I have the predecessor unit and it is just a two winding capacitor (direction) induction motor with a gear train. The digital display seems to be counting AC cycles. A strong wind (or in my case power mains failure) can push a 12' yagi out of alignment. In short it is not like a CDR type with an internal wire wound resistor measuring direction.
Sort of a shame the WW2 400 Hz selsyns are no longer "inexpensive" although a PM magnet, an Arduino flux compass, and some hot glue will probably replace a selsyn and all the analog hardware to remotely read out azimuth position in degrees.
|
Re: File upload: Rotable FLAG-antenna
What about this diamond shape antenna, would it better? I have a Wellbrook FLG100 Wellbrok module amplifier. I dont know if the growning flag will be better.
?
?
https://swling.com/blog/tag/small-unidirectional-loop-antenna-sula/
?
https://swling.net/viewtopic.php?t=55
|
I just saw this RCA rotor on sale, I don't know that is is precise enough, because it is programmable for every 10 degrees. I haven't read the manual
far enough to see if you can precisely set direction to null your noise sources or if you can fool it to ever 5degrees by only turning 180 degrees.
It is $89 on sale with rebate.? $14 shipping, at least to me in Fl.
?
Here's the manual,
?
???????????????? Mikek
?
?
?
?
|
Re: Entry Level SDR recommendations
Maybe is the power supply causing this problem. I have tried to feed with a well filtered external USB adptor but the problem persit. I forgot also I purchased a USB isolator but not results at all . I have several 31-43 mix toroids and big 43 ferrite clamps.? As I said before the cable is not too long I will purchase extra cables in order to wind the toroids.
|
Re: Entry Level SDR recommendations
I agree with Simon, and he raises a valid point that you can use smaller diameter cables, but sometimes things like moulded USB connectors prevent their use, and you have to resort to larger cores.
?
Regards,
?
Martin
?
On Sun, Feb 23, 2025 at 06:47 PM, Simon wrote:
However you do NOT need to use ft240/(31/43) cores.. Ft240 is the size of core. As your cable is not rg213 ie thick, one can use cheaper smaller diameter cores..just as long as one can get the required turns though and are of same spec. Ie type 31/43 etc.
|
Re: Entry Level SDR recommendations
If the amplifier is genuinely running in class A (which I doubt) it should not generate any RFI.
?
It is difficult to tell from the video if the interference varies in unison with the audio, but the Spectrum Analyser plots suggest a single switching frequency and harmonics, which to me suggests a power supply issue.
?
I believe the noise is most likely being introduced from the USB port, or whatever is powering the amplifier, so personally I would concentrate on that rather than the amplifier, as I think you have tried just about every usual technique of RFI suppression on the PCB itself.
?
I'd suggest trying a screened PSU cable, with good decoupling of the supply cores at each end, and a decent bond to ground at the PC end.
?
Regards,
?
Martin
?
On Sun, Feb 23, 2025 at 05:17 PM, enriqueeeeee2001 wrote:
Trust speakers, it has a class A amplifier and radiates a lot s of RFI
|
Re: Entry Level SDR recommendations
?Hi
Just to add to Martin’s comments..
G3TZQ chart is very helpful.( ie the Bible on cm chokes.) But was primarily designed for common mode chokes on Tx cables going to antennas. They are the same for rx/ rfi chokes so will work for you.
However you do NOT need to use ft240/(31/43) cores.. Ft240 is the size of core. As your cable is not rg213 ie thick, one can use cheaper smaller diameter cores..just as long as one can get the required turns though and are of same spec. Ie type 31/43 etc.
Sorry if you already knew this.
Simon
|
Re: Entry Level SDR recommendations
Ideally, you need to tailor the core material and number of turns to work at the most problematic frequency.
?
Just one pass of a cable through a single small clip-on core will not do much at short wave frequencies (IT equipment use them to reduce emissions on frequencies >30MHz), and you would need about 30 to 40 of them to be effective at HF.
?
Winding multiple turns through a larger core is much more effective and economical to construct.
?
Steve, G3TXQ (SK), produced some handy charts, that provide good guidance for common mode choke construction.
?
?
You don't have to use exactly the same parameters, but it does nicely demonstrate what is required to stand a chance of making a difference.
?
Regards,
?
Martin
|
Re: Entry Level SDR recommendations
You night be better off with mix 31..
On Sunday, February 23, 2025, 12:09 PM, enriqueeeeee2001 via groups.io <enriqueeeeee2001@...> wrote: Thanks , yes? only have a ferrite bead because the cable is too short between the Pc and the speakers. I will try with a big toroid 43 or 71 ferrite material. I will use longer wires. I hope this will fix the RFI interferences.
|
Re: Entry Level SDR recommendations
Thanks , yes? only have a ferrite bead because the cable is too short between the Pc and the speakers. I will try with a big toroid 43 or 71 ferrite material. I will use longer wires. I hope this will fix the RFI interferences.
|
Re: Entry Level SDR recommendations
Class D and E are switchers and to be avoided.? I'm guessing the RFI you are experiencing is conducted on the audio cables from the PC, itself.? Once energy is present on the cables, they become antennas to radiate that energy.? Try installing several clamp-on ferrites on all the cables.? Make up to three turns through each clamp-on ferrite.? No more.? Install them next to the PC and next to the speakers.?
Dave - W?LEV
On Sun, Feb 23, 2025 at 5:17?PM enriqueeeeee2001 via <enriqueeeeee2001= [email protected]> wrote:
I have only a SDR a Winradio Excalibur with a Wellbrook antenna, it works superb but my main problem are the PC speakers, Trust speakers, it has a class A amplifier and radiates a lot s of RFI , can be seen on the display. I have enclosedthe PCB board in a mettlic enclosure but still RFi.? Anyone knows how to solve the situation?? Yes , I have tried a PCB D class amplifier but the sound is awful.
?
?
?
|
Re: Entry Level SDR recommendations
I have only a SDR a Winradio Excalibur with a Wellbrook antenna, it works superb but my main problem are the PC speakers, Trust speakers, it has a class A amplifier and radiates a lot s of RFI , can be seen on the display. I have enclosedthe PCB board in a mettlic enclosure but still RFi.? Anyone knows how to solve the situation?? Yes , I have tried a PCB D class amplifier but the sound is awful.
?
https://www.youtube.com/watch?v=aPWQi-A-e6Y&t=236s
?
?
|
Re: TX protection on RX Loop
Hi
Use the rx in antenna port for loop..its an icom so should have one.
(If its txing into loop you worried about.)
Simon g0zen
|
Re: TX protection on RX Loop
Thank you everyone who has helped with my question for these great ideas. I'm pretty sure I understand how I need to proceed now. The biggest problem with the Icom 737 is the pesky transmit button just a few millimeters underneath the on and off switch. I have already had accidental activation of TX. Made just be wiser not to combine the two aspects of the hobby (SWL and TX) on the one radio.?
On Sat, 22 Feb 2025 at 4:48, biastee via groups.io <biastee@...> wrote: Add a PIN limiter diode across the input terminals. Why a PIN diode and not an ordinary small signal diode like 1N4148? The former's longer carrier lifetime prevents the diode from "following" the RF signal; i.e. being turned on and off and producing intermodulation products. A good reference is this: . Referring to fig. 1 in the referenced article, the shunt inductor can be omitted as the loop plays the same function.
73, Leong, 9M2LCL, ex-9W2LC
?
|
Re: TX protection on RX Loop
Add a PIN limiter diode across the input terminals. Why a PIN diode and not an ordinary small signal diode like 1N4148? The former's longer carrier lifetime prevents the diode from "following" the RF signal; i.e. being turned on and off and producing intermodulation products. A good reference is this: . Referring to fig. 1 in the referenced article, the shunt inductor can be omitted as the loop plays the same function.
73, Leong, 9M2LCL, ex-9W2LC
?
|
Re: TX protection on RX Loop
Looked up the amp. The two transistors seem to be marked as "1A" which are generic 2N3904 surface mounts. They would be National Semi process process 23 devices which have a 2db NF above 100Khz. One of the documented transistors of the late 1960's. If you pop a few, they are easy to replace and inexpensive. 2N3904A's are the same device. The "A"s seemed a bit more consistent, box to box.
?
Almost any relay "cure" is going to be more costly than the current online price of the of the amp (the LAMB-1B amps seem to be on sale at the Casarain site right now). Even a PIN diode in reverse parallel to a Schottky diode to drive the PIN will cost more than the amp. (This was the cure for protecting the 20mA input fuses on our AIL test sets). >"AIL" is Airborne Instrument Labs<.
?
If you can find them, series #49 lamps between the loop and amp inputs will also work as inexpensive 50 ma fuses. Small cold resistance but large (18X and fast) resistance hot.?
?
Jim/VEZ
|
Found this on another group and thought it might interest someone here, but not for the budget minded:
?
https://www.netsandmore.com/products/fishing-accessories/fiberglass-hoops
|
Re: TX protection on RX Loop
Hi
Use ptt out ( used to switch amp to tx)to control a little relay in line with rx coax. If the relay goes after bias T ( loop side) it will also shut off power to loop preamp.
The relay crt is dead easy, use the power for bias t to supply crt.
Or You could just use 1transister inline with power to bias t, this also controlled by ptt. That would just kill power to loop on tx.
However if you are using antenna 2 out in rig and not rx in, then you can easy blow it up if you tx from ant 2 out into loop..so if you can always use rx in antenna socket.
Simon g0zen
|
Re: TX protection on RX Loop
Hi Tom, it's an Icom IC-737?
73 Adam
|
Re: TX protection on RX Loop
|
James Redding WA9VEZ
Everett N4CY
Adam