Topband: 160m portable operating
Jon Zaimes AA1K
jz73 at verizon.net
Wed Sep 12 09:05:38 EDT 2007
Sounds like you have some nice room to play with ...
steve d wrote:
> How many radials should I put out?
A dozen will get you started, 30 is good, 60 is 95 percent of optimum,
and 120 is the broadcast-industry "standard." 200 just gets you bragging
rights and costs a lot of copper (but I've done it).
> 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,
It helps to get a copy of the survey for the property -- many
governments now have these online, or the property owner may have one
from when it was purchased. Then you can plot out the location of
Beverages and the transmit antenna before you begin.
> 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.
It's nice to have a half wave or more separation between TX and RX
antennas to avoid coupling of noise, but if you must go closer to get a
Beverage in the right direction, so be it. I have several Beverages as
close as 10-20 feet to towers in some cases. There's noise pickup, but
they hear better than a Bev. in the wrong direction or a shorter one
placed elsewhere. You can also de-tune the TX antenna on RX to avoid
> 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?
You can use a pot and adjust for best f/b, though I've never gotten
around to doing that with mine. The value may change through the year as
ground conductivity changes -- I know one ham who said he had to
re-adjust for different seasons. Most of mine are around 550 ohms and
seem to work OK. Height above ground will affect this value (mine are
generally around 10 ft). Check the reflector archives, ON4UN's Low Band
DXing book, and w8ji.com for more info on this.
> 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.
It would have to be a very long Beverage to be that narrow a beamwidth.
For 500-800 ft single wires, more like 50 degrees if I recall. I would
start with Europe (45 degrees from here), Caribbean/South America (162)
and due west for VK/ZL/JA. Later add NW for JA. Then anytime a rare one
is due to come up and you don't have one in that direction, add one. (I
now have about 20, most phased pairs). An old rule I follow: Better to
have a short Beverage in the right direction rather than any Beverage in
the wrong direction.
> Steve, KC8QVO
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