Noise graph kph-station

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Noise graph kph-station

Ulli
Hi Rob,
this is my first post in the new forum. From now on, I will post WD-related issues exclusively here, as it is very specific, not general Kiwi-sdr related...

I have a question about the noise plot of kph, specifically the 2200/630m graphs. I guess, the graphs may be written with some correction - may be 20db or more less, than the real calibrated value should be.

If I look to the graphs from the Northern Utah group, the VLF plots look more realistic to me, even at the very quit kph site. I can hardly believe -140dbm/Hz on 2200 at midday...

In my graphs for each antenna, I also included mismatch error loss (calculated from the network analyser measurements). I found a nice calculator on the Internet:
https://chemandy.com/calculators/return-loss-and-mismatch-calculator.htm

Currently (during summer) I want to use my longwires a bit more often. These antenna do not have perfect match to the coax fed (even not with the impedance transformers). However with very well common-mode chokes, they receive very well. But SWR on some bands is 1:10 or even higher (2200/630m). So what is the loss, which occurs due to the mismatch itself ? The above calculator is a nice tool, as I can measure the mismatch very accurately with the network analyser.
Additional loss occurs due to high SWR on lossy feedline as well - also that is included in my figures...

Another issue is the Noisefactor of the pre-amp.
The longwires currently run without any pre-amp, but when using the W7IUV pre-amps I calculated additional 5db loss from the noise of the pre-amp... (of coarse with almost 20db gain the net result is about 14-15db gain). But the amp-noise is certainly something we should not forget, in the conf. file...

Unfortunately in summer it is very difficult in my small garden to place large V-beams in directions, which are useful. The fields are for vegatibles and the cows in summer...
However I still think, they are the best broadband gain antennas we can use in a true broadband application (kiwi as a webreceiver). I am curious if someone ever try terminated V-beams for reception...

regards,
Ulli, ON5KQ



Rob
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Re: Noise graph kph-station

Rob
Hi Ulli,

I too am perplexed by the noise level reports on all bands at KPH.

Due to National Park Service restrictions, I can't measure the transmission lines or antennas.  But I am told both the TCI-530 and the Marconi-T transmission lines a very, very low loss coax.  When the KPH site is reopened, I will use my NanoVNA to measure at the transmission line output and perhaps gain some better insight into it.

KPH HF distribution system:

TCI-530  ===> 2-way ====> KPH dist amp
              ||           ||=======> AMBF =====> Clifton ==== 50 ft RG-58  ====> 30 MHz LPF ====> 8-way =====> KIiw73...77
              ||                                                                                                                                                ||===100 pF ==> 15 dB gain ====> Kiwi78
              ||<====================================50 ft RG-58 ============ NanoVNA ====  10 dB Pad <====||

I have used a calibrated NanoVAN to measure the gain/loss from the TCI-530 HF antenna to the SMA feed to the Kiwis and got about +10 dB gain which includes the +23 dB gain from the Clifton, 11 dB from the 8-way splitter, and small additional losses from the filters.

For the 2200/630M system I made a similar measurement from the Marconi-T to the Kiwi72  and got about -4 dB loss from the 2-way splitter.

However the KPH noise levels differ by 10 dB or more from those recorded by the TC-530 system at KA7OEI-1.  I expect his levels are more accurate, but only 6-10 dB of loss in the transmission line at KPH would seem to explain the difference.

Join the Wednesday WD users group zoom meeting  when I'm sure we will delve into this subject once again.
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Re: Noise graph kph-station

ON5KQ
Rob, there is no doubt about the excellent location about kph-site.
Also, your measurement of gain/loss in distribution system is out of question...

What I am wondering however is the following.

Usually we like to see the daytime/nighttime difference of noiselevel . Especially on the low bands, we can see during the night the propagated (far away) noise is much higher than local noise.

When we compare stations with the same technical set-up (even same antenna TCI-530) we cannot simply take the average maximum noise during nighttime (average over month of data as max night time noise) and assume both values for that maximum should be the same, if the distance of the two stations is not too far away from each other.

Could it be, that there are small differences between the local ground and local sourrounding of the TCI antennas at the two locations, so that one antenna has a slightly different radiation angle ?

What I always find is, that the propagated noise (static crashes) during the night are very loud at kph. No local noise at all, but really loud static crashes. Asume that one antenna for whatever reason has a slightly different pattern with some "pattern spike" pointing to the south, where the thunderstorms are and the other antenna has just the opposite - some daming to the south, due to small differences...
Effect would be, that both stations have no man-made local noise (noise bottom in the graph should be same!) but one of the stations has much higher noise during the night... (noise peak is different)

If you listen to kph the propagated noise is one of the strongest of California Kiwis! That could be the reason (in addition to the highly efficient antenna) the relative difference of day and night noise is so big at kph-site...

Due to the time difference, I often listen at kph at the middle of the night, when the locals sleep...hi

My obvious experience:
I have build a full wave 80m loop (delta apex up) and feed it at the middle of the 38m long bottom wire for horizontal polarisation -  the antenna is resonant ant picks up really a lot of QRN from the south. Now, with ths loop, I have bigger day and night noise difference - even on  the higher bands with this antenna...
However in fact it hears less good than the low 60m wires (short summer Beverages) and especially compared to the V-beam, which I explained at the kiwi-Forum.
The V-beam however produces louder signals (about 6db, on higher bands 10db) but with lower noise level.
And the noise difference (day/night) is smaller than from the delta loop.

It means noise levels are depending from antenna radiation angle - the location is the same (bottom almost same, but noise peak is very different!)

I believe, when kph finally has possibility for a low angle DX antenna, the day/night noise difference may be 10db lower or even less, but this low noise antenna will hear better!

I have seen comparisons of noise graphs in a presentation you (or someone else) made, in an attempt to judge various things (quality of low noise location and more). However we need to keep attention to real antenna radiation angle and characteristics, if we make such comparisons...
Even if both locations use same technical system incl antenna!

Still hoping kph can recover one of the old V-beams originally formerly used at kph... would be also a nice attempt to keep the historical set-up "original"....

Ulli, ON5KQ

Rob
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Re: Noise graph kph-station

Rob
Hi Ulli,

I hope you can join us on the Wednesday WD Users Group where you will find much interest on this subject.  It’s  starts at 17:00CET and lasted until 20:00CET.  So don't hesitate to join late.

73,

Rob


On Sun, Apr 19, 2020 at 11:03 AM ON5KQ [via wsprdaemon] <[hidden email]> wrote:
Rob, there is no doubt about the excellent location about kph-site.
Also, your measurement of gain/loss in distribution system is out of question...

What I am wondering however is the following.

Usually we like to see the daytime/nighttime difference of noiselevel . Especially on the low bands, we can see during the night the propagated (far away) noise is much higher than local noise.

When we compare stations with the same technical set-up (even same antenna TCI-530) we cannot simply take the average maximum noise during nighttime (average over month of data as max night time noise) and assume both values for that maximum should be the same, if the distance of the two stations is not too far away from each other.

Could it be, that there are small differences between the local ground and local sourrounding of the TCI antennas at the two locations, so that one antenna has a slightly different radiation angle ?

What I always find is, that the propagated noise (static crashes) during the night are very loud at kph. No local noise at all, but really loud static crashes. Asume that one antenna for whatever reason has a slightly different pattern with some "pattern spike" pointing to the south, where the thunderstorms are and the other antenna has just the opposite - some daming to the south, due to small differences...
Effect would be, that both stations have no man-made local noise (noise bottom in the graph should be same!) but one of the stations has much higher noise during the night... (noise peak is different)

If you listen to kph the propagated noise is one of the strongest of California Kiwis! That could be the reason (in addition to the highly efficient antenna) the relative difference of day and night noise is so big at kph-site...

Due to the time difference, I often listen at kph at the middle of the night, when the locals sleep...hi

My obvious experience:
I have build a full wave 80m loop (delta apex up) and feed it at the middle of the 38m long bottom wire for horizontal polarisation -  the antenna is resonant ant picks up really a lot of QRN from the south. Now, with ths loop, I have bigger day and night noise difference - even on  the higher bands with this antenna...
However in fact it hears less good than the low 60m wires (short summer Beverages) and especially compared to the V-beam, which I explained at the kiwi-Forum.
The V-beam however produces louder signals (about 6db, on higher bands 10db) but with lower noise level.
And the noise difference (day/night) is smaller than from the delta loop.

It means noise levels are depending from antenna radiation angle - the location is the same (bottom almost same, but noise peak is very different!)

I believe, when kph finally has possibility for a low angle DX antenna, the day/night noise difference may be 10db lower or even less, but this low noise antenna will hear better!

I have seen comparisons of noise graphs in a presentation you (or someone else) made, in an attempt to judge various things (quality of low noise location and more). However we need to keep attention to real antenna radiation angle and characteristics, if we make such comparisons...
Even if both locations use same technical system incl antenna!

Still hoping kph can recover one of the old V-beams originally formerly used at kph... would be also a nice attempt to keep the historical set-up "original"....

Ulli, ON5KQ




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Rob Robinett
AI6VN
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