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OK -- yet most Z match tuners seem to be home brew. Does
either my MFJ-956 or MFJ-16010 tuner qualify? Or do I need
something else? IS there an inexpensive commercially made
one that works for cheap? If not cheap, for a lot?

Thanks - I will Google around on this...

Given what you say, I could make a loop on the outside of my deck railing, which would be 20 feet by 5 feet, and all be about ten feet
above ground. From your comment that would be a decent loop, and
tunable in the shack with a z match tuner (assuming I figure out
what one is and how to get or make one....) Hmmmm... I like this
prospect.

/// Richards ///
===========================================================

Michael Hebert wrote:

Richards,

Like Jim Dunstan said the loop doesn't need to have a tuning cap. You
can use a simple wire loop with a remote tuner. Google for "Z-match"
and you will find a simple and very capable tuner. If you need to run
anything longer than 20' or so for a feedline you can use 450 Ohm TV
ladderline (if you can find it) or make some ladderline with #20 wire
spaced an inch or so apart. That should be good for upwards of 50'
with very little loss. I have even used runs of 20' of 300 Ohm foam
filled twinlead with good success.

Loop size?? Whatever you can erect!! I have used square loops with
sides as small as 2' and as large as 25'. The Z-match tunes them all!

Right now I'm using my Z-match to tune an indoor loop strung around
two sides of my bedroom and tuned through about 10' of #22 speaker
wire. Yes, it's noisy but it works better than a random wire or dipole
from inside my 2nd floor urban apartment.

73,

'Bear' NH7SR

I wish I could find a simple design for a SWL loop antenna
that would cover, at least, say, between 5 and 10 MHz. Just
something simple I could stick up in the yard, maybe. All these
amplifiers, tuning capacitors, etc. Where is a simple loop?

Not easily done. Loops are inherently low impedance antennas, and when
you're well below the first resonance they look a lot like an inductor. As
you approach the resonance, they begin to look like a shorted transmission
line. I had to tackle this when I was designing my own active loops, and I
was able to devise a remote tuning and amplifier using the coax as both the
amplifier power and the tuning voltage. It became a 2-part series in QEX.

A 1M diameter loop made with 0.25" copper tubing (first resonance at
27.5MHz) will have an impdance of 0.5 + j110 ohms at 5MHz, 1.0 + j 230 ohms
at 10MHz, 1.5 + j450 ohms at 15MHz, and 25 +j1500 ohms at 25MHz. Not
exactly a linear relationship.

The same antenna can be used at 40M with just a 64:1 impedance
transformer (three 4:1 transformers in series) and a fixed capacitor, but
you will still need some sort of tuning somewhere in order to have it
function well over the entire band. Making the transformers so they will
have low loss is a real pain.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_ |/ Principal Engineer
oo\ Sonoran Radio Research
(__)\ _ P.O. Box 25240
\ \ .' `. Tempe, Arizona 85285-5240
\ \ / \
\ '" \ IEEE Senior Member #40274515
. ( ) \
'-| )__| :. \ Email: christrask@...
| | | | \ '.
c__; c__; '-..'>.__

Graphics by Loek Frederiks

I wish I could find a simple design for a SWL loop antenna
that would cover, at least, say, between 5 and 10 MHz. Just
something simple I could stick up in the yard, maybe. All these
amplifiers, tuning capacitors, etc. Where is a simple loop?

(Crying in my beer this holiday...) //// Richards ////
=================================================================

Jim Dunstan wrote:

At 02:34 PM 5/28/2007 +0100, you wrote:

At 12:06 pm ((PDT)) Sun May 27, 2007, Jim Dunstan wrote:

[big snip]
A tuned loop (about 3' in diam.) is my favorite receiving antenna when
living at the apartment on the 9th flr. I put mine on the balcony and tune
it remotely with 12 ft of 300 ohm twin lead fed into a Z-match antenna
tuner.

Does this mean there is no capacitor attached to the loop
and all tuning is done by the ATU? So the resistance of the
feeder is included in the loop resonance?

If so, you could get higher Q and hence more output by
tuning at the loop. OTOH, Q is one of those good things
one can have too much of. ;-)

Regards, Len

Hi Len,

You are correct on all counts. The original purpose of the arrangement was to provide a decent antenna for my SWL activity (Sony 7600 receiver) from 5mhz to 15mhz. The tuner sits inside the window looking out on the balcony. The operation is simple .... when it hits resonance the noise level goes up on the receiver .... that's it!! Compared to the whip antenna the performance is a quantum leap improvement, even if I bring the receiver/whip out on the balcony.

I also built transmitting loops for operation at the apartment, using the more traditional tuning/matching arrangements. They work fine .... when I tuned in to SW station (eg 15mhz ... close to 20M) I could NOT detect appreciable difference in performance listening to SW broadcast stations. Of course, this kind of tuning is not compatible with band hopping.

In order for a loop to be an effective SWL antenna it must able to be mounted remotely and provide a reasonable signal level across a very broad range (at least 5-15 mhz or more). In order to provide a reasonable signal across this broad spectrum the antenna either has to be remotely tuned or be broad banded with amplification at the source. My system is the first ... remotely tuned .... with the distance limitation of approximately 15-20 ft. with balance feed line. If you go beyond that distance the capacitance of the feed line starts to limit tuning range. It is also possible to tune such a loop with coax feed line but the distance is even more limited as coax represents greater capacitance.

Jim, VE3CI

At 12:06 pm ((PDT)) Sun May 27, 2007, Jim Dunstan wrote:

[big snip]
A tuned loop (about 3' in diam.) is my favorite receiving antenna when
living at the apartment on the 9th flr. I put mine on the balcony and tune
it remotely with 12 ft of 300 ohm twin lead fed into a Z-match antenna
tuner.

Does this mean there is no capacitor attached to the loop
and all tuning is done by the ATU? So the resistance of the
feeder is included in the loop resonance?

If so, you could get higher Q and hence more output by
tuning at the loop. OTOH, Q is one of those good things
one can have too much of. ;-)


Regards, LenW
--
From Yahoo! Groups Help: ... trim all the irrelevant quoted text
out of your message (as a courtesy to the other members of
the group to make the digest easier to read).

Hey Everyone,

Excuses for those who saw this message as well on the
Shortwave-SWL-Antenna group; someone posted off list about this list
to me, so I just signed up here!


Who here has built a WL1030 and can help me answer these questions?

1) How do you like it? Its said its comparable to a Wellbrook, if you
know, can you comment on it?

2) Did you built one without the PSU? If so:
2a) What did you used for the 10v supply? (especially regarding their
comment it must be a "smooth 10v DC")
2b) Am I right to assume if you manually supply the amplifier 10v you
need to cut connection L1 - J3? And the 1/2Vcc is being supplied by
the extra/separated piece of circuit top-right on the diagram?

Anything else you would like to say about building this antenna?

Building circuits is rather new for me, but am keen to built this
antenna, as its both lots cheaper then a Wellbrook, and more fun to
make it yourself.

Thanks all,

Jeroen Kloppenburg

Jim, I don't even have to go out to the patio to make adjustments as my loop is mounted indoors where it picks up just as much noise as my whip antenna (36") and actually is capable of discriminating against some of it. I cover 8300-28900 khz on the smaller section of the dual capacitor, and with a small clip connector 4400-22000 khz both sections in parallel. Clipping in a 250 mmfd. mica gets me down to 3450 so I have the 80/75 meter band covered. Space constrictions in the apartment mean that my whip is not fully extended, so I get stronger sigs from the loop (the Sat 800 antenna systems are instantly switchable for comparison). I have a triple-spaced variable I could try if I wanted to transmit, but I found out a few years ago that sigs from the apartment were getting into the cable tv system and also into people's hearing aids {senior citizens' home} and as I will be 90 myself later this year I don't want to "make waves". Of course, reception is not what it used to
be but dividing my time between the computer and SWL fills in my hobby time. John M.

---------------------------------
You snooze, you lose. Get messages ASAP with AutoCheck
in the all-new Yahoo! Mail Beta.

At 07:16 PM 5/26/2007 -0700, you wrote:

I was a member of this group some time ago... somehow I became disconnected but the daily message content continued to be delivered to my e-mail address. While continuing to read the mail, I was struck by a construction note that discouraged the use of variable condensers for tuning purposes.because, as I interpreted it, the result would be weak signals. I decided to experience this phenomenon myself, so I have built a relatively crude loop, based on materials already at hand plus a 30 inch hula hoop. I was startled at how strong the signals are, because I had been led to believe that a loop delivered somewhat weaker signals along with a substantial loss in noise, in other words a better signal-to-noise ratio at the cost of a few S points on a tuning meter. I do have solid-state varactors on hand but I have been trying a selection of two-gang tuning condensers, mostly from surplus stores of around fifty years ago. I concluded that the weak link would be the connection
to the moving vanes (rotors) which is made via a ball-bearing race at one or both ends, and a spring brass or phosphor bronze contact finger resting against the metal frame. With 50 years of oxidation on the contactor, this could lead to vastly diminished performance by introducing resistance or diode action (or both) into the circuit. Therefore, I prepared the end of the contactor for soldering rather than a pressure fit. I rubbed it CAREFULLY (!) with a sand or emery board such as used in manicuring and tinned it with solder without damaging the rest of the structure. One end of the loop would be soldered there. The other point of contact ia where the grounded shaft rotates against the finger. To deal with the oxide there, I gave a couple of puffs of contact cleaner and worked the rotation about 20 times and hoped for the best. I also gave a couple of puffs to the ball race and to the shaft bearing at the back of the condenser. My loop is crude: a single turn of
insulated stranded hook-up wire fastened to the outer edge of the hula hoop with strips of masking tape about every 8 inches. The tuning conderser is mounted at the top of a piece of wood about 64" x 1 1/2 " , the loop mounted directly below with a couple of plastic ties, one end soldered to the contact finger, the other end soldered to the fixed plates (stators). For the pick-up loop, the experience of other people suggested 1/5 the diameter of the main loop, which would put me at 6". I happened to have on hand a circular antenna of the type that used to be supplied with TV sets using UHF tuners.... it has a diameter of 9" but that is what I am using for now. It is connected via RG58/U to the 52 ohm input of my Grundig Sattelit 800 and at the moment (0205 utc) I am listening to a strong signal from Habana, Cuba on 6180 khz. I know I have gone on and on somewhat, but I felt it worthwhile to dispel the notion that old tuning capacitors were no good and, who knows,
it might encourage some hesitant souls to try their luck at constructing a "crude" loop. John MacKay, VE7AFN.

Hi John,

If you are building a tuned loop for MF or HF receiving purposes the quality of the (air gap) variable capacitor is of minor consequence. In most cases the advantages of a tuned loop (even those using 30 year old variable capacitors with some rust in their joints) is a quantum leap ... and in most cases they are fed into or inductively coupled to modern high gain receivers. The quality of the capacitor becomes significant when the tuned circuit performance is more critical as for example when using a crystal radio receiver, or when feeding power to the loop antenna.

There are some tricks that can be used with old variable capacitors with questionable contact surfaces .... for example if you have a 2 gang (365 pfd per gang) capacitor you can connect them in series and isolate the frame from the circuit. This will give you a maximum of 182 pfd capacity .... but no questionable contact surfaces. If you have a 4 gang 500 pfd capacitor (as someone on this group mentioned) you could hook them into 2 parallel/ series pairs and have a full 500 pfd capacitor with no contact surface to deal with.

The added advantage is that the voltage capability is also doubled. If your dealing with power, then the capacitor problem is not only one of rusty joints but voltage capability .... since voltage across the capacitor gap rises very quickly as power is increased.

A tuned loop (about 3' in diam.) is my favorite receiving antenna when living at the apartment on the 9th flr. I put mine on the balcony and tune it remotely with 12 ft of 300 ohm twin lead fed into a Z-match antenna tuner. In order to rotate it I walk out on to the balcony and give it a twist hi hi . PS ... I have fed power into such a loop and have made several contacts ... but the design was intended for reception only. I am sure if I constructed the loop from larger diameter copper tubing instead of RG-58 coax and heavy duty home brew open wire feed line instead of 300 ohm twin lead, it would make a decent antenna for transmission as well.

Jim, VE3CI

I was a member of this group some time ago... somehow I became disconnected but the daily message content continued to be delivered to my e-mail address. While continuing to read the mail, I was struck by a construction note that discouraged the use of variable condensers for tuning purposes.because, as I interpreted it, the result would be weak signals. I decided to experience this phenomenon myself, so I have built a relatively crude loop, based on materials already at hand plus a 30 inch hula hoop. I was startled at how strong the signals are, because I had been led to believe that a loop delivered somewhat weaker signals along with a substantial loss in noise, in other words a better signal-to-noise ratio at the cost of a few S points on a tuning meter. I do have solid-state varactors on hand but I have been trying a selection of two-gang tuning condensers, mostly from surplus stores of around fifty years ago. I concluded that the weak link would be the connection
to the moving vanes (rotors) which is made via a ball-bearing race at one or both ends, and a spring brass or phosphor bronze contact finger resting against the metal frame. With 50 years of oxidation on the contactor, this could lead to vastly diminished performance by introducing resistance or diode action (or both) into the circuit. Therefore, I prepared the end of the contactor for soldering rather than a pressure fit. I rubbed it CAREFULLY (!) with a sand or emery board such as used in manicuring and tinned it with solder without damaging the rest of the structure. One end of the loop would be soldered there. The other point of contact ia where the grounded shaft rotates against the finger. To deal with the oxide there, I gave a couple of puffs of contact cleaner and worked the rotation about 20 times and hoped for the best. I also gave a couple of puffs to the ball race and to the shaft bearing at the back of the condenser. My loop is crude: a single turn of
insulated stranded hook-up wire fastened to the outer edge of the hula hoop with strips of masking tape about every 8 inches. The tuning conderser is mounted at the top of a piece of wood about 64" x 1 1/2 " , the loop mounted directly below with a couple of plastic ties, one end soldered to the contact finger, the other end soldered to the fixed plates (stators). For the pick-up loop, the experience of other people suggested 1/5 the diameter of the main loop, which would put me at 6". I happened to have on hand a circular antenna of the type that used to be supplied with TV sets using UHF tuners.... it has a diameter of 9" but that is what I am using for now. It is connected via RG58/U to the 52 ohm input of my Grundig Sattelit 800 and at the moment (0205 utc) I am listening to a strong signal from Habana, Cuba on 6180 khz. I know I have gone on and on somewhat, but I felt it worthwhile to dispel the notion that old tuning capacitors were no good and, who knows,
it might encourage some hesitant souls to try their luck at constructing a "crude" loop. John MacKay, VE7AFN.

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I am building the contol boxes for the K9AY Loop and am using
the FAR Circuits boards. I would love to hear from anyone who has built
them

73 John NS5Z

Automatic tuning could be made to work, but you will have to furnish a
pilot carrier for the coupler to know how to tune the loop. The SGC
"stealth kit" is basicly a green camouflaged loop and support with a
"smart-tuner". Information on the smart-tuner states that as soon as
you begin to transmit, the coupler senses your frequency and tunes the
antenna, so your transmitted signal is the pilot carrier. The signal
level required to tune the coupler/antenna may be quite small, perhaps
1.5 watts, but is required. Because the coupler could tune in just a
few seconds, you could, with a transfer switch, replace the receiver
with a signal generator on-frequency, tune the antenna to frequency,
and switch the antenna back to the receiver. The radiated signal from
1.5 watts injected into the antenna would not be easy to detect for
that brief period.

The other possibility that does work is to store presets for all
possible frequencies, and then simply go to those frequencies. We do
that with many of our commercial HF transmitters. A simple way to
implement this is to use a motor-driven capacitor with a "follow-pot"
to tune the antenna, and sense the position of the tuning capacitor.
Regards,
Paul
WA5LFY


--- In loopantennas@..., Jim Dunstan <jdunstan@...> wrote:

At 03:59 PM 5/25/2007 +0000, you wrote:

Hi, loop fans! I'm thinking of using an auto antenna tuner to match a
HF square loop's internal impetance with RG58. Is that possible?
Thanks in advance...

Yes, it is certainly possible. ATU's are primarily designed to tune

2-30

mhz and go into the auto tune mode when they receive an injection of
several watts of power from your xmitter. The larger the loop the more
efficient it will be as a radiator and receiver of radio signals.

The SGC

company advertises a 'Stealth' package based on an 80 ft wire loop

and an

ATU. The 80' wire is formed into a loop of a single, 2, or 3 turn
loop. They have lots of info on their site.

Jim, VE3CI

At 03:59 PM 5/25/2007 +0000, you wrote:

Hi, loop fans! I'm thinking of using an auto antenna tuner to match a
HF square loop's internal impetance with RG58. Is that possible?
Thanks in advance...

Yes, it is certainly possible. ATU's are primarily designed to tune 2-30 mhz and go into the auto tune mode when they receive an injection of several watts of power from your xmitter. The larger the loop the more efficient it will be as a radiator and receiver of radio signals. The SGC company advertises a 'Stealth' package based on an 80 ft wire loop and an ATU. The 80' wire is formed into a loop of a single, 2, or 3 turn loop. They have lots of info on their site.

Jim, VE3CI

Hi,

An automatic antenna tuner works matching the transmitted signal of the
transmitter to the antenna. If you are using it for this purpose it
will work well. I am using an LDG AT-200Pro autotuner for this purpose.
If you want to use it on a receiver only, it will not tune.

Hi, loop fans! I'm thinking of using an auto antenna tuner to match a
HF square loop's internal impetance with RG58. Is that possible?
Thanks in advance...

Hi Fraser,

I'll give them a try and see what's still available. I had already
ordered the "2nd half of the 90's" CD from the Medium Wave Journal,
which should include several of Andy's articles.

Thanks,
Rob

Hi Rob,

Shortwave Magazine became part of Radio User magazine which is a PW
Publishing product. Since the change it has not been very clear on
the website how you get copies of older SWM articles.

You can buy SWM articles via the following email address and phone
number:

Book & Back Issue Orders

books@...

Tel: 0870 224 7830
Fax: 0870 224 7850

At the back of the Radio User magazine another email address is
listed against the back issue charges (?5 per back issue magazine).

bookstore@...

Damn, Yahoo Groups Email address detector has hidden the email
addresses in my message.

Here they are again but I've used AT instead of @ so you will need to
change the email address accordingly before use.

Book & Back Issue Orders

booksATpwpublishing.ltd.uk

bookstoreATpwpublishing.ltd.uk

Fraser

--- In loopantennas@..., "Rob Moore" <rmoore5@...> wrote:

Hi John,

Unfortunately, there doesn't seem to be a way to order individual
articles (or even entire back issues) from SHortwave (Wireless?)
magazine when I looked on their website. Do you have a method?

Rob

Hi Rob,

Shortwave Magazine became part of Radio User magazine which is a PW
Publishing product. Since the change it has not been very clear on
the website how you get copies of older SWM articles.

You can buy SWM articles via the following email address and phone
number:

Book & Back Issue Orders

books@...

Tel: 0870 224 7830
Fax: 0870 224 7850

At the back of the Radio User magazine another email address is
listed against the back issue charges (?5 per back issue magazine).

bookstore@...

I ordered some photocopied articles from the 1980's and they cost me
?3 each inc P+P. Overseas orders attract a ?1 additional charge. Two
of the articles that I asked for were unavailable as the original
archive magazine had been lost.

Hope this helps

Fraseer

Hi John,

Unfortunately, there doesn't seem to be a way to order individual
articles (or even entire back issues) from SHortwave (Wireless?)
magazine when I looked on their website. Do you have a method?

Rob

--- In loopantennas@..., crabtreejr@... wrote:

Hello Rob et al

Andy Ikin did write a number of articles, as listed below. There

may have

been more.

A. Ikin, Active solution?, Short Wave Magazine, Oct 1996, pp 22, 23,

23 36

A. Ikin, Intermodulation - General Consideration for Active

Antennas, Short

Wave Magazine, Nov 1996, pp 28, 29
A. Ikin, Quieten it Down, Short Wave Magazine, Dec 1996, pp 32
(about low noise performance from long wire antennas)
A. Ikin, Broadband Loop Aerials (part 1), Medium Wave News, Jan

1998, pp

13-16
A. Ikin, Broadband Loop Aerials (part 2), Medium Wave News, Mar

1998, pp 9-12

A. Ikin, Receiving Loop Antennas, Short Wave Magazine, Oct 1998, pp

26-28

HTH and 73

John KC0G


In a message dated 5/22/07 6:19:49 PM Central Daylight Time,
rmoore5@... writes:

snip > Hi Nigel,

Actually, I'd be really interested to hear something about his
background. Did he work for a Radio company or has this always been a
hobby? When did he get the idea to make a better loop antenna? What
new things will be coming from his shop in the future? Would he be
willing to "Educate" some of us here on antenna design? It would be
fascinating.

snip >

Rob

***
See what's free at .

[Non-text portions of this message have been removed]

Hello Rob et al

Andy Ikin did write a number of articles, as listed below. There may have
been more.

A. Ikin, Active solution?, Short Wave Magazine, Oct 1996, pp 22, 23, 23 36
A. Ikin, Intermodulation - General Consideration for Active Antennas, Short
Wave Magazine, Nov 1996, pp 28, 29
A. Ikin, Quieten it Down, Short Wave Magazine, Dec 1996, pp 32
(about low noise performance from long wire antennas)
A. Ikin, Broadband Loop Aerials (part 1), Medium Wave News, Jan 1998, pp
13-16
A. Ikin, Broadband Loop Aerials (part 2), Medium Wave News, Mar 1998, pp 9-12
A. Ikin, Receiving Loop Antennas, Short Wave Magazine, Oct 1998, pp 26-28

HTH and 73

John KC0G


In a message dated 5/22/07 6:19:49 PM Central Daylight Time,
rmoore5@... writes:

snip > Hi Nigel,

Actually, I'd be really interested to hear something about his
background. Did he work for a Radio company or has this always been a
hobby? When did he get the idea to make a better loop antenna? What
new things will be coming from his shop in the future? Would he be
willing to "Educate" some of us here on antenna design? It would be
fascinating.

snip >

Rob

***
See what's free at .