KCBQ overloads PL-380 (Re: Tecsun PL-360 3" Loopstick Testing)


pianoplayer88key
 

Ok, I went outside a little while ago and did the best crunch test I could come up with for where I am. Locally, the strongest station here is 1170 KCBQ daytime, which, even without any external antenna aid, loudly splatters several channels each way (limited to about 2 or 3 due to an almost-as-strong local on 1130) on my Panasonic RQ-SW20, a radio with selectivity comparable to the Sony SRF-M37W with sensitivity a few dB less. (A station that may have weak, but recognizable audio on the SRF-M37W just will not be there at all on the RQ-SW20).

Now, while KCBQ is strongest in the daytime (50kW, 9 miles), at night KCBQ powers down to 2.9kW, and 760 KFMB, 7 miles away, powers UP from 5kW to 50kW at night. Interestingly, though, KCBQ is stronger daytime than KFMB is nighttime, even though KFMB is closer. (This is judged by reading how wide the splatter is on my not-so-selective RQ-SW20.)
Just checked with the FCC calculator, and actual distance/heading to KCBQ's transmitter is approximately 15.031km (9.34mi), 7.08°.

Well, anyway, I took my Select-A-Tenna and PL-380, and put it up to a power pole...
http://cid-6bdd1917662288cb.skydrive.live.com/self.aspx/AM%20radio%20files/1170%20KCBQ%20-%202010-04-16/Me^J%20PL-380^J%20SAT%20@%20Power%20Pole.jpg
See the thin wooden piece running down the pole? If I put my radio and SAT up to that (like in the pic), it gives the signal some serious gain. (For example, a TIS on 1620 which is normally 24dBu barefoot is about 57dBu with the SAT at the power pole, and 41dBu with the SAT alone. Also 570 KLAC reads 60dBu at the pole w/SAT, 51dBu with SAT alone, and 31dBu barefoot.) There's another way to put it... I can't get it to overload like this, barefoot, as we're driving right by their transmitter site!
(pic of power line from one pole to the next): http://cid-6bdd1917662288cb.skydrive.live.com/self.aspx/AM%20radio%20files/1170%20KCBQ%20-%202010-04-16/PowerLine.jpg

...and made some recordings:

First, a quick comparison. First part of the recording is KCBQ barefoot, with the PL-380 held a few feet away from the SAT and power pole. About halfway through this recording, I bring the PL-380 to rest on top of the SAT (which is tuned to 1170) like in the picture above. http://cid-6bdd1917662288cb.skydrive.live.com/self.aspx/AM%20radio%20files/1170%20KCBQ%20-%202010-04-16/KCBQ%201170%20-%20PL-380%20-%20overload%20demo%20-%202nd%20half%20SAT%20@%20PowerPole.mp3
Now if you don't call that audio distortion overload when it's tuned to 1170, what do you call it?

Next, a partial harmonic series, with the SAT + power pole. I think I stopped at about the 7th or 8th harmonic. http://cid-6bdd1917662288cb.skydrive.live.com/self.aspx/AM%20radio%20files/1170%20KCBQ%20-%202010-04-16/KCBQ%201170%20-%20PL-380%20-%20partial%20harmonic%20series%20-%20SAT%20@%20PowerPole.mp3
Just to give you a little bit of an idea, the 2nd harmonic (2340kHz) was reading 63dBu, and the 3rd harmonic (3510kHz) was reading 49dBu.

Next two are the PL-380 with SAT @ Power Pole, tuning from 1170 up to 1710, then from 1170 down to 520.
http://cid-6bdd1917662288cb.skydrive.live.com/self.aspx/AM%20radio%20files/1170%20KCBQ%20-%202010-04-16/KCBQ%201170%20-%20PL-380%20-%201170%20to%201710%20-%20SAT%20@%20PowerPole.mp3
http://cid-6bdd1917662288cb.skydrive.live.com/self.aspx/AM%20radio%20files/1170%20KCBQ%20-%202010-04-16/KCBQ%201170%20-%20PL-380%20-%201170%20to%200520%20-%20SAT%20@%20PowerPole.mp3

For comparison, here's the Panasonic RQ-SW20 tuning from 1170 to 1710, then from 1170 down to 710 (stopped there), also with the SAT @ Power Pole.
http://cid-6bdd1917662288cb.skydrive.live.com/self.aspx/AM%20radio%20files/1170%20KCBQ%20-%202010-04-16/KCBQ%201170%20-%20RQ-SW20%20-%201170%20to%201710%20-%20SAT%20@%20Power%20Pole.mp3
http://cid-6bdd1917662288cb.skydrive.live.com/self.aspx/AM%20radio%20files/1170%20KCBQ%20-%202010-04-16/KCBQ%201170%20-%20RQ-SW20%20-%201170%20to%200710%20-%20SAT%20@%20Power%20Pole.mp3

I should mention those are all done in the 6kHz bandwidth... but even so I shouldn't be hearing station audio from 1170 on almost every frequency, right?

With the antenna tuned to 1170 kHz, I was getting 45 to 50 dBu between channels throughout the longwave and mediumwave bands. I didn't check for 1170 daytime like I did for 760 nighttime, but I suspect I would have been nearing 50dBu at least somewhat into the shortwave bands.

In an earlier posting I posted a log of my signal strength readings barefoot (and some with the SAT) for the PL-380. Now here's some barefoot inside a car, which gives some attenuation. You may notice that most of the time, the signal level between channels is usually 15 dBu. (All were taken in the 1 kHz bandwidth mode.)

520 - 15,00
530 - 15,00 - slight XESURF chatter
540 - 36,25 sw - XESURF (null=15,06)
550 - 15,02 - slight XESURF chatter
560 - 15,00
570 - 18,08 NW - KLAC (null=15,00)
580 - 15,00
590 - 28,00 W - KOGO's IBOC (n=15,10)
600 - 52,25 W - KOGO (null=31,25)
610 - 27,00 W - KOGO's IBOC (n=15,00)
620 - 24,21 S - XESS (null=19,03-15)
630 - 15,00 (slight KFI IBOC?)
640 - 29,25 NW - KFI (null=15,10-16)
650 - 15,00 (slight KFI IBOC?)
660 - 15,00
670 - 15,04 WNW - KIRN (null=15,00-01)
680 - 17,00 S - XEWW splatter (null=15,00)
690 - 50,25 S - XEWW (null=35,25)
700 - 15,00 S - XEWW splatter
710 - 15,10 NW - KSPN (null=15,00-01)
720 - 15,00
730 - 17,05-08 WNW - KBRT IBOC (null=15,00)
740 - 34,25 WNW - KBRT (null=17,17-20)
750 - 17-24,00 NNW - KFMB splatter
760 - 53,25 NNW - KFMB
770 - 20-22,00 NNW - KFMB splatter
780 - 15,00
790 - 17,23-20 WNW - KABC (null=15,00)
800 - 37,25 SSW - XESPN (null=15,04-07)
810 - 15,00 - XESPN splatter
820 - 15,00
830 - 15,13-18 N - KLAA (null=15,00
840 - 15,00
850 - 15,00
860 - 38,25 SSW - XEMO (null=16,16-19)
870 - 15,00
880 - 15,00
890 - 15,00
900 - 17,00 NNE - KECR splatter (null = 15,00)
910 - 48,25 NNE - KECR (null=32,25)
920 - 15,00 - KECR splatter
930 - 15,07 NW - KHJ (null=15,00-01)
940 - 15,00 - slight XEKAM splatter
950 - 34,25 SSW - XEKAM (null=19,14-22)
960 - 15,00
970 - 15,00
980 - 15,00
990 - 15,00
1000 - 24,25 NNW - KCEO (null=15,00-01)
1010 - 15,00
1020 - 15,00 NW - KTNQ
1030 - 25,16-25 S - XESDD (null=15,00-01)
1040 - 34,25 WSW - KURS (null=16,16-18)
1050 - 15,00-02 E - XED
1060 - 15,00 (slight KNX IBOC?)
1070 - 30,25 NW - KNX (null=20,02-04)
1080 - 17,00 NW - KNX IBOC
1090 - 34,25 SSW - XEPRS (null=25,23)
1100 - 19,00 N/S , 17,00 E/W
I noticed that if I pointed the radio at my strongest pest, THEN tuned the radio, it would read something like 30dBu inside the car, from about 1100 to 1300 or so (pest being 1170). If I then turned the radio to null the pest, it would drop down to 15 or 17 dBu, then if I turned back to face the pest the signal level would stay down, or maybe gain 2 dB (17-19dBu).
1110 - 19,00 NW - KDIS
1120 - 19-31,00 N - KSDO splatter
1130 - 57,25 N - KSDO (null=31,24-25)
1140 - 22-38,00 N/S - KSDO splatter , 20,00 E/W
1150 - 24,00 N/S , 22,00 E/W
1160 - 24-29,00 N/S - KCBQ splatter , 22,00 E/W
1170 - 62,25 NNE - KCBQ (null=45,25)
1180 - 22,00 N/S - KCBQ splatter, 20,00 E/W
1190 - 20,00 NW - KXMX carrier (noise beating a couple pulses/second, but too weak for actual audio) (null=22,00)
1200 - 19,00 (slight KPRZ splatter?)
1210 - 38,25 NNW - KPRZ (null=24-25,04-12)
1220 - 20,00 (slight KPRZ splatter?)
1230 - 19,00
1240 - 40,25 WSW - KNSN (null=20,18-19)
1250 - 15,00
1260 - 17,00 (slight XEAZ splatter)
1270 - 31,25 SSW - XEAZ (null=17,10-13)
1280 - 17,01-05 WNW - KFRN (null=17,00)
1290 - 15,00
1300 - 17,00
1310 - 25-26,20-22 SSW - XEC (null=17,00)
1320 - 17,00
1330 - 17,00
1340 - 17,00
1350 - 17,00
1360 - 50,25 WSW - KLSD (null=17,14-19)
1370 - 17,00
1380 - 17,00
1390 - 25,25 SE - XEKT (null=15,00-02)
1400 - 15,00
1410 - 15,00
1420 - 29,25 S - XEXX (null=15,00)
1430 - 15,00
1440 - 15,00
1450 - 15,11-13 N - KFSD (null=15,00)
1460 - 15,00
1470 - 35,25 SSW - XERCN (null=19,19-23)
1480 - 15,00 (slight XERCN splatter?)
1490 - 15,00
1500 - 15,00
1510 - 15,00
1520 - 15,00
1530 - 15,00
1540 - 15,15 - unidentified carrier, no known local (unless it's a new TIS that's testing?) on that frequency (KMPC L.A. is barely detectable (if at all) outside the car, and this bandscan is done inside where it's more attenuated)
1550 - 15,17 S - XEBG (null=15,00-01)
1560 - 15,00
1570 - 15,00
1580 - 15,00 WNW - KBLA? (or could have been KMIK but it was too faint to ID)
1590 - 15,00
1600 - 15,00
1610 - 15,00
1620 - 15,00 SSW - WNSB415 (very weak, but could ID)
1630 - 30,25 S - XEUT (null=15,12-16)
1640 - 15,00
1650 - 15,00
1660 - 15,00
1670 - 15,00
1680 - 15,00
1690 - 15,00
1700 - 32,25 S - XEPE (null=15,00-01)
1710 - 15,00

Now that I've posted a few of my local bandscan readings with my DSP radio... I'm curious as to what some of your daytime bandscans look like on your DSP radios, barefoot, and with various antennas. (They should probably be put in a separate topic, btw.)


So I may have a defective PL-380, you say, right? Does your PL-380 manage just fine, Gary? :) For example, if you go close enough to 570 KVI so that on the SRF-M37W it splatters all the way up to 1710, can you still hear 560 KPQ and TPs/TAs on 567 kHz just fine in the 1kHz bandwidth mode with no splatter from KVI, for example?

--- In ultralightdx@..., "jim_kr1s" <jkearman@...> wrote:


--- In ultralightdx@..., D1028Gary@ wrote:

With analog models like the SRF-59
and the R9012 you can actually tune the radio simply by tuning the 9'
loop
(when their distance is within 5 feet), but the DSP Ultralights
typically
receive only on their tuned frequency, no matter what frequency the
huge
loop selects.
Analog radios borrow part of the ferrite rod for the local-oscillator
(LO) inductor. You are tuning the radio with the antenna, by "pulling"
the LO. DSP radios digitally synthesize the LO; there are no tuned LO
circuits. You could use a separate inductor for the LO, but that only
moves another weak link into position, the front-end circuitry.
Portables are designed to have gain commensurate with their antennas,
and will "saturate" on strong signals.

DSP radios will overload too,. The effect is hard to discern from the
usual splatter by adjacent stations. You can demonstrate it with some
simple test equipment (two signal generators and calibrated
attenuators). Where several strong signals are close together, the radio
may sound noisy between stations, because of intermodulation
<http://en.wikipedia.org/wiki/Intermodulation> . Shielding the radio in
such a way that you can still read the meters (screen wire) or simply
taking the radio farther away from the location, will eliminate those
stations as possible causes of the problem. Location location location.
This article
<http://www.radio-electronics.com/info/receivers/overload/cross-modulati\;
on-intermodulation-intercept-point.php> simply explains the causes.

This PDF <http://neazoi.com/arrl/020708qex046.pdf%20> explains how
ARRL <http://www.arrl.org/> measures intermodulation distortion
<http://en.wikipedia.org/wiki/Intermodulation> (IMD). It's more easily
done when you can disable AGC, but the article further explains what's
happening in our radios in the presence of multiple strong signals.
Intermodulation is the product of two or more strong signals. If you
can reduce the strength of one or more of them, you may eliminate the
problem.

One of the most-effective ways to reduce the problem is to have as much
selectivity as possible before any amplifying stages. That's one reason
I persistently insist the antenna should resonate across the band. A
higher-inductance but non-resonant antenna may increase indicated signal
levels, but lead to IMD problems in areas where there are multiple
strong, nearby stations. They might work great where there aren't many
strong stations, but crash and burn in places where there are.

73,

Jim, KR1s
http://kr1s.kearman.com/ <http://kr1s.kearman.com/>

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