Help needed in Fine-Tuning SSTV on ISS

Miles WF1F of MAREX-MG has requested help in the fine tuning of the Amateur Radio Slow Scan TV (SSTV) system now operating on the International Space Station (ISS).

In an email on the AMSAT Bulletin Board (AMSAT-BB) he writes:

We need your help in fine tuning the SSTV system on ISS.
Here is how you can help.

VOX Delay:

There is an intermittent problem with the VOX box that controls the transmitter switch on the radio. When the VOX hears sound coming from the Laptop, it will turns on the D700 Transmitter. When the sound stops, the transmitter should shutdown in 2-3 seconds.

We need you to listen to the end of the SSTV signal and time the delay.

Suggest you also Audio or video tape record the sessions so we can get accurate timing values.

The first question is:

How long does the Transmitter stay keyed after the end of an image?

What is the slide show delay set for?

I have requested it be set for approximately 5 minutes for now, until we make sure we are not driving the transmitter too hard. We do not want the radio to over heat.

Audio Levels:

For those of you that are experts in SSTV, please try to guess the Audio levels of the Down link.

Is the audio too high or too low?

If we turn the Audio level down a bit, we may be able to reduce the number of VOX hangs.

Slant Adjust:

The Downlink SSTV slant adjustment has not been set on SpaceCam1. We the experts familiar with Adjusting SSTV slant, to Audio record the Images coming down live and play those images back into your system and see if you can calculate the slant adjustment value.

Since SpaceCam1 is based on CPIX, you should be able to use CPIX as your test bed and calculate the slant correction factor.

Other Tuning Suggestions Welcome.

Sincerely

Miles WF1F
Marexmg.org

Send your data and image to:
sstv@issspacecam.org

AMSAT Bulletin Board AMSAT-BB
http://www.amsat.org/amsat-new/tools/maillist/

MAREX-MG
http://www.marexmg.org/