Messages

1

Peskies / Asian Fishing 5377.7 USB Eastern Pacific still active 2020NOV30

« on: November 30, 2020, 0527 UTC »

2020 NOV 30 0400UTC
5377.7 kHz USB voice
Asian language fishing fleet, likely S. Korean.
4 or 5 stations.
Approximate location today: a few hundred miles off the coast of Oregon and California.
Often heard nightly 0400-0530UTC spinning big fish stories to each other on this frequency.
Motors and other industrial ship background sounds.

Note: this isn't a normal Maritime HF channel or band

2

Propagation / Re: Here's our pre geomagnetic storm foF2/MUF boost

« on: September 28, 2019, 2335 UTC »

It provided some really good transequatorial propagation and F2 openings on 27 and 28 MHz.

3

HF Mystery Signals / Re: 8956khz Aug 4 02:37utc

« on: September 27, 2019, 0024 UTC »

No, almost certainly not an OTHR.

Yes, agreed, it isn't OTHR.
Also agreed, it looks like a sweep tone within a standard 3 kHz or 2.8 kHz speech communication bandwidth.
The curious discontinuous wiggles in the sweep frequency might be some kind of data, or be just a glitch.
That makes it interesting. 

4

Other / Re: 5690KHz Japanese/English voice tx

« on: September 22, 2019, 2032 UTC »

This is an international standard "Aero Off Route" channel.

Generally open Aeronautical freq, but usually not LDOC or RDARA or MWARA.
It can be utilized by all types of aircraft and air-ground or aero comms orderwire (private, corporate, mil) entities.
Most of the "Aero Off Route" channel allocations are well known for mil air.

Other standard "Aero OR" channels may be found at 3.0 kHz intervals up from this channel.
etc.
5680 international AERO SAR channel with Maritime SAR interoperability (+/-4 kHz protection)
5684 "Aero Off Route"
5687 "Aero Off Route"
5690 "Aero Off Route"
5693 "Aero Off Route"
5696 "Aero Off Route"
5699 "Aero Off Route"
5702 "Aero Off Route"
etc.

5

Equipment / Re: Test Equipment for First Time Build

« on: September 13, 2019, 1849 UTC »

A calibrated radio receiver.

6

Other / Re: 57530 LSB 08:51z automatic laser gun firing sound w

« on: September 10, 2019, 0544 UTC »

Automatic laser gun, firing sound, with a beep beep beep.

Google OTH Radar and CODAR.

7

Equipment / Re: Inverted sloper?

« on: September 06, 2019, 1634 UTC »

Put the feedpoint up as high as possible.
If one end is higher, make it the "hot" side.

8

Peskies / Re: Angry and not so angry fishermen 5178.25 USB 1200 UTC 1 Aug 2019

« on: August 04, 2019, 1606 UTC »

There used to be hf barge traffic on the Missouri and Mississippi rivers, where did it go?

Cellphones.

9

Equipment / Re: New T2FD Antenna Construction and Performance

« on: July 28, 2019, 1854 UTC »

Generally speaking, the radiation pattern for a T2FD antenna with a balun is the same shape as a dipole of the same length.
The only difference is in the efficiency gain or amplitude of the curve.

On HF, it is advantageous to get the feedpoint as high as possible, especially to get the radiation center above ground clutter and above receive RFI sources.
For a single support, the Inverted-V configuration gets the feedpoint at the top.

And it turns out that the TFD tends to do very well as an Inverted-V.
Structurally, the inverted-v configuration helps to manage the weight and wind loading of the coaxial cable, balun, spreaders, and termination resistor.
The inverted-v TFD is the most commonly seen HF antenna throughout most of South America and Southeast Asia, as radio ops who travel there have probably noticed

10

Equipment / Re: New T2FD Antenna Construction and Performance

« on: July 27, 2019, 1649 UTC »

  I found that reception was equally good either near horizontal or tilted close to 30 degrees. Maybe Countryman's original 30 degree design was in regards to transmitting for his intended purpose?

The original Countryman T2FD antenna was tilted to help offset the imbalance problems the design had due to its high impedance open wire feed.

In other words, they had a lot of transmission line radiation that showed up as nulls and peaks in the measured radiation pattern.
Tilting the flat top helped to fill in those nulls.

There was no balun in the original designs.
The open wire feedline was not decoupled from the antenna at all.

Ferrite baluns, which came along later, were applied in updated Terminated Folded Dipole designs.
Using a ferrite balun provides feedline isolation over a broad spectrum, eliminating feedline radiation in the TFD.

There is no magic tilt (and no need for tilt) in a TFD that has a balun.

 

11

10/11 meters / Re: 27 MHz ISM Fish Hook Swisher Interference RFI EMI RF HF Sealers Heaters Welders

« on: July 14, 2019, 2150 UTC »

It is no wonder that these ISM signals can be propagated to very far distances.
The governmental regulations for these transmitting devices are very loose, allowing high power levels and high radiated signal strength.

For example, here are some of the US federal ISM transmitter regulations from about 10 years ago, at a time when many of the ISM devices presently in use were designed [emphasis added].

• Operation on Particular Frequencies Designated for ISM Equipment
  
  The following frequencies are designated for use by ISM equipment, the emissions of which shall be confined within the frequency limits associated with each frequency:
  
  6780 kHz ± 15.0 kHz
  13560 kHz ± 17.0 kHz
  27120 kHz ± 163.0 kHz
  40.68 MHz ± 20.0 kHz
  915 MHz ± 13.0 MHz
  2450 MHz ± 50.0 MHz
  5800 MHz ± 75.0 MHz
  24.125 GHz ± 125.0 MHz
  61.25 GHz ± 250.0 MHz
  122.5 GHz ± 500.0 MHz
  245 GHz ± 1.0 GHz
  
  In the event harmful interference is caused by ISM operation to any authorized radio service outside the frequency limits specified,
  the operator of the ISM equipment shall promptly take necessary steps to eliminate such interference,
  except in those cases where the interference is due to direct intermediate frequency pickup by a receiver of the fundamental frequency emissions of ISM equipment operating on an ISM frequency, and the operator otherwise complies with this section.
  
  ISM equipment, other than industrial heating equipment, that is operated on the frequencies 915, 2450, 5800 MHz, and 24.125 GHz, is subject to the following conditions:
  1. The energy radiated and the bandwidth of emission shall be reduced to the maximum extent practicable.
  2. In the event harmful interference is caused to authorized radio services from spurious or harmonic radiation from ISM equipment, the operation of the ISM equipment shall be discontinued until necessary measures have been taken to eliminate such interference.
  
  Medical diathermy equipment may be operated on the designated ISM frequencies without regard to the type or power of emissions being radiated, except as specified above. However, any harmonic or other spurious radiation outside the frequency limits specified in this section shall be suppressed so as not to exceed a strength of 25 uV/m at a distance of 300 meters.
  Measurements to determine field intensity shall be made in accordance with standard engineering procedures.
  
  Industrial heating equipment and RF stabilized arc welders may be operated with unlimited radiation on any designated ISM frequency, but shall be adjusted to operate as close to that ISM frequency as practicable. Filtering between the industrial heating equipment and power lines must be provided to the extent necessary to prevent the radiation of energy from power lines on frequencies other than those designated for ISM, with a field strength in excess of 10 uV/m at a distance of 1600 meters from the industrial heating equipment, and at a distance of 15 meters from the power line.
  
  Miscellaneous ISM equipment may be operated on the designated ISM frequencies without regard to the type or power of emissions being radiated, provided any harmonic or other spurious radiation outside the frequency limits specified in this section is suppressed so as to not exceed:
  25 uV/m at a distance of 300 meters or,
  for equipment generating more than 500 watts of RF power on the fundamental frequency,
  25 uV/m times the square root of P/500 (where P is the actual RF power generated),
  but not to exceed 10 uV/m at 1600 meters,
  provided this increase is not permitted for equipment located in a predominantly residential area and operating on a frequency below 1000 MHz.
  
  Operation on Frequencies Other than Those Designated for ISM Equipment
  Operation of ISM equipment within the following safety, search and rescue frequency bands is prohibited: 490-510 kHz, 2170-2194 kHz, 8354-8374 kHz, 121.4-121.6 MHz, 156.7-156.9 MHz, and
  242.8-243.2 MHz.
  
  In the event harmful interference is caused to any authorized radio service outside the frequency limits specified in previous Section, by ISM operation conducted pursuant to this section, the operator of the ISM equipment shall promptly take the necessary steps to eliminate the interference.
  
  Medical diathermy equipment shall be provided with a rectified and filtered plate power supply, powerline filters, and shall be constructed so that any radiated radio frequency energy (including harmonic or other spurious emissions) on a frequency outside the frequency limits specified in the previous Section does not exceed a strength of 15 µV/m at a distance of 300 meters.
  
  Measurements to determine field intensity shall be made in accordance with standard engineering procedures.
  
  Industrial heating equipment and RF stabilized arc welders may be operated provided all of the following conditions are met:
  
  1. Radiation on the fundamental carrier frequency, as well as spurious and harmonic radiations resulting from any source frequency, and falling outside the frequency limits specified in the previous Section, shall be suppressed so that:
  
  a) below 5725 MHz the field strength does not exceed 10 µV/m at a distance of 1600 meters and;
  
  b) above 5725 MHz it is reduced to the greatest extent practicable.
  
  2. Filtering between the industrial heating equipment and power lines shall be provided to the extent necessary to prevent the radiation of energy from power lines on frequencies other than the designated ISM frequencies, with a field strength in excess of 10 µV/m at a distance of 1600 meters from the industrial heating equipment and at a distance of 15 meters from the power line.
  
  Miscellaneous ISM equipment may be operated on frequencies other than those designated for ISM equipment provided all of the following conditions are met:
  
  1. The equipment shall be provided with a rectified and filtered plate power supply and power line filters.
  
  2. Any radiated radio frequency energy outside the frequency limits specified in previous Section (including harmonic or other spurious emissions) shall not exceed:
  15 µV/m at a distance of 300 meters; or, for equipment generating more than 500 watts of RF power on the fundamental frequency, 15 uV/m times the square root of P/500 (where P is the actual RF power generated), but not to exceed 10 µV/m at 1600 meters, provided this increase is not permitted for equipment located in a predominantly residential area and operating on a frequency below 1000 MHz.
  
  Operation of ultrasonic equipment shall not result in radiation exceeding the following limits:
  
  1. Below 490 kHz
  2400 µV/m at 300 meters/Frequency (in kHz)
  
  Between 490 and 1600 kHz
  24000 µV/m at 30 meters/Frequency (in kHz)
  
  Over 1600 kHz (excluding frequencies within the limits specified in previous Section)
  15 µV/m at 30 meters
  
  2. For equipment operating below 490 kHz and generating more than 500 watts of RF power on the fundamental frequency.
  2400 µV/m at 300 meters “Frequency (in kHz) times the square root of P/500 (where P is the actual RF power generated), but not to exceed 10 µV/m at 1600 meters”, provided this increase is not permitted for equipment located in a predominantly residential area.
  
  3. On any frequency 490 kHz and above, the radio frequency voltage appearing on each power line shall not exceed 200 µV; below 490 kHz it shall not exceed 1000 µV.
  

12

10/11 meters / Re: 27 MHz ISM Fish Hook Swisher Interference RFI EMI RF HF Sealers Heaters Welders

« on: July 11, 2019, 0904 UTC »

Driving home last evening I have my radio set to 27.385 and as usual there is no activity, so I leave it at low volume. Just before 6:00 Los Angeles time, the swisher sound was so clear and very loud. I only heard one, it sounded like a local signal but chances are it came from some distance.

That ISM you heard could have been anywhere within a 2000 km radius, since it was probably via "short skip".
Put a pin at your location and draw a 3500 km diameter circle around it.
The location of that ISM was probably on that line.
It's amazing how strong short skip can be, almost as if it is being amplified.
There's been a whole lot of short skip (Es) lately around California, the west coast, and around the rockies.

13

Fishing Drift Net Beacons / Re: DNB CI7 2.308MHz in for hours, propagtion type?

« on: July 03, 2019, 2244 UTC »

Groundwave is probably the answer I think, but would appreciate comments from fellow HFU DXers.

It was probably not groundwave.

It was simply NVIS (Near Vertical Incidence Skywave) propagation, very common via the F-layer of the ionosphere.
NVIS usually doesn't extend more than about 650 km (400 miles), so perhaps the DNB was within that distance from your receiver.

See this image of the Digisonde from your nearby Canberra ionosonde, for the time interval of your report.
The squiggly solid horizontal line in the bottom left side of the graph shows the zenith reflective F layer was good for NVIS propagation in the 1.74 MHz (fmin)  to 5.670MHz (foF2)  range.


For other dates and times, see this link to the Canberra ionosonde:
https://lgdc.uml.edu/common/DIDBYearListForStation?ursiCode=CB53N

14

HF Beacons / Re: 7 MHz Western USA Beacons

« on: June 16, 2019, 2207 UTC »

Just bounced back over to 7998 and HI has now returned.

09MAR2019 23:36z 7998.07 KHz,  fairly strong then fades out for a transmission or two.

Has anyone copied HI recently?

15

10/11 meters / Re: 27 MHz ISM Fish Hook Swisher Interference RFI EMI RF HF Sealers Heaters Welders

« on: June 14, 2019, 2039 UTC »

Noticing a large number of swooshes on the lower freeband frequencies - roughly 26.500 MHz to 26.900 MHz, with some in-band as well.  All 40 CB channels are busy at 1613 UTC.

Some possible speculation for the prevalence of ISM fish hook swishers below the 27 MHz ISM and CB bands:

1. Natural downward frequency drift of the ISM work head resonant L-C tank when in use.

2. Initial calibration at 27.12 MHz is done with the heating work head in free air, rather than in contact with the dielectric work piece, which increases capacitance and causes resonant frequency to shift lower.

3. Factory calibrators may intentionally tune each ISM device toward the low end of the ISM band ~26.96 MHz (rather than 27.12 MHz center) to avoid the wrath of:
_ a. Amateur radio 28 MHz fox hunt vigilantes, frequency cops, or intruder monitors.
_ b. CB radio operators who might get angry.

4. After the ISM device is purchased and goes into service, it is probably never frequency calibrated again because nobody cares.