LX reception (FM - analog TV) - blocked by storm(s)

[kfbkfb]

An unusual reception issue happened to me in the very early 1980s - AFAIK, due to a storm moving thru between the (north of me) TV and some FM transmitters and Iowa City IA, reception was blocked (just static, as if there was no signal) for WMT TV 2, KWWL TV 7, KCRG TV 9 and KQCR FM.

At the time, there was a outside antenna on the roof of the house which provided clear reception at all other times, I also tried the car radio on FM and noticed only static when tuned to KQCR FM.

(there was nothing in the news the next days about a power failure during that time in the areas where these transmitters are)

Anyone else had "local" (IIRC, these transmitters are ~50 miles north of I C IA) FM/TV reception completely blocked by storms?


Kirk Bayne

 

[Kelly A]

Anyone else had "local" (IIRC, these transmitters are ~50 miles north of I C IA) FM/TV reception completely blocked by storms?

The phenomena is known as: 'atmospheric ducting: What is Duct Propagation? Definition and Mechanism of Duct Propagation - Electronics Desk
It isn't that the signal is being blocked. It's actually being carried over the intended viewing/listening area by thermal conditions.

 

[seattlesarchiebunker]

As a young’un growing up in the southeastern US, about 40 miles from a large city with a fair amount of class C2/B stations, I’d notice they’d be unusually scratchy (at best) or replaced by stations on the same dial position 100-300 miles out. It always seemed to be mid-late afternoon or early-mid morning when these events occurred.

As I got more involved in radio (and DXing), I found out those events are “tropospheric propagation” or tropo for short. The signals are pushed up to 15-40,000ft and then out. Signal goes further, but can have a tough time locally

Layman’s research showed me that higher stations with lower wattage were far more affected than lower height, higher wattage stations. It is also far more likely to occur the further south and east one goes in the US. I have experienced exactly two tropo events on the west coast in being here for almost a decade. I’d notice 1-2 tropo events per week during the summer in the South.

E-skip I noticed is far more storm-based than tropo skip, however. The only commonality I have seen in tropo propagation is warm-ish, very humid weather.

 

[kfbkfb]

I'm reminded of another unusual TV reception event in the same house with the same outside antenna (happened in the late 1970s):

One late night, I decided to try the UHF tuner in the Sylvania TV to see if I could get TV 40 from Dubuque IA in Iowa City IA (one of the few UHF signals in IA at that time), for some reason, that night, the UHF spectrum was full of TV signals (I'm not a DXer, I didn't write down any call letters).

Reception was fair for the UHF channels, but they would fade out after a while.

I haven't checked to see if there was some weird weather system in the USA overnight sometime in the late 1970s that would cause this (even w/Google et al., I wouldn't know how to look up such a thing).


Kirk Bayne

 

[SomeRadioGuy]

Anyone else had "local" (IIRC, these transmitters are ~50 miles north of I C IA) FM/TV reception completely blocked by storms?


Kirk Bayne

Uh yes.. *raises hand* the slightest bit of a solar storm will cause my semi locals, 10 to 50kw in anchorage or fairbanks 250 miles away which are completely listenable here when its dark... to completely disappear

KCAM 790 with 5KW from 315-320 miles away sounds real good at night when theres no solar upset. But when the solar stuff pukes up, it disappears. Here's audio: https://drive.google.com/file/d/1K75qEVUyN_XaS0Sk8WFs3K6M2KHKKgf9/view?usp=sharing

 

[Tim from Springfield IL]

I'm reminded of another unusual TV reception event in the same house with the same outside antenna (happened in the late 1970s):

One late night, I decided to try the UHF tuner in the Sylvania TV to see if I could get TV 40 from Dubuque IA in Iowa City IA (one of the few UHF signals in IA at that time), for some reason, that night, the UHF spectrum was full of TV signals (I'm not a DXer, I didn't write down any call letters).

Could some of the Illinois and Wisconsin U's that existed in the late 70s had been possibilities that night? Peoria on channels 19, 25, 31, and 47; Rockford on 17 and 23; Madison on 15, 21, 27; Chicago (definitely 20, 26, 32, 38, and 44 existed in the late 70s, not sure about the others); and Milwaukee (at least 18 and 24 before the Quad Cities channels signed on at those channels in the 80s, not sure about the others). Maybe even Springfield, IL on Channel 20. Plus whatever UHF repeaters for Iowa Public Television that were already on the air by the late 70s. Maybe even KMEG-14 Sioux City? Could those channels have been possibilities you saw that night?

 

[kfbkfb]

Certainly possible, I didn't know much about DXing (I sometimes listened to WLS-AM 890 back then, the local WSUI-AM 910 [we sometimes called it "the blight" because it made WLS hard to hear] made that rare though).

I didn't know how to look up info about UHF TV stations, it's just something unusual (RF related) that happened w/analog OTA TV (KC had 2 UHF stations in the late 1960s/early 1970s - TV 50, then TV 41 [which I watched Lost in Space reruns on daily], which I watched using a UHF loop antenna).

I must have used an indoor UHF loop antenna (probably free with the TV) because the twin lead from the roof antenna was only connected to the VHF antenna input.


Kirk Bayne

 

[vchimpanzee]

I remember seeing TV stations from Texas and Louisiana on Channel 2 in North Carolina in the late 70s. I could pick up a station at Channel 2 in the area where I lived. The problem was worst around the time Skylab fell back to Earth.