Messages

16

The RF Workbench / Re: Beacon Project "Common and Precious" (OFF air, 10.237,5kHz, 5W)

« on: November 08, 2017, 1100 UTC »

Hey,

baaa. I'm slooooow. Finally found the motivation to uninstall the whole beast and take it home. There's some issue with the seperate amplifier. The screws are corroded. Haven't dealt with that so far.

But I've been rebuilding the dipole.
+ Thicker wire
+ Proper BalUn
+ Adjustable LC impedance matching. (10-15R:50R)

Got a new toy. A55 Zoom Antenna Analyzer. So much fun. :)

Greezings,
~Zazzle

17

The RF Workbench / Re: Common and Precious IV - Construction phase

« on: November 08, 2017, 1018 UTC »

Heyho,

weather has been pretty much.... wet during the last couple of weeks. Not much progress with the Antenna (finetuning) and alike.

I've been working with the software instead. Data acquisition and logging works fine. I've some trouble with the I/O-Ports but that's just a matter of time. Also, the chassis got prepared.

Usually, there's some warm days in December. If things work out I might be able to "deploy" the project then.

Kind greetings,
~Zazzle

18

The RF Workbench / Re: Common and Precious IV - Construction phase

« on: October 03, 2017, 1458 UTC »

Heyho,

Used the sunny autumn weather for some construction works. Ta-daaaa.

Also, all sensors arrived yesterday.

Kind greetings,
Zazzle

19

The RF Workbench / Re: Common and Precious IV - Construction phase

« on: September 30, 2017, 0943 UTC »

Heyho,

after Chris was done planting ideas in my head... I wanna have your opinion on:

Depending on the sun available during wintertime it's necessary to save energy. Which way would you prefer:
- Lowering the TX-Power from 6 to 2 W .
- Adding a delay between transmissions. I.e. keeping 6W but adding up to 1 Minute idle between each transmission.

Well, I got an ADC-Borad for the Raspi. Which means I can also add the Battery-Voltage to the transmission data.


This is the block for RTTY. Too much? Anything of interest I could add?

Code: [Select]

COMMON AND PRECIOUS 4 BEACON
SOLAR POWERED - 24H OPERATION
ALTERNATING CW AND RTTY OPERATION
LOCATED IN JO62SK
1/4 VERTICAL ANTENNA
8W REGULAR POWER
2W ENERGY SAVING MODE
CURRENT TX POWER <TXPOWER>
BATTERY <BATTERYVOLTAGE>
TEMPERATURE <TEMPERATURE>
HUMIDITY <HUMIDITY>


I think that's a tad too long for CW. Therefore I might go with:

Code: [Select]

COMMON AND PRECIOUS JO62SK RTTY AND CW 1/4 VERTICAL 6W TEMP 21.6 HUMID 88 BAT 12.6

Opinions?

Greetings,
Zazzle

20

The RF Workbench / Re: Beacon Project "Common and Precious II" (on air, 6.398.5kHz, 30W)

« on: September 30, 2017, 0909 UTC »

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

21

The RF Workbench / Re: Beacon Project "Common and Precious II" (on air, 6.398.5kHz, 30W)

« on: September 30, 2017, 0903 UTC »

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

22

Software / Re: RTTY protocol help

« on: September 30, 2017, 0901 UTC »

Oooo! OOOOOoo do a binary coded decimal system like what wwv uses!

Noooooooooooooooooo! :D

23

The RF Workbench / Re: Common and Precious IV - Construction phase

« on: September 30, 2017, 0853 UTC »

Hey Chris,

I would like to experiment with milling a PCB using my CNC machine, I understand that is possible - has anyone here tried it?

Milling works well. Depending on the precision of the machine, even with very fine tracks. But it takes wayyyyy longer than etching. An EU-Card (100x160mm) takes up to 5 hours.

Kind greetings,
Zazzle

24

Software / Re: RTTY protocol help

« on: September 29, 2017, 1505 UTC »

Hey Chris!

If you are using a CPU, you could always send a mix of modes, CW, RTTY, and Hell. That would allow everyone to listen, plus you could learn what modes work best under different conditions?

Stop giving me Ideas!

Actually, I could do a switch between RTTY and CW. Can add that without big hassle.
Maybe I'm going to add Hellschreiber later.

Kind greetings,
Zazzle.

25

The RF Workbench / Re: Common and Precious IV - Construction phase

« on: September 29, 2017, 1456 UTC »

Hey Chris!

Zazzle - how are you making your PCBs, such as from the first post in this thread?

Heyho!

Zazzle - how are you making your PCBs, such as from the first post in this thread?

Straight forward.

- Designing a Layout with EAGLE
- Printing on office paper (with a very smooth surface)
- Soaking it with "Pausklar" (some German spray stuff that makes the paper almost transparent but vaporates after a day so the paper goes back to normal)
- Transfering to a PCB with photo positive coating (I use UV fluorescent lamps)
- Developing (NaOh)
- Etching with Iron(III) Chloride solution.
- Cleaning, drying, dilling holes
- Coating with solderable sealing

Kind greetings,
zazzle

26

Software / Re: RTTY protocol help

« on: September 29, 2017, 1409 UTC »

Heyho!

First: thanks for the fast answer!

I'm basically aiming for the standard type of code with is most common/classic. I know there's variations that use plain 7/8 Bit ASCII straight from the table.

RTTY (FSK) uses a logical 0 for the start bit, and a 1 for the stop bit.
Baudot is a 5 bit code, ASCII can be sent at either 7 or 8 bits and there can be a parity bit when it is 7 bits of data (optional).
The switching between numeric and alphabet is only done in the 5 bit baudot mode, and is done as necessary.
No frame markers or anything like that. Very simple. 

So it works like this?

Code: [Select]

(optional leading RYRYRYRYRY)
[1][Letter][0]
[1][Letter][0]
[1][Letter][0]
[1][Letter][0]
[1][Switch to numbers][0]
[1][Number][0]
[1][Number][0]
[1][Number][0]
[1][Switch to letters][0]
[1][Letter][0]
(...)


Unfortunately RTTY is not very robust. PSK31 would be more robust, but obviously more difficult to transmitt.
Have you looked into Hellschreiber?  Since it is copied by looking at the resulting image and the decoding is done in the brain, it is fairly robust even under noisy conditions. Plus is it is a fun and under-utilized mode 

Yea, it requires a higher bandwidth and is therefore more prone to be affected by noise. Sicne I'm almost done with the TX setup... too lazy to rip it apart for PSK31. ^^'
Hell is fun. But actually it requires a waterfall monitor. I wanna make sure it can be decoded by as many people as possible. And CW ist most straight forward, with RTTY the next common.

I'm not entirely sure myself whether I stick to CW with a higher rate or change to RTTY. Since I'll use at Raspi... I can just change it with a few commands

I also learned, which confused me before, that the RYRYRYRYRY stuff at the beginning is legacy stuff to sync the baudrate.

Kind greetings,
~Zazzle

27

Software / RTTY protocol help

« on: September 29, 2017, 1034 UTC »

Heyho.

Gonna write a RTTY Encoder in Perl. I read some documentation but like to ask for some checks and advice whether I understood the stuff properly.

RTTY uses CCITT-2, yes?

It's 5 Bits but for practial use it's 8 bits, yes? (2x Startbit, 5x Code-Bits, 1x Stopbit)

Start- and Stopbit always  red "1", yes?

So, sending "A" is "11 00011 1"?

Switch between the NUMBER and ALPHABET blocks is done by it's own command (and not combined with space)? So I send <^letters> <flag or block switch> <bumbers> <Flag or block switch> <letters> (...)

Is there something like a Frame marker, a head/endblock or something?

Some advice on timing between blocks/transmissions?

Could someone provide me with an example?

Kind greetings,
Zazzle

28

The RF Workbench / Re: Common and Precious IV - Construction phase

« on: September 29, 2017, 1015 UTC »

Heyho,

Stuff happens! Especially this project getting out of hand. :)

Inspiration struck yesterday. I had some spare time before sunset. Which I used to have a walk across the airfield, looking for a suitable place for the beacon. I knew that there are old, unused (wooden) fenceposts all over the field. The initial idea was to install the antenna pole and solar module on one of those. Outside the used field-area. It's a bit problematic. I need a post which isn't inside the used area. But it must not be too close to the edge of the field. There's a small road around it which is frequently used by people for (dog-) walks because the area around is also some sort of park.

It was a good thing that had a look before sunset. I knew that a small part of the airfeld is used to keep sheeps. But there's two more fields (with fences around) by now. More sheeps. And cattle. That could have ended not nice... me stumbling into cattle in the middle of night. It almost made me abandon the field idea. Most of the area isn't usable anymore and I won't dare to install the setup in the used sections.

I kept walking around and my patience got rewarded. I found the perfect spot. It's a larger group of young and older trees which happens to be fenced itself. I dunno why. Maybe to keep the sheeps from eating the young trees. But this section of the field looks like it isn't used at all. The fenced area doesn't stick to the trees but expands a bit on one side. No idea why. I've to examine that. The trees itself are on the side towards the edge and form a rough half circle. It'll shield my setup perfectly against looks from the road. The other side is open and offers enough space for the antenna. Also, the open side of the half circle faces the south side. Excellent for the PV modules.

So, what's new?
- A friend of mine gave me 3x 100W PV modules (friends can be great, can't they?)
- I'm gonna construct a carrier for 2-3 PV modules.
- The antenna post gets expanded by additional 1,5 meters, with antenna at 5,5m above the ground.
- Got used UPS batteries 6x 4.5Ah with approx 3Ah remaining. That's 18Ah and enough.
- Since I have a PI Zero flying around unused (50mA from 12V) I'm pondering to have the beacon also sending temperature and humidity information. I cooooould go with RTTY instead of CW, but not too sure about it yet.
- Since I have so much PV power at hand (wayyyyy too much during summertime, but still hardly enough for winter) I ponder to have the beacon operate at two power modi. Like, 8W with enough charge and 2W in 'energy saving' mode.

Kind greetings,
Zazzle

29

The RF Workbench / Re: About Vpp, Vp, Vrms and P(R)

« on: September 26, 2017, 2259 UTC »

Heyho,

The formula I always use is.... W=(0.707 ( Vpp / 2 )^2 / Zload

That's actually the same way I use. Just a different way to phrase it (0.707 = 1/1,41).

Anyway, I found the issue. It was a bit nasty and tricky to get behind.

1) The probes, set to 1:1 mode,  introduce the full capacitance reactance of the probe lead to the signal. Which is, at 14MHz, 100-200R (depending on the C of the lead). This alone affects the signal.

2) The lead isn't terminated (10M at the Input of the Oscilloscope) so the wire starts to act as a Lecher line, which also affects the signal (transforms the impedance).

Switching the probe to 1:10 made a really biiiiiiig difference. But the reading was still off.

I ran tests with a 40MHz, a 50MHz a 250MHz and a 500MHz Oscilloscope. The bandwidth of all devices were sufficient.

Different probes lead to different readings. Starting from 30Mhz it got better. All below was... way off.

In the end I found a nice workaround that gives good readings:

I mount a 10W dummy load on a BNC T-Splitter which gets directly connected to the Oscilloscope input. A 2m RG174 BNC-wire connects the BNC T-splitter with the TX unit.

So I have the dummy as close as possible to the Oscilloscope input and no line in between that causes isues. Gives proper reading on all Oscilloscopes. 55.6Vss. That's what I wanted to read!

Good night!

~Zazzle

30

The RF Workbench / About Vpp, Vp, Vrms and P(R) [solved]

« on: September 25, 2017, 2252 UTC »

Heyho,

I need a slap onto the back of my head so the bits fall into place. Also, yeah, asking this is kinda embarrassing. I feel stupid. Google doesn't really help here. It all says that my instruments are wrong.

The Oszilloscope (actually five) says Vpp=30V. The Wattmeters says ~8W. I say 'eh?'

If I'm not stupid, then "calculating P on 50R from VPP" works like this:

Code: [Select]

Vpp / 2 = Vp
Vp / SQRT(2) = Vrms
Vrms˛/R = P

Which is:

Code: [Select]

30Vpp / 2 = 15Vp
15Vp / SRQT(2) =~ 10,6Vrms
10,6Vrms˛ = 112,3 / 50R = 2,24W

That's theory. But all five power meters say "approx 8W".
The circuit draws ~1A @ 12V. So 8W out divided by 12W in is n= 67%, which sounds resonable. Also, power loss (heat) feels normal. So it checks.

What is it that I'm missing here?

Some small voice in the back of my head says "theory only looks at the positive swing. But the negative also contains energy, which makes it twice" (double the voltage = 4 times the power. Which would check. I could also run this through Fourier, which also requires to ignore the negative swing but uses two times the positive swing).

Code: [Select]

30Vpp / SRQT(2) =~ 21,3Vrms
10,6Vrms˛ = 453,7 / 50R = 9W

So, gimme a slap please.

Edit: read values from an CB Radio with Po=4W. Powermeter says: ~4W. Oszilloscope says: Vpp = 20V. Checks with my theory. But I'm none wiser.

Greetings,
~Zazzle