Topband: 160m portable operating
kc8qvo at yahoo.com
Tue Sep 11 12:51:30 EDT 2007
Hi All, I was at my friend's new property over the weekend operating in the VHF contest so I got to scope out the place.
There are lots of tall trees, I would say in the neighborhood of 60'. That would be plenty to string up an inverted L. The other option would be to raise my aluminum tent pole mast as high as I can get it (could go up 70-75'). As someone pointed out before, ground radials are going to be the only option since 1/8w (to get away from ground coupling) is 60 some feet on 160 - thats as high as the trees. How many radials should I put out? I know the more the better, but there has to be a point where performence vs. number of radials is decent enough to not go further.
Heres where I am with the rx antenna idea: There is space for beverages, and there should be plenty of time to set everything up. I would like to center the feedpoint, that way I have 1 feedline going out there. I will also need a control cable for the switchbox as well as DC feed (can combine that in to the control cable) for the preamp (I could run that through the coax, but Im not a big fan of that method). I am not sure what the dimensions of the property are, Ill have to investigate this further. The issue I might run in to is there wont be enough space from the center out to string up a decent size beverage. In this case, I might need multiple feedpoints - which would cost more $$ (more cable, more preamps, more impedance matchers).
Another issue is the location of the transmitting antenna vs. the location of the beverages. As the idea stands, the transmitting antenna is going to be in between the beverages.
What length should I be consitering for a decent beverage? 500-800'? How about grounding them? I know I need a ground rod at each end and a terminating resistor at the far end. What is the best way to go about figuring out the termination resistance? Can I use some kind of pot to be able to adjust it, or should I figure out what the resistance should be and put resistors in?
The next question is how many should I lay out? If the beamwidth is 10deg (I think thats what they are, around there) then, to get all directions I would need 36. When you factor in the cost of the wire, relays for switching, ground rods, and resistors.. hmm, thats a LOT of $$. Are there any directions I should really concentrate on? Europe, Africa, South America, Australia, Asia? Im sure I can eliminate the majority of that 36 by focusing on a few good locations, rather than trying to accomodate everything.
I still have plenty of time to think about this HI. Ive just got my wheels spinning right now.
Pinpoint customers who are looking for what you sell.
More information about the Topband