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loopantennas-owner@...

Thanks,
Steve Greenfield

--- In loopantennas@..., "gfreport1" <gfreport@...> wrote:

I stopped by to have lucnh with Terry and this is what he has
to add.

Thanks for that info, much appreciated :)

I prefer the active dipoles designed by Dallas Lankford.

Gotcha =)

I'm still looking for the availability for some of the parts of the
wl1030 and for some I might need to get them per 10, so the wl1030
plan might simply be pushed of the table solely for that reason.

I will look into those dipoles as well. Maybe the cheap/easier to
built version first that is :) Still need to gain more building
experience anyway...

Thanks all!

--- In loopantennas@..., gandalfg8@... wrote:

In a message dated 31/05/2007 16:04:34 GMT Daylight Time,
rblum@... writes:

I think you are seeing the capacitors he added. He says he added 1 mf
ceramic capacitors, and that the diodes were not noisy, because they
"did not reduce the noise at the lower end of the NDB". He apparently
measured or at least noted the noise; added capacitors and inductors;
noted no significant noise reduction; concluded the capacitors and
inductors really weren't needed for that particular R/S supply.



---------------------------------
Hi Bob

The point Len was making is that you can see the added capacitors on

the

back of the board but that there are already capacitors across the

diodes,

mounted as normal through hole components on the circuit boards, and

that could

have been the reason there was no noise reduction in this example.
Whether or not the existing level of noise was considered acceptable

does

not seem very clear, altough I get the impression it might have

been, the

observation was only that it didn't change.

If you look at the lower photos in the reference given earlier

you'll see

that Len is right.
The existing caps look, to me anyway, to be fairly small ceramic

types but

they are definitely in circuit and part of the original construction.
You can see two of the original capacitors clearly, a bit of

another less

clearly, and can also see from the rear photo that they are across

the diodes,

in addition to the later ones mounted on the rear of the PCB.

regards

Nigel
GM8PZR

Thanks for the clarification, Nigel. This time I zoomed the thing up
to 300+% and I see the little fellas you are talking about.

Nice "talking" to you again.

Bob

Could this design be adapted to have the power supply through the coax?

Cor Beijersbergen van Henegouwen

For a simpler and better acitve dipole that really works, I
have one, try
<>
The acitve parts, 2 each , J310 JFET and a 2N5109 won't break the
bank are are much easier to setup then Dallas's other active antenna.

Will

At 06:12 AM 5/31/2007 +0000, you wrote:

--- In
<mailto:loopantennas%40yahoogroups.com>loopantennas@..., Jim
Dunstan <jdunstan@...> wrote:

At 05:19 PM 5/30/2007 +0000, you wrote:

From personal experience I can say antenna works well at 27MHz.

Are you speaking of the active whip that he mentions works well at SW
too? As this one needs a ground rod its one of the antenna's I wont be
able to use (4th floor apartment building no lighting rods etc either...)

Hi,

In the article on the active antenna the author shows two versions ... one
version is a mono pole, the one you mention that uses a ground rod. The
other version uses a dipole. The dipole version is really 2 complete 1
meter whip/amplifiers constructed as mirror images. This produces a
balanced system that does not need to be mounted at ground level. It is
the version you would require in your location in the 4th flr apartment.y

The active antenna was designed to provide reception at MW &LW bands ...
but a person who has used the system says it works well at 27Mhz ...
therefore I assume it works fine across the HF band as well.

Jim, VE3CI

--- In loopantennas@..., gandalfg8@... wrote:

In a message dated 30/05/2007 18:57:05 GMT Daylight Time, novost@...
writes:

We may never know if the _diodes_ had the potential for creating
RF noise because they were already bypassed with substantial-
looking disk ceramic capacitors, two of which are clearly visible
in his photograph and the wires for all are visible on the solder
side of the PCB - so it shouldn't be a great surprise that there
was little RF noise and that extra capacitors didn't reduce it.

------------------------

I was about to reply...
"C'mon, surely he ain't gonna make such an obvious mistake".....
but you're right:-)

I think you are seeing the capacitors he added. He says he added 1 mf
ceramic capacitors, and that the diodes were not noisy, because they
"did not reduce the noise at the lower end of the NDB". He apparently
measured or at least noted the noise; added capacitors and inductors;
noted no significant noise reduction; concluded the capacitors and
inductors really weren't needed for that particular R/S supply.

Bob

In a message dated 31/05/2007 16:04:34 GMT Daylight Time,
rblum@... writes:

I think you are seeing the capacitors he added. He says he added 1 mf
ceramic capacitors, and that the diodes were not noisy, because they
"did not reduce the noise at the lower end of the NDB". He apparently
measured or at least noted the noise; added capacitors and inductors;
noted no significant noise reduction; concluded the capacitors and
inductors really weren't needed for that particular R/S supply.



---------------------------------
Hi Bob

The point Len was making is that you can see the added capacitors on the
back of the board but that there are already capacitors across the diodes,
mounted as normal through hole components on the circuit boards, and that could
have been the reason there was no noise reduction in this example.
Whether or not the existing level of noise was considered acceptable does
not seem very clear, altough I get the impression it might have been, the
observation was only that it didn't change.

If you look at the lower photos in the reference given earlier you'll see
that Len is right.
The existing caps look, to me anyway, to be fairly small ceramic types but
they are definitely in circuit and part of the original construction.
You can see two of the original capacitors clearly, a bit of another less
clearly, and can also see from the rear photo that they are across the diodes,
in addition to the later ones mounted on the rear of the PCB.

regards

Nigel
GM8PZR

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

At 05:19 PM 5/30/2007 +0000, you wrote:

From personal experience I can say antenna works well at 27MHz.

Are you speaking of the active whip that he mentions works well at SW
too? As this one needs a ground rod its one of the antenna's I wont be
able to use (4th floor apartment building no lighting rods etc either...)

At 05:19 PM 5/30/2007 +0000, you wrote:

From personal experience I can say antenna works well at 27MHz.

The main point with either twin lead or coax is bring the feedline
out at a right angle to the orientation of the antenna for at least
10'.

Will

Hi Will,

You are right it is important to take care when dressing antenna feed line, especially when dealing with a dipole (balanced) antenna in order to minimize antenna/feed line interaction which might disturb antenna balance. However the question was about the use of zip cord or speaker wire as a feed line .... and whether it would pick up RFI when it comes into the RFI polluted environment of the house/radio operating position; the assumption being that coax would be better.

The main point was addressing the question. Properly dressed and terminated balanced feed line is definitely more immune to RFI than a standard properly terminated unbalanced coax feed line. This is true at audio and RF frequencies. Would you agree?

Jim, VE3CI

At 9:35 am ((PDT)) Tue May 29, 2007, gfreport wrote:

Posted by: "gfreport1" gfreport@... gfreport1
Date: Tue May 29, 2007 9:35 am ((PDT))

This one is uses cheaper parts.
<>

Note that of the second power supply here, 12 volt AC/DC #273-1776,
Dallas says; "It turned out that the diodes in this power supply were
not noisy like the diodes in the bridge I used for the 24 VDC supply",
giving as the reason; "because bypassing them with the 1 mF
capacitors did not reduce noise at the lower end of the NDB"
(Aeronautical Non Directional Beacons are at 200 - 500 KHz.)

We may never know if the _diodes_ had the potential for creating
RF noise because they were already bypassed with substantial-
looking disk ceramic capacitors, two of which are clearly visible
in his photograph and the wires for all are visible on the solder
side of the PCB - so it shouldn't be a great surprise that there
was little RF noise and that extra capacitors didn't reduce it.


Regards, LenW

In a message dated 30/05/2007 18:57:05 GMT Daylight Time, novost@...
writes:

We may never know if the _diodes_ had the potential for creating
RF noise because they were already bypassed with substantial-
looking disk ceramic capacitors, two of which are clearly visible
in his photograph and the wires for all are visible on the solder
side of the PCB - so it shouldn't be a great surprise that there
was little RF noise and that extra capacitors didn't reduce it.



------------------------

I was about to reply...
"C'mon, surely he ain't gonna make such an obvious mistake".....
but you're right:-)

Not sure if I'd describe them as "substantial" but definitely fitted, you
can even see part of a third one in the bottom photo if you look carefully.

How odd.

regards

Nige
GM8PZR

Here is an interested active antenna:



Has somebody in this group built one?
---
timo

Richards,

The MFJ-956 and MFJ-16010 tuners are both intended for use with random
length wire antennas... not loops. MFJ does make loop tuners. The
MFJ-933 and -935 but they are not Z-match designs. Those tuners are
meant to be mounted at or _very_ close to the loop.

Using any tuner remotely located from the loop (including the Z-match)
will distort the loop pattern since the feedline becomes part of the
loop. With close-spaced wire like speaker cable there will be greater
signal loss than with wider spaced wire like 300 Ohm twinlead or 450
Ohm ladderline. I follow a very loose rule of thumb that says the loop
circumference should be a minimum of 4 times the length of the
feedline. That seems to ensure that the loop does not simply act like
a short circuit at the end of the feedline. The greater the loop
circumference the more signal capture area it will have... and that's
the name of the game. The tuner is simply used to enable a reasonably
efficient transfer of that energy to the receiver.

The Z-match is not difficult to build. Mine uses one 365pF variable
cap, 1 dual-365pF variable cap, the coil wound on a T80-6 toroid and a
DPDT switch to choose between the two output link windings. I believe
I used the design on G3YCC's web page as a guide. The whole thing is
build into a black plastic enclosure from Radioshack. The caps and
toroid were ordered from Ocean State Electronics.

It's certainly much cheaper to build one of these than to buy an MFJ
tuner... and, IMHO, it's much more flexible in use for receiving. I
have used mine for transmitting also but the caps limit power handling
to a max of about 5 watts.

73,

'Bear' NH7SR

At 05:54 PM 5/29/2007 +0000, you wrote:

Try these:
This is the better, but the FET is very pricy.

<<>>

OK...

There are some issues I see with my VERY little experience (basically,
none) with building circuits but I will see if I can make a try.

Why is there a gas discharge tube in the dipole? And if you use
speakerwire for the connection between antenna and receiver, wont it
pick up noise inside the house?

Hi:

Let me help with your questions .... the short (1 meter) antenna is
connected to the FET in either a mono pole or dipole version of his
circuit. The gas discharge tube is a safety device that will discharge any
DC static build up to ground. It provides no function to enhance
reception. As I mentioned he shows 2 versions of his antenna/amplifier ...
the first is single ended (mono pole) and should really be mounted right on
the ground next to the ground rod. The second version is a dipole ...
which will allow the antenna/amplifier to be mounted away from ground.

The speaker wire or zip cord is a balanced feed line. His objective (he
goes to great lengths) is to completely isolate the antenna (1 meter in
length) from the amplifier and feed line. The amplifier is high gain, high
impedance input and low noise. He uses RF transformers to isolate the unit
from the feed line. In critical situations it is much easier to maintain
balance and isolation using balanced feed line instead of coax. Properly
terminated balanced line will not pick up RF ... eg noise. The reason is
that the noise signals are picked up at any point in the feed line in
exactly the same strength and phase. When the meet at the terminating
transformer winding they will be 180 deg out of phase and cancel each other
out .... eg no noise. This is not true in coax.

And finally, he speaks of just LW and AM, but my interest is in the
shortwave (60mtr tropical band is my main focus I want a new antenna for).

I do not know how well the unit will work on 60M tropical band. The
antenna and amplifier should be just fine .... the limiting factor will be
the transformers .... which are designed for LF/MW frequencies.

Jim, VE3CI

frederick1444 schreef:

Hi, I am looking for an effective antenna to use that will pull in
local AM stations more clearly, about all I hear on AM now is static. Do loop antennas work for FM stations? I would like better FM
reception too.

about 40 cm dia.

I have made FM loop with dia 86cm, good directivity.


Marc

--
--
Shortwave transmissions in English, Francais, Nederlands, Deutsch, Suid-Afrikaans, Chinese, Dansk, Urdu, Cantonese, Greek, Spanish, Portuguese, ...
Updated every 2-3 months.

Try these:
This is the better, but the FET is very pricy.

<>


OK...

There are some issues I see with my VERY little experience (basically,
none) with building circuits but I will see if I can make a try.

Why is there a gas discharge tube in the dipole? And if you use
speakerwire for the connection between antenna and receiver, wont it
pick up noise inside the house?

And finally, he speaks of just LW and AM, but my interest is in the
shortwave (60mtr tropical band is my main focus I want a new antenna for).

--- In loopantennas@..., "gfreport1" <gfreport@...> wrote:
<snip>

Thank you William, much appreciated.

If you have any additional info later about the power supply its most
welcome. I will also dive into those active dipoles. Ultimately its
about improving my reception, and learning some building skills =)

I might end up building both, so I'm sure to find out whats best for
my location.

Jeroen

Hi, I am looking for an effective antenna to use that will pull in
local AM stations more clearly, about all I hear on AM now is static.
Do loop antennas work for FM stations? I would like better FM
reception too.
Any antenna has to pass WAF (wife acceptance factor)so smaller is
better, no 4,5 or 6 foot antennas please.
Would a 8 inch or longer ferrite bar provide better reception?
Forgive all the newbie questions, just getting into a nice componet
stereo system, but have already learned that even a good vintage tuner
(Sansui TU 717)cann't pull in stations without a decent antenna. Most
of the mass produced antennas I have investigated either don't seem to
work or cost an arm and a leg.
Any suggestions greatly appreciated.
PS I live in a valley surrounded by hills in Petaluma, Ca.
Thanks Frederick.

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