Combining 2 antennas - wire or combiner? - Canadian TV, Computing and Home Theatre Forums
post #1 of 16 (permalink) Old 2019-02-27, 02:39 PM Thread Starter
PSS
Rookie
 
Join Date: Feb 2019
Posts: 9
Combining 2 antennas - wire or combiner?

I came across this article about combining two OTA antennas, with wire. https://www.bsntech.com/can-you-hook...a-tv-antennas/ Thoughts?

Did a search of the Forum, and couldn't find much about using wire instead of joiners/combiners? TY.
PSS is offline  
Sponsored Links
Advertisement
 
post #2 of 16 (permalink) Old 2019-02-27, 08:34 PM
Rookie
 
Join Date: Dec 2008
Location: Mississauga
Posts: 1,043
It probably works because both are yagi antennas pointed in exactly the opposite directions. The front to back rejection of each antenna is enough to prevent out of phase cancellations to occur. Just a guess.
Jorgek is offline  
post #3 of 16 (permalink) Old 2019-02-28, 08:09 AM
Rookie
 
Join Date: May 2017
Posts: 362
Clarify your intensions. There are 2 completely different scenarios:

1) 2 antennas (preferrably identical, but it's not a must) are used as phased array to increase gain by +2...3 dB

2) 2 antennas are pointed to different directions to different transmitters or to the same direction but at different bands (e.g. VHF + UHF)

In general, 2nd scenario is not possible, but if you are lucky and your transmitters work at different bands (UHF + VHF) you can use frequency diplexer
Yurii Pylypenko is offline  
 
post #4 of 16 (permalink) Old 2019-02-28, 09:23 AM
Rookie
 
Join Date: Nov 2009
Posts: 534
Quote:
...or to the same direction but at different bands (e.g. VHF + UHF)
This should be considered as a 3rd scenario that easily and successfully done all the time using a UVSJ combiner. Same direction, different direction for each antenna doesn't matter, it still works as you noted.
ProjectSHO89 is online now  
post #5 of 16 (permalink) Old 2019-02-28, 12:02 PM
Rookie
 
Join Date: Jun 2011
Location: 43° N, 81.2° W
Posts: 8,579
The linked article refers to two dissimilar antennas linked by #12 AWG electrical wire that looks like it is still in the original 2/3 conductor sheath. #12 AWG electrical wire is a disaster at TV frequencies. It's nowhere near the correct impedance, will have excessive SWR and may have dielectric losses.

That article is a perfect example of how not to install two antennas. The two antennas are dissimilar, too close together, not joined properly and pointed in different directions. The poster just got lucky and probably benefits from having strong, non-interfering signals in both directions.

p.s. I can get two channels with a paper clip. It doesn't mean it's a good TV antenna.
ExDilbert is offline  
post #6 of 16 (permalink) Old 2019-02-28, 01:02 PM
Rookie
 
Join Date: Oct 2008
Location: tarana
Posts: 1,320
Quote:
Originally Posted by PSS View Post
I came across this article about combining two OTA antennas, with wire. https://www.bsntech.com/can-you-hook...a-tv-antennas/ Thoughts?

Did a search of the Forum, and couldn't find much about using wire instead of joiners/combiners? TY.
I can confirm that the concept works. I took two, silver sensor antennas - mounted with an electrical junction box on a pole (I've seen them mounted individually on a pole as well), one pointed north and one pointed south, and then combining the two with a simple splitter in reverse, then fed to a satellite multiswitch. Works great - I get signals from both directions, and the feed is available anywhere I have a satellite drop, via a mixer-splitter.
tvmaster is offline  
post #7 of 16 (permalink) Old 2019-02-28, 05:53 PM
Rookie
 
Join Date: Nov 2008
Location: San Diego, CA
Posts: 3,396
I have analyzed various Vertically and Horizontally Stacked Antennas:
https://imageevent.com/holl_ands/stacked

It is fairly easy to connect two Identical Antennas pointed in Same Direction [cable lengths must be SAME Length] or Different Directions using a standard RF Splitter, as a Combiner connected in reverse [RF Combiner Mod]. However there is a 0.5 to 1.5+ dB LOSS in the RF Combiner due to Internal Loss as well as Gain, Phase and SWR Mismatch in the Ferrite Hybrid Transformer inside the RF Combiner:
Antenna Comparisons, Antenna Reviews, DIY Antenna Modifications, HDTV Antennas

It is NOT easy to design an interconnecting Harness using JUST Bare Wire (see for example my HHH or HVH, designed via Computer Optimization Software).....and is even more difficult using off-the-shelf 300-ohm Twinlead Transmission Lines (or typically better 450-ohm Ladder Line), since you can ONLY adjust the Length and NOT the Impedance [needed to turn it into an Impedance Transformer]....and there is high Loss when Wet/Snow/Ice.

In my HHH (Holl_ands Horizontal Harness) and HVH (Holl_ands Vertical Harness), the Optimizer finds not only the Optimum Total Length (must be MORE than the given Stacking Distance), but also the Variable Impedance (separation distance between the Harness Wires) of the Transmission Lines....both of which are significantly affected by PROXIMITY to all of the OTHER Wires in the Antenna (and vice versa).

If you make RANDOM choices, you're going to get RANDOM results, incl. the likelihood of poor SWR and possibly Gain Drop Outs on some Frequencies....
holl_ands is offline  
post #8 of 16 (permalink) Old 2019-02-28, 10:46 PM Thread Starter
PSS
Rookie
 
Join Date: Feb 2019
Posts: 9
Quote:
...If you make RANDOM choices, you're going to get RANDOM results, incl. the likelihood of poor SWR and possibly Gain Drop Outs on some Frequencies....
Thanks all, for the replies. Lots to learn and think about, to do it the right way, and not just random luck and trial and error (which is likely an exercise in frustration)
-p
PSS is offline  
post #9 of 16 (permalink) Old 2019-03-01, 02:56 PM
Rookie
 
Join Date: May 2017
Posts: 362
Quote:
However there is a 0.5 to 1.5+ dB LOSS in the RF Combiner due to Internal Loss
this is true only if power combiner/splitter has isolation between ports, as in https://en.wikipedia.org/wiki/Wilkinson_power_divider
if no isolation (not a Wilkinson type, or frequency differs from wilkinson design frequency) - half of signal will go to port and will be radiated by second antenna
Yurii Pylypenko is offline  
post #10 of 16 (permalink) Old 2019-03-01, 03:38 PM
Rookie
 
Join Date: Dec 2008
Location: Mississauga
Posts: 1,043
"if no isolation (not a Wilkinson type, or frequency differs from wilkinson design frequency) - half of signal will go to port and will be radiated by second antenna"
So if half of the signal goes out the other port to the antenna, is this not a loss?
Jorgek is offline  
post #11 of 16 (permalink) Old 2019-03-02, 03:45 AM
Rookie
 
Join Date: May 2017
Posts: 362
It's a loss, but not 0.5-1 dB loss.
In lossless divider (no insertion [no heat, no radiation, no mismatch] loss) it is 3 dB
In lossy/mismatch - energy flow depends on matching condition
Yurii Pylypenko is offline  
post #12 of 16 (permalink) Old 2019-03-02, 02:38 PM
Rookie
 
Join Date: Nov 2008
Location: San Diego, CA
Posts: 3,396
FYI: My old Summary re. Alternative Antenna Combiners:
https://www.digitalhome.ca/forum/81-...ml#post2884273

And my old (Mar 2009) Summary of Low Loss Wilkinson Stripline Couplers....note only Partial Band Coverage for most but not all Couplers. Typical Internal Loss is 0.2 to 0.5 dB, irrespective of whether 2-Port, 4-port or whatever. Frequently used to sum Multiple Output Stages in an RF Amplifier, so may or may NOT be suitable as a Low-Loss Combiner....so check with manufacturer:
https://www.avsforum.com/forum/25-hd...l#post16072450

MACOM App Notes for a Ferrite Hybrid Transformer Splitter/Combiner:
http://web.rfoe.net:8000/ziliaoxiaza...63144/m561.pdf [Incl. Mismatched Inputs + Wilkinson]
http://web.rfoe.net:8000/ziliaoxiaza...52359/m560.pdf
http://web.rfoe.net:8000/ziliaoxiaza...17591/m568.pdf

In a Ferrite Hybrid Transformer [typical Cable Splitter/Combiner], internally there is a 75-ohm Load Resistor connected to the port "D", also called the DIFFERENCE PORT. As illustrated in App. Note M586 Figure II (first entry), when there is a Phase Difference between the two Input Ports, internal Port "D" dissipates the "Difference". And the "3 dB" Combining Gain (less Internal Losses) is ONLY realized when Input Signals are EQUAL, with the difference being dissipated in the Internal Load Resistor on Port "D"....see MACOM App Note M561.

Power coming in on one port and going out the OTHER is measured by the ISOLATION Spec...which is quite high in ALL of the above Splitter/Combiners....incl. Wilkinson. I don't know of any of THESE types that have significant energy going from one Input Port to another.

Last edited by holl_ands; 2019-03-02 at 03:05 PM.
holl_ands is offline  
post #13 of 16 (permalink) Old 2019-03-02, 02:47 PM
Rookie
 
Join Date: May 2017
Posts: 362
That is true only for combining in-phase equal-magnitude signal (i.e. using phased array of N antennas pointed to the same transmitter).
If second port has zero signal (hence this antenna is pointed in different direction), this zero-voltage cannot prevent energy flow (no port isolation)
Yurii Pylypenko is offline  
post #14 of 16 (permalink) Old 2019-03-03, 04:51 PM
Rookie
 
Join Date: Nov 2008
Location: San Diego, CA
Posts: 3,396
Which type of Combiner??? And can you provide supporting information????
holl_ands is offline  
post #15 of 16 (permalink) Old 2020-02-16, 09:00 PM
Rookie
 
Join Date: Apr 2019
Location: Sherbrooke, Qc
Posts: 17
Combining 2 antennas from 2 directions using a reverse splitter return a loss of 3-4 dB on each antenna's signal. But would it be possible to pick up the signal from one antenna and retransmit it at low power over-the-air in front of the other one ?
cuivreux is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Canadian TV, Computing and Home Theatre Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome