Author Topic: Display backlight and self-interference due to PWM  (Read 1602 times)

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Offline miraculon

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Display backlight and self-interference due to PWM
« on: August 04, 2013, 08:31:36 AM »
I have read on the main Blitzortung forum about the PWM dimming for the display causing noise that can trigger the dreaded interference mode. This morning, I noticed that my station fell off of the "participants" list (they seem to cut it off at 13 stations despite numerous pages). It had been in interference mode for some period of time.

I reduced the gain right away and normal mode returned.

I decided to try 0% PWM based on one posting. (in the comments area
2013-08-01, 23:03
). I haven't upgraded the firmware to v2.3 yet that shuts off PWM for 100%.

I put 0% after 60 seconds in the display control option. I was able to return the threshold back to the default 120mV, and increase the gain to 10x2(x40).
It is now staying in "normal" mode and my participation rate is back on the chart and climbing. (it just went past the original 6.8USB station as I write this).

Greg H.

Blitzortung Stations #706 and #1682
CWOP: CW4114 and KE8DAF-13
Amateur Radio Callsign: KE8DAF

Offline Cutty Sark Sailor

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Re: Display backlight and self-interference due to PWM
« Reply #1 on: August 04, 2013, 09:24:23 AM »
Greg, I've noticed no issue with the LCD, but I do know I'll be in interference mode with any storms within 200-250 miles at my 'normal'. Running, as now, with 10*10 at 105mv, and the relatively calm environment, I'm up there in efficiency, but I'll have to back down to 8*8 120/130, at least, probably on CH B (E/W) as those Kansas/Mo storms move near the MO/Il/KY line and into KY. I'm only running ferrites.

Here's some observations from last night. First, I'm about 38/-84.
Last night I was free to monitor a small storm developing about 20-30 mi East, and had the opportunity to monitor interference mode from both channels as it drifted south, and developed into a thin line about 80 miles wide as it moved south... at a distance of 50 mi S, ch A (N/S) was backed down to 4*8 at 140, while B (E/W) was back at 10*10/130... and as it moved into TN, (180 or so miles) B was holding fine at 10*10/120, and I was able to get A up to 8*8/120 when it moved well into TN. 200<250mi.

Interesting enough, I've confirmed strikes S to 10, west to 108-109, North to 50+, but have a had a hard time getting past 65-70, which goes a long way toward validating my "Thor's HSJ" hypothesis... for awhile yesterday, I was only cutting a 500 800 mi radius, generally, in Normal Mode with strong clusters between me and further cells, but  confirming stikes with no problem south of Yucatan, etc, and up into Saskatchewan and Montana with no in-between activity.

Central KY looks like a pretty good location, overall, for East of the Continental Divide detection, and I may very well stay with the ferrites.
« Last Edit: August 04, 2013, 09:27:09 AM by Cutty Sark Sailor »