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RX ANTENNAS FOR LOW BANDS
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by CX6VM on June 18, 2005
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Hi,
Will want to ask wich RX antenna is recomended for 160 & 80 mts. My idea is to have a inv. L for 160mts and 3-4 slopers with relays for 80mts, but I will need something else for RX. No space restriction, so wich RX antenna will be the IDEAL in this situation? Beverage? LOOP?, another?.
Thanks,
Jorge
CX6VM
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RE: RX ANTENNAS FOR LOW BANDS
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by PA5AT on June 20, 2005
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Hi Jorge,
I am ON5KQ, ex PA5AT and low-band operator from M/M contest station PI4COM.
If you have no space restriction, I would recommend Beverage antenna's. Ultimate systems are usually phased beverages!
Here in Europe our main problem is QRM from other EU's especially from back of the antenna: When I am calling on 80/160m to western direction to work W/VE or south and central america, usually the SP/UA stations try the same.... and put signals like 59+40db and more on my TX-antenna. Therefore I want to increase F/B ratio of my RX-antenna as much as possible: phased beverages do the job !
This is 2 beverages side by side about 5 m spacing, but one beverage's feedpoint is about 30m further than the other:
feedpoint 1....................................600 Ohm resistor
o===========================o
;;;;;;;;; o===========================o
;;;;;;;;feedpoint 2......................................600 Ohm
-35db F/B --------------> max. reception
feedpoint 2 = feedpoint 1 + 30m
As indicated the F/B ratio is extremly high !
If you use 2 wire beverages, you can even switch direction by 180 degrees... (very helpful!)
If you in Uruguay don't have so much local qrm, you probably don't need so high F/B, but more directivity (the front lobe of the antenna then will be come much narrower):
make spacing for 160m about 100m and for 80m about 50m (the half). Then you will have extremly sharp front lobe with about still 25db F/B and front to side rejection.
Disadvantage of this system is, that it is optimum only for one band. Also due to the narrow lobe you need every 30degrees another system....
Please refer to the excellent website of Tom: www.w8ji.com
Greetings from Belgium,
op Ulli, ON5KQ
(ex PA5AT)
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