Hooking up two antennas

[tbharper]

My setup includes a Larsen NMO150/450/800 with a ground plane on a 34 ft mast using 50 ft of LMR-400, and a D130NJ Discone on a 20 ft mast with 50 ft of LMR-400, with both antennas separated by about 20 ft. I’m looking to connect them to a Stridsberg MCA204M multicoupler and wondering if this would be the best way to combine them to a Mini-Circuits ZFSC-2-1.

https://www.digikey.com/en/products/detail/mini-circuits/ZFSC-2-1-N-/21727775?gclid=d11f3f185c47111f4c0456aee81516e1&gclsrc=3p.ds&msclkid=d11f3f185c47111f4c0456aee81516e1

 

[prcguy]

My setup includes a Larsen NMO150/450/800 with a ground plane on a 34 ft mast using 50 ft of LMR-400, and a D130NJ Discone on a 20 ft mast with 50 ft of LMR-400, with both antennas separated by about 20 ft. I’m looking to connect them to a Stridsberg MCA204M multicoupler and wondering if this would be the best way to combine them to a Mini-Circuits ZFSC-2-1.

https://www.digikey.com/en/products/detail/mini-circuits/ZFSC-2-1-N-/21727775?gclid=d11f3f185c47111f4c0456aee81516e1&gclsrc=3p.ds&msclkid=d11f3f185c47111f4c0456aee81516e1

You wouldn't want to directly combine those two antennas as it won't benefit anything and may reduce signal levels if signals combine out of phase from the two antennas. If you had two antennas for two different bands like a VHF and UHF or a Discone and an 800 antenna you can combine those with a diplexer that will only allow the specific frequency range of each antenna to be combined and avoid out of phase problems. The 2-way divider you linked would actually cause a 3dB loss per antenna and you would only gain a little of that back if by accident some signals were combined in phase but that would be doubtful.

The only other time you might combine antennas is with two identical narrow band Yagi antennas mounted at a specific distance apart so signals will be in phase. Then you can combine and get up to 3dB improvement. The reason you can get 3dB more gain by combining identical antennas using a divider that has 3dB loss is the act of combining antennas in phase actually gives you a 6dB improvement but you loose 3dB in the divider.

 

[tbharper]

You wouldn't want to directly combine those two antennas as it won't benefit anything and may reduce signal levels if signals combine out of phase from the two antennas. If you had two antennas for two different bands like a VHF and UHF or a Discone and an 800 antenna you can combine those with a diplexer that will only allow the specific frequency range of each antenna to be combined and avoid out of phase problems. The 2-way divider you linked would actually cause a 3dB loss per antenna and you would only gain a little of that back if by accident some signals were combined in phase but that would be doubtful.

The only other time you might combine antennas is with two identical narrow band Yagi antennas mounted at a specific distance apart so signals will be in phase. Then you can combine and get up to 3dB improvement. The reason you can get 3dB more gain by combining identical antennas using a divider that has 3dB loss is the act of combining antennas in phase actually gives you a 6dB improvement but you loose 3dB in the divider.

Thanks for the reply, as I wasn't sure.

 

[Ubbe]

I would connect each antenna to its own receiver/scanner. Then make notes on what antenna works best for a particular system or frequency that are more difficult or impossible to receive from the other antenna/receiver and then divide up the systems and frequencies between receivers to get the best reception. I use 6 different antennas split up between different scanners and receivers.

If you have a multicoupler and need to feed several scanners then use that multicoupler with the antenna where it makes most use to those other receivers. You can do your own multicoupler using a $30 preamplifier based on a PG103+ amplifier and then use a $10 CATV splitter and a suitable $5 attenuator to give a final gain of 3-6dB at the splitters output and it will perform better than a Stridsberg.

I once had two antennas with their coaxes connected together using a T-connector and I had several small coaxes of different length like 5-10-20 inches, that would be 1/8 and 1/4 wavelengths of a frequency, and inserted them between T-connector and one coax to make it longer and depending of the direction of the source and its frequency I could then receive that signal stronger when the two antennas where more or less in phase with each other than trying to receive using just one antenna. Another direction or frequency or using the wrong coax length would make the signal worse than using a single antenna. Any strong signal could still be received even using the wrong phase but a single, very noisy, signal could be made to be received stronger.

There are QRM eliminator boxes that have phase controllers to cancel out interference by using two antennas but can equally well be used to instead add two signals in phase. Then that box would simulate different length of coax to one antenna. But most of them have components values that make them suitable only for shortwave frequencies.

/Ubbe

 

[prcguy]

I would connect each antenna to its own receiver/scanner. Then make notes on what antenna works best for a particular system or frequency that are more difficult or impossible to receive from the other antenna/receiver and then divide up the systems and frequencies between receivers to get the best reception. I use 6 different antennas split up between different scanners and receivers.

If you have a multicoupler and need to feed several scanners then use that multicoupler with the antenna where it makes most use to those other receivers. You can do your own multicoupler using a $30 preamplifier based on a PG103+ amplifier and then use a $10 CATV splitter and a suitable $5 attenuator to give a final gain of 3-6dB at the splitters output and it will perform better than a Stridsberg.

I once had two antennas with their coaxes connected together using a T-connector and I had several small coaxes of different length like 5-10-20 inches, that would be 1/8 and 1/4 wavelengths of a frequency, and inserted them between T-connector and one coax to make it longer and depending of the direction of the source and its frequency I could then receive that signal stronger when the two antennas where more or less in phase with each other than trying to receive using just one antenna. Another direction or frequency or using the wrong coax length would make the signal worse than using a single antenna. Any strong signal could still be received even using the wrong phase but a single, very noisy, signal could be made to be received stronger.

There are QRM eliminator boxes that have phase controllers to cancel out interference by using two antennas but can equally well be used to instead add two signals in phase. Then that box would simulate different length of coax to one antenna. But most of them have components values that make them suitable only for shortwave frequencies.

/Ubbe

If the OP were to use each antenna into a specific scanner the Larsen should work a little better than a Discone in the 150-165MHz area, 450-512MHz area and much better in the 700/800MHz area. The Discone will work noticeably better than the Larsen in the VHF and UHF air bands and ok in the general 118 to 512Mhz range.