Messages

61

Equipment / Re: Question about ordering aluminum tubing

« on: February 22, 2022, 1218 UTC »

If you really want to go with aluminum tubing, DX Engineering has a selection of tubing:

https://www.dxengineering.com/search/part-type/aluminum-tubing


Another alternative is the Hygain AV18-VS antenna.  It sells for about $200 and is really nothing more than a vertical aluminum antenna, with a loading coil at the base.
 
The S9v31 approach seems to work well for many.  DX Engineering also sells fiberglass tubing if you elect to follow this path.

62

Equipment / Re: Common mode noise

« on: February 22, 2022, 1159 UTC »

Your comment about OCF dipoles and end fed wires is interesting.  I had never considered them as being worse for common mode noise pickup before, but your logic makes sense.

A decade ago I had a 80 meter dipole with a balun, fed with coax.  The coax went straight down and then entered an underground pvc pipe that led to the house.  At the house it connected to a grounded metal plate for entry into a basement hamshack.  I remember that antenna as being very quiet for RF noise, even though I was surrounded by neighbor homes in close proximity in all directions.  I see now that it was well situated to minimize common mode noise pickup, though that wasn’t done knowingly.
 

63

Part 15 AM and FM Station Operation / Re: Questions about part 15 shortwave

« on: February 20, 2022, 1429 UTC »

This ISM band runs from 13.553 to 13.567 MHz - a 14 kHz wide bandwidth.  It won’t support more than one or two AM transmitters.

This doesn’t seem like a good idea.

* If you want to stay legal, your output power will only be a few milliwatts at best.

* You are going to be competing will all sorts of industrial noise emittters.

* You are going to be interfering with a number of established hobbiest beacons.

64

Equipment / Common mode noise

« on: February 19, 2022, 1624 UTC »

N6GN says:

“…….In studying noise sources and in particular the coupling of these sources to the KiwiSDR I’ve come to realize that one of the dominant coupling mechanisms of signals that degrade receiver noise floor is via common-mode signals. These can exist almost everywhere in the system; they exist on the antenna
itself, within ground systems, on the feedline and other connections to the antenna and through the KiwiSDR itself. I’m presently of the opinion that for most amateur stations and even most KiwiSDRs that the dominant source of unnecessary SNR degradation, QRN and QRM, is due to common mode currents. Near-field coupling to a variety of types of local sources, interference which is attenuated as a function of distance faster than the inverse-square field of a radiated plane wave emanating from a distant source dominates a majority of amateur stations.

Although resignation to the existence of “all those noisy digital devices” and the mindset that interference has to be accepted seems to be the prevalent wisdom within the hobby, I’ve found that this is not the case. I have come to believe that the vast majority of amateur receive systems are not limited by either propagated noise, which would be the desired condition, or by radiated noise from local interferers, as is commonly espoused, but by coupling to near-field sources and in particular common mode noise…..”

source:
https://forum.kiwisdr.com/uploads/Uploader/5f/492f44efb5a272d715c5219da67b44.pdf

This pdf has further thoughts on this. (The active antenna he mentions was in the Oct 2018 issue of QST, not Sep 2017 as he states in the pdf.)

65

Propagation / Re: Three Cheers...

« on: February 10, 2022, 1313 UTC »

There is better detail in the story here:
https://www.space.com/spacex-starlink-satellites-lost-geomagnetic-storm

There is more to the story I imagine.  It isn't clear why they couldn't leave "safe mode".  Was this a design issue?  Were the spacecraft at a point that their propulsion system couldn't recover them?

There will be more details in the weeks to follow.  Starlink has to provide information to keep financial investors interested.

The spacecrafts use Hall thrusters to maneuver.
https://spaceflightnow.com/2019/05/15/spacex-releases-new-details-on-starlink-satellite-design/

66

Amateur Radio / Re: Consensus of average 40M noise level

« on: February 10, 2022, 1253 UTC »

I don't have anything off in the house that is normally on. Just wanted to know what other people are averaging. Most all other bands seem to have a reasonable noise level. I currently have 2 TV's on, 3 PC's running along with 2 tablets. No fancy lighting in the house etc. Somewhat rural area.

I hear you.  I also live in a rural area and the noise is puzzling.  You swear that nothing is on in the house but...there is always something running.  My last big "Aha!" moment was when I discovered my coffee maker was a noise maker. Battery chargers and wall warts are big noise producers.  You forget about that wall wart plugged in to the wall because nothing is plugged into it, but it is still running.  Some devices (like TVs) are always active, even when the power switch is off.  I ended up plugging the coffee maker into a SPST power switch so I could completely power it off.  Of course now the clock and timer in it are useless.

You pretty much have to go room by room and examine what is plugged into each outlet.

There have always been noise sources during my years in radio, but they are worse today.  Back in the day all I had to contend with were mostly 15 kHz TV oscillators, bad powerline insulators, and car ignition systems.

I doubt many listeners today have ever heard what a low noise level actually sounds like.  After a while you start to think S2/S3 noise as normal in a rural environment.  It isn't.

67

General Radio Discussion / Government auctions…

« on: February 06, 2022, 0608 UTC »

Interesting find.  Looks a little rough though.

https://www.reddit.com/r/amateurradio/comments/sbrzh1/interesting_find/?

68

General Radio Discussion / Re: AFN on shortwave still exist?

« on: February 04, 2022, 1544 UTC »

AFN is mostly distributed via C band satellite.  With changes coming to C band, that may change.
https://media.myafn.dodmedia.osd.mil/AFNHD/Signal_Acquisiton_Guide.pdf

Retired military can get a decoder key, but you have to live outside the US.
https://myafn.dodmedia.osd.mil/

There is an Internet broadcast called AFN 360, but they take steps to ensure you are outside the US.

69

HF Mystery Signals / Re: Clicky Carrier

« on: January 30, 2022, 1403 UTC »

You’re right, they are very similar.  Interesting!

70

HF Mystery Signals / Clicky Carrier

« on: January 29, 2022, 1517 UTC »

http://ka7oei.blogspot.com/2021/12/the-case-of-clicky-carrier.html

71

Amateur Radio / Re: Equipment Recommendations?

« on: January 03, 2022, 1224 UTC »

The Icom IC-718 is popular for the price, and AFAIK, its receiver side is similar to the popular R-75.

This topic was covered on HFU before.  The R75 is a triple conversion receiver, the IC-718 is double conversion.  The R75 had a little more control over AGC, but still had problems on SSB/CW.  Proper use of your RF gain control helps a lot…which is why it is there <G>.  Token noted on the Radioreference.com site that the circuit board layouts are quite different.

https://www.hfunderground.com/board/index.php?topic=59595.0

https://forums.radioreference.com/threads/ic-718-transceiver-ic-r75-receiver-circuitry.368407/

If I was saving up for a rig, I would wait until I had enough to buy a IC-7300.  I don’t think there is another radio on the market that gives you the bang for the buck that the IC-7300 offers and in sheer numbers sold, it may well be the most popular ham rig ever.  Radios like the IC-7100 or FT-991A also give you VHF/UHF which is something to consider if that is important to you, but for HF the IC-7300 is better.  The IC-7300 comes with DSP filters whereas the IC-718 requires you to buy additional filters.  The IC-718 is an older design than the IC-7300, which *might* mean that the IC-7300 will be supported longer, but these days who knows?  A brand new IC-7300 is going to cost you around $1000 - more expensive than the IC-718, but more likely to be the radio you will still be using years in the future.  You will likely outgrow the IC-718 if you stay in the hobby.

72

Amateur Radio / Re: Equipment Recommendations?

« on: January 01, 2022, 1510 UTC »

The IC-718 suffers from one problem - horrible fast AGC time constants on SSB.  The audio “pumps” (especially on medium to strong signals) and is tiring to listen to for any length of time.  You can make the radio tolerable by using the RF gain control to reduce the received signal strength so that the AVC isn’t so active.

I have never seen a mod to fix this.  The only mod for the AGC I found was one that forced the radio to use the AGC settings for one of the other modes.  It’s too bad as the radio is otherwise OK.  I used one for MARS operation for a few years.

Despite the physical resemblance to the Icom R-75 receiver, the IC-718 receiver section is not the same.  The R-75 is better.
 

73

General Radio Discussion / Deep Space Communications

« on: December 28, 2021, 1449 UTC »

All you might ever want to know about Deep Space Communications.  The sidebar links take you to even more information.

https://descanso.jpl.nasa.gov/monograph/mono.html

74

VHF/UHF Logs, including satellites and radiosondes / Starlink Beacons

« on: December 03, 2021, 1343 UTC »

Here are details on Starlink satellite beacon reception.  There is another link early in the Reddit link that takes you to a detailed discussion of the hardware being used.

I first saw mention of this on the RTL-SDR list, but the Reddit post has more details.

For mere detection of the beacons, much less is required.  There have been reports of success with nothing more than a Ku LNB pointed straight up, no dish.  A generic Ku LNB will mix down to L band, which is in band for almost all the popular SDR receivers. The doppler shift will verify that you are hearing the satellites.


https://www.reddit.com/r/StarlinkEngineering/comments/r7mmsd/a_tale_of_two_satellite_constellations_update_1/

75

SDR - Software Defined Radio / KiwiSDR and HFDL

« on: November 16, 2021, 1746 UTC »

The latest software build for the KiwiSDR has added a HFDL decoder.