HFU HF Underground
Technical Topics => The RF Workbench => Topic started by: Zazzle on March 09, 2016, 1303 UTC
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Heyho,
Dunno where to start. Just let's say I discovered E-Class amplifiers by "accident" and now I wanna play with it. But since Class-E is only fun when it comes to "more power" [Tim Taylor] I'm going to build a second "Common and Precious" CW Beacon on 40M with *gsssssp* 25W. Some may render me a bit too bold for doing that. But hey, hey, no risk no fun. And 25W sounds a lot of fun to me. :)
I was doing some engineering work with a resonant SMPS circuit when I started to wonder why it shouldn't be possible to use a pulse driven stage to generate clean HF with a proper resonant circuit on the output. Well, after checking some things with Google I stumbled upon Class-E amplifiers. Oh-yes, baby. Which basically ruined my whooole weekend 'cuz I got absorbed in technical papers and formulas.
Since it's going to be pirate equipment and may be prone to get damaged or busted, I settled with a simple setup. I left more space on the PCB for the output stage because that's what I want to tinker with.
- The transmitter generates the operating frequency with a simple TTL-based crystal oscillator (which can be pulled a bit).
- The last TTL-Gate is keyed by an Attiny25 which holds the morse code / identifier that's to be broadcasted.
- The TTL Block is followed by a high-current FET-Driver.
- The rest is obvious. A resonant circuit and just to stay clean (which is important to me) a 7-pole Low-Pass.
The whole thing end up in an small aluminium box with an external (15V/3A Notebook) PSU.
I learned from my last setup that having the transmitter high on a pole sucks rocks because I have to tear down the whole setup each time I need to work on it. This time I go with a transmitter that's hidden under the roof. 25W allow me to lose 2-3W on a long RG-58 cable so I can run the cable in a way that makes it impossible to follow easily and to a place where I can hide the transmitter without any risk of it being found by accident.
So far I got myself all the parts needes. Electronis components, wires for the antenna and poles, paint, wood slants and so on.
I think I make this happen around the easter holidays. Hope the weather works in my favor :)
Question: any reasons against f=6.553,5kHz? I wanna keep it simple and a 6.553,6kHz crystal is chep.
Kind regards,
~Zazzle
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Evenin'
Update. We got a layout!
- Bottom-Left: µC Keyer
- Left-Top: Oscillator and Keying
- Top-Middle: FET Driver
- Middle: PA Stage
- Right: Impedance Matching tarnsformer and Low-Pass Filter
~Zazzle
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Neat! It'd be sweet if you could add some telemetry to it, like ambient temp, barometric pressure, working voltage, a cheerful message, etc.
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Hey Josh!
Neat! It'd be sweet if you could add some telemetry to it, like ambient temp, barometric pressure, working voltage, a cheerful message, etc.
I had thoughts about that two years ago when it was in the making. I agree that those features are a nice thing. Temperature, humidity and alike. In the end I forsaw from adding such. The main reason was, that I didn't want to spend much time and money on features for a projekt that's likely to be vandalised and/or stolen/busted.
Another reason against is based on the fact, that the signal may be received with hard fading. Therfore, I like to keep it short and simple, only containing the basics.
Since the project made it almost through 1,5 years without anyone touching it, I might rethink my decision and add at least a temperature value. We'll see .:)
Kind regards,
Zazzle,
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Hey,
vacation! Hoooray! I found time to etch and populate the PCB. Sadly, I added a Diode reversed which lead to a 5V TTL IC to be fed with 15V. Which it took, of course, not well. But fortuna was on my side and I found a replacement in my spareparts box.
The circuits works and will spend the next 7 days in a metall box in the basement. Burn-in test.
~Zazzle
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Hey,
the test passed without problems. Froze it almost to death and heated it up to 90°C several times. Steady operation. So I'm gonna install it next weekend. As long as the weather stays steady. I'm looking forward to that. :)
Kind Greetings,
Zazzle
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Heyho,
Board after cleanup.
Did some fun-testing:
- 60W Po, 81% effiency.
- 30W Po (nominal value): 86% effiency.
Kind greetings,
Zazzle.
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Hey.
Bite my a$$.
Found time, installed the setup. Of course I had, again, issues with the SWR. I've expected such, given the low frquency, low antenna height and metal based roof construction.
But then, just when I was done with the annoying antenna issue, Murphy decided to join and the 15V Notebook PSU, that powers the whole thing, decided to go FUBAR fo no reason. Yeah, thank a lot.
I still got some more at home, but I wasn't rewarded with a working setup yesterday - after all the work I put into.
So, do it again, Sam.
~zazzle
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Hello Zazzle!
Did you make some tests on frequencies near to 6400 kHz? I have heard slow CW there during short period of time about a month ago. The CW speed has been almost the same as I heard on 10 MHz. I have made recording then, but unfortunately deleted the file and didn't decode it.
73!
Alex.
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Hey!
Did you make some tests on frequencies near to 6400 kHz? (...)
*Looks at the date of your post and his calendar* Yes! Very likely! If it was in the hours around midnight, it's very possible. :)
Funny thing that you happen to caugh me on those few rare minutes where I had it on air. :)
Greetings,
Zazzle
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Phew! What a night!
Finally! I found time (and motivation) to install the Beacon and get it on air.
It's operating on 6.398,5kHz.
To be honest, I wasn't that motivated to spend (again) hours over hours on the roof, trying to get the best SWR. Besides the fact, that the PSU died on me when I was almost done, I also spend too many hours with finding the perfect match with the Balun and Antenna length.
I had the setup installed in my garden before. But due to it's length (almost 22m) I had trouble running the wire Dipole high enough without getting it caught in trees. Back then it got already obvious, that adjusting it will be another pain-in-the-you-know-what.
I tried to fool myself by believing it'd go easier on the roof because there's no trees around and I could work with the already installed support poles. Well, it didn't get that better. Maybe I cut the wire some centimetres too short (well, shouldn't have that much of an effect on 40m anyway) or it's just about the plain fact, that the height of 3m is just too low for the frequency. Especially since the ground is highly conductive. You remember... metal construction.
In the end I put the antenna up and down another 7 times. Until I was that annoyed that I settled with a SWR of about 2.5. Not awesome, but f** it. I got 30W so I can waste some. The SWR-Meter says FWD: 55W, REF: 10W. The Chassis where the MOSFET is mounted to stays almost cool. So. Ehh....
What annoyed me like hell (and made the night one I'll be laughing about in a few months) were those people walking around on the ruin yard. Suddenly, I heard people walking and talking in low voices. It's funny how fast a calm mind switched to paranoia mode. They were just some kiddos walking over the yard but after that every loud noise made me freeze. And, believe me, things that hardly make a noise during the day become quite loud during night. Damn, Duct Tape is pretty loud when it's been unwound. Not to mention all the animals moving in the shrubs near the roof on the ground.
Anyway! It's on air. I could already receive it on two WEB-SDRs
- - Bedfort, England: 05:45 UTC
- - Twende, Netherlands: 05:75 UTC
Greetings,
Zazzle
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Hey,
oh, and this is how the TX-Unit looks like. I'm gonna take photos of the whole setup during day another time.
Greetings,
Zazzle
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Looks nicely executed.
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Hi!
It's amazing, that I have tuned to 6398 kHz at the same moment when you did unannounced test broadcast and received C&P-II even before it's official start :)
The signal is good here at the moment: SINPO = 44444. However, sometimes Pyongyang makes a splatter from 6400 kHz on local evenings.
73!
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Looks nicely executed.
Thank you! :)
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Heyho,
Eh! Noticed a bug in the firmware. It sends "52W" instead of "25W". Lucky me, that I kept the TX-Box hidden on the ground this time. The controller is fittet into a socket, so I can replace it without big trouble.
Also the first reports came in. Made my day. :)
I wonder when the first oversea reports will arrive.
Greetings,
Zazzle,
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I wonder when the first oversea reports will arrive.
Hi Zazzle,
I was able to receive the beacon the other day. I sent you a message with a link to some recorded audio.
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Hello Zazzle, ULX2 let me know about your beacon.
I'm located in New Hampshire, USA and was listening to your beacon starting about an hour before local sunset and your signal was always there but battling with the thunderstorm static. Typically I could copy 30% to 50% of the CW. I have a 200m beverage antenna pointed at Europe (built for 160m but works very well on 48m).
August 25, 2016
2240z s3, noise peaks s7
2315z s4, noise peaks s7 (sun nearly set)
2330z s2, noise s5
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Hi there!
Summertime... always full of activities and I somehow lost track of checking for reports. Mea Culpa.
I was able to receive the beacon the other day. I sent you a message with a link to some recorded audio.
Thank you a lot! I read your mail today. A QSL card will be send out within the next couple of days.
I'm located in New Hampshire, USA and was listening to your beacon starting about an hour before local sunset and your signal was always there but battling with the thunderstorm static. Typically I could copy 30% to 50% of the CW. I have a 200m beverage antenna pointed at Europe (built for 160m but works very well on 48m).
Also big thanks to you. I send you a mail, asking about details and whether you'd like to receive a QSL card as well. :)
Kind greetings,
~Zazzle..
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Hey,
some on-site impressions of the TX-Unit. :)
TX-Unit, hidden under the roof construction (https://dl.dropboxusercontent.com/s/eba2gwwlvroiw9o/CaP-40M-TX_Unit-Hidden-01.jpg)
TX-Unit, hidden under the roof construction - Closeup Wired (https://dl.dropboxusercontent.com/s/ysdq6myj9mryyjl/CaP-40M-TX_Unit-Hidden-02.jpg)
And another closeup of the wired TX-Unit (https://dl.dropboxusercontent.com/s/n87r161ac5b295e/CaP-40M-TX_Unit-Wired-01.jpg)
Kind greetings,
~Zazzle
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Nice pictures, Zazzle, thanks for sharing!
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Is the beacon on 24/7 or specific times ? Will keep an ear out for it. Would be my first beacon to listen for. Guess I should expand my SWL hobbies ; )
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Hey!
Is the beacon on 24/7 or specific times ? Will keep an ear out for it. Would be my first beacon to listen for. Guess I should expand my SWL hobbies ; )
It runs 24/7. And with you being in the area of NY you have a good chance to pick a signal, even if somewhat noisy and weak. From the reports I got so far mostly in the morning hours.
Also, try your luck with the 30M-Band Beacon at 10.237.800Hz. :)
Greetings!
~Zazzle
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https://www.youtube.com/watch?v=kxb8Rr8I2NA&feature=youtu.be
Ciao Zazzle !!!
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Hello Zazzle!
The beacon on 6398.5 kHz seems to be silent. No reception of it for months here.
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Hello Zazzle!
The beacon on 6398.5 kHz seems to be silent. No reception of it for months here.
I knooooooow. And I'm sooooory. :)
But I really felt not for fixing in. The weather was cold and wet until a few weeks ago and I really felt not for it. My worst fear was that the Beacons go stolen or seriously damanaged. Which added to my lack of motivation. The idea of facing time consuming repairs was not appealing at all. Looks like it has been dead since beginning of March.
But I checked last weekend. The mains cable, that runs over the steal beams under the roof is broken in two places. Cut into half. Looks like bite marks. I guess a rat (or other animal) had it's fun with the cable.
Verything else looks fine. Dunno when I'll have time to fix that. Likely at the beginning of next month.
I keep you posted.
~Zazzle
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Hearing your beacon on 6398.46 at 0014z on 19 Jun 2017.
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Hey everyone,
HA! Motivation struck and I fixed everything yesterday. What a beautiful evening. Lovely warm, no clouds and the sunset was just beautiful to watch. I love the look of ruins, flooded with the warm light of sunset.. and "mejestic "Antennas. Feels like reaching out from a secret, hidden world. Ah~ I'm getting romantic!. :)
Anyway. Fixing everything went smooth. I replaced most of the broken cables and renewed the joints with modern conenctors. Looks all nice and ready for some years to come.
In short: this beacon is up again. :)
Kind greetings,
Zazzle,
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Hi,
Status Update: This one is off air. Since about 10 days.
It died along with the 30m band Beacon.
I took the transmitter box with me. Looks like the PA is fried. The Keying works. I suspect that the stray field of a nearby lightning strike fried it.
Kind greetings,
Zazzle
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May they rise again before the fall DX season. They're always fun targets here in the US
I really enjoy reading (and seeing pix of) your stations. Abandoned buildings with power are hard to find!
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Hey,
that was easy to fix. The sealing gave away and the recent thunderstorm with heavy rain introduced water to the circuit. Which it didn't like. The +12V track was entirely corroded away.
Fixed. The Beacon is operating again.
Kind greetings,
~Zazzle
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Hi Zazzle,
great Job. !
I was listening the beacon today from about 19:30 till 20:00 UTC.
2017September12 20:00 UTC 6398,5 kHz
faint but stabil signal, S1 T4 Q3 with moderate fading and noise.
A1A Beacon
JO62SK Common and Precious JO62SK ....
Rec. in Germany JN49AC Loop R1000 QRB 680km
<<a small reception video is available on https://www.youtube.com/watch?v=r-qS3OYh1s4 >>
PSE QSL
73 de DD2DR, Klaus
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First time I've heard this beacon for quite a while. Good copy in New Hampshire, S2 with the noise level S2-S3.
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Hi Zazzle,
great Job. !
I was listening the beacon today from about 19:30 till 20:00 UTC.
2017September12 20:00 UTC 6398,5 kHz
faint but stabil signal, S1 T4 Q3 with moderate fading and noise.
A1A Beacon
JO62SK Common and Precious JO62SK ....
Rec. in Germany JN49AC Loop R1000 QRB 680km
<<a small reception video is available on https://www.youtube.com/watch?v=r-qS3OYh1s4 >>
PSE QSL
73 de DD2DR, Klaus
Arghl. Sorry for the late reply. I read it back then but forgot to anser.
Many thanks for the video. It's alway nice to know where it was received. :)
Kind Greetings,
Zazzle
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Hi DimBulb!
First time I've heard this beacon for quite a while. Good copy in New Hampshire, S2 with the noise level S2-S3.
Oi, nice! It's been quite a whiiiiiile since I got reports from 'the other side'. AFAIK it was in early spring. So it's a seasonal depending connection I guess. Many thanks. :)
Kind greetings,
Zazzle
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Late in the show here, but aren't class D and E just the cat's nose? Only limited by available saturation current. At 80 percent eff. that a swell little AM transmitter at 80/4 carrier power. 20 watts! Did you try amplitude modulating it? Only a cheap monaural amp would be needed. Of course only should be said filtering the output to a close sinusoidal signal would be needed.
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Hi there,
Late in the show here, but aren't class D and E just the cat's nose?
Class D mimics an analog signal by filtering a PWM signal (x-times oversampling equired for quality) though a low pass.
Class E generates a sine signal directly from a rectangular signal that equals the target frequency. Conversion between REC and SINE is done by a CCL filter at resonance.
In the core, yes, in both types convert a "digital" signal to a analog one by filtering.
20 watts! Did you try amplitude modulating it?
I set it to 20W. The shown board is capable of delivering 60W peak carrier from 12V. Likely more with other components. Class E is fairly easy to upscale. About modulation: yes, whatever can supply with with a positive-wing-only-signal works. Some classy monorail amp with the blocking cap on the output removed will do fine. Or some cheap Opamp-Stuff. Or, if you like to stick to "keeping it efficient": some PWM Amp.
Kind geetings,
Zazzle.
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Update. Same issue as here. (https://www.hfunderground.com/board/index.php/topic,21834.msg150901.html#msg150901)
Operating again.
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I may I received it this afternoon since about 12:00 GMT on the UTwente WebSDR. At the time of the image it was around S2-S3 but at the time of posting it's a steady S5-S7
Current propagation conditions from Dourbes
(https://i.imgur.com/G5lLB2o.png)(http://digisonde.oma.be/IonoGIF.secure/DB049_2018102125500_IO.PNG)
Current propagation conditions from Dourbes
I did have FLDigi running but the decoded text wasn't much readable. Not sure if it didn't like the intermittent fading present on the signal
TTMMT XN EEFEHEM GD TT OE T T*IOUH EE*ST 5L T *O IE EKRESE ED PEEFS@WB2EK 5OW AAJMNE<AA>EE2<SK>*TNKCOM E3*A*BA0EPSHTASK*SN6Y<SK>LE5<SK>Y LEM?<SK>IM T*BTM MEHJ
1 I6A*DIAGES<SK> SETAMMII<SK>*ASJECD*SS JIEAS E AM*T *I*SN EIE5 LM ET T*N*US JESK EE MO62SK CMMMONADO*JM A*)EEMO<SK>TEEKMS<AA>MIA*EE
I'd like to say I've stumbled upon these beacons by accident and I love the whole concept and especially your professional execution... Very cool
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C&P-2 is off air today ???
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C&P-2 is off air today ???
Yeah... noticed a lack of reception on Monday. Got sceptical when I didn't hear it today again...
Damage issue. Details can be found here... (https://www.hfunderground.com/board/index.php/topic,21834.msg164040.html#msg164040)