Date   

Re: Sangean HDR-14 UL HD AM/FM Radio - What do you think?

Michael Schuster
 

WFAS-AM (1230 KHz) in White Plains, NY - a low-power daytime station with almost no audience, inexplicably converted to IBOC "("HD Radio") digital-only MA3 mode on May 22. Perhaps Cumulus is testing the waters in a low-risk situation.

Their transmitter is about 18 miles from me as the crow flies.

Knowing this change was coming I benchmarked the useable signal on a few of AM-HD capable portables (Sangean HDR-14 and HDR-15, NiceTex "SPARC" SHD-TX2) in analog mode early last month, and then did the same after the conversion. In analog mode the audio was very staticky but as intelligible as any fringe area station. Of course the digitall audio is significantly more intelligible - at the cost of the artificial-treble expansion sibilance characteristic of HD-AM.

The problem is, even with all of the transmitter power invested solely into the digital signal, and unlike WWFD in Maryland, this particular station makes the worst-case scenario for an analog-to-IBOC conversion. In various parts of my house I can either hear ony digi-noise (i.e. the HD detector is not even triggered), otherwise there may be an HD "lock" but no audio, or still elsewhere the digital audio kicks in (and out) only after an extended period of buffering.

This is barefoot ... adding just about any externally-coupled loop or ferrite antenna makes a world of difference as one might suspect.

Tune in in 6 months or so for the post-mortem ...


Re: Sangean DT-800 vs Sihuadon R-108 vs CCRadio 2E

Michael Schuster
 

Some YT reviewers have noted the DT-800 to have a relatively high noise floor on AM. Perhaps what you are observing, explains where that comes from in that most YT reviewers do not use headphones for obvious reasons.
Of note the CC Pocket has the same issue but has a front-panel button to turn off the LCD display to eliminate that as a source of RF noise.
Curious why the designer of neither radio couldn;t simply shield things better.


Re: Recent FSL Antenna Experimentation

Marc Coevoet
 

Op 1/06/2021 om 08:29 schreef kevin asato:
A more generalized loop that would work better in a wide band scenario would look like a coil like this and is normally the throwaway antenna supplied with stereo receivers <https://www.amazon.com/Fancasee-Antenna-Connector-Stereo-Receiver/dp/B0793F5JWR>.

I have replaced the standard loop from a tuner with a self made loop, I measure for the value of INDUCTANCE, and make such a loop (mostly around 12µH).. One loop of 2 by 2 meters gives me enough inductance for most receivers/tuners. Of course, the signal can be "huge" ... And tuners differ, so that one can use the better AM tuners ...



Marc
--
The "Penguin" has arrived - and he's not going away - ever.
For former Apple users: Xubuntu.org (menu's up left)
For former Windows users: Lubuntu.org (menu's down left)


Re: Recent FSL Antenna Experimentation

kevin asato
 


[there are embedded links for illustration purposes rather than having everyone suffer with my artwork]

Schematically, the FSL and Terk resemble a tuned LC circuit.; the difference is that the Terk would be an air core inductor and the FSL would be ferrite. It is the tuned circuit which resonates to a particular frequency at the expense of "hearing" other frequencies. This is what makes it not feasible for use with an SDR and panoramic display which is a wideband function but excellent for DX work.

A more generalized loop that would work better in a wide band scenario would look like a coil like this and is normally the throwaway antenna supplied with stereo receivers. i would attach one conductor to the wire antenna and the other to ground/earth. Some alternate arrangement will have to be made to support the antenna connection to an SDR dongle. The coil in this usage is to couple the signal from the antenna wire onto the radio tuned front end/loopstick antenna. The particular resonance of the loop is of no real concern here although one can play with the number of turns or diameter of the loop for best coupling to the radio. 

No matter which approach you take, have fun and play with it to see what works for your situation. 

73,
kevin 
kc6pob

On Mon, May 31, 2021 at 6:35 PM kevin asato via groups.io <kc6pob=gmail.com@groups.io> wrote:
Well. yes. A FSL is supposed to increase selectivity over a very small frequency range to aid in finding that one station buried adjacent in frequency of a higher powered station. Not just the FSL but also air core loop antennas as Terk,Tecsun, and homebrew implementations as well. A wideband implementation defeats the purpose of enhancing selectivity. For SDR in which you are looking at a panorama display, you probably just want to couple to a basic wire antenna which is broadbanded and can be readily coupled (multi-turn wrapped?) to a radio receiver. After that you can couple to a loop antenna to peak the frequency of interest.
73,
kevin
kc6pob

On Mon, May 31, 2021 at 2:30 PM <robconboy@...> wrote:
 

 

I have determined that broadband FSL’s don’t work very well for broadband recording with an SDR to sift thru later, unless wound on a large amount of ferrite. A broadband winding on a small FSL might be useful for live dx using an SDR, to help identify a frequency to tune to. Furthermore, I have not yet explored broadband enhancement for a inductively coupled small portable, relying exclusively on the the portable’s selectivity. It would entail using a bias tee, power supply or battery, and an inductive coupler probe.

 

My testing used a Wellbrook ALA1530LN as a reference antenna and a Perseus receiver. Perseus has a true 50 Ohm resistive input.

The FSL broadband amplifier is a Wellbrook FLX1530LN which I think is the same amplifier as the reference but in a different package.

 

I used copper tape to prototype, using various widths, and tapped the amplifier in at various points to determine the best broadband windings.

 

4 turns of 1-1/2 inch wide flashing wound on a 49 rod 200 mm long FSL yielded signal amplitudes 10 dB below the reference antenna, while the QRN daytime noise floor was about 11 dB below the reference.

 

2 turns of 2-1/2 inch wide flashing wound on a 204 rod 600 mm long FSL (68 rods x3) yielded amplitudes 3 dB below reference, and the daytime noise floor was about 6 dB below reference, (while still above the radio’s own noise floor). I don’t know why the large FSL consistently is yielding better performance than the reference antenna. My guess is that directional nulls of the FSL are broader and deeper than the Wellbrook loop’s and therefore the FSL is intercepting less QRN from some directions.

 

This antenna has broadband and tuned outputs. The tuned portion has a variable selectivity control. 

 

It’s grossly impractical, heavy and the cost of materials was more expensive than I will admit, even here, but its performance is nothing short of amazing.  First off, the field around this antenna is immense. It begins enhancing reception of a portable within about 6 feet.    Selectivity is adjustable. The narrower the selectivity, the greater the sensitivity. Tuning for dx is a balance between bandwidth, sensitivity and offset. Those of us with experience dx’ing with an old Hammarlund that has a regenerative selectivity control should remember what this is like.

 

The ferrite sleeve is 24 inches long and 9 inches diameter and made from 204 eight inch ferrite rods mounted on the outside of a 8-inch i.d. PVC pipe.  There is a 2-rod-width gap along the length of the sleeve that serves a dual purpose. It’s where the coil connections are made, as the electronics are inside the pipe. It also creates a gap to cut down magnetic coupling between conductors that run along the length of the sleeve. Without the gap, the sleeve becomes a toroidal core. The gap runs along the bottom of the sleeve for symmetry.

 

BTW, the 200mm by 10mm ferrite rods were still available on eBay last I looked, from a supplier in China. The specs aren’t given which is probably why they they haven’t been discovered by the dx community (as far as I know), but they appear to be mix 61. 

 

I bought 5, to check their suitability. After some testing and measurement, I was able to determine their permeability is above 100. So I bought 20 more, then 50, then 200.  Mix 61 is commonly used for AM loopstick antennas.

 

Tuned coil: 12 turns 1100/48 Litz, 230 uH, Centered on ferrite sleeve.

 

Capacitor:  20-400 pF, semi- logarithmic taper, 3-turn vernier shaft. This is mounted in the center of the ferrite sleeve (inside it) at the same depth as the coil.  This location was chosen after experimentation. I noticed that a small portable (Tecsun PL-330) placed inside the ferrite sleeve (before winding any coils) had greatly attenuated reception at some spots inside the pipe. So I wound a sniffer probe on a rod and connected it to my Perseus. There is a deep broadband null along the center axis that is greatest halfway in. I chose this spot for the tuning capacitor. The shaft is connected to an acrylic extension shaft with an insulated coupler. The coil/cap combination tunes from 525 to about 1850 kHz. Details on mounting come later.

 

The tuning knob is a dual concentric 1:1 and 40:1 vernier from Ukraine I bought on eBay. When combined with the vernier drive on the capacitor, it takes 120 turns of the inner knob to fully open/close the capacitor. The outer knob takes 3 turns. This makes pinpoint tuning at narrow bandwidths easy. Unfortunately there is some slop in this vernier when reversing rotation. It takes about 1/10 rotation before the rotor plates move. It’s inconsequential with such an extreme vernier ratio, but with a 1:1 shaft capacitor (40:1 vernier instead of 120:1) the slop was intolerable.

 

The pickup coil has 7 uH, is two widely spaced turns of 1100/48 Litz. The pickup coil feeds a step down transformer. This pickup coil is located 4 inches from one end of the ferrite sleeve. 

 

Step Down transformer: BN-73-202 core, 

Primary: 15 turns 64/46 Litz

Secondary: 3 turns 64/46 Litz.

 

The purpose of this transformer ratio is so that the pickup coil places a very light load on the tuned circuit. It also serves as a balun between the pickup and the amplifier. This is critical.

 

From the transformer it goes to a Mini-Circuits low noise amplifier model ZFL-500LN with a 50 Ohm input. This amplifier, due to the mismatch introduced by the transformer, places a 1250 Ohm load on the pickup coil and the amplifier’s effective gain is reduced to about 16 dB from 30 dB

 

Amplifier output goes to a Mini-Circuits signal splitter which reduces the gain by another 3 dB while isolating the feedback circuit from any connected radios.

 

Port one of the splitter goes through a 6 dB attenuator to a Mini-Circuits bias tee for powering the amplifier. This attenuator reduces the possibility of overloading the front end of a radio.

 

The RF+DC port of the bias tee goes to a BNC jack to connect a radio (via an external bias tee). The amplifier gain here is now about 6 dB.  

 

Port 2 of the signal splitter goes to a 10 dB attenuator.  This makes about 3 dB of gain available for feedback.

 

The output of the attenuator goes to a Bourns 10-turn 500 Ohm potentiometer. 

 

The output from the potentiometer goes through a switch to the feedback coil.

 

Between the switch and the feedback coil is a common mode choke balun: 5 bifilar turns around a small mix 75 toroid

 

In series with the feedback coil is 100 Ohms in parallel with 1330 pF. This makes the feedback slightly favor higher frequencies. This high pass filter makes potentiometer feedback adjustment less touchy when changing frequencies.

 

Feedback coil: 1-turn of 1100/48 Litz wire located 4 inches from the end of the ferrite sleeve opposite the pickup coil. Choosing Litz wire here might be complementary to the high pass filter but may yield no advantage over common wire..

 

Broadband  pickup coil:  Two turns of 2-1/2 inch wide copper flashing. They are wound on opposite sides of the tuning coil. 

 

This broadband coil goes through a DPST switch to a Wellbrook FLX1530LN low impedance loop antenna amplifier. The switch is necessary or else the broadband loop behaves like a partially shorted turn when using the the tuned portion of the antenna.

 

The output of the Wellbrook amplifier goes to a BNC jack.

 

The entire assembly is housed in a Rubbermaid trashcan liner.

I used 12 inch and 8 inch diameter wooden discs to center the antenna in the liner at the control panel end. The 12 inch disc fits into the liner, the 8 inch disc fits into the pipe, and the discs are glued together. The electronics are mounted on the outside of a 4 inch diameter, 11 inch tall plastic jar. The jar is mounted in the 8 inch wooden disc. The jar’s threads are lined with teflon tape. The 8 inch disc is cut with a 4 inch hole saw. The jar is mounted in the 4 inch hole using paste epoxy. This jar extends halfway down the center of the pipe. The teflon tape makes it so the jar can be unscrewed. The capacitor is mounted on the outside bottom of the jar, level with the tuned coil. Its shaft runs trough the inside of the jar to the vernier knob outside of the assembly. 

 

I built up the opposite end of the antenna with 2 inch wide strips of neoprene rubber to center it into the liner. 

 

Three modes of operation: 

 

Active tuned antenna with variable selectivity control, powered through a bias tee such as a Wellbrook antenna interface. Tune-able range 525 kHz to 1.85 MHz.  Measured narrowest possible (stable) -3 dB bandwidth @ 1750 kHz is about 80 Hz, making maximum possible Q about 22000 before oscillation.  In use, Q is dialed lower than this because a radio is not a subwoofer. 

 

The other mode is a Broadband antenna with it’s own separate coil and Wellbrook loop amplifier. This is usable up into the shortwave bands but performance gradually begins to degrade above about 2 MHz.

 

Passive mode, amplifiers unpowered. A tuned FSL that is proximity coupled to any nearby radio that has an internal loop antenna. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Re: Kchibo D96L portable radio.

Paul Blundell
 

It sounds like a display issue if this changes but it stays on the right station. I find these CCR to be a mixed bag.

Paul

On Tue, 1 Jun 2021, 07:41 Jerry H. Neves via groups.io, <jhneves7=aol.com@groups.io> wrote:

Hello to all members. Have had the above radio for a few years. Always worked fine. Also have always had a heck of a time trying to figure out how to properly operate this radio as the manual is all in Chinese!!! Yesterday went to use radio and on AM band, i.e. Broadcast band, when I tune to a station such as KGO on 810 kHz, after a few minutes the display will step down in frequency to 768 kHz, BUT It’s still hearing the program on 810??? On a station on 1080 kHz, KSCO the same problem occurs, after a few minutes station steps down to 1024 kHz, again signal from KSCO remains on!!! Any ideas?? This only happens on Broadcastband!   I tried a reset to no avail. Real weird. Also how to get the instruction manual in English? Also how to open up this radio??Any help will be appreciated.Thanks.
Jerry Neves

 


Re: Recent FSL Antenna Experimentation

kevin asato
 

Well. yes. A FSL is supposed to increase selectivity over a very small frequency range to aid in finding that one station buried adjacent in frequency of a higher powered station. Not just the FSL but also air core loop antennas as Terk,Tecsun, and homebrew implementations as well. A wideband implementation defeats the purpose of enhancing selectivity. For SDR in which you are looking at a panorama display, you probably just want to couple to a basic wire antenna which is broadbanded and can be readily coupled (multi-turn wrapped?) to a radio receiver. After that you can couple to a loop antenna to peak the frequency of interest.
73,
kevin
kc6pob

On Mon, May 31, 2021 at 2:30 PM <robconboy@...> wrote:
 

 

I have determined that broadband FSL’s don’t work very well for broadband recording with an SDR to sift thru later, unless wound on a large amount of ferrite. A broadband winding on a small FSL might be useful for live dx using an SDR, to help identify a frequency to tune to. Furthermore, I have not yet explored broadband enhancement for a inductively coupled small portable, relying exclusively on the the portable’s selectivity. It would entail using a bias tee, power supply or battery, and an inductive coupler probe.

 

My testing used a Wellbrook ALA1530LN as a reference antenna and a Perseus receiver. Perseus has a true 50 Ohm resistive input.

The FSL broadband amplifier is a Wellbrook FLX1530LN which I think is the same amplifier as the reference but in a different package.

 

I used copper tape to prototype, using various widths, and tapped the amplifier in at various points to determine the best broadband windings.

 

4 turns of 1-1/2 inch wide flashing wound on a 49 rod 200 mm long FSL yielded signal amplitudes 10 dB below the reference antenna, while the QRN daytime noise floor was about 11 dB below the reference.

 

2 turns of 2-1/2 inch wide flashing wound on a 204 rod 600 mm long FSL (68 rods x3) yielded amplitudes 3 dB below reference, and the daytime noise floor was about 6 dB below reference, (while still above the radio’s own noise floor). I don’t know why the large FSL consistently is yielding better performance than the reference antenna. My guess is that directional nulls of the FSL are broader and deeper than the Wellbrook loop’s and therefore the FSL is intercepting less QRN from some directions.

 

This antenna has broadband and tuned outputs. The tuned portion has a variable selectivity control. 

 

It’s grossly impractical, heavy and the cost of materials was more expensive than I will admit, even here, but its performance is nothing short of amazing.  First off, the field around this antenna is immense. It begins enhancing reception of a portable within about 6 feet.    Selectivity is adjustable. The narrower the selectivity, the greater the sensitivity. Tuning for dx is a balance between bandwidth, sensitivity and offset. Those of us with experience dx’ing with an old Hammarlund that has a regenerative selectivity control should remember what this is like.

 

The ferrite sleeve is 24 inches long and 9 inches diameter and made from 204 eight inch ferrite rods mounted on the outside of a 8-inch i.d. PVC pipe.  There is a 2-rod-width gap along the length of the sleeve that serves a dual purpose. It’s where the coil connections are made, as the electronics are inside the pipe. It also creates a gap to cut down magnetic coupling between conductors that run along the length of the sleeve. Without the gap, the sleeve becomes a toroidal core. The gap runs along the bottom of the sleeve for symmetry.

 

BTW, the 200mm by 10mm ferrite rods were still available on eBay last I looked, from a supplier in China. The specs aren’t given which is probably why they they haven’t been discovered by the dx community (as far as I know), but they appear to be mix 61. 

 

I bought 5, to check their suitability. After some testing and measurement, I was able to determine their permeability is above 100. So I bought 20 more, then 50, then 200.  Mix 61 is commonly used for AM loopstick antennas.

 

Tuned coil: 12 turns 1100/48 Litz, 230 uH, Centered on ferrite sleeve.

 

Capacitor:  20-400 pF, semi- logarithmic taper, 3-turn vernier shaft. This is mounted in the center of the ferrite sleeve (inside it) at the same depth as the coil.  This location was chosen after experimentation. I noticed that a small portable (Tecsun PL-330) placed inside the ferrite sleeve (before winding any coils) had greatly attenuated reception at some spots inside the pipe. So I wound a sniffer probe on a rod and connected it to my Perseus. There is a deep broadband null along the center axis that is greatest halfway in. I chose this spot for the tuning capacitor. The shaft is connected to an acrylic extension shaft with an insulated coupler. The coil/cap combination tunes from 525 to about 1850 kHz. Details on mounting come later.

 

The tuning knob is a dual concentric 1:1 and 40:1 vernier from Ukraine I bought on eBay. When combined with the vernier drive on the capacitor, it takes 120 turns of the inner knob to fully open/close the capacitor. The outer knob takes 3 turns. This makes pinpoint tuning at narrow bandwidths easy. Unfortunately there is some slop in this vernier when reversing rotation. It takes about 1/10 rotation before the rotor plates move. It’s inconsequential with such an extreme vernier ratio, but with a 1:1 shaft capacitor (40:1 vernier instead of 120:1) the slop was intolerable.

 

The pickup coil has 7 uH, is two widely spaced turns of 1100/48 Litz. The pickup coil feeds a step down transformer. This pickup coil is located 4 inches from one end of the ferrite sleeve. 

 

Step Down transformer: BN-73-202 core, 

Primary: 15 turns 64/46 Litz

Secondary: 3 turns 64/46 Litz.

 

The purpose of this transformer ratio is so that the pickup coil places a very light load on the tuned circuit. It also serves as a balun between the pickup and the amplifier. This is critical.

 

From the transformer it goes to a Mini-Circuits low noise amplifier model ZFL-500LN with a 50 Ohm input. This amplifier, due to the mismatch introduced by the transformer, places a 1250 Ohm load on the pickup coil and the amplifier’s effective gain is reduced to about 16 dB from 30 dB

 

Amplifier output goes to a Mini-Circuits signal splitter which reduces the gain by another 3 dB while isolating the feedback circuit from any connected radios.

 

Port one of the splitter goes through a 6 dB attenuator to a Mini-Circuits bias tee for powering the amplifier. This attenuator reduces the possibility of overloading the front end of a radio.

 

The RF+DC port of the bias tee goes to a BNC jack to connect a radio (via an external bias tee). The amplifier gain here is now about 6 dB.  

 

Port 2 of the signal splitter goes to a 10 dB attenuator.  This makes about 3 dB of gain available for feedback.

 

The output of the attenuator goes to a Bourns 10-turn 500 Ohm potentiometer. 

 

The output from the potentiometer goes through a switch to the feedback coil.

 

Between the switch and the feedback coil is a common mode choke balun: 5 bifilar turns around a small mix 75 toroid

 

In series with the feedback coil is 100 Ohms in parallel with 1330 pF. This makes the feedback slightly favor higher frequencies. This high pass filter makes potentiometer feedback adjustment less touchy when changing frequencies.

 

Feedback coil: 1-turn of 1100/48 Litz wire located 4 inches from the end of the ferrite sleeve opposite the pickup coil. Choosing Litz wire here might be complementary to the high pass filter but may yield no advantage over common wire..

 

Broadband  pickup coil:  Two turns of 2-1/2 inch wide copper flashing. They are wound on opposite sides of the tuning coil. 

 

This broadband coil goes through a DPST switch to a Wellbrook FLX1530LN low impedance loop antenna amplifier. The switch is necessary or else the broadband loop behaves like a partially shorted turn when using the the tuned portion of the antenna.

 

The output of the Wellbrook amplifier goes to a BNC jack.

 

The entire assembly is housed in a Rubbermaid trashcan liner.

I used 12 inch and 8 inch diameter wooden discs to center the antenna in the liner at the control panel end. The 12 inch disc fits into the liner, the 8 inch disc fits into the pipe, and the discs are glued together. The electronics are mounted on the outside of a 4 inch diameter, 11 inch tall plastic jar. The jar is mounted in the 8 inch wooden disc. The jar’s threads are lined with teflon tape. The 8 inch disc is cut with a 4 inch hole saw. The jar is mounted in the 4 inch hole using paste epoxy. This jar extends halfway down the center of the pipe. The teflon tape makes it so the jar can be unscrewed. The capacitor is mounted on the outside bottom of the jar, level with the tuned coil. Its shaft runs trough the inside of the jar to the vernier knob outside of the assembly. 

 

I built up the opposite end of the antenna with 2 inch wide strips of neoprene rubber to center it into the liner. 

 

Three modes of operation: 

 

Active tuned antenna with variable selectivity control, powered through a bias tee such as a Wellbrook antenna interface. Tune-able range 525 kHz to 1.85 MHz.  Measured narrowest possible (stable) -3 dB bandwidth @ 1750 kHz is about 80 Hz, making maximum possible Q about 22000 before oscillation.  In use, Q is dialed lower than this because a radio is not a subwoofer. 

 

The other mode is a Broadband antenna with it’s own separate coil and Wellbrook loop amplifier. This is usable up into the shortwave bands but performance gradually begins to degrade above about 2 MHz.

 

Passive mode, amplifiers unpowered. A tuned FSL that is proximity coupled to any nearby radio that has an internal loop antenna. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Re: FM Translators - Why?

Paul Blundell
 

Here (Tasmania) they serve two main purposes:
- To provide coverage in areas the main transmitter does not reach. As an example, our main transmitter site for FM radio is Mt Barrow, this provides a great signal across a wide area but as our CBD is in a valley, due to this they have translators in the CBD for our two commercial FM stations.
- In some rural areas, they have a translator of the local AM station to also provide a signal for those that don't have an AM radio.

Paul

On Tue, Jun 1, 2021 at 4:57 AM Johnny via groups.io <jlochey=yahoo.com@groups.io> wrote:
Hi all,

Why do FM Translators exist?

The closest I can tell is that they exist to give an AM station a "Market Presence" in the FM band at a local level.

Is that pretty much it?  Or am I missing it?

Also, I have not come across an FM Booster yet, but apparently these exist (in the US at least).


Johnny



--
Paul


Re: Recent FSL Antenna Experimentation

Robert Conboy
 

The font size was unintentional as was the big empty space;  artifacts from copy/paste from notepad. Sorry.


Kchibo D96L portable radio.

Jerry H. Neves
 

Hello to all members. Have had the above radio for a few years. Always worked fine. Also have always had a heck of a time trying to figure out how to properly operate this radio as the manual is all in Chinese!!! Yesterday went to use radio and on AM band, i.e. Broadcast band, when I tune to a station such as KGO on 810 kHz, after a few minutes the display will step down in frequency to 768 kHz, BUT It’s still hearing the program on 810??? On a station on 1080 kHz, KSCO the same problem occurs, after a few minutes station steps down to 1024 kHz, again signal from KSCO remains on!!! Any ideas?? This only happens on Broadcastband!   I tried a reset to no avail. Real weird. Also how to get the instruction manual in English? Also how to open up this radio??Any help will be appreciated.Thanks.
Jerry Neves

 


Re: Recent FSL Antenna Experimentation

Robert Conboy
 

 

 

I have determined that broadband FSL’s don’t work very well for broadband recording with an SDR to sift thru later, unless wound on a large amount of ferrite. A broadband winding on a small FSL might be useful for live dx using an SDR, to help identify a frequency to tune to. Furthermore, I have not yet explored broadband enhancement for a inductively coupled small portable, relying exclusively on the the portable’s selectivity. It would entail using a bias tee, power supply or battery, and an inductive coupler probe.

 

My testing used a Wellbrook ALA1530LN as a reference antenna and a Perseus receiver. Perseus has a true 50 Ohm resistive input.

The FSL broadband amplifier is a Wellbrook FLX1530LN which I think is the same amplifier as the reference but in a different package.

 

I used copper tape to prototype, using various widths, and tapped the amplifier in at various points to determine the best broadband windings.

 

4 turns of 1-1/2 inch wide flashing wound on a 49 rod 200 mm long FSL yielded signal amplitudes 10 dB below the reference antenna, while the QRN daytime noise floor was about 11 dB below the reference.

 

2 turns of 2-1/2 inch wide flashing wound on a 204 rod 600 mm long FSL (68 rods x3) yielded amplitudes 3 dB below reference, and the daytime noise floor was about 6 dB below reference, (while still above the radio’s own noise floor). I don’t know why the large FSL consistently is yielding better performance than the reference antenna. My guess is that directional nulls of the FSL are broader and deeper than the Wellbrook loop’s and therefore the FSL is intercepting less QRN from some directions.

 

This antenna has broadband and tuned outputs. The tuned portion has a variable selectivity control. 

 

It’s grossly impractical, heavy and the cost of materials was more expensive than I will admit, even here, but its performance is nothing short of amazing.  First off, the field around this antenna is immense. It begins enhancing reception of a portable within about 6 feet.    Selectivity is adjustable. The narrower the selectivity, the greater the sensitivity. Tuning for dx is a balance between bandwidth, sensitivity and offset. Those of us with experience dx’ing with an old Hammarlund that has a regenerative selectivity control should remember what this is like.

 

The ferrite sleeve is 24 inches long and 9 inches diameter and made from 204 eight inch ferrite rods mounted on the outside of a 8-inch i.d. PVC pipe.  There is a 2-rod-width gap along the length of the sleeve that serves a dual purpose. It’s where the coil connections are made, as the electronics are inside the pipe. It also creates a gap to cut down magnetic coupling between conductors that run along the length of the sleeve. Without the gap, the sleeve becomes a toroidal core. The gap runs along the bottom of the sleeve for symmetry.

 

BTW, the 200mm by 10mm ferrite rods were still available on eBay last I looked, from a supplier in China. The specs aren’t given which is probably why they they haven’t been discovered by the dx community (as far as I know), but they appear to be mix 61. 

 

I bought 5, to check their suitability. After some testing and measurement, I was able to determine their permeability is above 100. So I bought 20 more, then 50, then 200.  Mix 61 is commonly used for AM loopstick antennas.

 

Tuned coil: 12 turns 1100/48 Litz, 230 uH, Centered on ferrite sleeve.

 

Capacitor:  20-400 pF, semi- logarithmic taper, 3-turn vernier shaft. This is mounted in the center of the ferrite sleeve (inside it) at the same depth as the coil.  This location was chosen after experimentation. I noticed that a small portable (Tecsun PL-330) placed inside the ferrite sleeve (before winding any coils) had greatly attenuated reception at some spots inside the pipe. So I wound a sniffer probe on a rod and connected it to my Perseus. There is a deep broadband null along the center axis that is greatest halfway in. I chose this spot for the tuning capacitor. The shaft is connected to an acrylic extension shaft with an insulated coupler. The coil/cap combination tunes from 525 to about 1850 kHz. Details on mounting come later.

 

The tuning knob is a dual concentric 1:1 and 40:1 vernier from Ukraine I bought on eBay. When combined with the vernier drive on the capacitor, it takes 120 turns of the inner knob to fully open/close the capacitor. The outer knob takes 3 turns. This makes pinpoint tuning at narrow bandwidths easy. Unfortunately there is some slop in this vernier when reversing rotation. It takes about 1/10 rotation before the rotor plates move. It’s inconsequential with such an extreme vernier ratio, but with a 1:1 shaft capacitor (40:1 vernier instead of 120:1) the slop was intolerable.

 

The pickup coil has 7 uH, is two widely spaced turns of 1100/48 Litz. The pickup coil feeds a step down transformer. This pickup coil is located 4 inches from one end of the ferrite sleeve. 

 

Step Down transformer: BN-73-202 core, 

Primary: 15 turns 64/46 Litz

Secondary: 3 turns 64/46 Litz.

 

The purpose of this transformer ratio is so that the pickup coil places a very light load on the tuned circuit. It also serves as a balun between the pickup and the amplifier. This is critical.

 

From the transformer it goes to a Mini-Circuits low noise amplifier model ZFL-500LN with a 50 Ohm input. This amplifier, due to the mismatch introduced by the transformer, places a 1250 Ohm load on the pickup coil and the amplifier’s effective gain is reduced to about 16 dB from 30 dB

 

Amplifier output goes to a Mini-Circuits signal splitter which reduces the gain by another 3 dB while isolating the feedback circuit from any connected radios.

 

Port one of the splitter goes through a 6 dB attenuator to a Mini-Circuits bias tee for powering the amplifier. This attenuator reduces the possibility of overloading the front end of a radio.

 

The RF+DC port of the bias tee goes to a BNC jack to connect a radio (via an external bias tee). The amplifier gain here is now about 6 dB.  

 

Port 2 of the signal splitter goes to a 10 dB attenuator.  This makes about 3 dB of gain available for feedback.

 

The output of the attenuator goes to a Bourns 10-turn 500 Ohm potentiometer. 

 

The output from the potentiometer goes through a switch to the feedback coil.

 

Between the switch and the feedback coil is a common mode choke balun: 5 bifilar turns around a small mix 75 toroid

 

In series with the feedback coil is 100 Ohms in parallel with 1330 pF. This makes the feedback slightly favor higher frequencies. This high pass filter makes potentiometer feedback adjustment less touchy when changing frequencies.

 

Feedback coil: 1-turn of 1100/48 Litz wire located 4 inches from the end of the ferrite sleeve opposite the pickup coil. Choosing Litz wire here might be complementary to the high pass filter but may yield no advantage over common wire..

 

Broadband  pickup coil:  Two turns of 2-1/2 inch wide copper flashing. They are wound on opposite sides of the tuning coil. 

 

This broadband coil goes through a DPST switch to a Wellbrook FLX1530LN low impedance loop antenna amplifier. The switch is necessary or else the broadband loop behaves like a partially shorted turn when using the the tuned portion of the antenna.

 

The output of the Wellbrook amplifier goes to a BNC jack.

 

The entire assembly is housed in a Rubbermaid trashcan liner.

I used 12 inch and 8 inch diameter wooden discs to center the antenna in the liner at the control panel end. The 12 inch disc fits into the liner, the 8 inch disc fits into the pipe, and the discs are glued together. The electronics are mounted on the outside of a 4 inch diameter, 11 inch tall plastic jar. The jar is mounted in the 8 inch wooden disc. The jar’s threads are lined with teflon tape. The 8 inch disc is cut with a 4 inch hole saw. The jar is mounted in the 4 inch hole using paste epoxy. This jar extends halfway down the center of the pipe. The teflon tape makes it so the jar can be unscrewed. The capacitor is mounted on the outside bottom of the jar, level with the tuned coil. Its shaft runs trough the inside of the jar to the vernier knob outside of the assembly. 

 

I built up the opposite end of the antenna with 2 inch wide strips of neoprene rubber to center it into the liner. 

 

Three modes of operation: 

 

Active tuned antenna with variable selectivity control, powered through a bias tee such as a Wellbrook antenna interface. Tune-able range 525 kHz to 1.85 MHz.  Measured narrowest possible (stable) -3 dB bandwidth @ 1750 kHz is about 80 Hz, making maximum possible Q about 22000 before oscillation.  In use, Q is dialed lower than this because a radio is not a subwoofer. 

 

The other mode is a Broadband antenna with it’s own separate coil and Wellbrook loop amplifier. This is usable up into the shortwave bands but performance gradually begins to degrade above about 2 MHz.

 

Passive mode, amplifiers unpowered. A tuned FSL that is proximity coupled to any nearby radio that has an internal loop antenna. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Re: FM Translators - Why?

Peter Laws
 

On Mon, May 31, 2021 at 1:57 PM Johnny via groups.io
<jlochey=yahoo.com@groups.io> wrote:

Hi all,

Why do FM Translators exist?
Because the FCC says that this is how to "revitalize" AM broadcasting.

¯\_(ツ)_/¯

--
Peter Laws | N5UWY | plaws plaws net | Travel by Train!


FM Translators - Why?

Johnny <jlochey@...>
 

Hi all,

Why do FM Translators exist?

The closest I can tell is that they exist to give an AM station a "Market Presence" in the FM band at a local level.

Is that pretty much it?  Or am I missing it?

Also, I have not come across an FM Booster yet, but apparently these exist (in the US at least).


Johnny


Re: My best FM DX'ing catch so far!!!

Johnny <jlochey@...>
 

Hi John,

I was using my R-108.

A GREAT radio!


Johnny


Re: Recent FSL Antenna Experimentation

Gary DeBock
 

On Mon, May 31, 2021 at 09:18 AM, <robconboy@...> wrote:
Well, I just unsuccessfully attempted to post a lengthy reply full of technical details but it would not post, or needs to be reviewed by a moderator or something...
Hi Rob,

Moderator approval isn't needed for lengthy messages, so you should be good to go. It's only set up by Groups.io for the first message sent by a new member, in order to avoid spam postings.

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


Re: Recent FSL Antenna Experimentation

Grant
 

hoping that you get it published, really want to see it - thanks, Grant


Re: Recent FSL Antenna Experimentation

Robert Conboy
 

I will try again later. The post was cobbled together from my various build notes which I still have.


Re: Recent FSL Antenna Experimentation

Phil Pasteur
 

That is too bad. I would really like to see the information. Maybe one of the mods can help you with it. Hopefully the post was saved somewhere.


Re: Recent FSL Antenna Experimentation

Robert Conboy
 

Well, I just unsuccessfully attempted to post a lengthy reply full of technical details but it would not post, or needs to be reviewed by a moderator or something...


Long Term DX Project - 29/05/2021

Paul Blundell
 

Date: 29/05/2021
Time: 4:15pm
Location: Home, Launceston Tasmania.
Radio: AR-1733 / 3” FSL
Notes: A late afternoon session at home, using my AR-1733 and 3” FSL. Signals were a real mix with only two of the 50kw big guns hitting good signal levels. Even 3GG on 531kHz struggled a bit. Both the HPON stations were only logged at poor signal levels.

 

Long Term DX Project Loggings:

FREQ

CALLSIGN

LOGGED

Area Served

Purpose

Power

531

3GG

AVERAGE

Warragul

Commercial

5k

549

2CR

POOR

Cumnock

National

50k

594

3WV

AVERAGE

Horsham

National

50k

621

3RN

GOOD

Melbourne

National

50k

774

3LO

GOOD

Melbourne

National

50k

1053

2CA

UNLOGGED

Canberra

Commercial

5k

1179

3RPH

UNLOGGED

Melbourne

Community

5k

1341

HPON GEELONG

POOR

Geelong

HPON

5k

1422

HPON MELBOURNE

POOR

Melbourne

HPON

5k

1503

3KND

UNLOGGED

Melbourne

Community

5k


Re: Recent FSL Antenna Experimentation

Nick Hall-Patch
 

Have you published details of your broadband amplified FSL, Rob?  

I don't know if others have tried the copper flashing for a pickup winding.   How different is its response from using a simple loop of wire to transfer the FSL's signal to the amplifier?   And, is the amplifier itself a unique design?

Thanks.

Nick

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