AM time-brokered stations powering down

[K.M. Richards]

Unfortunately, no. Even mono FM uses 75us pre-emphasis, which an AM Volumax had no “awareness” of. It would make a terrible peak limiter for any FM. It was the pre-emphasis control section they added that made the FM Volumax what it was, and it was pretty OK right up until the Optimod 8000 seriously kicked its butt.

Okay, I think that is what I was remembering ... the FM version of Volumax at the studio and an Audimax at the transmitter.

 

[sasha23]

"...they (WKTA) had been on the air (and are licensed for) 24 hours, with a nighttime signal was too strong for their 110 watts."

> definitely out where I live, in the Bartlett area, it sounded more like 500 watts or 1kW (this was several months through the last winter)

"It's been a year and a half since WRDZ-1300 in suburban La Grange lost their transmitter site and has been silent."

> from what I can tell, this is not happening, an STA, nor a new/diplexed facility. I emailed the president of Polskie Radio, about the status of 1300 - never heard back.

 

[AMRadioGuy]

Okay, I think that is what I was remembering ... the FM version of Volumax at the studio and an Audimax at the transmitter.

The Audimax was the same, whether for FM mono or AM. It was the Volumax that was different. The Audimax always came first, as it was the AGC to smooth out levels and feed the Volumax with a consistent average level for consistent limiting.

The Audimax would be at the studio, feeding the STL (whether a Marti or an eq'd phone line, etc.) and then the Volumax would usually be the final unit feeding the transmitter.

With the 2-rack white units, you could gang two Audimax's together for stereo operation. Same with the FM Volumaxes. They actually had a special connecting cable to gang them together. The 70s single-rack units were just configured for stereo or mono.

 

[davideduardo]

Unfortunately, no. Even mono FM uses 75us pre-emphasis, which an AM Volumax had no “awareness” of. It would make a terrible peak limiter for any FM. It was the pre-emphasis control section they added that made the FM Volumax what it was, and it was pretty OK right up until the Optimod 8000 seriously kicked its butt.

It was easy to modify the original Volumax units (white, two rack units) for FM pre-emphasis; it was entirely built with discreet components and the boards could be modified.

 

[davideduardo]

The Audimax would be at the studio, feeding the STL (whether a Marti or an eq'd phone line, etc.) and then the Volumax would usually be the final unit feeding the transmitter.

My first AM station STLs were a lower power FM back when FMs were not licensed for independent commercial use. The Audimax units fed the FMs, and they were received on fixed frequency receivers at the transmitter where each had a Volumax.

The STLs were all about 100 watts. First, I used a trimmed CB antenna, and then used a trimmed Ch 7 to 13 TV antenna to be directional for one AM site that was over 25 miles from the studio with no true line of site. The FM transmitters were built in house..

Later, in the U.S., I never used Marti STLs. I'd always use the hot standby Mosely units at each end.

 

[K.M. Richards]

I give up trying to remember which was which at my old station. It's giving me a headache. 😖 And besides, it was 50+ years ago.

Thanks to you all for trying.

 

[dc2bluelight]

It was easy to modify the original Volumax units (white, two rack units) for FM pre-emphasis; it was entirely built with discreet components and the boards could be modified.

Well, that depends on what you call "easy", and what results you hope for. Sure, you could add pre-emphasis somewhere around the input amp, then de-emphasis around the output, but that's not going to work well. The FM units included two additional cards, one was a second AGC card, the other an entire board for high frequency control. You know, rather than modulate the entire broadband gaing based on pre-emphasized audio, you modify the pre-emphasis dynamically. I have to say just adding pre-emph/de-emph to a 400 wouldn't really do the job.

 

[1KW-SDR Fan]

I just saw a post about WNDZ 750 AM, on another site. Do you think they're done? What will the rest of the year bring for stations like WNDZ? I find it interesting how, all of sudden 1330 and 1430 power down at night. I remember (until 2-3 years ago), at least 1330 was on (full power) at night. During the winter, I heard both 1330 and 1430 at night (or all day). 1510 is still around, so is 1570. I find it amazing how those two stations are still going strong. What will the AM dial (in Chicago/suburbs) be like within a few years?