Splitting An Antenna

[KI5IRE]

Hello everyone, I'm trying to figure out the lowest cost, most effective way to split off my antenna feed.

I have an attic discone that is currently only feeding my BCD436 but I am trying to figure out how I could split the antenna to a future 2nd BCD436, my BCD996xt, a future BCT15x and a future BCD996p2/BCD536 or SDS100.

I posted a while back asking about this and some had mentioned using a multi-coupler for lowest RF loss, but I have yet to find a decent looking multi-coupler that is fairly inexpensive or that I can drive myself to purchasing.

I understand that a multi-coupler will grant me lowest RF loss out of my antenna, but if I'm going to cheap out on it, I at least understand it will come with issues.

I am looking for the best way to be as cheap as possible, while getting the best results on a budget.

What have y'all tried?

 

[buddrousa]

Then get you a 8 port TV amp a bunch of F connector to bnc and pray you do not have noise.

 

[Ubbe]

I understand that a multi-coupler will grant me lowest RF loss out of my antenna, but if I'm going to cheap out on it, I at least understand it will come with issues.

No, it only amplifies what signals are left after the coax have done its attenuation.

There are no doubts that the most effecient configuration are a low noise, high IM resistant amplifier at the antenna and then a passive splitter at the scanners. Depending of scanners and number of ports and the antenna gain, it often is neccessary to attenuate the signal to a level where the scanners operate at their optimum. Having the amplifier makes it possible to use cheap coax, as long as it is well shielded. RG6 are the most cost effective coax you can get.

$30 Amplifier with excellent performance, way better than a Stridsberg multicoupler, https://www.ebay.com/itm/Ultra-Line...A-103-Bias-Tee-ESD-Stabilization/282883786525
$3 Splitter. See to that at least one port have power pass to feed power to the amplifier, https://www.ebay.co.uk/itm/4-WAY-F-...EVIEW-BLADE-VU-TECHNOMATE-D-BOX-/350879872817
$20 Coax https://www.ebay.com/itm/RG6-COAX-C...adio-rg6-COAXIAL-Tri-Shield-WIRE/151388951973
$20 Variable 20dB attenuator https://www.amazon.com/Konig-Satellite-Attenuator-45-2300MHz-SAT-ATT20-KN/dp/B002KD7OPE
$4 75 ohm terminator https://www.ebay.com/itm/1-500-PCS-...minator-End-Cap-Cover-USA-Seller/232775160451
Pigtail coax https://www.ebay.com/itm/F-type-Mal...16-Coax-Low-Loss-Jumper-RF-Cable/392006640812
https://www.ebay.com/itm/F-J-Male-t...tail-20cm-High-Quality-Quick-USA/232299077450

You'll need some additional adapters to the amplifier and scanners and perhaps the antenna and some jumper cables from splitter to scanners, eiter ready made pigtails or use a F-SMA or F-BNC adapters. You can select splitters with the number of ports that you think you will need in the future and get some 75 teminators for the ports you do not use and you can choose any RG6 coax that suits your need, either with connectors fitted or you buy the type of connector you screw on without any expensive crimp tool, but buy them from the same place as the coax as there are 4 different sizes. If you re-use your current coax you can do that and only add the adapters needed.
It will be way cheaper than a Stridsberg solution that will not give the same superior performance.

/Ubbe

 

[mule1075]

No, it only amplifies what signals are left after the coax have done its attenuation.

There are no doubts that the most effecient configuration are a low noise, high IM resistant amplifier at the antenna and then a passive splitter at the scanners. Depending of scanners and number of ports and the antenna gain, it often is neccessary to attenuate the signal to a level where the scanners operate at their optimum. Having the amplifier makes it possible to use cheap coax, as long as it is well shielded. RG6 are the most cost effective coax you can get.

$30 Amplifier with excellent performance, way better than a Stridsberg multicoupler, https://www.ebay.com/itm/Ultra-Line...A-103-Bias-Tee-ESD-Stabilization/282883786525
$3 Splitter. See to that at least one port have power pass to feed power to the amplifier, https://www.ebay.co.uk/itm/4-WAY-F-...EVIEW-BLADE-VU-TECHNOMATE-D-BOX-/350879872817
$20 Coax https://www.ebay.com/itm/RG6-COAX-C...adio-rg6-COAXIAL-Tri-Shield-WIRE/151388951973
$20 Variable 20dB attenuator https://www.amazon.com/Konig-Satellite-Attenuator-45-2300MHz-SAT-ATT20-KN/dp/B002KD7OPE
$4 75 ohm terminator https://www.ebay.com/itm/1-500-PCS-...minator-End-Cap-Cover-USA-Seller/232775160451
Pigtail coax https://www.ebay.com/itm/F-type-Mal...16-Coax-Low-Loss-Jumper-RF-Cable/392006640812
https://www.ebay.com/itm/F-J-Male-t...tail-20cm-High-Quality-Quick-USA/232299077450

You'll need some additional adapters to the amplifier and scanners and perhaps the antenna and some jumper cables from splitter to scanners, eiter ready made pigtails or use a F-SMA or F-BNC adapters. You can select splitters with the number of ports that you think you will need in the future and get some 75 teminators for the ports you do not use and you can choose any RG6 coax that suits your need, either with connectors fitted or you buy the type of connector you screw on without any expensive crimp tool, but buy them from the same place as the coax as there are 4 different sizes. If you re-use your current coax you can do that and only add the adapters needed.
It will be way cheaper than a Stridsberg solution that will not give the same superior performance.

/Ubbe

Can everyone get it thru their heads the stridsberg is not a preamplifier repeat it is not a preamplifier. It is a active multi-coupler. Now back to the topic at hand.

 

[prcguy]

An active Stridsberg multicoupler has a preamplifier no different than one you would use for general purpose wide band antenna amplification. Its got a fairly low noise figure and reasonable compression point with enough gain to overcome divider loss and maybe a dB or two extra.

You can easily duplicate a Stridesberg multicoupler by shopping for an amplifier with similar specs and a suitable divider and if you find the parts used you can probably do it for way less than a new Stridesberg. I would only buy a 50 ohm amplifier and high quality 50 ohm divider which will provide a consistent match across the bands and maximum isolation between receivers.

You can get by with TV components but my way of doing things the right way limits me to 50 ohm components for a 50 ohm antenna system. I'm usually known for doing things the right way and that's probably why people ship me all over the world to do jobs for them.

Can everyone get it thru their heads the stridsberg is not a preamplifier repeat it is not a preamplifier. It is a active multi-coupler. Now back to the topic at hand.

 

[buddrousa]

People that have never used a Stridsberg the know it alls only know the cheap ways and will only learn when they spend the money and buy an Active Stridsberg and compaired first hand I had to learn first hand that the Stridsbergs work and why the homemade version only half works.

 

[lmrtek]

Use RG6 coax and buy a 4 port channel master 3412 distribution amplifier for $30 bucks.
......

 

[mule1075]

An active Stridsberg multicoupler has a preamplifier no different than one you would use for general purpose wide band antenna amplification. Its got a fairly low noise figure and reasonable compression point with enough gain to overcome divider loss and maybe a dB or two extra.

You can easily duplicate a Stridesberg multicoupler by shopping for an amplifier with similar specs and a suitable divider and if you find the parts used you can probably do it for way less than a new Stridesberg. I would only buy a 50 ohm amplifier and high quality 50 ohm divider which will provide a consistent match across the bands and maximum isolation between receivers.

You can get by with TV components but my way of doing things the right way limits me to 50 ohm components for a 50 ohm antenna system. I'm usually known for doing things the right way and that's probably why people ship me all over the world to do jobs for them.

OK thanks but if I am reading it right it only has 4db of gain and a 3.5 db noise figure. So it does not have the 20db gain the lna preamplifiers people are linking in most of these threads is that correct?

 

[zz0468]

There's an engineering saying that says "You can get something done right, get it done cheap, and you can get it done fast. Pick two."

In the case of multicouplers and antennas, it's pretty much the same, only you can take the time constraint out. So, it becomes a choice of "best" or cheap, and usually the two are mutually exclusive.

Prcguy is pretty damned sharp, and I do what he's suggesting... I've built many multicouplers, and have been happy with the results. But then, I have the sweep gear and spectrum analyzers and noise figure meters to do it. The typical hobbiest does not.

It then gets down to some variation of best vs. cheapest, and typically those advocating one over the other have no way of telling what's really going on. If they did, they'd probably go ahead and build their own, too.

So, what's the OPs skill level? What's the OPs ability to test? If it's minimal to nonexistent, then you just throw money at it. If you just use a TV distribution amp, you might seriously compromise your reception, but they're cheap. If you buy a Stridesberg, it's a reputable product that people seem to like. But as prcguy alluded to, it's not "the best".

 

[zz0468]

In measuring receiver performance, lots of gain in front of an already sensitive receiver is not a good thing. It's all about noise figure, just enough gain to overcome the receiver noise figure, and immunity to overload.

Those 20 dB gain preamps have a lot of loss behind them in the form of splitters and attenuators before it plugs into a receiver.

OK thanks but if I am reading it right it only has 4db of gain and a 3.5 db noise figure. So it does not have the 20db gain the lna preamplifiers people are linking in most of these threads is that correct?

 

[prcguy]

The preamp in a multicoupler is before the divider(s) to make up for loss. A 4-way divider will have about 6-7dB loss and an 8-way will have 9-10dB loss. If a 4-way multicoupler has about 4dB of gain overall the internal preamp would be in the 10-11dB gain range. That same preamp would be a better choice for an 8-way multicoupler leaving you with about -1 to +1dB of overall gain.

Generally speaking, it would be nuts to use a 20dB or higher gain antenna preamp in a wideband system, it would be too much gain and cause more problems than it fixes. In a narrow band system like a very well filtered 466 to 469MHz front end for repeater systems, you do see preamps in the 15 to 20dB range, but those are usually well engineered systems with known outcomes. 10dB gain would be my goal for placing a wide band preamp right at an antenna to make up for cable loss or to feed a divider when making a multicoupler. But that's just me, the guy who likes to do it right. You can do what you want.

OK thanks but if I am reading it right it only has 4db of gain and a 3.5 db noise figure. So it does not have the 20db gain the lna preamplifiers people are linking in most of these threads is that correct?

 

[mule1075]

The preamp in a multicoupler is before the divider(s) to make up for loss. A 4-way divider will have about 6-7dB loss and an 8-way will have 9-10dB loss. If a 4-way multicoupler has about 4dB of gain overall the internal preamp would be in the 10-11dB gain range. That same preamp would be a better choice for an 8-way multicoupler leaving you with about -1 to +1dB of overall gain.

Generally speaking, it would be nuts to use a 20dB or higher gain antenna preamp in a wideband system, it would be too much gain and cause more problems than it fixes. In a narrow band system like a very well filtered 466 to 469MHz front end for repeater systems, you do see preamps in the 15 to 20dB range, but those are usually well engineered systems with known outcomes. 10dB gain would be my goal for placing a wide band preamp right at an antenna to make up for cable loss or to feed a divider when making a multicoupler. But that's just me, the guy who likes to do it right. You can do what you want.

Thanks for the breakdown just what I needed. I will be playing around with some ideas in the future. Thanks again for You're insight greatly appreciated.

 

[prcguy]

Your welcome. If your going to roll your own multicoupler you can estimate the gain of what's in a Stridesberg and their noise figure and IP1 or IP3 should be advertised. I would shop for a similar gain amp with no worse noise figure and better IP1 (1dB compression point) or IP3 rating.

Besides the frequency range and number of ports on a divider, there is the isolation between ports. A good divider will have at least 25dB isolation between ports. TV type dividers do not rate very well on this spec.

Thanks for the breakdown just what I needed. I will be playing around with some ideas in the future. Thanks again for You're insight greatly appreciated.

 

[Ubbe]

If you are looking for the most cost effective way to split a signal, that the OP requested, you would not get an expensive Stridsberg multicoupler.

They are used for splitting already good signals, as with all multicouplers. They are plug&play with BNC connectors and are trouble free even for the novice to use so they are popular but comes with a high cost. Sat/tv splitters have 12 to 20dB isolation between ports measured on different cheap 1-2 splitters I use. Having more ports would logically give even more dB so no different than a Stridsberg.

Forget about things like constant match when dealing with scanners and wideband antennas, their impedances are all over the place.

Stridsberg are probably building their products by hand and in house which have a high labour cost and they maybe sell 50-100 multicouplers a year. Compare to sat/tv gear that are made in china and sell 10 thousands a year and are exposed to fierce competition.

If the OP only wants to split his current received signal he just need that suggested amplifier that can be powered with an USB cable, the variable attenuator to be put between amp and splitter and a suitable CATV splitter. Easy and quick to set up. Moving the amp up to the antenna will in most cases give an increased receive range.

Stridsberg IP1 17dB IP3 31dB Noise 3,5dB
PGA103+ IP1 20dB IP3 40dB Noise 0,5dB

/Ubbe

 

[rwier]

I ignored "conventional wisdom" and purchased a

https://is.gd/Y4vzEI

I was so happy with it, I purchased two more. I have one in the bedroom, one near my computer hutch, and one in my vehicle. The one in the vehicle was very expensive, as it required the installation of a 12v dc to a 120v ac converter.

 

[prcguy]

Why? That model should run fine off 12V vehicle power instead of 15V.

The one in the vehicle was very expensive, as it required the installation of a 12v dc to a 120v ac converter.

 

[rwier]

Why? That model should run fine off 12V vehicle power instead of 15V.

I misspoke. The vehicle installed items I was referring to as converters were inverters. The two models I had professionally installed are

Wagan TrueRated(TM) 400 Watt 5V 2.1 Amp Continuous Power Inverter with USB Charging Ports - EL2003-5

and

Cobra CPI 880 800 Watt 12 Volt DC to 120 Volt AC Power Inverter with 5 Volt USB output

At the time, at remote locations (dark sites), I was using two computers, two GPS units, a reasonably sophisticated "GOTO" telescope, and a myriad of devices that assist with human comfort. Also, these locations often had multiple nearby camping parties. Some had diesel generators, and they allowed others that were nearby to use the same. I allowed nearby campers to avail themselves of the inverters when needed. My PU truck spent a lot of time idling, lol.

As to the "splitter", the supplied wall wart and the associated (very) proprietary cables are designed for 120v plug in use.

I did have additional 12v accessory outlets installed at the same time, as many small draw electrical devices were in use by myself, and members of my group.

 

[prcguy]

What I was referring to is you can get a mating coaxial power plug with cable attached that fits the amplified splitter and run that direct from your vehicle 12V without an AC to DC converter.

I misspoke. The vehicle installed items I was referring to as converters were inverters. The two models I had professionally installed are

Wagan TrueRated(TM) 400 Watt 5V 2.1 Amp Continuous Power Inverter with USB Charging Ports - EL2003-5

and

Cobra CPI 880 800 Watt 12 Volt DC to 120 Volt AC Power Inverter with 5 Volt USB output

At the time, at remote locations (dark sites), I was using two computers, two GPS units, a reasonably sophisticated "GOTO" telescope, and a myriad of devices that assist with human comfort. Also, these locations often had multiple nearby camping parties. Some had diesel generators, and they allowed others that were nearby to use the same. I allowed nearby campers to avail themselves of the inverters when needed. My PU truck spent a lot of time idling, lol.

As to the "splitter", the supplied wall wart and the associated (very) proprietary cables are designed for 120v plug in use.

I did have additional 12v accessory outlets installed at the same time, as many small draw electrical devices were in use by myself, and members of my group.