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Author Topic: bigger LOG.....  (Read 532 times)

Offline IQ_imbalance

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bigger LOG.....
« on: December 04, 2021, 1956 UTC »
Getting ready to embark on a great experiment....expanding my current LOG (~8x10m) quite a bit.  Going to run around the house (driveway crossing be damned) for a 35x20m loop. 

Fingers crossed...if it works i'll be able to move my feed line much much closer to the shack in addition to whatever additional benefits a larger antenna might have.....

Now if i can only find my yard staples....
LOG/NE-SW unterminated BOG/DJ-130/800Mhz Yagi
AFEDRI SDR-Net ICF-SC1 SDS-200 various RTL-SDR
Central MD

Offline IQ_imbalance

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Re: bigger LOG.....
« Reply #1 on: December 04, 2021, 2155 UTC »
....aaaaand noise.  Lots and lots of noise.  Put a broadcast HPF on the coax, but that didn't really help :( .  Tried playing around w/ the gain, and still no joy.  Going to see if it gets better this evening as sometimes there's periodic QRM around the neighborhood.....


This was with the smaller loop...although not this evening.


LOG/NE-SW unterminated BOG/DJ-130/800Mhz Yagi
AFEDRI SDR-Net ICF-SC1 SDS-200 various RTL-SDR
Central MD

Offline ChrisSmolinski

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Re: bigger LOG.....
« Reply #2 on: December 04, 2021, 2159 UTC »
Noise or overload?  Which SDR? Did you try backing down the gain?
Chris Smolinski
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Offline IQ_imbalance

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Re: bigger LOG.....
« Reply #3 on: December 04, 2021, 2221 UTC »
Noise or overload?  Which SDR? Did you try backing down the gain?
AFEDRI-SDR.  Don't think it's overload, it's not blanketing across the whole spectrum (and, if it matters the SDRDX OVL light isn't flashing!).  I have an AM station close so thought that might be the issue but the HPF is working great as I barely see anything under 2.5MHz even with the gain pushed up. If i drop the gain i lose pretty much even broadcast HF signals....

Thought it might be the hot tub since the antenna runs near that (and my heat pump) but shut those off and the noise persists.  Suppose it could be the neighbor's....

here's one of the 'hot spots'....the noise spikes are about 26.5kHz apart.....
« Last Edit: December 04, 2021, 2237 UTC by IQ_imbalance »
LOG/NE-SW unterminated BOG/DJ-130/800Mhz Yagi
AFEDRI SDR-Net ICF-SC1 SDS-200 various RTL-SDR
Central MD

Offline IQ_imbalance

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Re: bigger LOG.....
« Reply #4 on: December 05, 2021, 1605 UTC »
going to try one more thing....at the moment my antenna feeds into a balun probably 80 feet from my shack, so there's a pretty significant run of coax between there and my radio.  Since the antenna now goes all the way around the house, i can tap into it probably 6 feet away now.  Will do that, drop the gain, and see what happens. 

At the moment I can run the gain all the way up on 20m, but anything lower and i have to drop it by half and pretty much lose any useful signal. 
« Last Edit: December 05, 2021, 1607 UTC by IQ_imbalance »
LOG/NE-SW unterminated BOG/DJ-130/800Mhz Yagi
AFEDRI SDR-Net ICF-SC1 SDS-200 various RTL-SDR
Central MD

Offline IQ_imbalance

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Re: bigger LOG.....
« Reply #5 on: December 05, 2021, 2108 UTC »
OK, I give up.  Apparently any antenna that runs in my backyard picks up a hell of a lot of QRM from somewhere.  Probably something in my office, but who knows. 

Back to the LOG in the front yard and it's very long coax run. 
LOG/NE-SW unterminated BOG/DJ-130/800Mhz Yagi
AFEDRI SDR-Net ICF-SC1 SDS-200 various RTL-SDR
Central MD

Offline kris

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Re: bigger LOG.....
« Reply #6 on: January 11, 2022, 0006 UTC »
  Well, you have terrible disruptions!
Something similar occurs periodically in my QTH, but the signal peaks are more rounded / fuzzy, the transmission width is probably up to 1 MHz. Someone posted a similar image with the comment that these are interference from LED power supplies. I did not find any dependence on the time of day or devices turned on in my apartment / neighborhood. Having compared three antennas with different directional characteristics, I found that the highest level is on a dipole antenna hanged 35m above the ground,
and the lowest on a dipole at a height of 1.5m. This suggests that the signal comes at a low elevation angle, i.e. far away. The signal appears in not very long cycles and is sometimes synchronously tuned by several +/_ kHz. I suspect this is some kind of OTHR in my case. The moment of start and end of the transmission is clear as on / off, not a slow ramp.
   Maybe in your situation the only antenna that enables satisfactory reception will be the magnetic loop?
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