Lot's can be written about the HB9CV antenna and it's construction. But I like to write about how it is working on air and the experiences I encoutered with it and not only about construction as it can be done in many ways. All details can be found on the internet these days.
Anyway, I have to tell the whole story so a little theory is necessary since you will always encounter some minor problems. I don't know were I got the calculating formulas from in the past but it wasn't from Rothammel's antennabook which I posess. I didn't really know but I always used the 75 Ohm formula as long before the internet I didn't have anything else. But now it seems there is a slight difference between the 75 Ohm and 50 Ohm version. Never noticed a bad SWR or so, but didn't have a analyser as well at that time. So, there are 3 different basic models as you can see in the picture. The difference between the 75 and 50 Ohm version is the gamma match.
I use the 50 Ohm formula for my HB9CV this time. Besides that I used a piece of cheap 75 Ohm coax as capacitor. I don't write about the exact building as there are many sites on the internet about that.
One of the best sites I found regarding the HB9CV, you need to translate however. Should be no problem: http://www.ok2kkw.com/hb9cv/hb9cv_1969.htm. Unfortenately you won't find that the actual design is for a 75 Ohm coax cable.
All this HB9CV writing, thinking and building made me remember some personal notes. Sometimes you almost forget things that happened in the past. I encountered happy and sorrow times with the HB9CV antenna back in the early nineties of last century. The first HB9CV was made for a friend that had a very bad traffic accident. He was in a wheelchair and most of his radio and antennawork was done by friends. Unfortenately when I finished the antenna his health went very bad. He couldn't barely talk anymore. He persisted to put the antenna on the mast myself. A year later he died. Second one was built for another friend which I contacted lately via facebook. I remember this HB9CV as the one that was struck by lightning and still survived. I only had to go up to his roof and replace the capacitor and box + coax. The lightning did get from the coaxcable into a copper gastube made a hole and he had a fire upstairs since gas was flowing out. Luckely he was at home and could turn off the gas. He recently wrote me he sell his HB9CV as he had no place for it at a new home. The third one was made as a birthday gift ordered by a XYL from one of my radiofriends at that time. He had a incurable brain tumor and all he wanted was a HB9CV. I made him one and helped to raise the antenna at his birthday. I remember he was very very happy and I made many QSO's with him always with both HB9CV's pointed to each other. Besides that he was finally able to do some decent DX. He passed away about a year later leaving his wife and 2 kids. I measured the antenna for him when constructing and you can see the results in the "plot". But there were also happy times. We had a lot of DX fun of course with our HB9CVs. A lot of DX with 25W all over the world. I worked at least 220 DXCC with this antenna on the 11m band and it never let me down.
Curious how the "new" HB9CV is going to work?
Er kan veel geschreven worden over de HB9CV antenne en de constructie ervan. Maar ik wil meer vertellen over hoe zo een antenne in de praktijk werkt en de ervaringen en verhalen er om heen omdat de HB9CV op diverse manieren gemaakt kan worden. Tegenwoordig kun je er van alles over vinden op internet.
Maar goed een klein beetje theorie ontkom je niet aan omdat je toch altijd weer wat probleempjes tegenkomt tijdens het bouwen. Ik weet niet meer waar ik destijds de formule's vandaan had om de antenne te berekenen maar het was volgens mij niet uit het antenneboek van Rothammel die ik bezit. Ik wist het eigenlijk niet maar ik werkte altijd met de 75 Ohm formule omdat ik lang voor internet gewoon niet anders had. Nu blijkt dat er een klein verschil zit in de lengte van de gammamatch voor 75 Ohm en 50 Ohm. Eigenlijk is het me nooit opgevallen, geen echt slechte SWR of zo, maar goed ik had ook geen antenne analyzer destijds. Zoals te zien op het plaatje zijn er zelfs 3 versies.
Voor mijn HB9CV gebruik ik dus de 50 Ohm formule dit keer. Daarnaast gebruik ik geen variabele C maar een stuk goedkope 75 Ohm coax als condensator. Ik ga niet schrijven over hoe ik dingen gemaakt heb want er is al genoeg over te vinden op internet.
Een site die volgens mij de beste omschrijving geeft van de HB9CV antenne is helaas in het Tjechisch. Maar vertalen hoeft vandaag de dag geen probleem op te leveren. Kijk maar eens hier: http://www.ok2kkw.com/hb9cv/hb9cv_1969.htm. Helaas vind je daar niet dat het oorspronkelijke design voor een 75 Ohm coax bedoeld is.
|Parts so far...|
Ben benieuwd hoe de "nieuwe" HB9CV gaat werken?