Antenna combiner

Discuss commercial and home made antennas.
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illllm
Posts: 22
Joined: Tue Apr 17, 2018 5:41 pm

Antenna combiner

Post by illllm » Thu Sep 27, 2018 9:12 pm

Can i combine 4 or 5 different antennas using this? Linear 2534 Channel Plus 4-Way Splitter/Combiner

https://www.amazon.com/gp/product/B0000 ... BKXO&psc=1

one for FM, one wide band for GHz frequencies, one for Am HF, one loop, one MiniWhip.

JEL
Posts: 123
Joined: Wed Feb 07, 2018 2:08 am

Re: Antenna combiner

Post by JEL » Thu Sep 27, 2018 11:29 pm

I tried something similar, but with only 2 antenna-inputs.

It halfway worked, but not without issues.

The problem, simply put, is that the signals from the multiple inputs are mixed together and thus can null each other out on some frequencies.

So you may degrade reception.

But on frequencies where the setup resonates, you may get a slight boost.
It's not trivial, sadly.

rtlsdrblog
Site Admin
Posts: 2163
Joined: Mon Nov 19, 2012 11:54 pm

Re: Antenna combiner

Post by rtlsdrblog » Fri Sep 28, 2018 12:01 am

It's very difficult to get good performance by combining antennas. But it may end up being good enough for your purposes.

snn47
Posts: 147
Joined: Tue Dec 27, 2016 11:00 pm

Re: Antenna combiner

Post by snn47 » Mon Oct 01, 2018 9:52 pm

Combining different frequency ranges is possible, but requires that the filters provide separation between the antennas in frequency,

This requires the cutover frequency ranges of filters and antennas don’t overlapp. If you combine the same signal received by different antennas, due to varying phases they mostly will cancel each other.

For your antennas, a combiner would need to consist of a LP-filter for AM, a BP filter for your HF antenna, another BP for the FM antenna and a HP filter for the GHz antenna. The combiner you’ve shown seems to be for BC/TV use and therefore will not work for you. Due to the high attenuation I would suggest to use a mechanical antenna switch,

P-40 Warhawk
Posts: 84
Joined: Thu Jun 26, 2014 11:55 pm

Re: Antenna combiner

Post by P-40 Warhawk » Tue Oct 02, 2018 11:50 am

Hi Snn 47 .
I would suggest use a TV signal splitter , you can get them at Walmart , Lows , Home Depot Best Buy . Anyway the signal splitters are also Combiners as you have found out . Their is a drop of signal of about 8DB . You can put a LNA that everybody is selling in front of the Combiner/ splitter or in your case the output .

snn47
Posts: 147
Joined: Tue Dec 27, 2016 11:00 pm

Re: Antenna combiner

Post by snn47 » Wed Oct 03, 2018 4:41 am

@P-40 Warhawk illllmhad asked about combining his antennas and if the referenced combiner would work for him.

Any passive device can be used as spltter combiner, but the problem is that cutoff frequencies have to match the antenna frequency range. In this case, since designed for BC/TV for most parts of the spectrum not the antenna with the best performance will be available for recption and the disadvantage of high insertion loss.
While you can add preamps to overcome the loss in the combiner, this will cause unnessary intermodulation and overload to the receiver. To many many strong stations degrade receiver performance, unless of course you live far far away from any such stations, e.g. an arctic region.
Therefore you would have to add bandpass filter or preselectors to compensate IM, but you would have an unessary complex and expesive system without any benfit compared to a simple mechanical switch, except for not having to manually switch when you change frequency ranges.

P-40 Warhawk
Posts: 84
Joined: Thu Jun 26, 2014 11:55 pm

Re: Antenna combiner

Post by P-40 Warhawk » Wed Oct 03, 2018 11:49 pm

Hi Snn47 .
I just read your last post and all that I can say is oh! Well I guess than go to plan B . use a RF switch , a lot of inputs and one output . MFJ sells them . .mfjenterprises.com

illllm
Posts: 22
Joined: Tue Apr 17, 2018 5:41 pm

Re: Antenna combiner

Post by illllm » Sat Oct 06, 2018 2:09 pm

I cam across this:

https://www.dxengineering.com/parts/dxe-rsc-2

I wonder if there is a circuit since this item is about $80.

JEL
Posts: 123
Joined: Wed Feb 07, 2018 2:08 am

Re: Antenna combiner

Post by JEL » Mon Oct 15, 2018 3:35 pm

illllm wrote:
Sat Oct 06, 2018 2:09 pm
I cam across this:

https://www.dxengineering.com/parts/dxe-rsc-2

I wonder if there is a circuit since this item is about $80.
I read it as being useful only if used with an antenna-system which is in phase, such as this setup (2 wires, same length, same position, same everything basically): Image

Read more about that setup here: https://remoteqth.com/two-wire-beverage.php

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