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Phasing Antennas


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#1 taco6513

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Posted 25 February 2019 - 07:58 AM

How would you go about Phasing 2 DB420's together?

Thanks 

WCRW870



#2 Corey

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Posted 25 February 2019 - 09:16 AM

How would you go about Phasing 2 DB420's together?

Thanks 

WCRW870

 

For what reason? The 420 is already a great antenna, I can't electrically see any benefit to phasing two of them together.

 

Corey


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Just My $.02

 

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#3 Elkhunter521

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Posted 25 February 2019 - 01:07 PM

Hi Taco6513,
The only benifit of stacking your antennas, considering the line of sight characteristics of the frequency, would be area saturation. A 3 element yagi would be simpler and more effective.
Be vewy vewy quiet.
I'm listening to my wadio!

#4 Jones

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Posted 25 February 2019 - 11:07 PM

I also ask: WHY?  The DB420 is already a stacked phased array of 16 folded dipoles with an omni gain of 14 decibels. Why do you need more?



#5 taco6513

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Posted 25 February 2019 - 11:28 PM

The antenna is a 9.2db gain in omni set up or 10.4 and  the pattern looks like an egg. Every time you double the antenna size you gain 3db. This would take you from 9.2 to 12.2 db gain in omni set up. Would give you a more sensitive system for walkie talkies. So if you could phase 4 together you would get 15.2db gain. The better the antenna gain and the lower the feed line loss the better a repeater would preform. If you can do it why not?



#6 RCM

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Posted 26 February 2019 - 12:07 AM

The antenna is a 9.2db gain in omni set up or 10.4 and  the pattern looks like an egg. Every time you double the antenna size you gain 3db. This would take you from 9.2 to 12.2 db gain in omni set up. Would give you a more sensitive system for walkie talkies. So if you could phase 4 together you would get 15.2db gain. The better the antenna gain and the lower the feed line loss the better a repeater would preform. If you can do it why not?

Depends on the terrain. In a mountainous area for example, more gain is not necessarily better.



#7 Jones

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Posted 26 February 2019 - 11:23 AM

I agree with RCM.

 

As I explained elsewhere on this site, too much gain is not a good thing on UHF.  You will wind up with such a narrow beam-width that you wont be able to hit the repeater when you are in close to it.

 

Antenna height is king.  You will get better results from a 3dB antenna at 100 feet than you would with a 12dB antenna at 50 feet... especially in hilly or mountainous terrain.


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#8 Corey

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Posted 26 February 2019 - 04:29 PM

Also, Gain has nothing to do with RX..... If you need better sensitivity try using a filter tuned to the frequency, into a pre amp and then you need to pad out any gain from the preamp that is above the noise floor.


Just My $.02

 

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#9 RCM

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Posted 26 February 2019 - 09:28 PM

Gain works both ways. RX as well as TX.



#10 Corey

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Posted 27 February 2019 - 08:57 AM

I guess everything I have ever learned is wrong, guess I should sell my Areoflex and Sitemaster.


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Just My $.02

 

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#11 RCM

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Posted 27 February 2019 - 10:24 AM

Point a Yagi antenna at a weak signal, then turn the antenna away and see what happens to the signal. You won't need high dollar test equipment to hear the difference.



#12 berkinet

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Posted 27 February 2019 - 10:28 AM

Gain works both ways. RX as well as TX.

Antenna “Gain” might reduce your S/N ratio, especially in the case of a directional antenna, because you will be receiving less noise and competing signals. But, it will not impact the signal strength of the desired signal. In the case of an omni directional antenna, the impact is really minor since you really don’t hear much from
directly overhead or below the antennna.
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Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth.

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#13 Corey

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Posted 27 February 2019 - 10:46 AM

Antenna “Gain” might reduce your S/N ratio, especially in the case of a directional antenna, because you will be receiving less noise and competing signals. But, it will not impact the signal strength of the desired signal. In the case of an omni directional antenna, the impact is really minor since you really don’t hear much from
directly overhead or below the antenna.

 

Trouble is most people dont understand what S/N ratio, insertion loss, return loss, impedance, noise floor, velocity factor etc even are. The Yagi example has noting to go with gain at all. I have shown countless people using calibrated industry standard equipment RX gain is nothing more then S/N. If you take a 3dB Yagi and a 18dB yagi, mount them in a fixed position at a fixed signal the uV level received by the test equipment is going to be the same. This is why filtering, pre-amps and attenuator's have a place. Simple really, a filter to reduce the S/N ratio and provide adjacent channel rejection, pre-amp to boost the signal and proper attenuation to lower the noise floor.


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Just My $.02

 

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#14 RCM

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Posted 27 February 2019 - 04:29 PM

Call it whatever you like, but antennas with greater gain also have greater effective area which increases received signal strength. When you double or quadruple the size of the antenna you pick up more noise and more of the desired signal equally.



#15 Corey

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Posted 27 February 2019 - 05:45 PM

Antenna gain is selected based on the site and required coverage area. It is a total misconception that more gain is better. Depending on the antenna height and terrain you can do more damage then good with higher gain. Site engineering is an important part of any system, science and methodology will always provide the best results over what one may think. Unless you are stacking UHF Yagis you will gain nothing by phasing omni's together, you would be better off setting them up diversity using power dividers but this involves its own engineering and the proper test equipment. Co phasing omni's was and still is popular for 10 and 11 meter but that is HF AM not UHF.

 

I currently have several DB-420, DB-411, DB-408, DB-404 and a single Sinclair SC329-HF2LDF in use at different sites both part 90 Commercial and GMRS. Each one selected for the installation and desired coverage. The antenna is the biggest factor in any radio system with the coax the second, trust the science. I have and still do see allot of people wasting money and being unhappy with system performance over bad antenna selection.

 

Just my $.02 

Corey


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Just My $.02

 

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#16 quarterwave

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Posted 01 March 2019 - 09:11 AM

What is the emoji for Nauseated?  :wacko:


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#17 RF Medic

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Posted 07 March 2019 - 04:00 PM

This whole thread hurts and is an absolute waste of time for the actual results. You would have more loss in the phasing harnesses than you would gain.

 

Put up the DB420 and enjoy the hell out of a kicka** antenna.


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#18 n4gix

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Posted 07 March 2019 - 04:30 PM

Now this is a phased array! It is the infamous "Duga Woodpecker" in Russia. :lol:

CWDj7.png


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#19 Corey

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Posted 09 March 2019 - 10:49 AM

OMG the Woodpecker, I remember this famous numbers station from the 80's


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#20 PastorGary

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Posted 09 March 2019 - 11:41 AM

Speculation was that it was an over the horizon missile launch 'radar' detection system. ERP was thought to be over 10 megawatts and was heard back then on a number of HF frequencies between 7 and 19 Mhz.  It routinely wiped out the transmissions from WWVH in Hawaii.






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