Dual direction yagis one transceiver

mtand73

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Im following a QRT article for recycling a TV antenna to a 2m yagi and I had a thought.
If I have enuf parts to make 2 of them can I point them in two different directions and run it on one coax to my transceiver without issues?
I Google it but as a new ham the information I found was pretty high over my head lol
Thanks for any information you can provide
Mike
KF0AWL
 

buddrousa

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Co-phasing is normally done with 2 antennas of the same type with matching harnesses so I am not sure how this would work for you.
 

prcguy

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If you use a power divider or co-phasing harness to run two Yagi antennas pointed in different directions, you will loss about 3dB of gain on the antennas. So if each Yagi is rated 10dB gain you will end up with 7dB gain Yagis. At that point you might be better off with a 10dB gain omni.
 

mtand73

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If you use a power divider or co-phasing harness to run two Yagi antennas pointed in different directions, you will loss about 3dB of gain on the antennas. So if each Yagi is rated 10dB gain you will end up with 7dB gain Yagis.
Now that I can understand thanks!
Now if I use a multi antenna switch I'll get normal gain out of each one correct?
 

KC4ASF

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I think I know the answer to this question now but I will ask anyhow. I have 4 seven element 850-900mhz in my attic on a single pole. (no external antennas allow) These antennas are individually aimed N, E, S, W. Good grade 75ohm coax about 12" on each one feeding into a multi coupler with a 25db RF amplifier. Which feeds into a single 75ohm coax of 25' into my radio room. I am not getting the signal increase on stations around 25 miles out as I expected. Is the reason that the antennas are losing so much signal because of the way I have the antennas setup?
 

prcguy

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You mention a multicoupler but is it a combiner or RF splitter used backwards to combine? If so you would be loosing about 6dB of signal off each Yagi in the process and possibly more. An ideal four way divider has 6dB loss but some TV types can have 7dB or more loss. If all the Yagi's are aimed in different directions then you will have the total loss of the combiner in effect for each antenna, so if each Yagi is 10dB gain you might have 3 to 4 dB of overall gain in sort of an omni directional pattern. If this is the case just get a high gain omni and be done with it.

If you have all four Yagi's pointed in the same direction and at the correct spacing then combine them, that will add about 6dB gain beyond whatever the individual gain of each antenna is.

Your 25dB gain amplifier is way too much for what you describe, reduce that to maybe 6dB otherwise you are probably overloading your receiver and/or have a very high noise floor. Whatever you lost in the combining process or have never picked up cannot be made up with amplifier gain. It has to be done at the antenna.

I think I know the answer to this question now but I will ask anyhow. I have 4 seven element 850-900mhz in my attic on a single pole. (no external antennas allow) These antennas are individually aimed N, E, S, W. Good grade 75ohm coax about 12" on each one feeding into a multi coupler with a 25db RF amplifier. Which feeds into a single 75ohm coax of 25' into my radio room. I am not getting the signal increase on stations around 25 miles out as I expected. Is the reason that the antennas are losing so much signal because of the way I have the antennas setup?
 

KC4ASF

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You mention a multicoupler but is it a combiner or RF splitter used backwards to combine? If so you would be loosing about 6dB of signal off each Yagi in the process and possibly more. An ideal four way divider has 6dB loss but some TV types can have 7dB or more loss. If all the Yagi's are aimed in different directions then you will have the total loss of the combiner in effect for each antenna, so if each Yagi is 10dB gain you might have 3 to 4 dB of overall gain in sort of an omni directional pattern. If this is the case just get a high gain omni and be done with it.

If you have all four Yagi's pointed in the same direction and at the correct spacing then combine them, that will add about 6dB gain beyond whatever the individual gain of each antenna is.

Your 25dB gain amplifier is way too much for what you describe, reduce that to maybe 6dB otherwise you are probably overloading your receiver and/or have a very high noise floor. Whatever you lost in the combining process or have never picked up cannot be made up with amplifier gain. It has to be done at the antenna.
OK. It is the coupler in reverse. It ends up at my SDS200. I will have to rethink my experiment.
Thanks
Ben
 

dlwtrunked

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...

If you have all four Yagi's pointed in the same direction and at the correct spacing then combine them, that will add about 6dB gain beyond whatever the individual gain of each antenna is.
...
I am sure you also meant to add the right cable lengths (so phasing would again be right) but you may have meant to imply that with "correct spacing".
 

prcguy

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Yes, correct spacing between antennas, equal cable lengths, wind behind you, etc. Gain will go up and beam width will narrow when four antennas are phased properly in the same direction.

I am sure you also meant to add the right cable lengths (so phasing would again be right) but you may have meant to imply that with "correct spacing".
 

alcahuete

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OK. It is the coupler in reverse. It ends up at my SDS200. I will have to rethink my experiment.
Thanks
Ben

Why play around with all these antennas? Get a cheap and simple TV antenna rotator and spin a single yagi in your attic, assuming there's space for it. Should work great. Of course, you're going to have to spin it based on what you want to hear. If you're looking for an omnidirectional pattern, then buy a high gain omni.
 

KC4ASF

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Why play around with all these antennas? Get a cheap and simple TV antenna rotator and spin a single yagi in your attic, assuming there's space for it. Should work great. Of course, you're going to have to spin it based on what you want to hear. If you're looking for an omnidirectional pattern, then buy a high gain omni.
I have one and was rather disappointed with it. I regularly experiment with increasing the signal of the simulcast stations in my fringe areas. It seemed like a great idea at the time a couple months ago when I dreamed up using 4 beams. I guess my best bet now is to checkout the cable lengths and other issues mentioned. Since I am not allowed to go outside the house now it will give me something to do.
 

mtand73

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Ok I have run into a query.
Im supposed to feed my matching stub into my DE, and run the braids in the center to my SO239 or coax feedline.
What braid at the center goes to were on the 239/ feedline?
Im going to run it directly to coax but they specifically say what to solder each of my braid to!
Is it one to center and one to outside braid of my feed coax?
Attached photo shows were im at.
 

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mtand73

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Ok thanks
I might have been over thinking it or something I just couldn't figure out what I was seeing n reading lol
 

W5lz

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Can it be done? Yes, but. There will be complications, a different way of doing things. Will distnace apart affect either/both antennas? Yes, but it's not insurmountable. Is it worth doing? I don't know. If those two directions are not too far apart, maybe not. Split the difference if you can.
 
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