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Messages - Zazzle

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46
Good evening!

Hey Chris! Thank you a lot! :)

Maintainance report:  had to fix some support wires that broke during the recent storm. Looks like the fabric got weak due to the UV radiation. I replaced the wires with a type that's UV resistant. Everything else looks fine. I guess sooner or later one of the support poles will give away. After almost three years of sun and rain it looks ... well... tired. :)

Kind greetings,
Zazzle

47
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

48
The RF Workbench / Re: Project #4 - RTTY Beacon
« on: January 17, 2017, 0919 UTC »
It'd be keen to have a dual band beacon, 20m days, 40 or 80 nites.

Well, I already have beacons on 40m, 30m, 11m.


49
The RF Workbench / Re: Project #4 - RTTY Beacon
« on: January 16, 2017, 1518 UTC »
Heyho,

thank for the input. I've to see whether I'll stick to RTTY (easy to build) or whether I go through the efforts of building a PSK31 modulation stage.

I'm still pondering about the frequency to use. I've to admit that I fancy 80m because of the exellent propagation. On the other hand, 80m is noisy with no end. The power it'll take to cross the ocea contradics with the idea to have it entirely powered by solar. Also, the Antenna (likely a Dipole again) is an issue. 80m band means ~20m on each end. The location only allows to put it ~3m above the ground (dry gound, I should mention).

I'll likely go with the 20m band instead.

Opinions? :)

Kind Greetings,
~Zazzle


50
The RF Workbench / Re: Someone had Corsair II AM TX experience?
« on: January 09, 2017, 1055 UTC »
Hi,

(...) walk in to your tx site in temps well below freezing, be tuned up and ready to go and have one of the things fry on you.

Aren't we here for the adventure? At least a little bit? :)
And well, what pisses us off today becomes a funny story to share in a few years.

But yeah, I feel with you. I had it in Summer 2016. Just the other way around. I was installing the setup for the 30W Beacon. In a night with 36C. On a black tar roof - all hot from the day - doing acrobatics. Eventually, after hours of sweating, everything was in place. I plugged the PSU in and.... dead. It had been working 5 minutes before. I literally kicked that damn Toshiba Notebook PSU from the roof and half across the complex yard.

I guess it's what brings the fun. Having a small adeventure during night hours. Collecting memories. :)

Kind greetings,
Zazzle.

51
The RF Workbench / Re: Someone had Corsair II AM TX experience?
« on: January 08, 2017, 1928 UTC »
Hey,

(...) IMO. And I'm talking about frying them exclusively with a transmitter that outputted around 14 W of carrier. (...)

Actually, yes. Very possible. I haven't thought about that because, on my wordesk, I always use a dummy loads and short wires. So no high levels of RF escape. But yes, now that I remember the Video with "a lot of open wires"...

Happened to me outdoors when testing the 30W CW-Beacon. I was using a Laboratory Power Supply. The distance between Antenna and PSU was about 5M. But depending on where I stood the C in PSU went mad and locked up in emergency shutdown mode.

Kind greetings,
Zazzle

52
The RF Workbench / Project #4 - RTTY Beacon
« on: January 06, 2017, 1016 UTC »
Hey!

Argh! There's this idea. It's stuck in my head. Since weeks. And it wants out. Okay. Here we go.

I'm running three CW Beacons by now. I wanna do something with RTTY because it's fun and allows "high" Data rates. It's also easy to build. I can use a PI-Zero, which makes it easy to collect data and send it. So, what to send?

First, I wanted to send such like temperature, humity and - if solar powered - Battery status.

But that one disasterous evening, a friend started to annoy me with 'yer mom'-jokes and I got the idea to store a biiig collection of those jokes on the PI, having it sending them in a loop.

The other idea would involve a GPRS-Modem. I could have the PI fetch E-Mails once a day and send it's text content. The Address would be public and anyone could send greetings and whatever. This sounds pretty much fun. But I need to think about the problem with the SIM card. Thanks to our politicians going nuts about Terrorism it isn't any longer possible to get an "anonymous SIM". Buying a prepaid card now requires to register it in the shop with your ID. Sucks. So I've to check the situation in countries around my own. Means that I've to pay roaming fees. I've to think about.

I'd like to have your feedback on that. :)

Kind greetings,
Zazzle

53
The RF Workbench / Re: Someone had Corsair II AM TX experience?
« on: January 06, 2017, 0943 UTC »
Hi there!

But the real problem to solve was to separate input AF to LM386 input, so I have added a 1:1 600 ohm audio transformer, with one side directly connected to one RCA input, isolated from ground and other side connect to input of transmitter.

Now modulation is good (see short video linked) normal BIAS regulation without rustles and whistles, IRF530N power mosfet runs from warm to moderately hot depends from BIAS voltage, reach nominal 10W output, 1-1,3 A absorption.

Late me is late. Good you found a workaround. Feels god to get stuff done, hm? :)

Anyway, may I add my opinion on that? It may be a bit tech heavy, so feel free to ask if I'm confusing you

I've to agree, that the modulation circuit around the LM386 is prone to cause issues. With a distorted modulation I assume that the amplifier goes into clipping (is overdriven). The design is kinda ugly and one would be better off with a circuit that feeds the signal from the Emitter back to the OpAmp/Driver input. Along with a potentiometer to adjust the gain (and modulation grade). Makes it easy to run with input levels from - say - 100mVss to 800mVss.

I've got two theories why the transformer solved the issue:
  • 1) You have a ground loop problem. You can check this by feeding an Audio signal to the input (without transformer) by using a entirly battery driven device (that has no other connections than the one to the transmitter).
  • 2) The input signal is too high and overdrives the amp. The transformer solves it because it's input of 600R is too low for a regular audio source and causes the signal to drop on a way smaler level (which doesn't overdrive the Amp).

Kind regards,
Zazzle.

54
HF Beacons / Re: Common & Precious
« on: November 23, 2016, 1152 UTC »
It always makes me smile when I hear reports from 'over the pond'. Thank you for listening. <3

55
Hey,

Some progress:

  • A new support pole was installed. Making Duct Tape sticky again in cold ambient temperatures by using a torchlight works well.
  • The main pole, carrying the transmitter unit, was also provided with new guy wires.

I was mistaken.

I always assumed that hardly anyone would climp the roofs on that old industrial yard. But a visit on a sunny day after weeks of shitty weather made me stand corrected. There were six (6!) other people climbing roofes on the yard. Some kids, some creative guys with spray paint and some that looked like they were up to no good.

Well, after pondering my options for a moment I decied to go on. There's no way I can do anything against vandalism. Expect the hope, that when they see somone working on the poles, they might understand that it's someones project and nothing that's meant to be damaged.

Greetings,
Zazzle


56
The RF Workbench / Re: Beacon Project #3 - 5W, 11m Band
« on: November 23, 2016, 1130 UTC »
Oh, well. Sometimes I'm an idiot.

We had some sunny days recently, which left me with enough motivation to install this Beacon. Only to discover, that the SWR is beyond anything I'd call reasonable. I assumed it was, as usual, the metal construction of the roof that caused it. Adjusting the matching circuit didn't help. I was clueless for some minutes until it struck me. To make sure the matching circuit in the foot of the antenna won't become lose due to vibrations of the antenna (introduced by the wind) I've filled the coil with epoxy. Thus, making sure it's permanently attached to the socket. I should have thought about the fact that the material, a coil is wound on, even if it's a non conductive material, affects the inductance. So, well, yeah. The Epoxy filling affected the matching circuit enough to make it unusable.

Well. Do it again, Sam. Looks like I've to build and install a new coil.

Greezings,
Zazzle

57
Hey,

I thought a while whether I should write this or not. Primary because I have no intentions of annoying someone. But, well, I think I should say the following...

I've always had dipoles give high SWR when using a stock fifty feet length of coax as the feed. I've found a length (...)

Thank you for writing this. There is no use in voicing statements like "it always works" or "this is the perfect antenna".

A phrase like "this always works" will only lead to one thing: the freshman feeling stupid because he can't just get a simple works-always solution working. He'll feel frustrated. Just remember when we started? How many "why does that not work, damn?!"- moments did we live through? Especially with such complex things like antennas. And, well, ask 5 HAMS, gets 7 answers (which is fine. Everyone can only reflect from personal experiences, which differ greatly).

    Let me explain why:
    • An antenna exists (as experienced user know) of a an inductive (L, +j), capatitive (C, -j)and two ohmic parts (Wire loss Rl and radiation resistance Rr). Those parameters are prone to be affected by a lot of factors. Do we know about those factors at the place where the feshman wants to build his antenna? Hardly.
    • Of course we can say such like "start with a wire that's a bit too long and cut it inch by inch until you hit the best SWR". But likely the poor guy will never obtain a good SWR. Why?
    • The reactive L/C parts need to cancel each other out. That's the case when the wire is cut to the perfect length. But a perfect length does not grantee a perfect SWR because the feedpoint impedance may still be way off our target (lets say that's Z=50R). So the poor lad can start with 200 feet of wire and end up cutting it down to 1 inch and will still wonder "why I didn't get a good SWR? People say 'I just need to cut it down until I get a perfect SWR'".
    • Maybe the freshman obtains a perfect SWR with testing the antenna 3m above the ground (so he can work on it with a ladder). As soon as he puts it up to 10m the SWR goes postal again. He doesn't know why and will be frustrated. Why? Because (we assume L/C cancel each other out) the feedpoint impedance swings (on a graph) up and down with rising height of the antenna. At some point it's 50R for sure. But likely it well be something between 20 and 80R.
    • Maybe he uses 7m of Coax when experimenting and ends up with a good SWR. As soon as he uses 12m of Coax the SWR runs out of scale. Why? Because, yes, like Pigmeat mentioned, Coax can work as a impedance transformation line (look up "stub lines" or "stub transformator" on HAM literature).

    But likely, the poor freshman faces some impedance like 36R+j155 and he has noooooo idea how to get that to R=50Z because no one gave him a kickstart with antennas but just "
this always works".

So, since I'm a HAM I'll add my own opinion to that now (I still have to stick to stereotypes). :D

So, what's the solution? No "just do this, it'll always work" for sure.
Of course, one of the best ways to get the freshman started is to provide him with some links to basic Antenna theory and advice him to puracse an antenna analyser (yeah, owies, several hundred bucks). But that way he can experiment and verify the theory from the book by results from the antenna analyser. And he can learn what stuff affects the antenna and will get it on track.

But, yeah. You're right to laugh at me for saying that. That's not realistic. :)

So my advice is: yes, use a (not complex, self build) Antenna Tuner. The setup is as follows:

[TX]-- Z=50R COAX-LINE -->[C-L-C Tuner] -> [BalUn] -> Dipole

Or, if it's prefered to have the tuner inhouse, he could use something like a G5RV-Antenna.

You may ask "why the tuner?". Well, like I wrote above, there's no way to know about the parameters of the antenna and a tuner is the simplest way to compensate any L/C-part and also transform the impedance to 50R.

Kind greetings (and really, I didn't mean to step on anyones tail if I did by accident),
Zazzle[/list]

58
The RF Workbench / Re: Beacon Project #3 - 5W, 11m Band
« on: October 30, 2016, 2305 UTC »
Hi!

I found time to build a L-Match for the old CB Antenna I'm gonna use with this Beacon. Works like a charm. SWR 1:1,2 or better.

By now it's mounted on "the roof"[TM]. But I forgot the Transmitter unit at home. Well, that has to wait until next weekend then.

Greetings,
Zazzle

59
Hi,

looks like I've been the victim of vandalism for the first time since I put the Beacons on the roof. But the whole situation is pretty confusing.

One of the support poles were down, shattered into pieces. The fragments look like someone had been hitting them with a big, sharp object, like an axe or machete.
I wonder who climbs up to the roof (not that easy) with some big knife to damage one pole? Power cables, antenna wires and everything else was left untouched.
Curious. When someone intended to go all postal he could just damage all Beacon setups in less than 5 minutes to the point beyond repair.

My current guess is, that it were some kids that started with the first pole and ran off when it came down.

As a result one half of the Dipole were down. So far I could bring it up with some quick fix. Still, it won't radiate properly with the current angle.

Therefore this Beacon runs currently with restrictions. If the weather is on my side next weekend I'm gonna install a new support pole. If things are worse than I was able to see in the dark  I also need to replace the entire half of the Dipole.

Oh well, could have been worse. :)

Kind greezings,
Zazzle.

60
The RF Workbench / Common and Precious IV - Construction phase
« on: October 21, 2016, 1702 UTC »
Hey,

so, this is the board of the Beacon that I took with me on vacation during Autumn 2015. It Outputs approx 10W+ @ 13V. I wanted to play a bit with push-pull PAs. It's simple: oscillator, keyed buffer, driver and PA. PA (final) and oscillator/driver are feed seperately. Which allows me to feed the PA with higher voltages seperately.

Since I have no use for this as a Beacon any longer (got replaced by the 30W Class D CW Beacon) I'm planning to turn this one into a small AM transmitter for experimenting and having some fun.

The big AM Transmitter project (300W+) already goes by the name "Dirty Phoenix". So I call this one "Dirty Phoenix Jr."

Next todo: mounting it to a chassis with proper heatsink and cleaning up the inductor mess.

Kind Greetings,
Zazzle

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