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


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


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


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


VE3VXO
 

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


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


Rob Robinett
 

The WebSDR system seems to best address the latency issue of the Kiwi and many other SDRs and thus more popular with ham operators.

You can compare the KFS WebSDR at http://kfswebsdr.wsprdaemon.org:8901/ 

There is more information about those KFS systems at http://kfs.wsprdaemon.org:81/

The KFS antennas suffer from some switching power supply RFI created by the cell site equipment co-located on one of the HF antenna towers, but still KFS is the premier listening site on the West Coast.


On Sat, Jul 24, 2021 at 10:22 AM Glenn Elmore <n6gn@...> wrote:

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



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