Can 2 yagi antennas be combined with a phasing harness for different directions?

[Riktar]

Most of my needs (at distances over 10 miles) are in 2 specific directions. Using just a single yagi pretty much covers my "local" (under 5 miles) needs.

So instead of using a rotator on a single antenna I was wondering if it would be simpler/more efficient to have two yagis pointing at 2 individual compass points?

[gortex2]

a commercial splitter will be at least 3db of loss so you may loose what you have now with the 5 mile range. You could get a decent omni antenna most like for the cost of the splitter. Splitting a TX antenna is not as simple as a T in between them. 

https://www.dbwave.com/pdf/medpowercombinersplitter/PAPD0200700270B.pdf

Not knowing the power level you are talking about here is a 50 watt, 3db port loss with N connector that goes for around $330.00. You can get a DB404 for a few dollars more.

[Riktar]

Thanks for the reply. As to the power level, I am using a Kenwood TK-8180H so 45 watts output.

And EGADS that is an eyewatering price!! Not to mention the 3db loss....

[gortex2]

Well to be honest that isn't a large price. I have installed ones that cost many times more than that in commercial applications. As with all radio services antenna systems can make or break a radio system. 1/2 watt UHF radio on a 5000' Mountain can talk alot further than a 1/2 watt radio in a valley. Antenna systems vary with costs and quality thats what gets the whole repeater debate going all the time. In the end you get what you pay for and if you have expectations of a Ferrari on a Fiero budget you will not be happy. 

[SteveShannon]

23 minutes ago, Riktar said:

Thanks for the reply. As to the power level, I am using a Kenwood TK-8180H so 45 watts output.

And EGADS that is an eyewatering price!! Not to mention the 3db loss....

Just buy two yagis, two coax cables, and an antenna switch. It still won’t be cheap but you won’t have to deal with 50% signal losses. 

[Riktar]

It wasn't the $$$ amount of the DB404 that was the egads part. It was the cost of the splitter I was commenting on.

And yes on the 2 yagis. I do have a coax switch already from a prior setup. I just thought it would have been convenient to have both antennas "on" at the same time without having to remember to flip the switch on the coax switch.

But for that price, I will bear with the added effort of flipping a switch....

[Radioguy7268]

Years back there was an interesting write up that a club did - where since they were going to have to sidemount their transmit antenna - they ended up going with a 3 sector antenna system using stacked 3dB yagi antennas, and used a phased harness to make it all work. At least, that's  how I remember it, and now I can't find it online with a weak search attempt. I do remember that it was an interesting article, wish I could find it again.

[wayoverthere]

I found this article with a quick Google...haven't fully digested it yet (it's deep for reading on the phone), but it looks like it has some information in the ballpark, and makes it look like the idea isn't totally out of the realm of reality.

How far apart are the two compass points?

[WRQX963]

I would suggest using two antennæ with an A/B switch.

[Riktar]

1 hour ago, wayoverthere said:

I found this article with a quick Google...haven't fully digested it yet (it's deep for reading on the phone), but it looks like it has some information in the ballpark, and makes it look like the idea isn't totally out of the realm of reality.

How far apart are the two compass points?

Pretty close to 150 degrees.

I did some searching on how to make a phase harness. If I understand the theory I need 2 75 ohm coax feeds to the antenna(s) and a 50 ohm feed that get connected to a coax splitter/combiner of sorts which is then connected (via the 50 ohm coax) to my radio. All the sites I found that mention how to do this are referencing VHF frequencies for the math and measurements. Still looking for someone who has done the math in the 462-467 range.

 

Edited May 31, 2022 by Riktar
added content

[Wyoduner]

You cannot realistically combine two yagis that are pointing in different directions.  Even if you were to properly phase the feedlines, the antennas themselves are out of phase - you would do more harm than good.  When you combine two yagis they need to be looking in the same direction and be the same distance electrically (via spacing the yagis or delay line in the phasing harness) from the signal source.

 

2 Yagis, 2 coax and  A/B switch is how it must be done.

 

Brad

[WRQX963]

1 hour ago, Riktar said:

If I understand the theory I need 2 75 ohm coax feeds to the antenna(s) and a 50 ohm feed that get connected to a coax splitter/combiner of sorts...

If you are using an actual splitter/combiner, then the impedances are already matched so do not use any 75Ω
(that would only be necessary if you were using an empty T-connector).
Do use the same amount of 50Ω cable, though, between the splitter/combiner and each antenna.
But I would still go with Wyoduner and recommend an A/B switch.

[deanq]

You most assuredly can. All you need is a correct phasing harness. This is how commercial repeater antennas work. They can be set up as a directional, to cover all four (or less) compass points.

[Riktar]

12 hours ago, Wyoduner said:

You cannot realistically combine two yagis that are pointing in different directions.  Even if you were to properly phase the feedlines, the antennas themselves are out of phase - you would do more harm than good.  When you combine two yagis they need to be looking in the same direction and be the same distance electrically (via spacing the yagis or delay line in the phasing harness) from the signal source.

 

2 Yagis, 2 coax and  A/B switch is how it must be done.

 

Brad

Then how does the DB-404 work? It consists of 4 folded dipoles which are combined by what appears to be a phasing harness. And they are not pointing the same way. Or is that because the folded dipole design allows that while the Yagi design does not?