Hi Dave , Bob and Jay
Fist of all thanks Dave and Bob to bring this discussion to the high level
technical discussion this group is used to, and my public sincere apologize
my friend Jay for my emotional behavior that I regrets.
160m is a unique band that has only one noise component on sky wave, and it
is atmospheric noise, HF on the other hands has several other component's of
noise including cosmic rays. Going up in frequency atmospheric noise
decrease and cosmic rays increases.
We are in the low part of the solar cycle, propagation on most HF bands are
very poor, but not dead!. The Signal to noise ration is very important. I
was talking with my old friend PY5EG , Atilano Oms, about propagation , He
mentioned that he can hear 15m weak signals on his 72 FT boom 8 elements 15m
Yagi and can not hear on his 5 element Yagi. The reason is the high
directivity g the large Yagi over the short Yagi. More directivity means you
can hear the signal above the noise on the higher RFD Yagi. Experiments on
VHF , 2m , 6m ant also EME systems, has the same results.
On 160m when you don't have atmospheric noise and no ground wave (manmade
noise), the noise temperature can drop to 70 degree Kelvin, that is lower
than 144 Mhz. In this situation the signal to noise ratio is the Noise
figure of the RX system. However that situation is only present on few days
during the winter nights. Some atmospheric noise is known by QRN at
distance., or normal propagation noise.
Bob is right about quiet locations, noise near -125 db is rare. Manmade
noise on ground wave is becoming a real problem.
The DRF or directivity improves signal to noise ratio at the antenna feed
point, all electronic beyond this point deteriorate signal to noise ratio.
If the NF is the same equivalent temperature of the noise the deterioration
is 2.3 db S/N, on 160m at 70 K the NF of 2 db deteriorates the signal to
noise ratio by 2.3 db. If he noise is above the NF of the system there is no
deterioration because the propagation noise dominates.
When noise is present li my city lot -85dbm average during the day, and my
best ever measured noise -100dBm. RDF plays a lot. 9 db RDF improves the S/N
ratio over 6 db from the vertical TX antenna that has 6 db RDF. Going to the
WF vertical or horizontal with the same 11.5 db RDF, my 10 years measure
shows 10 db improvement. The HWF rejects mand made noise due a -90db gain on
the main direction, the ground waive is not amplified because it sits below
the MDS of the receiver. Again, my measures show 20 or more db improve on
signal to noise ratio over my vertical.
Places with different local noise has different results, if the noise is
s9+10 on -63 dBm, you can hear it on the HWF because it's above the MDS of
the receiver. This not considering common mode leak into the RX system, big
issue for all of us.
A good 4 square TX antenna, 4 vertical in phase has 11db to 12 db RDF, the
front lobe is 90 degree. One FLAG, EWE or K9AY, all loaded loops has a
cardioid patter similar 2 vertical ins phase, good front back and a 120
degree front lobe. Two EWE or Flag or K9AY phased has the same pattern or
RDF the 4 square, depending on the way it is build the RDF is 11 to 12 db, 4
verticals in phase like the TX array. It is simple like that. * verticals
has better RDF than 4 verticals, over 13 db RDF, and 60 degree front lobe.
It is easy to understand why a loaded loop self-phased by the resistor and
the transformer has a cardioid pattern over a large bandwidth , with a
small dimensions loop 1/10 of wave length the loaded loop can maintain the
patter from1 to 10 MHz , a smaller loaded loop 3 to 30 MHz, and a very
larger small loop to 300KHz to 3 MHz .
A delta flag has one horizontal wire and two wires inclined, let's say 45
degree. The current on the horizontal wire generates a current on the ground
180 degree out of phase and there is a cancelation between them , it is
really a transmit]ion line, that is why a K9AY can mover the resistor and
transformer to the center, and switch directions using a relay.
The inclined wire current , let's say with a vector module 1, can be
decomposed by one vertical vector .707 module and another horizontal vector
also .707 module, sounds familiar in vectoral algebra. The horizontal
component cancel against the reflected waive from the ground, the vertical
component adds to the reflected wave from the ground like a real vertical.
The EWE, both horizontal wires are really a transition line phasing the
two verticals.
The Delta Flag or FO0AAA, same thing, can be phased, two phased flag or WF,
is equivalent to 4 verticals. 4 Delta Flags are equivalent to 8 verticals,
you can get 13 db RDF , 60 degree front lobe. Very clean and at low angles.
In general a good phased vertical array outperform and beverage array
because the patter is cleaner and low angle radiation..
In the case of a SAL the vectoral description above apply, the two inclined
wire are really two verticals, the two vertical wire in the center works
like a transmission like the almost cancel it self, it depending on the
adjust of the load, The BALUN with 1 turn primary impedance depend on the
impedance ratio, lets say 9:1, a 100 ohms load represent a 900 ohms
impedance on the secondary. This load thing is complicated but it works
and the cardioid patter is there, and very similar to a Flag.
Same variation in phasing system like DHDL , has some improvident on RDF but
is not like a 4 vertical because the two inclined wire 180 degree out of
phase cancel it self. There is a .5 or 1 db increase on RDF depending on the
quality of the ground, The DHDL works better on good ground like near the
beach. Same reason the K9AY the horizonal wire is a transmission line with
the ground. The SAL vectoral components are very similar to a DHDL. It is .5
db better than the single FLAG. But enough to give you around 2 db increase
on SNR.
My webinar is available on the WWROF archives, both presentation are there
with the slides in pdf with more complete explanation. The presentation is a
result of 12 years if experiments and data collected on thousands of
measures, limited by my owl resources. It is a start point for more
developments, just a ham contribution with our ham spirit.
73's
JC
N4IS
-----Original Message-----
From: Topband <topband-bounces@contesting.com> On Behalf Of
daraymond@iowatelecom.net
Sent: Saturday, December 29, 2018 1:13 AM
To: topband@contesting.com; W7RH <midnight18@cox.net>
Subject: Re: Topband: Topband Digest, Vol 192, Issue 33
I can heartily confirm Bob's experience. I live in Iowa and moved from the
suburbs of Des Moines to a rural setting 22 years ago. I have a well
constructed overhead single phase 13.2 kV distribution feed on the road 1/4
mile from my home. My house is fed underground from the pole to the
transformer and underground from there to the house. When I first moved
here my mid-day noise floor on a 1/4 wave vertical antenna ran around -125
to -130 dbm (300 hz bandwidth). Switching from no antenna to the 1/4 wave
vertical on a sunny mid-day made a obvious but fairly insignificant
difference. I had very little man made noise. I then added a four square
transmit array.
I
subsequently put up several single wire Beverages, two-wire reversible
Beverages, and was the first to build W8JI's passive/tuned vertical array
design (which, oddly enough, had a simple design error which Tom quickly
caught and corrected). While all the RX antennas worked, they rarely out
"heard" the four square TX array and if they did, not by much. Remarkably,
they didn't "out hear" the 1/4 vertical by a whole lot many times either. I
began wondering if all these RX antennas were somehow defective (it's kind
of hard to screw up a Beverage). The answer proved out to be. . .they were
all working fine.
I have mentioned this a couple of times over the years but perhaps it's
worth noting.
The bottom line is. . .if you have a really quiet QTH (getting to a rarity),
having a terrific RDF doesn't buy you much in terms of improving real S/N
performance (with no "N" ?) and true ability to hear. If you are fortunate
enough to be in this situation, you also quickly realize quiet low gain RX
antennas are often noise figure limited (on several occasions people kept
telling me "you just need more gain". .
not necessarily so).
About six or eight years ago I put up an early Hi-Z 8 circle array which has
and continues to perform extremely well. Interestingly enough, many times
it doesn't hear all that much better than the four square TX antenna (but
putting it in diversity is a huge help). That said, with all the
encroaching rural homesteads being built with a mile or two, my noise floor
over the past five years or so has slowly crept up to
about -115 or -120 dbm. Sometimes I'm seeing -115. Lee/K7JTR understands
the
low noise floor issue very well and, at my and others behest, developed the
+6 amps
for the Hi-Z antennas with improved NF. He and I have had discussions about
improving this further but, frankly, I'm not certain there is much of a
market for people with true -130 noise floors. . .hi. With my ever
increasing noise floor, the performance difference between the Hi-Z 8 and
the TX antenna has become more apparent.
Sadly, my quiet QTH is not as quiet as it once was making RDF now matter
more.
See you all in the Stew. 73 and Happy New Year to all. . .Dave, W0FLS
-----Original Message-----
From: W7RH
Sent: Friday, December 28, 2018 11:04 PM
To: topband@contesting.com
Subject: Re: Topband: Topband Digest, Vol 192, Issue 33
All,
Two cents worth of comments on thread. The SAL, K9AY and Waller Flags all
work well and have their limitations. They do help the city folk improve the
ability to receive. The WF works great if you can get it up in the air and
rotate it. That is if you can keep it there in one piece though snow , ice
and wind. It also encompasses additional costs for tower support and
rotator.
The larger passive and active arrays specifically 8 circle provided you have
space are better yet with great RDF, realistic gain and noise figures.
There is a cross over point where there is no longer any improvement IMHO.
I'll point out an example. In the morning hours before sun rise my noise
floor drops to near zero on my RX/TX array. I'm extremely fortunate for I
have the space and no neighbors, no commercial power and thus only natural
noise. A reasonable guess would be a noise floor greater than -120 to
-125dB. Almost to the point of MDS where there is no indicated or measured
difference between antenna and no antenna.
Working signals via polar path, NW, West and SE are _on average very very
weak._
My experience tells me that active loops would be inferior to the existing
directional RX/TX antenna at this point because of their signal capture
levels and increased noise created by preamplifier. In this case only long
properly terminated and maybe phased beverages would be better.
I can feel the heat coming on this one. I'm not here to sell antennas as I
build my own.
73 and Happy New Year!
Bob, W7RH
--
W7RH DM35OS
It has become appallingly obvious that our technology has exceeded our
humanity.
Albert Einstein
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