Necessity being the mother of invention, bit me. Last weekend was CQWW CW on
160m. I stumbled on it and had no 160m antenna. I have a terrific performer
for 80m, an inverted L with 33, 60' radials stapled on the ground. I also
have a Carolina Windom 80 at 42' fed with perhaps 100' of RG8x.

Since it was a cw contest, I figured, brute force stuff with my tuner. Very
interesting results.

I tried the 80m inverted L, feeding just the center conductor, and also
tying the shield and center conductor together ...both cases feeding it as
an end fed wire. I got no band noise and very poor signals, but what the
heck, I worked 10 or 15 stations who were running S7 or better in spite of
things. I could tell I wasn't being heard very well. (I was also running
about 500w output).

Then I tried the same trick with the CW-80. I fed the center conductor
only...band noise jumped up to S-3, signals were amazingly loud, and I
started working everyone I could hear...first call. It didn't matter how
weak they were, I got answered immediately. I worked 44 states, France, and
two stations in Bermuda. My question: What is this antenna configuration and
why is it working so well, especially relatively low angle stuff like France
and Bermuda, West Coast, etc. I don't get it? (Feeding both shield and
center tied together, or feeding it "normally" did not work as well as just
feeding the center conductor)

This is an OCF Dipole, 85' on one side and 51' on the other. I have no idea
which side of the dipole was fed by the center conductor of the coax. My
coax runs underground (5' below the ground for 55' to the tower base), and
then up parallel to the tower (5 feet from the tower) for the 40' or so the
CW-80 is in the air). This really shouldn't work very well, yet it does.
VSWR bandwidth seems consistent with a somewhat efficient antenna (about 40
Khz before having to re-tune the tuner.

I'm at a loss to explain why it would seem to work so well as a DX antenna
for 160m. Pleased, but surprised. Any theories?

Am I somehow shunt/gamma feeding my tower?

I also had no tuner arcing, no rf in the shack, no RFI in the hi-fi,
.....zippo...all the RF appears to go where I would like it to, but I have NO
idea why. I prefer to understand things and not just rejoice in my dumb
luck. Ideas?

....hasan, N0AN

On Tue, 31 Jan 2006 16:14:38 -0600, "hasan schiers"
wrote:

Necessity being the mother of invention, bit me. Last weekend was CQWW CW on
160m. I stumbled on it and had no 160m antenna. I have a terrific performer
for 80m, an inverted L with 33, 60' radials stapled on the ground. I also
have a Carolina Windom 80 at 42' fed with perhaps 100' of RG8x.

Since it was a cw contest, I figured, brute force stuff with my tuner. Very
interesting results.

I tried the 80m inverted L, feeding just the center conductor, and also
tying the shield and center conductor together ...both cases feeding it as
an end fed wire.

Hi Hasan,

You tied the shield and center conductor together - isn't that a short
circuit for the inverted L?

I got no band noise and very poor signals, but what the

Sounds like a short.

heck, I worked 10 or 15 stations who were running S7 or better in spite of
things.

Could they have been much better?

I could tell I wasn't being heard very well. (I was also running
about 500w output).

Still sounds like a short.

Then I tried the same trick with the CW-80. I fed the center conductor
only...band noise jumped up to S-3, signals were amazingly loud, and I
started working everyone I could hear...first call.

Sounds like a cleared short.

I'm at a loss to explain why it would seem to work so well as a DX antenna
for 160m. Pleased, but surprised. Any theories?

One theory is you could have done a whole lot better - but that is
pure speculation. Another theory is you could have done a whole lot
worse - that doesn't need to be proven because we can all achieve
that.

Am I somehow shunt/gamma feeding my tower?

Could be. Could be so lossy as to defy SWR too.

I also had no tuner arcing, no rf in the shack, no RFI in the hi-fi,
....zippo...all the RF appears to go where I would like it to, but I have NO
idea why. I prefer to understand things and not just rejoice in my dumb
luck. Ideas?

For one, I've seen a number of posts recently proclaim the
accomplishments of DX, Low Angle antennas. The two are not
necessarily tied at the hip. It is all predicated on the bank shot
against the ionosphere, and a low angle could as easily end up in the
drink as it could in Lower Slobovia. And Versa Vice, a high angle
(call it 30 degrees) could as easily hit Ulan Bator as it could drill
into Pike's Peak.

True, a high angle is more susceptible to multi-hop losses, unless it
is bouncing over the Pacific on the first two caroms. Without a valid
propagation model tied to the radiation distribution characteristics,
calling an antenna a low Angle, DX performer is a mighty flight of the
imagination.

Short answer: a propagation modeler tracking real time results will
answer more questions than attaching claims to simple monopoles or
dipoles.

I've used WinCAP with a highly distorted antenna response curves to
probe launch angles. WinCAP comes with sample antennas, like the
common quarter wave vertical. I've edited that file such that output
at all elevation angles, except one, are severely reduced. Basically
a one degree height elevation lobe set at one particular angle (for
the sake of argument, a 5 degree launch angle, ±½ degree). When it
reaches Europe, the footprint floods France.

Now, we know that such an antenna is nigh on impossible to build for
HF, and the common vertical is going to launch very useful power over
a far greater span of angles. The upshot of this is that instead of
that ±½ degree, we take the typical ±15 degrees around a typical
launch angle of 20 degrees, and you cover a lot of ground at the other
end * IFF * the Ionosphere will support them. And just as much power
will probably hit France even though we've quadrupled that "low"
launch angle FROM 5 degree launch angle, ±½ degree TO 20 degree launch
angle ±15 degrees.

73's
Richard Clark, KB7QHC

Hi Richard,

Of course, when the inverted L was fed with both shield and center conductor
shorted, that is a short. But I also tried feeding just its center
conductor..and it was poor, as it should have been. I'm not saying that the
CW-80 center conductor only, brute force tuned was a great antenna, just way
better than I had any right to expect. It's not like 160 is like 10m, where,
when the band is up, nearly anything works. 160 is notorious for exposing
poor antennas.

In any case, without a legitimate reference antenna, I am limited to "how
well do I get answered and at what distance" analysis and that's what I
tried to provide.

A test I would like to do sometime is to get a KW-80 trap, put it on the end
of the 80m L and extend the wire out for 160m resonance. Then I would have a
2 band inverted L and that would be a reasonable reference antenna. What has
kept me from this is I had a hard time finding the KW-80 traps...they were
out of stock. My other concern is since the 80m inverted L works so well, I
don't want to do anything to ruin its performance. (It's also hard to get
motivated to go out and do the raising and lowering and tuning in the middle
of winter, yet if I don't do that, there won't be much I can do to evaluate
the trap's effect on either band.

I was trying to get "something" for nothing with the CW-80 trick, and
succeeded beyond my wildest expectations. Nothing about my situtation could
allow anyone to duplicate what is happening here. Too many variables. I just
got dumb lucky, and THEN I get curious. I still think this arrangement
should not work very well, and that just isn't the case. The goal was to get
on the contest and make contacts as if I had a "good" antenna. Anyone who
does contesting knows what a "good" antenna feels like as you call stations
and listen to those being called. It is so easy in a very few minutes in a
busy contest to accurately conclude: this antenna is crap. I couldn't do
that and was mystified as to why not.

Either this antenna was working as some sort of kludgey inverted L or
somehow the tower was getting excited, or both. Whatever set of fortunate
circumstances obtain, if I were to have put up a "proper" antenna for 160
and gotten the results I did (and if those results were/are repeatable), I
would have said, "This thing works pretty well." I then became very curious,
and that is all. As you noted, without a reference antenna, a real
assessment is impossible. However, how the antenna performed on the air in a
situation that is well understood (contest environment) made for some raised
eyebrows on my part. Rarely does "loading up what is laying around" work. In
this case it did. Antennas and propagaton obey the laws of physics. I'm just
wondering which ones apply and in what manner for this particular
"arrangement".

I'm left with the question, just "what kind of an antenna" is this, or does
it "resemble", that would perform as well as it did.

Radio signals and how they propagate still resemble "magic" at times, yet no
one in their right mind would build the mess I was brute forcing my RF into,
nor would I recommend it. At the same time, if one just "has" to get on the
air in a hurry, my experience might prove useful. If there is one thing I
learned from this it is don't dismiss something out of hand without trying
it (if there is an urgent need). You may get surprised. Then if it works
well, try to explain it later (if you are curious...and I am.)

Thanks for your comments.

73,

....hasan, N0AN
"Richard Clark" wrote in message
...
On Tue, 31 Jan 2006 16:14:38 -0600, "hasan schiers"
wrote:

Necessity being the mother of invention, bit me. Last weekend was CQWW CW
on
160m. I stumbled on it and had no 160m antenna. I have a terrific
performer
for 80m, an inverted L with 33, 60' radials stapled on the ground. I also
have a Carolina Windom 80 at 42' fed with perhaps 100' of RG8x.

Since it was a cw contest, I figured, brute force stuff with my tuner.
Very
interesting results.

I tried the 80m inverted L, feeding just the center conductor, and also
tying the shield and center conductor together ...both cases feeding it as
an end fed wire.

Hi Hasan,

You tied the shield and center conductor together - isn't that a short
circuit for the inverted L?

I got no band noise and very poor signals, but what the

Sounds like a short.

heck, I worked 10 or 15 stations who were running S7 or better in spite of
things.

Could they have been much better?

I could tell I wasn't being heard very well. (I was also running
about 500w output).

Still sounds like a short.

Then I tried the same trick with the CW-80. I fed the center conductor
only...band noise jumped up to S-3, signals were amazingly loud, and I
started working everyone I could hear...first call.

Sounds like a cleared short.

I'm at a loss to explain why it would seem to work so well as a DX antenna
for 160m. Pleased, but surprised. Any theories?

One theory is you could have done a whole lot better - but that is
pure speculation. Another theory is you could have done a whole lot
worse - that doesn't need to be proven because we can all achieve
that.

Am I somehow shunt/gamma feeding my tower?

Could be. Could be so lossy as to defy SWR too.

I also had no tuner arcing, no rf in the shack, no RFI in the hi-fi,
....zippo...all the RF appears to go where I would like it to, but I have
NO
idea why. I prefer to understand things and not just rejoice in my dumb
luck. Ideas?

For one, I've seen a number of posts recently proclaim the
accomplishments of DX, Low Angle antennas. The two are not
necessarily tied at the hip. It is all predicated on the bank shot
against the ionosphere, and a low angle could as easily end up in the
drink as it could in Lower Slobovia. And Versa Vice, a high angle
(call it 30 degrees) could as easily hit Ulan Bator as it could drill
into Pike's Peak.

True, a high angle is more susceptible to multi-hop losses, unless it
is bouncing over the Pacific on the first two caroms. Without a valid
propagation model tied to the radiation distribution characteristics,
calling an antenna a low Angle, DX performer is a mighty flight of the
imagination.

Short answer: a propagation modeler tracking real time results will
answer more questions than attaching claims to simple monopoles or
dipoles.

I've used WinCAP with a highly distorted antenna response curves to
probe launch angles. WinCAP comes with sample antennas, like the
common quarter wave vertical. I've edited that file such that output
at all elevation angles, except one, are severely reduced. Basically
a one degree height elevation lobe set at one particular angle (for
the sake of argument, a 5 degree launch angle, ±½ degree). When it
reaches Europe, the footprint floods France.

Now, we know that such an antenna is nigh on impossible to build for
HF, and the common vertical is going to launch very useful power over
a far greater span of angles. The upshot of this is that instead of
that ±½ degree, we take the typical ±15 degrees around a typical
launch angle of 20 degrees, and you cover a lot of ground at the other
end * IFF * the Ionosphere will support them. And just as much power
will probably hit France even though we've quadrupled that "low"
launch angle FROM 5 degree launch angle, ±½ degree TO 20 degree launch
angle ±15 degrees.

73's
Richard Clark, KB7QHC

On Wed, 1 Feb 2006 07:00:50 -0600, "hasan schiers"
wrote:

Hi Richard,

Of course, when the inverted L was fed with both shield and center conductor
shorted, that is a short. But I also tried feeding just its center
conductor..and it was poor, as it should have been. I'm not saying that the
CW-80 center conductor only, brute force tuned was a great antenna, just way
better than I had any right to expect. It's not like 160 is like 10m, where,
when the band is up, nearly anything works. 160 is notorious for exposing
poor antennas.

Hi Hasan,

Maybe I just cannot visualize this. The inverted L is fed at the
bottom (at ground level) of a vertical rising wire that at some
distance up meets a horizontally running wire (or the same wire just
takes a horizontal bend out). It is fed with a coax whose shield
connects to a radial field (this is how I am interpreting your
antenna's description that I read, perhaps this is in error).

You also have an OCF Dipole that you have played with, but both
descriptions are woven so tightly together I will try to sort out the
jumble of descriptions.

All former connections remain as they were, but what I read next is
that

1) at the feed point you short the coax center conductor to shield,

OR

2) you short the coax center conductor to shield in the shack.

If (1), then that is simply a dead short which is confirmed by your
report "I got no band noise and very poor signals"

If (2), then you have a lot of RF being pumped directly into the
ground as per your description " My coax runs underground" and you
have left unsaid what you use for ground in the shack.

You also have an OCF Dipole fed with another coax (another
presumption). You feed this:

1) in the conventional way, as a dipole;

2) just with the center conductor (against shack ground?);

3) both the center conductor and shield (against shack ground?).

(1) results in no particular performance to write home about;

(2) or (3) presents far more DX opportunities and clearly more signal
than (1).

In any case, without a legitimate reference antenna, I am limited to "how
well do I get answered and at what distance" analysis and that's what I
tried to provide.

Try using a buddy who monitors you and the DX stations.

A test I would like to do sometime is to get a KW-80 trap, put it on the end
of the 80m L and extend the wire out for 160m resonance.

Reasonable plan.

Then I would have a
2 band inverted L and that would be a reasonable reference antenna. What has
kept me from this is I had a hard time finding the KW-80 traps...they were
out of stock. My other concern is since the 80m inverted L works so well, I
don't want to do anything to ruin its performance.

By your description, you already have a solution. There is unlikely
to be a better one than:

I was trying to get "something" for nothing with the CW-80 trick, and
succeeded beyond my wildest expectations. Nothing about my situtation could
allow anyone to duplicate what is happening here.

Strictly speaking, yes. However, the general solution you stumbled
across is fairly typical advice here - if we are speaking of the OCF
Dipole being fed with its elements shorted (or otherwise one half of
it as you seem to see it).

The only improvement I would see is to break the OCF Dipole's coax at
ground level and feed THAT shorted together with the coax coming from
the shack (the newly broken end). Attach the short to the center
conductor, and the shield of the coax from the shack going to the
ground field. When you want to use the OCF Dipole in the conventional
way, open the short, remove the ground and connect in the conventional
way. This could be reduced to a couple of switches at ground level.

Otherwise, what I see in the (2) - (3) OCF Dipole feed situation
above, is that you are also feeding a massive, lossy capacitor
(ground) along the way to the OCF Dipole. The (2) - (3) OCF Dipole
feed situation is simply a top loaded vertical which may enjoy some
harmonious relation with the tower in proximity.

Another possibility arises from the tower. If it is guyed, insulate
the guys about 1/3 their length down from the top, but make sure they
are connected at the top (Top Hat). Feed with a gamma match against
your ground field. The gamma wire will probably trace the same path
as your OCF Dipole line (2 to 5 feet out from the tower) and you will
need a few hundred picofarads to tune.

73's
Richard Clark, KB7QHC

Richard, thanks for your patience. I'll try to be more concise, as it is
much simpler than the comments we've exchanged so far.

I tried 2 antennas in different configurations:
================================================== ===================
1. Feeding the center conductor of the Inverted L. Coax runs underground 50'
or so, then connects to my radial plate/coax connector. That arrangement
stunk. Band noise S-0, strong signals S-7. Worked about 10 or 15 stations..
Lots of calls unanswered. VERY PREDICTABLE, a poor performer to be sure.

2. Feeding the Inverted L conventionally...same result as 1 above. Perfectly
predictable.

3. Shorting the Coax at the shack end and feeding as a random wire
.....stupid idea...dead short....I didn't even load it, there were no signals
to listen to, OF COURSE. (You have to understand, I was in a hurry and not
thinking very clearly.)

END OF Inverted L Experiment.
================================================== =============
Begin CW-80 Experiment: (OCF Dipole with Line Isolator) up 42'. 85' one
side, 51 feet other side.

CW-80: 50' underground coax, then about 45' of vertical coax to the
feedpoint of the CW-80 (OCF)

1. I did not feed it conventionally, as I didn't want to chance heating up
the "Line Isolator" located 22' below the feedpoint of the OCF. In other
words, I didn't just plug the CW-80 coax into the tuner and try to tune it
up on 160. I was afraid this might cause the "Line Isolator" to fry (the one
located 22' below the feedpoint of the CW-80)....that is how the CW-80 is
constructed...it comes with the line isolator, and you attach your coax to
the line isolator. Shack Coax, abt 95' Line Isolator 22' Coax
Feedpoint.

50' of the 95' from the shack to the "Line Isolator" is underground in a
plastic pipe (along with 3 or 4 other coax cables)

2. Fed the center conductor of the shack end of the coax as a "random wire".
I just pushed the center conductor into the coax connector on the back of
the antenna tuner and made sure the shell was not connected to the tuner.

The worked rather well, as my description earlier details. I'd call this
combo a winner. As I said in my prior post, if I had built an antenna to
work on 160 and got the results I am getting with this option, I would have
concluded that I had a "good" antenna. (For the real estate in use)

3. Shorted the center conductor to the shield and fed that to my tuner
center conductor output as a random wire. (Thus using both the shield and
the center conductor in parallel as a "random wire". This configuration did
not work any better (and perhaps slightly less band noise) than solution 2
above.)
================================================== ================
The full layout of the tower and two wire antennas:

Tower is 48'. At 46' or so, I have a 10' metal horizontal cross boom for
pulleys (see below) At 50' I have a 6 element log periodic for 13-30 mhz. at
60' I have a dual band homebrew J-Pole for 2/70cm. So the total vertical
height is about 65', with whatever loading the LP has. The LP only has a 14'
boom.

So, I have a 48' tower with a 10' cross boom at the top section holding a
pulley on each end. One pulley has the CW-80 OCF feedpoint on it with coax
hanging down 5' away and parallel to the tower, to ground level where it
goes into the pipe, underground for about 50' to the shack.

The other pulley on the other side of the cross boom holds up my 80m
inverted L...about 42' vertical and then a sloping wire to complete its
proper length for 80m. (about 25' or so). Its feedpoint is about 6" above
ground level above a radial plate with 33, 60' radials made of #14 THHN
(insulated) wire, stapled to the lawn. The vertical wire is about 5' away
and parallel to the tower (on the opposite side of the tower from the CW-80
OCF.

Hopefully, this clears things up.

The only experiment I'm left with is adding a KW-80 80m trap to the 80m
inverted L and then adding sufficient wire to get resonance on 160. I take
from your prior comments that you don't think this arrangement will work any
better than the "dumb luck antenna" I stumbled into. I'm inclined to agree,
as the 42' vertical section of the Inverted L isn't all that great for
160...but one never knows.

I just don't want to compromise the current performance of the 80m Inverted
L...it is doing a wonderful job on 80m. I worked England on cw and S92RI in
Sao Tome & Principe Is.on SSB, first call. (West Africa). Making repeated
observations comparing the CW-80 (conventional feed) and the Inverted L has
shown the Inverted L receive strength about 2 S-units better on paths beyond
1000 or 1500 miles. On real DX paths, the Inverted L is quite a bit stronger
than the CW-80. Of course, the noise level on the Inverted L is higher than
on the CW-80...all the time. It is rare that I have to listen on the CW-80
and Transmit on the Inverted L....but it has happened. This inverted L
project has been one of my most enjoyable projects in ham radio in years.
Measuring the input Z as I went from 0,2,4,8,16,26,33 radials was a rush, as
was running 2:1 vswr bandwidth changes with each radial increment increase.
The results were downright text book! Falling input Z, decreasing 2:1 vswr
bandwidth as radials were added. Nice predicatable slope.

When Reg gave me his rule of thumb equation for radiation resistance of an
inverted L, that allowed me to begin calculating efficiency based on
feedpoint Z...further fun. And, to compliment Reg, I found two other sources
for the calculation of Rrad of an inverted L and they both agreed with Reg
within an ohm (about 25.4 ohms predicted)...although their formula was
different. Reg must have some sort of magic reference library, or he has
made a bajillion measurements. No matter, his formula worked and was
confirmed by two other sources. So far, I've been able to lower my input Z
to about 29 ohms, so my efficiency (I know... a crude measurement at best,
but better than nothing) is 25.4/29 or 87%. I'll be adding an additional 17
radials when weather and motivation improve, for a total of 50 radials. I'm
not expecting any real improvement in performance, but I have the wire, I
have the plate, I have the ss hardware, and I have the lawn staples. If I
break 90%, I'll be very surprised.

Again, thanks for taking the time to chat about my two projects.

73,

....hasan, N0AN

Very clear this time - - thanks for your effort to describe it in detail.
I'm curious about the lawn staples - - could you describe them - - material,
length, source, price - - Thanks.
Chuck W6PKP

"hasan schiers" wrote in message
...
Richard, thanks for your patience. I'll try to be more concise, as it is
much simpler than the comments we've exchanged so far.

I tried 2 antennas in different configurations:
================================================== ===================
1. Feeding the center conductor of the Inverted L. Coax runs underground
50'
or so, then connects to my radial plate/coax connector. That arrangement
stunk. Band noise S-0, strong signals S-7. Worked about 10 or 15
stations..
Lots of calls unanswered. VERY PREDICTABLE, a poor performer to be sure.

2. Feeding the Inverted L conventionally...same result as 1 above.
Perfectly
predictable.

3. Shorting the Coax at the shack end and feeding as a random wire
....stupid idea...dead short....I didn't even load it, there were no
signals
to listen to, OF COURSE. (You have to understand, I was in a hurry and not
thinking very clearly.)

END OF Inverted L Experiment.
================================================== =============
Begin CW-80 Experiment: (OCF Dipole with Line Isolator) up 42'. 85' one
side, 51 feet other side.

CW-80: 50' underground coax, then about 45' of vertical coax to the
feedpoint of the CW-80 (OCF)

1. I did not feed it conventionally, as I didn't want to chance heating up
the "Line Isolator" located 22' below the feedpoint of the OCF. In other
words, I didn't just plug the CW-80 coax into the tuner and try to tune it
up on 160. I was afraid this might cause the "Line Isolator" to fry (the
one
located 22' below the feedpoint of the CW-80)....that is how the CW-80 is
constructed...it comes with the line isolator, and you attach your coax to
the line isolator. Shack Coax, abt 95' Line Isolator 22' Coax
Feedpoint.

50' of the 95' from the shack to the "Line Isolator" is underground in a
plastic pipe (along with 3 or 4 other coax cables)

2. Fed the center conductor of the shack end of the coax as a "random
wire".
I just pushed the center conductor into the coax connector on the back of
the antenna tuner and made sure the shell was not connected to the tuner.

The worked rather well, as my description earlier details. I'd call this
combo a winner. As I said in my prior post, if I had built an antenna to
work on 160 and got the results I am getting with this option, I would
have
concluded that I had a "good" antenna. (For the real estate in use)

3. Shorted the center conductor to the shield and fed that to my tuner
center conductor output as a random wire. (Thus using both the shield and
the center conductor in parallel as a "random wire". This configuration
did
not work any better (and perhaps slightly less band noise) than solution 2
above.)
================================================== ================
The full layout of the tower and two wire antennas:

Tower is 48'. At 46' or so, I have a 10' metal horizontal cross boom for
pulleys (see below) At 50' I have a 6 element log periodic for 13-30 mhz.
at
60' I have a dual band homebrew J-Pole for 2/70cm. So the total vertical
height is about 65', with whatever loading the LP has. The LP only has a
14'
boom.

So, I have a 48' tower with a 10' cross boom at the top section holding a
pulley on each end. One pulley has the CW-80 OCF feedpoint on it with coax
hanging down 5' away and parallel to the tower, to ground level where it
goes into the pipe, underground for about 50' to the shack.

The other pulley on the other side of the cross boom holds up my 80m
inverted L...about 42' vertical and then a sloping wire to complete its
proper length for 80m. (about 25' or so). Its feedpoint is about 6" above
ground level above a radial plate with 33, 60' radials made of #14 THHN
(insulated) wire, stapled to the lawn. The vertical wire is about 5' away
and parallel to the tower (on the opposite side of the tower from the
CW-80
OCF.

Hopefully, this clears things up.

The only experiment I'm left with is adding a KW-80 80m trap to the 80m
inverted L and then adding sufficient wire to get resonance on 160. I take
from your prior comments that you don't think this arrangement will work
any
better than the "dumb luck antenna" I stumbled into. I'm inclined to
agree,
as the 42' vertical section of the Inverted L isn't all that great for
160...but one never knows.

I just don't want to compromise the current performance of the 80m
Inverted
L...it is doing a wonderful job on 80m. I worked England on cw and S92RI
in
Sao Tome & Principe Is.on SSB, first call. (West Africa). Making repeated
observations comparing the CW-80 (conventional feed) and the Inverted L
has
shown the Inverted L receive strength about 2 S-units better on paths
beyond
1000 or 1500 miles. On real DX paths, the Inverted L is quite a bit
stronger
than the CW-80. Of course, the noise level on the Inverted L is higher
than
on the CW-80...all the time. It is rare that I have to listen on the CW-80
and Transmit on the Inverted L....but it has happened. This inverted L
project has been one of my most enjoyable projects in ham radio in years.
Measuring the input Z as I went from 0,2,4,8,16,26,33 radials was a rush,
as
was running 2:1 vswr bandwidth changes with each radial increment
increase.
The results were downright text book! Falling input Z, decreasing 2:1 vswr
bandwidth as radials were added. Nice predicatable slope.

When Reg gave me his rule of thumb equation for radiation resistance of an
inverted L, that allowed me to begin calculating efficiency based on
feedpoint Z...further fun. And, to compliment Reg, I found two other
sources
for the calculation of Rrad of an inverted L and they both agreed with Reg
within an ohm (about 25.4 ohms predicted)...although their formula was
different. Reg must have some sort of magic reference library, or he has
made a bajillion measurements. No matter, his formula worked and was
confirmed by two other sources. So far, I've been able to lower my input Z
to about 29 ohms, so my efficiency (I know... a crude measurement at best,
but better than nothing) is 25.4/29 or 87%. I'll be adding an additional
17
radials when weather and motivation improve, for a total of 50 radials.
I'm
not expecting any real improvement in performance, but I have the wire, I
have the plate, I have the ss hardware, and I have the lawn staples. If I
break 90%, I'll be very surprised.

Again, thanks for taking the time to chat about my two projects.

73,

...hasan, N0AN

On Wed, 1 Feb 2006 12:59:11 -0600, "hasan schiers"
wrote:

================================================= ====================
1. Feeding the center conductor of the Inverted L. Coax runs underground 50'
or so, then connects to my radial plate/coax connector. That arrangement
stunk. Band noise S-0, strong signals S-7. Worked about 10 or 15 stations..
Lots of calls unanswered. VERY PREDICTABLE, a poor performer to be sure.

2. Feeding the Inverted L conventionally...same result as 1 above. Perfectly
predictable.

Hi Hasan,

You say the Inverted L works on 80, so we will leave that alone.

END OF Inverted L Experiment.
================================================= ==============
Begin CW-80 Experiment: (OCF Dipole with Line Isolator) up 42'. 85' one
side, 51 feet other side.

CW-80: 50' underground coax, then about 45' of vertical coax to the
feedpoint of the CW-80 (OCF)

1. In other
words, I didn't just plug the CW-80 coax into the tuner and try to tune it
up on 160. I was afraid this might cause the "Line Isolator" to fry (the one
located 22' below the feedpoint of the CW-80)

Aside from the odd tail (the drop to the choke), yes you do stand a
real chance of Common Mode current due to the deliberate imbalance
(the Off Center of the OCF Dipole).

However, when you are driving both sides shorted (or even just one,
singly), the choke is going to be engaged and become a loss (this may
be one reason why it matches well). This is the nature of choking
afterall. If it is built to present enough Z in the 160M band, it
could even disconnect the top hat (but that is not what you are
reporting). Something about the "Line Isolator" seems to lack a
choking action (which further suggests it doesn't choke and it doesn't
isolate).

Anyway, low 160M dipoles nearly always have dismal reports here. On
the other hand, strapping both side of the driveline together and
feeding that, as you say "random wire," often brings good results if
the dipole is high enough. Low/High? and for the same height for the
same band? The kicker is one is horizontal polarization, the other
vertical. That height is too low for horizontal, but suits vertical
polarization better.

3. Shorted the center conductor to the shield and fed that to my tuner
center conductor output as a random wire. (Thus using both the shield and
the center conductor in parallel as a "random wire". This configuration did
not work any better (and perhaps slightly less band noise) than solution 2
above.)

Perhaps because with a hot shield, and ground so close for so great a
distance....

================================================= =================
The full layout of the tower and two wire antennas:

Tower is 48'. At 46' or so, I have a 10' metal horizontal cross boom for
pulleys (see below) At 50' I have a 6 element log periodic for 13-30 mhz. at
60' I have a dual band homebrew J-Pole for 2/70cm. So the total vertical
height is about 65', with whatever loading the LP has. The LP only has a 14'
boom.

Sounds like a perfect platform for a top loaded 160M vertical. Take a
cue from your recent success with that polarization and work with what
nature has given you.

Hopefully, this clears things up.

The only experiment I'm left with is adding a KW-80 80m trap to the 80m
inverted L and then adding sufficient wire to get resonance on 160. I take
from your prior comments that you don't think this arrangement will work any
better than the "dumb luck antenna" I stumbled into. I'm inclined to agree,
as the 42' vertical section of the Inverted L isn't all that great for
160...but one never knows.

It's a 1/16th wave tall (or a quarter of a quarter), but top loading
will boost that to maybe 1/12th wave tall - still no great shakes.
However, experience has shown you were surprised with a "dumb luck
antenna" that has no more advantage in height. Thus it follows that
even as short as that still brings reward.

The long and short of it is that there is probably little to gain (pun
intended) with more work. I would still suggest moving the feed point
away from the back of your tuner, and:
The only improvement I would see is to break the OCF Dipole's coax at
ground level and feed THAT shorted together with the coax coming from
the shack (the newly broken end). Attach the short to the center
conductor, and the shield of the coax from the shack going to the
ground field. When you want to use the OCF Dipole in the conventional
way, open the short, remove the ground and connect in the conventional
way. This could be reduced to a couple of switches at ground level.

The absolute long and short of it is: "don't look a gift horse in the
mouth."

73's
Richard Clark, KB7QHC

Hi Chuck,

The lawn staples are from DX Engineering (as was the beautiful radial plate
with bulkhead coax connector).
They are about 6 inches long, a rectangle, maybe 1 inch wide, and heavy
enough that you can pound them in with a hammer, as long as your soil isn't
concrete. Sold in packages of 10 or 20, I think. Quite reasonably priced. I
only have one staple per wire now (doing it in the middle of winter made me
move quickly between ice and mud patches). I'll put down a staple every 10'
or so when things dry out.

Google DX Engineering and you will find there web site. From there it's
pretty easy to find stuff.

73,

....hasan, N0AN