Re: [Elecraft] (OT redoux) MAG LOOP ANTENNAS

[Jean-François Ménard]

Hi,

I already used the Alexloop inside my house a few years ago. I was using at 
that time a FT-897D running at 5W on battery on 20m…. And I did many contacts 
using PSK31 and JT-65. I was really fun to see how it was possible to even do 
contacts inside the house…. At least, to experiment mode without going outside 
during the winter season. Hi Hii ‼️

73 de Jeff | VA2SS

__
Jeff | VA2SS
Jean-François Ménard

jean-francois.men...@va2ss.com
www.VA2SS.com

Membre de / Member of :
ARRL / AMSAT / QRP ARCI / FISTS / SKCC / MICHIGAN QRP CLUB

Message envoyé à partir de mon appareil mobile.
Message sent from my portable device.

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Re: [Elecraft] (OT redoux) MAG LOOP ANTENNAS

[Fred Jensen]

Many years ago, when computers filled buildings, consumed a megawatt or 
two, and the IBM CEO forecast a world-wide market for them of maybe six, 
ten tops ... automatic antenna matching, particularly in HF mobile 
environments, was sometimes achieved by sampling the voltage and current 
at the feed point and driving a motor on the matching unit's capacitor 
shaft to make the phase difference zero [i.e. resonance].  Should be 
able to do that with a mag loop today in a much smaller package.


I do wish Alex had put a 10:1 drive on the capacitor shaft however.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 1/23/2017 11:16 AM, kevino z wrote:

I just wish Alex would release the motor to control the tuning...
-Kevin (KK4YEL)


-
The problem with the world is that the intelligent people are full of 
doubts, while the stupid ones are full of confidence.


On Jan 23, 2017, at 14:13, Fred Jensen > wrote:


Good to know.  I've never tried my Alexloop inside the house, but for 
an all-round portable antenna it meets the requirements of size, ease 
of set-up/take-down, and working well at QRP-ish power levels.  The 
tuning problem is mitigated by the fact that I usually sit directly 
under it when it's mounted on the tripod and I can just reach up and 
adjust it.


73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County


On 1/23/2017 5:21 AM, Doug Turnbull wrote:

Fred,
Well put and useful.I can though testify that the AlexLoop 
can work
amazingly well from inside a frame house and even a stone house as I 
have

tried this.


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Re: [Elecraft] (OT redoux) MAG LOOP ANTENNAS

[kevino z]

I just wish Alex would release the motor to control the tuning...
-Kevin (KK4YEL)


-
The problem with the world is that the intelligent people are full of doubts, 
while the stupid ones are full of confidence.

On Jan 23, 2017, at 14:13, Fred Jensen 
> wrote:

Good to know.  I've never tried my Alexloop inside the house, but for an 
all-round portable antenna it meets the requirements of size, ease of 
set-up/take-down, and working well at QRP-ish power levels.  The tuning problem 
is mitigated by the fact that I usually sit directly under it when it's mounted 
on the tripod and I can just reach up and adjust it.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County


On 1/23/2017 5:21 AM, Doug Turnbull wrote:
Fred,
Well put and useful.I can though testify that the AlexLoop can work
amazingly well from inside a frame house and even a stone house as I have
tried this.

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Re: [Elecraft] (OT redoux) MAG LOOP ANTENNAS

[Fred Jensen]

Good to know.  I've never tried my Alexloop inside the house, but for an 
all-round portable antenna it meets the requirements of size, ease of 
set-up/take-down, and working well at QRP-ish power levels.  The tuning 
problem is mitigated by the fact that I usually sit directly under it 
when it's mounted on the tripod and I can just reach up and adjust it.


73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County


On 1/23/2017 5:21 AM, Doug Turnbull wrote:

Fred,
 Well put and useful.I can though testify that the AlexLoop can work
amazingly well from inside a frame house and even a stone house as I have
tried this.


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Re: [Elecraft] (OT redoux) MAG LOOP ANTENNAS

[Ron D'Eau Claire]

It doesn't directly address KC5WA's need (unless his retirement home is at
the beach) but a subterfuge I see used on the coast for people at vacation
rentals involve long surf-fishing poles. Some are 20 feet or more long so it
is common to see them propped up near vertical at the deck railing at
people's apartments when they are not in use. They are a very common sight
with nothing "Ham Antenna" about them, but a wire instead of fishing line
running up the length of the pole can be a very effective outdoor radiator. 

And if it's a fine wire that was cast from the pole into a nearby tree
extending its length for a full half wave on 40 or 80 meters, all the
better!   

The old phrase, "Necessity is the Mother of invention" comes to mind. After
all, trolling the Ham bands is just a different sort of "fishing". 

73, Ron AC7AC

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Vic
Rosenthal
Sent: Sunday, January 22, 2017 10:07 PM
To: Ron D'Eau Claire
Cc: Elecraft@mailman.qth.net
Subject: Re: [Elecraft] (OT redoux) MAG LOOP ANTENNAS

I agree with Ron that the best solution is wire outdoors. I too lived in
apartments and did similar things. Best results always seemed to come from
some sort of balanced antenna when possible. Nowadays there are so many
noise sources in buildings that getting a wire outside is worth the
struggle. Indoors, you are within the loop of the AC lines, Ethernet cables,
etc. Try to get out of the loop and use a balun to decouple the outside of
the feed line if it's coax.
Small wire like no. 20 enameled wire can be almost invisible from a few feet
away.
Another possibility is a temporary antenna. You can make a little stand for
a mag loop and place it outdoors to operate and then bring it inside when
you are done.
I have a little game I play whenever I visit a new place. I ask myself "how
would I put up an antenna if I lived here?" My wife is used to my walking
around looking at trees, etc.

Vic 4X6GP

> On 23 Jan 2017, at 02:49, Ron D'Eau Claire <r...@cobi.biz> wrote:
> 
> Over the years I've done a fair bit of operating from inside 
> apartments. My tactic was to get as much wire up as high as possible 
> while still being unobtrusive. I was running 10 watts or less, CW.
> 
> In one location I had a tree about 20 feet away from a window at my 
> operating desk. I slipped a fine wire out of the window (so I could 
> still close it) and hooked it to some fishing line leader which I then 
> tossed into the tree, succeeding in getting it about 20 feet above the 
> ground. It was not visible and survived some surprising winds. Worked 
> it against a counterpoise made from fine white wire held along the 
> (apartment white) wall with pushpins.
> 
> Where I had a 2nd (top) floor unit, I had good success with a thin 
> white wire 'doublet' tacked onto the wall near the ceiling with the 
> two halves running as nearly in opposite directions as possible I was 
> able to get about
> 50 feet of wire up that way and made a lot of contacts including some 
> DX. Of course being indoors brings you closer to all sources of noise 
> and, depending upon the construction of the building a certain amount 
> of "shielding".
> 
> One apartment building had a flat roof. The manager okayed me 
> installing a simple antenna on the roof. It never hurts to ask. In 
> another top floor location I discovered I had an attic access door in 
> one closet, so I installed a "doublet" in the attic just under the 
> roof rafters. Got a full half wave on 40 in that space with a bend in 
> each half. The "feeder" was open wire - thin white wires that passed 
> through two tiny holes in the ceiling next to the wall at my operating 
> position and down to the rig. It worked beautifully on 40 through 10 
> meters. On that one when I moved I never got into the attic space to 
> remove the antenna, insulators, etc. I just cut the feeder at the 
> ceiling and filled the tiny holes. Eventually someone needing to do 
> work in the attic probably scratched their head wondering what that was -
unless they were a Ham.
> 
> 73, Ron AC7AC
> 
> -Original Message-
> From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of 
> Robert 'RC' Conley
> Sent: Sunday, January 22, 2017 6:16 AM
> To: Elecraft@mailman.qth.net
> Subject: [Elecraft] (OT redoux) MAG LOOP ANTENNAS
> 
> Guys;
> I'm anticipating a move to a seniors villa and I know I will be unable 
> to to take my antenna farm and most of the ham shack. I've decided on 
> my KX2 with ATU (grab-n go). A MAG LOOP should allow indoor operations 
> at QRP power levels.Thanks for your thoughts.
> 73
> KC5WA
> 
> --
> May You Live Long and Prosper
> what's life without a few dr

Re: [Elecraft] (OT redoux) MAG LOOP ANTENNAS

[Vic Rosenthal]

I agree with Ron that the best solution is wire outdoors. I too lived in 
apartments and did similar things. Best results always seemed to come from some 
sort of balanced antenna when possible. Nowadays there are so many noise 
sources in buildings that getting a wire outside is worth the struggle. 
Indoors, you are within the loop of the AC lines, Ethernet cables, etc. Try to 
get out of the loop and use a balun to decouple the outside of the feed line if 
it's coax.
Small wire like no. 20 enameled wire can be almost invisible from a few feet 
away.
Another possibility is a temporary antenna. You can make a little stand for a 
mag loop and place it outdoors to operate and then bring it inside when you are 
done.
I have a little game I play whenever I visit a new place. I ask myself "how 
would I put up an antenna if I lived here?" My wife is used to my walking 
around looking at trees, etc.

Vic 4X6GP

> On 23 Jan 2017, at 02:49, Ron D'Eau Claire  wrote:
> 
> Over the years I've done a fair bit of operating from inside apartments. My
> tactic was to get as much wire up as high as possible while still being
> unobtrusive. I was running 10 watts or less, CW.  
> 
> In one location I had a tree about 20 feet away from a window at my
> operating desk. I slipped a fine wire out of the window (so I could still
> close it) and hooked it to some fishing line leader which I then tossed into
> the tree, succeeding in getting it about 20 feet above the ground. It was
> not visible and survived some surprising winds. Worked it against a
> counterpoise made from fine white wire held along the (apartment white) wall
> with pushpins. 
> 
> Where I had a 2nd (top) floor unit, I had good success with a thin white
> wire 'doublet' tacked onto the wall near the ceiling with the two halves
> running as nearly in opposite directions as possible I was able to get about
> 50 feet of wire up that way and made a lot of contacts including some DX. Of
> course being indoors brings you closer to all sources of noise and,
> depending upon the construction of the building a certain amount of
> "shielding". 
> 
> One apartment building had a flat roof. The manager okayed me installing a
> simple antenna on the roof. It never hurts to ask. In another top floor
> location I discovered I had an attic access door in one closet, so I
> installed a "doublet" in the attic just under the roof rafters. Got a full
> half wave on 40 in that space with a bend in each half. The "feeder" was
> open wire - thin white wires that passed through two tiny holes in the
> ceiling next to the wall at my operating position and down to the rig. It
> worked beautifully on 40 through 10 meters. On that one when I moved I never
> got into the attic space to remove the antenna, insulators, etc. I just cut
> the feeder at the ceiling and filled the tiny holes. Eventually someone
> needing to do work in the attic probably scratched their head wondering what
> that was - unless they were a Ham. 
> 
> 73, Ron AC7AC
> 
> -Original Message-
> From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Robert
> 'RC' Conley
> Sent: Sunday, January 22, 2017 6:16 AM
> To: Elecraft@mailman.qth.net
> Subject: [Elecraft] (OT redoux) MAG LOOP ANTENNAS
> 
> Guys;
> I'm anticipating a move to a seniors villa and I know I will be unable to to
> take my antenna farm and most of the ham shack. I've decided on my KX2 with
> ATU (grab-n go). A MAG LOOP should allow indoor operations at QRP power
> levels.Thanks for your thoughts.
> 73
> KC5WA
> 
> --
> May You Live Long and Prosper
> what's life without a few dragons
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Re: [Elecraft] (OT redoux) MAG LOOP ANTENNAS

[Fred Jensen]

I'm not sure about a mag loop inside a room, I've never tried mine that 
way.  When used vertically outside, they tend to be insensitive to 
surroundings [trees, ground, you sitting under it] because the 
permeability of most such surroundings is 1.  This may not be true if 
you're set up on the track of a railroad yard ... or if there's a lot of 
ferromagnetic material in your walls.


If you try it, be aware of several things:

1.  Small magnetic loops involve some very high voltages and circulating 
currents, even at surprisingly low powers.  AA5TB has an on-line 
calculator and there is a similar one at 
http://www.66pacific.com/calculators/small_tx_loop_calc.aspx


2.  The equivalent radiation resistance of small loops is 
extraordinarily low -- in the milliohms range.  Your power will be split 
between the radiation resistance and the RF resistance of the 
conductors, which is higher than the DC resistance because of the skin 
effect.  You really need to achieve the lowest possible RF resistance 
[high conductor surface area].


3.  Mag loops are resonant transformers or autotransformers.  To radiate 
at all, they MUST be exactly resonant at your TX frequency.  "Getting 
close and letting the ATU match it" will create a fairly effective dummy 
load.  Bypass the ATU and tune the loop for exact resonance.


4.  The usable bandwidth will be very low [i.e. you need to re-resonate 
the loop when you QSY, even a little].  As the circumference of the loop 
becomes smaller in relation to the wavelength [i.e. on lower frequencies 
for a fixed size loop], the BW can become smaller than the occupied BW 
of a SSB signal.


Commercial mag loops [e.g. my Alexloop] are usable from 40 up. Tuning it 
on 40 is really touchy.  It's easier on 20 and up.  They tend to run in 
the $400 range.  You can build one much cheaper, but remember #2 above.


73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 1/22/2017 6:16 AM, Robert 'RC' Conley wrote:

Guys;
I'm anticipating a move to a seniors villa and I know I will be unable to
to take my antenna farm and most of the ham shack. I've decided on my KX2
with ATU (grab-n go). A MAG LOOP should allow indoor operations at QRP
power levels.Thanks for your thoughts.
73
KC5WA



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Re: [Elecraft] (OT redoux) MAG LOOP ANTENNAS

[James F. Boehner, MD via Elecraft]

For those interested, the ARRL has a new book entitled "Ham Radio from
Indoors".  It is a quick read with a lot of good ideas!

'73 de JIM N2ZZ

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Robert
'RC' Conley
Sent: Sunday, January 22, 2017 9:16 AM
To: Elecraft@mailman.qth.net
Subject: [Elecraft] (OT redoux) MAG LOOP ANTENNAS

Guys;
I'm anticipating a move to a seniors villa and I know I will be unable to to
take my antenna farm and most of the ham shack. I've decided on my KX2 with
ATU (grab-n go). A MAG LOOP should allow indoor operations at QRP power
levels.Thanks for your thoughts.
73
KC5WA

--
May You Live Long and Prosper
what's life without a few dragons
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