Help For High-Frequency Hobbyists

Dead-bug circuit building is not a pretty affair, but hey, function over form. We usually make them because we don’t have a copper circuit board available or the duty of making one at home is not worth the efforts and chemical stains.

[Robert Melville and Alaina G. Levine] bring to light a compromise for high-frequency prototypes which uses the typical FR4 blank circuit board, but no etching chemicals. The problem with high-frequency radio is that building a circuit on a breadboard will not work because there is too much added inductance and capacitance from the wiring that will wreak havoc on the whole circuit. The solution is not new, build your radio module on a circuit board by constructing “lands” over a conductive ground plane, where components can be isolated on the same unetched board.

All right, sometimes dead-bug circuits capture an aesthetic all their own, especially when they look like this and they do allow for a darned small package for one-off designs.

Mini-velddag op zaterdag en zondag 29 en 30 september

Op zaterdag 29 en zondag 30 september houdt de VRZA Zuid-Limburg een mini velddag in Schimmert/Oensel (zie: LINK voor info over de locatie). Tijdens deze velddag zijn radio-amateurs natuurlijk van harte welkom om mee te doen en te kijken/luisteren bij het experimenteren met antennes en opstellingen.
Op zaterdag zijn we vanaf 12:00 tot pak ‘m beet 20:00 uur aanwezig, op zondag van 10:00 tot 17:00 uur. Hou voor de zekerheid het inpraatstation in de gaten op PI3ZLB @ 145.725 MHz.

Helmut Singer (Aken) gestopt…

Wie is er nog nooit bij Helmut Singer in Aachen geweest of heeft er niet op z’n minst al eens over gehoord? Helaas is het bedrijf in allerlei apparatuur niet meer…

Helmut Singer, een aparte verschijning in zijn kleine maar volgestouwde winkeltje, handelde in allerlei technische apparaten en onderdelen. Van kabeltjes van een paar cent tot spectrum analyzers van duizenden euro’s en van geigerteller tot straalmotor, hij had het allemaal. Tot voor kort want sinds eind januari is het bedrijf “in Liquidation” wat inhoudt dat het met de activiteiten is gestopt of gaat stoppen.

Jammer maar helaas, al verwachten we dat zijn voorraad hoe dan ook ergens zal opduiken…

Ah, reactie in de mailbox!

Hello,
All goods from Helmut are bought by TDM Electronics from Poland.
Test equipment will slowly appear on eBay and Allegro.pl – they are mostly still unpacked.
Unfortunately all spare parts – including HP oryginal elements are definitelly lost.

best regards,
Pawel, SQ5ESM

https://www.northdata.de/Helmut+Singer+Elektronik+Vertriebs+GmbH,+Aachen/HRB+15785

Radiomarkt Hajé groot succes

Op zondag 2 september hielden de VERON en VRZA gezamenlijk een radiomarkt bij Hajé in Berg en Terblijt. Het weer was uitstekend, de kramen lagen vol en de bezoekers stroomden massaal binnen.

Tal van spullen zijn weer van eigenaar gewisseld en bieden weer ter inspiratie voor nieuwe experimenten en knutselprojecten.

Iedereen bedankt voor de komst en bijzondere dank voor de organisatoren voor het opzetten en afbreken van de kramen!

Repeater PI3ZLB weer operationeel!

In het najaar van 2017 zweeg de repeater van Zuid-Limburg… Hoewel onderhoud en verplaatsing van de repeater reeds gepland was, kwam het als een verrassing en moest er snel worden gehandeld. De Repeatercommissie ging op zoek naar een geschikte locatie, wat nog niet eenvoudig bleek te zijn, en naar een nieuwe repeater met modernere functies.

Al met al is sinds medio juli 2018 de repeater weer operationeel! Hij staat opgesteld in Hulsberg, in het hartje van Zuid-Limburg. Meer informatie vind je op de pagina’s over de repeater.

Het bestuur bedankt de leden van de Repeatercommissie en alle helpende amateurs én natuurlijk alle donateurs voor hun bijdragen! Zonder hun hulp zou de repeater geen succes geworden zijn.

Radio Antenna Mismatching : VSWR Explained

If you have ever operated any sort of transmitting equipment, you’ve probably heard about matching an antenna to the transmitter and using the right co-ax cable. Having everything match — for example, at 50 or 75 ohms — allows the most power to get to the antenna and out into the airwaves. Even for receiving this is important, but you generally don’t hear about it as much for receivers. But here’s a question: if a 100-watt transmitter feeds a mismatched antenna and only delivers 50 watts, where did the other 50 watts go? [ElectronicsNotes] has a multi-part blog entry that explains what happens on a mismatched transmission line, including an in-depth look at voltage standing wave ratio or VSWR.

We liked the very clean graphics showing how different load mismatches affect the transmission line. We also liked how he tackled return loss and reflection coefficient.

There was a time when driving a ham radio transmitter into a bad load could damage the radio. But if the radio can survive it, the effect isn’t as bad as you might think. The post points out that feedline loss is often more significant. However, the problem with modern radios is that when they detect high VSWR, they will often reduce power drastically to prevent damage. That is often the cause of poor performance more so than the actual loss of power through the VSWR mechanism. On the other hand, it is better than burning up final transistors the way older radios did.

Measuring VSWR without a transmitter is a bit trickier. A network analyzer can do it. While that used to be a pretty exotic piece of gear, it has become much more common lately.

Free E-Book: Software Defined Radio for Engineers

We really like when a vendor finds a great book on a topic — probably one they care about — and makes it available for free. Analog Devices does this regularly and one you should probably have a look at is Software Defined Radio for Engineers. The book goes for $100 or so on Amazon, and while a digital copy has pluses and minuses, it is hard to beat the $0 price.

The book by [Travis F. Collins], [Robin Getz], [Di Pu], and [Alexander M. Wyglinski] covers a range of topics in 11 chapters. There’s also a website with more information including video lectures and projects forthcoming that appear to use the Pluto SDR. We have a Pluto and have been meaning to write more about it including the hack to make it think it has a better RF chip inside. The hack may not result in meeting all the device specs, but it does work to increase the frequency range and bandwidth. However, the book isn’t tied to a specific piece of hardware.

Make no mistake, the book is a college-level textbook for engineers, so it isn’t going to go easy on the math. So if the equation below bugs you, this might not be the book you start with:

[Di Pu] and [Alexander Wyglinksi] have an older similar book, and it looks like the lecture videos are based on that book (see video below). The projects section on the website doesn’t appear to have any actual projects in it yet, although there are a couple of placeholders.

We have enjoyed Analog’s book selections in the past including The Scientist and Engineer’s Guide to Digital Signal Processing which is a classic. If you visit their library you’ll find lots of books along with classes and videos, too.

If you want something a bit less academic, there’s always [Ossmann’s] videos. Or if you’d rather just use an SDR, there are plenty of inexpensive options to choose from.

A cleverly concealed magnetic loop

We’re sure all radio amateurs must have encountered the problem faced by [Alexandre Grimberg PY1AHD] frequently enough that they nod their heads sagely. There you are, relaxing in the sun on the lounger next to the crystal-blue pool, and you fancy working a bit of DX. But the sheer horror of it all, a tower, rotator, and HF Yagi would ruin the aesthetic, so what can be done?

[Alexandre]’s solution is simple and elegant: conceal a circular magnetic loop antenna beneath the rim of a circular plastic poolside table. Construction is the usual copper pipe with a co-axial coupling loop and a large air-gapped variable capacitor, and tuning comes via a long plastic rod that emerges as a discreet knob on the opposite side of the table. It has a 10 MHz to 30 MHz bandwidth, and should provide a decent antenna for such a small space. We can’t help some concern about how easy to access that capacitor is, on these antennas there is induced a surprisingly large RF voltage across its vanes, and anyone unwary enough to sit at the table to enjoy a poolside drink might suffer a nasty RF burn to the knee. Perhaps we’d go for a remotely tuned model instead, for this reason.

[Alexandre] has many unusual loop projects under his belt, as well as producing commercial loops. Most interesting to us on his YouTube feed is this one with a capacitor formed from co-axial soft drink cans.

Thanks [Geekabit] for the tip.