I put up an 80 meter full wave loop using about 280’ of #14 wire in
almost a square. Each end of the loop was soldered to an SO-239
connector. I’m feeding the loop via RG-8 coax, about a 30’ run.

Using an MFJ Antenna Analyzer I can’t find a nice low SWR point. The
lowest I can find is at 2.5 MHz, the SWR at that point is still high at
3.4:1. In the 80 mtr band its 8:1 and in the 40 mtr band its 7:1.

My installation is far from ideal. First, the antenna for about ½ the
loop is at about 20’ high and the second half is about 15’ high. Next,
in the center of the loop is the metal frame work for a screen-room over
the swimming pool (50’ x 30’) which I’m sure interacts with the loop
antenna to some degree. The screening is not metal however the frame
work is.

Of course I can use my MFJ-949 tuner to get a low SWR on any band but by
doing so am I loosing efficiency? I also notice that trying to tune the
loop the tuner seems to be very touchy! I have noticed on 20 meters
the loop received on average about 2 S-Units better than my 20 meter
dipole. On 40 meters it receives almost 1 S-unit better than a 160’
randomwire. On 80 meters just slightly better than a 160’ randomwire.
(all antennas I’m comparing are all at about 20’ high).

I would have started making the loop shorter to bring up the resonate
frequency to 80 meters however I’m concerned as to why the lowest SWR I
can find anywhere on the HF band is still over 3:1. Is it because the
loop low to the ground (20’)? Or do I need a balum? 1:1 balum? 4:1
balum? Looking for any suggestions.

TNX
George – KI4FIA
http://www.MilAirComms.com

On Sun, 05 Jun 2005 16:57:03 GMT, GeorgeF
wrote:

I put up an 80 meter full wave loop using about 280’ of #14 wire in
almost a square.

Hi George,

That was certainly a good beginning, but questions abound as we
proceed.

Each end of the loop

How many "ends" does a loop have? This is something akin to how many
sides to a circle.

was soldered to an SO-239 connector.

One is enough, why two (or more, we still don't know how many ends
there are)?

This statement is enough to give pause. If there is more than one 239
inserted inline, it must of necessity break continuity of the loop.
This, then, means that you no longer have a loop, but rather a
fullwave dipole (presuming the loop has 2 ends).

I’m feeding the loop via RG-8 coax, about a 30’ run.

You say nothing of choking the feedpoint, and given the symptoms that
you describe, this sounds like a major omission.

In the 80 mtr band its 8:1 and in the 40 mtr band its 7:1.

Sounds like full wave dipoles (or even multiples). In other words,
consistent with previous descriptions.

My installation is far from ideal.

No one here has it any better, but by degrees. If you can do better
by trying harder, fine, but if there's no way to get the antenna
higher, or to blow away the obstructions....

Of course I can use my MFJ-949 tuner to get a low SWR on any band but by
doing so am I loosing efficiency?

In trying to tune full wave dipoles? Could be, but being so close to
the dirt is probably lowering your antenna's wicked Z to something
easier to tune (your efficiency is already dominated by ground loss).

I also notice that trying to tune the
loop the tuner seems to be very touchy!

Lack of choking at the feed point - or - you are tuning an
anti-resonant antenna.

I have noticed on 20 meters
the loop received on average about 2 S-Units better than my 20 meter
dipole. On 40 meters it receives almost 1 S-unit better than a 160’
randomwire. On 80 meters just slightly better than a 160’ randomwire.
(all antennas I’m comparing are all at about 20’ high).

Now all your previous complaints sound like whining. Do you want a
tuned antenna, or a gain antenna?

BOTH!?

73's
Richard Clark, KB7QHC

Now all your previous complaints sound like whining. Do you want a
tuned antenna, or a gain antenna?

BOTH!?

73's
Richard Clark, KB7QHC


There is one SO-239 connector, there is one piece of wire which is 280'
in lenght. On end of the wire is connected to the center pin of the
SO-239 connector while the other end of the wire is connected to the
braid side of the SO-239. Hope that clears up the configuration questions.

No I am not choking at the feed point. I was not told about a choke by
other hams who mentioned I should give an 80 meter loop a try. Is a
choke the same as a 1:1 balun? I was told (and found it also
illistrated in print) that I could directly hook 50 ohm coax to the
feedpoint. Tell me what I need to do to choke the feedpoint.

I had seen (believe it was one of the ARRL handbooks) that this antenna
should have no SWR higher than 3:1, mine is 7+:1 so I think either I did
something wrong or am missing something. Don't think I'm whining yet....

George

"GeorgeF" wrote in message
hlink.net...


Now all your previous complaints sound like whining. Do you want a
tuned antenna, or a gain antenna?

BOTH!?

73's
Richard Clark, KB7QHC


There is one SO-239 connector, there is one piece of wire which is 280' in
lenght. On end of the wire is connected to the center pin of the SO-239
connector while the other end of the wire is connected to the braid side
of the SO-239. Hope that clears up the configuration questions.

No I am not choking at the feed point. I was not told about a choke by
other hams who mentioned I should give an 80 meter loop a try. Is a choke
the same as a 1:1 balun? I was told (and found it also illistrated in
print) that I could directly hook 50 ohm coax to the feedpoint. Tell me
what I need to do to choke the feedpoint.

I had seen (believe it was one of the ARRL handbooks) that this antenna
should have no SWR higher than 3:1, mine is 7+:1 so I think either I did
something wrong or am missing something. Don't think I'm whining yet....

George


George,
Since you have an MFJ Antenna Analyzer, is there some frequency, regardless
of the SWR, where the reactive part of the impedance goes to 0? I don't know
about horizontal loops, but vertical loops are not 50 Ohm antennas.

Tam/WB2TT

"GeorgeF" wrote in message
hlink.net...
I put up an 80 meter full wave loop using about 280’ of #14 wire in
almost a square. Each end of the loop was soldered to an SO-239
connector. I’m feeding the loop via RG-8 coax, about a 30’ run.

Using an MFJ Antenna Analyzer I can’t find a nice low SWR point. The
lowest I can find is at 2.5 MHz, the SWR at that point is still high at
3.4:1. In the 80 mtr band its 8:1 and in the 40 mtr band its 7:1.

My installation is far from ideal. First, the antenna for about ½ the
loop is at about 20’ high and the second half is about 15’ high. Next,
in the center of the loop is the metal frame work for a screen-room over
the swimming pool (50’ x 30’) which I’m sure interacts with the loop
antenna to some degree. The screening is not metal however the frame
work is.

Of course I can use my MFJ-949 tuner to get a low SWR on any band but by
doing so am I loosing efficiency? I also notice that trying to tune the
loop the tuner seems to be very touchy! I have noticed on 20 meters
the loop received on average about 2 S-Units better than my 20 meter
dipole. On 40 meters it receives almost 1 S-unit better than a 160’
randomwire. On 80 meters just slightly better than a 160’ randomwire.
(all antennas I’m comparing are all at about 20’ high).

I would have started making the loop shorter to bring up the resonate
frequency to 80 meters however I’m concerned as to why the lowest SWR I
can find anywhere on the HF band is still over 3:1. Is it because the
loop low to the ground (20’)? Or do I need a balum? 1:1 balum? 4:1
balum? Looking for any suggestions.

TNX
George – KI4FIA
http://www.MilAirComms.com

Sounds like s successful installation. The tuner doesn't reduce
efficiency - - it just tunes out reactance, leaving a resistive load for
your rig to work with. Don't worry about SWR - - your radio doesn't worry
about SWR (with the reactance tuned out) - - it sees stronger signals. You
did good.
Chuck W6PKP

Chuck Olson wrote:
The tuner doesn't reduce efficiency - -

There's no such thing as a 100% efficient tuner.
--
73, Cecil http://www.qsl.net/w5dxp

----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

"Cecil Moore" says -

There's no such thing as a 100% efficient tuner.
====================================

Cecil, not a very surprising statement.
There's nothing which is 100% efficient.

What is the typical efficiency of a typical tuner with a typical
antenna.
Does it differ significantly from 100% ?
Yes or no?
----
Reg.

...

"Cecil Moore" says -

There's no such thing as a 100% efficient tuner.
====================================

Cecil, not a very surprising statement.
There's nothing which is 100% efficient.

What is the typical efficiency of a typical tuner with a typical
antenna.
Does it differ significantly from 100% ?
Yes or no?
----
Reg.


Well, at the risk of David going into conflict with the Goliaths of the
newsgroups, I would reckon that a tuner (matcher ?) must be a pretty efficient
device as it doesn't get very warm from wasting energy as heat - or perhaps my
aerials are a reasonably good match and the tuner isn't doing any / much work.
Also a tuner, I would suggest, is a fairly useful bit of kit in that it enables
the transmitter to see the sort of load it wants to and allows it to deliver
more power to the antenna system without the internal protection devices
limiting the power it produces (to avoid self destruction) even if not all
arrives at the antenna.......

Is this a fairly correct understanding of what is going on, Reg / Cecil ?

Nick

nick smith wrote:
Is this a fairly correct understanding of what is going on, Reg / Cecil ?

Yep, Nick, all I was doing was taking a tongue-in-cheek poke
at the idea that "The tuner doesn't reduce efficiency."
--
73, Cecil http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---

"Cecil Moore" says -

There's no such thing as a 100% efficient tuner.
====================================

Cecil, not a very surprising statement.
There's nothing which is 100% efficient.

What is the typical efficiency of a typical tuner with a typical
antenna.
Does it differ significantly from 100% ?
Yes or no?
----
Reg.


Well, at the risk of David going into conflict with the Goliaths of
the
newsgroups, I would reckon that a tuner (matcher ?) must be a pretty
efficient
device as it doesn't get very warm from wasting energy as heat - or
perhaps my
aerials are a reasonably good match and the tuner isn't doing any /
much work.
Also a tuner, I would suggest, is a fairly useful bit of kit in that
it enables
the transmitter to see the sort of load it wants to and allows it to
deliver
more power to the antenna system without the internal protection
devices
limiting the power it produces (to avoid self destruction) even if
not all
arrives at the antenna.......

Is this a fairly correct understanding of what is going on, Reg /
Cecil ?

Nick

====================================

Nick, your response indicates a 'perfect' understanding of what goes
on inside tuner boxes. If it runs cold or cool with 100 watts there's
nothing to worry about.

Most Guru's over-exaggerate the importance of tuner losses. But in a
practical case they never state what the efficiency actually is. Such
omissions illustrate their ignorance of the subject.

From the frequency of occurrence at which 'tuner loss' appears in
these columns, novices and even experienced amateurs can gain the
frightening impression that tuner loss is the most serious loss in the
system and is to be avoided at all costs, even to the extent of
dispensing with the tuner.

In answer to my own question, the efficiency of a typical tuner when
used with a typical antenna does not differ significantly from 100
percent. Even if it is as poor as 90% this corresponds to an
undetectable loss in signal strength of 0.5dB or 1/13 of an S-unit.
Less than the thickness of the S-meter needle. So forget it.
----
Reg, G4FGQ