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

Wednesday, 20 April 2022


Ερώτηση για την απόδοση της  Double Bazooka.
Απάντηση με κακά μαντάτα.

...I am researching the Double Bazooka as another antenna I would like to experiment with on 20/40 meters. I'd like to hear from anyone who has used this antenna in the past.....is it more than just a glorified dipole or inverted V ? Has anyone tried building it with 75 ohm coax (I have quite a bit of this left over from my cable TV days).
If It somehow achieves performance that can not be realized with an ordinary Inverted V, I may give it a shot.
Thank You. Rod, K5FRH...

Charles Tom Rauch
This antenna has been analyzed and tested many times over my radio lifetime.
I once owned Midport Electronics and one of my employees sold them at Hamfests using unrealistic claims. I had BC field strength meters, because I did some SW and AM station antenna proofs.
I took one to my house and set it up in the clear and made all sorts of measurements. (I can't recall if it was actually one of his, or one I made. That was like around 1970 or so.)
It was ever so slightly lossier than a dipole, no quieter for noise, and actually not any noticeable amount wider BW than a regular old dipole made from the same materials. He continued to justify selling them, saying "people report they are better so I'll keep selling them" or something like that.
I tested another on for someone from IAC years later. It measured exactly the same as earlier tests, within instrument and site tolerances.
Walter Maxwell in "Reflections" does a pretty good analysis, as has other over the years. His theoretical conclusions paralleled the measurements I made some years earlier (around 1970 or so).


Wednesday, 29 December 2021

BalUn's - UnUn's - Autotransformer's, validation!

 Charles Tom Rauch

To know if a transformer or unun is actually any good or better than a different transformer or any good at all, you have to do an open circuit SWR with no load, a short circuit SWR curve with a dead shorted load, and a matched load.
A simple SWR curve on a load doesn't tell someone very much.

Marek Klimczyk
Charles Yes I am aware of these tests. I plan to make identical transformer and measure transmission losses to gauge performance and efficiency. Still it looks like this transformer has a very wideband transformation bandwith, which also is important.

Steve Withnell
If you take measurements of the transformer open circuit and closed circuit on the secondary, the return loss will give a view of efficiency. Obviously, if the TX sees an open circuit, the return loss should be 0 as all the energy is reflected. Energy not reflected is power dissipated in the core....

Μία καμπύλη σ' ένα όργανο δεν αποδεικνύει τίποτα.
Τρεις καμπύλες στο ίδιο όργανο, τα πάντα!

Monday, 27 December 2021

Jerry Sevick and GUANELLA BalUn understanding

Ο Steve Withnell ανέβασε ένα αρχείο στην ομάδα Antenna Building.

24 Δεκεμβρίου στις 5:22 μ.μ.  · 

Given the popularity of the Guanella BalUn and more to the point,  the prevalence of Guanella baluns that are not that at all,   prompted by Owen Duffy's blog, I pulled the original write up by Guanella.   I've OCR'd the version I found on the internet and converted it from the magazine 2 column format, to a single column document in the hope of making the article easier to read.  I may have introduced errors in the process,  you get a bit word blind comparing docs after a while.

The document is worth a look - following on from Owen Duffy's point, that there is no magnetic coupling between coils in Guanella's work.   In this document,  the coils are air-cored and method of operation of the single winding explained first, then using multiples of the single unit to change impedance transformation ratios.

12 σχόλια

Jim Kennedy

Fig. 5 is just a metal housing with connection points.

 · Απάντηση · 3 ημ.

Steve Withnell

Thanks Jim, do you have a decent copy of the image you could share?

Merry Christmas!

 · Απάντηση · 1 ημ.

Jim Kennedy

Steve Withnell

Probably not, this is the best I can provide:

Μπορεί να είναι εικόνα κείμενο που λέει "BROWN BO 617971 61797. Fig. 5. Matching unit with double-wire coils."

 · Απάντηση · 1 ημ.

Rick Westerman

Steve, what is it you are trying to do? Don't get too hung up on a document that is 75 years old. The technology has come a L O N G ways since then. You'll find a lot better information on building Guanella baluns than that document has. A good starting place is to read G3TXQ's (SK) paper on basic baluns. Then for tips on which toroid(s) to use, you can view his color charts on his web.

I can only post one link here, so I will post the second link in a second post.

Basic Baluns: http://www.karinya.net/g3txq/baluns/baluns.pdf

 · Απάντηση · 1 ημ. · Τροποποιήθηκε

Steve Withnell

Rick Westerman Hi Rick. Primarily, I picked up on the document for two reasons. First, it has a clear explanation of how the balun actually works (a rare thing!) and secondly I want to build a 12.5:50 ohm BalUn for a 70MHz antenna I've started work … Δείτε περισσότερα

 · Απάντηση · 1 ημ. · Τροποποιήθηκε

Rick Westerman

Steve Withnell Excellent reply, Steve. Now I know exactly what you want to do and I can say that I have vast experience with baluns on the HF bands and have never built one for frequencies above 6m.

First of all, be careful with Sevick. He wrote an excellent book, but like almost all books there are a few mistakes in it; one concerns the 4:1 Guanella, which you wish to build.

The BIGGEST mistake Sevick made is that he suggested that you can build a 4:1 Guanella on a single toroid core. This is not the case. You MUST use two cores.

Your circuit diagram will be exactly the same as with any 4:1 Guanella balun: you must wind two 1:1 Guanella baluns, each on its own separate toroid core.

Basically, the 4:1 balun will transfer 4:1, regardless of what its input and output impedances are.

I would suggest winding 4 or 5 turns of COAX onto each 1:1 balun. When you parallel their inputs and series their outputs, this will give you a balun with 25 Ohms on the input and 100 Ohms on the output. So it will have a 2:1 SWR, but due to short lengths, this is trivial for hf frequencies.

I don't know how it will work at 70cm.

Gud Luk, and HNY. de DJ0IP

 · Απάντηση · 22 ώρ.

Steve Withnell

Rick Westerman Thanks for TXQ's paper on BalUns. I shall go away now and have a read!

 · Απάντηση · 1 ημ.

Matt Miller

Rick Westerman tep, keep in mibd that fir decades Sevik was considered the last word. But recently his conclusions has been shown flawed as well.

 · Απάντηση · 1 ημ.

Rick Westerman

Matt Miller EXACTLY! And not just recently. I think awareness has only come recently.

 · Απάντηση · 22 ώρ.

Charles Tom Rauch

Matt Miller I knew Jerry.

When Jerry was writing his book, I know for a fact I tried to get him to change some things before publication. I know Roy Lewallen W7EL and others did also. Walt Maxwell and Jerry got in quite a private disagreement.

Jerry chose to go ahead anyway without changes.

My conclusion is Jerry was a great guy and quite an experimenter, but never did understand what balance and unbalance was and how a balun worked.

Clearly it is a matter of the public becoming aware, but it absolutely was known by some to be wrong in many critical areas at or before publication. Peer review only works when authors allow it to work.

There are three rules:

1.) never trust one source for critical information (this would go for white papers or books)

2.) always get someone ornery who isn't afraid to disagree and question in the process

3.) the only absolute answers we can universally trust is "I don't know" or "I'm not sure"

 · Απάντηση · 3 ώρ.

Steve Withnell

I worked through G3TXQs paper this morning. Excellent. One simple thing, he has actually put the 'dots' on the windings which makes a big difference to understanding the diagrams.

I hadn't seen the hybrid BalUn before - the combination of a 4:1 Ruthroff and a 1:1 Guanella.

The chatter is usually current baluns good, voltage baluns bad. Here we see a hybrid model that can be better than either.

 · Απάντηση · 2 ώρ.

Rick Westerman

And here's a link to G3TXQ color charts for building baluns.

Note that there are a few more links on that page, for more detailed information on the various ferrite mixes.


Common-mode chokes


Common-mode chokes

Common-mode chokes

Saturday, 17 July 2021

TLC for a KENPRO 7401 - 004 rotator

 I was given as an exchange a KENPRO rotator. At first it was stuck and hard to rotate but using a long screwdriver as a lever I manage to give it a couple of turns and make it sound like grinding stones!

Actually it was grinding fine particles of mud rain usually falls to Greece when in Atmosphere there is mixture of African dust and rainy clouds!

I clean it last night into my shack so I use the less flammable liquid I could use, White Spirit.

I let it soak all night and this morning using a short haired brush I clean it thoroughly and after a general apply of special grease, its like new one rotating freely. 

Photos are not great but can can easily spot the red dust on one side due probably to slight misalignment.

Friday, 7 May 2021

6m Horizontal Dipole!

6m wire horizontal dipole built the old fashion way.
On a piece of lumber! (33mm X 45mm X 400mm) 
My Create V antenna is BLR now so until I build something new with the alu tubes I left, I used the centre plate, the CMC and the coax to assembly a 6m Dipole.

After the necessary trimming each leg of the dipole antenna is 135cm. The dipole is broad to the axis of  140° - 320° and that means  that I can work Middle East-Arabian Peninsula and Central Europe-East Coast simultaneously! In THEORY!

On average is better than the Slim-Jim I am using by 6 db or so. I've just install it and I haven't made some reception tests yet. So until I'll find a way to tame the high SWR of a W8JK antenna or a design of a bidirectional Yagi, this will be my 2021 6m antenna!
cheers and 73

p.s. the dipole is elevated @approximately 9 meters ARL and 40 meters ASL.

Thursday, 5 November 2020

Restoring the Collins 180S-1

Next on the bench, a Collins 180S-1 antenna tuner found its place.
A friend of mine ask me to have a look and remove a Plexiglas plate someone had installed for some reason adding also the missing bank of 100pf capacitors.

He new nothing of its former owners, simply he wanted to be in original state rather this mistreated one.
He was wrong as it proved. The ATU wasn't mistreated but heavily vandalised.

Some one had try to make it working as Tee rather than the original Pi/L network and a lot of interconnecting wires were missing.
Easy to cut, difficult to replace and solder. 
I ordered from the Eastern Market the missing caps and load meself with tones of patience. Internet was my help the whole time with photos and useful articles.

Step by step I disassembly it by 95% being cautious not to made a bigger damage. Luckily enough there weren't  any unnecessary wholes made at the fascia or anywhere else so cosmetically it was going to fine.
And went!
It took me some time to figure what to unscrew and how in order not to make any damage and then  widen a bit the holes to pass the bolts of the new capacitor bank being different #number that the one already punched. Small stuff of great care.
Eventually everything fell in position, nothing went missing or surplus apart of a few bolts that the former owner had used for his mod. 

So another project came to a glorious end.
Enjoy the article and the photos and #staysafe
73 de sv3auw/m0lpt

Tuesday, 3 November 2020

Building a QRPGuys 40/30/20m DSB Digital Transceiver Kit

Though I haven't post something on my blog a couple of months now, that doesn't meant that I was idle.
First on the construction bench sat quoting from their site: 
"...  The QRPGuys DSB Digital Transceiver is a low cost, multiband, DSB transceiver kit, currently with three easy plug-in band modules for 40/30/20m, (additional module pcb’s available). This transceiver is an evolution compiled from various DSB and digital designs on the internet from ZL2BMI, VK3YE, AA7EE, BD6CR, and others. With help from Jim Giammanco, (N5IB) and finally Steve Weber, (KD1JV), we are offering a transceiver with an approximate output of 2.5 watts on 40m, over 1.5 watts on 30m, and over 1 watt on 20m. The receiver sensitivity was measured at .4uV (-115dBm). All the components are included for the main board (3.0″ x 3.12″) and three (40/30/20m) band modules.

The transceiver will run the popular free WSJT-X software (Windows, Linux, or macOS) that requires an accurate time synchronization program, such as Dimension 4, or many of the other free ones available. Users will need two 3.5mm stereo jumpers to your computer or tablet microphone/speaker jacks on the sound card.

The transceiver’s internal VOX circuit will switch to transmit automatically when it senses an audio output signal from the software on the pc or tablet speaker jack. The connections to the transceiver are BNC for the antenna, 3.5mm stereo jumpers to the computer audio jacks, and 12-14 VDC for the pcb mounted 2.1mm pin coaxial power jack. Approximate power consumption is about RX-15mA/TX-350mA. The total weight w/band three modules is 3oz. (85gm). The normal tools required are a soldering iron with a small tip, rosin core solder, and small side cutters. The transceiver can be built in an evening. On a difficulty scale of 1 to 5, 5 being the most difficult, this is rated at 3 depending on your experience. Note also below, plans for building a 3.5″ sq. x 1.0″ high compact chassis from PCB material. ..."

This certain kit is retired now replaced by the Digital Transceiver II kit which has an optional Digital VFO board so the user can choose the Tx frequency and Tx Mode to bands from 160m – 17m.
It can easily constructed in one evening and in my Scale of Difficulty is a fair 2! As long as you are familiar with PCB soldering and toroid cores winding, is a piece of cake!
You can find the old version here but the newer and better is the one I strongly suggest to construct! 
The kit I've constructed gave me 4W on 7.074MHz, 2W on 10.136MHz and 1W on 14.074MHz. Definitely not enough power to set alight the Ionosphere but more than enough to have a constant flow of qso's!
Enjoy your time and @staysafe 
73 de sv3auw/m0lpt

Friday, 22 May 2020

How much a Kilo weights?!

The homebrew 1Kw dummy Load I've made weights exactly 1.273 grams! That is tad less than 1.3grams per Watt!
It cost me £7 /8€.That is a mere Half Penny or Half Cent per Watt!
Not bad ! Not bad at all!
The actual cost was the purchase of the 4 DL chips 50Ω/250W for a Pound and a Half each from e-bay!
 I have a box full of heat sinks bought at a Junk sale night of SARC (Southgate Amateur Radio Club) and I pay also for a copper sheet of 12cm by 50cm another £1.5/2€

Two similar heat sinks MIGed together by my Brother-in-Law along with some drilling and that was it as long as mechanical it  takes!
I cut the copper sheet to dimensions(12cm by 20cm) with a Stanley knife, mark and make the thru holes and bolt the chips with the help of 8 M3 bolts applying thermo-paste at the same time!
I connected the chips in series/parallel configuration so I have two rows of 25Ω each connected in parallel for the necessary 50Ω load!

I've built it for myself so I don't think that it needs a box to look better and then my Lin. Amp. tuning is kept short with output power less than the rated 1Kw!
73 de sv3auw/m0lpt

Κατά καιρούς δημοσιεύονται κατασκευές Dummy  Loads μεγάλης ισχύος με την διαφορά όμως ότι όταν μπαίνει το κολλητήρι στην πρίζα τα Βατ γίνονται 150 ή 250, όσα ακριβώς αντέχει το ένα μόνο τσιπάκι.
Η κατασκευή είναι απλή.

Ένωσα δύο μεγάλες ψύκτρες με MIG κι αυτό για την καλύτερη θερμική μεταφορά κι επιφάνεια.
Παρέμβαλα ένα φύλο χαλκού για καλύτερη απαγωγή θερμοκρασίας μεταξύ των αντιστάσεων και την αλουμινένιας ψήκτρας και...
και συνέδεσα τις αντιστάσεις ανά δύο σε σειρά και μεταξύ των παράλληλα. 4 x 250 = 1KW!

Ακόμα κι αν δεν αντέχει για μεγάλο χρονικό διάστημα, δεν έχει σημασία διότι δεν θα εκπέμψω με το Dummy Load κι έπειτα δεν έχω τόση ισχύ!
Δεν θα το βάλω σε κουτί παρά θα βρω μόνο έναν τρόπο να στερεώσω τον SO239 κονέκτορα καλύτερα.
Το κόστος των αντιστάσεων δεν ξεπερνά τα 10€ από το e-bay κι ένα φύλο χαλκού δεν θα κοστίσει περισσότερο από 2€. Πραγματικά αξίζει να το προσπαθήσετε κι αν το κάνετε, καλή επιτυχία!