RV Net - 10/8/2020

Below you can listen to an MP3 file of audio from my FLEX-3000 transceiver, recorded during the second hour of the RV Service Net. I edited an 18-minute recording to remove long periods of no usable signal. I left in a few short segments where a signal was marginal. The result is less than 15 minutes long.

RV Net - part of 2nd hour

The stations heard include: AI1N,W5BUY, W8MQ, N0JHX, KC4GO, and W4BXI. You'll hear W4BXI as net control station transmitting from the following sites, in order: N4GYN, WA5MLF, KC4GO, W4UOA. W4BXI connected to each station via the Internet, using software from RemoteHams.com.

When transmitting from WA5MLF, there is no background radio noise, since the recording captured the VoIP audio coming into the transceiver from the RemoteHams software components.

I have a few other short recordings, from that same net session, that also may be worth sharing.

73,

John WA5MLF

Ionosonde sweeps the 40 m band

 

 

 

 

 

 

 

While viewing the 40 m band with my SDRplay receiver I saw a strong ionosonde signal sweeping across the band, as shown in the above screenshot. The top part shows the signal on the panadapter view (horizontal axis is frequency, vertical axis is amplitude). The bottom part shows the waterfall display (horizontal axis is frequency, vertical axis is time, progressing downward). Signal amplitude is represented by brightness. The sweep shows here as a diagonal line. Other stations on the band are operating on fixed frequencies.

Data collected by the ionosondes around the world are publicly available. See my blog posting: Graphs of Maximum Usable Frequency from Ionosonde Data for more information. The collection and analysis of data from ionosondes is managed by the GLOBAL IONOSPHERE RADIO OBSERVATORY.

I captured a video of the SDRplay window that includes a sweep, as seen below. There is no sound in this recording. Normally one hears only a short chirp as the sweep passes through the receiver's audio bandwidth. On this view the 2.8 kHz audio bandwidth is the thin vertical column in the center. Other active signals on the band are seen as the up-and-down white vertical spikes.

 

RCForb testing with foot switch

W4BXI is using a custom circuit to interface an ordinary foot switch to the TX function of the RCForb client program on his Windows PC. We have observed occasional stuttering in his transmit audio during the first 2 seconds or so after the foot switch is pressed. Today I made a recording of his contact on 40 m, transmitting from W4UOA, with a Virginia station. The full 3.5 minute recording is available below for listening.

QSO on 7193 kHz

You can hear the audio stutter just past at about 2:24 in the recording. Below is a 2-second excerpt from the recording along with a screen capture of the audio waveform that shows several quick drop-outs as received in Baton Rouge. 

2-second portion with audio stutter

Additional testing is being arranged to isolate the cause of the drop-outs.

RV Net - 9/24/2020

Here are 5 audio clips from the second hour of the 9/24/20 (East-Central-Canada) RV Service Net on 7.191 MHz, recorded from my Flex-3000 transceiver in Baton Rouge. Any long time segments with no readable audio have been shortened or edited out. The stations heard are identified above each audio clip. 

John WA5MLF

AI1N

W8OI, WK1F, N4JLR

N4JLR, W8OI, WW1SS

K9JWJ

K9JWJ, W4BXI (via N4GYN), K4ICZ, W4OWT

WU5E (Korea) to RVNet -- 9/17/2020

 WU5E checked into the RV Net from South Korea using an Internet remote connection to his Flex-6600 in Tennessee. Below is part of his exchange with net control W4BXI. The audio was recorded by WA5MLF in Baton Rouge on his transceiver.

The figure below shows that WU5E and W4BXI use the Internet to connect to separate transceivers remotely. There is no direct Internet connection between their computers.

Sloper Antenna for 20 m thru 10 m

A sloper dipole antenna is planned for evaluation at W4UOA to supplement the two horizontal dipoles and one horizontal loop antenna. The hyperlink in the previous sentence has a very nice analysis of the sloper antenna. I offered to do some modeling of the new antenna at W4UOA, and some results are presented below. The antenna is sized (length = 29 ft)  according to W8JI guidelines for a multi-band dipole. The radiation plots are oriented for a westward direction of greatest gain. The heights of the antenna ends and the slope angle are arbitrary starting points. The antenna is to be fed with 450-ohm balanced line that transitions to 50-ohm coax cable thru a balun.

Click on any plot to magnify.

This plot shows the total gain (horizontal and vertical polarization) of the antenna at 14.25 MHz in the horizontal plane. The blue curve maps the gain (dBi), with the scale progressing outward from the center of the plot. The labels around the plot are azimuth, like compass bearings, going clockwise around the circle. 0º is North. The antenna is in the plane oriented east-west. The maximum gain is 2.25 dBi at azimuth 334º.

This plot presents the total gain in the vertical plane. The labels around the circle are elevation (above horizon) angles. This shows the maximum gain (2.25 dBi) occurring at 46º at azimuth 338º.

This plot shows the vertical gain in the horizontal plane. The maximum gain is 2.11 dBi at azimuth 270º and elevation angle 72º.

Here is a 3D view of total gain with colors to signify the gain according to the scale at the left side of the figure. The slanted white line represents the antenna structure. The web link at the top of this article has a very nice animation of 3D and 2D views showing how the gain varies with the angle of the antenna from vertical to horizontal. The author of the article uses the same modeling software as I have used for these plots.





The W8JI article with guidelines for multi-band dipoles recommends balanced feed line of 300-ohm characteristic impedance.  Since Carl has 450-ohm balanced line on hand, I ran comparisons of the design using both feed line types, for the frequency range of interest -- 14 to 30 MHz. The modeling software generated tables of data including: SWR, gain F/B ratio,impedance (R, X, |Z|, phase). I made graphs to compare the SWR vs frequency and impedance (magnitude) vs frequency for both feed line impedance values. The graphs below show that for most frequencies there is not a large difference between the results of the two impedance values.  The SWR data are based on a 50-ohm source impedance. These results do not include the coax cable that will extend the balanced line to the antenna tuner. That detail can be added to the model at any time.

I would prefer to start these graphs at 14 MHz, but I don't know how to prevent Excel from starting at zero on the x-axis.

It will be interesting to see how this new antenna performs at W4UOA in comparison with the other antennas.

73,
John WA5MLF