main@UltralightDX.groups.io | Matching transformer for PL-380

hans.ostnell@...

Group,

Anyone who could suggest a matching transformer to use when connecting the 50 Ohm output from my Quantum QX-loop directly to the PL-380?

What I'm doing now is to switch between the 7.5" loopstick and the QX-loop. The QX works pretty good together with the 380, actually, but I can see that I'm not taking full advantage of the QX sensibililty (i.e I loose gain from the loop when connecting it diretly to the ferrite input on the PL-380). This is most likely due to the impedance mismatch between the QX output and the ferrite input on the 380.

Yes, It works fine tocouple the QX inductive via the 7.5" loopstick, but I would like to experiment a bit with disconnecting the 7.5" loopstick from the system.

73,

Hans

Vardo, Arctic Norway

maurits van driessche <mauritsvandriessche@...>

#22428

you always lose signal when you connect the antenna to the radio. Do this several times tried, best is an antenna preamp.
73,
Maurits
Belgium

Show quoted text

Group,

Anyone who could suggest a matching transformer to use when connecting the 50 Ohm output from my Quantum QX-loop directly to the PL-380?

What I'm doing now is to switch between the 7.5" loopstick and the QX-loop. The QX works pretty good together with the 380, actually, but I can see that I'm not taking full advantage of the QX sensibililty (i.e I loose gain from the loop when connecting it diretly to the ferrite input on the PL-380). This is most likely due to the impedance mismatch between the QX output and the ferrite input on the 380.

Yes, It works fine tocouple the QX inductive via the 7.5" loopstick, but I would like to experiment a bit with disconnecting the 7.5" loopstick from the system.

73,

Hans

Vardo, Arctic Norway

Richard Jones

#22434

I'm not sure I understand exactly what you are doing but be VERY careful if you are connecting an external signal directly to the solder pads where the loop wires go. Go to Silicone Labs website and download the documentation for the Silicon Labs si4734 chip. You will notice that the loopstick forms a resonant circuit with varicaps embedded in the chip. To tune the radio the DSP changes the capacitor value effectively resonating the tank circuit to the desired frequency. In other words, the radio has its own internal tuned loop circuit. Attaching any high level signal in place of a loopstick seems dangerous. Additionally, there are many ESD warnings to the possibility of zapping the chip at the antenna input unless an external capacitor is used for protection when bringing in external signals. Indirectly coupling a signal into the original or supercharged loopstick seems to be the best and safest way as far as I can tell. Rick

---In ultralightdx@..., <hans.ostnell@...> wrote:

Group,

Anyone who could suggest a matching transformer to use when connecting the 50 Ohm output from my Quantum QX-loop directly to the PL-380?

What I'm doing now is to switch between the 7.5" loopstick and the QX-loop. The QX works pretty good together with the 380, actually, but I can see that I'm not taking full advantage of the QX sensibililty (i.e I loose gain from the loop when connecting it diretly to the ferrite input on the PL-380). This is most likely due to the impedance mismatch between the QX output and the ferrite input on the 380.

Yes, It works fine tocouple the QX inductive via the 7.5" loopstick, but I would like to experiment a bit with disconnecting the 7.5" loopstick from the system.

73,

Hans

Vardo, Arctic Norway

hans.ostnell@...

#22442

You're absolutely right, Rick. The best results I've achieved with the Quantum loop + PL-380 combo is when the Quantum is inductively coupled to the 7.5" loopstick on the modified PL-380, by means of the Quantum coupler. This works excellent.

Hans

Vardo isl. Arctic Norway

---In ultralightdx@..., <n3ikq@...> wrote:

I'm not sure I understand exactly what you are doing but be VERY careful if you are connecting an external signal directly to the solder pads where the loop wires go. Go to Silicone Labs website and download the documentation for the Silicon Labs si4734 chip. You will notice that the loopstick forms a resonant circuit with varicaps embedded in the chip. To tune the radio the DSP changes the capacitor value effectively resonating the tank circuit to the desired frequency. In other words, the radio has its own internal tuned loop circuit. Attaching any high level signal in place of a loopstick seems dangerous. Additionally, there are many ESD warnings to the possibility of zapping the chip at the antenna input unless an external capacitor is used for protection when bringing in external signals. Indirectly coupling a signal into the original or supercharged loopstick seems to be the best and safest way as far as I can tell. Rick

---In ultralightdx@..., <hans.ostnell@...> wrote:

Group,

Anyone who could suggest a matching transformer to use when connecting the 50 Ohm output from my Quantum QX-loop directly to the PL-380?

What I'm doing now is to switch between the 7.5" loopstick and the QX-loop. The QX works pretty good together with the 380, actually, but I can see that I'm not taking full advantage of the QX sensibililty (i.e I loose gain from the loop when connecting it diretly to the ferrite input on the PL-380). This is most likely due to the impedance mismatch between the QX output and the ferrite input on the 380.

Yes, It works fine tocouple the QX inductive via the 7.5" loopstick, but I would like to experiment a bit with disconnecting the 7.5" loopstick from the system.

73,

Hans

Vardo, Arctic Norway

kugellagers

#22444

I don't think he is talking about directly soldering wires to the PL-380 antenna inputs. I think he is trying to match his 50 ohm coax to the input impedence of the antenna input using a torid matching transformer.

For example, I have a Rycom 1307A-GR which I use for my non-ultralight LW DX. Its RF input impedence is not the typical 50 ohm input but is a 3000+ ohm input. To match my 75 ohm RG6 Quad shield coax to the 3000 ohm input of the radio I need a matching transformer that gives me aobout a 40:1 RF ratio. For this I use a FT140 type J toroid with 38T:6T giving me about a 40:1 RF ratio.

This isolates the coax from the radio but still matches the two different impedences allowing for maximum signal transfer from the coax to the radio.

I think this is what Hans wants to do.

So the question is: What is the input impedence of the PL-380 antenna input? It seems like since it is a variable matching circuit there must be some ideal middle value impedence he can use to match the coax to the radio.

I would actually like to do this as well so that I do not have to lug around a fragile ferrite rod loopstick to inductively couple an external antenna as I do now. Internal antenna has been removed..

John

];')

---In ultralightdx@..., <hans.ostnell@...> wrote:

You're absolutely right, Rick. The best results I've achieved with the Quantum loop + PL-380 combo is when the Quantum is inductively coupled to the 7.5" loopstick on the modified PL-380, by means of the Quantum coupler. This works excellent.

Hans

Vardo isl. Arctic Norway

---In ultralightdx@..., <n3ikq@...> wrote:

I'm not sure I understand exactly what you are doing but be VERY careful if you are connecting an external signal directly to the solder pads where the loop wires go. Go to Silicone Labs website and download the documentation for the Silicon Labs si4734 chip. You will notice that the loopstick forms a resonant circuit with varicaps embedded in the chip. To tune the radio the DSP changes the capacitor value effectively resonating the tank circuit to the desired frequency. In other words, the radio has its own internal tuned loop circuit. Attaching any high level signal in place of a loopstick seems dangerous. Additionally, there are many ESD warnings to the possibility of zapping the chip at the antenna input unless an external capacitor is used for protection when bringing in external signals. Indirectly coupling a signal into the original or supercharged loopstick seems to be the best and safest way as far as I can tell. Rick

---In ultralightdx@..., <hans.ostnell@...> wrote:

Group,

Anyone who could suggest a matching transformer to use when connecting the 50 Ohm output from my Quantum QX-loop directly to the PL-380?

What I'm doing now is to switch between the 7.5" loopstick and the QX-loop. The QX works pretty good together with the 380, actually, but I can see that I'm not taking full advantage of the QX sensibililty (i.e I loose gain from the loop when connecting it diretly to the ferrite input on the PL-380). This is most likely due to the impedance mismatch between the QX output and the ferrite input on the 380.

Yes, It works fine tocouple the QX inductive via the 7.5" loopstick, but I would like to experiment a bit with disconnecting the 7.5" loopstick from the system.

73,

Hans

Vardo, Arctic Norway

Richard Jones

#22446

There is no external antenna input on the PL-380. The DSP chip needs an inductor for AM/LW and a whip/wire for SW. The details are in the documentation at Silicone Labs website.

---In ultralightdx@..., <kugellager@...> wrote:

I don't think he is talking about directly soldering wires to the PL-380 antenna inputs. I think he is trying to match his 50 ohm coax to the input impedence of the antenna input using a torid matching transformer.

For example, I have a Rycom 1307A-GR which I use for my non-ultralight LW DX. Its RF input impedence is not the typical 50 ohm input but is a 3000+ ohm input. To match my 75 ohm RG6 Quad shield coax to the 3000 ohm input of the radio I need a matching transformer that gives me aobout a 40:1 RF ratio. For this I use a FT140 type J toroid with 38T:6T giving me about a 40:1 RF ratio.

This isolates the coax from the radio but still matches the two different impedences allowing for maximum signal transfer from the coax to the radio.

I think this is what Hans wants to do.

So the question is: What is the input impedence of the PL-380 antenna input? It seems like since it is a variable matching circuit there must be some ideal middle value impedence he can use to match the coax to the radio.

I would actually like to do this as well so that I do not have to lug around a fragile ferrite rod loopstick to inductively couple an external antenna as I do now. Internal antenna has been removed..

John

];')

---In ultralightdx@..., <hans.ostnell@...> wrote:

You're absolutely right, Rick. The best results I've achieved with the Quantum loop + PL-380 combo is when the Quantum is inductively coupled to the 7.5" loopstick on the modified PL-380, by means of the Quantum coupler. This works excellent.

Hans

Vardo isl. Arctic Norway

---In ultralightdx@..., <n3ikq@...> wrote:

I'm not sure I understand exactly what you are doing but be VERY careful if you are connecting an external signal directly to the solder pads where the loop wires go. Go to Silicone Labs website and download the documentation for the Silicon Labs si4734 chip. You will notice that the loopstick forms a resonant circuit with varicaps embedded in the chip. To tune the radio the DSP changes the capacitor value effectively resonating the tank circuit to the desired frequency. In other words, the radio has its own internal tuned loop circuit. Attaching any high level signal in place of a loopstick seems dangerous. Additionally, there are many ESD warnings to the possibility of zapping the chip at the antenna input unless an external capacitor is used for protection when bringing in external signals. Indirectly coupling a signal into the original or supercharged loopstick seems to be the best and safest way as far as I can tell. Rick

---In ultralightdx@..., <hans.ostnell@...> wrote:

Group,

Anyone who could suggest a matching transformer to use when connecting the 50 Ohm output from my Quantum QX-loop directly to the PL-380?

What I'm doing now is to switch between the 7.5" loopstick and the QX-loop. The QX works pretty good together with the 380, actually, but I can see that I'm not taking full advantage of the QX sensibililty (i.e I loose gain from the loop when connecting it diretly to the ferrite input on the PL-380). This is most likely due to the impedance mismatch between the QX output and the ferrite input on the 380.

Yes, It works fine tocouple the QX inductive via the 7.5" loopstick, but I would like to experiment a bit with disconnecting the 7.5" loopstick from the system.

73,

Hans

Vardo, Arctic Norway

kugellagers

#22447

There is if you have removed the internal antenna and added a 1/8" jack to plug in your 7.5" loopstick. ;')

John

];')

---In ultralightdx@..., <n3ikq@...> wrote:

There is no external antenna input on the PL-380. The DSP chip needs an inductor for AM/LW and a whip/wire for SW. The details are in the documentation at Silicone Labs website.

---In ultralightdx@..., <kugellager@...> wrote:

I don't think he is talking about directly soldering wires to the PL-380 antenna inputs. I think he is trying to match his 50 ohm coax to the input impedence of the antenna input using a torid matching transformer.

For example, I have a Rycom 1307A-GR which I use for my non-ultralight LW DX. Its RF input impedence is not the typical 50 ohm input but is a 3000+ ohm input. To match my 75 ohm RG6 Quad shield coax to the 3000 ohm input of the radio I need a matching transformer that gives me aobout a 40:1 RF ratio. For this I use a FT140 type J toroid with 38T:6T giving me about a 40:1 RF ratio.

This isolates the coax from the radio but still matches the two different impedences allowing for maximum signal transfer from the coax to the radio.

I think this is what Hans wants to do.

So the question is: What is the input impedence of the PL-380 antenna input? It seems like since it is a variable matching circuit there must be some ideal middle value impedence he can use to match the coax to the radio.

I would actually like to do this as well so that I do not have to lug around a fragile ferrite rod loopstick to inductively couple an external antenna as I do now. Internal antenna has been removed..

John

];')

---In ultralightdx@..., <hans.ostnell@...> wrote:

You're absolutely right, Rick. The best results I've achieved with the Quantum loop + PL-380 combo is when the Quantum is inductively coupled to the 7.5" loopstick on the modified PL-380, by means of the Quantum coupler. This works excellent.

Hans

Vardo isl. Arctic Norway

---In ultralightdx@..., <n3ikq@...> wrote:

I'm not sure I understand exactly what you are doing but be VERY careful if you are connecting an external signal directly to the solder pads where the loop wires go. Go to Silicone Labs website and download the documentation for the Silicon Labs si4734 chip. You will notice that the loopstick forms a resonant circuit with varicaps embedded in the chip. To tune the radio the DSP changes the capacitor value effectively resonating the tank circuit to the desired frequency. In other words, the radio has its own internal tuned loop circuit. Attaching any high level signal in place of a loopstick seems dangerous. Additionally, there are many ESD warnings to the possibility of zapping the chip at the antenna input unless an external capacitor is used for protection when bringing in external signals. Indirectly coupling a signal into the original or supercharged loopstick seems to be the best and safest way as far as I can tell. Rick

---In ultralightdx@..., <hans.ostnell@...> wrote:

Group,

Anyone who could suggest a matching transformer to use when connecting the 50 Ohm output from my Quantum QX-loop directly to the PL-380?

What I'm doing now is to switch between the 7.5" loopstick and the QX-loop. The QX works pretty good together with the 380, actually, but I can see that I'm not taking full advantage of the QX sensibililty (i.e I loose gain from the loop when connecting it diretly to the ferrite input on the PL-380). This is most likely due to the impedance mismatch between the QX output and the ferrite input on the 380.

Yes, It works fine tocouple the QX inductive via the 7.5" loopstick, but I would like to experiment a bit with disconnecting the 7.5" loopstick from the system.

73,

Hans

Vardo, Arctic Norway

Michael <michael.setaazul@...>

#22448

Show quoted text

----- Original Message -----  From: n3ikq

  
There is no external antenna input on the PL-380. The DSP chip needs 
an inductor for AM/LW and a whip/wire for SW. The details are in 
the documentation at Silicone Labs website. 

-------------------------------------------------

I  carefully  (!) soldered a LW coil   on a longer ferrite rod with 
parallel tuning capacitor in lieu of the internal ferrite antenna.

The internal and external tuning capacity co-existed, with
the internal self-adjusting to optimise the total capacitance.
Without the additional external variable capacitor, the 
internal capacitance auto-range was not sufficient for
the whole LW band as the inductance did not match
the automatic tuning facility as well as the internal
ferrite winding designed for the purpose, but which
is optimised for 540-1600kHz and less effective on LW. 

I used the same external L/C adjacent to the 
internal L/C with comparable  results.  This is doubtless
the safer approach. The hard-wired version produced 
better S/N, so would be warranted for optimal performance,
as in Gary's latest posting (We avidly await part 2!)

Michael

Richard Jones

#22450

True that, that's what I did so I could swap out AM/LW loopsticks. I'm just not sure that folks realize that this is not your ordinary radio front end. With signals going directly into a chip, you have no room for mistakes. Unless you can unsolder and replace a QFN chip without destroying the radio, caution would be highly recommended! Of course if you do turn the radio into a paperweight, the monetary loss is not too upsetting! Here is the link to some documentation:

http://travelx.org/Si4734.pdf

I'm not an expert but looking at the diagram, it looks like an I and Q signal is being generated much like the SDR I just built? I'm trying to keep up with the times!

---In ultralightdx@..., <kugellager@...> wrote:

There is if you have removed the internal antenna and added a 1/8" jack to plug in your 7.5" loopstick. ;')

John

];')

---In ultralightdx@..., <n3ikq@...> wrote:

There is no external antenna input on the PL-380. The DSP chip needs an inductor for AM/LW and a whip/wire for SW. The details are in the documentation at Silicone Labs website.

---In ultralightdx@..., <kugellager@...> wrote:

I don't think he is talking about directly soldering wires to the PL-380 antenna inputs. I think he is trying to match his 50 ohm coax to the input impedence of the antenna input using a torid matching transformer.

For example, I have a Rycom 1307A-GR which I use for my non-ultralight LW DX. Its RF input impedence is not the typical 50 ohm input but is a 3000+ ohm input. To match my 75 ohm RG6 Quad shield coax to the 3000 ohm input of the radio I need a matching transformer that gives me aobout a 40:1 RF ratio. For this I use a FT140 type J toroid with 38T:6T giving me about a 40:1 RF ratio.

This isolates the coax from the radio but still matches the two different impedences allowing for maximum signal transfer from the coax to the radio.

I think this is what Hans wants to do.

So the question is: What is the input impedence of the PL-380 antenna input? It seems like since it is a variable matching circuit there must be some ideal middle value impedence he can use to match the coax to the radio.

I would actually like to do this as well so that I do not have to lug around a fragile ferrite rod loopstick to inductively couple an external antenna as I do now. Internal antenna has been removed..

John

];')

---In ultralightdx@..., <hans.ostnell@...> wrote:

You're absolutely right, Rick. The best results I've achieved with the Quantum loop + PL-380 combo is when the Quantum is inductively coupled to the 7.5" loopstick on the modified PL-380, by means of the Quantum coupler. This works excellent.

Hans

Vardo isl. Arctic Norway

---In ultralightdx@..., <n3ikq@...> wrote:

I'm not sure I understand exactly what you are doing but be VERY careful if you are connecting an external signal directly to the solder pads where the loop wires go. Go to Silicone Labs website and download the documentation for the Silicon Labs si4734 chip. You will notice that the loopstick forms a resonant circuit with varicaps embedded in the chip. To tune the radio the DSP changes the capacitor value effectively resonating the tank circuit to the desired frequency. In other words, the radio has its own internal tuned loop circuit. Attaching any high level signal in place of a loopstick seems dangerous. Additionally, there are many ESD warnings to the possibility of zapping the chip at the antenna input unless an external capacitor is used for protection when bringing in external signals. Indirectly coupling a signal into the original or supercharged loopstick seems to be the best and safest way as far as I can tell. Rick

---In ultralightdx@..., <hans.ostnell@...> wrote:

Group,

Anyone who could suggest a matching transformer to use when connecting the 50 Ohm output from my Quantum QX-loop directly to the PL-380?

What I'm doing now is to switch between the 7.5" loopstick and the QX-loop. The QX works pretty good together with the 380, actually, but I can see that I'm not taking full advantage of the QX sensibililty (i.e I loose gain from the loop when connecting it diretly to the ferrite input on the PL-380). This is most likely due to the impedance mismatch between the QX output and the ferrite input on the 380.

Yes, It works fine tocouple the QX inductive via the 7.5" loopstick, but I would like to experiment a bit with disconnecting the 7.5" loopstick from the system.

73,

Hans

Vardo, Arctic Norway

Gary DeBock

#22451

Hi Michael, Hans, John, N3IKQ and all,

It's true that the Si4734 DSP chip in the PL-380 can adjust to a fairly wide range of loopstick coil impedances (nominally 150-450 uH), but the stock PL-380 loopstick (usually around 300 uH) is designed only for acceptable MW band coverage, and is nowhere near the optimal inductance for the Longwave frequencies (experimentally proven to be around 1700 uH, in the exhaustive experimentation described in the attached file). A DXer who wants excellent performance on both bands with a 7.5" loopstick faces a tough choice... either build two hot-rodded PL-380 models (one with a Medium Wave loopstick and one with a Longwave loopstick), or mount a plug-in socket on the PL-380 to switch between the two 7.5" loopsticks. The second approach would probably be a mechanical nightmare for many experimenters, but such a PL-380 model was built here in 2010 to accept the PL-360 7.5" plug-in loopsticks (photo attached).

73, Gary DeBock (in Puyallup, WA, USA)

Show quoted text

-----Original Message-----
From: Michael
To: ultralightdx
Sent: Fri, Nov 8, 2013 1:07 pm
Subject: Re: [ultralightdx] RE: RE: Matching transformer for PL-380

----- Original Message ----- From: n3ikq

There is no external antenna input on the PL-380. The DSP chip needs
an inductor for AM/LW and a whip/wire for SW. The details are in
the documentation at Silicone Labs website.

-------------------------------------------------

I carefully (!) soldered a LW coil on a longer ferrite rod with
parallel tuning capacitor in lieu of the internal ferrite antenna.

The internal and external tuning capacity co-existed, with
the internal self-adjusting to optimise the total capacitance.
Without the additional external variable capacitor, the
internal capacitance auto-range was not sufficient for
the whole LW band as the inductance did not match
the automatic tuning facility as well as the internal
ferrite winding designed for the purpose, but which
is optimised for 540-1600kHz and less effective on LW.

I used the same external L/C adjacent to the
internal L/C with comparable results. This is doubtless
the safer approach. The hard-wired version produced
better S/N, so would be warranted for optimal performance,
as in Gary's latest posting (We avidly await part 2!)

Michael

Andy Gardner <ceo@...>

#22453

Yes. I think you need to ensure that the inductance of the secondary of the matching transformer is of a value that allows the radio innards to tune across the band you're interested in.

Measuring the inductance of the built-in ferrite stick would give you a ball park figure I think.

Show quoted text

On 9/11/2013, at 9:09 AM, <n3ikq@...> <n3ikq@...> wrote:

There is no external antenna input on the PL-380. The DSP chip needs an inductor for AM/LW and a whip/wire for SW. The details are in the documentation at Silicone Labs website.