Messages

1

General Radio Discussion / Re: Good old days

« on: March 07, 2025, 0028 UTC »

Back in the seventies, several of us teenage SWLs visited a older guy near Baltimore.  He brought out an old wire (yes, wire not magnetic tape) recorder and played SW station IDs from the thirties and forties.  Wow.  I was floored at the exotic DX and the fact that the signals sounded so good.  Sure wish I had a mp3 of it today!

It never occurred to me that the stuff I heard every day back then would be similarly “exotic” one day, as SW broadcasters shut down.  Now I wish I had made my own recordings during the seventies.

2

General Radio Discussion / Re: "This site can't be reached" very often : are you also experiencing that ?

« on: March 04, 2025, 1059 UTC »

Could this be a DNS problem?

3

Equipment / Re: vertical or horizontal for sw pirate radio?

« on: March 01, 2025, 1454 UTC »

On SW, polarization gets mixed up after reflections off the ground and ionosphere, so you never know what to expect.  Consideration of whether an antenna is vertically or horizontally polarized is overcome by the question of what kind of gain pattern the antenna has.

On VHF, propagation is usually line of site so the polarization of the receiver and transmit antennas is of more concern.  If cross polarized, you can suffer more than 20 dB of loss, but that is only if you are perfectly cross polarized.  If you installed a beam at a 45 degree angle, you would only be down by 3 dB for horizontally or vertically polarized signals.

Even at VHF you can see reflections off of objects like buildings so the polarization you receive may or may not be what was transmitted.

4

General Radio Discussion / Re: Russia-linked cable-cutting tanker seized by Finland ‘was loaded with spying equ

« on: February 01, 2025, 1445 UTC »

Estlink2 is a HVDC power cable.

https://en.wikipedia.org/wiki/Estlink

https://en.wikipedia.org/wiki/2024_Estlink_2_incident

5

General Radio Discussion / Re: Russia-linked cable-cutting tanker seized by Finland ‘was loaded with spying equ

« on: January 31, 2025, 1438 UTC »

The picture here is more like what I would have expected.

https://lieber.westpoint.edu/baltic-sea-cable-cuts-ship-interdiction-c-lion1-incident/

This photo isn’t labeled as to what it actually is of, but it is illustrative of what damage might look like.

Remember that they don’t have to actually sever the cable.  All they need to do is breach it to seawater and there will probably be arcing.

6

General Radio Discussion / Re: Russia-linked cable-cutting tanker seized by Finland ‘was loaded with spying equ

« on: January 31, 2025, 1417 UTC »

I am not sure that the photo you are referring to is the actual break.

I don’t think they have shown a picture of the cable damaged in the latest incident.  I believe the photos shown were from an earlier incident.

It is possible the photos we have seen are from a piece of the cable that was cut out to facilitate repairs.  We may be seeing an end the repair crew cut with a saw.

If the ship had a cutting device of some sort, can you imagine the arc explosion when you cut through and shorted the cable with your cutting device?  I would expect to find the device arc welded to the remenants of the cable.

7

General Radio Discussion / Re: Russia-linked cable-cutting tanker seized by Finland ‘was loaded with spying equ

« on: January 30, 2025, 1417 UTC »

Or this scene from the Battleship movie?

https://www.youtube.com/watch?v=5AJKah6-YCY

Yeah, it doesn’t work like that.  No anchor could handle the momentum of a ship underway like that.  Standard practice is to come to all stop prior to deploying an anchor.  After deploying you would back astern to set the anchor.


Back in my active duty days I learned that it wasn’t so much the flukes of the anchor digging into the sea bed that held a ship in place as it was the weight of the chain deployed.  Not all anchors have flukes.  Submarines have mushroom anchors for instance.

Losing an anchor or dragging is not unheard of.  When anchored we were required to regularly take fixes on our position to ensure we weren’t slipping.

Surface ship anchors are visible so if they had a special anchor to cut cables, it would be apparent.

8

22 Meter Band HiFER Beacons / KEPR 13564.29 kHz 1332Z

« on: January 28, 2025, 1333 UTC »

Weak, fading in and out.

Rcvr: KiwiSDR, Northern VA, longwire antenna

9

The RF Workbench / MPJA closing

« on: January 02, 2025, 1803 UTC »

I often buy electronic parts from Marlin P. Jones & Associates in Florida (www.mpja.com)

Lately I have noticed them closing out more and more of their inventory and offering significant discounts (currently at 20%) on other stock.

I checked with them and they confirmed they are planning on closing sometime in 2025.  Sales have dropped, possibly due to hobbyists buying direct from China.

They join a growing list of companies that cater to the hobby and have shut down in the past few years, including All Electronics, Fair Radio, and Universal Radio.

10

General Radio Discussion / Re: Russia-linked cable-cutting tanker seized by Finland ‘was loaded with spying equ

« on: December 31, 2024, 1625 UTC »

I am surprised by how clean the cut is.  It is as if it was sheared rather than torn.  Maybe a specially shaped anchor?

One of the locals provided the answer.  The picture of the severed cable is from a different event in July 2024 where a defect in the cable was repaired.  The Daily Mail used the older picture but didn’t clarify that this picture was not from the December event.

https://news.err.ee/1609560733/estlink-2-suspected-fault-location-on-the-bottom-of-the-gulf-of-finland

11

General Radio Discussion / Re: Russia-linked cable-cutting tanker seized by Finland ‘was loaded with spying equ

« on: December 31, 2024, 1513 UTC »

I am surprised by how clean the cut is.  It is as if it was sheared rather than torn.  Maybe a specially shaped anchor?

12

General Radio Discussion / Re: I could use some help understanding SSB bandwidth

« on: December 13, 2024, 1238 UTC »

I think you are getting there. The way I think of the process is that it is all about frequency translation of my audio signal.  And the way we do this is by mixing the audio signal with another signal (the RF signal).  The math of doing this shows we then generate sum and difference signals, and we can then filter out the ones we don’t want and are left with the one we do want to transmit.  On the other end we reverse the process by mixing the received signal with a carrier signal and the mixing now gives us a signal back at audio frequencies.

I struggled with this myself years ago, especially with why on AM the waveform I would see on an oscilloscope would go to zero at 100% modulation, yet it was obvious that I was still transmitting power.  The Ah-hah moment was when I realized the oscilloscope picture was the composite of the carrier, usb, and lsb all together.  The sum of the signals could go to zero, but that didn’t mean that the individual signals were zero….they were just phased differently.

I thought I knew all of this stuff cold when I got my BSEE.  Later when I got my MSEE I realized I knew nothing.  Teaching is just a process of telling smaller and smaller lies.  You make everything sound simple at the beginning and then when the students get their heads wrapped around the basic concept, you start introducing the complexities.  It’s easy to say that in amplitude modulation we modulate the carrier.  If you look at it on an oscilloscope that is exactly what appears to be happening.  Yet the real story is much different.  Years ago the tools to see things in the frequency domain were very esoteric; today any SDR lets you see do this.  And the simple lies that worked well enough in the mid-twentieth century aren’t enough anymore.

Theoretical physicists seem to have a good grasp of this problem as they attempt to explain how the universe works.  One of them said “Not only is the universe stranger than we know, it may very well be stranger than we CAN know”. That’s pretty sobering.  But as engineers we know that we only need to know it well enough so that we can build things.



 

13

General Radio Discussion / Re: I could use some help understanding SSB bandwidth

« on: December 10, 2024, 0318 UTC »

https://reviseomatic.org/help/2-modulation/Amplitude%20Modulation.php

if you look at the second image on this page, you'll see how I understand it to be.  And you'll see that without a carrier wave, there's no signal at all.

That picture that shows the amplitude of the RF wave going up and down….that is in the time domain and the waveform you see is actually the SUM of the LSB, the carrier, and the USB signals. It is what you would see if you had an oscilloscope connected to the transmitter output.  It is seeing all the energy (carrier, LSB, and USB) at once.

The three of them are all on slightly different different frequencies, so they go in phase and out of phase with each other.   Sometimes they add and sometimes they subtract….so you see the amplitude going up and down.

At 100% modulation, 50% of the transmitted power is present in the carrier, 25% is in the LSB and 25% is in the USB.  At some points the two sidebands will be out of phase with the carrier and the  display on your scope will go to zero.  At other times everything will be in phase and you will see the scope display show twice what it does with the carrier alone.  It might appear that the signal goes to zero but if you were looking in the frequency domain (that is what a waterfall display in a SDR shows) you would see that NONE of them….the sidebands or the carrier…actually go away.

Do you have a recent copy of the ARRL Handbook?  It discusses this in Chapter 11, including drawings.

14

General Radio Discussion / Re: I could use some help understanding SSB bandwidth

« on: December 08, 2024, 1441 UTC »

Modulation is a mixing phenomena.  When we send two signals through a non-linear device, additional frequencies (called modulation products) are generated.

 If I transmit a carrier at 1 MHz, you would only see a carrier at 1 MHz.  If I then modulate that carrier with a 1 kHz tone, I am in fact mixing the 1 MHz signal with a 1 kHz signal.  What you then see is a carrier at at .999 MHz (the lower sideband), the original carrier at 1 Mhz, and another carrier at 1.001 MHz (the upper sideband).

The mixing of the 1 kHz tone and the 1 MHz carrier has produced three RF carriers. 

If you want to replace the 1 kHz tone with some audio from (going 0 to 3 kHz for example), what you get is that 3 kHz wide chunk of audio duplicated above and below the carrier (the upper and lower sidebands).  Those sidebands look just like the original audio waveform - but they are now at RF frequencies.  This is where the information is….and the upper and lower sidebands carry identical information.  You don’t really need both of them, so in SSB we remove one of them.  Also, once we have accomplished the mixing phenomena to generate the sidebands, we no longer need the carrier, so in SSB or DSB, we remove it.

It’s difficult to explain this without drawing pictures.

15

General Radio Discussion / Re: WRC27

« on: August 09, 2024, 1148 UTC »

BTW, the FCC link also included NTIA’s inputs.  Pretty much the same but they did not caveat the 3900-3950 range as Region 1 only like the FCC did.