We had a storm earlier this week. But since I leave home when it is still dark and come back when it is already dark I didn't notice my vertical antenna was gone...
Found the broken parts in the neighbouring garden, they didn't notice as well I guess....time to analyze the damage.
For a while I noticed the antenna was not straight up anymore, it did bend even without wind. So this all came not as a surprise. You can see the wire the is originally inside but was not used anymore and the wire I attached at one side. I saw the tube went flat and not round anymore, I guess it was already a weak point that eventually cracked. I was unable to see the cracks because the antenna was covered with plastic tape.
I cut the center tube to have a view inside You can see the small wire inside. A common fault with these antennas is a broken wire which is difficult to repair. Since an Imax2000 is 7,5m long they bend a lot in the wind, with such a tin and solid wire it's no wonder it snaps.
After I replaced the A99 (with alutape cover) with the Imax2000 (with coppertape cover) years ago I have been thinking many times to threw this one in the garbage. But luckely I didn't....and yes, this one also suffers from the broken inner wire...
The A99 is 4,75m long. And not 5,5m like many think. Many 11m operators do use these antennas but I think originally it is a 10m band antenna. The formula to calculate a wire antenna with insulation is: 300/28,5(MHz)=10,52m/2=5,26m-5%=4,74m
I found one part suspicious. The center part is glued into a steel bushing. But I could turn it around. So I made some kind of splint to be shure it will no break at that place and stays into the bushing.
I wouldn't be a experimenter if I wouldn't try something new. This time I tape 5 1/4 wave wires onto the A99 for 20 till 10m. I want to see how this works.
When the antenna was ready it occured to me that I probabely used the mast mounting U-bolts for other projects......but how lucky I was, I still had this mast mounting system from my Diamond CP-6 which fits exactly around the bottom tube from the A99. A lucky miracle!
I was so lucky the weather was great. After some cutting, grinding, connecting and insulating the new 5 band 1/4 wave vertical is up again. The configuration is as follows:
TRX > Coax > Galvanic Isolator at botom of tower > Coax > Air choke > CG3000 autotuner > High quality 1:1 balun > 5x 1/4 wave wire for 14,18,21,24 and 28 MHz.
Results: Most important, does it tune. Yes, the tuner had a problem with 12m at first but after tuning 10m 12m was fine. Compared to the inverted-V the vertical does not win on 20m, receive is about 1-2 signal point weaker and sometimes it is the same...On 17m it clearly wins from the inverted-V. I don't know for 15, 12 and 10m since there is no propagation present. Hope to find out tomorrow.
I tried to make some SSB contacts with the vertical but I could hear only a few stations which were not really strong. Have been calling for 10 minutes but no one answers. So I switched to FT8.
Did some calls with 100W to see results. This was after about 20 minutes. Despite my signal was heard in Africa and USA I didn't make any DX QSO. Only a few European stations that responded. I'm shure it is not my signal that is the problem but the amount of stations that are transmitting in multiple signal layers on just 3000Hz. I couldn't simply find a clear spot on the waterfall to get my signal out the the DX stations I wanted to work. 20m FT8 is not really my piece of cake...
Well, I hope this antenna will survive any other storm this year. Hopefully it will help me getting my signal out on 17, 15 and 12m.
Bas, when I first read the headline I thought your tower came down and that now you have *only* a vertical - good thing the vertical was the only thing lost and that it was easily/quickly replaced!
ReplyDelete73 - John
Wel John, we had a windforce 7 Bft. I retract the tower when the forecast is 9 Bft or more. The tower down would need a hurricane of 16 Bft which is very uncommon here. It was only the vertical and I was not really surprised about it. Lucky I still had the A99 around in the garage. 73, Bas
DeleteGood afternoon Bas, very nice work on getting things up and running again. Even though you were not able to make any SSB contacts FT8 is a great way to see and make sure the antenna is getting out. By the map I would say the antenna is doing just fine!
ReplyDelete73,
Mike
VE9KK
Hello Mike, yep despite my efforts my signal was getting out. Later in the evening I even saw I was spotted in Antarctica and western Australia. But on 20m it´s just too difficult to get out...73, Bas
DeleteExcellent work! What a stupid solid wire. Just about any wire would have been better than that stuff!
ReplyDeleteFor your interest, 15m propagation was very good this afternoon, notably to the US and South Africa.
I was really surprised by the size of the wire John, no wonder it snaps. I would really not buy a A99 or a Imax new ever again. You can make a much better and stronger antenna yourself. The propagation hasn´t been the same here compared to yours. I´ve been listening on 15m but not much to hear. We had some propagation to Lebanon early in the afternoon. Signals on the vertical were about 4 S-units better compared to the inverted-V. I've been trying the vertical on 40m/60m as well on receive, I was surprised it did well....actually better as with the 7,5m Imax vertical. On both bands I received almost equally signals when I compared the inverted-V with the vertical... And tuning was not a problem at all. I guess that has something to do with the tower which is used as counterpoise. 73, Bas
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