MFJ 1786 magnetic loop
 

I have just started to use my new MFJ 1876 located om my balcony.
Before the antenna went into operartion the motor unit has to be replaced.
:-(
However, my problem is that the antenna will not tune in the frequency area
10.1 - 18 MHz.
On higher band there is no problem.
I known that the loaction on my balcony is not ideal but i don´t think thats
the problem or?
Any ideas??
Best regards
OZ1JZV - John

"John Passaneau" skrev i en meddelelse
...
Hi:
Do you have the loop horizontal or vertical? Horizontal mounting requires
it
to be 20 feet (sorry can't do meter in my head) above ground. Your balcony
most likely has steel structure holding it up and that is always ground.
Try
mounting it vertical if you have not already done so.


--


Hi

Thanks for you mail.

The loop is mounted vertically.

Yes, your are right. There is a lot of steel and aluminium in the structure
of my balcony.

I have tried to replace the loop but it still "refuse" to tune below 21 MHz.

I can se a small dip on the meter but are not able tuned it manually.

From 21 MHz and above I get a very low SWR.

In the instruction manual it is mentioned if there is a high SWR due to
placement of the loop, the feed loop in the antenna can be tuned to get a
lower SWR.

I have not tried this solution yet due to the good SWR on higher band, but
perhaps I should.



Regards
OZ1JZV - John

I think I would try adding a capacitor first
Art

"vandmand" wrote in message
. ..

"John Passaneau" skrev i en meddelelse
...
Hi:
Do you have the loop horizontal or vertical? Horizontal mounting
requires
it
to be 20 feet (sorry can't do meter in my head) above ground. Your
balcony
most likely has steel structure holding it up and that is always ground.
Try
mounting it vertical if you have not already done so.


--


Hi

Thanks for you mail.

The loop is mounted vertically.

Yes, your are right. There is a lot of steel and aluminium in the
structure
of my balcony.

I have tried to replace the loop but it still "refuse" to tune below 21
MHz.

I can se a small dip on the meter but are not able tuned it manually.

From 21 MHz and above I get a very low SWR.

In the instruction manual it is mentioned if there is a high SWR due to
placement of the loop, the feed loop in the antenna can be tuned to get a
lower SWR.

I have not tried this solution yet due to the good SWR on higher band, but
perhaps I should.



Regards
OZ1JZV - John

On Fri, 09 Jul 2004 16:22:01 GMT, "aunwin"
wrote:
I think I would try adding a capacitor first
It has a capacitor.

On Fri, 9 Jul 2004 12:47:53 +0100, "vandmand"
wrote:
In the instruction manual it is mentioned if there is a high SWR due to
placement of the loop, the feed loop in the antenna can be tuned to get a
lower SWR.

I have not tried this solution yet due to the good SWR on higher band, but
perhaps I should.

Hi John,

Yes, the manual suggests this, but it seems strange advice. Move your
antenna inside to a room that has less metal nearby (away from railing
and major building components) and confirm you "can" adjust for low
SWR at your problem frequencies.

73's
Richard Clark, KB7QHC

I think I would try adding a capacitor first.

It has a capacitor.

What is to prevent him adding another. The more pF the merrier.

On Fri, 9 Jul 2004 16:59:33 +0000 (UTC), "Reg Edwards"
wrote:
I think I would try adding a capacitor first.
It has a capacitor.
What is to prevent him adding another. The more pF the merrier.

This is like charging the battery to fix a flat tire.

Since it normally requires more capacitance at that end of the band it was
my intent to make the capacitance larger. But it would appear that I am in
error and should be scolded , tho I hardly believe that it is inductance
should be added for it to present a purely resistive load, It will be
interesting to find out why.
Apologies for the incorrect suggestion
Art

"aunwin" wrote in message
news:JCzHc.49499$%_6.20861@attbi_s01...
I think I would try adding a capacitor first
Art

"vandmand" wrote in message
. ..

"John Passaneau" skrev i en meddelelse
...
Hi:
Do you have the loop horizontal or vertical? Horizontal mounting
requires
it
to be 20 feet (sorry can't do meter in my head) above ground. Your
balcony
most likely has steel structure holding it up and that is always
ground.
Try
mounting it vertical if you have not already done so.


--


Hi

Thanks for you mail.

The loop is mounted vertically.

Yes, your are right. There is a lot of steel and aluminium in the
structure
of my balcony.

I have tried to replace the loop but it still "refuse" to tune below 21
MHz.

I can se a small dip on the meter but are not able tuned it manually.

From 21 MHz and above I get a very low SWR.

In the instruction manual it is mentioned if there is a high SWR due to
placement of the loop, the feed loop in the antenna can be tuned to get
a
lower SWR.

I have not tried this solution yet due to the good SWR on higher band,
but
perhaps I should.



Regards
OZ1JZV - John

Unless what he wants to do is lower the frequency. It is, after all,
just a very leaky tank circuit with "no load". (That was "tongue in
cheek" for those of you that normally fail to recognize it)

tom
K0TAR

Richard Clark wrote:

On Fri, 9 Jul 2004 16:59:33 +0000 (UTC), "Reg Edwards"
wrote:

I think I would try adding a capacitor first.

It has a capacitor.

What is to prevent him adding another. The more pF the merrier.


This is like charging the battery to fix a flat tire.

On Fri, 09 Jul 2004 21:00:25 -0500, Tom Ring
wrote:
Unless what he wants to do is lower the frequency.

Hi Tom,

But that is NOT what he is trying to do. He simply wants it to work
"as advertised." Everyone is re-inventing it to do what it was
already designed to do. It already resonates at these frequencies, to
add capacitance is very poor advice for any of several reasons.

What John needs is to determine if it is broke, or if it is
environment that is getting in the way. He is not asking for the
antenna to tune outside of its characteristic range.

The advice in the handbook suggests he open up the case and squash the
feed loop to compensate for nearby interfering, metallic structures.
This may solve the problem, but it is a ****-poor solution. If it
were a general, preferrable condition, they would sell them all this
way.

73's
Richard Clark, KB7QHC

Well, how would you suggest he troubleshoot it?

I would drop some extra C in to determine if that's what's needed. What
is it going to hurt? Otherwise all he has left, from what you have
suggested, is to complain to the manufacturer.

At the least, he should determine what, if anything, makes a difference
before complaining.

tom
K0TAR

Richard Clark wrote:

On Fri, 09 Jul 2004 21:00:25 -0500, Tom Ring
wrote:

Unless what he wants to do is lower the frequency.


Hi Tom,

But that is NOT what he is trying to do. He simply wants it to work
"as advertised." Everyone is re-inventing it to do what it was
already designed to do. It already resonates at these frequencies, to
add capacitance is very poor advice for any of several reasons.

What John needs is to determine if it is broke, or if it is
environment that is getting in the way. He is not asking for the
antenna to tune outside of its characteristic range.

The advice in the handbook suggests he open up the case and squash the
feed loop to compensate for nearby interfering, metallic structures.
This may solve the problem, but it is a ****-poor solution. If it
were a general, preferrable condition, they would sell them all this
way.

73's
Richard Clark, KB7QHC

On Sat, 10 Jul 2004 18:30:40 -0500, Tom Ring
wrote:

Well, how would you suggest he troubleshoot it?

Hi Tom,

I've already addressed that, as has the manufacturer.

I would drop some extra C in to determine if that's what's needed. What
is it going to hurt? Otherwise all he has left, from what you have
suggested, is to complain to the manufacturer.

Just "add some extra C?" Think he could find a 20KV rated cap with
100A leads at Radio Shack? Do you and Reg seriously think that a one
loop inductor and simple cap have been so confusing to manufacture
that gum and bailing wire will fix it?

We may as well offer him to file down the inductor to raise the R to
accomplish the same thing. It doesn't take much, a very thin saw
cutting a notch could do it pretty quickly. With luck, it may even
self-heal welding the slot shut.

The manual's suggestion to squeeze the feed loop is beginning to look
better already.

If it needs more C to tune, it isn't for lack of plates or their mesh.
More likely it is the capacitor drive system.

At the least, he should determine what, if anything, makes a difference
before complaining.

That has already been offered. If anything, John should determine
that it isn't a razor thin null that is escaping his attempts to lower
SWR.

73's
Richard Clark, KB7QHC

Sorry, but you didn't address anything. All your previous responses follow.

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

Richard Clark wrote:

#1 -

It has a capacitor.

#2 -

Yes, the manual suggests this, but it seems strange advice. Move your
antenna inside to a room that has less metal nearby (away from railing
and major building components) and confirm you "can" adjust for low
SWR at your problem frequencies.

#3 -

This is like charging the battery to fix a flat tire.

#4 -

ut that is NOT what he is trying to do. He simply wants it to work
"as advertised." Everyone is re-inventing it to do what it was
already designed to do. It already resonates at these frequencies, to
add capacitance is very poor advice for any of several reasons.

What John needs is to determine if it is broke, or if it is
environment that is getting in the way. He is not asking for the
antenna to tune outside of its characteristic range.

The advice in the handbook suggests he open up the case and squash the
feed loop to compensate for nearby interfering, metallic structures.
This may solve the problem, but it is a ****-poor solution. If it
were a general, preferrable condition, they would sell them all this
way.

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

Sorry but none of this seems to be advice that would help him. You
didn't address anything. All you seem to be able to do is criticize
other's suggestions and offer nothing yourself.

I hope to actually see you try to help someone sometime.

At least I am trying.

73
tom
K0TAR

Richard Clark wrote:

On Sat, 10 Jul 2004 18:30:40 -0500, Tom Ring
wrote:


Well, how would you suggest he troubleshoot it?


Hi Tom,

I've already addressed that, as has the manufacturer.

On Sat, 10 Jul 2004 19:19:56 -0500, Tom Ring
wrote:

At least I am trying.

Hi Tom,

Must've missed it, unless it was the pale joke.

73's
Richard Clark, KB7QHC