Ferrite antenna advice for LW


John
 

I have a Tecsun PL-330 which is known to be very deaf on LW. I also have a Roberts R993 (quite basic transistor radio) which has very good LW sensitivity. As a little project, I took the internal ferrite antenna for the Roberts and used it to make an external antenna for the Tecsun, following a procedure analogous to the one here https://swling.com/blog/tag/xhdata-d-808-modifications/ - I simply soldered the ends of the LW coil to a 3.5mm plug which is then inserted into the external antenna jack on the Tecsun

However, this only gives the Tecsun about the same sensitivity as when using its own non-optimal internal ferrite antenna. Can anyone advise me on how I could improve the LW sensitivity further? Would it help to include a variable capacitor to tune the receiver coil? Should I be able to expect the Tecsun to get the same sensitivity as a transistor radio with the same ferrite antenna or is there another reason why transistor radios perform better for LW?

I am a complete beginner so any advice would be appreciated!


Gary DeBock
 

Hello  jgriff670@...,
However, this only gives the Tecsun about the same sensitivity as when using its own non-optimal internal ferrite antenna. Can anyone advise me on how I could improve the LW sensitivity further?
For optimal Longwave reception on the Tecsun Pl-330, the best solution would be to replace the MW-optimized stock loopstick with an externally mounted Longwave-optimized loopstick that was designed for these DSP-chip Ultralight radios. The 7.5 inch (19cm) Longwave loopstick originally designed for the Tecsun PL-380 model would work great in the PL-330, just like it works great in the XHDATA D-808. This would be a superb solution for improved Longwave reception, but would require some technical skill to do the modification. Full details are in the articles linked below.
https://dreamcrafts.box.com/s/5d0pi85jfptgmrj4pd0jsmaybgb6gteh
https://dreamcrafts.box.com/s/xu7drqxg7epmljm4yu4579hcrin9em6p

Gary DeBock (in Puyallup, WA, USA)

  


-----Original Message-----
From: jgriff670@...
To: main@UltralightDX.groups.io
Sent: Sat, Jun 18, 2022 9:50 am
Subject: [UltralightDX] Ferrite antenna advice for LW

I have a Tecsun PL-330 which is known to be very deaf on LW. I also have a Roberts R993 (quite basic transistor radio) which has very good LW sensitivity. As a little project, I took the internal ferrite antenna for the Roberts and used it to make an external antenna for the Tecsun, following a procedure analogous to the one here https://swling.com/blog/tag/xhdata-d-808-modifications/ - I simply soldered the ends of the LW coil to a 3.5mm plug which is then inserted into the external antenna jack on the Tecsun

However, this only gives the Tecsun about the same sensitivity as when using its own non-optimal internal ferrite antenna. Can anyone advise me on how I could improve the LW sensitivity further? Would it help to include a variable capacitor to tune the receiver coil? Should I be able to expect the Tecsun to get the same sensitivity as a transistor radio with the same ferrite antenna or is there another reason why transistor radios perform better for LW?

I am a complete beginner so any advice would be appreciated!


Steve Ratzlaff
 

I'm not familiar with the Roberts R993 but I found it online--it doesn't say much about it. It's probably not a modern DSP radio such as the various Tecsun radios are (PL380, PL330, etc.). The DSP radios automatically peak the signal but can only do that for either MW or LF, not both. All stock Tecsun DSP radios have the internal ferrite rod coil optimized for MW, thus LF sensitivity is very poor as you've found. You can remove the rod and change the winding for much more inductance so it will tune LF, then it will have comparable LF sensitivity. But you can't have both MW and LF at the same time. Gary DeBock has published plans for putting a 7.5" external ferrite rod on these various DSP radios, and winding the coil for either MW or LF. That's a much larger rod than the stock rod (which is removed when the mod is done) and gives much greater MW or LF sensitivity.

I've done these external ferrite rod mods to several Tecsun DSP radios (and others such as Radiwow that are also DSP) both for MW and for LF. I've also compared a bunch of stock portable radios that have an LF band--the best ones for LF sensitivity I've found are the Sony 7600GR and an older Sangean ATS-818 (same as Radio Shack DX-391 or 392 with the cassette; the ATS-818CS also has the cassette).

73,

Steve

On 6/18/2022 9:50 AM, jgriff670@... wrote:
I have a Tecsun PL-330 which is known to be very deaf on LW. I also have a Roberts R993 (quite basic transistor radio) which has very good LW sensitivity. As a little project, I took the internal ferrite antenna for the Roberts and used it to make an external antenna for the Tecsun, following a procedure analogous to the one here https://swling.com/blog/tag/xhdata-d-808-modifications/ - I simply soldered the ends of the LW coil to a 3.5mm plug which is then inserted into the external antenna jack on the Tecsun

However, this only gives the Tecsun about the same sensitivity as when using its own non-optimal internal ferrite antenna. Can anyone advise me on how I could improve the LW sensitivity further? Would it help to include a variable capacitor to tune the receiver coil? Should I be able to expect the Tecsun to get the same sensitivity as a transistor radio with the same ferrite antenna or is there another reason why transistor radios perform better for LW?

I am a complete beginner so any advice would be appreciated!


Marc Coevoet
 

I remember Gary making very good antennas for am and lw for tecsun/silabs radios like the 310 or 380.  But they had a different number of turns (more for lw) to match the needed coil inductivity for am/lw.  So thats also why old radios like grundig have different coils ...  Unfortunately tecsun did not adapt for lw ...

Marc Coevoet

Op za 18 jun. 2022 20:13 schreef <jgriff670@...>:

I have a Tecsun PL-330 which is known to be very deaf on LW. I also have a Roberts R993 (quite basic transistor radio) which has very good LW sensitivity. As a little project, I took the internal ferrite antenna for the Roberts and used it to make an external antenna for the Tecsun, following a procedure analogous to the one here https://swling.com/blog/tag/xhdata-d-808-modifications/ - I simply soldered the ends of the LW coil to a 3.5mm plug which is then inserted into the external antenna jack on the Tecsun

However, this only gives the Tecsun about the same sensitivity as when using its own non-optimal internal ferrite antenna. Can anyone advise me on how I could improve the LW sensitivity further? Would it help to include a variable capacitor to tune the receiver coil? Should I be able to expect the Tecsun to get the same sensitivity as a transistor radio with the same ferrite antenna or is there another reason why transistor radios perform better for LW?

I am a complete beginner so any advice would be appreciated!


Gary DeBock
 

Thanks Marc and Steve,

Longwave-optimized loopstick design was a fascinating challenge, since no commercial manufacturer had ever included such a loopstick in any of their portables. It was really a "start from scratch" design effort.

The full details of the 2010 experimentation leading to the 7.5 inch (19cm) Longwave-optimized loopstick for the DSP Ultralights is posted at 
https://dreamcrafts.box.com/s/rmcd8wpt81pw1oobcl6om1pwhsqny0gd

73, Gary
    


-----Original Message-----
From: Marc Coevoet <sintsixtus@...>
To: main@ultralightdx.groups.io
Sent: Sat, Jun 18, 2022 12:08 pm
Subject: Re: [UltralightDX] Ferrite antenna advice for LW

I remember Gary making very good antennas for am and lw for tecsun/silabs radios like the 310 or 380.  But they had a different number of turns (more for lw) to match the needed coil inductivity for am/lw.  So thats also why old radios like grundig have different coils ...  Unfortunately tecsun did not adapt for lw ...

Marc Coevoet

Op za 18 jun. 2022 20:13 schreef <jgriff670@...>:
I have a Tecsun PL-330 which is known to be very deaf on LW. I also have a Roberts R993 (quite basic transistor radio) which has very good LW sensitivity. As a little project, I took the internal ferrite antenna for the Roberts and used it to make an external antenna for the Tecsun, following a procedure analogous to the one here https://swling.com/blog/tag/xhdata-d-808-modifications/ - I simply soldered the ends of the LW coil to a 3.5mm plug which is then inserted into the external antenna jack on the Tecsun

However, this only gives the Tecsun about the same sensitivity as when using its own non-optimal internal ferrite antenna. Can anyone advise me on how I could improve the LW sensitivity further? Would it help to include a variable capacitor to tune the receiver coil? Should I be able to expect the Tecsun to get the same sensitivity as a transistor radio with the same ferrite antenna or is there another reason why transistor radios perform better for LW?

I am a complete beginner so any advice would be appreciated!


Peter 1956
 

Hello all,
The Sony ICF-M780SL portable radio which featured in my 252 LW daytime reception from Ireland, is actually a DSP radio, which obviously works fine on LW.
I have several portable radios which work well on LW. Since the 1990s Roberts Radios are actually re-badged Sangean radios. I gave quite a few of these radios :)
older Roberts radios were made in Britain.
Peter
Blackpool UK


John
 
Edited

Thanks for your reply, I have read Gary's articles and I will definitely try this. I am curious as to why the external loopstick works with only a single coil - my understanding of traditional AM receivers is that they have a primary and a secondary coil which are coupled via the tap to the radio circuit. Do DSP radios work differently to analog radios in this respect? Many thanks


Michael.2E0IHW
 

John, older transistor radios have a low-impedance NPN (or PNP) RF amplifier and needed a low-impediance coupling coil on the ferrite.
Modern DSP radios have a high impedance FET RF amp in the IC, usually with auto-tuning of the high impedance ferrite winding.
If you use an exterior loopstick inductively coupled to the internal ferrite, it needs manual tuning with a variable capacitor. This is the
principle of the  excellent FSL series.

Michael

On 19/06/2022 11:15, John wrote:
Thanks for your reply, I have read your articles and I will definitely try this. I am curious as to why your loopstick works with only a single coil - my understanding of traditional AM receivers is that they have a primary and a secondary coil which are coupled via the tap to the radio circuit. Do DSP radios work differently to analog radios in this respect? Many thanks


Gary DeBock
 

Hi Again John,

<<<   I am curious as to why the external loopstick works with only a single coil - my understanding of traditional AM receivers is that they have a primary and a secondary coil which are coupled via the tap to the radio circuit. Do DSP radios work differently to analog radios in this respect? Many thanks   >>>

All of the original DSP Ultralight radios (Tecsun PL-310, PL-380, PL-360 etc.) had a loopstick design with a single coil, which matched the specifications of their internal (Silicon Labs) Si4734 DSP chips. These DSP chips were designed to operate with a single coil from 180-450 uH in inductance, although experimentally they worked very well with coils of greater inductance for improved Longwave reception. These DSP chips provided a huge breakthrough in Ultralight radio performance at the time (2008-2010), and were a primary reason why the Ultralight radio niche group exploded in popularity worldwide.

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

 


John
 

Thanks for all your help on this topic. I have ordered some Litz wire and a ferrite rod to make a LW optimised loopstick following Gary's procedure.