sv3auw
qrp, homebrew, κεραίες και άλλα συναφή διότι "ένας σταθμός ασυρμάτου είναι τόσο καλός, όση καλή είναι η κεραία από την οποία εκπέμπει"
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Wednesday, 20 April 2022
OPINIONS SOUGHT ON DOUBLE BAZOOKA ANTENNA:
Thursday, 27 January 2022
Guest Post: Crystal Radios – Construction, Listening, and Contesting
Wednesday, 29 December 2021
BalUn's - UnUn's - Autotransformer's, validation!
Marek Klimczyk
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.
http://www.karinya.net/g3txq/chokes/
Common-mode chokes
KARINYA.NET
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!
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!
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!
Thursday, 5 November 2020
Restoring the Collins 180S-1
He new nothing of its former owners, simply he wanted to be in original state rather this mistreated one.
Tuesday, 3 November 2020
Building a QRPGuys 40/30/20m DSB Digital Transceiver Kit
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!