[Alexandria Radio Club Reflector] FW: VOA Radiogram, 10-11 August 2013

[Don Lewis (KI4D)]

As you may know VOA has been running a series of tests over HF during recent months to determine the best digital modes for most reliable and effective transmission of text and images.  I am enclosing the schedule of tests for this weekend, see the website for frequencies and times.  So far based on their testing it looks like MFSK32 performs the best.  This is an interesting finding since the ham community has for the most part been using Olivia 8/500 or MT63 modes for text transmission during  digital nets and emergency comms exercises .  It seems certain that more will be written about this subject later on.  Attached is the image I copied and submitted in a reception report to VOA last weekend.  The image, which is pretty good quality,  is of a Las Vegas Lightning Strike.  It was received  using EasyPal on 5.745MHz.

 

Don, KI4D

 

From: VOA Radiogram [mailto:radiogram at voanews.com] 
Sent: Friday, August 9, 2013 7:42 AM
To: VOA Radiogram
Subject: VOA Radiogram, 10-11 August 2013

 

cid:image001.jpg at 01CE94D3.F43D2020

 

Hello friends,

 

I am in the process of answering your reception reports from the past weekend's VOA Radiogram.

 

Some of you are doing some interesting experiments with the digital modes on VOA Radiogram. And some of you are letting us know about some useful techniques to improve both the production and the reception of the program.

 

Mark, WA4KFZ, notes that the SSTV Denoiser software, part of the SSTV Tools suite from dxatlas.com/SstvTools/, can be effective with some of the "noisy" MFSK images you receive on VOA Radiogram. 

 

In this weekend's VOA Radiogram, one VOA News item will be in the MFSK22 mode (80 words per minute). Unlike the MFSK 16, 32, and 64 modes, which have a sample rate of 8000 Hz, MFSK22 has a sample rate of 11025 Hz. For this weekend's program, I recorded to one track at 48000 Hz for the voice introduction and closing music, one track at 8000 Hz for MFSK 16 and 32, and one track at 11025 Hz for the MFSK22 item. Then all three were mixed to one .wav file with a sample rate of 48000 Hz.

 

Another "feature" in this weekend's program will be five seconds of silence whenever modes are changed. This might improve the performance of the RSID.

 

The Flmsg-formatted VOA News story in this weekend's program is 9 minutes, 6 seconds long. That might seem unusually long, but it includes 4 minutes, 20 seconds for a VOA logo in SVG format as part of the html. This was created for us by Mark Hirst in the UK.

 

Here is the lineup for VOA Radiogram, 10-11 August 2013:

 

2:30  MFSK16: Program preview

3:26  MFSK22: VOA News re import of Apple products

3:12  MFSK32: Greetings to l'Associazione Italiana Radioascolto

2:10  MFSK32 image: AIR logo

9:06  MFSK32/Flmsg*: VOA News re one year of Curiosity on Mars

2:26  MFSK32 image: Curiosity tire tracks

1:10  MFSK16: Closing announcements

2:20  Surprise image, text, image of the week

 

*To make Flmsg work with Fldigi (both can be downloaded from w1hkj.com), in Flmsg: Configure > Misc > NBEMS -- Under Reception of flmsg files, check both boxes, and under that indicate where your Flmsg.exe file is located.

 

Please send your reception reports, audio samples, screenshots, comments, ideas, suggestions to radiogram at voanews.com . 

 

Thanks for listening and decoding.

 

Kim

 

Kim Andrew Elliott 

Producer and Presenter

 

VOA Radiogram

radiogram at voanews.com

http://voaradiogram.net

Twitter: @voaradiogram

 

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