What is the point of a combiner splitter?

[SIMON11]

No matter how many posts I read on a subject I have to try it to see what happens. I have a discone and a 2m 70cm antenna and I change them over to see what difference there is in signal. I tried joining them with a bnc tee piece before entering the scanner and I lost a lot of signal. I had read about combiner splitters the pros and cons but thought I would try one. I know they use them to join two television aerials to get a stronger signal.
I bought a wideband combiner splitter for joining any two antenna. On connecting any one antenna the signal is as it is without the combiner, As soon as I connect them both the signal is lost the same as if I use a bnc tee.
What is the point? Do you have to use a mast amp with a combiner splitter? Or are they just a waste of time as many forum users state? I will probably now waste my money on a mast amp just to see what it does. If anything. At least I will have first hand experience of trying it.
This can be an expensive hobby can't it!




Thanks in advance for any comments.

 

[MacombMonitor]

No matter how many posts I read on a subject I have to try it to see what happens. I have a discone and a 2m 70cm antenna and I change them over to see what difference there is in signal. I tried joining them with a bnc tee piece before entering the scanner and I lost a lot of signal. I had read about combiner splitters the pros and cons but thought I would try one. I know they use them to join two television aerials to get a stronger signal.
I bought a wideband combiner splitter for joining any two antenna. On connecting any one antenna the signal is as it is without the combiner, As soon as I connect them both the signal is lost the same as if I use a bnc tee.
What is the point? Do you have to use a mast amp with a combiner splitter? Or are they just a waste of time as many forum users state? I will probably now waste my money on a mast amp just to see what it does. If anything. At least I will have first hand experience of trying it.
This can be an expensive hobby can't it!

Thanks in advance for any comments.

Any of these devices, regardless of who makes them, or how much they cost, or what they call them, are not going to work as well as a single antenna with it's own dedicated coax, and limited number of connectors. They do make active, or amplified multi-couplers, vs passive (non-amplified) multi-couplers, the the amplifier often introduces a whole new set of problems, such as noise, or overload. If you must use an amplifier, try to find a mast-mounted amplifier, as opposed to having the amplifier in your listening shack, near the scanner. A mast-mounted amplifier will gather the signal at the base of the antenna, without amplifying noise, and interference gathered along the coax, and "push" that signal down the coax to your radio. An amplifier in the shack "pulls" the signal down the coax, along with all the noise, and interference the coax picks up along the way. Also make sure the amplifier has an adjustable gain, preferably allowing you to turn the gain down to zero when necessary. Make sure all the devices you use in your antenna system are rated for the highest frequency you intend to receive. Pay close attention to the losses introduced by each, and every device on your antenna system. Often it's like three steps forward, two back.

I still think the best overall solution is to dedicate one scanner to the 850MHz band, with it's own antenna optimized for that band. Then have a second scanner (if not more), for VHF (150MHz), and UHF (450MHz) monitoring, with either a wide-band discone, or dual-band antenna. Keep it simple!

 

[Skypilot007]

The BNC T connector will never work out well as you have seen. I think a simple antenna selector switch would solve your problems. You would just need to turn a switch to change from one antenna to another. Then you can watch the s-meter and switch between antenna to see which one works best for what.

 

[Al42]

Simon, if the signal coming in on one antenna is out of phase with the same signal on the other antenna, they tend to cancel each other. That's why people use diplexers instead of splitters.

And, yes, the hobby can get quite expensive if you want to do more than turn the scanner on and listen to it.

 

[kb2vxa]

Hi Simon and all,

"I know they use them to join two television aerials to get a stronger signal."
There's a lot more to a stacking kit than a combiner, in fact one isn't used at all. Actually you're thinking of a phasing harness, for transmitting they're sometimes called power dividers. You must be a ham with that question about mounting a 2M/70cM antenna, you should know better. Something tells me you need a bit of study to upgrade your Foundation license.

I'm not being sarcastic, seriously you need a bit more technical know-how you can't get here, this being a very non technical, casual user group. You can start by reading my latest post in the general discussion forum where I wrote the conclusion of Diplexer Trek The Final Frontier, then crack the study manuals.

Thanks Al, you must have been reading my epic story of the infinite universe, now read the final chapter. I'll paraphrase it here, that custom made diplexer works like a charm.

 

[SIMON11]

Hi Simon and all,

"I know they use them to join two television aerials to get a stronger signal."
There's a lot more to a stacking kit than a combiner, in fact one isn't used at all. Actually you're thinking of a phasing harness, for transmitting they're sometimes called power dividers. You must be a ham with that question about mounting a 2M/70cM antenna, you should know better. Something tells me you need a bit of study to upgrade your Foundation license.

I'm not being sarcastic, seriously you need a bit more technical know-how you can't get here, this being a very non technical, casual user group. You can start by reading my latest post in the general discussion forum where I wrote the conclusion of Diplexer Trek The Final Frontier, then crack the study manuals.

Thanks Al, you must have been reading my epic story of the infinite universe, now read the final chapter. I'll paraphrase it here, that custom made diplexer works like a charm.

Thanks for your reply. I am not a ham and I do not transmit. The bit about the 2m 70cm antenna is because I have been advised on several occasions that this should outperform my discone on these bands. I bought one and I find it doesn't. Rather than just have wasted my money, I am trying to combine the two to get a better signal. This may be impossible and cost me more money but it is interesting and a good way of learning. There is nothing like first hand experience.
Thanks to AL42 I can now see that it may be hard if not impossible as the signals are probably out of phase. But then there may be something to bring them back in phase.
I have my antenna in the loft and I am just trying to squeeze another couple of dbi out of them rather than mounting outside as this has it's complications.
I know that a mast amp needs a good signal and that it is only designed to overcome the loss of the down lead but I will try it anyway. I remember a neighbour living next door to me and they had two television aerials mounted together with a mast amp and the picture was far better than mine with one. I have also read on this forum that joining two antenna of the same design can give 3dbi of gain which I tend to believe.
As far as saying that I can't pick up technical knowledge from this forum. I find there are a lot of knowledgable users on this forum And I am very grateful for their input. I dont need to know all the theorum behind the design of antenna to experiment. I may however read some basic theory just out of interest.