Multicouplers

[tip]

Anyone have any experience using the CCW VHF/UHF Multicoupler? Is it on par with something like the Stridsberg MCA204M? I have the MCA204M, but need another port (but not 8). I believe the CCW MC has 5 ports, and would represent a savings over having to upgrade to the MCA208M.

 

[Ubbe]

It looks as if they use the exact same case? The specification looks sligtly better for the CCW. But neither of the two specify the noise factor.
Stridsberg probably have some gain so you could use a 1-2 CATV splitter that costs $5 to add another port and then some BNC adapters or coaxes. Use those outputs on the least critical monitoring if the loss turns out to be 2-3dB. No need to spend hundreds of dollars just to have one more output port.

/Ubbe

 

[prcguy]

Looking at some of the critical specs on a Stridsberg MCA204M I see its very disappointing with a 1dB compression at 17dBm and an IP3 of only 32dBm. Using an active multicoupler is essentially the same as using a preamp, which I've been fighting with over the last month or so. If I put a Stridesberg MCA204M in line with my Discone my reception would suck due to lots of Intermod generated by the little amp in the Stridesberg. In some RF rich areas like where I live you have to do much better or suffer.

I recently went through a couple of preamps here experimenting and so far the one that does not seem to cause any IMD with FM broadcast showing up where it doesn't belong and a raised noise floor of IMD is a preamp with a 1dB compression point of around 30dBm and an IP3 of 46dBm. Thats over 10dB more on IP1 and 14dB more on IP3. This amp alone was $150 and you would still need a 4 way divider at another $80 to $100, but in using these discreet parts you would have a bullet proof VHF/UHF multicoupler.

You can usually get an idea of the high signal level handling traits of a preamp by how much power it uses. Little tiny $1 pill type amps on a circuit board like Stridesberg uses draws about 85ma @12V. That's not much. The preamp I found that is not creating any problems draws about 525ma at 12v and has a big heat sink for about 11dB gain.

 

[mule1075]

Looking at some of the critical specs on a Stridsberg MCA204M I see its very disappointing with a 1dB compression at 17dBm and an IP3 of only 32dBm. Using an active multicoupler is essentially the same as using a preamp, which I've been fighting with over the last month or so. If I put a Stridesberg MCA204M in line with my Discone my reception would suck due to lots of Intermod generated by the little amp in the Stridesberg. In some RF rich areas like where I live you have to do much better or suffer.

I recently went through a couple of preamps here experimenting and so far the one that does not seem to cause any IMD with FM broadcast showing up where it doesn't belong and a raised noise floor of IMD is a preamp with a 1dB compression point of around 30dBm and an IP3 of 46dBm. Thats over 10dB more on IP1 and 14dB more on IP3. This amp alone was $150 and you would still need a 4 way divider at another $80 to $100, but in using these discreet parts you would have a bullet proof VHF/UHF multicoupler.

You can usually get an idea of the high signal level handling traits of a preamp by how much power it uses. Little tiny $1 pill type amps on a circuit board like Stridesberg uses draws about 85ma @12V. That's not much. The preamp I found that is not creating any problems draws about 525ma at 12v and has a big heat sink for about 11dB gain.

What preamplifier are you referring to do you have a link?

 

[tip]

It looks as if they use the exact same case? The specification looks sligtly better for the CCW. But neither of the two specify the noise factor.
Stridsberg probably have some gain so you could use a 1-2 CATV splitter that costs $5 to add another port and then some BNC adapters or coaxes. Use those outputs on the least critical monitoring if the loss turns out to be 2-3dB. No need to spend hundreds of dollars just to have one more output port.

/Ubbe

Remembered that I had one of those 1/2 splitters in my junk box. I tried two configurations.... this one worked best (receive signal strength, etc): the antenna LMR-400 feedline to the input of the splitter, with one side going to the input of the multicoupler, the other to my 5th radio (SDR). Think this will do for now. Thanks for the memory jog.

 

[tip]

Looking at some of the critical specs on a Stridsberg MCA204M I see its very disappointing with a 1dB compression at 17dBm and an IP3 of only 32dBm. Using an active multicoupler is essentially the same as using a preamp, which I've been fighting with over the last month or so. If I put a Stridesberg MCA204M in line with my Discone my reception would suck due to lots of Intermod generated by the little amp in the Stridesberg. In some RF rich areas like where I live you have to do much better or suffer.

I recently went through a couple of preamps here experimenting and so far the one that does not seem to cause any IMD with FM broadcast showing up where it doesn't belong and a raised noise floor of IMD is a preamp with a 1dB compression point of around 30dBm and an IP3 of 46dBm. Thats over 10dB more on IP1 and 14dB more on IP3. This amp alone was $150 and you would still need a 4 way divider at another $80 to $100, but in using these discreet parts you would have a bullet proof VHF/UHF multicoupler.

You can usually get an idea of the high signal level handling traits of a preamp by how much power it uses. Little tiny $1 pill type amps on a circuit board like Stridesberg uses draws about 85ma @12V. That's not much. The preamp I found that is not creating any problems draws about 525ma at 12v and has a big heat sink for about 11dB gain.

Money is a factor...so, on to the splitter!

 

[prcguy]

Its in a thread about my tower top filter/preamp in the scanner antenna section. This is the preamp I had to go with for the 118 to 512MHz range, although the amp goes down to 50MHz. Even with its huge signal handling specs I would not run it without an effective FM broadcast trap filter in front. Anything smaller in signal handling just made IMD and raised my noise floor too much.
https://www.minicircuits.com/pdfs/ZHL-1010+.pdf

This is the FM trap filter that really works with otherwise minimal insertion loss. https://www.minicircuits.com/pdfs/ZBSF-95+.pdf

What preamplifier are you referring to do you have a link?

 

[mule1075]

Its in a thread about my tower top filter/preamp in the scanner antenna section. This is the preamp I had to go with for the 118 to 512MHz range, although the amp goes down to 50MHz. Even with its huge signal handling specs I would not run it without an effective FM broadcast trap filter in front. Anything smaller in signal handling just made IMD and raised my noise floor too much.
https://www.minicircuits.com/pdfs/ZHL-1010+.pdf

This is the FM trap filter that really works with otherwise minimal insertion loss. https://www.minicircuits.com/pdfs/ZBSF-95+.pdf

Thanks for the link.

 

[Ubbe]

This is the FM trap filter that really works with otherwise minimal insertion loss. https://www.minicircuits.com/pdfs/ZBSF-95+.pdf

They could name it more truthfully as 70MHz-115MHz bandstop filter. Seems really good for people who still would like to monitor VHF air when using a FM trap filter.

/Ubbe

 

[Ubbe]

I tried two configurations.... this one worked best (receive signal strength, etc)

Probably a good thing to add 3dB attenuation from the splitter as Stridsberg multicouplers seems to get easily overloaded and de-sense. If it where of higher quality it would have worked best to split after the multicoupler. If you have another 1-2 splitter, try to put that inline as well, or switch to a 1-3 or 1-4 splitter, and see if the additional attenuation will improve the signal even more for the other receivers. The best thing when using external antennas are to always have a variable 0-20dB attenuator to try at different points in a receive chain to see if something are overloading and in need of a reduces signal level, either by frequency dependent filters or by attenuating the whole frequency range.

/Ubbe

 

[tip]

Probably a good thing to add 3dB attenuation from the splitter as Stridsberg multicouplers seems to get easily overloaded and de-sense. If it where of higher quality it would have worked best to split after the multicoupler. If you have another 1-2 splitter, try to put that inline as well, or switch to a 1-3 or 1-4 splitter, and see if the additional attenuation will improve the signal even more for the other receivers. The best thing when using external antennas are to always have a variable 0-20dB attenuator to try at different points in a receive chain to see if something are overloading and in need of a reduces signal level, either by frequency dependent filters or by attenuating the whole frequency range.

/Ubbe

I did try the splitter after the coupler, but seemed to loose sensitivity. Don't have any testing equipment (or skills to do so), just basically relied on how the radio (BCD536HP) behaved. Signal strength suffered in this scenario. Will look into the attenuation aspect though. Thanks.

 

[Ubbe]

If you add attenuation, like from a 1-2plitter that attenuates 3-4dB, and the reception improves, then the device after the attenuation are exposed to high levels of signal that actually de-sense it and loose sensitivity. Reducing the signal to a level where it can handle it will restore full sensitivity. Having a variable attenuator at hand and using it at different points in the chain will usually quickly reveal where the problem are.

In your case it seems as if your receivers can handle the signal levels but not the Stridsberg. Filtering out broadcast radio and tv from the signal could be enough to not overload the amplifier in a multicoupler or receiver.

/Ubbe