I do not have a lot of space for antennas. So i have to get creative when possible to be able to work the bands of interest for me at this time, 40 and 20m. I have a low slung dipole for 40m in the tiny space called our backyard. Which leaves doing something for 20m.
I have had this old station master CB antenna sitting in my workshop for a while that i planned to use on 15 or 10m. Well, nothing much is doing on either of those bands other than some E’s so i have reconfigured the station master into a 20m 1/4 wave.
Its about 4.5m to the base of the antenna and the 5m of radiator on top of that and 4 radials to bring the feed impedance up to 50 ohms.
The fact that the 2:1 bandwidth is 2mhz kind of tells me that i have made a high quality dummy load. I am still unconvinced that its not a dummy load even though it does radiate.
This is the FT8 map from today. It certainly hears better than the portable dipole and reports are about the same so it is doing something.
Not to be outdone, reverse beacon reports similar reports around the pacific region. The jury is still out and I might still yet pull it all apart and start again to see if i can get that swr bandwidth narrower. For now, its what I will be using on 20m.
I have had this antenna sitting under the work bench in the garage for some time. My initial plans were to use it on 15m by making it a little longer and going to town to get it close to a 50 ohm match and hope like hell it worked ok.
So, being the bottom of the cycle and not much doing on 15m at all and that i can tune the 40m dipole up on 15m and it will work ok, and 10m is pretty much a bust, I figured i would turn this thing into a 1/4 wave on 20m.
After a bunch of false starts and I want to smash this with an axe moments 🙂 I got to doing what was needed to make it kind of work. First part was to bypass the tuning coil as it is not needed, its about 5.2m long, a bit on the long side i know, but without going at it with a hacksaw it was not not becoming shorter LOL.
Put it on the vna and it looks kind of ugly. But We can fix that I hope.
A couple of radials later and its starting to look more like what it should. 2:1 swr across the whole 20m band. When i can be bothered to add another 2 radials that should come down even more.
Fired up FT8 and it seems to be working as good as the dipole. I dont think its any better, but it is certainly not worse. That gives me 20m at home now in a more permanent way until I can be bothered to buy a tri bander.
So i got the dipole up now in its final position. The coax is now clamped to the mast so there is no flapping about in the breeze. The ends are up at their finished height. All up we have 7.6m apex and about 3m at the ends. Seems to be working ok, rx is certainly up.
SWR is as good as it is going to get and much broader banded than the old shortened dipole.
Photo bombed by Buster the Boxer. This is some fancy engenerding going on here. There is a 6ft star dropper 2ft in the ground right up the masts clacker providing the main support, the 2nd star dropper is screwed to the retaining wall and some big automotive clamps tying the 2 together. No idea what the safe working limit on all these things are LOL, but it did not move much during the big storm we had go thought last night. So i think it should be ok.
Today i pulled down the old antenna and mast and put up a new and improved version of each. The old shortened 40m dipole was only ever meant to be a temporary solution that stayed in place for 3 years. So it was time to bring her down and put it to rest.
I bought a flag pole cause it seemed like a quick and simple way of putting up a new dipole and a balun because i want to be one of those balun guys who has to tell you what kind of balun he is using even though its kind of not important to the conversation but the word balun gives the air of technical know how and ability especially when you say its a 9 to 1 balun which is really an unun or as I call them 9:1 onions, because endfails will make you cry, but I digress. <– this is called sarcasm to anyone who is going to get hurt feelings over their antenna of choice, don’t email me call your local politician and complain to them.
Erected the flagpole and hoisted up the balun and new dipole cut for 40m on the flag raising rope, saluting while humming the national anthem and got the ends up in a temporary fashion to check the long or short of it with the analyzer, when the wife gets home from work. She comes out the back, looks at the new flag pole and remarks, Oh great, its storm season and you go and erect a dirty great big lightning attracter. Chuckles to herself and leaves me to antennaring like i know what i am doing. And if my Pythagoras is correct, when i put the ends up about 4m in the air, i should have 50mm to spare. The joy of living on a postage stamp block in the city.
So with the new year comes new projects, I am not going to set out what my overall plans and goals are as I have started way to many things and never bothered to see them through or to complete them. So with that in mind, I am building a L match
Its hard to make out, but you can just see the LED glowing, the signal is 10v p-p from the signal generator, the load is a decade resistance box. At infinite swr there is 1/2 the p-p voltage at the junction of the rectifier and capacitor. As swr approaches 1:1 the voltage drops to a point where the LED turns off. Its simple and its a winner.
It will get paired up with the sotabeams switched inductor and a 8-370pf air capacitor. as an L match. Should be good enough for the kinds of girls i go out with. Below is the schematic I am following for this project and a link to the authors site is at the bottom of the page. In the final build I will use 3w 50ohm resistors and the diode i used was a Schottky, i don’t recall the numbers it was just something i had in the parts box, I used the Schottky for its lower voltage drop, though that is probably not all that critical seeing that LED’s are current limited, not voltage.
Link to authors blog post: HERE
With all the sporatic E around lately, I decided that I needed an antenna for 15 and 10m that I can deploy quickly at home and make some contacts with. I know there are better options, but I do not have space to errect other antennas and I need approval from my land lord to have anything permanent. So for ever i have been using a 40m dipole on 40,15 and 10, to some success mind you, especially on 15m.
So i figure that a trapped vertical for 10 and 15m should be a large improvement over the 40m dipole. My initial tests using a 15m vertical and 2 elevated radials seemed to do quite well, a 9db SNR improvement via Reverse Beacon Network over the dipole, making stations workable that the dipole could not even hear.
So on the CNC machine i routed up some Trap Boards, using a pair of 2000v 100pf caps in series for 50pf capacitance paralleled with whatever inductance was required to make resonance at 15m.
With silicon wire for the radator, and some zip ties for mechanical strength, its not a set and forget depoloyment, this thing will die quickly in weather, but, for something i put up on weekends, it should be fine.
Checking the resonance of the circuit. Looks about right to me.
And this is the completed trap, i should have added some more wire to the toriod rather than bunching the turns up, but i was lazy. Will see how it goes and pull it apart and make changed if needed.