Re: A second "Stealth Modified" PL-380

Gary DeBock

Hello Stephen,
Thanks for your comments regarding the "Stealth Modified" PL-380 project. I've been pleasantly surprised at the success of this experiment, which provides a sizable boost in MW and LW sensitivity for almost no $$.
As for your questions, the local signal overload you are experiencing (in which splatter is extending 13 and 14 kHz away, even on the PL-380's 1 kHz DSP setting) is not related to loopstick antenna Q, and will not be solved by this modification. To reduce the splatter issue, you do have some options with external loop antennas (tunable and otherwise), phasing systems, etc, but if you wish to use the PL-380 as a stand-alone receiver in its original cabinet, you may need to be content with simple nulling.
Regarding the use of Amidon type 61 bars in the PL-380 (and PL-310) internal-cabinet loopstick modifications, like several other DXers I ordered some of these bars as possible substitutes for the stock bar. After starting the actual modification work, however, it was obvious that these large cylindrical bars were a deal breaker-- the Tecsun circuitry is simply too crammed to accommodate them without major "plastic surgery," and rewiring of some adjacent components. Having experienced such messy cutouts in the Eton E100 CFJ455K5 filter installations, I was highly motivated to avoid them again (as John and Guy can relate). In the absence of a type 61 ferrite bar of exactly the same shape and size, recycling the stock ferrite bar is the only logical option.
For those reluctant to attempt removal of their own PL-380 stock ferrite bar, there may be hope from another source. There have been multiple requests for PL-380 7.5" external loopstick modification jobs (far more than I can perform by myself), and the related article on MediaFire ( ) has already been downloaded 153 times. During these transplant operations the PL-380 stock ferrite bars become "orphans," suitable for recycling in a "Stealth Modified" PL-380 job. To meet the demand for the 7.5" loopstick PL-380's, other qualified technician(s) will be sought to perform this modification, and many more of these PL-380 "orphan" stock ferrite bars will probably be available before much longer.
Once some free time is available, I'll be happy to record some MP3's of the signal boost provided by the PL-380 "stealth modification," and post photos. For a $5 investment, the job certainly provides the maximum DXing bang for the buck.
73, Gary DeBock (in Puyallup, WA, USA)          
In a message dated 1/17/2010 5:21:17 A.M. Pacific Standard Time, pianoplayer88key@... writes:


I've been eagerly reading about these experiments with the loopstick antennas in the PL-380, and am glad to see some progress being made. :)
Question... does antenna Q (on the loopstick) affect the adjacent-channel selectivity (once you get past the bandwidth equivalent to whatever the filter setting is)? One reason I'm wondering is because my (stock, for now) PL-380 has several signals (stations within 5-8 miles of me) that even in the 1kHz setting, don't completely disappear until I'm tuned about 13 or 14 kHz off, and 10kHz away are strong enough to overpower stations that would otherwise be fairly well intelligible. Is there any way to improve on this?

Also, related to doing the stealth loopstick modification, is there any way to fit one of the Amidon Type 61 bars in there if I somehow cut (or ground) away some of the plastic near the flat loopstick (especially behind it) to make room? Or, would that possibly monkey with the shielding and make it more susceptible to internally-generated noise? If I am able to get rid of plastic (something I'd be willing to consider) to make room, what bar should I probably put in there? I'm thinking I would probably go with the Amidon R61-025-400 - the Type 61 0.25" diameter 4" bar.... or, if there's room after cutting away some plastic, should I go with the R61-050-600 and trim its length to fit in the cabinet?

I believe my PL-380 is one of the 11-2009 models. Pics:

I don't expect to start any modification until at least after I get the replacement tuner part from Joyce, which I ordered few days ago (not EMS, so it'll probably take a couple weeks or so to get it).

Another idea for an antenna modification.... what about winding an air-core loop antenna around the internal perimeter of the case, and somehow adding a switch to switch between that and the internal loopstick? (The internal air-core antenna would be intended to allow use of the radio in a vertical orientation.)

With whatever modifications I do, MW performance is the most important to me. Any improvement with LW would be considered an extra bonus. (In stock form, I don't get any trace of any LW stations, but then maybe I've checked at the wrong time of the day.)
I also have yet to log any TP/TAs, but that could also be due to the fact that I have strong locals on nearby channels... for example an IBOC on 600 (owning 594), 50kW locals on 690 (-693) and 760 (-747 & 774), a fairly nearby by 10kW on 1130 (wiping out 1134) directed toward me, and two 50kW 1580s battling it out both within about 300 miles of me (negating 1575), just to name a few challenges.

Also, speaking of the two 1580s... I don't have a recording of it now, but I often hear rapid volume changing (several times per second) or something when I hear both stations at the same time. Is that likely to be the two station's carriers not quite perfectly on frequency, or is it possibly soft mute? (Both stations are capable, when conditions are right, of coming in nearly as strong as a few of the aforementioned locals.) If that's not the case, considering that I still think there is a little bit of soft mute in my PL-380 (or is it just my extra-sensitive ear?), is there a recommended way to check for this?

And another thing ;) ... would it be possible to post audio examples of the shootouts, or modifications you have made? For example, record a station on the stock PL-380 that is at the threshold of detectability, then the same on a modded PL-380... or whatever comparison you might choose to do...?

--- In, D1028Gary@... wrote:
> Hi Steve,
> Great job on your "stealth modified" PL-380. I think we both agree that as
> long as a great LW sensitivity boost is obtained, we'll be happy to DX with
> the radio, even if the coil has a lower Q :-)
> The "stealth modified " PL-380 here really "smokes" the stock PL-310 on
> LW, and has a serious advantage on the lower MW frequencies as well (where
> many of the TP's reside). I have been extremely satisfied with this $5
> modification, which I think will help many DXers obtain a significant boost in
> AM-DXing capabilities for almost no $$.
> The same experiment was very successful in the PL-310 model, but to be
> perfectly honest, like most TP-DXers I have never been particularly thrilled
> with the "soft mute" function in the PL-310 and earlier models, which limits
> the ability to tune farther away from domestic splatter. Despite this, the
> same experiment in the PL-310 provided an equivalent boost in LW and AM
> sensitivity, and the PL-310 stock loopstick bar is significantly easier than
> the PL-380 bar to remove.
> Warning: the PL-380 stock loopstick typically will not come out without
> testing the patience of the tinkerer. I will paste the recommendations I gave
> to Steve below, and recommend that those lacking confidence about
> performing the procedure wait until the full modification article comes out.
> 73 and Good DX,
> Gary DeBock (in Puyallup, WA, USA)
> __________________________________________________________
> ____________
> Recommendations to Steve:
> Having done three of these PL-380 ferrite bar removals, I have noticed a
> great difference between the amount of glue in the models manufactured in
> November, and the models manufactured in December. The ones made in November
> are loaded with glue, making it almost impossible to remove the bar without
> cracking it into pieces, but the ones made in December seem to have far
> less glue. During a transplant procedure I myself cracked up a PL-380 bar on a
> model made in November, but successfully removed the bars in two December
> models.
> Anyway, the procedure is to use a small, flat jeweler's screwdriver to
> break all glue bonds on both sides, then gently pry underneath the bar to
> break the glue bonds on the bottom of the bar. Then the bar is gently lifted up
> by the screwdriver until it can be grasped by hand, and twisted repeatedly
> until it comes out. Almost all of the glue bonds are concentrated in one
> small section of the slot, but there are small spots of glue on each end.
> In a message dated 1/16/2010 6:53:47 P.M. Pacific Standard Time,
> steveratz@... writes:
> I did the same PL380 stock loopstick rewind today. I'd previously failed
> to remove the loopstick, and was close to breaking it when I stopped trying
> to pry it out. I tried again today, using a 1/4" wide screwdriver blade in
> the open end of the frame to pry, after once again scoring all the glue
> joints on the sides of the bar and frame. This time the glue eventually (very
> reluctantly) let go and I was able to get the loopstick out intact (and
> only one spot of mangled wire but not broken).
> I started rewinding (with 40/44 Litz) 0.1" from one end and wound 110
> turns before stopping. I had 0.25" left on the other end and could have
> probably gotten another 5 turns on. Total winding length 2.68", with 6" pigtails
> for connecting to the Q meter.
> The new coil measures worse for Q than the old one (!) on the HP4342A Q
> meter except for the bottom LF frequencies. Inductance measured 420 uH, Q 55
> at 796 kHz. (397 uH on the B&K 875A LCR meter; 390.7 uH on the LC
> meter)
> The highest frequency before the Q meter variable cap was at minimum was
> 1300 kHz, for Q measurements.
> 1300 kHz Q 17 (stock Q 30, 260 uH inductance at 796 kHz)
> 900 kHz Q 43 (stock Q 68)
> 700 kHz Q 72 (stock Q 102)
> 530 kHz Q 114 (stock Q 151)
> 500 kHz Q 125 (stock Q 162)
> 400 kHz Q 170 (stock Q 194)
> 300 kHz Q 225 (stock Q 220)
> 200 kHz Q 267 (stock Q 211)
> It was already dark by the time I'd finished the tests and put the coil in
> the PL380 and put the case on and tried the radio. But it could hear my
> 296 LGD beacon now; I had no comparison tests for MW especially for a
> non-daytime check, but it certainly heard stations from 1700 down.
> Perhaps Q really does have little effect on loopstick sensitivity. :)
> Since the new coil had much higher inductance compared to the stock coil, maybe
> that was the reason for improved LF sensitivity since I couldn't hear my
> local NDB with the stock coil.
> More mysteries! :)) That's the fun of experimenting, see what you come up
> with; with more data now added to what Gary, Roy and Scott have already
> contributed.
> 73,
> Steve
> ----- Original Message -----
> From: _D1028Gary@..._ (mailto:D1028Gary@...)
> To: _ultralightdx@ultralightdxult_ (
> Sent: Saturday, January 16, 2010 2:33 PM
> Subject: [ultralightdx] "Stealth Modified" PL-380 vs. Stock PL-310 Shootout
> Hello All,
> As reported in a recent Ultralightdx post, a Tecsun PL-380 model received
> a serious AM sensitivity boost by replacing the Chinese Litz wire on the
> stock ferrite bar with high-quality 40/44 Litz wire, and rewinding a coil to
> provide an inductance of 434 uh. This modification (detailed in the
> experimental report pasted below)provided an average 4 dBu increase in the
> PL-380's RSSI readings from 530-1700 kHz, and cost only about $5 (for the small
> quantity of 40/44 Litz wire).
> Yesterday this "stealth modified" PL-380 was tested extensively against a
> stock PL-310 model-- on all AM and LW frequencies. Tests were made for
> weak-signal reception throughout the spectrum, and records were kept both of
> relative signal quality, and the RSSI readings.
> These tests showed that the "stealth-modified" PL-380 had a performance
> advantage over the stock PL-310 on all LW and MW frequencies, although the
> advantage on the very high AM band (X band frequencies) was shown only on the
> RSSI readings, with equivalent live signal audio quality.
> On the LW frequencies, the "stealth modified" PL-380 really ran wild over
> the stock PL-310, receiving 4 beacon stations (at local midnight)
> completely inaudible on the PL-310. This was in sharp contrast to the stock PL-380's
> LW performance, which is much less impressive than the PL-310's (although
> not as deaf as the PL-300WT/ G8 models).
> On the lower AM frequencies, the "stealth modified" PL-380 also was
> clearly superior to the PL-310, having solid reception of the 521-INE beacon
> (that the PL-310 could barely detect as a trace). During early morning testing,
> the modified PL-380 was also able to detect traces of 594-JOAK and
> 747-JOIB, which were completely absent on the PL-310. RSSI readings on the
> modified PL-380 averaged 2 dBu higher than on the PL-310 on the low band
> frequencies, but the difference in actual signal quality was more pronounced.
> The modified PL-380 maintained this general advantage on the mid-band
> frequencies, although the PL-310 became more competitive. Live signal reception
> on open frequencies still favored the modified PL-380, although in several
> cases the PL-310's "soft mute" irritant kicked in, as if the model was
> throwing in the towel. The RSSI readings still averaged about 2 dBu in favor
> of the modified PL-380.
> AM high band reception was essentially equal, although the modified PL-380
> continued to show an average 1 dBu advantage in the RSSI readings. No
> difference in actual live signal audio was detectable in the two models, howe
> ver. The PL-310's "soft mute" function was again a serious impediment to the
> weak signal testing, making the model's audio drop out frequently during
> the competition.
> So what is the overall verdict of this "stealth-modified" PL-380 model?
> Well, simply by removing the stock loopstick and replacing the mystery
> Chinese Litz wire with superior 40/44 wire (in a longer 434 uh coil), at the cost
> of $5 a PL-380 owner can upgrade the AM and LW sensitivity of his radio to
> exceed that of the PL-310 model-- and avoid the "soft mute" issue as well.
> This advantage can be obtained without changing the outward appearance of
> the PL-380 in any way, and TSA will never know the difference :-)
> A full experimental report and related article should be drafted shortly
> (one of several unfinished hobby projects competing for rare free time,
> unfortunately)A
> 73, Gary DeBock (in Puyallup, WA, USA)
> ----------------------------------------------------------
> ----------------------------------------------------------
> Initial Experimental Report:
> Hello All,
> Yesterday there was a moderately successful experiment to wind a 40/44
> Litz wire coil on a PL-310 stock ferrite bar, which was successful in
> providing about a 4 dBu average increase in the RSSI readings from 530- 1700 kHz
> (as well as slightly better signal quality on weak stations, with the fringe
> benefit of stopping the PL-310 from kicking in to "soft mute" so quickly).
> But I should confess that the PL-310 experimentation yesterday was really
> only a warm up for my true pet project-- creating a similar in-cabinet
> loopstick for the PL-380, which hopefully would boost up its 530-1700 kHz
> sensitivity in the same way.
> As with the PL-310 yesterday, the PL-380's cabinet interior has very
> little free space, making it mandatory that the stock ferrite bar by recycled in
> a new loopstick (in the absence of a type 61 bar of the same shape and
> size, which seems unavailable)As with the PL-310 yesterday, the PL-3 ferrite
> bar can be successfully removed from its slot in the cabinet, although
> patience is required for this task, and the stock coil windings themselves always
> get mangled when the glue bonds are broken.
> As yesterday, the stock ferrite bar was first wound with the maximum
> amount of 40/44 Litz wire that its length would allow (providing about 512 uh),
> then coil turns were subtracted until the Si4734 chip varactor suddenly
> allowed a huge boost in signal reception on an extreme high band frequency (in
> this case, 1700 kHz). The inductance at this point was measured at 434 uh,
> which was somewhat higher than the "breakthrough" PL-310 inductance found
> yesterday (416 uh). The exciting result of the experiment was that this
> enhanced loopstick provided a clear increase in PL-380 AM sensitivity from
> 530-1700 kHz, both in the RSSI readings (averaging 4 dBu increase across the
> band) and in the signal quality of weak stations. The stock PL-380 clearly
> cannot compete with this "stealth modified" PL-380 model, which will be
> tested tomorrow against the stock PL-310.
> This modification costs almost nothing (about $5 of 40/44 Litz wire), and
> leaves the PL-380's outward appearance unchanged. Further testing will be
> conducted tomorrow against both the stock PL-310, and the "stealth modified"
> PL-310. Thanks also to Steve Ratzlaff for his excellent description of
> coil Q, and detailed readings on both the PL-310 and PL-380. Steve was my
> experimental partner in the creation of the SWP 7.5" Slider models, designing
> the CFJ455K5 filter modification for the C.Crane SWP ultralight (while I
> designed the Slider loopstick modification)T
> 73 and Good DX,
> Gary DeBock (in Puyallup, WA, USA)

Join { to automatically receive all group messages.