I may not mention this much, but I like it when people get these old original antennas and restore them. And this being one of my favorite antennas to explore...
Keep up the good work.
The DB
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ASTROPLANE best vertical antenna ever?
- Thread starter nosepc
- Start date
I may not mention this much, but I like it when people get these old original antennas and restore them. And this being one of my favorite antennas to explore...
Keep up the good work.
The DB
Does it matter if I isolate the mast from the tower? I’m at 50’ to the bottom of the skirt on a tower. Also wouldn’t I need a choke at the same place it isolated from the tower? Isn’t that like 9’? But just how much difference does it make if any
During the rare free time I had at work today I read through some of the earlier posts in this thread. The old days where several of us were dissecting these antennas and others trying to figure out how they actually worked... I learned a lot doing that, and learned modeling as well. Me and others taking into account the various thoughts and ideas, and presenting our own to see what others thought...
I simply wouldn't be where I am today, knowledge wise, without it.
And a piece of me misses it...
The DB
I simply wouldn't be where I am today, knowledge wise, without it.
And a piece of me misses it...
The DB
Agreed. I always enjoyed the exchanging of ideas here, and it stayed pretty civil. I look back at all the antennas that were available during the 70's, and Avanti really had some interesting products.
Reading this thread again has made me want to build an Astroplane for my frequency of choice,
I am not butchering my original Astroplane so I would use the "old CTE top-one" bracket that Eddie Marconi (RIP) sent me years ago,
It would have a full 1/4wave upper radiator ( maybe an extension of the mast )
& a longer than 1/2wave mast above the isolator & choke as seen in The DB's models,
I don't know why I can't see all the models posted, not even if I use a VPN to bypass the current UK governments stupid ban on hosting sites
,
I am trying to decide if with the full size upper radiator & correct mast length it could have 3/4wave of in phase radiation,
Time to have a route in the garrage to see what tubes I have.
I am not butchering my original Astroplane so I would use the "old CTE top-one" bracket that Eddie Marconi (RIP) sent me years ago,
It would have a full 1/4wave upper radiator ( maybe an extension of the mast )
& a longer than 1/2wave mast above the isolator & choke as seen in The DB's models,
I don't know why I can't see all the models posted, not even if I use a VPN to bypass the current UK governments stupid ban on hosting sites
,I am trying to decide if with the full size upper radiator & correct mast length it could have 3/4wave of in phase radiation,
Time to have a route in the garrage to see what tubes I have.
I am making new base antenna plans. My question is has anyone ever co-phased two Astroplane antennas together. There is a wooden utility shed 50 feet from the residence, about 9 foot high roof, building about 12 feet long. I figure I can easily mount 2 tripod mounts on the roof then use 2- 5 foot flanged mast sections to get the antennas 10 feet above the roof. The setup will be two Astroplanes about 19 feet off the ground and 9 feet apart. 1:1 Ugly Balun at the ground and then use PVC pipe buried to run the coax back to the house. The shed has electricity, and its dry, so I was thinking about actually setting up my RM KL503HD and a radio in the shed to test the setup. and then keep the KL503HD hook up in the shed to actually have the extra power as close to the base of antenna as possible. Does this idea sound workable or it it flawed in many ways?
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Co-phasing antennas lowers the real resistance just like putting resistors in parallel, so if your feed point is 50 Ohms on each antenna, you will have a real resistance of 25 Ohms creating a 2:1 SWR.
Can you get around this with transmission line impedance matching?
Maybe, if you can fabricate 35 Ohm coaxial line 1/4 wave length long that then splits into your 50 Ohm coax that goes to each antenna.
What might be a lot less work is adding a director or reflector.
Can you get around this with transmission line impedance matching?
Maybe, if you can fabricate 35 Ohm coaxial line 1/4 wave length long that then splits into your 50 Ohm coax that goes to each antenna.
What might be a lot less work is adding a director or reflector.
Use two 75ohm coaxial matching transformers and install the antennas 9 feet apart.
Since RG-11 is the same size as RG-8, just use two 1/4 waves of it or 9 feet x .81 velocity factor or about 7 feet 4 inches with normal connectors, like two 75ohm patchcords, one from each antenna to a T connector, and the 50ohm coax going to your radio screwed into the bottom of the T connector.
A 1/4 wave of 75ohm transforms 50ogms at one end to 100ohms at the other end.
Two 100ohm impedances in parallel across the top of the T connector becomes a 50ohm impedance at the bottom of the T connector.
Have fun & 73!