Tecsun PL390

[rfry]

There are often occasions when I'll want to hear...a station from twice as far as Radio-Locator's "fringe" 0.15mV/m contour during the day, while within a mile (or often within a couple hundred feet) of a first-adjacent (or 2nd-adjacent IBOC - would be 1st adjacent if IBOC was off) strong local.

First-adjacent interference issues aside, very few listening locations have an ambient r-f noise level that will permit useful reception of an AM broadcast station when the arriving field is even 0.15 mV/m, let alone less.

 

[nd2023]

It's better if a DSP radio handles overload by desensitizing rather than splattering images across the band.

 

[BobOnTheJob]

I haven't gone too close to an FM tower with a DSP radio yet, but I had noticed the significant amount of desensitivity with Pioneer car radios with the Supertuner IIID when I drive past FM towers that are located just along the road.

My Supertuner IIID does exactly the same thing.

 

[BobOnTheJob]

It's better if a DSP radio handles overload by desensitizing rather than splattering images across the band.

Agreed....

 

[pianoplayer88key]

It's better if a DSP radio handles overload by desensitizing rather than splattering images across the band.

Agreed....

Actually I was able to get my PL-606 to splatter images all over the band earlier this evening.  I took it and my Select-A-Tenna outside to a utility groundwire, tuned the SAT to 760 (KFMB is 7.3 miles away and 50kW at night) and recorded the bandscan linked.  (It's about 2.5 MB at 32 kbps mono, mp3.  I stayed on each frequency for a few seconds or so - generally staying a bit longer when there were strong images, and moving on quicker when there wasn't much.)
A few notes:  KFMB's TOH is heard while tuned to 540, KFMB and KECR are heard mixing on 610 (I know KEAR is also on that frequency but they're hard to get here - also KECR has images on a few other frequencies), there's a strong KFMB image on 700, 760's signal readings were 98dBuV/25dB SNR (with unintelligible audio and virtually no background noise), and KFMB's 2nd harmonic, 1520, was indicating about 78 dBuV.  Pretty much everywhere on the band where there wasn't a strong signal or a strong image (although weak images or splash could be heard), the PL-606 was reading 50/00, which is what it does when it's being badly desensed.


I was noticing something that seems quite odd.  I actually got BETTER reception of 1110 KDIS by going FARTHER away from them, in approximately the same direction.
Here's 1110 KDIS at Cameron Corners - about 135 miles, 139° from their transmitter, recorded around noon on the 21st.
For comparison, this is my futile attempt at hearing KDIS at Santee Town Center Trolley - only 106 miles, 146° from them, recorded around 5:30pm on the 21st.  (I was outside on the other side of a bagel shop (which was closed at the time) maybe about 20-30 feet from the trolley line, so I wasn't getting any QRM when there was no trolley in the station.)
Signal readings on the PL-606 were 15,10 at Cameron Corners and 50,00 at Santee.  (It's interesting that it would have showed a stronger signal when KDIS wasn't audible - seems to prove that the dBu display isn't really all that accurate or even linear.)
I would think that the signal should be better when I'm closer to them, but in this case apparently not.

I noticed that the Sony SRF-59 had an easier time at Santee receiving a couple stations than the PL-606.  For example, here's 1070 KNX on the PL-606 and
on the SRF-59.  (BTW I was unable to get 1110 KDIS in Santee on the SRF-59 - there was too much splash from 1130 KSDO, which was indicating about 88,25
or so on the PL-606.)
My location at Santee was about 106 miles, 131° from KNX.  On the PL-606, I got what I thought was better reception of KNX at Cameron Corners, about 138 miles, 128° from KNX - yet another case of going farther away to improve reception!

There are often occasions when I'll want to hear...a station from twice as far as Radio-Locator's "fringe" 0.15mV/m contour during the day, while within a mile (or often within a couple hundred feet) of a first-adjacent (or 2nd-adjacent IBOC - would be 1st adjacent if IBOC was off) strong local.

First-adjacent interference issues aside, very few listening locations have an ambient r-f noise level that will permit useful reception of an AM broadcast station when the arriving field is even 0.15 mV/m, let alone less.

When I was in Cameron Corners, I was able to get what I'd call useful reception on 1090 XEPRS, even though I'm about 3x or so past their 0.5mV/m contour.  (I should mention that they use their nighttime directional antenna in the daytime, too.  The FCC and Radio-Locator both say XEPRS is non-directional in the daytime, but they're not.)  Here's XEPRS's night pattern on R-L.  I was approximately 2.8 miles north of the border and about 2/3 of the way from the coast to the county line - approximately between the "s" and "t" (about level with its cross) in "Chula Vista".
Several months ago at home when 1170 KCBQ (I'm about 9.3 miles and 187° from them) was off the air for several minutes shortly after 1pm, I was able to get 1180 KERN using the Select-A-Tenna.  There signal was also present barefoot, but it was much tougher to hear.  (1130 KSDO was still on the air desensing the radio somewhat - I suspect it would have been easier to hear KERN if KSDO was also off.  Also toward the end you'll suddenly hear KERN's signal take a nose dive as if another unmodulated carrier is coming on over the top of them.  That's KCBQ coming back on and desensing the radio.)  I estimate that I'm about 2x past KERN's estimated 0.15mV/m signal.
Even with all the locals operating normally (including a 20kW on 950 that's about 25 miles away), I'm able to get a faint, but audible signal from 960 KIXW on the PL-380 (If I've made a recording on the PL-606 (which is supposed to be a little more sensitive), I can't find it at the moment.)


So, it IS possible in my area to hear signals well past their 0.15 mV/m "fringe" contour.  It'd be nice if my PL-606 didn't desense so badly, though.  IIRC the signal reading for 960 KIXW was about 30/00 which indicates moderate desense.  I think 49/00 and 50/00 indicate severe desense (my DSP radios usually show about 45/00 or so in the mid 1100s during the day in my back yard), and if it's possible to get a 15/25 signal indication, then there's virtually no desense.  Using the SAT tuned to 1170, on both DSP radios I can often get 15/25 on KCBQ's 2nd harmonic on 2340 kHz.  I haven't had much of a chance to experiment much with a small signal generator to simulate desense, but I suspect that if I was to desense the PL-606 to indicate 30/00, then KCBQ's harmonic would be about as listenable as my clip of KIXW on the PL-380.  If it was 50/00, I would think the signal on 2340 kHz would disappear completely.  (I did experiment in the MW band several months ago with a local signal about 72/25 or so.  With the generated signal on (and set up to indicate 98/25 on its frequency), the local signal went from clear reception to 50/00 and barely detectable.)
As for sensitivity, I'd prefer co-channel interference about like this, rather than no signal at all, when I'm at a theoretical area where 5 same power/antenna/frequency stations are arranged in a circle around me such that one station's 0.005mV/m contour doesn't overlap another station's 0.1mV/m contour.  (BTW anyone know where in the FCC rules it mentions Class A stations being protected to their 0.1mV/m groundwave contour on co-channel, and a 26dB desired-to-undesired ratio being desired?)  I might want an RF gain control, though, so if one co-channel was stronger than the others, I could reduce the strength of the weaker one and make it go away.  (BTW in the recording there's only 2 co-channels - XEKT and KLTX, both on 1390, recorded mid-afternoon in April near Fashion Valley mall in San Diego, CA.)


Since this topic is on the PL-390 ...  I wonder if I should think about buying one?  I know I won't be able to carry it around clipped on my belt or in my pocket like I can the SRF-59 (which is how I would prefer to carry a radio that does get the stations I want to get at midday (without splatter/desense - RF noise is OK and at their weak levels I would expect some of that) including but not limited to KFYI, KNBR, KALL, KDWN, KCBC, KGO, KXNT, KRLA, KIXW, KNWZ, KFWB, KDUS, KFNX, KDIS, KNWQ, KTLK, KERN, KMZT, KZSB, KROP, KCLU, KTDD, KFNY, KSPA, KVTA, KNZR, most of which I think would be receivable if my radios weren't desensed or splattered), but would it bring in the weak stations that on the PL-380 and PL-606 are desensed/splattered into oblivion?
How would the PL-390 handle the situations I've outlined?  Based on what I've been reading, it looks like it would be struggling at places like here (that's 590 KTIE) and here (that's 910 KECR and 1170 KCBQ).  Hopefully it'd have a little easier time here (near 760 KFMB), at least compared to the previous two examples.   BTW it's interesting to note that KFMB, using the SAT & utility groundwire from 7.3 miles away, is actually STRONGER than just with the built-in ferrite a couple hundred feet from their antenna, and was approximately comparable with reception of KTIE and its harmonics when I was near them as seen in the photo.  (I was outside the fence, btw.)  I'm curious - would even a very good radio like a Drake, Hammarlund, etc (substitute any of your favorites), be able to handle the overload implied in the photo near KCBQ, or would that bring even those big boys to their knees?  (That's a HARMONIC of KCBQ I was receiving - in the FM band!)

 

[MarioMania]

Does the DX-380 have the DSP chip in it??

 

[dxer720]

No, MarioManai, the Radio Shack DX-380/Sangean ATS-808 does not have DSP. They're too old.

If you're asking about the Tecsun PL-380...That does have a DSP chip.

The performance of the Tecsun PL-380 is pretty good, but not as good as the PL-390...Particularly, the MW/AM & LW bands are not as strong. This is probably due to the smaller internal ferrite loopstick used for MW/LW.

 

[MarioMania]

Thanks...

So the DSP chip will improve reception??