AM broadcast received audio -- local and remote

Audio quality testing this morning involved reception of WWL-AM (870 kHz) on my Flex-3000 transceiver. I recorded audio samples from two places:

1. Flex-3000 speaker output
2. RCForb client program output

Below is a drawing that shows the arrangement of radio and computer software, and the software components that are involved in the two audio paths that I used for recording. I also showed the Ethernet connection to the Internet that provides the path to remote users. The testing reported here used only the data path internal to the PC and the external audio cable.

Click above to enlarge.

Here are audio recordings (about 18 seconds each) for the two audio paths. Click on each to hear the audio recording.

1. Flex-3000 speaker output via audio cable
2. RCForb client program output

Screen shots of the audio spectrum of each recording are shown below. Click on either for an expanded view.

Flex-3000 speaker output via audio cable

RCForb client program output

The RCForb graph shows high frequency content above 5000 Hz that may be due to the wide bandwidth of the Virtual Audio Channel and other data paths internal to the PC. It was not noticeable to me when listening via speakers.

John WA5MLF
 

Graphs of Maximum Usable Frequency from Ionosonde Data

In support of a forthcoming article on 40 m propagation during the daily East Coast RV Service Net, data has been collected for two ionosonde sites: one at Eglin AFB in Florida and one at Wallops Island in Virginia. The locations of ionosondes around the world can be seen at this web page. 

Thanks to Dan KC4GO for collecting data on

• critical frequency (foF2)
• MD = MUF(3000) / foF2
• Maximum Usable Frequency (MUF) 

from both sites, spanning 16 months. Data are available in plain text format from the Digital Ionogram Data Base.

The Eglin ionosonde provided 96 data sets for each day, and the Wallops Island ionosonde provided even more. Data were collected for propagation distances of 300 and 500 miles, which were chosen to represent some common distances among regular RV Net participants. The longest distance among regular participants appears to be about 1200 miles.  A review of past ionogram data shows that the MUF at 900 miles or beyond is typically about 7 MHz at the start of the 2-hour net. Shorter distances are likely to have poor to marginal propagation that improves gradually during the Net time frame.

Eglin Graphs

Below are some graphs developed from the Eglin ionosonde data. Click on any graph for a full size view.

The above graph shows the variation of MUF(300) [MUF at 300 miles] over the past 5 months, using data from 1200 UTC each day.

The above graph shows the MUF(300) at 1300 UTC on each of the dates.

 The above graph shows the MUF(500) at 1200 UTC on each of the dates.

 The above graph shows the MUF(500) at 1300 UTC on each of the dates.

 The above graph presents the variation of MUF(500) values during the 2-hour time frame of the RV Service Net.  The data points are taken from the same calendar period as the previous four graphs: 9/1/2019 thru 1/15/2019. The bottom curve shows the minimum value of MUF(500) for each time-of-day point among the 137 days.  The middle curve shows the average or mean value (across the 137 days) of MUF(500) for each time-of-day point. The top curve shows the maximum value of MUF(500) for each time-of-day point among the 137 days.

I plan to produce the same type of graph for MUF(300) [MUF at 300 miles].


Wallops Island Graphs

The above graph shows the MUF(300) at 1200 UTC on each of the dates.

The above graph shows the MUF(300) at 1300 UTC on each of the dates.

The above graph shows the MUF(500) at 1200 UTC on each of the dates.

 
The above graph shows the MUF(500) at 1300 UTC on each of the dates.



John WA5MLF

Hidden Damage to 450-ohm Balanced Line

Recently I installed new coax cable from my rig to the outdoor surge protector on the back of my garage, where the balanced feed line terminates from my multi-band dipole. This is the latest evolution of the dipole from its initial design based on pages 7 - 10 of the article Choosing the Correct Balun.  The current configuration has adopted some characteristics of a G5RV design.

While handling the 450-ohm window line I noticed that a short (1.25") section of one side of the line was able to bend at a much sharper angle than other parts of the line. Since this was part of the length I cut off, I examined it more closely by slicing away some of the insulation. The photo below shows what I saw.

Click to enlarge

It appeared that one strand of the stranded wire was still connected. I can't tell if this localized damage relates to the lightning strike in 2016 or the recent lightning strike to a nearby tree or high-power operation on 40 m or a combination of these events.

I am continuing to use and modify this antenna.

73,
John

Lightning - Sunday night

Here's a screen shot of the real time display from LightningMaps.org during a 15-minute period last night. The yellow and orange dots are the lightning detections. The blue dot is my home location.

My rain gauge collected 1.3" last night.

John

Joining Google Hangout from shared link

Here are some notes from my recent testing of joining a group Hangout on an Apple iOS device via shared link.

First, install the Google Hangouts app. The screen photo below shows the correct app to use, from the Apple App Store. There are 3 other Hangouts apps published by Google.

In order to use the app you must log in with your Google account.

My ham radio friends who meet on 3740 kHz have often used a group Hangout to supplement voice communication with live video and sharing of photos or software demonstrations / assistance. One of the group members starts a Hangout from the app on a mobile device or from a desktop / laptop computer by directing the Google Chrome web browser to hangouts.google.com.  The person starting the Hangout then copies the link for sharing (see image below) with other group members via the chatroom.  The group members can then click on the shared link to launch their Hangout apps and join the Hangout in progress.

This process works smoothly on Windows PCs, using the Google Chrome browser.  Some iPad users are able to join a group Hangout by clicking the shared link in the chatroom, viewed from the Safari browser. I have tested this multiple times successfully with a model A1474 iPad running iOS 11.4.  It is not clear whether older iPad models are able to "join via link" easily or consistently.  I've seen some indication that cookies must be enabled for the Hangouts app to work properly.

A member of a group Hangout can also send a direct invitation to another person via email, using the window shown below. Also, the copied link can be emailed to another person.

Communication between two individuals via Hangout can be initiated from the app by one person simply inviting the other.

Send me a reply if you have questions or comments.

John WA5MLF

Email addressee "auto-complete" entries

I and several friends have noticed the annoying behavior of some email applications to pull up multiple email addresses for a friend when entering part of a name or partial email ID in the To: field of a new email. With a careful search I found the following two (of many articles) that address the issue:



How to Clean Up Your Gmail Autocomplete List
I searched through my Google contacts for certain friends and did indeed find a few automatic contact entries, along with multiple email addresses saved in some of the contacts that I built myself. I weeded out the older, unused email addresses and see great improvements in what appears when I start to compose a new email.

I also found some older email addresses associated with Google+ Circles that I had assigned in the past. I had to remove these entries from the affected Circles and, where desired, add the current, valid contacts to the Circles.  Call it Spring cleaning.

How to stop old email addresses appearing automatically in the ‘To’ field in mail app
This article is specific to the Apple mail program.

73,
John

Customizing arrangement of RCForb windows

Based on discussion and screen shots shared this morning on 75 m, I explored some additional options for arranging and customizing the contents of components displayed in the RemoteHams  RCForb client window.

Below is a screen shot of the arrangement (active portions) I normally use when connected to the w4uoa remote.  These screen shots where made while the station was powered off.
(Click on any image below for a larger view.)

This arrangement has the KPA and KAT windows pinned to remain visible alongside the K3 graphic, as shown in the close-up view below.

This arrangement can be tailored by adjusting the boundaries among the 3 tiled windows, as illustrated below.

It is possible to drag the KPA window or the KAT window (or both) away from the pinned position to any other place on the Windows desktop.


The next screen shot shows the KPA window overlapping the K3 and KAT windows -- not a useful arrangement.  The window can be dragged away from the RCForb window completely, if desired. The pinned arrangement is probably preferred by most users.











A floating window like the above can be returned to the RCForb main window by drag-and-drop as shown below.

Click and hold on the top of this floating KPA window and move the mouse pointer toward the top right. A blue shaded area shows the current position based on the mouse pointer. A cross icon appears indicating possible landing positions for the window when the mouse button is released.

This view shows the selected landing position of the window.
















Another display option is to auto-hide the KPA and/or KAT windows.

This view shows both windows auto-hiding. When the mouse pointer is moved onto one of these tabs, the window will open for viewing, until the mouse pointer is moved away.

This view shows the KPA window pinned, so it displays full-time, while the KAT window is auto-hiding.










Comments and questions are welcome.
WA5MLF