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Messages - redhat

Pages: 1 [2] 3 4 5 6 7 8 9 10 ... 106
16
General Radio Discussion / Re: DaveP passes
« on: April 27, 2023, 0040 UTC »
Dave was a good guy.  We had many exchanges over the years about his not-so-low-power AM he ran at home, and other projects.  He will be missed by all of us.

+-RH

17
General Radio Discussion / Re: Song Info TX mode
« on: April 08, 2023, 0546 UTC »
I would run PSK31 just outside of your audio modulation.  If your running AM, you can simply inject PSK31 into the baseband audio just beyond your program audio bandwidth at about 10% modulation.

I assume the purpose of this is to provide a similar service to RDS on HF?

+-RH

18
The ones I have are DROK or a clone off amazon, and they work fine up to 15-17W carrier and don't cut out until you hit 29VDC input.  The PA's I run are around 10 ohms at the DC input.  The small boards seem better than the larger ones.  I bought one of the larger 100W amps, and upon closer inspection found it had a small IC in it from a LCD TV, which also didn't pass DC.  Caveat Emptor indeed.

+-RH

19
Peskies / 6300 USB Arabic 0135 UTC 17 MAR 2023
« on: March 18, 2023, 0137 UTC »
Hearing Arabic sounding speech on 6300 USB.

+-RH

20
The TPA3116 amplifier boards and their clones seem to work well.  Tie the positive outputs together, and add a solder blob to tie the wipers of the pot together.  This will ensure that outputs are as close to the same as possible, so one channel doesn't fight the other.  Seems to be good to 15W or so.

https://www.ebay.com/itm/284160314693?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=hksnm2-7qz6&sssrc=2047675&ssuid=XS3HxYCuQ6C&widget_ver=artemis&media=COPY

+-RH

21
The RF Workbench / Re: Redhat's LULU build attempt
« on: February 25, 2023, 0722 UTC »
"clean desk, empty mind."

+-RH

22
Good signal into the MI Kiwi with 10KHz audio and some bright jazzy music.

Thanks for the show!

+-RH

23
Most of these papers were done under the tenure of the original owner and are years old.  The owners' kid is now running the place now, and working quickly to take AM out of the firms' portfolio.  In some ways its sad to see such a giant of the AM hardware business move away from their core model, but I suppose that's the way it goes.  You have to evolve or die.

+-RH

24
The RF Workbench / Re: Redhat's LULU build attempt
« on: January 21, 2023, 2251 UTC »
The differences are subtle but a grenade style PA is not class E.  It was never optimized as such.

+-RH

25
The RF Workbench / Re: Redhat's LULU build attempt
« on: January 17, 2023, 1804 UTC »
The online calculators to determine component values are all fine and good*, but you have to understand that the models can't incorporate PCB parasitics because the the parasitic values depend upon the PCB layout, the PCB  materials, the choice of transistor, the packaging of the transistor, etc. They work OK as starting points but there will be refinement later. This is why I recommend the "driving a car in deep snow" method: https://www.hfunderground.com/board/index.php/topic,92791.msg297947.html#msg297947 Make your first try, figure out how far off target you are and then make course corrections to get closer to the goal.

And, yes, as I heard you say in the video, Class E can be very picky about component values on the matching network. Whatever values you come up with may be suboptimal for someone else whose "hand-carved PCB" technique is a little different from yours. This is one place where a manufactured PCB may be helpful since it is likely to be more uniform from batch to batch, though that is not guaranteed either. (FR4 Er can be all over the map.)

Unless I missed it, you didn't show what the drain waveform at the frequency where the power output peaks (~5500-5600 KHz?). If the drain waveform looks kinda/sorta OK there, then I think your problem is simply a tuning issue

Yup, no argument there, and its one of the things I neglected to add into the dialog.  As I mentioned in the video, its easy to get tunnel vision and forget simple but important things.  This was more of a 'hey, lets try this and see if it works' kinda thing.  Appreciate the comments!

+-RH

26
The RF Workbench / Redhat's LULU build attempt
« on: January 13, 2023, 1546 UTC »
From an edited version of last night's live stream, watch for two painful hours me build my version of the LULU.  This is just the initial build without optimization.  Schemo's and BOM to follow once I get everything dialed in.

https://youtu.be/Mme7L0eR954

+-RH

27
General Radio Discussion / Re: has anyone ever thought about...
« on: January 05, 2023, 0654 UTC »
If you have a cool idea for a show, and you just want to get it on the air, contact a couple stations and ask.  The worst they can do is turn you down.

Myself and other stations have done relays for folks in the past.  Hell, that's how we got our start.

+-RH

28
General Radio Discussion / Re: WBCQ 7490 Transmitter Off Air
« on: January 05, 2023, 0638 UTC »
Wow, so there IS a God !  :)

It would have been better if it stayed on air, because now the political and religious programs are being mixed with the entertainment programs on 5130 kHz.

What's the difference?  It should all be viewed as entertainment, or comedy.

+-RH

29
Sounding good on OH SDR at 0238 with Crowded House's 'World Where You Live'.  Happy New Year WDDR, glad to hear you again :)
Sipping some Solerno blood orange liqueur here.
0250 OM on the mic, letting the music play, into Janis Joplin.
0300 Thanks for the shout, bud!
0310 OM on the mic, into DEVO 'Working In A Coal Mine'  Love it!
0323 OM on the mic into RHCP's 'Dark Necessities' Love it!
some SSTV, and other nice tunes.  REM Orange Crush now at 350z.
0451z OM with music backsell, Oingo Boingo 'Just Another Day' into Gladys Knight & The Pips 'Midnight Train To Georgia'

Thanks for the show tonight, helping me beat the blues!

How about a song I first heard on one of your shows, 'She's come undone' by the Guess Who....THANKS!!

0510z Some DJ patter, mentions of myself and requests.  The song starts and stops...glad that doesn't just happen to me :)
Thanks bud and Happy New Year!

+-RH

30
One of these circuits appears to be a modulated power oscillator, meaning the operating frequency would likely change based on antenna loading changes, and with modulation...poor man's FM.

Yes and I'm going to expand on this a little:

Transmitter have several operating functions inside them. Examples are, an oscillator (a VFO is one such oscillator), a final amplifier and perhaps some amplification between the two of these, perhaps some sort of power supply (e.g., 'bias") circuit. All those functions have to be present and operate well separately from each other; this implies a level of isolation and is critical for proper operation. If the different functions interfere or interact with each other too much, bad things can happen like muddy/mushy modulation, FMing or frequency shifting with modulation, oscillator drift,  feedback (instability), operation at unintended frequencies and so on.

The best way to ensure a certain amount of isolation is to make separate oscillator circuit, a separate final amplifier circuit, separate power supply circuit and then the designer will weave them together so that they all "play nicely" with each other.

The single tube/valve transmitter shown doesn't have any of that isolation between circuit functions; it does all the functions in one circuit and so it is prone all the issues I mentioned above. So why do it? Having those functions in separate circuits adds complexity, expense and time to build. For a hobbyist, convenience may override all those other considerations.

Yes, this precisely.

+-RH

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