Topband: Lab style comparison results on 160m small lot antenna changes.

[Guy Olinger K2AV]

A prior poster, lamenting the nature of FCP success reports, wrote:

"Who has done that, with only a radial change, against an unchanged
reference antenna that is in the far field of the antenna under test.
 [Where's the post with the details] ?"

Perfectly logical question.  We all would like that answered with posts
listing lab grade experiments.  But, after experiencing what goes on
converting to an FCP in constrained circumstances first hand, and hearing
quite a number of stories including failed attempts to come up with those
comparative figures, this is what's happening out there where one might
expect posts would be generated.

Short Version:

1) Most activity not via TopBand reflector to start with.
2) Reluctant to post to TopBand reflector.
3) Only room for one antenna at a time.
 4) Working state of old and new antennas separated by weeks or months.
5) Adequate test equipment to deal with 3) and 4) not owned.
6) If there's (rare) room for two antennas, defeated by interaction.
7) Installers are advised to remediate all sources of loss.
8) A test to isolate dB's from radial removal not a priority out there.
9) RBN is free, all skywave, unbiased, and remarkably useful.
 10) Many times anecdotal evidence is all we are going to get, period.

Long Version:

1) Most activity not via TopBand reflector to start with.

This is not a dig at TopBand reflector at all.  It's just that in general,
results are not likely to be posted to TopBand reflector, nor anywhere
else.  Nearly all FCP activity takes place out of  the reflector sphere,
never mentioned here.  FCP didn't start on TopBand reflector.  It never got
mentioned here until after we had stuff clearly working.    NCJ article was
requested independently.  Top Band just isn't the channel for it, that's
all.

The web page is busy. Most web hits are outside the U.S.  For the last
three months, Jack has had a cute world map counter on the page:
http://www4.clustrmaps.com/counter/maps.php?url=http://www.w0uce.net

FCP circulation is nearly all by word of mouth out there, using W0UCE's web
page and its links as a reference.  I get some small percentage in email
asking for assistance, which is my prime source of what is going on.  I get
people in contests saying TNX FCP, very few I recognize from any of my
usual haunts, including here.

2) Reluctant to post to TopBand reflector

I will not post information I have directly from others without permission.
 Nearly all requests I have made in the past for an FCP installer to post
results to TopBand reflector were refused or ignored.  I don't ask anymore,
it gets in the way.  For whatever reason one might argue, that's an issue.
 If they post, they post.  If they don't, they don't.  So far, the odds
seem against it.  Guys are not putting up FCP's to prove points in a
technical argument, they're doing it to work people.  For them working
people they never could before equals success, however much some here may
frown on that.

So the odds are well down on getting a given post over here before we even
start in on issues of difficulty.

3) Only room for one antenna at a time.

These situations are on the other end of  the spectrum from the big guys
with all the acreage.  It's an art form getting up a working 160m antenna
in a 21' x 75' backyard with only a 29'  tower to support the bend.  There
will NOT be two antennas side by side to compare.  Forget antenna switch
A/B tests.  You either have antenna A strung up out there or you got
antenna B strung up, not both.  This is the practical situation almost
everywhere.

4) Working state of old and new antennas separated by weeks or months.

Only one antenna up at a time leads to a practical comparison conundrum,
where the original antenna system has to be measured by whatever method
BEFORE being torn down, or adjusted, or whatever, and then RE-measured by
the same stable, unchanged equipment and method AFTER everything is done to
erect and tune up the new one.  Since this interval often is weeks or
months, or one case I know approaching a year,  very stable methods and
equipment are required to do an accurate far field comparison.

5) Adequate test equipment to deal with 3) and 4) not owned.

Adequate test equipment for shelf life stability and repeatability is
pretty rare among hams.  All of us would love to be dreadfully wrong about
affordability of something good enough for 3) and 4).

The common field strength stuff one sees like an MFJ801 or the equivalent
doesn't cut it.  The sensitivity pot alone disqualifies these types.  I've
used an off brand equivalent of the MFJ with a time split on the SAME DAY,
with the range pot knob immobilized by tape.  That worked just fine for
tuning a particular antenna to maximum smoke.   But if it had to sit around
for months, I wouldn't trust the pot to be at the same resistance, even if
the knob had not been touched or jostled.

And anyway the conversion to dB is uncertain from a difference on an
inexpensive diode detector meter with a linear scale from 0 through 10.

Need higher grade stuff with ranges, V/m, mV/m, uV/M, 3.5 digits, features
like hold average or hold peak, digital display, and above all stability
and repeatability off the shelf after periods of non-use.  Decent absolute
accuracy would sure be nice, but stability and accurate relationships
between ranges is the killer issue.

Expecting Joe Average FCP Installer to have one of those?  Don't hold your
breath.

[I'm thinking of springing for a professional tunable FSM, gak.
Recommendations from those who have tried and lived with them all would be
appreciated.  None of my rube goldberg alternative procedures around here
(to keep from buying said pro FSM) have been good enough to trust quoting
mV/m.  Reapeatability over time on an unchanged antenna was not to be had.

6) If there's (rare) room for two antennas, defeated by interaction.

For some in the rare spot of having physical room to put up two 160m TX
antennas, most often they still had to remove the old antenna, anyway due
to destructive interactions, sometimes to allow the FCP version to tune up
at all.  So though the old antenna wasn't usable either way for antenna
switch comparisons.  One case of attempted comparison seen on this
reflector, where there WAS room, it still ended in a case of the
interaction blues.  He had the order of magnitude for sure, but he was not
convinced of n.x dB magnitude.

7) Installers are advised to remediate all sources of loss, right up front.

Of course they are.  Of course they do.

The point of the exercise is to improve signals. And they already have the
patient cut open.  Fix it all now. Sew it back up.  With the feedback I do
have, we are developing a "dirty dozen" list of things to absolutely go
check and fix if needed.  ALL AT ONCE.  Get it all done and over with.  The
point is PERFORMANCE, not PROOF TEXT for some concept.

Hams ARE capable of deciding themselves whether they like the results.  My
experience is they keep their own counsel.

After some ugly results out there without the isolation transformer using
various inexpensive "baluns", I had a few shipped to me which I measured
for 160 meters.  On 160m, cr*p.  Merely ugly on 80.  So those changes were
replacing insufficient radials with common mode problems with the FCP, PLUS
using the isolation transformer to remediate  the cr*p isolation from
common mode, one case moving vertical 8 feet away from the ground.

8) A test to isolate radial removal not a priority with the users.

An FCP and an isolation transformer go after two sources of loss at the
same time -- losses in the radials and, and depending on what they had,
common mode loss on the shield of the feed coax.  If it is replacing a poor
in/on ground radial system, it's going after a third source of loss,
induced loss in the ground medium from usually maximum vertical wire
current right at the ground, hence maximum induction.  This loss diminishes
significantly simply by raising the bottom of the vertical radiator up to 8.

So the number of issues being remediated could be one to three, with the
installer not really identifying which problem he had to start with, and
proper attributation of dB to various causes nearly impossible.

People go for the big bundle, first shot.  They want to put it up, make
their signal better and work people.  They're not on TopBand, don't care
about backing one or the other side of a dispute.  And then there's the
majority, moving along with nothing than the web page and their buddy's
experiences, for which I have no wide source of information.  Because of
Skype sessions with a Scottish gentleman, I get good scuttlebutt about
what's going on in GM land.  Nobody is talking about setting up lab cases.
 They want to be able to work stuff on 160.

9) RBN is free, all skywave, unbiased, and remarkably useful.

As long as an installing station has another station more or less local to
him that is not changing anything for a while, and you can transmit TEST
W6XYZ W6XYZ test strings, that's plural, over a period of time, with both
on air at  at the same time.  Do this BEFORE the modifications, then repeat
after the changes.  This will  will get you before and after relative data
on RBN that is skywave and unbiased. Numbers like this are good enough to
spot something not done right, or to see conclusively that a lot was fixed.
 Because it's free, I can ask people to just do the sending, and since
everyone has access to RBN, I can see for myself what the numbers are.
 Like I posted earlier, one can see all kinds of stuff with RBN if you know
how.

10) Many times anecdotal evidence is all we are going to get, period.

Deal with it.  An awful lot of really good food needs to be shelled,
peeled, cored, cooked, etc, to be in usable form.  One can shell, peel,
core, cook anecdotes to get very useful information out of them, without
having to chew and swallow the peel, core, shells, or eat it raw.  An
anecdote is a story, not a dataset.

We're going to get anecdotes, most of the time, nearly all the time?  If
doing field strength testing was generally interesting or popular, we would
not be having this discussion.  With demand, particularly now, comes
remarkably useful stuff like AIM4170, Elecraft XG3, other ham-priced
gizmo's that we would have killed for 20 years ago.  But where's the MFJ or
Elecraft digital FS meter?  Is there one that goes on a ham budget?   So we
are back to accepting what we get, anecdotes.  Or hopefully, better, RBN.

Anecdotes are not useless.  Determining predominance and sifting out
essential indicators will accurately get you "leans" in a given direction.
 It may look like noise, but it will tell you where the wind is blowing.  A
"rule" has a problem, if it says one thing while predominance of anecdotal
evidence says something else.  There IS something to get worked out.  The
really good, grounded rules will EXPLAIN the anecdotal material.  If both
RBN and anecdotes are leaning the same way, you can tell someone to do
something and results will get better.

Which of these sound like six dB?  You are installing FCP and isolation
transformer.  All are assumed at equal power levels if two transmitters are
implied.

   a) You live on the east coast of US. Your New Mexico buddy says your
signal is "really not very loud".  He says Station X about 90 miles north
of you is a "beacon".  After changes, you're up there in "X's
neighborhood".

   b) From GM land, "Before I could barely hear the guys in 9A, much less
work them.  Now they give me S9."

   c) From W6 land.  "Before, for years I could never work east of the
Mississippi.  Now I'm working Europe and Maine to Florida."

   d) They tell me not a huge change, maybe I'm up an S unit.

   e) Before the changes,  Jerry's RBN signal average over the evening at
NY3A was 32.  Mine was 18.  Tonight with the new stuff, Jerry's was 26 and
mine was 23.  You can see the parallel data lines and their separation in
the RBN spot analysis tool.  What your eye tells you about the curves
matches the math.

   f) "You're a little bit louder, but not so much." (Not an S meter
reading)

Answers:

a)  You hit the jackpot.  Don't know how many past 6 dB increase but it's a
LOT.  You wish you had done comparative RBN before changes.  You have
eliminated serious loss problems.  Emphasis on plural.  You are so happy
with your new antenna you can hardly stand it.  You can't prove anything to
the skeptics, but you just don't care.

b)  This will be a lot more than 6 dB, but not the stark change in a).
You ARE happy with it.

c)  Same as b)

d) Not spectacular, 6 dB-ish.  Will you keep it?  Sure you will.  Happy?
 Yes.  Finding a spare 4,5,6 dB laying around is tough.

e) Particularly if you have similar numbers on other RBN nodes, this is
going to be (32-18) minus (26-23), or 14-3, or 11 dB.  You may have fixed
multiple issues.  If Jerry has a  good 1/4 wave over 60 buried 1/4 wave
radials,  you are probably at the best you can do with an FCP.  It's time
to worry about RX antennas.

f)  This is fuzzy-words for S unit.  See d).  To see whether there is more
to be had you need to do long comparisons with someone local with a good
antenna.  It's always theoretically possible to get to within 3 dB of a
good 1/4 wave over full size, dense and uniform all around radials.

---

One needs to keep some tolerant perspective about anecdotes.  People are
verbal.  Stories travel fast without apparent means of transmission. Data
needs the internet.  Most people have a good built-in innate understanding
of the anecdotes above, EXCEPT for e).  They will look at that and ask
themselves, what does 11 dB sound like, and then try to translate it into
something like a,b,c,d,f.  :>)

I've been trying to help people, not spreadsheets.  So this lack of
specificity, understandably tortuous to some here, bothers me not at all.
 We WILL get our chance to run some good numbers that may satisfy the
spreadsheet hacks (or not).  It's just that in our circumstances it is such
a ROYAL PITA.

73, and a most excellent holiday season to you all.

Guy.