Tecsun PL-360 3" Loopstick Testing


Gary DeBock
 

Hello All,
 
A medium-sized replacement loopstick for the Tecsun PL-360 was wound on a 3" x 3/8" type 61 Amidon ferrite bar, using 40/44 Litx wire at an inductance of 315 uh (which practically maxed out the length of this shorter bar, making it impractical to add more turns). The loopstick was mounted with rubber shock mounts on a cut piece of plastic carpenter's level, with a Radio Shack 1/8" phone plug to match the stock loopstick jack.
 
Live signal testing of this new loopstick confirms that it boosts the AM sensitivity of the modest PL-360 well past that of either the stock PL-310 or PL-380 on all frequencies from 530-1600 kHz, with excellent nulling qualities. Even though this loopstick is much shorter than the 7.5" long model tested yesterday, it apparently is a huge improvement over any of the stock loopsticks used by Tecsun, and thereby outperforms all of them on the AM band.
 
The total cost of this loopstick upgrade is about $15 in parts, a real bargain considering the increase in AM-DXing capability.
 
73, Gary DeBock (in Puyallup, WA)
 
 
 
                                         


Gary DeBock
 

Hi Stephen,
 
Thanks for your comments on the PL-360 experimentation.
 
In answer to your questions, I do plan to post comparison RSSI and S/N readings between the stock and custom PL-360 plug-in loopsticks (3" and 7.5") in an upcoming PL-360 review. After the 3" x 3/8" ferrite bar plug-in loopstick was completed last night, I did run some quick comparison tests with the stock PL-310 and PL-380 models on some relatively open AM night frequencies here (521-INE beacon, 1610-TIS mix, and 1700-Tijuana) to verify that the PL-360's AM performance (with the 3" loopstick) was significantly better than the stock Tecsun models. I think that this 3" loopstick design would also have good potential in the PL-380's battery compartment as a "stealth" antenna, perhaps with an external plug-in battery supply to replace the 3 vdc power from the two missing batteries.
 
It's tough to predict how the custom Amidon loopsticks would perform in your RF-saturated environment, Stephen, since they have only been tested in the PL-360 (with its fixed 3 kHz DSP selectivity). The custom loopsticks can provide better RSSI and S/N readings on weak stations, but if you find that even the PL-380 (with its 1 kHz DSP option) is unsatisfactory in cutting down your local splatter, it's unlikely that these custom loopsticks will solve your problem. Your best option may be to use a sharp-nulling external tuned passive loop to cut down splatter (and add an additional tuned circuit to aid selectivity), or if you have some serious back yard space, you might try one of the directional single-loop designs like the EWE, flag, etc. If many of your pests are from a single direction, these antennas can help in cutting down the splatter.
 
73, Gary DeBock (in Puyallup, WA)         
 
In a message dated 4/14/2010 8:12:24 P.M. Pacific Daylight Time, pianoplayer88key@... writes:

 

Sounds good. Gary. Any chance you could post comparison dBu, S/N readings?
Now I'll ask a question about performance where it counts (for me, at least). So let's say you are in an RF-rich environment, where the RSSI is 50dBu on the "blank" channels across half the band. If you use one of the custom Amidon-61 loopsticks, would a signal with a RSSI, S/N reading of 15,01 be readable within 10-20kHz of the strong local, even if the stock stick would have a 50,00 RSSI,S/N reading 500kHz-1MHz away from the pest?
I'm not quite ready to write off my PL-380 as a US$69.99 loss, but I think I'm getting a little closer. :( I am in an area with strong signals, and was hoping to be able to pull in weak signals in the presence of strong ones. Unfortunately my PL-380 is not much better than my previous radio, a Panasonic RQ-SW20 (with a filter as wide as the SRF-M37W), in that respect. While the signal would be somewhat readable on the SW20 the few times I got lucky tuning in when the pest was off the air, the signal would be buried below the elevated noise floor on the PL-380, despite better sensitivity at the low and high band.
Also, my original reason for getting a different radio than what I had been using was I wanted better selectivity and sensitivity in a configuration that would fit in my front pants pocket (which is deeper than it is wide). Now I would also add resistance to blocking/desense, variable bandwidths, and robust construction (don't want plug-in loopsticks breaking off or tuning knobs breaking - the one in my PL-380 has broken twice) to my criteria. (Also the fact that the stock stick on the PL-380 doesn't take the entire cabinet width is a small concern.)

Maybe I should just wait for a PL-400 or something?

--- In ultralightdx@yahoogroups.com, D1028Gary@... wrote:
>
> Hello All,
>
> A medium-sized replacement loopstick for the Tecsun PL-360 was wound on a
> 3" x 3/8" type 61 Amidon ferrite bar, using 40/44 Litx wire at an inductance
> of 315 uh (which practically maxed out the length of this shorter bar,
> making it impractical to add more turns). The loopstick was mounted with
> rubber shock mounts on a cut piece of plastic carpenter's level, with a Radio
> Shack 1/8" phone plug to match the stock loopstick jack.
>
> Live signal testing of this new loopstick confirms that it boosts the AM
> sensitivity of the modest PL-360 well past that of either the stock PL-310 or
> PL-380 on all frequencies from 530-1600 kHz, with excellent nulling
> qualities. Even though this loopstick is much shorter than the 7.5" long model
> tested yesterday, it apparently is a huge improvement over any of the stock
> loopsticks used by Tecsun, and thereby outperforms all of them on the AM
> band.
>
> The total cost of this loopstick upgrade is about $15 in parts, a real
> bargain considering the increase in AM-DXing capability.
>
> 73, Gary DeBock (in Puyallup, WA)
>


pianoplayer88key
 

Sounds good. Gary. Any chance you could post comparison dBu, S/N readings?
Now I'll ask a question about performance where it counts (for me, at least). So let's say you are in an RF-rich environment, where the RSSI is 50dBu on the "blank" channels across half the band. If you use one of the custom Amidon-61 loopsticks, would a signal with a RSSI, S/N reading of 15,01 be readable within 10-20kHz of the strong local, even if the stock stick would have a 50,00 RSSI,S/N reading 500kHz-1MHz away from the pest?
I'm not quite ready to write off my PL-380 as a US$69.99 loss, but I think I'm getting a little closer. :( I am in an area with strong signals, and was hoping to be able to pull in weak signals in the presence of strong ones. Unfortunately my PL-380 is not much better than my previous radio, a Panasonic RQ-SW20 (with a filter as wide as the SRF-M37W), in that respect. While the signal would be somewhat readable on the SW20 the few times I got lucky tuning in when the pest was off the air, the signal would be buried below the elevated noise floor on the PL-380, despite better sensitivity at the low and high band.
Also, my original reason for getting a different radio than what I had been using was I wanted better selectivity and sensitivity in a configuration that would fit in my front pants pocket (which is deeper than it is wide). Now I would also add resistance to blocking/desense, variable bandwidths, and robust construction (don't want plug-in loopsticks breaking off or tuning knobs breaking - the one in my PL-380 has broken twice) to my criteria. (Also the fact that the stock stick on the PL-380 doesn't take the entire cabinet width is a small concern.)

Maybe I should just wait for a PL-400 or something?

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

Hello All,

A medium-sized replacement loopstick for the Tecsun PL-360 was wound on a
3" x 3/8" type 61 Amidon ferrite bar, using 40/44 Litx wire at an inductance
of 315 uh (which practically maxed out the length of this shorter bar,
making it impractical to add more turns). The loopstick was mounted with
rubber shock mounts on a cut piece of plastic carpenter's level, with a Radio
Shack 1/8" phone plug to match the stock loopstick jack.

Live signal testing of this new loopstick confirms that it boosts the AM
sensitivity of the modest PL-360 well past that of either the stock PL-310 or
PL-380 on all frequencies from 530-1600 kHz, with excellent nulling
qualities. Even though this loopstick is much shorter than the 7.5" long model
tested yesterday, it apparently is a huge improvement over any of the stock
loopsticks used by Tecsun, and thereby outperforms all of them on the AM
band.

The total cost of this loopstick upgrade is about $15 in parts, a real
bargain considering the increase in AM-DXing capability.

73, Gary DeBock (in Puyallup, WA)


sdwillingham
 

Stephen,

I'm wondering if maybe there is something else wrong with your PL-380 besides the broken tuning knob. I really can't think of a reason why you are seeing 50 dBu in between channels. The PL-380 might de-sense in the presence of strong channels, but it shouldn't overload or distort, which is what could "fill-in" the gaps between channels. What are the RSSI readings on a few of your strongest stations?

Maybe you could demo a G8 at a local Radio Shack to see if you get similar behavior?

In any case, as long as you see a 50 dBu floor, an antenna with more signal strength will not be helpful. You need either better Q or better nulling.

-Scott-


gratiscomputer <gratiscomputer@...>
 

D1028Gary@... wrote:
Hi Stephen,
Thanks for your comments on the PL-360 experimentation.
In answer to your questions, I do plan to post comparison RSSI and S/N readings between the stock and custom PL-360 plug-in loopsticks (3" and 7.5") in an upcoming PL-360 review. After the 3" x 3/8" ferrite bar plug-in loopstick was completed last night, I did run some quick comparison tests with the stock PL-310 and PL-380 models on some relatively open AM night frequencies here (521-INE beacon, 1610-TIS mix, and 1700-Tijuana) to verify that the PL-360's AM performance (with the 3" loopstick) was significantly better than the stock Tecsun models. I think that this 3" loopstick design would also have good potential in the PL-380's battery compartment as a "stealth" antenna,
Maybe you have room to construct a twin coil in the batt compartment??

What would the construction of a twin coil look like??

http://www.ccrane.com/antennas/am-antennas/twin-coil-ferrite-am-antenna.aspx

Marc

--
What's on Shortwave guide: choose an hour, go!
http://shortwave.tk
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pianoplayer88key
 

Well... right here just barefoot I am far enough away so that I'm not quite getting 50 dBu in between channels, but it is often touching 40 - 45 dBu. I don't have to boost it much to get 50 dBu, though - just using the SAT is sufficient for that. (By comparison, inside a car, which naturally attenuates signals somewhat, the barefoot reading in between channels is around 15 - 20 dBu.)

I took the liberty to do some comparison on several local frequencies an hour or two ago. Comparisons are: inside the car (barefoot) | outside (barefoot) | outside (with Select-A-Tenna). (Then there'll be one more noted farther down the post.) All were done between 10:15pm and 11:45pm using relatively stable local signals using 1 kHz bandwidth.

600 (KOGO): 47,25 | 63,25
690 (XEWW): 37,25 | 56,25
747 (off KFMB): 24,00 | 37,00
760 (KFMB): 58,25 | 63,25
774 (off KFMB): 19,00 | 39,00
800 (XESPN): 31,25 | 47,25
860 (XEMO): 33,25 | 51,25
895 (off KECR): 15,00 | 35,00
910 (KECR): 49,25 | 63,25
925 (off KECR): 15,00 | 35,00
1040 (KURS): 23,22 | 40,25
1116 (off KSDO): 22,00 | 37,00
1130 (KSDO): 50,25 | 63,25
1143 (off KSDO): 22,00 | 37,00
1170 (KCBQ): 44,25 | 60,25
1210 (KPRZ): 30,25 | 45,25
1240 (KNSN): 36,25 | 52,25
1270 (XEAZ): 27,25 | 43,23
1310 (XEC): 26,19 | 42,25
1360 (KLSD): 40,25 | 57,25
1420 (XEXX): 29,25 | 47,25
1470 (XERCN): 35,25 | 54,25
1550 (XEBG): 15,14 | 32-35,25
1630 (XEUT): 24,25 | 40,25
1700 (XEPE): 33,25 | 50,25

Then, I took the strongest one, 760 (KFMB), and gave the radio a bit of an extra boost to see what would happen. First, I used just the SAT tuned to 760, while tuning the PL-380 (using the push buttons as the tuning dial is broken). With only the SAT, I was getting 50 dBu in between channels from about 665 to 1015 kHz, and 49 dBu from about 545 to 1495 kHz. Also, the 2nd harmonic (1520) was reading 47,25 with just the SAT.

Then I put it to the ultimate (well, for what I had access to) test. I put the SAT and PL-380 up against a power pole - one of the ones with a ground wire running down it inside the narrow diameter cylindrical wood piece running up the height of the pole.
Now to give you a little idea of how much of a boost that is... back several years ago KCBQ, a local blowtorch pest, used to have their transmitter site a few miles closer, AND had a higher ERP toward me. When taking my previous radio (Panasonic RQ-SW20) barefoot on the road on which their transmitter property was (about 5 to 6 miles north of me), sure 1170 would splatter across a good portion of the band.
However... use the SAT and power pole outside my house several miles away from the transmitter.... and I could actually get the audio, while tuned ON the assigned frequency, to overdrive, something I couldn't do barefoot on the road right by their transmitter!

So... I did the SAT + Power Pole test on 760... and here's the results:
50dBu spread: 153kHz to almost 3000 kHz (yes, I checked the LW and SW bands)
harmonics: 2nd was 63dBu, 25dB S/N, 3rd couldn't be tuned (2280), 4th to 8th were 63dBu (but not 25dB S/N), 9th was about 57-60, 10th (7600 kHz) was about 62 dBu or so, and I didn't check any higher than that.


Now... for some RSSI readings I took a couple days ago in the early afternoon (2:00 to 3:45 pm) in my back yard. Most of them are barefoot, and I'll note SAT readings on some channels.

520 - 20,00
530 - 17,01-11 NW - WNHV296 (LAX) + another TIS (CalTrans) | SAT = 20-30,07-19
540 - 50,25 SSW - XESURF (null (N) = 27,18) | SAT = 63,25
550 - 24,00 north/south (N/S) , 20,00 east/west (E/W)
560 - 22,00 E - KBLU | SAT = 22-24,06-12
570 - 31,24 NW - KLAC (n=20,07) | SAT = 51,25
580 - 22,00
590 - 40,00 W - KOGO's IBOC (n=20,01 - KTIE?) | SAT = 30,02 NNW = KTIE if nulling KOGO's IBOC
600 - 63,25 W - KOGO (n=44,25)
610 - 41,00 W - KOGO (n=22,00) | SAT = 30,02-07 NNW = KAVL, if nulling KOGO's IBOC
620 - 40,25 S - XESS (n=30,25) | SAT = 61,25
630 - 25,00 NW - KFI's IBOC | SAT = 38,00
640 - 45,25 NW - KFI (n=27,19) | SAT = 63,25
650 - 25,00 NW - KFI's IBOC | SAT = 34,00
660 - 25,00 | SAT = 27,03-12 - XESURF spur
670 - 25,19-22 WNW - KIRN (n=25,11) | SAT = 43,25
680 - 29,00 N/S , 24,00 E/W (have in the past been able to log KNBR early afternoon but not that time)
690 - 63,25 SSW - XEWW (n=46,25)
700 - 29,00 N/S , 27,00 E/W (I think I've heard KALL faintly a couple times early afternoon, but not that day)
710 - 27,17 NW - KSPN (n=27,09) | SAT = 47,25
720 - 30,00 N/S , 27,00 E/W | SAT = 35,00 NE - KDWN
730 - 30,00 SSW - XEEBC (WNW = 29,00 - KBRT's IBOC) | SAT = 35,16 for XEEBC
740 - 48,25 WNW - KBRT (n=33,25) | SAT = 63,25
750 - 30,00
760 - 63,25 NW - KFMB (n=49,25)
770 - 29,00
780 - 32,00 N/S , 27,00 E/W
790 - 29,21-25 WNW - KABC (n=27,00) | SAT = 46-48,19-25 for KABC, with XESU possibly in the background
800 - 54,25 SSW - XESPN (n=27,12-17) | SAT = 63,25
810 - 25,00 (I may have been able to hear KGO a couple times early afternoon with SAT, but not the other day)
820 - 27,00 ESE - XEVMS (or XEABCA, not sure of call - radio-locator names 2 for same COL) | SAT = 32,21-25
830 - 31,25 N - KLAA (n=24,08) | SAT = 52,25
840 - 24,00 | SAT = 32,07 NE - KXNT
850 - 22,00 ESE - XEZF | SAT = 33,25
860 - 54,25 SSW - XEMO (n=29,25) | SAT = 63,25
870 - 22,07 NNW - KRLA | SAT = 35,25
880 - 25,00 N/S , 22,00 E/W
890 - 25,00 | SAT = 35,23-25 WSW - Point Loma TIS (KPB892) carrier, I think - no audio though
900 - 34,00 N/S , 24,00 E/W
910 - 63,25 NNE - KECR (n=44,25)
920 - 27,00 N/S , 22,00 E/W
930 - 23,23 NW - KHJ (n=25,16) | SAT = 44,25
940 - 22,00 ESE - XEWV | SAT = 30,23
950 - 51,25 SSW - (XEKAM? - Rosarito) (n=31,24) | SAT = 63,25
960 - 25,00 NNE - KIXW | SAT = 35,00-08
970 - 30-32,00 NE - KNWZ | SAT = 34,24
980 - 32,00 NW - KFWB | SAT = 40,25
990 - 22,12-18 - WNW = KTMS , ESE = XECL | SAT = 33,16-25 for both, I think
1000 - 40,25 NNW - KCEO (n=25,05) | SAT = 62,25
1010 - 30,00 N/S , 24,00 E/W | SAT = 30,09-16 NE - KXPS
1020 - 25,07-10 NW - KTNQ | SAT = 41,25
1030 - 43,25 SSW - XESDD (n=25,20) | SAT = 59,25
1040 - 49,25 WSW - KURS (n=31,25) | SAT = 63,25
1050 - 27,02 ESE - XED | SAT = 41-42,15-25
1060 - 35,00 NW - KNX's IBOC | SAT = 39,00
1070 - 43,25 NW - KNX (n=35,24) | SAT = 63,25
1080 - 34,00 NW - KNX's IBOC (n=39,00) | SAT = 39,00
1090 - 49,25 SSW - XEPRS (n=33,22) | SAT = 63,25
1100 - 35,00 N/S , 29,00 E/W
1110 - 34,00 NW - KDIS (n=37,00) | SAT = 42,25
1120 - 43,00 N/S , 30,00 E/W
1130 - 63,25 N - KSDO (n=47,25)
1140 - 39-55,00 N/S , 32,00 E/W
1150 - 39,00 N/S , 32,00 E/W | SAT = 47,00 - I think I could barely hear KTLK under the elevated floor courtesy KCBQ)
1160 - 39,00 N/S , 32,00 E/W
1170 - 63,25 NNE - KCBQ (n=54,25)
1180 - 39,00 N/S , 30,00 E/W
1190 - 41,00 NNW - KXMX | SAT = 45,02-07
1200 - 41,00 N/S , 30,00 E/W
1210 - 53,25 NNW - KPRZ (n=34,05) | SAT = 63,25
1220 - 41,00 N/S , 30,00 E/W
1230 - 32,00 E - KXO | SAT = 37,09-16
1240 - 54,25 WSW - KNSN (n=32,22) | SAT = 63,25
1250 - 32,00 WNW - KZER (I think, or possibly KNWH?) | SAT = 39,25
1260 - 32,00 N/S , 29,00 E/W | SAT = 35,01-05 NW - KSUR
1270 - 46,25 SSW - XEAZ (n=27,14-17) | SAT = 63,25
1280 - 30,18 NW - KFRN (n=30,00) | SAT = 46,25
1290 - 25,00 WNW - KZSB (n=30,00) | SAT = 31-36,25 WNW - KZSB ; 34-37,10-15 NNE - KKDD
1300 - 34,00 N/S , 30,00 E/W | SAT = 29,04-20 NW - KAZN (normally KROP would be dominant but they are silent)
1310 - 43,25 SSW - XEC (n=27,07-16) | SAT = 63,25
1320 - 30,00 NW - KKSM | SAT = 36-37,23-25
1330 - 30,00 NW - KWKW | SAT = 35,25
1340 - 30,00 WNW - KCLU | SAT = 35,16-25
1350 - 30,00 | SAT = 35,13-17 N - KTDD
1360 - 63,25 WSW - KLSD (n=30,21-25)
1370 - 32,00 N/S , 30,00 E/W | SAT = 35,07-12 NNW - KWRM
1380 - 30,00 N/S , 32,00 E/W
1390 - 39,25 SE - XEKT (n=29,00-03) | SAT = 61,25
1400 - 30,00 N/S , 27,00 E/W | SAT = 34,07-10 - spanish (no idea what station it would be though)
1410 - 27,00 | SAT = 35,00 N - KCAL? (too weak to tell for sure though)
1420 - 47,25 S - XEXX (n=25,00) | SAT = 63,25
1430 - 25,00 E - KWST | SAT = 30,08-18 E (KWST) , NW = KMRB
1440 - 25,00 N/S , 24,00 E/W | SAT = 35,00 NNE - KDIF
1450 - 30,25 NNW - KFSD (n=24,02) | SAT = 47,25
1460 - 30,00 N/S , 22,00 E/W | SAT = 28-31,19-25 - spanish (no idea what station though)
1470 - 52,25 SSW - XERCN (n=22-24,19-22) | SAT = 63,25
1480 - 22,00
1490 - 22,01-06 - ESE = KGBA , WNW = KIST | SAT = 29-36,13-25 for both
1500 - 22,00 | SAT = 26-27, 21-23 W - Qualcomm Stadium TIS Carrier, I think
1510 - 29,00 N - KSPA | SAT = 27-30,19-23
1520 - 22,00 WNW - KVTA | SAT = 31,25
1530 - 22,00 N/S , 20,00 E/W (occasionally KFBK is possible in the daytime during winter but I haven't heard them this week)
1540 - 20,12 - something - not sure if it was a het or KMPC, but it was too weak to hear audio | SAT - 24,09 NW - KMPC
1550 - 29,25 SSW - XEBG (n=20,00) | SAT = 51,25
1560 - 24,00 NNW - KNZR | SAT = 25,11-17
1570 - 27,00 N/S , 20,00 E/W | SAT = 29,00 N - KPRO (very faint)
1580 - 20,05-10 NW - KBLA | SAT = 36,25 NW - KBLA (sometimes KMIK can also be heard on winter days)
1590 - 19,00 | SAT = 25,13-18 NW - KUNX
1600 - 20,00 N - KAHZ | SAT = 29,22-25
1610 - 29,00 N/S , 17,00 E/W | SAT = 22,01-02 - unidentified TIS
1620 - 24,14-17 - WNSB415 San Ysidro (n=17,00) | SAT = 41,25
1630 - 48,25 SSW - XEUT (n=23,24) | SAT = 63,25
1640 - 20,00
1650 - 19,00 NW - KFOX | SAT = 32,17-25
1660 - 25,00 N/S , 17,00 E/W | SAT = 22,00-02 W - San Diego Convention Center TIS? (but too weak to ID)
1670 - 17,01 NNE - KHPY | SAT = 38-40,25 (but with some fading)
1680 - 25,00 N/S , 17,00 E/W
1690 - 27,00 N/S , 17,00 E/W (San Diego Airport TIS used to be possible (barely) with SAT before XEPE was on the air)
1700 - 48,25 SSW - XEPE (n=15,13-17) | SAT = 63,25
1710 - 25,00 N/S , 15,00 E/W

Well... turns out I listed more than just a few of my strongest stations. ;) As for demoing a G8, I actually had bought one before I bought the PL-380, and tested it... but right now I'm not sure I can find any notes I had made - I think I may have deleted them or something accidentally.

I think what I need is better Q AND better sensitivity. Originally, I was planning to use the radio inside my pants pocket (which is deeper than it is wide, hence the desire for a vertically-oriented radio), with headphones connected, while I was going around town either walking, taking the bus, on my bike (during which I'd only have the headphones on loosely), etc. A few stations I wanted to be able to listen to mid daytime were 560 KBLU Yuma (pest is 570 KLAC), 590 KTIE San Bernardino and 610 KAVL Lancaster (pest for both is now 600 KOGO's IBOC), 680 KNBR San Francisco (pest is 690 XEWW), 700 KWLW North Salt Lake City (pest is also 690 XEWW), 1110 KDIS Pasadena (pest is 1130 KSDO), 1180 KERN Wasco-Greenacres, which is near Bakersfield, CA (pest is 1170 KCBQ), 1580 KMIK Tempe, near Phoenix, AZ (pest is co-channel KBLA Santa Monica), among others. All of them were virtually completely undetectable - not even so much as a carrier (with the exception of KDIS, but ONLY if KSDO was off the air) on my previous barefoot radio, the Panasonic RQ-SW20, which I still have.

Also, with a good loop antenna (something comparable to or better than what Bruce Carter has used - he was able to get Chicago AMs from TX in the daytime), I was hoping to get daytime loggings of 750 KXL (pest is 760 KFMB), 820 WBAP (pest would be 820 XEVMS Mexicali), 850 KOA, 1000 KOMO (pest would be 1000 KCEO Vista), 1080 KRLD (pests would be 1070 KNX (and their IBOC) and 1090 XEPRS), 1160 KSL (pest would be 1170 KCBQ), 1190 KEX (pest would be KXMX Anaheim), just to name a few... and at night with a good loop I would like to be able to regularly bring in 650 KENI Anchorage, AK and WSM Nashville, TN (pest would be KFI), 660 WFAN New York (pest would be KTNN Window Rock, AZ), bring back 670 KBOI Boise (they changed their pattern - used to be a regular here before that, pest is now KIRN Simi Valley) and WSCR Chicago, 700 WLW Cincinnatti, 720 WGN Chicago (have logged them once, pest is usually KDWN Las Vegas), 750 KFQD Anchorage and WSB Atlanta, 760 WJR Detroit (pest is local KFMB), 770 WABC New York, 880 WCBS New York (pest is KRVN Lexington, NE), 1000 WMVP Chicago, 1500 (former WTOP) Washington, DC (I have heard KSTP St Paul once or twice), just to name a few.


Scott, what part of the country do you hail from? (I think Gary DeBock is in the Seattle area or somewhere south of there, but I'm not sure.) I'm basically about 10 or so miles east of San Diego, CA - basically south of El Cajon and east of La Mesa, within a mile or so of 32°45'40"N 116°56'50"W, which is on a school campus not very far from me. (Also I'm curious as to what typical daytime RSSI readings of stations (and in between) are where you are - I understand you got a PL-380, right? or was it a PL-310, PL-360, or PL-300WT/G8?)


Now, a quick reply to Gary's post, as I don't want to make two separate posts....

Any chance you could do daytime comparisons when the signals are more stable? Also, any chance that you could go to somewhere within a km or two of some of your 50kW locals and check the performance there? I'm about 6-10 miles away from a couple locals, and the RSSI readings when between channels are unacceptable at around 30-40 dBu. Inside a car in a rural area (where weaker signals would be attenuated on top of that), they read 15 dBu in between channels.
As for backyard space, I probably have about 40 feet (north-south) by 120 feet (east-west) or so of area where I could erect temporary antennas. Also I'm probably about 5 miles away from a commuter airport, and not exactly in the flight path of the international airport 15 miles to the west, so I do have a little bit of room to elevate an antenna. (I would be a bit wary of erecting a full-wavelength guyed tower for 153 kHz, though.)

--- In ultralightdx@..., "sdwillingham" <sdwillingham@...> wrote:

Stephen,

I'm wondering if maybe there is something else wrong with your PL-380 besides the broken tuning knob. I really can't think of a reason why you are seeing 50 dBu in between channels. The PL-380 might de-sense in the presence of strong channels, but it shouldn't overload or distort, which is what could "fill-in" the gaps between channels. What are the RSSI readings on a few of your strongest stations?

Maybe you could demo a G8 at a local Radio Shack to see if you get similar behavior?

In any case, as long as you see a 50 dBu floor, an antenna with more signal strength will not be helpful. You need either better Q or better nulling.

-Scott-


Gary DeBock
 

Hi Stephen,
 
All of the AM signal comparisons in the Shootout and Review articles are performed under daytime DX conditions, so that stable ground wave signals are used to judge relative sensitivity and selectivity between ULR models. Trying to compare unstable AM signals at night would be asking for trouble.
 
Fortunately here in Puyallup, WA there are no 50 kw locals, but we do have a Korean-language graveyard pest (1450-KSUH) about 2 miles from here, a 50 kw Tacoma slopper (KKOL-1300) about 6 miles away, and a 5 kw Spanish-language pest (1360-KKMO) about 8 miles away. But none of these really cause the PL-380 (on its 1 kHz DSP setting) to overload here, Stephen. At night, stations can easily be heard 10 kHz up and down from each of these stations-- so I'd agree with Scott that you probably have an issue with your individual PL-380.
 
All of the Si4734 DSP models typically have fairly good resistance to overload, in comparison to the earlier-design ULR's that preceded them. Most traditional Ultralights overload badly when inductively coupled to the 9' box loop here, but the Si4734 models are highly "crunch-resistant," and behave very well (even with the RF onslaught). 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.
 
73, Gary DeBock (in Puyallup, WA)   
 
          
 
In a message dated 4/15/2010 1:38:43 A.M. Pacific Daylight Time, pianoplayer88key@... writes:


Now, a quick reply to Gary's post, as I don't want to make two separate posts....

Any chance you could do daytime comparisons when the signals are more stable? Also, any chance that you could go to somewhere within a km or two of some of your 50kW locals and check the performance there? I'm about 6-10 miles away from a couple locals, and the RSSI readings when between channels are unacceptable at around 30-40 dBu. Inside a car in a rural area (where weaker signals would be attenuated on top of that), they read 15 dBu in between channels.
As for backyard space, I probably have about 40 feet (north-south) by 120 feet (east-west) or so of area where I could erect temporary antennas. Also I'm probably about 5 miles away from a commuter airport, and not exactly in the flight path of the international airport 15 miles to the west, so I do have a little bit of room to elevate an antenna. (I would be a bit wary of erecting a full-wavelength guyed tower for 153 kHz, though.)


jim_kr1s <jkearman@...>
 


--- 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 . 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  simply explains the causes.

This PDF  explains how ARRL  measures intermodulation distortion (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/