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Messages - redhat

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1
Just leave bad enough alone.  In the long run the AM band will fix itself.  Non-viable stations will cease operation.
Viable stations in order to stay viable will have to offer programming that well serves the "public interest, convenience,
and necessity" (what they should be doing all along).  In other words, the market will fix itself.  In the process, there
will be fewer stations in the end.  Hate to see any station go dark but if it means better programming and less
interference, so be it.

THIS!

+-RH

2
The RF Workbench / Re: 100W Linear PA for the FM Band
« on: October 15, 2020, 2228 UTC »
Sorry for the delay, I'm on the road this week.
 Finding a commercial amp in that frequency range and power level is one thing, something rated or capable of linear operation is near impossible.  You could try a conventional class B/C amp and turn up the bias and see what happens.  I looked at some of the TV fets, and they recommend somewhere around 1.5-2A per fet.  With 50V of drain, that's about 200W of static dissipation!  With a push pull circuit, I'd try between 0.5-1A of bias (1-2A total) and see what the intermod looks like.  I'm not aware of any COTS amplifiers for this level, although a SD2942 pallet would be a good place to start.  Not cheap, about $400 US, but I do know that particular fet is used in Digital FM band transmitters in class AB linear.

+-RH

3
The RF Workbench / Re: 100W Linear PA for the FM Band
« on: October 09, 2020, 1754 UTC »
Although the datasheet specifies linear operation, there is no recommended operating conditions for such, and none of the reference designs are specified for linear operation either.  The problem with doing something like this is the intermodulation products can become very large.  While this may not be a problem for the levels you are proposing, it still can cause a lot of interference to other band users.  I assume the idea here is to broadcast multiple stations across the dial with one transmitter?  I would probably look at a larger device, perhaps the MRF300AN, possibly in push pull.

+-RH

4
Part 15 AM and FM Station Operation / Re: Part 15 EAS kinda
« on: October 05, 2020, 2348 UTC »
...Or you could buy a TFT EAS 911 on ebay for $100 and feed a weather receiver into it.  They are no longer type accepted for broadcast station use, but will still decode the FSK data encoded in EAS messages.

+-RH

5
The RF Workbench / Re: Watch out for those cheap components
« on: October 05, 2020, 1807 UTC »
WOW!  This is a big reason why I only buy parts from reputable vendors.  Ebay is a crap shoot in that regard, especially with IC's

+-RH

6
..Personally, I still think using AM would be the better option for both Wa!mart and the churches. I wonder why they continue to focus on the FM option.

Because the AM in a modern car sounds like sh*t, and some don't even have it.  That coupled with the finicky nature of most LPAM antennas verses the 'set it and forget it' nature of a small FM setup.  I suspect the folks running these things are not engineering caliber people.

+-RH

7
You can get the same thing for less money from Balun Designs https://www.balundesigns.com/4/  I've used their 1:1 feedline chokes on all my verticals and dipoles, which solved most of my RFI issues.  DX Engineering makes good stuff, but it tends to be expensive for what it is.  Their sales staff also leaves something to be desired.

+-RH

8
Part 15 AM and FM Station Operation / Re: FCC vs God
« on: September 22, 2020, 0522 UTC »
I was later dismayed to find that local pastors prefer to hold services as usual, in spite of the risks.

Of course, much easier to guilt a donation out of a captive audience.

+-RH

9
I don't get it.  Is it really above the intelligence of the average soccer mom that drives one of these things to plug it in at night?  Wireless charging is horribly inefficient, and you think the point of all this in the first place is reducing one's energy footprint, not broadening it.

+-RH

10
Huh? / Re: Julian Assange arrested by UK police...
« on: September 15, 2020, 1254 UTC »
Hard to take the Brits seriously until they start driving  on the correct side of the street and lower their beer temperature another 10 degrees F.

+1

+-RH

11
The RF Workbench / Re: NOT A Replacement For Your Stretchy Audio Amp
« on: September 13, 2020, 2126 UTC »
It has crossed my mind, easy enough to drive a photocoupler/fet driver combination.  Then the sky is the limit, power wise.  Much cheaper too than a lot of the other solutions out there.

+-RH

12
The RF Workbench / Re: NOT A Replacement For Your Stretchy Audio Amp
« on: September 13, 2020, 1745 UTC »
Ya know, a lot of the problems with these amps stem from the use of a transformer in the first place.  Why not double the supply voltage, eliminate the transformer and drive the PA direct from one side of the audio amp IC?

I made a thread about this some time back...  https://www.hfunderground.com/board/index.php/topic,40717.0.html

*edit* I forgot that this is a 40W TX requiring 48V peak mod, and have not yet found an COTS audio amp IC that will run at that supply voltage.  Might be time to build a simple PWM modulator?

+-RH

13
General Radio Discussion / Re: Allan Weiner buys WHRI
« on: September 06, 2020, 0154 UTC »
"...I think he summed up intended programming for the former WHRI frequencies by saying...."we will continue to spread HIS word." Also in the final few minutes, he complained mightily about electric rates in Maine, perhaps a hint that the WBCQ operation will be heading south?

Sadly it's about the only format left that is self sustaining...that or conspiracy talk.

+-RH

14
Huh? / Re: Is Bomar Crystal the last one in USA?
« on: August 18, 2020, 1503 UTC »
It should be noted that Bomar does not make crystals.  They job shop their work to places overseas, which is why one-offs take 6-8 weeks to be made.

+-RH

15
Equipment / Re: The Best Active Loop Antenna 2019 = MLA-30?
« on: July 27, 2020, 0725 UTC »

...It could be set up as horizontal for omni directional antenna, but most BC stations on HF seem transmitting on vertically polarised antenna. But one could do some testing on that to figure out which polarisation works better.

FWIW every curtain antenna I've every seen at a shortwave broadcast station was horizontally polarized.

+-RH

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