Mini-Circuits ZFL-1000LN 15v Amplifier & ZFSC-4-1 4 Way Splitter question

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Pyr8

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I just ordered a Mini-Circuits "ZFSC-4-1" 4 Way Splitter/Combiner and a Mini-Circuits "ZFL-1000LN" 15v Amplifier.

The "ZFL-1000LN" has a dB gain depending on voltage as follows:

12V = 19.9dB
15V = 23.50dB
16V = 24.14dB

Can I connect a variable power supply to control the output voltage, in return controlling the dB gain on the fly?
I'm wondering if changing the input voltage on the amplifier while my scanners are connected will cause damage to anything?

This will be used for monitoring only and no TX.

Both units are wide-band from 1Mhz to 1Ghz & .1Mhz to 1Ghz respectively.

The units can be found here:

ZFL-1000LN power amp = Mini-Circuits ZFL-1000LN | eBay
ZFSC-4 way splitter = ZFSC-4-1 4 Way Splitter | eBay
 

prcguy

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If your going to use this as an antenna preamp or otherwise feed it with an antenna I would cancel the order and get another amp. I have drawers full of ZFL1000, ZFL2000, ZFL500, etc and would never use one in a receive circuit unless it was for a very specific band and I had a good preselector in front of the amp. Otherwise the IP1 is too low and it will overload easily and create all kinds of problems. I've tried all these amps in the past with miserable results.

If you lower the voltage the gain will drop but usually the IP1 also drops making the amp even more susceptible to overload. Not knowing what your antenna will pick up and what kind of spectrum and levels will be presented to the amp its hard to choose an appropriate one but I would look for an IP1 of at least 20dBm or more or an IP3 of 35dBm or more with a little less gain, maybe 15dB max and a noise figure no worse than the ZFL1000. In your case you want to make up for the splitter loss and maybe spiffy up the levels a little but you have to be very careful with the gain and other parameters.
prcguy



I just ordered a Mini-Circuits "ZFSC-4-1" 4 Way Splitter/Combiner and a Mini-Circuits "ZFL-1000LN" 15v Amplifier.

The "ZFL-1000LN" has a dB gain depending on voltage as follows:

12V = 19.9dB
15V = 23.50dB
16V = 24.14dB

Can I connect a variable power supply to control the output voltage, in return controlling the dB gain on the fly?
I'm wondering if changing the input voltage on the amplifier while my scanners are connected will cause damage to anything?

This will be used for monitoring only and no TX.

Both units are wide-band from 1Mhz to 1Ghz & .1Mhz to 1Ghz respectively.

The units can be found here:

ZFL-1000LN power amp = Mini-Circuits ZFL-1000LN | eBay
ZFSC-4 way splitter = ZFSC-4-1 4 Way Splitter | eBay
 

prcguy

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I'm not familiar with that preamp but it seems to be for portable use with rubber ducks or short whips attached. It may go in the toilet when you attach a base antenna. A good preamp that will survive the onslaught of signals and levels from an antenna is usually going to draw too much current to be considered portable and able to run from a 9v battery. If rum from 12 or 15v I would expect it to need at least 100ma of current or if 24v, 50ma.

I've only found a couple of broad band preamps that are suitable to use with a Discone and they are fairly elaborate and expensive mil surplus units. I live in a high level RF area and until you know what your area is like try not to go cheap on a preamp.

If you have a friend with a spectrum analyzer, or even an RF power meter or RF milivolt meter can give you a lot of info. Around here an RF power meter can show an average of -10dBm level from a Radio Shack Discone and that's the aggregate level for all carriers being picked up at any given time from cell towers, paging, TV, FM broadcast, etc. If someone is transmitting in my neighborhood that level can go way up. Hook that -10dBm spectrum of signals to a ZFL1000 with 20dB gain and now your at +10dBm and 7dB past the compression point of the preamp and you have a mess.

You can create lots of Intermod that will wreak your noise floor with signals that are 20 or 30dB below the 1dB compression point so the ZFL1000 could have trouble with signals that are 20dB or 100X weaker than I measure at my location. If you want to avoid problems you have to go very big on the preamp or filter out most of the spectrum and leave small segments at a time to feed through your preamp.
prcguy


Any idea if I can use the "Jim M75" Pre-Amplifier on the antenna side (before the splitter) with any success?
 

Pyr8

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I live in a rural area without much noise if any.

IP1?

What would you suggest in terms of a booster that wont be a hassle to source out?
I really only want the booster to cancel the losses in my 100 foot cable run as well as associated connectors, and of course the 4 way splitter.

I figure something in the +10dB would be more than enough.

I'm not familiar with that preamp but it seems to be for portable use with rubber ducks or short whips attached. It may go in the toilet when you attach a base antenna. A good preamp that will survive the onslaught of signals and levels from an antenna is usually going to draw too much current to be considered portable and able to run from a 9v battery. If rum from 12 or 15v I would expect it to need at least 100ma of current or if 24v, 50ma.

I've only found a couple of broad band preamps that are suitable to use with a Discone and they are fairly elaborate and expensive mil surplus units. I live in a high level RF area and until you know what your area is like try not to go cheap on a preamp.

If you have a friend with a spectrum analyzer, or even an RF power meter or RF milivolt meter can give you a lot of info. Around here an RF power meter can show an average of -10dBm level from a Radio Shack Discone and that's the aggregate level for all carriers being picked up at any given time from cell towers, paging, TV, FM broadcast, etc. If someone is transmitting in my neighborhood that level can go way up. Hook that -10dBm spectrum of signals to a ZFL1000 with 20dB gain and now your at +10dBm and 7dB past the compression point of the preamp and you have a mess.

You can create lots of Intermod that will wreak your noise floor with signals that are 20 or 30dB below the 1dB compression point so the ZFL1000 could have trouble with signals that are 20dB or 100X weaker than I measure at my location. If you want to avoid problems you have to go very big on the preamp or filter out most of the spectrum and leave small segments at a time to feed through your preamp.
prcguy
 

majoco

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Ideally you need a 'multicoupler' - a properly designed amplifier with all the right parameters - low noise, high overload, good linearity etc immediately followed by individual matched buffers for each individual output.

As previously noted, watch out for mil surplus on FleaBay. Good ones have inbuilt power supplies as they take a bit of current to keep the front end linear. I just bought a Reaction Instruments VLF-HF Active Multicoupler. Model 409-2 for NZ$50 which has yet to arrive - 1 antenna input - 8 50ohm outputs. Hope it works!
 

rbm

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I agree with prcguy. The IP3 spec is pretty poor for that amplifier.
Higher is better.
I prefer mid 20’s and higher.

I wouldn’t discourage experimentation. Sometimes it works, sometimes it doesn’t.

You could try varying the voltage to the preamp within the min/max specification.
Keep in mind though, that will change more than just the gain.
You may, or may not be happy with the results.
Either way, you’ll learn something from it.

The preamps I use most are LNA-1000 from RF Bay, Inc.

LNA-1000 specifications:

Frequency Range: 10-1000MHz;
Noise Figure: 2dB at 500MHz
Gain: 30dB at 1GHz
P1: 11dBm
IP3: +23dBm
DC Voltage: +9 to 15V
SMA Female Connector

For antennas that aren’t used above 600 MHz or so, I use LNA-580 preamps. Also from RF Bay, Inc.

LNA-580 Specifications:

Frequency Range: 10-580MHz;
Noise Figure: 0.7dB at 250MHz
Gain: 23dB at 250MHz
P1: +19dBm
IP3: +33dBm
DC Voltage: +5V/70mA
SMA Female Connector

That’s a great preamp (LNA-580), but it’s prone to ESD damage and I frequently have to replace the E-PHEMT chips.
They're about the size of a grain of ground pepper with four leads, so if you’re not used to ‘micro’ soldering, I wouldn’t recommend it.
(It’s also more expensive)

I prefer a preamp that has around 10 dB more gain than the total loss of the feed line and splitter.
So …….
If you use a 4-Way splitter with 10 dB loss, and you lose another 7-9 dB in your feed line, 25-30dB is a reasonable amount of gain.

However, if you mount the preamp at the scanner end of the feed line, you will have lost the weakest signals and NO amount of amplification will ever bring them back.

Also, the first stage of your system pretty much ‘sets’ the overall system noise figure.

If you have a preamp with a Noise Figure of 1 dB mounted right at the antenna, your overall system noise figure will ‘approach’ 1 dB.

Mount that very same preamp at the scanner end with 8 dB of coax loss ahead of it, your overall system noise figure will be around 8 dB. (In this case, the coax can be considered to be the first ‘stage’ of the system.)

With all that out of the way ..

'Ball park' losses for splitters: (You can also use them as something of a fixed attenuator in the feed line)

A 2-way splitter has around 4 dB loss
A 3-way splitter has around 7-8 dB loss
A 4-way splitter has around 9-11 dB loss
An 8-way splitter has around 13.5 dB loss

Those numbers vary widely depending on manufacturer so you have to check the specs.

Rich

Here's an old post of mine that shows the weather resistant PVC housings I use for my antenna mounted pre-amps.
http://forums.radioreference.com/scanner-receiver-antennas/115239-pre-amps-local-powering-versus-remote-powering.html#post860180
 
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Pyr8

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Are there any on eBay now that you would suggest under $200?


Ideally you need a 'multicoupler' - a properly designed amplifier with all the right parameters - low noise, high overload, good linearity etc immediately followed by individual matched buffers for each individual output.

As previously noted, watch out for mil surplus on FleaBay. Good ones have inbuilt power supplies as they take a bit of current to keep the front end linear. I just bought a Reaction Instruments VLF-HF Active Multicoupler. Model 409-2 for NZ$50 which has yet to arrive - 1 antenna input - 8 50ohm outputs. Hope it works!
 

prcguy

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The splitter losses mentioned are in line with TV or satellite types but good 50 ohm splitters from companies like MiniCircuits will have something like only .5dB above theoretical loss. That would make them around:

2-way 3.5dB loss
4-way 6.5dB loss
8-way 9.5dB loss

If you spend enough time on Ebay you will find some high level, low noise VHF/UHF amplifiers for very cheap prices. You have to look them all up to find the specs but they are there. Same goes for splitters (power dividers) where I've found some nice Anaren 4-way 50 ohm dividers that cover 10 to 2000MHz with really good specs for $10 each. Or some Mu-Del brand low noise amps that cover 10 to 1000MHz with very high IP1 and IP3 in outdoor enclosures with DC power up the coax options for cheap. These were made for a US three letter agency specifically for VHF/UHF monitoring purposes. This is one of the few amps I've ever bought that really work and do not raise my noise floor or produce IMD that I can measure. Ebay has just about everything you need if you know what to look for.
prcguy

I agree with prcguy. The IP3 spec is pretty poor for that amplifier.
Higher is better.
I prefer mid 20’s and higher.

I wouldn’t discourage experimentation. Sometimes it works, sometimes it doesn’t.

You could try varying the voltage to the preamp within the min/max specification.
Keep in mind though, that will change more than just the gain.
You may, or may not be happy with the results.
Either way, you’ll learn something from it.

The preamps I use most are LNA-1000 from RF Bay, Inc.

LNA-1000 specifications:

Frequency Range: 10-1000MHz;
Noise Figure: 2dB at 500MHz
Gain: 30dB at 1GHz
P1: 11dBm
IP3: +23dBm
DC Voltage: +9 to 15V
SMA Female Connector

For antennas that aren’t used above 600 MHz or so, I use LNA-580 preamps. Also from RF Bay, Inc.

LNA-580 Specifications:

Frequency Range: 10-580MHz;
Noise Figure: 0.7dB at 250MHz
Gain: 23dB at 250MHz
P1: +19dBm
IP3: +33dBm
DC Voltage: +5V/70mA
SMA Female Connector

That’s a great preamp (LNA-580), but it’s prone to ESD damage and I frequently have to replace the E-PHEMT chips.
They're about the size of a grain of ground pepper with four leads, so if you’re not used to ‘micro’ soldering, I wouldn’t recommend it.
(It’s also more expensive)

I prefer a preamp that has around 10 dB more gain that the total loss of the feed line and splitter.
So …….
If you use a 4-Way splitter with 10 dB loss, and you lose another 7-9 dB in your feed line, 25-30dB is a reasonable amount of gain.

However, if you mount the preamp at the scanner end of the feed line, you will have lost the weakest signals and NO amount of amplification will ever bring them back.

Also, the first stage of your system pretty much ‘sets’ the overall system noise figure.

If you have a preamp with a Noise Figure of 1 dB mounted right at the antenna, your overall system noise figure will ‘approach’ 1 dB.

Mount that very same preamp at the scanner end with 8 dB of coax loss ahead of it, your overall system noise figure will be around 8 dB. (In this case, the coax can be considered to be the first ‘stage’ of the system.)

With all that out of the way ..

'Ball park' losses for splitters: (You can also use them as something of a fixed attenuator in the feed line)

A 2-way splitter has around 4 dB loss
A 3-way splitter has around 7-8 dB loss
A 4-way splitter has around 9-11 dB loss
An 8-way splitter has around 13.5 dB loss

Those numbers vary widely depending on manufacturer so you have to check the specs.

Rich

Here's an old post of mine that shows the weather resistant PVC housings I use for my antenna mounted pre-amps.
http://forums.radioreference.com/scanner-receiver-antennas/115239-pre-amps-local-powering-versus-remote-powering.html#post860180
 

Pyr8

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This is the dB loss I figure I will be needing to overcome from the antenna to the input of the scanners.

-2 dB Cable (100' LMR400)
-1 dB Connectors (2 x SMA)
-6.58 dB 4 way splitter
-0.6 dB insertion loss on 4 way splitter

Total = -10.18 dB Loss

+2 dBi (Diamond Discone Antenna)

If it wasn't for the 4 way, I could deal with a -3.5dB loss, but add in the 4 way @ -6.58 dB, and it's too much.
+20/+25 dB on an amp is the most I will need, and may even be a little overkill.

Thoughts guys?!
 

rbm

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If it wasn't for the 4 way, I could deal with a -3.5dB loss, but add in the 4 way @ -6.58 dB, and it's too much.
+20/+25 dB on an amp is the most I will need, and may even be a little overkill.

Thoughts guys?!
Since you're in a rural area, I don't think that much gain is overkill.
The likelihood of overload should be small. (As long as you don't have any strong signals nearby.)

If you find that it's too much, you can add some additional attenuation.
Either with an attenuator, or another splitter.

Rich

Around 20 years ago, I lived less that 1 mile from the highest spot in this area.
I was line of sight with all of the TV, Radio, and public service towers.
Using variable attenuators in each feed line allowed me to find a 'sweet spot' where everything was perfectly stable and my coverage was great.
 

Pyr8

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rbm

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What about this setup:

ZFSC-4 way splitter

to

Holland PS-10 DC Power Supply
Holland LA Series PS-10 DC Power Supply and Inserter for Satellite Amplifiers

to

Holland LA-520
http://www.3starinc.com/manuals/LA-Series-Amplifier.pdf

Will I run into any issues with this setup?

I noticed that you (Rich) use the Holland LA-520 in other posts, so I'm assuming they work well and will be compatible with the Mini-Circuits ZFSC 4 way??
I have ten of the Holland LA-520 and they're not too bad. (But not too good either. ;)
They have 20 dB of gain and they're weatherproof.
I've used them for testing and they're easy to take with me when I go to help friends (for demo purposes).
They're cheap and functional.

Rich

Here's a comparison for you.
Each amplifier was mounted right at the antenna and feeding an 8-way splitter.
The 'weakest' frequencies were chosen for this test.
See this previous post:
http://forums.radioreference.com/scanner-receiver-antennas/228728-so-i-bought-antennacraft-st2-scantenna-5.html#post2015393

For this test the antenna was an ST2 on a 10' mast just above ground level.

This using the Holland LA-520



Here's the LNA-1000
 

Pyr8

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So do you think I would be better off with the "LA-520" or the "ZFL-1000LN" at the end of the day?

I have ten of the Holland LA-520 and they're not too bad. (But not too good either. ;)
They have 20 dB of gain and they're weatherproof.
I've used them for testing and they're easy to take with me when I go to help friends (for demo purposes).
They're cheap and functional.

Rich

Here's a comparison for you.
Each amplifier was mounted right at the antenna and feeding an 8-way splitter.
The 'weakest' frequencies were chosen for this test.
See this previous post:
http://forums.radioreference.com/scanner-receiver-antennas/228728-so-i-bought-antennacraft-st2-scantenna-5.html#post2015393

For this test the antenna was an ST2 on a 10' mast just above ground level.

This using the Holland LA-520



Here's the LNA-1000
 

rbm

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So do you think I would be better off with the "LA-520" or the "ZFL-1000LN" at the end of the day?
My guess is that they'd perform about equally.

The gain on both is around 20 dB.
The ZFL-1000LN noise figure is around 3 dB. I would think the Holland wouldn't be any better.

If you have the ZFL-1000LN on the way, I'd just wait and try it out.

If you ever do decide to try the LA-520, the cost would only be around $15 to experiment with it.

For most signals you probably won't need much of an amplifier. (or none at all)

For the very weak signals it can make the difference between hearing them or not hearing them at all.

You can see that by looking at the 852.5625 MHz signal on the LNA-1000 test.
It's there but weak. I could hear it.
With the LA-520 (and probably on the ZFL-1000LN as well) you would never even know there was a signal there.

Rich
 

rbm

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And to add another image ....................

Here's what the LNA-580 does during the same test. (10-580 MHz)

Notice that even though the LNA-580 isn't spec'd that high, there is still a 'perceptible' signal at 852.5625 MHz.
It's not something you could listen to, but you know it's there. ;)

The LNA-580 has just slightly more gain (23 dB), but a much better noise figure (0.7 dB).

Rich

LNA-580
 

Pyr8

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What about this setup:

ZFSC-4 way splitter

to

Holland PS-10 DC Power Supply
Holland LA Series PS-10 DC Power Supply and Inserter for Satellite Amplifiers

to

Holland LA-520
http://www.3starinc.com/manuals/LA-Series-Amplifier.pdf

Will I run into any issues with this setup?

I noticed that you (Rich) use the Holland LA-520 in other posts, so I'm assuming they work well and will be compatible with the Mini-Circuits ZFSC 4 way??

Would I also require a splitter (circled in red) as per the photo, or is it not necessary with the "Holland PS-10 DC Power Supply" and the "LA-520"???

 

prcguy

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The thing that looks like a power splitter is a power inserter for the amp, it puts voltage up the coax at the same time RF goes the other way. I personally don't believe the .7dB noise figure spec on the Holland amp and suspect its much higher.
prcguy

Would I also require a splitter (circled in red) as per the photo, or is it not necessary with the "Holland PS-10 DC Power Supply" and the "LA-520"???

 

Pyr8

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Sorry, I'm confused as to weather or not I require the "power inserter" (as per your photo) with the Holland Amp as well as injector, or is the functionality built in to their solution?



The thing that looks like a power splitter is a power inserter for the amp, it puts voltage up the coax at the same time RF goes the other way. I personally don't believe the .7dB noise figure spec on the Holland amp and suspect its much higher.
prcguy
 

rbm

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Sorry, I'm confused as to weather or not I require the "power inserter" (as per your photo) with the Holland Amp as well as injector, or is the functionality built in to their solution?
You need a way to get DC power to the amplifier.

That power inserter feeds the required DC up the coax to the amplifier.
One port passes DC, the other blocks the DC.
You need to attach a 12Volt 'wall wart' power supply to that black connector on the power inserter.
(Obviously you'll need to ensure the correct polarity.)

The Holland LA-520 amplifier doesn't even come close to a .7 dB noise figure. It's much higher than that.

Rich

 
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