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[Scott Holtzman]

Hey all, first post here!

going back to the combiners...

Are there noticeable differences?
Do specific combiners work better with units of the same manufacturer?
what kind of specs can we use to measure these types of properties?

thanks!



-Nathan

RF doesn't know who manufactured it.

The onus is on you to choose the right 3rd party combiner.   Power, Q, circulators, lots of chances to make a mistake. 

To me doesn't seem worth the savings.

[Brian Hancock]

Hey all, first post here!

going back to the combiners...

Are there noticeable differences?
Do specific combiners work better with units of the same manufacturer?
what kind of specs can we use to measure these types of properties?

thanks!

-Nathan

Nathan, I think most would agree with wireless you get what you pay for ... all the listed models are quality units and work very well, however there are some subtle differences ... for example some have internal amplifiers that make up for the loss of the combiner and that power is selectable, or they have a external input to combine multiple combiners

but in all but the absolutely most demanding environments all will work very well.

[Scott Holtzman]

[8quote author=Nathan.McBee link=topic=166778.msg1539527#msg1539527 date=1522285594]


-Nathan


Nathan, I think most would agree with wireless you get what you pay for ... all the listed models are quality units and work very well, however there are some subtle differences ... for example some have internal amplifiers that make up for the loss of the combiner and that power is selectable, or they have a external input to combine multiple combiners

but in all but the absolutely most demanding environments all will work very well.

I have never seen a combiner with an amplifier.   You might be thinking about an RX Multicoupler

[Nathan McBee]

well, lets take for instance the GX-8.
It seems to have an input sensitivity that favors a certain mW input.
Or the Shure PA821 is said to have a fair bit of gain loss when you use the expansion port and another combiner.

I'm wondering if others have experiences or opinions regarding these sorts of things.
If there are noticeable differences of linearity, etc.

[Scott Holtzman]

well, lets take for instance the GX-8.
It seems to have an input sensitivity that favors a certain mW input.
Or the Shure PA821 is said to have a fair bit of gain loss when you use the expansion port and another combiner.

I'm wondering if others have experiences or opinions regarding these sorts of things.
If there are noticeable differences of linearity, etc.

It's actually an amp on every input.  From the vendors site "Each input contains its own discreet RF amplifier and proprietary ALC circuits."

Now if they can just spell discrete.

[Henry Cohen]

well, lets take for instance the GX-8.
It seems to have an input sensitivity that favors a certain mW input.
Or the Shure PA821 is said to have a fair bit of gain loss when you use the expansion port and another combiner.

I'm wondering if others have experiences or opinions regarding these sorts of things.
If there are noticeable differences of linearity, etc.

First, as Scott noted, active combiners have amplifiers on each input that raise the carrier power to a level to compensate for subsequent combiner and insertion losses (~7dB for 4-way, ~10dB for 8-way) in unity gain units (Shure, Sennheiser, RF Venue, AT, etc). For those combiners that offer variable output levels, the amplifier stage provides additional gain beyond the combiner/insertion losses with, generally, a switchable attenuator on the output (GX-4 & GX-8), or by attenuating at the input to the amplifier (RAD TX-8).

Amplifier gain, noise figure, 1dB compression point ("P1"), third order intercept point ("IP3"), linearity and cooling are the real drivers behind the quality and cost of the combiner, along with packaging and any additional features. Digital transmission schemes and RAD's double sideband AM transmission are the most taxing on amplifier stages; amplifiers in combiners for these transmission schemes require high linearity and a very good IP3.

The expansion port on the Shure PA8/421 combiners is simply a high power passive 2-way splitter/combiner with about 3.5dB total loss.

[Brian Hancock]

The expansion port on the Shure PA8/421 combiners is simply a high power passive 2-way splitter/combiner with about 3.5dB total loss.

Henry correct me if I'm wrong but are isn't the shure combiner essentially just a mini circuits zapd-2-1 (think I got that product id close)

basically a 2 to 1 combiner splitter ?!?

[Henry Cohen]

Henry correct me if I'm wrong but are isn't the shure combiner essentially just a mini circuits zapd-2-1 (think I got that product id close)

basically a 2 to 1 combiner splitter ?!?

Actually, more like the ZAPD-900-5W-N+. Yes, it's a standard Wilkinson circuit.

[Andrew Broughton]

The RF Venue combiner seems relatively inexpensive compared to the others. Anyone know what's different about it?

[Nathan Riddle]

The RF Venue combiner seems relatively inexpensive compared to the others. Anyone know what's different about it?

Chris of RF Venue via email (I was asking questions) said their inputs are 100mw capable.

And that's all that I can contribute to this convo 

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