OneBadUukha
Member
I have several very basic telescoping antennas for scanner radios. Would there be any advantage to somehow combining them in series to create a more powerful "single" antenna?
Is Combining Antennas Useful/Possible?
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There's a sticky thread on this very topic.
https://forums.radioreference.com/s...57-running-one-scanner-multiple-antennas.html
It's an idea full of pitfalls and gotchas and it's generally not worth it. You'd be better served just using a better antenna. To sum up that very lively thread, to do that requires some engineering. Otherwise, the antenna is just a random collection of metal, and it will give you a random collection of results.
No. It's complicated to explain, and will usually result in less performance. What are you trying to accomplish? Improvement on one band, or every thing?
OneBadUukha
Member
I'd like to get better performance from a range of frequencies. I wanted to rule out a DIY approach before I spent money on better antenna.
What are the requirements? What frequency ranges? What are you trying to listen to? If you're unhappy with the stock antenna, what specific problems are you trying to solve?
If you're going from internal whip antennas to just about anything external (as in outside), then you'll see a huge improvement.
OneBadUukha
Member
I listen mostly to 40-50 MHz and 400-550 MHz. Police, Fire, Highway Patrol, etc.
Ok. There's a couple of possibilities, and people will chime in with ideas. There are multiband scanner antennas that cover those ranges in a single antenna. The frequency separation also lends itself to easily being diplexed, so you could combine two antennas to a single coax, then split that out to multiple radios.
Where it gets hairy is when you want to combine multiple antennas on the same frequency, or the separation is such that diplexing is impractical.
Google 'low band uhf diplexer' and see what shakes out.
Ubbe
Member
Look at the DPD Omni-x antenna. It has two dipoles in a cross connected in parallell to a dipole made of tubes.
It is three antennas tuned to three different frequencies connected together. If you look at the measurements of the antenna you'll see that there's no magic involved as the lenght of the dipoles corresponds to the middle of the frequency band they are supposed to cover. And users says that the antenna works great. The same is true for the popular ST-2 antenna that many says are the best antenna ever for scanner use.
Make one telescope match 45MHz (160cm) and the other 470MHz (16cm) and connect them together as a V. The easiest way to test are If you have a long steady transmission to monitor and quickly change the lenght of the telscope and notice if the reception signal changed.
Of course setting any kind of antenna on the roof will outperform anything you can do inside with telescope antennas.
/Ubbe
It is three antennas tuned to three different frequencies connected together. If you look at the measurements of the antenna you'll see that there's no magic involved as the lenght of the dipoles corresponds to the middle of the frequency band they are supposed to cover. And users says that the antenna works great. The same is true for the popular ST-2 antenna that many says are the best antenna ever for scanner use.
Make one telescope match 45MHz (160cm) and the other 470MHz (16cm) and connect them together as a V. The easiest way to test are If you have a long steady transmission to monitor and quickly change the lenght of the telscope and notice if the reception signal changed.
Of course setting any kind of antenna on the roof will outperform anything you can do inside with telescope antennas.
/Ubbe
What's down there?
ecps92
Member
Businesses, Public Safety, Military, Utilities
So I added a 15 element 900MHZ Hamfest beam below my 1/4 wave VhfUhf and the results are fantastic. I just got a good T and combined them without measuring anything. Bringing in MPSCS towers 50 miles away. VHF still there.
By combing them with a T adapter you are reducing the performance of both antennas. If you can find a Comet CF-413 diplexer, it will separate the VHF/UHF antenna from the 900 antenna and allow them to do the best job with minimal loss.
The CF-413 passes 1.3 to about 470Mhz on one input and 840 to over 1300MHz on the other. I use them all the time for combining an 800MHz or higher antenna with Discones, etc.
prcguy
The CF-413 passes 1.3 to about 470Mhz on one input and 840 to over 1300MHz on the other. I use them all the time for combining an 800MHz or higher antenna with Discones, etc.
prcguy
Ubbe
Member
That's whats it all about. As long as it works for you there's no need overdoing it.
/Ubbe
JamesO
Member
While the overall result may seem "fantastic", as mentioned, as long as you are happy with the result, this is all the matters. But there may be some hidden performance problems that you have not noticed yet.
Like anything, there is a lot of experimentation that goes on and sometimes it works, sometimes not so much. Without a lot of bench marking of transmitter sites, it is hard to say 100%. While the S meter on the radio might be a useful relative reference point, sometimes cheap SDR is helpful to get a better overall picture of what is going on.
I just recently moved from a smaller all band antenna the attic to my Antennacraft ST2 that is in the attic and clearly the Low Band State Police from the adjacent county is FAR better.This feed is running my Mini-Circuits LNA and I still am getting very good results. I need to do some more comparison, but I had been using the other smaller antenna for a long time, so I have good reference points to compare against.
I have a plan to set up an antenna mix using a diplexer to see how things perform next.
Hopefully then I can get all of this moved outside in the near future.
Like anything, there is a lot of experimentation that goes on and sometimes it works, sometimes not so much. Without a lot of bench marking of transmitter sites, it is hard to say 100%. While the S meter on the radio might be a useful relative reference point, sometimes cheap SDR is helpful to get a better overall picture of what is going on.
I just recently moved from a smaller all band antenna the attic to my Antennacraft ST2 that is in the attic and clearly the Low Band State Police from the adjacent county is FAR better.This feed is running my Mini-Circuits LNA and I still am getting very good results. I need to do some more comparison, but I had been using the other smaller antenna for a long time, so I have good reference points to compare against.
I have a plan to set up an antenna mix using a diplexer to see how things perform next.
Hopefully then I can get all of this moved outside in the near future.
Thanks. That looks interesting. Due to the current fittings and the fact that one tower si 700MHZ I'll jsut see how this does. My point was I just threw this up before it rained and made great improvements. Seems like there's a lot of drama from some people when anyone mentions dual antennas.
JamesO
Member
Dual antennnas with a splitter or T fitting can be and are typically very unpredictable. While this may appear to work for you now, you may find some funny things as you spend more time with it. It is often hard to "see" unless you have some sophisticated testing equipment to know exactly what is going on.
Something like this is commercially available - DPD Productions - Base & Mobile Antennas for Radio Scanners: VHF, UHF, NOAA, Low-Band, 700 MHz, Police, Fire, Public Safety
Forget about the drama, members often try to warn the less experienced, antennnas are funny things at the end of the day. But as long as you are happy with the results it really does not matter what anyone has to say because they are not connected to the end of the feedline!
Glad it appears to have worked out for you.
Can you recommend one with F fittings for VHFUHF and 800 beam?
JamesO
Member
Why bother if you are happy with the current result. While I may not have done what you did due to my background and knowledge, sometimes things work out despite what is expected to happen. Or you have an improvement and are happy with it even though the set up is not optimized or ideal, you have a partial solution.
The only items with F connectors would be from the CATV/MATV world and may or may not be what you want and need. There are VHF/UHF diplexers and other devices, but these may relegate the Yagi to the only UHF/700-800 MHz antenna which may impact other UHF/700-800 MHz you want to monitor. Even using a 2 way splitter as a combiner may or may not help matters.
If you are really looking for a "solution" you may not find a device with native F connectors and 75 Ohm interfaces. You may need to use F adapters.
Antennas are Co-phased all the time with basically a "T" connection, they tend to use a different impedance coax that is equal length and identical antennas. Again, this is doing things more the "right" way that is predictable and tested, what you have appears to work, so not sure I would get too excited to see a major change or improvement. Often playing with a set up may actually make things worse.
The only items with F connectors would be from the CATV/MATV world and may or may not be what you want and need. There are VHF/UHF diplexers and other devices, but these may relegate the Yagi to the only UHF/700-800 MHz antenna which may impact other UHF/700-800 MHz you want to monitor. Even using a 2 way splitter as a combiner may or may not help matters.
If you are really looking for a "solution" you may not find a device with native F connectors and 75 Ohm interfaces. You may need to use F adapters.
Antennas are Co-phased all the time with basically a "T" connection, they tend to use a different impedance coax that is equal length and identical antennas. Again, this is doing things more the "right" way that is predictable and tested, what you have appears to work, so not sure I would get too excited to see a major change or improvement. Often playing with a set up may actually make things worse.
Ubbe
Member
The simplest solution are often the best and others that costs money and time might not give a noticable improvement. It is mentioned that half the power from one antenna goes out the other and does not reach the scanner. But if you get a proper splitter it will attenuate half the power anyways with the end result being the same.
Experiment but don't put too much money and time into it if you already have achived what you initially wanted to do.
/Ubbe
Experiment but don't put too much money and time into it if you already have achived what you initially wanted to do.
/Ubbe
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