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Messages - Charlie_Dont_Surf

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1
Listening on a NY SDR. SINPO 55445 at 0010 UTC.
I'm busy with something else so no "play by play" from me but I wanted to let you know that I am listening.

Very nice (new) audio configuration, 8 KHz wide.
0045 - Now that I have been listening for over 30 minutes, my perception is that I think that I hear some clipping/limiting distortion on the bass frequencies.
0057 - Seems better but it might just be because of the songs being played.
0110 - I was right and DJDW is tweaking things as he goes along. The bass distortion is fixed, comrade. Very nice - but not thumping - bass. Without splitting hairs, if you wanted to add a little bit back in, that would be OK too but just a little.
0114 - Momma?



2
Station ID = Robot 36?

No, that's the format of SSTV transmission used.

3
Just above the noise on a Kiwi in New England.

0017 - ZZ Top? Gramps says Motorhead. OK.
0022 - SSTV
0023 - Motorhead

4
The RF Workbench / Re: Radioberry Transmitter
« on: July 05, 2024, 0011 UTC »
Yes, Radioberrys can generate SSB so generating AM just means a different equation in a line of code. As an ex-boss liked to say, "It's all just math, man."

The efficiency is a different matter. If you insist on having a multimode solution then a Radioberry could be the ticket but be prepared to deal with heat from the final amplifier. For my money a dedicated AM solution with a class D/E/F/J final and high-level modulation is likely going to be hard to beat.


5
The RF Workbench / Re: Low-cost RF synthesizer uses generic ICs?
« on: July 04, 2024, 2359 UTC »
Since we are all piling on with more modern alternatives (which might not be the point), I will wade in with:

https://www.qrp-labs.com/vfo.html

and

https://www.qrp-labs.com/progrock2.html

6
I haven't used breadboards since the early 90s (perhaps it was earlier) but I'm going to say that proper layout for good isolation of I and Q would be the priority. Redhat's -40 dBc seems reasonable to expect. At those frequencies we can get ~-60 dBc or better in much more compact areas but with optimized layouts.

7
2340 - Signoff to fix the "problem".

It actually sounds OK  to my ears right now, except for some AGC pumping noticeable on your mic audio (fan noise comes up between sentences) and a peskie on 6930 LSB (which is out of your control). I don't remember your signal having "pumping bass" in the past so I'm not sure what you are missing.

8
In fact there are two commercially available QRP transceivers, the uBITX and the sBITX from HFSignals.com, that use the IRF510 in the finals and these transceivers can be used at 10 meters.

The IRF510 is the lightest load (in terms of Ciss and Qg) of the IRF and IRL series of transistors, closely followed by the IRL510, and they are very cheap because they are very old. I believe that they were released in the late 1980s. The IRF510 typical Ciss (180 pF) approaches that of many lower frequency RF transistors I have seen so it would be interesting to see how high they can be pushed.

Difficulties:
  • The IRF510 is not characterized for HF or VHF operation so you would have to either make some assumptions (read: guesses) for small-signal parameters for the matching design at those frequencies, measure them yourself or just tweak your amp forever until you are happy.
  • The transistor package (TO-220) is quite high inductance by modern standards for 100 MHz.
  • Finally, because the transistor is not intended nor characterized for operation above maybe a few MHz (probably less), that means that the manufacturer is not keeping an eye on  parameters that matter for RF performance over the manufacturing lifetime so certainly not looking at things like transconductance at RF, Cgd, Cgs, etc., thus the batch lot-to-batch lot variation could be much more than you think. You might build one amp and it will be fine then build another one a year later and can't get it to work well at all.

9
https://www.pa9x.com/pep-power-and-duty-cycle-in-amateur-radio :)

While he's not wrong in his basic points, in fact the duty cycle is actually more complicated than his table implies since the duration of an FT8 transmission is always ~12.5 seconds of on time (and FT4 is always ~4.5 seconds) but an AM or FM transmission often is much longer. FM will be "constant envelope" (no amplitude variation), FT8/4 can be close to constant, but AM will necessarily not be constant envelope and power output at 100% modulation will be four times the carrier power, i.e., the power with no modulation.

The overall time scale matters to the heat build up in the PA, baluns, tuners, etc.

10
Amateur Radio / Re: Dumb question RE FT8
« on: July 04, 2024, 2255 UTC »
A couple more things to add:

As implied above the computer sound card acquires the entire 2700+ Hertz of bandwidth at once and processes it all at once. Decodes of the whole bandwidth are essentially instantaneous. The computer has much better dynamic range than the human ear & brain so FT8 is generally much better at low signal to noise ratio work than even CW and certainly you can pack more FT8 signals into a small space than you can CW signals. The signal to noise ratio requirement of FT8 is low enough that if there is even a glimmer of hope of any amount of propagation, you will probably hear some FT8 since it can work when conditions don't permit other modes and there are enough people using it now.

There is a lot of fancy math involved in the underlying basis for FT8. Fortunately the guy who came up with the idea is Nobel Prize winning physicist. Dr. Joe Taylor (K1JT) won the prize for his work on pulsars but he borrowed on a lot of work created for communication with deep space probes (which necessarily communicate over low signal to noise methods) to come up with the techniques. He is an EME (moonbounce) enthusiast and FT8 has it's origins in that area.

The theoretical bandwidth is around 50 Hz, as noted above, but that's only a good approximation of how much space you should leave to your neighbors. Yes, we do "step on" each other often but if both signals are strong at the receiver, it will work out, depending upon how much overlap there is. On the other hand if one signal is much weaker than the other and there is complete or sometimes only partial overlap, the weaker signal is pretty screwed. That's why we generally leave about 25 Hertz on either side of center and that seems to basically work. (Of course, not everyone hears everybody else so you can still get stepped on.) With a 2700 Hertz "swath" to work with and each transmission using 50 Hertz, that allows for 54 frequency "slots". At very busy times, for example 20 meters in the North American evenings, I have seen approximately 50 simultaneous signal decodes filling up my computer screen many times.

To get a feel for the flow of FT8 (or FT4), you can use any Kiwi SDR on the internet, turn on the FT8/FT4 decoder (in the pull down menu under "Extensions"), select the band of choice, sit back and watch.

Yes, people still use JT65 on HF. Sometimes those guys intrude into the upper ends of the FT8 area and wipe others out.

11
Very listenable on Weston-Super-Mare, SINPO 34333. Some distortion on audio peaks.

0935 - The Specials, A Message to You Rudy
0940 - Reggae ID: "I love Radio Pamela."
0944 - Live air check. Previous song was from The Specials. "Next song is from Bobby Bloom, Montego Bay".
0949 - Recording: https://voca.ro/18Effli6GF0y
0951 - Recording: https://voca.ro/1511xDgY1clO

I'm going to bed. Good night/good morning, all.


12
0415 - Banjo plucking audible in CA. Nothing on the Northern Utah SDR with log-periodic pointed east.
0418 - Dialogue by two males over banjo plucking.  I heard one of the two males say, "I know that feeling."
0422 - Seems a replay of the Poncho Villa show heard on AM a few minutes ago (Trump sarcasm) but nothing heard on the W0AY SDR in Montana so seemingly a different TX.
0426 - Fart noises included in the dialogue.
0428 - Song: "Sit on my face.."
0428 - Same ID and email address (yahoo) as heard on AM a few minutes ago.
0430 - "Fake news all the time", into SSTV but I wasn't ready with the decoder.
0431 - Seemingly off.

13
0405 - Skit satirizing Trump and this trial.
0408 - ID: "Voice of Poncho Villa" with email address.
0409 - TX off.

Very localized reception. Great reception (under the circumstances) on the W0AY SDR in western Montana but almost nothing on the SDRs I could get to in Washington state, Oregon, British Columbia and Alberta.

14
S9 with the K1VL KiwiSDR.

0250 UTC-Music

Did you get an ID or is this presumed? I admit that it sounds like them, to the extent that I can tell through the heavy polar flutter.

I heard what sounded like an MRI ID

OK.

15
To the extent that I can tell, which admittedly isn't much, my weather station with a clock locked to WWVB has had no difficulty since this degradation in service.

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