Date   

Re: Kiwi front end protection.

Glenn Elmore
 

I think it wasn't a Kiwi at the time, just two collocated antennas with the receiver running continuously.  The rx may have been an analog radio or an Apache/Anan dual-ADC board, I can't remember any longer, just that I could manage with a receiver running continuously while I was transmitting. It's possible that it was the Anan board with some delay.

It's possible to help a Kiwi somewhat by turning down the abuf but that doesn't solve the problem, it only helps somewhat. I often run with abuf=0.25.  Full QSK with fast CW, or even listening to one's own signal isn't very useful with any SDR I've tried.


On 7/24/21 9:50 AM, VE3VXO wrote:
On Sat, Jul 24, 2021 at 11:14 AM, Glenn Elmore wrote:
It was rather fun to be 'full QSK' on SSB or CW.
Glenn, how did you deal with the processing delay?  Here it is almost a full second through the Kiwi.  I can't handle that, my fist stops in an instant when my delayed CW hits my ears.  Turning volume knobs up and down on two sets of speakers isn't practical and is hardly QSK! I thought of using some sort of PTT/mute on the Kiwi audio but got stalled on that project.

On Kiwi protection, I added an optocoupler output to the green terminal block which is tied in with my local PTT.  The on resistance of the opto is ~5 ohms so it only gives a little extra attenuation rather than shorting the antenna directly to ground. It has handled local 500w transmitter no problem.

Joe


Re: The Pi in the FiredogSDR can run 8 channel WD

VE7VXO
 

I suspected that but wasn't sure.  I don't expect to see my FD arrive till September probably but in the mean time if you have any chance to write down the steps you used it will help me a lot and would be much appreciated!

Best regards...joe


Re: The Pi in the FiredogSDR can run 8 channel WD

Rob Robinett
 

It was a typo.  I was working on the FlyDog 

On Sat, Jul 24, 2021 at 9:34 AM VE3VXO <ve3vxo@...> wrote:
Is that a typo for Flydog, or sarcasm, or is there actually another SDR called Firedog?  I looked but came up empty?



--
Rob Robinett
AI6VN
mobile: +1 650 218 8896


Re: The Pi in the FiredogSDR can run 8 channel WD

VE7VXO
 

Is that a typo for Flydog, or sarcasm, or is there actually another SDR called Firedog?  I looked but came up empty?


Re: Kiwi front end protection.

VE7VXO
 

On Sat, Jul 24, 2021 at 11:14 AM, Glenn Elmore wrote:
It was rather fun to be 'full QSK' on SSB or CW.
Glenn, how did you deal with the processing delay?  Here it is almost a full second through the Kiwi.  I can't handle that, my fist stops in an instant when my delayed CW hits my ears.  Turning volume knobs up and down on two sets of speakers isn't practical and is hardly QSK! I thought of using some sort of PTT/mute on the Kiwi audio but got stalled on that project.

On Kiwi protection, I added an optocoupler output to the green terminal block which is tied in with my local PTT.  The on resistance of the opto is ~5 ohms so it only gives a little extra attenuation rather than shorting the antenna directly to ground. It has handled local 500w transmitter no problem.

Joe


The Pi in the FiredogSDR can run 8 channel WD

Rob Robinett
 

Despite my vow last night to not work on the FD until its serious RF input problems are solved, this morning I decided that I had spent so much time setting up access to Tom NH6Y's FD that I would spend an hour to see if wsprdaemon (WD) could be installed and run on it.  

Surprisingly, it took only about 20 minutes any many automatic package installations to get WD installed and running.  

There are plenty of CPU cycles to support 8 channel mode, but the Pi CPU is getting pretty warm at 71C.  

So the FD would benefit from a better heat sink+fan.  

The FD is posting fewer than 1/4 the spots of a local KiwiSDR which is attached to a better antenna, so I don't know how much of that difference is due to the FD's RF input problems and how much is due to the Kiwi's better antenna.  

Hopefully we will get the chance to feed the same RF to the FD and Kiwi and quantify the difference in performance.


--
Rob Robinett
AI6VN
mobile: +1 650 218 8896


Re: Kiwi front end protection.

KD2OM
 

Rolf,

I have used the Cross Country Wireless receiver protectors on mine, they work quite well.  My three kiwi's are all on passive antennas with 11 dB preamps. They are spaced about 100 feet from my transmitters, I have never had a problem as far as damage but overload does show up. I have run as much as 500 watts with the transmitters without issue.  Clint KA7OEI has designed a filter that has decreasing attenuation the higher in frequency you go which might be of some help.


73

Steve KD2OM

On 7/24/21 2:17 PM, Rolf Ekstrand wrote:
Good morning y'all,

In regards to my expansion plans I am thinking of putting up some fixed gain antennas.  However in the EU direction I have a high power DX/contester station about 1/3 of a mile away and my concern is front end overloading and protection of the Kiwi with increased gain in that direction. It is pretty bad at times as is with the omni antenna.   I had the Kiwi schematic some place, but can't find it now, and with the ongoing Kiwi bru hah hoopla the link is not seemingly accessible.    

Anyone  out there in WD land that have info on the front end protection of the Kiwi and/or experience with close in band high power transmissions.  

73 Rolf K9DZT


Re: Kiwi front end protection.

Glenn Elmore
 

Rolf,

JKS has put protection diodes at the input to the preamp on the Kiwi board which can handle significant power. But given the distance and the difficulty of ever achieving high coupling between antennas in the far field, I really doubt that you will damage anything from your contester's operation.  Even a matched dipole on your end against, say, 10 kW ERP at 1/3 mile on 14 MHz only results in 100 mW which isn't enough to cause physical damage to the Kiwi. In all likelihood things are ten's of dB safer than that. You would likely have to work very hard to actually damage a Kiwi in the circumstance you describe, I think.

Having said that, once aggregate input exceeds about -15 dBm, the top of Kiwi ADC is exceeded and things go bad immediately so you'll not be able to use it during his transmissions. But just to make the point, I've actually run nearly full duplex from my own 20m station by transmitting on a 60' high dipole and receiving on a broadband active antenna. It was rather fun to be 'full QSK' on SSB or CW.

In short, were it me, I'd not worry about physical damage but I'd be prepared to lose operation during transmission peaks.


On 7/24/21 8:17 AM, Rolf Ekstrand wrote:
Good morning y'all,

In regards to my expansion plans I am thinking of putting up some fixed gain antennas.  However in the EU direction I have a high power DX/contester station about 1/3 of a mile away and my concern is front end overloading and protection of the Kiwi with increased gain in that direction. It is pretty bad at times as is with the omni antenna.   I had the Kiwi schematic some place, but can't find it now, and with the ongoing Kiwi bru hah hoopla the link is not seemingly accessible.    

Anyone  out there in WD land that have info on the front end protection of the Kiwi and/or experience with close in band high power transmissions.  

73 Rolf K9DZT


Re: Kiwi front end protection.

Stu C
 

Morning Rolf, I can email you the schematics but many people are using back to back signal diodes, often fitted directly to the green antenna connector.
Reagrds
Stu


Kiwi front end protection.

Rolf Ekstrand
 

Good morning y'all,

In regards to my expansion plans I am thinking of putting up some fixed gain antennas.  However in the EU direction I have a high power DX/contester station about 1/3 of a mile away and my concern is front end overloading and protection of the Kiwi with increased gain in that direction. It is pretty bad at times as is with the omni antenna.   I had the Kiwi schematic some place, but can't find it now, and with the ongoing Kiwi bru hah hoopla the link is not seemingly accessible.    

Anyone  out there in WD land that have info on the front end protection of the Kiwi and/or experience with close in band high power transmissions.  

73 Rolf K9DZT


Re: Odroid XU-4 or?

Rolf Ekstrand
 

Thanks all,

Based on what Rob is saying  in regards to the capabilities of the upcoming WD 3.0 I think it's time to move beyond the SBC's like an overclocked Rpi -4/400 or the XU4 as a WD server.   I am looking at the different alternatives as I am going along, but have not yet made up my mind how to proceed with the expansion project.   

73  Rolf  K9DZT


Re: Odroid XU-4 or?

Jim Lill
 

I use an XU4 for 26 channels of WD, have been for a year+ with success

On 7/22/21 10:18 AM, Rolf Ekstrand wrote:
Greetings y'all

Thinking about making some additions here to expand my set up here as the condx are improving on the higher bands.  This means additional antennas and of course more Kiwis, and as I am running a Rpi4 here I guess there also have to be some thought about replacing this. Thus I like to put the question out there. Would for example an Odroid XU-4 be a better choice or is there something else out there in regards to reasonable priced SBC's     In regards to this I must also consider the Internet service as we are on a connection  here (Thanks Spectrum ) that consistently fails or slows down to a mere crawl.  Well that's why we use the WD, but with more Kiwis it will put more load on the system and we probably need something else than the Rpi4.

Any thoughts regarding this?

73  Rolf K9DZT



 
 


Re: Odroid XU-4 or?

Stu C
 

I was running a couple of virtual machines under VMware Esxi server for WSPR and FT8, the CPU is a i3-6100 and combined some days I'd hit about 60,000 spots.
That Virtual host is also running about four other uses at any one time, including a Virtual Win 10 desktop.

As rob says the instantaneous CPU is what seems to make a big difference, I could tell if FT8 decoding stopped as the host fan stopped the rhythmic cycling under load.

Stu


Re: Odroid XU-4 or?

Glenn Elmore
 

The eBay ThinkCentres suggested by Holger are much more capable than RPI4s and pretty small, low power and affordable. I think they can handle 50+ wspr bands even when bands are busy. 
I've been running one totally headless for some time with excellent results.

On Jul 22, 2021 7:18 AM, Rolf Ekstrand <rekstrand@...> wrote:
Greetings y'all

Thinking about making some additions here to expand my set up here as the condx are improving on the higher bands.  This means additional antennas and of course more Kiwis, and as I am running a Rpi4 here I guess there also have to be some thought about replacing this. Thus I like to put the question out there. Would for example an Odroid XU-4 be a better choice or is there something else out there in regards to reasonable priced SBC's     In regards to this I must also consider the Internet service as we are on a connection  here (Thanks Spectrum ) that consistently fails or slows down to a mere crawl.  Well that's why we use the WD, but with more Kiwis it will put more load on the system and we probably need something else than the Rpi4.

Any thoughts regarding this?

73  Rolf K9DZT



 
 


Re: Odroid XU-4 or?

Rob Robinett
 

Yes, the Pis and Odroids are not good long term platforms for WD.
I have been very happy with the used Lenovo Thinkcentre m93p Tiny with an i5/8GB which cost less than $100.  It consumes 10W at idle which jumps to 36W during the 1-=20 seconds that WD is decoding wav files. But any i5+ with 4+GB RAM is a good long term choice for WD sites.
CPU performance, reliability and low power consumption are available on many x86 platforms, just choose one which is supported by Ubuntu 20.x

On Thu, Jul 22, 2021 at 7:58 AM Edward Hammond <manager@...> wrote:

I have fun with SBCs but I don't regret recently switching to a more full blown system. 

I was lucky to have an underutilized Intel NUC in the shack. It's not new. I believe it is a 7th generation processor, dual core, not the quad.  Ubuntu was an easy install.  The CPU tests as being about the same, maybe slightly better (~10%), than the eBay used machine that Rob mentioned here a couple months ago, though I think the NUC is still more expensive (though probably less power hungry). 

A major motivator for me was that decoding FST4W with WD will be, per Rob, considerably more CPU intensive.

I literally haven't touched the NUC since the first time I ran WSPRDaemon after the install.  Except to use the display to show PSK Reporter or wspr.rocks maps while WD runs in the background.

God bless the SBCs but I'm not going back.

Edward

W3ENR



On 7/22/21 10:18 AM, Rolf Ekstrand wrote:
Greetings y'all

Thinking about making some additions here to expand my set up here as the condx are improving on the higher bands.  This means additional antennas and of course more Kiwis, and as I am running a Rpi4 here I guess there also have to be some thought about replacing this. Thus I like to put the question out there. Would for example an Odroid XU-4 be a better choice or is there something else out there in regards to reasonable priced SBC's     In regards to this I must also consider the Internet service as we are on a connection  here (Thanks Spectrum ) that consistently fails or slows down to a mere crawl.  Well that's why we use the WD, but with more Kiwis it will put more load on the system and we probably need something else than the Rpi4.

Any thoughts regarding this?

73  Rolf K9DZT



 
 



--
Rob Robinett
AI6VN
mobile: +1 650 218 8896


Re: Odroid XU-4 or?

Edward (W3ENR / K3WRG)
 

I have fun with SBCs but I don't regret recently switching to a more full blown system. 

I was lucky to have an underutilized Intel NUC in the shack. It's not new. I believe it is a 7th generation processor, dual core, not the quad.  Ubuntu was an easy install.  The CPU tests as being about the same, maybe slightly better (~10%), than the eBay used machine that Rob mentioned here a couple months ago, though I think the NUC is still more expensive (though probably less power hungry). 

A major motivator for me was that decoding FST4W with WD will be, per Rob, considerably more CPU intensive.

I literally haven't touched the NUC since the first time I ran WSPRDaemon after the install.  Except to use the display to show PSK Reporter or wspr.rocks maps while WD runs in the background.

God bless the SBCs but I'm not going back.

Edward

W3ENR



On 7/22/21 10:18 AM, Rolf Ekstrand wrote:
Greetings y'all

Thinking about making some additions here to expand my set up here as the condx are improving on the higher bands.  This means additional antennas and of course more Kiwis, and as I am running a Rpi4 here I guess there also have to be some thought about replacing this. Thus I like to put the question out there. Would for example an Odroid XU-4 be a better choice or is there something else out there in regards to reasonable priced SBC's     In regards to this I must also consider the Internet service as we are on a connection  here (Thanks Spectrum ) that consistently fails or slows down to a mere crawl.  Well that's why we use the WD, but with more Kiwis it will put more load on the system and we probably need something else than the Rpi4.

Any thoughts regarding this?

73  Rolf K9DZT



 
 


Odroid XU-4 or?

Rolf Ekstrand
 

Greetings y'all

Thinking about making some additions here to expand my set up here as the condx are improving on the higher bands.  This means additional antennas and of course more Kiwis, and as I am running a Rpi4 here I guess there also have to be some thought about replacing this. Thus I like to put the question out there. Would for example an Odroid XU-4 be a better choice or is there something else out there in regards to reasonable priced SBC's     In regards to this I must also consider the Internet service as we are on a connection  here (Thanks Spectrum ) that consistently fails or slows down to a mere crawl.  Well that's why we use the WD, but with more Kiwis it will put more load on the system and we probably need something else than the Rpi4.

Any thoughts regarding this?

73  Rolf K9DZT



 
 


Re: Question on Antenna design - will mismatch alone change antenna radiation pattern ?

ON5KQ
 

Thanks for answers. Jim and Glenn...
I am just curious, why I felt to be often unsuccesful with antennas, which are planned to be resonant on 15m (for example) usually work by far less good on a different band compared to  a well matched.

So I will try to build it during the coming summer ...

See you on Wednesday meeting...

Ulli, ON5KQ


Re: Question on Antenna design - will mismatch alone change antenna radiation pattern ?

Jim Lill
 

If the mismatched portion of the system includes the feedline, a "hot" feedline can skew the pattern in some cases.

On 7/20/21 10:37 AM, Glenn Elmore wrote:

Not claiming to be an expert but I would say that pattern is due to response in the far field.  As long as the 'matching' or other radiating mechanisms don't  have significant radiation compared to the 'antenna' then that response won't change.

Having said that, the *apparent* pattern can change. If mismatch gets high enough that other mechanisms, not intended to be included in what one calls the 'antenna', become significant compared to the desired/intended one then the pattern and performance can indeed change be different. 

This second situation is essentially what happens with common mode ingress. That which one *thinks* is the antenna is not really the total of what is providing response at the receiver.  Once intended antenna (mismatched) signals get down to the level of other signals, such as CM then the effective pattern is no longer entirely due to the intended antenna.

This problem can be aggravated by electrically small antennas which though they intercept the same aperture and, were they matched, would deliver the same signal power, deliver very small voltage or current levels due to their preamplifiers because of the low radiation resistance and high reactance and imperfect matching.

Perhaps surprisingly, were we able to perfectly match a [1 cm] dipole at 160m it would have just about the same performance as a full half wave. Of course we can't do that with materials we have, probably not even with super conductors so in practice this doesn't occur. 

But the general idea of using "something" as an antenna, no matter whether the feedpoint impedance is near something easy to access with reasonable matching materials, is perfectly fine as long as one compares the resulting mismatch to the target at a particular frequency of interest.  That target starts to get difficult at the high end of HF where we want to get increasingly close (or below) KTB. It's for this reason that either a loop, such as described by LZ1AQ, or my dipoles both fail to achieve the ITU 'quiet rural' noise floor at 10m.  More or less, it takes larger structures to get something that has a chance of 'not too bad' match over broader frequency range with a finite number of real components.


Re: Question on Antenna design - will mismatch alone change antenna radiation pattern ?

Glenn Elmore
 

Not claiming to be an expert but I would say that pattern is due to response in the far field.  As long as the 'matching' or other radiating mechanisms don't  have significant radiation compared to the 'antenna' then that response won't change.

Having said that, the *apparent* pattern can change. If mismatch gets high enough that other mechanisms, not intended to be included in what one calls the 'antenna', become significant compared to the desired/intended one then the pattern and performance can indeed change be different. 

This second situation is essentially what happens with common mode ingress. That which one *thinks* is the antenna is not really the total of what is providing response at the receiver.  Once intended antenna (mismatched) signals get down to the level of other signals, such as CM then the effective pattern is no longer entirely due to the intended antenna.

This problem can be aggravated by electrically small antennas which though they intercept the same aperture and, were they matched, would deliver the same signal power, deliver very small voltage or current levels due to their preamplifiers because of the low radiation resistance and high reactance and imperfect matching.

Perhaps surprisingly, were we able to perfectly match a [1 cm] dipole at 160m it would have just about the same performance as a full half wave. Of course we can't do that with materials we have, probably not even with super conductors so in practice this doesn't occur. 

But the general idea of using "something" as an antenna, no matter whether the feedpoint impedance is near something easy to access with reasonable matching materials, is perfectly fine as long as one compares the resulting mismatch to the target at a particular frequency of interest.  That target starts to get difficult at the high end of HF where we want to get increasingly close (or below) KTB. It's for this reason that either a loop, such as described by LZ1AQ, or my dipoles both fail to achieve the ITU 'quiet rural' noise floor at 10m.  More or less, it takes larger structures to get something that has a chance of 'not too bad' match over broader frequency range with a finite number of real components.

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