[TowerTalk] Re: Stray RF yes and no
K7GCO@aol.com
K7GCO@aol.com
Fri, 22 Jun 2001 17:45:31 EDT
"STRAY RF--YES & NO!"
This was sent to 23 others before to TT for their comments. No one had a
single problem with it as they had found the same things I have. I wanted
thank the others who confirmed my contentions that a lot of beam interference
from guys etc was actually and mostly from other stacked beams if too close,
RF Spill Over from bad matching systems like some badly adjusted Gamma
Matches or coax direct feed to balanced feedpoints without a balun. Symptoms
frequently gets misdiagnosed! Sometimes you get some surprises. There is a
simple way to fix or balance the affect of a gamma, however. Shift the DE
center and adjust the tip lengths and use the "K7GCO Stray RF Hand Test"--it
works contrary to those who haven't tried it. Some changed to balanced 100
ohm coax and a T Match, FD as I suggested (I may get something very useful
started here), better baluns or baluns like a 50, 100 or 160 ohm Bazooka for
balanced feed points and--the SWR change with rotation problems for one--just
went away! Isolation to SWR changes is great but may not be enough. If you
have an accurate E plane pattern of your beam from the manufacturer or Eznec,
you can at least check out the E Plane by rotating the antenna. However RF
Spill Over can still affect the H plane pattern and often not see it on the E
plane. After measuring vertical patterns for years I can assure you It can
be very evasive.
In one interference case reported to me an insulator at the tower for the
guys solved the problem--or at least part of it. Lowering the top guys 10'
solved the problem in 5 other cases. NOTE! I see absolutely no reason for
guy wires or Inverted Vees at the top of a tower anyhow. If you can't attach
the guys 10-15' below the top of the tower--your tower is too damn weak. I
don't know how this ever got started? A big 40M beam on top may be an
exception. A staggering question is, "why haven't others suggested this same
thing repeatedly"--it's so "incredibly obvious." So many bad practices like
this get started and too many follow like sheep over a troubled cliff that
even the TT Reflector has trouble handling. Those trying to redirect the
traffic with "new practices" away from the cliff edge often get ridiculed to
oblivion also. Progress is often made "One Death At A Time."
Stray RF can certainly do it's damage to F/B ratios if just right. However
it can be controlled and even ignored at times as the reports continue to
come in who followed my instructions. Actually nulls more than 30-40 dB have
"no legitimate reason for existence anyhow." They are usually in a real
narrow slot, very difficult to use anyhow and are inserted into patterns by
mother nature just so that the "RF Straw Bailers" (those who grab at stray RF
straws excessively) have something to crow about and look smart. They are
kind of like the "ACLU of RF Human Rights". Their claim they "Defend Your RF
Rights" (nulls) like no one else but there are 3 other (nulls) the ACLU
absolutely refuses to defend like the right to own guns and 2 others the
Liberals don't like. Hey that's a pretty good example if I say so myself.
I shall give a "classic example" of an "extreme case" that few thought would
be possible and apparently haven't realized it's full significance as yet.
Lucky I didn't listen to them before I started my project on a 5 and then a 6
band quad. Antenna Mart has been making all band multi element quads for
some time with great patterns. The "Stray RF Interfering Elements" in
question here are even:
1. In the same plane
2. Resonant on each side of the operating frequency
3. Of the same polarization and
4. Very close to if not optimum spacing (optimum spacing
may not be used by the main elements).
NOTE! These elements are capable of reflecting
"Major RF"--not "Stray RF."
It's a "5 band quad (20-10M) using tapered spacing (I've added 6M with a new
twist--why not)." However it uses "individual DE feed" with a remote coax
switch on the tower like Antenna Mart does--the DE's are NOT all tied
together which totally destroys the potential pattern "beyond repair" (in
Eznec and on the air) with all this "Stray and Major RF" used in the wrong
technical and financial way in business. Some manufacturers actually sell
this "Junk Stray RF Beam" to unsuspecting hams without a whimper even when
told about it. I seldom had to rotate the beam on CQ's even though a DX
station would call me on the side or back. Why hasn't any of the "Stray RF
ACLU Experts" on TT got concerned over a real "Major Case of Stray
RF--Industrial Strength??
Paul Harvey said:
"We live in a Junk Society. We have Junk Cars, Junk Houses, Junk
Books, Junk Toys, Junk Movies, Junk TV's, Junk TV Programs, Junk Furniture,
Junk Food and one city even had Junk People--they had more Suicides than
Homicides." We even have Junk Sex--it's less Emotional Satisfying and Junk
Antennas, Junk RF, Junk Radios, Junk Other Ham Equipment--on and on. They
even sell you Warranty Insurance to help pay for the eventual repair!! I
have returned the last 14 items I have purchased including 3 ham rigs with
major and expensive problems, cameras, an intermittent telephone, lenses,
guns with dangerous design flaws, an $800 Cell phone 6 years ago, a
Fax/Telephone combo on and on--junk junk junk. Some Junk Designs hang on for
years like the Gamma match. It's taken me a while to wake up but the only
way to eliminate this junk problem and wasted money is--don't buy anything.
I'll keep the 3-6M Raibeams as they are built and work great--better than I
had expected. A tight wad friend of mine who never buys anything brings this
to my attention all the time like for over 45 years. I had to admit to him
he's been right all this time. He's got over a "million trouble free bucks
in stocks and bonds I don't" and smiles a lot also.
Tom Peters used to give talks on "Making Life Time Customers" and I have his
and other books on it. It's become almost a "Forgotten Concept." There is a
concept frequently used now by many businesses where, if you get a "lemon,"
you're told "you will eat it." That's a very tough and sickening thing for a
retiree, a kid or anyone to hear with their hard earned money invested. You
couldn't get away with that years ago and still can't from some buyers. I'm
told "they often still come back" so they feel justified in doing it and the
"lemon product" is a headache for them also. I can show many proven
statistics that is "still bad very business." It still makes "Stray RF
Customers" in the Ham World. Walmart like no other Merchant has made
millions and millions forcing (ruthlessly some claim) suppliers to supply
good products at a low price. Mass sales at low profit margins has made the
"Biggest Fortunes" like for Walmart. Perhaps the Ham Dealers should do the
same. I think pressure should be put on the Junk Manufacturers of items for
resale or direct sale. Don't buy them! Don't throw your money away.
KC6T had a great article in QST where he tuned up a 5 band quad and used
series fixed and selected capacitors for the final reflector length. His
buddy did the same with a series inductor with taps. I guess the reasoning
was--it was easier to make a change in the reflector bottom wire during the
initial tune up from the roof than it was to change the entire wire length?
Regardless both got it tuned up and it still worked great after the move from
near the roof (house wiring, eve troughs and all that) to the top of the
tower-for both. How could that be?? It happens when you learn that there
are fewer design restrictions than you have been led to believe by the "False
RF Prophets." In this design the reflector was slightly larger for the
series Xc and slightly smaller with the series XL than normal when properly
tuned. This design actually used the same physical spacing on all bands with
good patterns although I will compare it to tapered spacing.
About 40 years ago Sant G2PU found that the usual open wire shorted stub used
for convenience to tune reflectors, "canted the free space H Plain Pattern
off center line" (either up or down I don't remember). Reflection Factor
plotting with the free space pattern when tipped up or down will reduce the
potential reflection 6 dB gain main lobe like over what I call "Liquid Copper"
--Salt Water. Your antenna creates the "text book nulls" in the beams
vertical pattern only over perfect ground and salt water is as close to it
you can get. Normal ground loss fills in the nulls bit more and for vertical
polarization, the even higher ground reflection losses fill in the nulls and
reduce the gain even more. The higher the frequency the worse it is for both
polarization's for the "Highly Abused and Misunderstood Null--It Gets No
Respect." However, Nulls or Dips in the pattern will put up a pretty good
fight to survive in the E-Plane I've found and have some great configurations
of beam patterns for verification. The reason all those great nulls are
shown in text books is conditions are ideal on paper. There is no RF Spill
Over on paper--it's non conductive. Would you believe that if technical
books were printed on aluminum foil, lift off of vertical patterns and
fill-in of nulls would be shown?
G2PU discovered the canting of the free space pattern when he fed his 20M
quad vertically polarized with the single reflector stub now on the side.
His pattern on vertically polarized sources "was not head on" and easy to see
on the S-Meter. So he said "enough of this design compromise total nonsense"
and took out the stub and lengthened the reflector until he got the same
pattern--head on. Then he rotated the feedpoint 90 degree back for
horizontal polarization with no tipping of the free space pattern. You can
have equal length stubs on each side for balanced but why have stubs at all?
They just flop around in the wind. After tune up they have served their
useful purpose. Add their length to the reflector.
How much difference a single stub actually makes on typical contacts would be
hard to tell for sure with other than 2 Quads side by side, one with and one
without the reflector stub. Eznec will tell the difference also at least at
the RF Starting Blocks. I'm sure it made at least an S-Unit or 2
psychological difference to listen to him tell about it although he always
had a great signal on AM with a 2 element quad on 20M. I haven't heard him
lately although he's still in QRZ. Too many design and performance
compromises are often used for convenience or to save money. Too few design
for "Maximum RF Clout" like Raibeam, Antenna Mart and M2.
Now even with no tuning stubs, no metal guys and individual feed of quad
DE's, it would still appear listening to all the "TT Stray RF ACLU Experts"
it would be totally impossible to get a 3, 5 or 6 band quad tuned up on ALL
BANDS and have good patterns with good nulls. It would seem there are just
too many stray RF generators and are too close in the wrong place. Are you
sitting down--NOTHING COULD BE FURTHER FROM THE TRUTH!! Don't you "Guys"
ever get tired of being wrong? All 5 bands (even 6) using .125 WL spacing
tuned up with great patterns and nulls with tapered and fixed spacings.
There were a couple "Unexpected Bonus." The gains increased slightly and
even the F/B in some nulls over what was possible from a monobander. It
never got worse. I reported this on TT and all the poo poers came out of the
computers with their ho ho ho's. Then Cebik bless his soul, verified what I
had found as he had found it also. The Poo Pooers were "strangely silent."
It was then he told me of KC6T who found good patterns on each of the 5
bands. He uses the same physical spacing in his design. This is what is
actually found when someone actually spends some time "tuning up beams"
instead of their "TT Shooting Gallery Opinions."
The H planes of yagi's and quads are always larger than the E plane in every
pattern I've ever seen. I have never ever seen it the same beam width except
in a Bi Square "totally unexpected bonus"quad. They get real close in 7 and
8 element yagi's. Another was this. The 6M 2 element quad inside the 5
other bands with symmetric loops--had the "Same Beamwidths." Absolutely
Incredible! This is "Pattern Black Magic." There was just too damn much
Stray RF. We just have to pass a "TT Anti-Beneficial Stray RF Law." So Be
it! It's not "Technically RF Correct." It's totally out of control in a
beneficial manner. We can't have that! Someone may have a signal edge. In
"RF Socialism" everyone has to be the same.
How could near resonant elements of a 5 or 6 band quad on each side of 3 or 4
operating frequencies be so immune to the beams pattern? It's violating too
many "TT Opinion, Appliance & Band Aid Operator Laws." Embarrassing isn't
it? Elevated Egos will never be the same.
When all the 5 band quad DE's are tied together, high levels of RF are
clearly seen on other off band-elements in Eznec and it does indeed affect
the patterns. It's so bad the 10M free space pattern even tilts down at
about 35 degrees--very grim! That's "Major Directed RF" doing this, not "TT
Stray RF."
There are many other examples I've seen that just aren't doing hardly
anything but then there are those that do like a towers affect on a
vertically polarized beam. I know all the major ones and have battled them
for years. They are clearly seen in a pattern recorder. I just found a new
one just spinning the beam that has been unrecognized even with Eznec now and
will report on it. Under "perfect conditions" I felt I had a vertically
polarized H plane pattern upset with stacked beams with certain spacings. RF
got on the separating boom of the wrong polarization. I found the reason, a
simple solution and solved the problem.
With individual DE feed of 5 or 6 band quads, some RF levels are actually
shown on off-elements in Eznec and recorded in the Current Charts. Yet great
patterns result which absolutely defy TT common misguided opinions.
I also excited the higher and lower frequency DE than Fo and great patterns
still were maintained--some even better. I was surprised myself but I dig
into areas that few would think productive all the time. It blew up the
theory of resonant DE's were needed other than for a resistive feedpoint. I
had thought of feeding the quad with open wire line and this off band DE
would be reactive one way or the other depending which one was used. I felt
the Match Box could handle this from the Z's I saw and similar examples.
That's an interesting concept of feeding the off band DE and getting a great
pattern. More on this later.
It's my plan to add a "new performance wrinkle" to an all band 2 element quad
by adding variable Xc's in each reflector all ganged together to a selsyn on
the mast so I can tune for max F/B or Gain anywhere in any band on all bands.
I'll determine the free space pattern cant if any of the H Plain in Eznec
and tilt the boom accordingly to compensate. There are little tricks away
and around some problems and in some cases certain levels of "The Dreaded
Stray RF Isn't All That Bad" even right in the bedroom under the sheets so to
speak. If you learn how RF really flows when and where, what different
levels do, you can learn how to talk to RF figuratively speaking--it will
behave.
I'll feed this quad with 100 ohm balanced coax into a match box in the shack
which will assure max RF into the coax input and anywhere in the band with
whatever the configuration is used. That could be considered a very useful
feature--in particular in a contest and no beam has it yet. Although guy
wires are out of the main plane, often non resonant, of the wrong
polarization, spacing and sometimes in a pattern null, I'll run some guy wire
stray RF tests in the pattern and SWR curve when I rotate it just to ease my
and other's curiosity in case they ask--or demand. I leave no RF Stones and
RF Burns unturned. A lot of all this was determined, observed and made use
of by many even long before Eznec so little of this is really new info.
While I'm on a roll here I really like 1/2 wave verticals whenever possible
in particular on 40M and on up for many reasons. I've had a couple of
articles on these 1/2 waves in CQ some 35 years ago. All these radial
problems go away although a screen around the base when close to the ground
has been known to help--even at WWVH. If the base is high enough the ground
screen could probably be done away with. I'll try it with and without. I
use 1/2 waves with an another unusual but simple design now on top of
monobanders for "listening antennas" as my F/B patterns are so good on some
beams (even with stray RF guys) I'd miss a lot of stations off the back and
side without the 1/2 wave vertical to switch to. I can run them together
with different phasings. It often does great just by itself. I've used 1/4
wave verticals over the beams DE also as the radials. Why this hasn't caught
on I'll never know.
I have a 6M 1/2 wave on the roof now for monitoring. The 6M Raibeam 5
element "Butt Kicker" I have 30' higher has such a good F/B/Side (even with
2-6M beams below it), I needed the 1/2 wave vertical for monitoring. When
an opening occurs on 6M you don't want to miss it from any direction and it
can be weak. NOTE! If certain of my or the 5 element Raibeams unusual
F/B/Side ratio's wasn't as good as it is, I wouldn't need the 1/2 wave
monitoring vertical. Apparently many have never had a beam with exceptional
F/B/Side!! What have you been doing all these years in advancing the state
of the art? Show me some examples. I have some that I haven't even
mentioned yet.
There is a "reverse concept" I have observed. I've told of the 10M 3 element
I have tuned for "absolute max gain of 10.2 dBi." No manufacturer has ever
tuned a beam that way. It has 8 dB F/B, narrow bandwidth and 6 ohms in the
center of the DE. The director is actually longer than the DE. I feed it in
a sneaky way at a 50 ohm feedpoint with "Absolutely No RF Spill Over." The
coax shield and center of the DE attached to the boom is "RF Stone Cold."
Would you believe that a "RF Frost" appears there after a long transmission.
Another phenomena occurs with 8 dB F/B I didn't expect. After a transmission
running legal power the back lobe clears the frequency so well it leaves a
"Signal Black Hole" for the same length of time before it fills in. That's
"Infinite F/B." In 3 years using the beam I don't remember having to repeat
anything. Contesters find this useful and have been known to have another
final on a beam pointing the other way leaving the impression or stating they
have poor F/B. Now you know. With a beam where max F/B and/or Gain can be
selected, one could also transmit with max gain and listen with max F/B.
That's a great idea.
This beam has another great advantage. With poor F/B you don't have to worry
about Stray RF filling in the nulls--it might create one--heaven forbid. It
could really silence the "Stray RF ALCU Birds" forever!
Antenna design is very interesting if you learn how to massage the RF and put
it to work for you. Few know the joy of a "fast rotator and a great beam
pattern. When you call them--they stay called." And I now have 3 ways to
cure and extend the narrow band width of this or any beam even more.
I had a 5 element 6M yagi on a 16' boom 10' below this 10M beam and when
installed it didn't change the SWR a bit of either one. The vertical
patterns of each and the very tight max gain coupling between the 10M
elements apparently really isolated it from the 6M beam. Both worked great.
I worked KE6IHA on 6M using a Cush Craft Ringo vertical that is really an
"Extended Double Zepp" of 3 dB gain design like their 2M Ringo. Running 700W
he has worked a lot of DX on 6M using it much to my surprise. That's one of
the few reports I've had of this although I know very well what 1/2 waves
will do on all bands--except 6M. This caught my immediate attention. I've
only heard JA's for DX 2 years ago on 6M once although they were coming into
Seattle last week and I missed them. My 1/2 wave will be mounted on top of
the 5 element Raibeam shortly. I want to see how well it will work up there
at any distance on 6M. I will then make my version of the 6M Ringo. The
Ringo is actually a very poor design. The ring at the base is really the
inductor of a tank circuit to match a Hi-Z at the end of the antenna and
tapped at the 50 ohm point. But it has the highest RF Spill Over down the
mast of any vertical in Ham radio. The higher you mount it the worse it
works as more of the lift-off of the vertical pattern occurs. The mast or
tower is heavily excited like a long wire and dominates. When the 2M AEA
Isopole came out with the double radial skirt to kill RF Spill Over once and
for all, Ringo added radials below the Ring Tank Circuit. Unfortunately they
didn't understand exactly what they were doing and trying to copy it, added
radials 1/8 WL lower and not 1/4 WL lower at the maximum high voltage and
Hi-Z area where they are the most effective as "RF Spill Over Killers." They
were close but "No Cigars." When I told them "they missed by 1/8 wave,"
their eyes rolled. I don't think they understood what I said as they didn't
change it.
A local Marine Antenna Manufacturer has a similar "pattern lift off problem"
with a the 156 MHz vertical and don't know why. These pattern lift off
problems created by "Major Stray RF" are still virtually "Best Kept Secrets."
The previous owners had stolen an antenna design from me and it had RF Spill
Over they didn't know how to stop and had then had the guts to ask me how! I
will offer a solution to the new owners for a respectable fee. I applied the
fix to one of their type antennas that can't be seen on the outside, will
demonstrate and then we will negotiate. I hope I get out of there alive and
with some folding stuff.
The Ringo, the 2 Marine verticals and several others including some Ham
verticals on the market are really nothing more than:
"50 ohm matching devices for the coax to the mast."
"So it can be seen that 1:1 SWR is not the full picture in
evaluating an antenna with or without Stray RF but
it's a good place to start."
It's like kissing on the hand--you have got to start some where!
The frequently neglected, hard to measure and evasive vertical pattern is
very important. The key to performance is seen mostly in the free space
vertical pattern--is it at 0 degrees or on the horizon? Learn how to
evaluate and control it once mounted on a tower. Dominate signals can be the
result. You may be accused of running big power. I know the feeling.
Record the weak DX station and play it back or point out "you hear the weak
ones better than they do or not at all." Sometimes they will call you from
across town (and across the country) to see if you are talking to yourself.
They "Absolutely Fry in Their Frustrations" hearing on the phone what they
don't hear. Bill Wall has had that happen using his quads. That's a big
clue you have got an unusual beam. Unfortunately few will ask how it is
done? They will ask about the receiver and seldom about the antenna?
Another clue of Stray RF and beams too close to each other is RF in the
Shack. If Compression is used on SSB Stray RF there can easily get into the
audio in some rigs. This usually happens when no balun is used.
Summation: All Stray RF isn't all that bad as some have claimed. If it
was the 6 band 2 element quad wouldn't be possible. Proper design does
reduce it as much as possible.
I've covered most of bases in this post to suppress most of the nit pickers.
I did add something a sharp nit picker could jump on. Let's see if any of
them catch it? I put something in for everybody. K7GCO
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