.

Ο λόγος στασίμων 1:1 ενός κεραιοσυστήματος, δεν συνεπάγεται τον 1:1 λόγο μεταφοράς ισχύος, προς την κεραία!

Monday, 25 September 2017

Ατσαλόσυρμα σε Βραχέο δίπολο. Μπορεί να χρησιμοποιηθεί?

Σχετική εικόνα
Σε τακτικά διαστήματα σε Ελληνικά αλλά και διεθνή Fora, τίθεται το ερώτημα:
"Μπορεί να χρησιμοποιηθεί ατσαλόσυρμα για κατασκευή δίπολης κεραίας"?

Το ερώτημα τέθηκε πάλι μερικές μέρες πριν στο forum RSBG όπου ανάμεσα στα, ναι-όχι-ίσως-μπορεί-δεν χάθηκε ο κόσμος-υπό προϋποθέσεις, κάποιος έδωσε ένα link Αυστραλιανού Συλλόγου ο οποίος δημοσίευσε ένα άρθρο το οποίο έγραφε και τεκμηρίωνε όλα αυτά τα οποία εσείς διαβάζετε σε αυτό το ιστολόγιο από τον Φεβρουάριο του 2009!
Έγραφε λοιπόν στο εν κατακλείδι ο Tim VK2BT: ...I would NOT recommend using stainless wire for a “low impedance” antenna (such as a simple dipole). I learned this lesson the hard way myself when I recently constructed one for myself at home, and found that I could NOT match it properly. (δεν θα συνιστούσα την χρησιμοποίηση του ατσαλοσύρματος για κεραία Χαμηλή Σύνθετης Αντίστασης π.χ. ως ένα δίπολο. Πήρα το μάθημά μου με άσχημο τρόπο όταν το είχα κατασκευάσει στο σπίτι και ΔΕΝ μπορούσα να το συντονίσω.)
Το όλο άρθρο είναι στην σελίδα του Manly-Warringah
Radio Society MWRS και διαβάζεται εδώ καθώς και το pdf με την eznec ανάλυση το οποίο θα διαβάσετε εδώ.

Επαναθέτοντας λοιπόν το ερώτημα:"Μπορεί να χρησιμοποιηθεί ατσαλόσυρμα για κατασκευή δίπολης κεραίας"?
Η απάντηση είναι μονολεκτικά ΟΧΙ!
ΟΧΙ ως κεραία αλλά ως στήριγμα της πραγματικής κεραίας, πραγματικά μπορεί και είναι ΝΑΙ!
Tip. Μου ζήτησε ένας συνάδελφος να αγοράσει αρκετά μέτρα από το multistranded του οποίου έχω μερικές καρούλες και πωλώ. απαραίτητη προϋπόθεση ήταν να αντέχει τα 12 Μποφόρ των μελτεμιών του Αιγαίου. Του έστειλα μερικά μέτρα σύρμα για δοκιμή η οποία με την σειρά της απέδειξε ότι το 7stranded σύρμα έχει την απαραίτητη αντοχή στην μόνιμη έλξη αλλά όχι στα τινάγματα και τις ριπές του αέρα. Επάνω στην κουβέντα για προτεινόμενες λύσεις πρότεινα το εξής. 
Να συνεχίσει να υπάρχει το ατσάλινο δίπολο, ΜΟΝΟ ΩΣ ΣΤΗΡΙΓΜΑ του χάλκινου αγωγού ο οποίος θα τρέχει παράλληλα. Τα "επιδερμικά φαινόμενα" τρέχουν στην επιδερμίδα του αγωγού διαλέγοντας πάντα την καλύτερη αγωγιμότητα άρα στο συγκεκριμένο παράδειγμα, η RF θα επιλέγει πάντα να τρέχει στον Χαλκό αδιαφορώντας για το Ατσάλι δίπλα του.
ΝΑΙ! Μπορείτε να χρησιμοποιήσετε ατσαλόσυρμα ως στήριγμα του χαλκοσύρματος της δίπολης ή άλλης κεραίας και τίποτε άλλο! Απλά μην το πληρώνετε ώς "σπέσιαλ"!

Tuesday, 29 August 2017

Faulty ladder-line to dipole connection.

I spent past weekend operating as SV3AUW/A from my resort house in Mani region.

My SEM tranZmatch was coping the mismatch of my dipole antenna in all of HF amateur frequenses until I get the fist RF bite. Accidentally I touched the chassis of my radio and I felt the "familiar" sting of  RFI and I smell the equally "familiar" smell of RF burned skin. Nothing serious but an RF bite is a painful one!
My radio was "seeing" a perfect match and was pumping 100 watts continuously but that power was never reaching the antenna or was never transmitted from it. There was a fault and I had to find it.
The proof of pudding is eating and the proof of faulty antenna is climbing the tiled roof.
It didn't took me long to see the broken wire of my ladder line at the centre plate as you can see in the photos.

Usually I carry a few tools with me, just-in-case, this time though due to a reason I took nothing with me. The only tool that was handy, was an old and rusty pair of pliers with the help of I managed to make a temporary, and efficient if I may add, repair of the broken wire by using a small piece of hookup wire to splice the two ends.

Next weekend or next time I'll go back, I will definitely have with me a big roll of extension cable, soldering iron, solder, the full monty!
By the way, I am surprised with the excellent efficiency of my ASTU which firstly matched and saved the output transistors of my radio and secondly, although it was operating erroneously it managed to pump enough RF to the one side of my dipole antenna so to work on 25/07/2017 at 20:55UTC with JH3NGD receiving 57 report!

Wednesday, 16 August 2017

Jeff Dumps (KL4IU) seeks crowd funding for HAARP experiment



I was wondering if you would be interested in sponsoring my amateur radio science experiment at HAARP. I am a new ham, and have participated in the February HAARP campaign, assisting Dr. Chris Fallen. It has inspired me to try an experiment. My experiment is designed to analyze the modulation frequencies and their effect on ionospheric cross modulation (Luxembourg Effect). Not only would this be a great opportunity for me, but also it could help the HAARP facility with more positive media coverage. It could also get other amateur radio folks interested in HAARP and the science behind it. As far as I know, there hasn't been a crowd funding campaign for HAARP time - so that would also be a very cool first if it is successful.
I would greatly appreciate it if you could share my campaign with the SWLing Post folks. I've raised $100 so far from one donor, only $900 more to go!
Here is the link to my crowd funding campaign page. On the page it has more details and a link to my experiment outline which details exactly how the experiment will be conducted.
Thanks for your time!

Monday, 1 May 2017

Hollow tube "homebrew" antenna tower!

  
I wanted to find the cheapest and safer way to rise my multi-band dipole antenna higher than the 6 meters it was.
After so many discussions and suggestions from the technical team, I finally settled on the solution of one square hollow tube inside the other.
Since the existing SHT I was using was 40X40mm the next size to use was either 50X50mm or 60X60mm. I then chose 60X60mm and on that basis my thought was how I would make it safe and functional at the same time. The steps were one of those thoughts! At the same time, because I intended to use the YAESU G-1000 rotor I had purchased some many years ago, I had to find again a safe and easy way to fix it to the tower construction. It's not easy to cross Kalamata even from side-roads with 6-meter square tubes on the roof of the car, nor comfortable to ask friends with bigger cars to do it. So I had to found a way to do what it must be done in the machine shop, cutting welding etc, and then the final assembly to be done on my roof.

I think I achieve it all the way to the end result.
Underneath the rotor cage, they weld for me a rectangular tube 40x50mm, 25cm long made in situ. Inside, that I could slip the existing 40X40mm SHT  and secure with two bolts bolted to the existing pre-welded nuts.
Another two of such nuts were welded to the large 60X60mm SHT, so as to stabilize the smaller tube at the desired height. For greater security, every one meter, transverse holes were opened so that a 7mm steel pin passes through.


In this way, the height of the dipole can reach from the 6-meter of the SHT plus the 2.5m of rotor along with the 1.5" steel pipe 8.5m, all the way up to 13.5m after extending by 5m of the smaller SHT. 
Already at the height of 8.5m there is a difference of 6 to 10db better reception compared to the random length of 32.5m wire which I use as an alternative antenna. With the dipole at the old height 6m the difference was a bit more than above the noise. 
Now higher it is far better, apart the advantage of rotation.
Check out the photos, and if I have forgotten something, I would gladly refer to it and clarify it.




 Ήθελα με τον φτηνότερο αλλά και ασφαλέστερο τρόπο να ψηλώσω το δίπολό μου από τα 6 μέτρα της υπάρχουσας κοιλοδοκού.
Πολλές συζητήσεις και προτάσεις από το τεχνικό τημ, τελικά καταστάλαξα στην λύση της μίας κοιλοδοκού μέσα στην άλλη.
Εφόσον η υπάρχουσα ήταν 40X40mm λογικό ήταν η επόμενη κοιλοδοκός να ήταν 1 ή 2 νούμερα μεγαλύτερη με την υπάρχουσα να γλυστρά μέσα της χωρίς δυσκολία.
Επέλεξα τότε την 60X60mm και με αυτό σαν βάση σκεφτόμουν πως θα την έκανα ταυτόχρονα ασφαλή και λειτουργική. Τα σκαλοπάτια ήταν το λογικό αποτέλεσμα.

Ταυτόχρονα κι επειδή σκόπευα να χρησιμοποιήσω και τον ρότορα τον οποίο είχα αγοράσει προ απομνημονεύτων ετών, έπρεπε να βρεθεί και για την στερέωση/εφαρμογή του ένας ασφαλής κι εύκολος τρόπος. Δεν είναι εύκολο να διασχίζω την Καλαμάτα ακόμα κι από παράδρομους με 6μετρους κοιλοδοκούς επάνω στο αυτοκίνητο, ούτε ακόμα να ζητώ από φίλους με μεγαλύτερα αυτοκίνητα να το κάνουν. Έτσι έπρεπε να βρεθεί ο τρόπος να γίνει ότι πρέπει να γίνει στο μηχανουργίο κι έπειτα το τελικό κι ασφαλές μοντάρισμα να γίνει στην ταράτσα μου.
Πιστεύω ότι τα κατάφερα σε όλο τον δρόμο μέχρι το τελικό αποτέλεσμα.
Κάτω από το κλουβί του ρότορα κολλήθηκε μία παραλληλόγραμμη κατασκευή 40X50mm και μήκους 25cm. Εκεί μέσα θα συρτάρωνε η υπάρχουσα κοιλοδοκός και θα ασφάλιζε με δύο βίδες στα υπάρχοντα προεγκατεστημένα παξιμάδια.
Ακόμα δύο τέτοια παξιμάδια κολλήθηκαν και στην μεγάλη κοιλοδοκό, έτσι ώστε να σταθεροποιούν την μικρή κοιλοδοκό στο επιθυμητό ύψος. Για μεγαλύτερη ασφάλεια, ανά μέτρο, ανοίχτηκαν εγκάρσιες τρύπες έτσι ώστε να περνά ένα ατσάλινος πίρος 7mm.
Με αυτον τον τρόπο το ύψος του διπόλου μπορεί να φτάσει από τα 6μέτρα της μεγάλης κοιλοδοκού συν τα 2.5 του ρότορα μαζί με την σωλήνα 1.5" 8.5m στα 13.5m αφού προστεθούν και τα 5m της μικρής κοιλοδοκού. 

Ήδη στο ύψος των 8.5m υπάρχει διαφορά 6 με 10db στην λήψη, σε σύγκριση με το τυχαίο μήκους σύρμα των 32.5m  το οποίο χρησιμοποιώ ως εναλλακτική κεραία. Με το δίπολο στο ύψος των 6m η διαφορά ήταν κάτι περισσότερο από τα όρια του θορύβου. Τώρα είναι καλύτερα, χώρια το πλεονέκτημα της περιστροφής.
Δείτε τις φωτογραφίες κι αν έχω ξεχάσει κάτι, ευχαρίστως να το αναφέρω και να το διευκρινίσω.

Saturday, 29 April 2017

CIRCUIT BOARD DESIGN CLASS


In this class, you will learn how to design a custom printed circuit board from a breadboard prototype. This is useful if you want to make multiple copies of a circuit board for your project, or simply want to add a level of polish and professionalism to your work. By creating your own custom circuit boards, you are elevating your project to more refined levels of design and fabrication. 

While this may seem intimidating, it is actually easy to do if you take your time and do it carefully. I will show you how to digitize a circuit in the freeware version of Autodesk Eagle and then how to convert the schematic into board files which can be sent out for fabrication. Once you see for yourself how easy this process is, you will be hooked. There are few greater feelings in the wild world of electronics than holding your first custom manufactured circuit board in your hand. 

I hope that you will follow along with me as I teach you how to design a circuit board.

https://www.instructables.com/lesson/PCB-Concepts-and-Materials/

Wednesday, 26 April 2017

The Cricket


The Cricket: The Four State QRP Group’s latest transceiver kit


 Here's a hot tip for those of you who enjoy building transceiver kits:
The Four State QRP group has just released The Cricket: a simple 80 CW transceiver kit. The Cricket was designed by David Cripe (NM0S) who is behind a number of successful kits (including the Ozark Patrol and the Bayou Jumper).

The amazing part about this kit is that it's super simple, has no toroids to wind and doesn't even need to be aligned. It even includes a Morse key.
All this shipped for $32.68 in the US, $39.50 in Canada and $43.50 for international orders. A serious bargain, in my book.
Typically, Dave's kits sell out the same day they are posted for sale. If you're interested in The Cricket, don't hesitate to order! (I just bought three, for example.)
 Here's The Cricket kit description via the Four State QRP Group website:
Kitted and Offered For Sale By The Four State QRP Group
The Cricket is a low cost entry level minimalist CW transceiver for the 80 meter band. Chosen as the build session kit for OzarkCon 2017, it bears a family resemblance to the well known but much lower performing Pixie. However it is very different and vastly improved over the Pixie. This is NOT a Pixie, it is far superior! It features low parts count, better components including MOSFETs for better sensitivity and switching, and a modern NJM2113D audio amp.
A TX/RX offset is also incuded so that you can work other stations that have zero beat you, or are using a crystal on the same frequncy. Full QSK and a sidetone complete the essential operating features. Dave's famous etched spiral coils are included on the pc board, so there are NO TOROIDS to wind. Additionally a straight key is included on the pc board, just snap it off, mount it on the board, and the whole rig is then self contained. Also included is an electronic keyer adapter - you can use your favorite keyer with the Cricket! These are many features for such a low parts count and inexpensive transceiver.
ALL THROUGH HOLE parts make this kit very easy to assemble. It will make a fine, fully functional, and educational first rig for a new builder, the new ham, or seasoned veterans wishing to just have fun with a new rig at minimal expense and effort. Note that Novices and Technicians have 80M CW privileges from 3.525 to 3.600, same as everyone else - so they also can build and use the Cricket.
This simple rig is fun and functional, and made many contacts at OzarkCon after the build session. A proven design and a great choice for your next rig, it is perfect for a group build with nets and contacts after the build. This is an excellent club project.

Tuesday, 21 March 2017

Voltage + Polarity indicator



Bic pen voltage and polarity tester.
This item of test equipment is a low voltage supply test indicator and polarity checker. It not only finds use on the bench in the radio room but everywhere there is low voltage pesence! In practise it will prove its worth in no time at all in any situation where there is a losw voltage power supply and wirring. As well as checking that power is available and its polarity it can be used for wire tracing and checking that fuses are OK.
The shopping list is very small, only six items and most of the bits can be found in the junk box if you have one. Firstly, we need a clear plastic ball pen, preferably at the end of its life.
Remove the refill from the pen case and clean the tip. Then solder a small piece of wire into the hole left by the removal of the ink tube. Now solder the green and Red LEDs in reverse as you can see in the photo and solder the wire to the anode the Green 3mm LED and then the 220W resistor to the anode of the Red LED. The free end of resistor is connected to a length of wire terminated in a small ‘crock clip’. If the probe is connected with the pen probe on the positive terminal the Green LED will light, and if connected the other way the Red LED will light! This gives us the polarity check. i.e. If we find a voltage present on one side of a fuse and not on the other this confirms the fuse has blown or the fuse holder is faulty. When this is all assembled in the case and you’ve used it a few times I am sure you will wonder how you managed without one in the past!  
based on an idea of Ian G3ROO

Ελεγκτής τάσεως και πολικότητος.
Υλικά:
Δύο LED διαφορετικού χρώματος.
Μία αντίσταση 220Ωμ.
Ένα στυλό Bic®. (τελειωμένο για να μη τα κάνετε χάλια με το μελάνι!)  
Συνδέετε ανάστροφα τις δύο διόδους και κολλάτε την αντίσταση όπου  σας είναι πιό βολικό. Εγώ την κόλλησα εμπρός για να φαίνονται καλύτερα τα LEDs.
Το δοκίμασα μέχρι τα 28 Βόλτ και δεν είχα πρόβλημα με τις διόδους. Με το ΣΥΝ στην μύτη ανάβει το Πράσινο LED ενώ με το ΜΕΙΟΝ στην μύτη ανάβει το κόκκινο LED. Στις περισσότερες περιπτώσεις θα θέλετε να δείτε αν έχετε θετική τάση αλλά γιατί να μην υπάρχει η δυνατότητα ένδειξης της αντίστροφης? Το μόνο που κοστίζει είναι ένα LED παραπάνω!

Thursday, 16 March 2017

Keying interface for IC-706.



Icom's IC-706 compact transceiver is intended for mobile use, but its small size also appeals to DXpeditioners. Unfortunately, Icom designers decided against installing a T/R (transmit/receive) control line output for interfacing an external power amplifier. The circuit presented here provides that interface.
A 13-pin DIN connector on the rear panel of the rig has a bidirectional control pin named HSEND (HF Send). In receive mode, it is pulled to +8V through approximately 1.2k. When transmitting, HSEND is about zero volts. Since it is bidirectional, grounding HSEND externally will also place the transceiver in transmit mode. The characteristics of this pin prevent its use as a direct T/R signal for most amplifiers it only sinks about 6mA, and most amplifier control lines pull higher than 8V. Directly connecting HSEND to a typical amplifier could damage the IC-706.
If you own a legacy HF amplifier( 30L-1, SB200/201 KW600/1000 YAESU FL line etc)  that have high voltage (120 V) switching or spiking issues you must use in series of the Q2 Collector a relay having a C to NO contact.

Pin Number I used.
Pin nr2 GROUND
Pin nr3 HSEND
Pin nr8 +13.8V
Have fun and enjoy home-brewing!


Κατασκευή ενός ενδιαμέσου για την ενεργοποίηση γραμμικών ενισχυτών από το IC-706 αλλά κι άλλων παρόμοιων ενισχυτών από παρόμοιους πομποδέκτες.
Αν ο ενισχυτής αρκείται στο να δει ΓΗ για να ενεργοποιηθεί, το κύκλωμα ως έχει είναι αρκετό. Στην περίπτωση των παλαιών καλών ενισχυτών του τύπου 30L-1 ή SB200/201 KW600/1000 YAESU σειρά FL κλπ
θα πρέπει να συνδέσετε ένα 12V ρελέ σε σειρά με τον Συλλέκτη του Q2.

Tuesday, 14 March 2017

3.14 the Pi Day!


LEARN ABOUT PI


Pi ( π) is the ratio of a circle’s circumference to its diameter. Pi is a constant number,
meaning that for all circles of any size, Pi will be the same.
The diameter of a circle is the distance from edge to edge, measuring straight through the center. The circumference of a circle is the distance around.

HISTORY OF PI

By measuring circular objects, it has always turned out that a circle is a little more than 3 times its width around. In the Old Testament of the Bible (1 Kings 7:23), a circular pool is referred to as being 30 cubits around, and 10 cubits across. The mathematician Archimedes used polygons with many sides to approximate circles and determined that Pi was approximately 22/7. The symbol (Greek letter " π") was first used in 1706 by William Jones. A ‘p’ was chosen for ‘perimeter’ of circles, and the use of π became popular after it was adopted by the Swiss mathematician Leonhard Euler in 1737. In recent years, Pi has been calculated to over one trillion digits past its decimal. Only 39 digits past the decimal are needed to accurately calculate the spherical volume of our entire universe, but because of Pi’s infinite & patternless nature, it’s a fun challenge to memorize, and to computationally calculate more and more digits.

GEOMETRY

The number pi is extremely useful when solving geometry problems involving circles. Here are some examples:
The area of a circle.
A = πr2
Where ‘r’ is the radius (distance from the center to the edge of the circle). Also, this formula is the origin of the joke “Pies aren’t square, they’re round!”
The volume of a cylinder.
V = πr2h
To find the volume of a rectangular prism, you calculate length × width × height. In that case, length × width is the area of one side (the base), which is then multiplied by the height of the prism. Similarly, to find the volume of a cylinder, you calculate the area of the base (the area of the circle), then multiply that by the height (h) of the cylinder.