Question about ultralight and loops for MW


sarmento2k
 

Hi

After have seen info about these new DSP receivers (like PL310/380) :

http://bbs.tecsun.com.cn/0002.asp?open=186695

I wonder if it would support loop antennas, like square air coil or even ferrite loops.

If one issue to add : living near big power MW stations.

Have anyone tried MW dx in this conditions ?

Regards
Sarmento - Rio de Janeiro - Brazil


Gary DeBock
 

Hello Sarmento,
 
Many air core and ferrite core external loops give excellent performance with the Tecsun PL-380 and PL-310 models, and make DXing a lot more fun.
 
Depending upon your DXing preferences, you can choose a transplanted ferrite loop (like the 7.5" loopstick PL-380), an inductively coupled ferrite loop (like the Q-stick) or a direct or inductively-coupled air core loop. All of these antenna designs have performance tradeoffs, and no one design is perfect for every situation.
 
Most DXers who wish to avoid "surgery" on the radio use air or ferrite core loops with the inductive coupling system, which gives an excellent performance boost (depending on the size of the loop) with an extra tuned circuit to aid in selectivity. The directly-connected ferrite and air core loops always require modification to the radio (and possibly the addition of other external hard-wired components), but avoid the need for a separate tuning step. 
 
My own favorite for convenient DXpedition usage is the 3' portable PVC air core loop, which is described in the photo article at  http://www.mediafire.com/?hqyzzu1mvyt . This tuned passive loop provides a powerful inductive coupling boost for the barefoot PL-380, can be assembled in 2 minutes, and will fit inside a packed compact car trunk.
 
73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)
 
 
 
In a message dated 7/6/2010 4:12:29 A.M. Pacific Daylight Time, sarmento.campos@... writes:

 

Hi

After have seen info about these new DSP receivers (like PL310/380) :

http://bbs.tecsun.com.cn/0002.asp?open=186695

I wonder if it would support loop antennas, like square air coil or even ferrite loops.

If one issue to add : living near big power MW stations.

Have anyone tried MW dx in this conditions ?

Regards
Sarmento - Rio de Janeiro - Brazil


sdwillingham
 

Sarmento,

A transformer-coupled air-loop is very effective. See:

http://kr1s.kearman.com/html/hooploop.html

Note that the transformer design will work with all kinds of
loops which have inductance in the 10 to 20 uH range. Results
with 12 inch or even 6 inch loops can be impressive and a
little more portable. You may also use ferrite loopsticks
wound for low inductance. The balanced design and relocation
of the antenna outside the radio cabinet both contribute to
superior noise immunity and nulling capabilities.

-Scott-

--- In ultralightdx@..., "Sarmento" <sarmento.campos@...> wrote:

Hi

After have seen info about these new DSP receivers (like PL310/380) :

http://bbs.tecsun.com.cn/0002.asp?open=186695

I wonder if it would support loop antennas, like square air coil or even ferrite loops.

If one issue to add : living near big power MW stations.

Have anyone tried MW dx in this conditions ?

Regards
Sarmento - Rio de Janeiro - Brazil


Gary DeBock
 

Hi Ralph,
 
As you probably know, because of the response delay in the RSSI and S/N readings on the PL-380 digital display, simply watching the readings in unlikely to be of much benefit in peaking the inductively-coupled external loops. For casual DXing I've had good results listening carefully for an audio signal peak while slowly tuning the external loops, and then fine-tuning the peak (using the display's S/N reading) as the loop's frequency is carefully adjusted from that point.
 
For urgent DXpedition situations like a sunrise TP opening on an ocean beach (which may be in total darkness) I simply use a modified ICF-2010 SSB spotting receiver to find TP targets, then tune the external loop to light up the ICF-2010's LED signal display on that frequency. The external loop is then perfectly peaked to boost reception on the PL-380, which only needs to be brought within inductive coupling range for a huge DXing boost. The entire procedure can be done in total darkness, and provides great results.
 
73, Gary   
 
In a message dated 7/6/2010 1:54:22 P.M. Pacific Daylight Time, rpollock@... writes:

 

The trick is how to peak the inductively coupled loop, be it air core or ferrite bar.  Any tips?

From: ultralightdx@yahoogroups.com [ultralightdx@yahoogroups.com] On Behalf Of D1028Gary@aol.com [D1028Gary@aol.com]
Sent: Tuesday, July 06, 2010 3:32 PM
To: ultralightdx@yahoogroups.com
Subject: Re: [ultralightdx] Question about ultralight and loops for MW

 

Hello Sarmento,
 
Many air core and ferrite core external loops give excellent performance with the Tecsun PL-380 and PL-310 models, and make DXing a lot more fun.
 
Depending upon your DXing preferences, you can choose a transplanted ferrite loop (like the 7.5" loopstick PL-380), an inductively coupled ferrite loop (like the Q-stick) or a direct or inductively-coupled air core loop. All of these antenna designs have performance tradeoffs, and no one design is perfect for every situation.
 
Most DXers who wish to avoid "surgery" on the radio use air or ferrite core loops with the inductive coupling system, which gives an excellent performance boost (depending on the size of the loop) with an extra tuned circuit to aid in selectivity. The directly-connected ferrite and air core loops always require modification to the radio (and possibly the addition of other external hard-wired components), but avoid the need for a separate tuning step. 
 
My own favorite for convenient DXpedition usage is the 3' portable PVC air core loop, which is described in the photo article at  http://www.mediafire.com/?hqyzzu1mvyt . This tuned passive loop provides a powerful inductive coupling boost for the barefoot PL-380, can be assembled in 2 minutes, and will fit inside a packed compact car trunk.
 
73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)
 
 
 
In a message dated 7/6/2010 4:12:29 A.M. Pacific Daylight Time, sarmento.campos@sarmento.eng.br writes:
 

Hi

After have seen info about these new DSP receivers (like PL310/380) :

http://bbs.tecsun.com.cn/0002.asp?open=186695

I wonder if it would support loop antennas, like square air coil or even ferrite loops.

If one issue to add : living near big power MW stations.

Have anyone tried MW dx in this conditions ?

Regards
Sarmento - Rio de Janeiro - Brazil


Gary DeBock
 

"The directly-connected ferrite and air core loops always require modification to the radio (and possibly the addition of other external hard-wired components), but avoid the need for a separate tuning step."
 
Hello All,
 
This is one unique exception to the above statement-- the 7.5" plug-in loopstick PL-360, which requires no radio "surgery," but provides a nice AM performance boost. Having just sent out over 20 of these, I should have remembered this exception :-)
 
73, Gary  
 
In a message dated 7/6/2010 1:32:44 P.M. Pacific Daylight Time, D1028Gary@... writes:

 

Hello Sarmento,
 
Many air core and ferrite core external loops give excellent performance with the Tecsun PL-380 and PL-310 models, and make DXing a lot more fun.
 
Depending upon your DXing preferences, you can choose a transplanted ferrite loop (like the 7.5" loopstick PL-380), an inductively coupled ferrite loop (like the Q-stick) or a direct or inductively-coupled air core loop. All of these antenna designs have performance tradeoffs, and no one design is perfect for every situation.
 
Most DXers who wish to avoid "surgery" on the radio use air or ferrite core loops with the inductive coupling system, which gives an excellent performance boost (depending on the size of the loop) with an extra tuned circuit to aid in selectivity. The directly-connected ferrite and air core loops always require modification to the radio (and possibly the addition of other external hard-wired components), but avoid the need for a separate tuning step. 
 
My own favorite for convenient DXpedition usage is the 3' portable PVC air core loop, which is described in the photo article at  http://www.mediafire.com/?hqyzzu1mvyt . This tuned passive loop provides a powerful inductive coupling boost for the barefoot PL-380, can be assembled in 2 minutes, and will fit inside a packed compact car trunk.
 
73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)
 
 
 
In a message dated 7/6/2010 4:12:29 A.M. Pacific Daylight Time, sarmento.campos@sarmento.eng.br writes:
 

Hi

After have seen info about these new DSP receivers (like PL310/380) :

http://bbs.tecsun.com.cn/0002.asp?open=186695

I wonder if it would support loop antennas, like square air coil or even ferrite loops.

If one issue to add : living near big power MW stations.

Have anyone tried MW dx in this conditions ?

Regards
Sarmento - Rio de Janeiro - Brazil


Pollock,Raphael E <rpollock@...>
 

The trick is how to peak the inductively coupled loop, be it air core or ferrite bar.  Any tips?

From: ultralightdx@... [ultralightdx@...] On Behalf Of D1028Gary@... [D1028Gary@...]
Sent: Tuesday, July 06, 2010 3:32 PM
To: ultralightdx@...
Subject: Re: [ultralightdx] Question about ultralight and loops for MW

 

Hello Sarmento,
 
Many air core and ferrite core external loops give excellent performance with the Tecsun PL-380 and PL-310 models, and make DXing a lot more fun.
 
Depending upon your DXing preferences, you can choose a transplanted ferrite loop (like the 7.5" loopstick PL-380), an inductively coupled ferrite loop (like the Q-stick) or a direct or inductively-coupled air core loop. All of these antenna designs have performance tradeoffs, and no one design is perfect for every situation.
 
Most DXers who wish to avoid "surgery" on the radio use air or ferrite core loops with the inductive coupling system, which gives an excellent performance boost (depending on the size of the loop) with an extra tuned circuit to aid in selectivity. The directly-connected ferrite and air core loops always require modification to the radio (and possibly the addition of other external hard-wired components), but avoid the need for a separate tuning step. 
 
My own favorite for convenient DXpedition usage is the 3' portable PVC air core loop, which is described in the photo article at  http://www.mediafire.com/?hqyzzu1mvyt . This tuned passive loop provides a powerful inductive coupling boost for the barefoot PL-380, can be assembled in 2 minutes, and will fit inside a packed compact car trunk.
 
73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)
 
 
 
In a message dated 7/6/2010 4:12:29 A.M. Pacific Daylight Time, sarmento.campos@sarmento.eng.br writes:

 

Hi

After have seen info about these new DSP receivers (like PL310/380) :

http://bbs.tecsun.com.cn/0002.asp?open=186695

I wonder if it would support loop antennas, like square air coil or even ferrite loops.

If one issue to add : living near big power MW stations.

Have anyone tried MW dx in this conditions ?

Regards
Sarmento - Rio de Janeiro - Brazil


pianoplayer88key
 

He also asked about the issue of living near high powered MW stations. I'll share a little of my experience. In rural areas (or other areas that don't have a strong signal nearby), I've found that the noise floor, as indicated on the radio, is 15dBu RSSI. I've seen stations that had a listenable signal at 15dBu RSSI, 18dB SNR or so. Yesterday I saw a 17dBu RSSI, 22dB SNR signal while my radio was inside a car (which attenuated the strong signals).
However.... when there are strong signals, it seems to desensitize the radio some. This is manifested by elevated RSSI readings across much of the band. For example, I live about 9 miles from a 50kW daytimer (2.9kW night) on 1170, 6 miles from a 10kW on 1130, and 7 miles from a 50kW nighttimer (5kW daytime) on 760. Except for the extreme edges of the band, the RSSI reading across most of the band on my Tecsun PL-380 is about 30dBu on otherwise "empty" channels. Within about 20-30kHz or so of the strong stations I mentioned, the RSSI will hit 39dBu or 41dBu, sometimes 43dBu between channels.
Also, my grandparents in San Gabriel, CA, live about 0.3 mi from a 23kW on 1300 and a 50kW on 1430, and about 5 mi from a 50kW IBOC on 1110. When I last visited them a few months ago, the RSSI throughout most of the band above about 1000 kHz or so was 49 to 50dBu on the "blank" channels.
Also, I experimented (and posted the results in an earlier post) with taking an older radio I have, generating the local oscillator carrier, and putting my PL-380 near it. When the other radio was on, the PL-380 would be showing 50dBu about +/- 150kHz from the frequency the other radio's LO was on. So, with the other radio turned off, and being in a car to partially shield the strong signals (so I wouldn't get the aforementioned 41dBu RSSI on a few frequencies, or 30dBu across the band; it was 15dBu across most of the band, maybe 20dBu near the strong stations), I would find a few stations to compare. Basically, with the other interference/carrier turned off, I might be able to hear a station that was about 35 to 40 dBu or so quite well. However, when turning that other radio (and its local oscillator) on, the target station went to fairly clear (with a little static) to virtually undetectable, if I remember correctly.
Also, I went near the transmitter site of a semi-local on 1450, and compared my PL-380 with a radio I have, the Panasonic RQ-SW20, which has selectivity comparable to the Sony SRF-M37 series radios. I also posted links to mp3 recordings of some of those comparisons, which I will not repeat here, except that there were several stations that, in spite of the horrible selectivity on the RQ-SW20 (1450 was being heard across several hundred kHz on frequencies where there weren't other stations on the dial), could be heard fairly well on the SW20, but were either extremely faint or just not there at all on the PL-380. Normally, the PL-380 is at least several dB more sensitive than the SW20, at least when it's not swamped by strong signals.

Now... Gary... what's your experience? I understand you can get perfectly clean audio from a distant station on 1460 (for which you're almost on radio-locator's fringe contour if I remember correctly), while you're about 3 miles from a local on 1450. I don't think my PL-380 would have a chance at that... not to mention that even in the 1kHz bandwidth mode, I often get somewhat noticeable splatter 10kHz away from 10kW stations about 30 miles away or so. (Also I think you've mentioned that my own PL-380 is probably defective. Any ideas on how to get it replaced? I would prefer not to spend the money on buying another one, unless I can get a vertically-oriented radio with multiple bandwidths and a good built-in Amidon-61 loopstick that doesn't protrude above the cabinet. The PL-360 won't cut it for me - single bandwidth, I'm afraid that the antenna will break off when I put the radio in my pants pocket where it will be primarily used (and where I was originally hoping to use the PL-380 but it won't fit there so by my definition it's not a ULR (although it still is by the committee's definition))... and I would prefer one a little wider (max of 4 inches IF the cabinet is no more than an inch thick, preferably 3.5" wide or less) so it can have a better loopstick in it, but shorter to keep its size under control.

So... Gary... when do you think you'll have the opportunity to check the RSSI near your strong signals? I would think your PL-380 shows 63dBu at 1450kHz (mine is capped at 63dBu, and it shows that on 5kW stations 8-10 miles away)... and based on how good the selectivity is on your specific PL-380, it would show 15dBu on 1440 and maybe 1460, right? Or what does it read? (Mine would probably read upwards of 30-45dBu where you are, not 15dBu. :( )

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

Hello Sarmento,

Many air core and ferrite core external loops give excellent performance
with the Tecsun PL-380 and PL-310 models, and make DXing a lot more fun.

Depending upon your DXing preferences, you can choose a transplanted
ferrite loop (like the 7.5" loopstick PL-380), an inductively coupled ferrite
loop (like the Q-stick) or a direct or inductively-coupled air core loop. All
of these antenna designs have performance tradeoffs, and no one design is
perfect for every situation.

Most DXers who wish to avoid "surgery" on the radio use air or ferrite core
loops with the inductive coupling system, which gives an excellent
performance boost (depending on the size of the loop) with an extra tuned circuit
to aid in selectivity. The directly-connected ferrite and air core loops
always require modification to the radio (and possibly the addition of other
external hard-wired components), but avoid the need for a separate tuning
step.

My own favorite for convenient DXpedition usage is the 3' portable PVC air
core loop, which is described in the photo article at
_http://www.mediafire.com/?hqyzzu1mvyt_ (http://www.mediafire.com/?hqyzzu1mvyt) . This tuned
passive loop provides a powerful inductive coupling boost for the barefoot
PL-380, can be assembled in 2 minutes, and will fit inside a packed compact
car trunk.

73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)




In a message dated 7/6/2010 4:12:29 A.M. Pacific Daylight Time,
sarmento.campos@... writes:




Hi

After have seen info about these new DSP receivers (like PL310/380) :

_http://bbs.tecsun.com.cn/0002.asp?open=186695_
(http://bbs.tecsun.com.cn/0002.asp?open=186695)

I wonder if it would support loop antennas, like square air coil or even
ferrite loops.

If one issue to add : living near big power MW stations.

Have anyone tried MW dx in this conditions ?

Regards
Sarmento - Rio de Janeiro - Brazil


pianoplayer88key
 

But, Gary... will that PL-360 with its plug-in 7.5" loopstick still fit in a shirt pocket or pants pocket, and be properly oriented (i.e. not vertical, reducing the signal pickup)? If I understand correctly, one of the intents of having ULRs be no larger than a certain size was so they would fit in pockets.

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

"The directly-connected ferrite and air core loops always require
modification to the radio (and possibly the addition of other external hard-wired
components), but avoid the need for a separate tuning step."

Hello All,

This is one unique exception to the above statement-- the 7.5" plug-in
loopstick PL-360, which requires no radio "surgery," but provides a nice AM
performance boost. Having just sent out over 20 of these, I should have
remembered this exception :-)

73, Gary


In a message dated 7/6/2010 1:32:44 P.M. Pacific Daylight Time,
D1028Gary@... writes:




Hello Sarmento,

Many air core and ferrite core external loops give excellent performance
with the Tecsun PL-380 and PL-310 models, and make DXing a lot more fun.

Depending upon your DXing preferences, you can choose a transplanted
ferrite loop (like the 7.5" loopstick PL-380), an inductively coupled ferrite
loop (like the Q-stick) or a direct or inductively-or a direct or
inductively-<WBR>coupled air core loop. All of these antenna designs have performance
tradeoffs, and no one design

Most DXers who wish to avoid "surgery" on the radio use air or ferrite
core loops with the inductive coupling system, which gives an excellent
performance boost (depending on the size of the loop) with an extra tuned circuit
to aid in selectivity. The directly-connected ferrite and air core loops
always require modification to the radio (and possibly the addition of other
external hard-wired components), but avoid the need for a separate tuning
step.

My own favorite for convenient DXpedition usage is the 3' portable PVC air
core loop, which is described in the photo article at
_http://www.mediafirhttp://www.mediaht_ (http://www.mediafire.com/?hqyzzu1mvyt) . This tuned
passive loop provides a powerful inductive coupling boost for the barefoot
PL-380, can be assembled in 2 minutes, and will fit inside a packed compact
car trunk.

73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)




In a message dated 7/6/2010 4:12:29 A.M. Pacific Daylight Time,
sarmento.campos@In a messIn a message d


Hi

After have seen info about these new DSP receivers (like PL310/380) :

_http://bbs.tecsun.http://bbs.thttp://bbhttp:/_
(http://bbs.tecsun.com.cn/0002.asp?open=186695)

I wonder if it would support loop antennas, like square air coil or even
ferrite loops.

If one issue to add : living near big power MW stations.

Have anyone tried MW dx in this conditions ?

Regards
Sarmento - Rio de Janeiro - Brazil


Pollock,Raphael E <rpollock@...>
 




On Jul 6, 2010, at 5:26 PM, "Stephen" <pianoplayer88key@...> wrote:

 

But, Gary... will that PL-360 with its plug-in 7.5" loopstick still fit in a shirt pocket or pants pocket, and be properly oriented (i.e. not vertical, reducing the signal pickup)? If I understand correctly, one of the intents of having ULRs be no larger than a certain size was so they would fit in pockets.

--- In ultralightdx@..., D1028Gary@... wrote:
>
> "The directly-connected ferrite and air core loops always require
> modification to the radio (and possibly the addition of other external hard-wired
> components), but avoid the need for a separate tuning step."
>
> Hello All,
>
> This is one unique exception to the above statement-- the 7.5" plug-in
> loopstick PL-360, which requires no radio "surgery," but provides a nice AM
> performance boost. Having just sent out over 20 of these, I should have
> remembered this exception :-)
>
> 73, Gary
>
>
> In a message dated 7/6/2010 1:32:44 P.M. Pacific Daylight Time,
> D1028Gary@... writes:
>
>
>
>
> Hello Sarmento,
>
> Many air core and ferrite core external loops give excellent performance
> with the Tecsun PL-380 and PL-310 models, and make DXing a lot more fun.
>
> Depending upon your DXing preferences, you can choose a transplanted
> ferrite loop (like the 7.5" loopstick PL-380), an inductively coupled ferrite
> loop (like the Q-stick) or a direct or inductively-or a direct or
> inductively-<WBR>coupled air core loop. All of these antenna designs have performance
> tradeoffs, and no one design
>
> Most DXers who wish to avoid "surgery" on the radio use air or ferrite
> core loops with the inductive coupling system, which gives an excellent
> performance boost (depending on the size of the loop) with an extra tuned circuit
> to aid in selectivity. The directly-connected ferrite and air core loops
> always require modification to the radio (and possibly the addition of other
> external hard-wired components), but avoid the need for a separate tuning
> step.
>
> My own favorite for convenient DXpedition usage is the 3' portable PVC air
> core loop, which is described in the photo article at
> _http://www.mediafirhttp://www.mediaht_ (http://www.mediafire.com/?hqyzzu1mvyt) . This tuned
> passive loop provides a powerful inductive coupling boost for the barefoot
> PL-380, can be assembled in 2 minutes, and will fit inside a packed compact
> car trunk.
>
> 73 and Good DX,
> Gary DeBock (in Puyallup, WA, USA)
>
>
>
>
> In a message dated 7/6/2010 4:12:29 A.M. Pacific Daylight Time,
> sarmento.campos@In a messIn a message d
>
>
> Hi
>
> After have seen info about these new DSP receivers (like PL310/380) :
>
> _http://bbs.tecsun.http://bbs.thttp://bbhttp:/_
> (http://bbs.tecsun.com.cn/0002.asp?open=186695)
>
> I wonder if it would support loop antennas, like square air coil or even
> ferrite loops.
>
> If one issue to add : living near big power MW stations.
>
> Have anyone tried MW dx in this conditions ?
>
> Regards
> Sarmento - Rio de Janeiro - Brazil
>


Rik
 

The slowness of the RSSI read out made me long for a DSP eadio which would tune an external antenna, That is what got me excited about the PL-360, since trying to tune my air core loops for the G8 was nearly impossible. Using an other radio is one solution. It seeme we all have our own self imposed restrictions. Some want a DSP ULR to replace a communications receiver while just sitting near a running computer, and others want a DSP ULR to be just as portable with an external antenna as without one. It is all relative I guess. - FARMERIK

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

Hi Ralph,

As you probably know, because of the response delay in the RSSI and S/N
readings on the PL-380 digital display, simply watching the readings in
unlikely to be of much benefit in peaking the inductively-coupled external
loops. For casual DXing I've had good results listening carefully for an audio
signal peak while slowly tuning the external loops, and then fine-tuning the
peak (using the display's S/N reading) as the loop's frequency is carefully
adjusted from that point.

For urgent DXpedition situations like a sunrise TP opening on an ocean
beach (which may be in total darkness) I simply use a modified ICF-2010 SSB
spotting receiver to find TP targets, then tune the external loop to light up
the ICF-2010's LED signal display on that frequency. The external loop is
then perfectly peaked to boost reception on the PL-380, which only needs to
be brought within inductive coupling range for a huge DXing boost. The
entire procedure can be done in total darkness, and provides great results.

73, Gary


In a message dated 7/6/2010 1:54:22 P.M. Pacific Daylight Time,
rpollock@... writes:




The trick is how to peak the inductively coupled loop, be it air core or
ferrite bar. Any tips?

____________________________________
From: ultralightdx@ ultralightd ultralightdx@<WBR>yah ultralightd
ultralightdx@<WBR>yahoogroups. ultralightdx@<WBR>yaho ult
Sent: Tuesday, July 06, 2010 3:32 PM
To: ultralightdx@ ultralightd ul
Subject: Re: [ultralightdx] Question about ultralight and loops for MW







Hello Sarmento,

Many air core and ferrite core external loops give excellent performance
with the Tecsun PL-380 and PL-310 models, and make DXing a lot more fun.

Depending upon your DXing preferences, you can choose a transplanted
ferrite loop (like the 7.5" loopstick PL-380), an inductively coupled ferrite
loop (like the Q-stick) or a direct or inductively-or a direct or
inductively-<WBR>coupled air core loop. All of these antenna designs have performance
tradeoffs, and no one design

Most DXers who wish to avoid "surgery" on the radio use air or ferrite
core loops with the inductive coupling system, which gives an excellent
performance boost (depending on the size of the loop) with an extra tuned circuit
to aid in selectivity. The directly-connected ferrite and air core loops
always require modification to the radio (and possibly the addition of other
external hard-wired components), but avoid the need for a separate tuning
step.

My own favorite for convenient DXpedition usage is the 3' portable PVC air
core loop, which is described in the photo article at
_http://www.mediafirhttp://www.mediaht_ (http://www.mediafire.com/?hqyzzu1mvyt) . This tuned
passive loop provides a powerful inductive coupling boost for the barefoot
PL-380, can be assembled in 2 minutes, and will fit inside a packed compact
car trunk.

73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)




In a message dated 7/6/2010 4:12:29 A.M. Pacific Daylight Time,
sarmento.campos@In a messIn a message d


Hi

After have seen info about these new DSP receivers (like PL310/380) :

_http://bbs.tecsun.http://bbs.thttp://bbhttp:/_
(http://bbs.tecsun.com.cn/0002.asp?open=186695)

I wonder if it would support loop antennas, like square air coil or even
ferrite loops.

If one issue to add : living near big power MW stations.

Have anyone tried MW dx in this conditions ?

Regards
Sarmento - Rio de Janeiro - Brazil


sarmento2k
 

Hi Stephen

Thats my doubt!

When I use a Sony 7600GR or Degen 1103 with a passive and inductive loop for MW, there is also internal generation of images all over the band. The local super power harms the front end, either with overloading or with desensitization of the receiver.

One workaround is to decrease gain or place the antenna a little bit away from the receiver.

But I'm really thinking of purchasing a Tecsun PL380 to make the tests.

I have made a little ferrite loop (a bundle of 3 ferrite rods with 9 inches length and litz wire and an Alps capacitor) with resonates at the entire MW band.

Not high gain, but maybe the adequate to inductive couple with the internal ferrite.

Thanks all for all attention,

Sarmento

--- In ultralightdx@..., "Stephen" <pianoplayer88key@...> wrote:

He also asked about the issue of living near high powered MW stations. I'll share a little of my experience. In rural areas (or other areas that don't have a strong signal nearby), I've found that the noise floor, as indicated on the radio, is 15dBu RSSI. I've seen stations that had a listenable signal at 15dBu RSSI, 18dB SNR or so. Yesterday I saw a 17dBu RSSI, 22dB SNR signal while my radio was inside a car (which attenuated the strong signals).
However.... when there are strong signals, it seems to desensitize the radio some. This is manifested by elevated RSSI readings across much of the band. For example, I live about 9 miles from a 50kW daytimer (2.9kW night) on 1170, 6 miles from a 10kW on 1130, and 7 miles from a 50kW nighttimer (5kW daytime) on 760. Except for the extreme edges of the band, the RSSI reading across most of the band on my Tecsun PL-380 is about 30dBu on otherwise "empty" channels. Within about 20-30kHz or so of the strong stations I mentioned, the RSSI will hit 39dBu or 41dBu, sometimes 43dBu between channels.
Also, my grandparents in San Gabriel, CA, live about 0.3 mi from a 23kW on 1300 and a 50kW on 1430, and about 5 mi from a 50kW IBOC on 1110. When I last visited them a few months ago, the RSSI throughout most of the band above about 1000 kHz or so was 49 to 50dBu on the "blank" channels.
Also, I experimented (and posted the results in an earlier post) with taking an older radio I have, generating the local oscillator carrier, and putting my PL-380 near it. When the other radio was on, the PL-380 would be showing 50dBu about +/- 150kHz from the frequency the other radio's LO was on. So, with the other radio turned off, and being in a car to partially shield the strong signals (so I wouldn't get the aforementioned 41dBu RSSI on a few frequencies, or 30dBu across the band; it was 15dBu across most of the band, maybe 20dBu near the strong stations), I would find a few stations to compare. Basically, with the other interference/carrier turned off, I might be able to hear a station that was about 35 to 40 dBu or so quite well. However, when turning that other radio (and its local oscillator) on, the target station went to fairly clear (with a little static) to virtually undetectable, if I remember correctly.
Also, I went near the transmitter site of a semi-local on 1450, and compared my PL-380 with a radio I have, the Panasonic RQ-SW20, which has selectivity comparable to the Sony SRF-M37 series radios. I also posted links to mp3 recordings of some of those comparisons, which I will not repeat here, except that there were several stations that, in spite of the horrible selectivity on the RQ-SW20 (1450 was being heard across several hundred kHz on frequencies where there weren't other stations on the dial), could be heard fairly well on the SW20, but were either extremely faint or just not there at all on the PL-380. Normally, the PL-380 is at least several dB more sensitive than the SW20, at least when it's not swamped by strong signals.

Now... Gary... what's your experience? I understand you can get perfectly clean audio from a distant station on 1460 (for which you're almost on radio-locator's fringe contour if I remember correctly), while you're about 3 miles from a local on 1450. I don't think my PL-380 would have a chance at that... not to mention that even in the 1kHz bandwidth mode, I often get somewhat noticeable splatter 10kHz away from 10kW stations about 30 miles away or so. (Also I think you've mentioned that my own PL-380 is probably defective. Any ideas on how to get it replaced? I would prefer not to spend the money on buying another one, unless I can get a vertically-oriented radio with multiple bandwidths and a good built-in Amidon-61 loopstick that doesn't protrude above the cabinet. The PL-360 won't cut it for me - single bandwidth, I'm afraid that the antenna will break off when I put the radio in my pants pocket where it will be primarily used (and where I was originally hoping to use the PL-380 but it won't fit there so by my definition it's not a ULR (although it still is by the committee's definition))... and I would prefer one a little wider (max of 4 inches IF the cabinet is no more than an inch thick, preferably 3.5" wide or less) so it can have a better loopstick in it, but shorter to keep its size under control.

So... Gary... when do you think you'll have the opportunity to check the RSSI near your strong signals? I would think your PL-380 shows 63dBu at 1450kHz (mine is capped at 63dBu, and it shows that on 5kW stations 8-10 miles away)... and based on how good the selectivity is on your specific PL-380, it would show 15dBu on 1440 and maybe 1460, right? Or what does it read? (Mine would probably read upwards of 30-45dBu where you are, not 15dBu. :( )


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

Hello Sarmento,

Many air core and ferrite core external loops give excellent performance
with the Tecsun PL-380 and PL-310 models, and make DXing a lot more fun.

Depending upon your DXing preferences, you can choose a transplanted
ferrite loop (like the 7.5" loopstick PL-380), an inductively coupled ferrite
loop (like the Q-stick) or a direct or inductively-coupled air core loop. All
of these antenna designs have performance tradeoffs, and no one design is
perfect for every situation.

Most DXers who wish to avoid "surgery" on the radio use air or ferrite core
loops with the inductive coupling system, which gives an excellent
performance boost (depending on the size of the loop) with an extra tuned circuit
to aid in selectivity. The directly-connected ferrite and air core loops
always require modification to the radio (and possibly the addition of other
external hard-wired components), but avoid the need for a separate tuning
step.

My own favorite for convenient DXpedition usage is the 3' portable PVC air
core loop, which is described in the photo article at
_http://www.mediafire.com/?hqyzzu1mvyt_ (http://www.mediafire.com/?hqyzzu1mvyt) . This tuned
passive loop provides a powerful inductive coupling boost for the barefoot
PL-380, can be assembled in 2 minutes, and will fit inside a packed compact
car trunk.

73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)




In a message dated 7/6/2010 4:12:29 A.M. Pacific Daylight Time,
sarmento.campos@ writes:




Hi

After have seen info about these new DSP receivers (like PL310/380) :

_http://bbs.tecsun.com.cn/0002.asp?open=186695_
(http://bbs.tecsun.com.cn/0002.asp?open=186695)

I wonder if it would support loop antennas, like square air coil or even
ferrite loops.

If one issue to add : living near big power MW stations.

Have anyone tried MW dx in this conditions ?

Regards
Sarmento - Rio de Janeiro - Brazil