Re: [IRCA] Rockworks 4 DXpedition - April 7th

[Guy Atkins <dx@xxxxxxxxxxxxx>]

Hi Nick,

Thanks for your comments. I agree that the Flag noise was unacceptably bad.
I've never noticed a noise floor so high on a (SDR) DXpedition before. If I
had realized it sooner I might have swapped out the FLG100LN head unit for
my other one. Hopefully one of them hasn't gone bonkers. I'll be putting up
the same loop on my antenna rotor at home, and can experiment with
different FLG100LN head units.

I've posted my results from today the 8th, and the substitute ALA100M
antenna continues to have very low noise and seems to perform well...
except for the lack of DUs and TPs to hear! Chuck's much larger Flag
(closer to 18 x 15 ft. than what I stated earlier) had basically the same
results again this morning. I'm really glad we were together at Rockworks
4, as it's less likely that we both have lousy antennas. Poor propagation
on these dates and at this spot is appearing more likely. I was hoping for
a real haul of DX like I had last November with a smaller-yet loop at the
same cliff.

Sorry, I didn't check >1600 kHz, as I'm not in the habit of DXing above
there (I'm stuck in the *pre*-extended AM band days :^) I'll check those
frequencies on the recordings after I return home.

You'll see in my report from this morning that my background noise floor
<520 and >1700 kHz was at -120 dBm. I'd suspect that our two brands of SDRs
are very close in measured signal strength. They are both designed like
spectrum analyzers in the sense that they give the actual signal strength
at the antenna input.

In hindsight, I think I should have really made room for the 12-inch FSL in
my vehicle! It would have been verrrrry interesting to peak it on some
frequencies for comparisons to the Flags and ALA100M loop.

Guy



---------------------------------------------------------------------------------------------------------------------
> From: Nick Hall-Patch <nhp@xxxxxxxx>
> To: Mailing list for the International Radio Club of America <
> irca@xxxxxxxxxxxxxxxx>
> Cc:
> Date: Tue, 08 Apr 2014 05:37:50 +0000
> Subject: Re: [IRCA] Rockworks 4 DXpedition - April 7th
> No stations above 1600kHz this morning, Guy?   1611 and 1629 were briefly
> close to audio here for a minute or two.
>
> The noise in your small Flag seems quite bad.   A small (4' on a side)
> ALA100 east-west loop here delivers
> -115dB (relative to full scale on the NetSDR) below 520kHz, and  -105dB
> above 1700kHz.   KAPS-660, right in line with the loop is at -65dB.    My
> full scale east-west FLG100 shows -100dB noise both above and below the MW
> band, and KAPS is at about -40dB when not nulled.     (sorry, I don't have
> a Perseus here for direct comparison with your observations)
>
> So the Flag has at least 25dB more oomph, but nothing like that much extra
> noise.  (a 50 ohm dummy delivers about -120dB noise floor).
>
> I wonder where your extra noise is coming from?
>
> best wishes,
>
> Nick
>
>
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