a personal heating appliance. Awesome. 

“Without RF, life itself would be impossible.”

Wayne



elecraft.com

> On Jan 22, 2019, at 9:04 PM, David Gilbert  wrote:
> 
> 
> 
> Here's another idea.
> 
> Run a wire inside your shirt from one cuff across your back and down to the 
> other cuff.  Wrap loading coils around each arm just above the elbow.  Feed 
> the "dipole" in the center at the back of your neck.
> 
> I did a quick model (assuming your arms are held straight out) with 5.5 feet 
> total length and 2200 inductive ohms for each coil, with each coil 30% from 
> their respective ends of the wire.  It "resonates" at around 14.15 MHz, but 
> with only about 0.4 ohms real feedpoint impedance.  I assume it would take 
> some sort of extra matching network to bring that up enough that a KX2 with 
> the internal tuner could drive it.
> 
> Ignoring the effect of a person's arm, another quick calculation says that 
> the arm coils would need to be roughly 11 turns of 10 gauge wire 3.5 inches 
> in diameter ... unless I made a mistake, which is quite possible.
> 
> It would bring new meaning to the term "compromise antenna", but I bet it 
> would be more effective than a super small loop the size of backpack frame.
> 
> 73,
> Dave  AB7E
> 
> 
> 
>> 
>> 
>>> On 1/22/19 12:57 PM, Wayne Burdick wrote:
>>> I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1 
>>> antenna and a dragged counterpoise. In wide open spaces it’s a blast. But 
>>> urban settings with dogs, wire-eating cacti and overzealous Neighborhood 
>>> Watchers can distract from one’s radio experience.
>>> 
>>> So, just for grins, I’d like to try something completely incognerdo: no 
>>> visible antenna. A small remotely tuned loop (say 12” diameter) would seem 
>>> to be the best choice, as it would fit entirely inside a small backpack. It 
>>> could have  modest efficiency while not requiring a counterpoise wire. 
>>> Rigid 1” copper pipe formed in a square would be convenient to deploy.
>>> 
>>> The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP, 
>>> of course.  OTOH, we’re talking about HF. A cellphone by your ear is 
>>> probably worse.
>>> 
>>> Any other antenna suggestions?
>>> 
>>> Wayne
>>> N6KR
> 
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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[David Gilbert]

Here's another idea.

Run a wire inside your shirt from one cuff across your back and down to 
the other cuff.  Wrap loading coils around each arm just above the 
elbow.  Feed the "dipole" in the center at the back of your neck.


I did a quick model (assuming your arms are held straight out) with 5.5 
feet total length and 2200 inductive ohms for each coil, with each coil 
30% from their respective ends of the wire.  It "resonates" at around 
14.15 MHz, but with only about 0.4 ohms real feedpoint impedance.  I 
assume it would take some sort of extra matching network to bring that 
up enough that a KX2 with the internal tuner could drive it.


Ignoring the effect of a person's arm, another quick calculation says 
that the arm coils would need to be roughly 11 turns of 10 gauge wire 
3.5 inches in diameter ... unless I made a mistake, which is quite 
possible.


It would bring new meaning to the term "compromise antenna", but I bet 
it would be more effective than a super small loop the size of backpack 
frame.


73,
Dave  AB7E






On 1/22/19 12:57 PM, Wayne Burdick wrote:
I’ve engaged in plenty of ultralight HF pack operation, with a KX2, 
AX1 antenna and a dragged counterpoise. In wide open spaces it’s a 
blast. But urban settings with dogs, wire-eating cacti and 
overzealous Neighborhood Watchers can distract from one’s radio 
experience.


So, just for grins, I’d like to try something completely incognerdo: 
no visible antenna. A small remotely tuned loop (say 12” diameter) 
would seem to be the best choice, as it would fit entirely inside a 
small backpack. It could have  modest efficiency while not requiring 
a counterpoise wire. Rigid 1” copper pipe formed in a square would be 
convenient to deploy.


The loop would be only 6 to 8” from soft tissue, so you’d want to run 
QRP, of course.  OTOH, we’re talking about HF. A cellphone by your 
ear is probably worse.


Any other antenna suggestions?

Wayne
N6KR


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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Wayne Burdick]

Thanks for the amazing response and great ideas. 

If someone wants to build a backpack loop antenna for 20 m sooner than I can, I 
promise to extensively field test it for you. If it works, it could become an 
Elecraft product. (AL1? :)

The KXIO2 option for the KX2 includes two open-drain outputs that could be used 
to slew a C-tuning motor up and down with suitable buffering. I’ll write the 
code for that if/when it’s needed. 

Wayne
N6KR


elecraft.com

> On Jan 22, 2019, at 7:43 PM, Bill Johnson  wrote:
> 
> The back pack frame would be the antenna?  Low power is the game.  I am not 
> concerned. In the Vietnam era, I was in a station where we had ~5 10KW 
> transmitters using wave guide at ~1.9Ghz and while there were very large 
> dishes, the exposure was there.  I would never worry about HF at 10 watts 
> close to my body, but there may be studies that dispute that.  I am still 
> alive after 12 months constant exposure to agent orange.  No problem.  What 
> was I writing about? :_)  
> 
> (Emoji added in case the sarcasm was missed.)
> 
> 73,
> Bill
> K9YEQ
> 
> https://wrj-tech.com/
> 
> -Original Message-
> From: elecraft-boun...@mailman.qth.net  On 
> Behalf Of Wayne Burdick
> Sent: Tuesday, January 22, 2019 2:57 PM
> To: Elecraft 
> Cc: KX3 
> Subject: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?
> 
> I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1 
> antenna and a dragged counterpoise. In wide open spaces it’s a blast. But 
> urban settings with dogs, wire-eating cacti and overzealous Neighborhood 
> Watchers can distract from one’s radio experience. 
> 
> So, just for grins, I’d like to try something completely incognerdo: no 
> visible antenna. A small remotely tuned loop (say 12” diameter) would seem to 
> be the best choice, as it would fit entirely inside a small backpack. It 
> could have  modest efficiency while not requiring a counterpoise wire. Rigid 
> 1” copper pipe formed in a square would be convenient to deploy. 
> 
> The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP, of 
> course.  OTOH, we’re talking about HF. A cellphone by your ear is probably 
> worse. 
> 
> Any other antenna suggestions?
> 
> Wayne
> N6KR
> 
> 
> 
> 
> elecraft.com
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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Bill Johnson]

The back pack frame would be the antenna?  Low power is the game.  I am not 
concerned. In the Vietnam era, I was in a station where we had ~5 10KW 
transmitters using wave guide at ~1.9Ghz and while there were very large 
dishes, the exposure was there.  I would never worry about HF at 10 watts close 
to my body, but there may be studies that dispute that.  I am still alive after 
12 months constant exposure to agent orange.  No problem.  What was I writing 
about? :_)  

(Emoji added in case the sarcasm was missed.)

73,
Bill
K9YEQ

https://wrj-tech.com/

-Original Message-
From: elecraft-boun...@mailman.qth.net  On 
Behalf Of Wayne Burdick
Sent: Tuesday, January 22, 2019 2:57 PM
To: Elecraft 
Cc: KX3 
Subject: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1 antenna 
and a dragged counterpoise. In wide open spaces it’s a blast. But urban 
settings with dogs, wire-eating cacti and overzealous Neighborhood Watchers can 
distract from one’s radio experience. 

So, just for grins, I’d like to try something completely incognerdo: no visible 
antenna. A small remotely tuned loop (say 12” diameter) would seem to be the 
best choice, as it would fit entirely inside a small backpack. It could have  
modest efficiency while not requiring a counterpoise wire. Rigid 1” copper pipe 
formed in a square would be convenient to deploy. 

The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP, of 
course.  OTOH, we’re talking about HF. A cellphone by your ear is probably 
worse. 

Any other antenna suggestions?

Wayne
N6KR




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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop

[Phil Kane]

On 1/22/2019 6:03 PM, Edward R Cole wrote:

> "Shades of WWII spy movies" with the german's sniffing RF with rotating
> loops on top of a small van!

That system - called the Finch loop in the US - was used by most if not
all radio enforcement administrations world-wide in some version or
other until well into the 1970s.

73 de K2ASP - Phil Kane
Elecraft K2/100   s/n 5402

>From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop

[Edward R Cole]

"Shades of WWII spy movies" with the german's sniffing RF with 
rotating loops on top of a small van!


Great idea!  Better Rx antennas, of course.  I have plans to make a 6 
or 8 foot loop out of some old 1/2 inch heliax cable (1/2 inch copper 
shield) to try on 630m for Rx. One foot loop on 14-MHz is 
comparable.  And if anyone were to ask what you are doing: "just 
tracking deer or bengal tigers"!


73, Ed - KL7UW
  http://www.kl7uw.com
Dubus-NA Business mail:
  dubus...@gmail.com 


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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Michael Chowning]

Just for grins, look into this link, from Ohio State University from back in 
2011!
https://news.osu.edu/antennas-in-your-clothes--new-design-could-pave-the-way/ 

There are also articles more recently (2018) on electronics in one’s clothes, 
and computers in one’s clothes in this website’s news as well.
Mike, N8TTR

> On Jan 22, 2019, at 2:57 PM, Wayne Burdick  wrote:
> 
> I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1 
> antenna and a dragged counterpoise. In wide open spaces it’s a blast. But 
> urban settings with dogs, wire-eating cacti and overzealous Neighborhood 
> Watchers can distract from one’s radio experience. 
> 
> So, just for grins, I’d like to try something completely incognerdo: no 
> visible antenna. A small remotely tuned loop (say 12” diameter) would seem to 
> be the best choice, as it would fit entirely inside a small backpack. It 
> could have  modest efficiency while not requiring a counterpoise wire. Rigid 
> 1” copper pipe formed in a square would be convenient to deploy. 
> 
> The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP, of 
> course.  OTOH, we’re talking about HF. A cellphone by your ear is probably 
> worse. 
> 
> Any other antenna suggestions?
> 
> Wayne
> N6KR
> 
> 
> 
> 
> elecraft.com
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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[kevinr]

There may be other options.  A serpentine pattern fed at the center 
could give you enough length for a 10 m or larger dipole. I've seen 
serpentine F antennas on printed circuit boards.  I've also seen spiral 
patterns used so I know they work to some extent.


If a dipole cut for 14 MHz is ~ 400 inches long it would take 11 up and 
down segments of 36" each to stuff it inside your pack. I'm sure the 
serpentine factor will change the length needed but with a bit of 
tweaking this could work.


Or feed it at one end for a 40 meter monopole (a counterpoise could be 
woven into the pack).


   73 & GL,

   Kevin.  KD5ONS

-


On 1/22/19 12:57 PM, Wayne Burdick wrote:

I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1 antenna 
and a dragged counterpoise. In wide open spaces it’s a blast. But urban 
settings with dogs, wire-eating cacti and overzealous Neighborhood Watchers can 
distract from one’s radio experience.

So, just for grins, I’d like to try something completely incognerdo: no visible 
antenna. A small remotely tuned loop (say 12” diameter) would seem to be the 
best choice, as it would fit entirely inside a small backpack. It could have  
modest efficiency while not requiring a counterpoise wire. Rigid 1” copper pipe 
formed in a square would be convenient to deploy.

The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP, of 
course.  OTOH, we’re talking about HF. A cellphone by your ear is probably 
worse.

Any other antenna suggestions?

Wayne
N6KR




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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[turnbull]

Why not a collapsible Alexloop mag loop which fits in your back pack and will 
be nore efficient.    73 Doug EI2CN


Sent from my Samsung Galaxy smartphone.
 Original message From: Grant Youngman  
Date: 22/01/2019  22:09  (GMT+00:00) To: K9MA  Cc: 
elecraft@mailman.qth.net Subject: Re: [Elecraft] Urban stealth HF: 
Inside-the-backpack loop antenna? 
Yes, it does not have to be round.  The actual measurement of interest is 
Circumference of whatever shape it is (e.g, the total length of the radiator).  
A 12” loop or square, or whatever,  is still going to have a very low 
efficiency at this size point.  But closer to rounder is better … 

Grant NQ5T
K3 #2091 KX3 #8342

> On Jan 22, 2019, at 4:51 PM, K9MA  wrote:
> 
> On 1/22/2019 15:46, Grant Youngman wrote:
>> The problem is loop diameter.
> 
> It doesn't have to be round.
> 
> 73,
> 
> Scott K9MA
> 
> 
> -- 

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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[K9MA]

There's undoubtedly a trade-off between rounder and longer. I was 
thinking of a typical more or less rectangular backpack, which would 
have a circumference much larger than a 12 inch circle. A typical 
backpacking pack could accommodate a circumference of about 88 inches, 
more than twice that of a 12 inch round loop. Granted, such a large pack 
wouldn't exactly be inconspicuous on an urban hiking trail, but you 
could always put some rocks in it, and pretend you're training for a 
Grand Canyon hike.


73,
Scott K9MA

On 1/22/2019 16:09, Grant Youngman wrote:
Yes, it does not have to be round.  The actual measurement of interest 
is Circumference of whatever shape it is (e.g, the total length of the 
radiator).  A 12” loop or square, or whatever,  is still going to have 
a very low efficiency at this size point.  But closer to rounder is 
better …


Grant NQ5T
K3 #2091 KX3 #8342

On Jan 22, 2019, at 4:51 PM, K9MA > wrote:


On 1/22/2019 15:46, Grant Youngman wrote:

The problem is loop diameter.


It doesn't have to be round.

73,

Scott K9MA


--




--
Scott  K9MA

k...@sdellington.us

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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Grant Youngman]

Yes, it does not have to be round.  The actual measurement of interest is 
Circumference of whatever shape it is (e.g, the total length of the radiator).  
A 12” loop or square, or whatever,  is still going to have a very low 
efficiency at this size point.  But closer to rounder is better … 

Grant NQ5T
K3 #2091 KX3 #8342

> On Jan 22, 2019, at 4:51 PM, K9MA  wrote:
> 
> On 1/22/2019 15:46, Grant Youngman wrote:
>> The problem is loop diameter.
> 
> It doesn't have to be round.
> 
> 73,
> 
> Scott K9MA
> 
> 
> -- 

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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Clay Autery]

Consider integrating the loop into a purpose built/modified backpack...  or the 
frame.
You can get a larger enclosed area, maintain easier use of the pack's volume 
without jacking up the loop, and better insure the loop geometry doesn't change 
as you pack/move/use it.
With a little creativity, yiu could also integrate some variable tuning into 
the design with access by hand if you place the adjusrable parts in the right 
location...
If you do switch in/out parts, it could be just a switch setup on the torso 
strap...
If QRP, I'd try to use the frame or an extension thereof...
Even the flexible plastic stiffeners in some frames could be used to carry a 
loop wire.
Good luck!
73,
ClayKY5G


Sent from my Verizon, Samsung Galaxy smartphone
 Original message From: Wayne Burdick  Date: 
1/22/19  14:57  (GMT-06:00) To: Elecraft  Cc: KX3 
 Subject: [Elecraft] Urban stealth HF: 
Inside-the-backpack loop antenna? 
I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1 antenna 
and a dragged counterpoise. In wide open spaces it’s a blast. But urban 
settings with dogs, wire-eating cacti and overzealous Neighborhood Watchers can 
distract from one’s radio experience. 

So, just for grins, I’d like to try something completely incognerdo: no visible 
antenna. A small remotely tuned loop (say 12” diameter) would seem to be the 
best choice, as it would fit entirely inside a small backpack. It could have  
modest efficiency while not requiring a counterpoise wire. Rigid 1” copper pipe 
formed in a square would be convenient to deploy. 

The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP, of 
course.  OTOH, we’re talking about HF. A cellphone by your ear is probably 
worse. 

Any other antenna suggestions?

Wayne
N6KR




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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[K9MA]

On 1/22/2019 15:46, Grant Youngman wrote:

The problem is loop diameter.


It doesn't have to be round.

73,

Scott K9MA


--
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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Grant Youngman]

The problem is loop diameter.  Efficiency on 20m of a 12” diameter loop would 
be on the order of 5%. Forget it entirely on 40m .. essentially a dummy load 
that would take around 1200 pf to resonate. On 17m efficiency would go up to 
around 11%. 

I use a loop portable all the time (Alexloop, W4OP) and they work well. They’re 
both about 3 ft in diameter. The Alexloop is light enough to be carried around 
hand held ... the W4OP needs a table top or tripod. 

Grant NQ5T

Sent from my iPhone

> On Jan 22, 2019, at 3:57 PM, Wayne Burdick  wrote:
> 
> 
> 
> So, just for grins, I’d like to try something completely incognerdo: no 
> visible antenna. A small remotely tuned loop (say 12” diameter) would seem to 
> be the best choice, as it would fit entirely inside a small backpack. It 
> could have  modest efficiency while not requiring a counterpoise wire. Rigid 
> 1” copper pipe formed in a square would be convenient to deploy. 
> 
> The loop would be only 6 to 8” from soft tissue, so you’d want to run QRP, of 
> course.  OTOH, we’re talking about HF. A cellphone by your ear is probably 
> worse. 
> 
> Any other antenna suggestions?
> 
> Wayne
> 
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Re: [Elecraft] Urban stealth HF: Inside-the-backpack loop antenna?

[Steve Sergeant]

On 1/22/19 12:57 PM, Wayne Burdick wrote:
>  A small remotely tuned loop (say 12” diameter) would seem to be the best 
> choice, as it would fit entirely inside a small backpack. It could have  
> modest efficiency while not requiring a counterpoise wire. Rigid 1” copper 
> pipe formed in a square would be convenient to deploy. 

[Deletia]

> Any other antenna suggestions?

I tried a 52ft 26ga wire J-pole/Zep on the line of a 5ft parafoil kite,
with 50ft of kite line above the antenna, and another 50' of RG-174
between the antenna and the radio.

I'll grant that this is not as invisible as your idea. But I felt
reasonably inconspicuous working SSB with cell-phone type earbuds
(w/mic), and the KX2 in an open waist-pack, out in an open field of a
large city park. People just thought I was on a phone call while flying
the kite. It helped that there were several other kite-fliers in the
park that day.

It was not a particularly good day for propagation, but I did work Las
Vegas and Spokane from Silicon Valley with under 10W on 20m.


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