Re: Topband: Waller Flag Question

[Mike Waters]

On a totally unrelated note, I cascaded two preamps to get 40 dB of gain
about 30 years ago. They were identical circuits, both using MGF-1202 GaAs
FETs.

The input was a Zener diode noise generator. The second preamp fed a 3dB
splitter which fed two inputs of a low-loss passive nulling circuit I
designed. The output of that fed a 2m to 10m RX converter, which fed 10
meter receivers.

That nulling circuit nulled all of that noise, much to our delight. But
it's not practical on 160m. :-)

And the preamps' piston trimmers could be adjusted either for maximum gain
or for lowest NF, but NOT at the same setting.

73, Mike
www.w0btu.com
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Re: Topband: The first indicators that Solar Cycle 25 may be similar in amplitude to Cycle 24

[donovanf]

Oops, I forgot to sign my prior email... 


73 
Frank 
W3LPL 

- Original Message -

From: donov...@starpower.net 
To: "PVRC" , cq-cont...@contesting.com, 
topband@contesting.com 
Sent: Tuesday, September 8, 2015 6:41:14 PM 
Subject: The first indicators that Solar Cycle 25 may be similar in amplitude 
to Cycle 24 



Until mid-2014 Solar Cycle 24 was remarkably quiet. Despite the 
steadily declining solar flux since mid-2014, the Sun’s large-scale 
magnetic field suddenly strengthened late in 2014 reaching its 
highest value in more than twenty years . Using these and related 
observations, two Naval Research Laboratory researchers, Wang 
and Sheehy, predict in their August 2015 article in The Astrophysical 
Journal that Solar Cycle 25 may reach an amplitude similar to Solar 
Cycle 24. 


Until the unexpectedly sudden and strong increase in the Sun’s large- 
scale magnetic field, some solar scientists feared that S olar Cycle 25 
might achieve a much lower amplitude than Cycle 24. Those fears 
might now be put to rest. 

http://aasnova.org/2015/09/02/witnessing-solar-rejuvenation 
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Topband: Waller Flag

[Lee K7TJR]

I must be missing something.

The noise in a 50 ohm resistor is -174 dbm per root Hz at ambient temp.

Lets take 100Hz bandwidth for the receiver and the noise becomes -154 dbm or
.0045 uVolts

Lets add a PERFECT amplifier of 40 db. The noise output of the 40 db amp is
then -114 dbm or 0.446 uVolts

S-2 on a receiver with perfect S meter is .4 uVolts so the RX should set at
S-2 normally.

As I understand it the Waller antenna produces about -45 db of gain over
some reference.  (45 db Is 177 time voltage)

So in order to simply match the noise level of .446 uVolts with a signal you
need a signal impinging on this antenna that would produce 79 uVolts in an
antenna similar to the reference.

To me a signal of 79 uVolts is something over S-9 on a receiver. Would a
simple dipole or inverted Vee antenna with essentially no gain produce a
whopping signal from the same source. Of course it would pick up noise as
well but I would think it would not be of an equal S-9 level.

 

  Where did I go wrong in these figures. I must be astray somewhere.

 

Lee  K7TJR  OR

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Re: Topband: The first indicators that Solar Cycle 25 may be similar in amplitude to Cycle 24

[Mike Waters]

That's not so good news for 160, eh?

73, Mike
www.w0btu.com

On Tue, Sep 8, 2015 at 1:41 PM,  wrote:

> ... some solar scientists feared that Solar Cycle 25 might achieve a much
> lower amplitude than Cycle 24. Those fears might now be put to rest.
>
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Re: Topband: Waller Flag

[JC]

Lee

Yes, this is confusing as it can get. Any passive component adds noise, any
active components adds noise. Power noise, and you only can add power noise
converting it in equivalent temperature in Kelvin degree.

The antenna itself is another confusing thing, any antenna has directivity
gain and power gain, when the efficiency in near 100% the power gain is the
same as directivity gain and most just say antenna gain, this assumes power
factor 1, no loss. 

EZENEC gain calculation for loops near ground is not perfect as well, If you
build a loop and measure the mv/m you find a surprised difference between
EZNEC power gain. Directivity gain is really RDF by definition so the HWF
and VWF has 11.5 directivity gain and let's say a very low power gain, the
system have losses.

The receiving systems starts at the preamp. Even if it's near the antenna,
far from the radio, or near the radio. The calculation is the same. 

The S meter in most analog radio measures the AGC, in SDR radios it can be
calibrates in dBm at the input of the preamp. That can be consider operator
preferences.

Power noise, power gain, voltage gain can be very confusing because the real
input or output impedance .

The discussion is really about the signal to noise ratio near the noise
floor of the receiver system. If you use you S meter at the input of the
preamp or after the preamp, it does not change the signal to noise ratio.

Small loops also have thermal noise itself and can be a limit factor as
well. 

>>
So in order to simply match the noise level of .446 uVolts with a signal you
need a signal impinging on this antenna that would produce 79 uVolts in an
antenna similar to the reference.
<<

I really don't understand you point can you elaborate it?


Regards
JC
N4IS

-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Lee K7TJR
Sent: Tuesday, September 08, 2015 4:01 PM
To: topband@contesting.com
Subject: Topband: Waller Flag

I must be missing something.

The noise in a 50 ohm resistor is -174 dbm per root Hz at ambient temp.

Lets take 100Hz bandwidth for the receiver and the noise becomes -154 dbm or
.0045 uVolts

Lets add a PERFECT amplifier of 40 db. The noise output of the 40 db amp is
then -114 dbm or 0.446 uVolts

S-2 on a receiver with perfect S meter is .4 uVolts so the RX should set at
S-2 normally.

As I understand it the Waller antenna produces about -45 db of gain over
some reference.  (45 db Is 177 time voltage)


To me a signal of 79 uVolts is something over S-9 on a receiver. Would a
simple dipole or inverted Vee antenna with essentially no gain produce a
whopping signal from the same source. Of course it would pick up noise as
well but I would think it would not be of an equal S-9 level.

 

  Where did I go wrong in these figures. I must be astray somewhere.

 

Lee  K7TJR  OR

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Re: Topband: Waller Flag

[Richard (Rick) Karlquist]

On 9/8/2015 1:01 PM, Lee  K7TJR wrote:


To me a signal of 79 uVolts is something over S-9 on a receiver. Would a
simple dipole or inverted Vee antenna with essentially no gain produce a
whopping signal from the same source. Of course it would pick up noise as
well but I would think it would not be of an equal S-9 level.


FWIW, my 90 foot 160 meter vertical routinely produces 79 uVolts from
DX signals.  Even FT5ZM on Amsterdam Island was in this range.
Stateside big guns at 1000+ miles produce much more than this,
20 to 40 dB more.

Rick N6RK
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Re: Topband: The first indicators that Solar Cycle 25 may be similar in amplitude to Cycle 24

[Guy Olinger K2AV]

Not really a problem for 160.

Solar minimum is a solar minimum is a solar minimum. In the last solar
minimum a certain well known multi-multi in one of the major CW DX
tests did a single weekend five band DXCC 160 through 15 meters. I think
that's the only time that's ever been done. Great ops great antennas great
equipment all in place before and since. Seemingly, super great conditions,
maybe once in a lifetime, also have to be in place for such an
accomplishment.

I'm getting ready for what might be a remarkable string of 160 seasons.

73, Guy K2AV

On Tuesday, September 8, 2015, Mike Waters  wrote:

> That's not so good news for 160, eh?
>
> 73, Mike
> www.w0btu.com
>
> On Tue, Sep 8, 2015 at 1:41 PM, >
> wrote:
>
> > ... some solar scientists feared that Solar Cycle 25 might achieve a much
> > lower amplitude than Cycle 24. Those fears might now be put to rest.
> >
> _
> Topband Reflector Archives - http://www.contesting.com/_topband
>


-- 
Sent via Gmail Mobile on my iPhone
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Re: Topband: HMC580 instead of W7IUV preamp

[Mike Waters]

Given the recent discussion about the need for low-noise preamps for the
Waller Flag, it would be interesting to learn what the NF on 160 for this
device might be.

It's rated for "DC" up into the GHz range. However, as N4IS pointed out, a
good NF at VHF does not mean a good or better NF below 2 MHz.

73, Mike
www.w0btu.com

On Fri, Aug 28, 2015 at 5:26 PM, Richard (Rick) Karlquist <
rich...@karlquist.com> wrote:

> It might be a lot easier to simply buy this amplifier IC:
>
> http://www.hittite.com/products/view.html/view/HMC580ST89
>
> The specs are close to the W7IUV preamp.
> I mounted one of these ICs on a breadboard and tried it out with a short
> vertical whip and it
> seemed to work fine.
>
> Rick N6RK
>
>
>
> On 8/28/2015 2:53 PM, Martin Kratoska wrote:
>
>> The latest version 6
>>
>> http://www.okdxf.eu/files/preamp_r60.pdf
>>
>> 73,
>> Martin, OK1RR
>>
>
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Re: Topband: Waller Flag Question

[Hugh Valentine]

Pardon me for chiming in on this Waller flag discussion as I am probably the 
least qualified person on Topband to discuss technical issues.

But, I do a lot of Trial and Error-ing and use some of the wisdom shared here.  
Plus I am a true Ham O Holic and always want to improve my ability to work DX 
on Low Bands.  And need to keep improving as I only use a highly compromised TX 
antennaa lowly Bird Feeder.

But, I am blessed to live 70’ from a Salt Marsh, on an Island with all 
Utilities/Cable underground and “almost” No Noise. Even though I have probably 
the Lowest 160 Antenna (35’Vertical) I do manage to hear and work long haul Top 
Band DX.

The last 2 years or so I converted from some EWEs(Stealth) to a K9AY Loop 
Array.  This helped boost signals from the quiet.  I next added Two K9YC 
chokes...one 15-20’ from the K9AY feed point, and one in the shack, just before 
the K9AY control box.  Thanks K9YC..Quieter.
So the Top Band Reflector helped me.  During the quieter winter months, most 
mornings on top Band, I can use both the K9AY Preamp and the K3 preamps 
together and have S0 or S1 flashing noise on the K3.  
In monitoring the Low Band Chat, I can most times hear what the Waller Flag 
Guys NX4D and N4IS are reporting,(depending on prop).  I occasionally hear 
things no one can hear...I think just based upon the fact that I have little or 
no noiseIf I get a little bit of noise from a local fluorescent or 
neighbor’s TVjust a little will wipe out a super weak signal and I lose my 
edge/advantage.  I think a lot of weak signals are there for most, just in the 
noise.

I believe those K9YC chokes helped me a lot.

Now, I hear you guys talk about “Detuning” nearby antennas to further reduce 
noise. My K9AY Loop is only 20’ from my “Birdfeeder” TX antenna. (I have a 
Multi-Core K9YC Choke on the Feed Point)
I have a Steppir Vertical which is 1’ from the horizontal portion of the “Bird 
Feeder”-(And 15’ from the K9AY).  And a final OCF Dipole wire is about 15’ from 
the TX Antenna(BF).  Thinks are close.

Question:  Should I look into “Detuning” These other antennae? to further 
reduce noise...

What DX I work is because I have less noise than most and I can hear...But I 
sure need some more advantage to help make up for the old bird Feeder.  I don’t 
work this stuff using power or a big TX antenna.

What the experts are talking about here is reducing Noise, which interferes 
with our ability to hear super weak signals, then Super Amplifiying the weak 
signal to stand out over the noise.  That is my take.

How do I know if “detuning” my TX antennas will help?  and How do I do that?
I can’t put up a Tower or Waller.  I am just an uneducated Redneck Swamp Boy 
tryin’ to make a Biscuit and survive.
And comments appreciated.

I am reading and enjoying these discussions and appreciate the expertise of the 
participants.  Thanks for your help.

73
Val
N4RJ

Want to place your ad here?
Advertise on United Online
http://thirdpartyoffers.juno.com/TGL3141/55ef7ddb4a0167dda7a25st04vuc
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Re: Topband: Waller Flag

[Lee K7TJR]

After putting my conclusions here and a 2 1/2 hour power outage I had an aha
moment and found I did not account for  40 db properly.
  The dipole without a preamp in the same location is just a few db higher
than the Waller with preamp  and would not produce the signals I was
thinking of.
Lee   K7TJR






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Re: Topband: [WARNING: ATTACHMENT(S) MAY CONTAIN MALWARE]RE: Waller Flag Question

[JC]

I meant OFF and not ON for the internal preamp. I don't use internal preamp
ON.


The issue is most internal preamps are not designed for 160m, they need to
cover up to 50 MHz  Even the ICOM Norton preamp does not have the muscle to
handle the signals level on 160m. If you turn  <<  OFF >>  you internal
preamp and use a better preamp outside the radio with a good BPF or
pre-selector you will always  have the flexibility to adjust the system NF
reducing RF gain. But there is no way to improve NF, it is all about less
degradation of the signal to noise ratio.

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Re: Topband: Waller Flag Question

[Tom W8JI]

Tom,  I'm afraid I disagree but agree with some of  that, I am using a 
43dB
gain preamp since 2010 with not a single failure yet, but I understand 
your
point. It is so delicate to implement that most of fellow that try it 
fail.

Even aluminum enclosure does not shield it enough, 40 dB gain is 10.000
voltage gain, it needs a dual shield with steel to cut magnetic field, the
feed lines must be decoupled over 80 dB, relays must be 100dB or more in
isolation, and much more details that I won't cover.

It is not a weekend project.



JC,

The problem is gain and noise figure, not shielding.

Let's assume a receiver with 250 Hz bandwidth has a MDS (3dB S+S/N) of -135 
dBm. This is a 15 dB receiver noise figure.


A 0.5 dB noise figure front end amplifier with NO other losses would 
produce -149.5 dB MDS. That is the absolute maximum MDS sensitivity 
obtainable with 250 Hz BW and 0.5dB total input noise figure.


If we include the receiver's noise figure, 14.5 dBm gain would result is a 
system composite noise figure of 3.44 dB. Increasing amplifier gain (with no 
change in amplifier 0.5 dB noise figure) results in the following system 
composite noise figures:


14.5dB = 3.44 dB
20 dB =  1.55 dB
25 dB =  0.86 dB
30 dB =  0.62 dB
35 dB = 0.54 dB
40 dB = 0.51 dB

At someplace around 20-25 dB, you get into system limits. The improvement 
from 30 dB to 40 dB is only 0.11 dB. No one will notice that.


This of course varies with the receiver, but few receivers are worse than 
this example.


Let's say we have an input stage NF of .5 dB with 15 dB gain. In order to 
have a cascade NF of .7dB the second stage has to have about a 2 dB NF.


All of this is peanuts.   A .6dB noise figure is a 3 dB MDS of -149.4 
dBm, while a 2 dB NF is a MDS of -148 dBm with 250 Hz BW.


There is a point where inevitable system flaws make using an antenna with 
such negative gain to require less than 1 dB NF impossible for "copy this 
plan".  This is why Beazley's out-of-phase small horizontal elements were 
mostly met with didn't work. The problem with models is we can build perfect 
systems that we cannot repeat in the real world.


Again my example of the small commercial loop I have. It limits by loop 
internal noise by many  dB at my location, and common mode on the cable is 
very evident. If I moved the same antenna to a location with 20 dB more 
external ambient noise floor, it would limit on external noise.


It seems unlikely most compact antennas are being used in locations so quiet 
they need 30 dB gain, or .6 dB NF.   If they had room, they would not have 
as much ambient site noise.


I'm not being disagreeable, just describing the practical limits.

73 Tom 


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Topband: [WARNING: ATTACHMENT(S) MAY CONTAIN MALWARE]RE: Waller Flag Question

[JC]

>>
A 0.5 dB noise figure front end amplifier with NO other losses would produce
-149.5 dB MDS. That is the absolute maximum MDS sensitivity obtainable with
250 Hz BW and 0.5dB total input noise figure.
<<

Correct agree
>>

If we include the receiver's noise figure, 14.5 dBm gain would result is a
system composite noise figure of 3.44 dB. 
At someplace around 20-25 dB, you get into system limits. The improvement
from 30 dB to 40 dB is only 0.11 dB. No one will notice that.
>>

Agree when the signal is above noise floor

The issue is most internal preamps are not designed for 160m, they need to
cover up to 50 MHz  Even the ICOM Norton preamp does not have the muscle to
handle the signals level on 160m. If you turn on you internal preamp and use
a better preamp outside the radio with a good BPF or pre-selector you will
always  have the flexibility to adjust the system NF reducing RF gain. But
there is no way to improve NF it is all about less degradation of the signal
to noise ratio.

The low NF is required only when the propagation noise is very low, the
concept of degradation is based on human skills and vary from operator to
operator, Most of us can copy CW signal 3 db above noise, 2 db above noise
is hard to copy, and 0 db SNR is very hard  but some of us can compensate
that in their brain.

What I don't agree is that :

When the signal is at noise level. 3 db improvement on signal to noise ratio
can make a QSO possible, you can hear the DX early and for a long time
before it fade. 3 db degradation means 50% power noise and 50% signal power
noise. Near the MDS 3 db signal to noise is close to 3db NF improvement.

At this point the difference is copy or no copy. QSO or no QSO. Log the DX
or wait the next DX expedition.



<<
There is a point where inevitable system flaws make using an antenna with
such negative gain to require less than 1 dB NF impossible for "copy this
plan".  This is why Beazley's out-of-phase small horizontal elements were
mostly met with didn't work. The problem with models is we can build perfect
systems that we cannot repeat in the real world.
>>

Agree , the practical noise figure for the system is around 2 dB NF, The way
to drop the noise floor few db more is reducing the BW to 100 Hz or 50 Hz.
An EME experienced CW operator knows that some signals you can copy using 50
Hz and no copy with 100 Hz. It is that simple in real weak signal DX.

The MDS can be low as -157dbm for 50 Hz BW, and this is almost -s9,  if
using 6db for each S unit. There is a lot of dynamic range bellow s0.

3db makes a lot of difference, I fight for every .1 dBm I can get.

<<

Again my example of the small commercial loop I have. 

>>  

The HWF is not so small, for the WF300 (300 sq Ft.) I use 44 ft boom and
loops 24ft.x12ft.

However for a noise location there is  one ideal size, the trick is to drop
local manmade noise bellow or near  the MDS.  During the day the HWF looks
like a dummy load noiseless antenna. My system's uses different gain for
each band and tuned for a radios with 20 NF (no internal preamp on).

For noise locations the WF200 with 24 ft boom is a good choice.

Like I said , it's not a weekend project but can be done and it performs
very well. Polarization filter is a powerful tool for urban stations that
cannot be disregarded.

There is no commercial loop compatible or comparable to the HWF antenna, it
is a different ball game. 

The results worth the time and money to implement it.

It all a good debate and we agree in most of it. Or at least we agree we
disagree.

Regards
JC
N4IS
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Re: Topband: Waller Flag Question

[K1FZ-Bruce]

Above and beyond all the dialogue, JC is making these antennas work. 
Time after time he is working stations that only a few with large 
antenna systems copy. 
 

73
Bruce-K1FZ
 
 
 
 
 

It seems unlikely most compact antennas are being used in locations so quiet
they need 30 dB gain, or .6 dB NF. If they had room, they would not have
as much ambient site noise. 

I'm not being disagreeable, just describing the practical limits. 


73 Tom

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Re: Topband: Waller Flag Question

[Mike Waters]

There seems to be something that I'm missing in this preamp NF discussion.

When I studied preamps and NF ~30 years ago, I thought the NF of the system
of the first active device was the all-important thing. Whatever losses
were between the antenna feedpoint and the preamp input (coax, connectors,
relays) added to that.

Once that preamp brought up the S+N above a certain point, the NF of the
amplifiers  downstream were not near as important.

Very low NFs, less than 0.5 dB, are easily obtainable with everything at
room temperature. (I used GaAs FETs at 144 MHz, but there are even better
devices today with lower NFs.)

A couple of papers I just downloaded and skimmed over seemed to reinforce
that.

Look at the last three slides with screen shots of AppCAD in NoiseCalc mode
at
http://ve2zaz.net/Presentations/Downloads/VE2ZAZ_EME_Presentation.pdf
and the paper at
http://dpmc.unige.ch/dubus/8804-2.pdf
There's much more to read on Google (I searched for *noise figure eme)* and
in my library, but I still have the flu and I'm done for now.

73, Mike
www.w0btu.com
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Re: Topband: Waller Flag Question

[Mike Waters]

There is no question in my mind that he is, Bruce.

I would just like to understand what Tom is saying. I almost think he had
noise figure confused with noise temperature at one point.

Correction to my previous e-mail, first sentence in second paragraph.
should have said "When I studied preamps and NF ~30 years ago, I thought
the NF of the first active device (preamp) was the all-important thing".

73, Mike
www.w0btu.com

On Tue, Sep 8, 2015 at 12:47 PM, K1FZ-Bruce  wrote:

>
> Above and beyond all the dialogue, JC is making these antennas work. Time
> after time he is working stations that only a few with large antenna
> systems copy.
>
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Re: Topband: HMC580 instead of W7IUV preamp

[Richard (Rick) Karlquist]

On 9/8/2015 7:02 PM, Mike Waters wrote:

Given the recent discussion about the need for low-noise preamps for the
Waller Flag, it would be interesting to learn what the NF on 160 for
this device might be.

It's rated for "DC" up into the GHz range. However, as N4IS pointed out,
a good NF at VHF does not mean a good or better NF below 2 MHz.

73, Mike
www.w0btu.com 



I've characterized this device and can tell you that the 1/f
corner is well below 2 MHz, because it is based on HBT
technology.  The devices that are good at VHF and noisy
at 2 MHz use MOSFET, GaAsFET, or ephemt technology.
JFET devices are also low noise at 2 MHz if they have a sufficiently
low channel resistance.

Rick N6RK
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