Re: Topband: ADC Overload

[James Wolf]

Jim,

I sense a flaw in the CLT argument, which is likely a lack of understanding on 
my part.  What you are describing sounds more like AGC action.  In-other-words, 
moving the minimum detector level up the bell curve such that we have now lost 
any capability of listening down into a hole between strong stations and 
copying the weak station (which is really what we are talking about).  That 
scenario now sounds like a corner case. 
Other wise, what happened to the two +3V stations that add up to +6V.   Do they 
still show up on the bell curve, and if they no longer add up to +6V, why not?

Thanks for the insight,

Jim - KR9U

-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim Garland
Sent: Monday, October 12, 2015 2:35 PM
To: st...@flexradio.com; topband@contesting.com
Cc: 'K1JD John'; 'Phillip Townsend Lontz'
Subject: Re: Topband: ADC Overload

Interesting comments, Steve, and to me quite on the mark. (In an ealier life, I 
was a physics prof, though I've forgotten most of what I once knew).

Re the comment by another list member that "there are various distractions such 
as the Central Limit Theorem...that don't add much to the discussion":  On the 
contrary, I believe the CLT is actually crucial to this discussion. Here's my 
attempt at an intuitive explanation of the CLT using a _very_ simplified 
example. I hope this contributes to this interesting discussion.

Suppose we have an SDR radio that hears two identical signals, and that the ADC 
in the receiver overloads when the instantaneous antenna voltage at the 
receiver input is greater than +/- 5V. Now let's assume that each of our 
identical signals has a maximum instantaneous RF voltage of +/- 3V, so that the 
receiver will overload when both signals add up to give either +6V or -6V. The 
question that the Central Limit Theorem addresses is how frequently this 
overload condition will occur. Here's how it works.

We'll keep things simple by assuming each of our two signals can take on only 
seven values of voltage: +3V, +2V,+1V, 0V, -1V, -2V, and -3V. (In reality of 
course, for a CW signal, the signals are sine waves varying continuously from 
+3V to -3V.) Every time the SDR samples these signals, it sees the 
instantaneous sum of their voltages. Since each signal has seven possible 
values, the sum of the voltages can have 7x7=49 possible values, which range 
from +6V down to -6V. 

If you make a list of all possible combinations of these two signals, you'll 
find that of the 49 possibilities, 0V comes up seven times, 1V comes up six 
times, 2V comes up 5 times and so forth, until you get to 6V (when the maximum 
value of signal adds up exactly). The reason 0V comes up seven times is because 
there are seven ways to get 0 by adding the voltages from the two signals, 
i.e., 0V plus 0V, +1V plus -1V, -1V plus +1V, +2V plus -2V, -2V plus +2V, +3V 
plus -3V, and -3V plus +3V. By contrast, there is only one way to get +6V, 
which is +3V plus +3V, and similarly for --6V.

Now if the ADC in the receiver overloads at any voltage greater than  +/- 5V, 
as we have assumed, then it will overload only two times in every 49 samples, 
once when the voltage is +6V and once when the voltage is -6V. If you draw a 
graph of all the possible combinations of voltages, plotting the numbers of 
times each combination of voltages comes up, you'll see that the graph 
resembles a bell-shaped curve, (called a "normal" distribution) peaked at zero. 
The maximum values of +6V and -6V are at the tail ends of the distribution.

So in this simplified example, our SDR radio will overload 2 out of every 49 
samples, or about four percent of the time. That's not terrible, but not 
wonderful either. It means that we'd hear a pop in our receiver about four 
percent of the time. But suppose we let our two signals take on a continuous 
range of values between +3V and -3V. instead of only seven possible values. 
Unforunately, things don't get much better. The data points on our bell-shaped 
curve would smooth out, but we'd still overload roughly four percent of the 
time. The general shape of the curve doesn't change.

But...here's the interesting thing. Suppose instead of only two signals, we 
have thousands of signals appearing at our antenna terminals, and we'll 
continue to assume each of our thousands of signals varies from +/- 3V. Now 
when we add up the voltages of each of these signals, we find something 
remarkable. The sums of the voltages of all these signals is still a 
bell-shaped curve peaked at zero volts and extending from +6V down to -6V, but 
with one significant change. The bell-shaped curve narrows in, becoming very 
sharply peaked at 0V. The extremes of the curve, which would overload our 
receiver, almost never happens. This peaking of the curve is what the Central 
Limit Theorem tells us, and basically it is the reason SDR radios are in most 
cases nearly immune from overload. The more signals we're hearing with

Re: Topband: Commond mode choke for Beverage

[Jim Brown]

On Mon,10/12/2015 1:27 PM, JC wrote:

It works like a voltage divider where the impedance to ground should be lower 
as possible to give you more attenuation  like 1k/500ohms versus 1K/5 ohms 
divider.


Yes.

But to expand on this -- often the interference is coupled into a gain 
stage or RX by a Pin One Problem. ALWAYS make the first connection of 
any cable shield to the shielding enclosure of EVERY active device. 
Follow this rule regardless of the function of the cable -- input, 
output, control line, RF or audio.


It's also good practice to bring RX antennas into the shack via the same 
grounding panel used for TX antennas. And that panel must be tied to 
local ground rods, those rods bonded to all other grounds, to the shack 
desk, etc.


73, Jim K9YC
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Re: Topband: High Pass Filter

[Jim Brown]

Switchcraft and Neutrik both make excellent RCA male cable-mount 
connectors. They are easy to terminate, and the shell will accept cable 
with an o.d. of about 0.25-in. They can be used with RG58 and RG59 
cables having a copper braid shield. I buy stuff like this from Full 
Compass, near Madison, WI.


73, Jim K9YC

On Mon,10/12/2015 11:18 AM, m.r.c. wrote:
I have generally found RCA connectors to be unsatisfactory in the long 
term for a variety of reasons generally revolving around the "Astro" 
plate hard nickel surfaces.  A large number of 160 receive antenna 
systems are built with type F connectors with generally good results - 
as well as it being a threaded connector instead of a slip on (read: 
slip off in the middle of the contest)


_
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Re: Topband: ADC Overload

[Mike Waters]

Hi Barry,

Thanks for your input. Yes, I believe we included direct sampling digital
receivers (SDR) versus superhet receivers.

The post I made here today is not complete; rather that re-post everything,
I included a link to the early August discussion, which explained in detail
what I meant. This is what I asked:

"I'd like to know whether it's ever been established that some very talented
hams can out-hear the best SDRs and/or DSP available. Can a skilled
ear-brain combo (such as some highly-skilled and talented 160 meter
contesters) beat state-of-the art digital signal processing when it comes
to copying the very weakest of signals buried in the noise?

"I always thought Linrad was the best DSP software, though I never got it
working right here (older sound card issues in Xubuntu).

"I asked the following question at
http://www.eham.net/ehamforum/smf/index.php?topic=104388.msg861047#msg861047
: "Are there any people who can hear weak signals with a good analog
receiver, who --if they could instantly switch their antenna and headphones
from the analog RX over to the best SDR made today-- simply couldn't hear
any better with today's best SDRs and/or DSP software?"

"There's been a few opinions, but how about multiple valid tests?"

There were a number of replies, both on the Linrad and the Topband
reflectors. Sounds like you don't agree with most. What direct-sampling
receiver did you mean?

73, Mike
www.w0btu.com

On Mon, Oct 12, 2015 at 6:53 PM, Barry N1EU  wrote:

> On Mon, Oct 12, 2015 at 10:28 PM, Mike Waters  wrote:
>
> > But as a recent thread here* established, there is *NO* SDR that can
> > perform as
> > well as a good ear-brain combo for copying the very weakest of signals
> > buried in the noise. Maybe someday, but the future has not arrived yet.
> :-)
> >
> >
> The statement is a bit ambiguous.  I don't know what you mean by "SDR" in
> the statement above.  If you're talking about dsp noise reduction versus no
> noise reduction, I agree.  But if you're talking about direct sampling
> digital receivers (SDR) versus superhet receivers, I categorically
> disagree.
>
> 73, Barry N1EU
>
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Re: Topband: FW: Commond mode choke for Beverage

[Tom W8JI]

I tried 7 & 8 turns, but it resolved too high in freq.



Use 9 TURNS on a core-stack of five (5) of  P/N 2631803802 cores. That’s 
the Mix #31 core.



The attenuation of any choke significantly depends on the common mode 
impedance, and impedances from shield to ground. Many times just a few ohms 
is enough, some cases even 10,000 ohms will not help.


It is a system that varies from place to place. For example, if you have a 
small floating loop the common mode impedance of that loop is already so 
high a choke would have no effect at all. If you have a cable between two 
fairly well grounded points, if it even needs a choke, the choke requirement 
would be low.


It is almost like a pi network filter. There is a shunt impedance at one end 
of the choke, the choke impedance, a series line common mode impedance, and 
another shunt impedance.


A dipole is another example. If the feed cable to a dipole is 1/8th to 3/8th 
wave long with a cable suspended away from things, and it is grounded at the 
earth, it is just as effective as using a balun. If you added a common mode 
choke near ground, it would make common mode significantly worse.


Before going wild with impedance goals, it is a good idea to look at the 
particular system.


My Beverage RX antennas at the antennas are isolated from the cable shield 
because I have just a few short ground rods. I don't want the shield being 
be a ground for those poor ground rods, because the shield would couple in 
unwanted signal. My RX verticals out in a field each have 8 long radials and 
buried feed cables, and the hub is well grounded. They have no common mode 
isolation at all, and do not need any.  Any contribution of signal by the 
coax would be no different than just adding another radial.



73 Tom

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Re: Topband: ADC Overload

[Barry N1EU]

On Mon, Oct 12, 2015 at 10:28 PM, Mike Waters  wrote:

> But as a recent thread here* established, there is *NO* SDR that can
> perform as
> well as a good ear-brain combo for copying the very weakest of signals
> buried in the noise. Maybe someday, but the future has not arrived yet. :-)
>
>
The statement is a bit ambiguous.  I don't know what you mean by "SDR" in
the statement above.  If you're talking about dsp noise reduction versus no
noise reduction, I agree.  But if you're talking about direct sampling
digital receivers (SDR) versus superhet receivers, I categorically disagree.

73, Barry N1EU
_
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Re: Topband: ADC Overload

[Mike Waters]

An SDR is better for several things, yes. One advantage is that
near-perfect extremely narrow filters can (and do) exist in software. But
as a recent thread here* established, there is *NO* SDR that can perform as
well as a good ear-brain combo for copying the very weakest of signals
buried in the noise. Maybe someday, but the future has not arrived yet. :-)

*I posted a question here and the Linrad reflector on August 4, and
received many informative replies. Many can be viewed at
lists.contesting.com/_topband/2015-08/msg8.html

73, Mike
www.w0btu.com

On Mon, Oct 12, 2015 at 4:15 PM, JC  wrote:

>
> It's well know the ability to copy weak signal near strong carriers.
> ...Yes the SDR is a better receiver but...
>
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Re: Topband: ADC Overload

[JC]

Hi Guys

It's well know the ability to copy weak signal near strong carriers. I run a
QS1R using HDSDR all the time shearing the same RX antenna with my IC7800.
In the last 10 years only once I worked a new country on 160 listening on
the SDR that I was not able to copy using the IC7800. David summer was
operating "simplex" from 4U1ITU once on 160m. and the pile up with US and
European station was very  "peculiar" on 1820.00. Everybody on the same
frequency. Yes the SDR is a better receiver but for practical reasons not
the more efficient radio to operate. 

Just have a driver problem with windows and you will find yourself hours
trying to find why the IP address does not match the SDR anymore or other
silly software things that takes hours to fix. 

I was not surprised to know from a good friend that some big contest
stations run DOS PC's!!

Here where the ADC overload gets complicated, when the ADC overload the
noise floor goes up for several seconds(or minutes), plus the pops. On low
bands all receiver antennas has different gain as you move up in frequency.
Like a Flag or beverage gain on 160m is low but the same antenna has  20 db
more gain on 10 MHz. Using the most common high pass filter to reduce AM BC
band bellow 1.8MHz infront a 20 db gain preamp, does not attenuate signals
from broadcast bands near 5 MHz, 7 MHz, 9 Mhz, 11 MHz, etc.  Endeed the
signal can be 40 dBm stronger than it should be in a vertical without
preamp. If the preamp is not tuned or have a band  pass filter after it ,the
problem of overload become a huge one, and you don't even know where the
overload  is coming from. AM BC reduces power during the night but
propagation brings strong signal from HF broadcast at night, specially near
SR and SS. It is not all the same during the day time or during the night.

If you check the top contest results you can find a good reason why the top
stations are using only few Radios models.

Regards
JC
N4IS 





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Re: Topband: Commond mode choke for Beverage

[JC]

Hi Felipe

 

It works like a voltage divider where the impedance to ground should be lower 
as possible to give you more attenuation  like 1k/500ohms versus 1K/5 ohms 
divider. You should use the choke near a good ground before entering the 
station. If you switch box have a good ground it’s a good place to install  it.

More turns better, but it is limited by the diameter of the coaxial cable, like 
RG58/RG142 allows 12 to14 turns. RG213  only 8 turns.

 

Jim K9YC and a fantastic documentation about chokes. Please read this document 

 

http://audiosystemsgroup.com/RFI-Ham.pdf

 

You will be a specialist after reading this guide.

 

Regards

JC

N4IS

 

From: Filipe Lopes [mailto:ct1...@gmail.com] 
Sent: Monday, October 12, 2015 9:52 AM
To: JC 
Cc: topBand 
Subject: Re: Topband: Commond mode choke for Beverage

 

Hello JC, 

 

Thanks for your answer.

 

I just ordered a few 2631803802 and 5943003801 from mouser.

 

With these ferrites I ask the same question, should I put the choke close to 
the 9:1 Balun or near the switching box and how many turns? some bevs have the 
feed point at +- 60m away from the switching box.

 




73's Filipe Lopes 

CT1ILT - CR6K

F4VPX - TM3M 

 

2015-10-12 15:40 GMT+02:00 JC mailto:n...@comcast.net> >:

Hi Filipe

Zero , you should use material #31  or #77 , The core you have is not good
for low bands.

JC
N4IS

-Original Message-
From: Topband [mailto:topband-boun...@contesting.com 
 ] On Behalf Of Filipe
Lopes
Sent: Monday, October 12, 2015 8:46 AM
To: topBand mailto:topband@contesting.com> >
Subject: Topband: Commond mode choke for Beverage

Hi guys,

I am about to add a common mode choke to isolate the antenna from its
feedline to each of my beverages and I only have FT240-61 ferrites. My
question is how many turns should I do on the ferrite using RG58 (all my
bevs are fed with RG58). Also should I put the choke near the 9:1 balun or
near my bev switching box?

Thanks in advance.

73's Filipe Lopes
CT1ILT - CR6K
F4VPX - TM3M

_
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Re: Topband: ADC Overload

[Richard (Rick) Karlquist]

Then what if we *deliberately* inject hundreds, if not thousands of discrete RF 
carriers into our SDR receivers from say...an internal RF carrier or noise 
generator, mixed with the desired RF signal to mitigate OL caused by a few 
strong carriers?  It would be interesting to see the math and note what, if any 
reasonable limits apply, even if the amount of OL protection is small but there 
nonetheless.  If this is a viable form of OL mitigation, then by now, someone 
must have already addressed this, possibly in an academic or IEEE paper?

Paul, W9AC



That roughly describes the FM broadcast band near San Bruno
Mountain, south of San Francisco, which is chock full of
FM transmitter sites.  It is an extremely difficult RF
environment.  The picket fence spectrum definitely is
not beneficial.  Instead, the stations mix with each other
in the receiver front end and fill in any clear channels
with garbage.  I did some consulting for a company that
made FM-SCA receivers and developed an 8 stage voltage tuned
preselector for their receiver that worked as well as
the six stage air variable preselector in my circa 1978
Technic's tuner that sold for $450 at that time.  I also
tried a WJ mixer with 1/2 watt LO drive as the front end
of a superhet, but without a preselector.  There was
no comparison; the non preselected high power mixer
was nowhere near as good as the preselected receivers.
Of course, an ordinary car radio driven near the
mountain is far worse than than any of the above.

At the Maker Faire a couple of years ago, they had
a start up company that was exhibiting an FM receiver
that digitized the entire FM band.  I'd like to see
what that would have done around San Bruno Mountain.

Rick N6RK
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Re: Topband: ADC Overload

[Paul Christensen]

>"The favorable SDR averaging doesn't apply when the RF voltage at the receiver 
>input is dominated by one huge signal, and if that signal exceeds the 
>capability of the ADC in the radio, overload can definitely occur. So, 
>although I believe that nearly all manufacturers will soon migrate to superior 
>SDR technology, the "big gun" multi-multi contesters may want to hang onto 
>their old Yaesu/ Icom/Kenwood transceivers (or else use bandpass filters on 
>the inputs of their SDR rigs)!
73, Jim W8ZR"

Nice explanation of CLT in this context, Jim.   So, as you and Tom point out, 
1, 2 or 3 extremely strong stations falling within the wideband SDR input can, 
and does cause severe OL effects in our SDR receivers.  

Then what if we *deliberately* inject hundreds, if not thousands of discrete RF 
carriers into our SDR receivers from say...an internal RF carrier or noise 
generator, mixed with the desired RF signal to mitigate OL caused by a few 
strong carriers?  It would be interesting to see the math and note what, if any 
reasonable limits apply, even if the amount of OL protection is small but there 
nonetheless.  If this is a viable form of OL mitigation, then by now, someone 
must have already addressed this, possibly in an academic or IEEE paper?

Paul, W9AC

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Re: Topband: Commond mode choke for Beverage

[shristov]

 Eduardo Araujo via Topband  wrote:

> My two cents..It was interesting during the installation of 
> the last beverage, we have only #31 core, so we placed it at the 
> receiver side. Disconnecting the coax at the bev feed point and 
> shorting the coax there, many AM broadcast stations could be 
> heard and some of them strong, indicating that even though one 
> choke was at the receiver side the coax was acting like an 
> antenna. The coax was just lying on the ground and is 40/50 mts 
> long. 

> When we got more cores and placed one choke at that place close 
> to the short, repeating the test before and after most broadcast 
> vanished and only one could be heard very week.


This is exactly as expected.

In the first case you fed all the RF received by the outer surface of the coax
directly inside the coax, and directly to your RX input.

In the second case, a significant isolating impedance was added
and the said RF was attenuated.

73,

Sinisa  YT1NT, VE3EA
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Re: Topband: ADC Overload

[Jim Garland]

Interesting comments, Steve, and to me quite on the mark. (In an ealier life, I 
was a physics prof, though I've forgotten most of what I once knew).

Re the comment by another list member that "there are various distractions such 
as the Central Limit Theorem...that don't add much to the discussion":  On the 
contrary, I believe the CLT is actually crucial to this discussion. Here's my 
attempt at an intuitive explanation of the CLT using a _very_ simplified 
example. I hope this contributes to this interesting discussion.

Suppose we have an SDR radio that hears two identical signals, and that the ADC 
in the receiver overloads when the instantaneous antenna voltage at the 
receiver input is greater than +/- 5V. Now let's assume that each of our 
identical signals has a maximum instantaneous RF voltage of +/- 3V, so that the 
receiver will overload when both signals add up to give either +6V or -6V. The 
question that the Central Limit Theorem addresses is how frequently this 
overload condition will occur. Here's how it works.

We'll keep things simple by assuming each of our two signals can take on only 
seven values of voltage: +3V, +2V,+1V, 0V, -1V, -2V, and -3V. (In reality of 
course, for a CW signal, the signals are sine waves varying continuously from 
+3V to -3V.) Every time the SDR samples these signals, it sees the 
instantaneous sum of their voltages. Since each signal has seven possible 
values, the sum of the voltages can have 7x7=49 possible values, which range 
from +6V down to -6V. 

If you make a list of all possible combinations of these two signals, you'll 
find that of the 49 possibilities, 0V comes up seven times, 1V comes up six 
times, 2V comes up 5 times and so forth, until you get to 6V (when the maximum 
value of signal adds up exactly). The reason 0V comes up seven times is because 
there are seven ways to get 0 by adding the voltages from the two signals, 
i.e., 0V plus 0V, +1V plus -1V, -1V plus +1V, +2V plus -2V, -2V plus +2V, +3V 
plus -3V, and -3V plus +3V. By contrast, there is only one way to get +6V, 
which is +3V plus +3V, and similarly for --6V.

Now if the ADC in the receiver overloads at any voltage greater than  +/- 5V, 
as we have assumed, then it will overload only two times in every 49 samples, 
once when the voltage is +6V and once when the voltage is -6V. If you draw a 
graph of all the possible combinations of voltages, plotting the numbers of 
times each combination of voltages comes up, you'll see that the graph 
resembles a bell-shaped curve, (called a "normal" distribution) peaked at zero. 
The maximum values of +6V and -6V are at the tail ends of the distribution.

So in this simplified example, our SDR radio will overload 2 out of every 49 
samples, or about four percent of the time. That's not terrible, but not 
wonderful either. It means that we'd hear a pop in our receiver about four 
percent of the time. But suppose we let our two signals take on a continuous 
range of values between +3V and -3V. instead of only seven possible values. 
Unforunately, things don't get much better. The data points on our bell-shaped 
curve would smooth out, but we'd still overload roughly four percent of the 
time. The general shape of the curve doesn't change.

But...here's the interesting thing. Suppose instead of only two signals, we 
have thousands of signals appearing at our antenna terminals, and we'll 
continue to assume each of our thousands of signals varies from +/- 3V. Now 
when we add up the voltages of each of these signals, we find something 
remarkable. The sums of the voltages of all these signals is still a 
bell-shaped curve peaked at zero volts and extending from +6V down to -6V, but 
with one significant change. The bell-shaped curve narrows in, becoming very 
sharply peaked at 0V. The extremes of the curve, which would overload our 
receiver, almost never happens. This peaking of the curve is what the Central 
Limit Theorem tells us, and basically it is the reason SDR radios are in most 
cases nearly immune from overload. The more signals we're hearing with our 
receiver, the closer those voltages add up to zero. One can dress up this 
example with sophisticated math, which is what the CLT does, but the concept is 
actually very simple.

To me, this immunity to overload is the huge advantage SDR radios have over 
their superhet counterparts. In a conventional superhet receiver, with roofing 
filters and IF crystal filters, the averaging of signal voltages takes place 
only within the passband of the receiver. That's why a guy with a S9+60db 
signal who is 1 kHz away from the weak DX station you're trying to copy can 
wipe out your receiver: the RF voltage from his signal overloads the front end 
and IF amplifiers in the receiver. In an SDR, by contrast his RF voltage gets 
averaged out by all the other signals in the entire spectrum. Once the spectrum 
is digitized, which the DAC does immediately at the antenna input terminals, 
there are no more 

Re: Topband: High Pass Filter

[m.r.c.]

It is shown with RCA connectors.  Is it available with
F?
BNC?
I have generally found RCA connectors to be unsatisfactory in the long term for a variety 
of reasons generally revolving around the "Astro" plate hard nickel surfaces.  A large 
number of 160 receive antenna systems are built with type F connectors with generally good 
results - as well as it being a threaded connector instead of a slip on (read: slip off in 
the middle of the contest)


thanks

Robin WA6CDR

 Original Message - 
From: "Jay Terleski" 

To: 
Sent: Monday, October 12, 2015 09:03
Subject: Topband: High Pass Filter



"Where can I find a schematic for a good high pass filter that rolls off at
1700 kHz?"

Hopefully with permission of the moderator I suggest you might look at our
inexpensive filters.  The specs are good even at 1.7 MHz
http://arraysolutions.com/Products/AS160HPF.htm

Jay Terleski
President
Array Solutions
214 954 7140
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Re: Topband: Commond mode choke for Beverage

[Eduardo Araujo via Topband]

>> With these ferrites I ask the same question, should I put the choke close
>> to the 9:1 Balun or near the switching box and how many turns? some bevs
>> have the feed point at +- 60m away from the switching box.

My two cents..It was interesting during the installation of the last 
beverage, we have only #31 core, so we placed it at the receiver side. 
Disconnecting the coax at the bev feed point and shorting the coax there, many 
AM broadcast stations could be heard and some of them strong, indicating that 
even though one choke was at the receiver side the coax was acting like an 
antenna. The coax was just lying on the ground and is 40/50 mts long. 
When we got more cores and placed one choke at that place close to the short, 
repeating the test before and after most broadcast vanished and only one could 
be heard very week.'73 Eddie, LU2DKT 


   
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Re: Topband: High Pass Filter

[Richard (Rick) Karlquist]

On 10/12/2015 9:03 AM, Jay Terleski wrote:

"Where can I find a schematic for a good high pass filter that rolls off at
1700 kHz?"

Hopefully with permission of the moderator I suggest you might look at our
inexpensive filters.  The specs are good even at 1.7 MHz
http://arraysolutions.com/Products/AS160HPF.htm

Jay Terleski


The specs look good as far as they go, but the apparently tiny
inductors may have issues of core distortion on strong signals.
There are many reports of distortion in similarly small transformers.
Has the filter been tested for distortion with realistically
high signal levels?

I would rather have F connectors than RCA phono jacks.

Cable assemblies with RCA's are normally intended for audio,
and the shield is usually a joke for RF:  a single layer of
wires that spiral around, not even braid.  You can homebrew
good RF cables with the right version of RCA connector and
good cable, but it is a lot of trouble.  Also, the center
conductor contact in many jacks is unreliable even for audio.

Rick N6RK
_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: Commond mode choke for Beverage

[Filipe Lopes]

Thanks Jim and all for the help.

Mix #31 cores are already ordered in mouser.

73's cu on low bands
Filipe LOPES
CT1ILT CR6K

Sent from my SAMSUNG GALAXY S4
Em 12/10/2015 17:39, "Jim Brown"  escreveu:

> On Mon,10/12/2015 6:51 AM, Filipe Lopes wrote:
>
>> With these ferrites I ask the same question, should I put the choke close
>> to the 9:1 Balun or near the switching box and how many turns? some bevs
>> have the feed point at +- 60m away from the switching box.
>>
>
> Use the #31 material. Wind at least 20 turns of RG58 around it. Place it
> as close to the 9:1 transformer.
>
> 73, Jim K9YC
> _
> Topband Reflector Archives - http://www.contesting.com/_topband
>
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Topband: High Pass Filter

[Jay Terleski]

"Where can I find a schematic for a good high pass filter that rolls off at
1700 kHz?"

Hopefully with permission of the moderator I suggest you might look at our
inexpensive filters.  The specs are good even at 1.7 MHz
http://arraysolutions.com/Products/AS160HPF.htm

Jay Terleski
President
Array Solutions
214 954 7140
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Re: Topband: FW: Commond mode choke for Beverage

[Jim Brown]

On Mon,10/12/2015 8:23 AM, Bill Hider wrote:

Use 9 TURNS on a core-stack of five (5) of  P/N 2631803802 cores. That’s the 
Mix #31 core.


Bill,

A 5-high stack of cores is only needed to handle high power. This is an 
RX antenna, so suitable choking Z can be obtained with more turns on a 
single core. See the measured data for 1-14 turns of small diameter wire 
on #31, #43, #77, #78, and #61.  #31 is the best material below 5 MHz.


73, Jim K9YC
_
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Re: Topband: Commond mode choke for Beverage

[Jim Brown]

On Mon,10/12/2015 6:51 AM, Filipe Lopes wrote:

With these ferrites I ask the same question, should I put the choke close
to the 9:1 Balun or near the switching box and how many turns? some bevs
have the feed point at +- 60m away from the switching box.


Use the #31 material. Wind at least 20 turns of RG58 around it. Place it 
as close to the 9:1 transformer.


73, Jim K9YC
_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: Commond mode choke for Beverage

[Jim Brown]

On Mon,10/12/2015 5:45 AM, Filipe Lopes wrote:

I am about to add a common mode choke to isolate the antenna from its
feedline to each of my beverages and I only have FT240-61 ferrites.


#61 is a terrible material for use as a common mode choke below 500 MHz. 
Try to find #31 or #43, and wind LOTS of turns.


73, Jim K9YC
_
Topband Reflector Archives - http://www.contesting.com/_topband

Topband: FW: Commond mode choke for Beverage

[Bill Hider]

Felipe,

 

I just now built  & tested what you need.

 

I tried 7 & 8 turns, but it resolved too high in freq.

 

Use 9 TURNS on a core-stack of five (5) of  P/N 2631803802 cores. That’s the 
Mix #31 core.

 

For the choke windings, make the windings VERY tight to the core-stack.

To do that, you will need 79 INCHES of RG-58/U – for the windings alone.  

ADD to that what you need for a pigtail and connectors.

 

Here is what I measured after I built the above.

As measured on my DG8SAQ VNWA Vector Network Analyzer:

1.8 MHz   Zmag = 12,230 Ohms, Rs = 9,201 Ohms, 41.8 dB  Common Mode Attenuation

1.9 MHz   Zmag = 13,211 Ohms, Rs = 10,831 Ohms, 42.47 dB  Common Mode 
Attenuation

2.0 MHz   Zmag = 14,083 Ohms, Rs = 12,414 Ohms, 43.03 dB  Common Mode 
Attenuation

 

Put the choke close to the 9:1 matching device.  1 Foot from the 9:1 will be 
fine.

 

If you want to, add another choke (9T on 5 Cores) 1 foot from the switch box.

 

If you have any questions, please email me:

N3RR (at) erols.com

 

I can email you the frequency plot from my VNWA if you want it.

 

Please let me know how this works for you.

 

73 & GL!

 

Bill N3RR

 

 

  _  

From: "Filipe Lopes" 
To: "JC" 
Cc: "topBand" 
Sent: Monday, October 12, 2015 1:51:43 PM
Subject: Re: Topband: Commond mode choke for Beverage

Hello JC,

Thanks for your answer.

I just ordered a few 2631803802 and 5943003801 from mouser.

With these ferrites I ask the same question, should I put the choke close
to the 9:1 Balun or near the switching box and how many turns? some bevs
have the feed point at +- 60m away from the switching box.


73's Filipe Lopes
CT1ILT - CR6K
F4VPX - TM3M

2015-10-12 15:40 GMT+02:00 JC :

> Hi Filipe
>
> Zero , you should use material #31  or #77 , The core you have is not good
> for low bands.
>
> JC
> N4IS
> -Original Message-
> From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Filipe
> Lopes
> Sent: Monday, October 12, 2015 8:46 AM
> To: topBand 
> Subject: Topband: Commond mode choke for Beverage
>
> Hi guys,
>
> I am about to add a common mode choke to isolate the antenna from its
> feedline to each of my beverages and I only have FT240-61 ferrites. My
> question is how many turns should I do on the ferrite using RG58 (all my
> bevs are fed with RG58). Also should I put the choke near the 9:1 balun or
> near my bev switching box?
>
> Thanks in advance.
>
> 73's Filipe Lopes
> CT1ILT - CR6K
> F4VPX - TM3M
> _
> Topband Reflector Archives - http://www.contesting.com/_topband
>
>
_
Topband Reflector Archives - http://www.contesting.com/_topband

 

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2015.0.6172 / Virus Database: 4435/10802 - Release Date: 10/12/15

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Re: Topband: Commond mode choke for Beverage

[shristov]

With 5943003801 and RG58, closely fill-in a single layer,
leaving 10-15 mm on the outside perimeter unused.
That should be ~16 turns, giving you impedance near 4000 Ohm.

Such a choke should be placed close to all points where
the current on the outer surface of the coax shield
can pass to the coax inside space.

This usually means near RX connector, and at the Beverage end of the feeding 
coax.
If the feed line is very long, then a few chokes may be inserted here and there.

But take care to make all coax joints completely shielded,
otherwise chokes may be bypassed.


73,

Sinisa  YT1NT,  VE3EA



- Originalna poruka -
Pošiljalac: Filipe Lopes 
Datum: Ponedeljak, Oktobar 12, 2015 15:52
Tema: Re: Topband: Commond mode choke for Beverage
Primalac: JC 
Cc: topBand 

> Hello JC,
> 
> Thanks for your answer.
> 
> I just ordered a few 2631803802 and 5943003801 from mouser.
> 
> With these ferrites I ask the same question, should I put the 
> choke close
> to the 9:1 Balun or near the switching box and how many turns? 
> some bevs
> have the feed point at +- 60m away from the switching box.
> 
> 
> 73's Filipe Lopes
> CT1ILT - CR6K
> F4VPX - TM3M
> 
> 2015-10-12 15:40 GMT+02:00 JC :
> 
> > Hi Filipe
> >
> > Zero , you should use material #31  or #77 , The core you 
> have is not good
> > for low bands.
> >
> > JC
> > N4IS
> > -Original Message-
> > From: Topband [mailto:topband-boun...@contesting.com] On 
> Behalf Of Filipe
> > Lopes
> > Sent: Monday, October 12, 2015 8:46 AM
> > To: topBand 
> > Subject: Topband: Commond mode choke for Beverage
> >
> > Hi guys,
> >
> > I am about to add a common mode choke to isolate the antenna 
> from its
> > feedline to each of my beverages and I only have FT240-61 
> ferrites. My
> > question is how many turns should I do on the ferrite using 
> RG58 (all my
> > bevs are fed with RG58). Also should I put the choke near the 
> 9:1 balun or
> > near my bev switching box?
> >
> > Thanks in advance.
> >
> > 73's Filipe Lopes
> > CT1ILT - CR6K
> > F4VPX - TM3M
> > _
> > Topband Reflector Archives - http://www.contesting.com/_topband
> >
> >
> _
> Topband Reflector Archives - http://www.contesting.com/_topband
_
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Re: Topband: Commond mode choke for Beverage

[shristov]

If you must use FT240-61, then in a single layer about 18 turns of RG58 would 
fit,
which should give you ~600 Ohms on 1.8 MHz. That would be very good for a 
dipole,
but for a Beverage a much higher impedance is needed. Try to fit as many turns
as possible, until there is no more room in the center of the core.

Alternatively, use RG174. In a single layer you should be able to put ~32 turns,
which will give you a respectable 2000 Ohms on 1.8 MHz.  But in this case take 
care
to make all coax joints (RG174 to RG58) completely shielded, eg. by using a 
copper foil.

73,

Sinisa  YT1NT, VE3EA



- Originalna poruka -
Pošiljalac: JC 
Datum: Ponedeljak, Oktobar 12, 2015 15:40
Tema: Re: Topband: Commond mode choke for Beverage
Primalac: 'Filipe Lopes' , 'topBand' 

> Hi Filipe
> 
> Zero , you should use material #31  or #77 , The core you 
> have is not good
> for low bands.
> 
> JC
> N4IS
> -Original Message-
> From: Topband [mailto:topband-boun...@contesting.com] On Behalf 
> Of Filipe
> Lopes
> Sent: Monday, October 12, 2015 8:46 AM
> To: topBand 
> Subject: Topband: Commond mode choke for Beverage
> 
> Hi guys,
> 
> I am about to add a common mode choke to isolate the antenna 
> from its
> feedline to each of my beverages and I only have FT240-61 
> ferrites. My
> question is how many turns should I do on the ferrite using RG58 
> (all my
> bevs are fed with RG58). Also should I put the choke near the 
> 9:1 balun or
> near my bev switching box?
> 
> Thanks in advance.
> 
> 73's Filipe Lopes
> CT1ILT - CR6K
> F4VPX - TM3M
> _
> Topband Reflector Archives - http://www.contesting.com/_topband
> 
> _
> Topband Reflector Archives - http://www.contesting.com/_topband
_
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Re: Topband: Commond mode choke for Beverage

[Filipe Lopes]

Hello JC,

Thanks for your answer.

I just ordered a few 2631803802 and 5943003801 from mouser.

With these ferrites I ask the same question, should I put the choke close
to the 9:1 Balun or near the switching box and how many turns? some bevs
have the feed point at +- 60m away from the switching box.


73's Filipe Lopes
CT1ILT - CR6K
F4VPX - TM3M

2015-10-12 15:40 GMT+02:00 JC :

> Hi Filipe
>
> Zero , you should use material #31  or #77 , The core you have is not good
> for low bands.
>
> JC
> N4IS
> -Original Message-
> From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Filipe
> Lopes
> Sent: Monday, October 12, 2015 8:46 AM
> To: topBand 
> Subject: Topband: Commond mode choke for Beverage
>
> Hi guys,
>
> I am about to add a common mode choke to isolate the antenna from its
> feedline to each of my beverages and I only have FT240-61 ferrites. My
> question is how many turns should I do on the ferrite using RG58 (all my
> bevs are fed with RG58). Also should I put the choke near the 9:1 balun or
> near my bev switching box?
>
> Thanks in advance.
>
> 73's Filipe Lopes
> CT1ILT - CR6K
> F4VPX - TM3M
> _
> Topband Reflector Archives - http://www.contesting.com/_topband
>
>
_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: Commond mode choke for Beverage

[JC]

Hi Filipe

Zero , you should use material #31  or #77 , The core you have is not good
for low bands.

JC
N4IS
-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Filipe
Lopes
Sent: Monday, October 12, 2015 8:46 AM
To: topBand 
Subject: Topband: Commond mode choke for Beverage

Hi guys,

I am about to add a common mode choke to isolate the antenna from its
feedline to each of my beverages and I only have FT240-61 ferrites. My
question is how many turns should I do on the ferrite using RG58 (all my
bevs are fed with RG58). Also should I put the choke near the 9:1 balun or
near my bev switching box?

Thanks in advance.

73's Filipe Lopes
CT1ILT - CR6K
F4VPX - TM3M
_
Topband Reflector Archives - http://www.contesting.com/_topband

_
Topband Reflector Archives - http://www.contesting.com/_topband

Topband: Commond mode choke for Beverage

[Filipe Lopes]

Hi guys,

I am about to add a common mode choke to isolate the antenna from its
feedline to each of my beverages and I only have FT240-61 ferrites. My
question is how many turns should I do on the ferrite using RG58 (all my
bevs are fed with RG58). Also should I put the choke near the 9:1 balun or
near my bev switching box?

Thanks in advance.

73's Filipe Lopes
CT1ILT - CR6K
F4VPX - TM3M
_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: ADC Overload

[Stephen Hicks, N5AC]

On Sun, Oct 11, 2015 at 5:13 PM, Mike Waters  wrote:

> SDR fascinates me, and I intend to experiment with the technology on 160
> meters starting with a Softrock Xtall Lite 9.0 and the matching switchable
> BPF.
>

​This is how a lot of people get started.  It's a very cool way to
inexpensively dip your toes in the water and understand what's going on and
how you might be able to use it, etc.​

​73,
Steve​


Stephen Hicks, N5AC
VP Engineering
FlexRadio Systems™
4616 W Howard Ln Ste 1-150
Austin, TX 78728
Phone: 512-535-4713 x205
Email: st...@flexradio.com
Web: www.flexradio.com
Click Here for PGP Public Key




*Tune In Excitement™*
PowerSDR™ is a trademark of FlexRadio Systems
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