Has anyone ever repurposed a video distribution amp as a receive multicoupler?

[WB2EMS]

Another department is clearing out some RGBS distribution amplifiers and I got to looking at them. Unity gain, 75 ohm, 1:4 port, looks like  they go to 300 mhz or better. Sound a lot like the multicouplers we used to use to feed a rack of receivers from a single antenna. Has anybody ever tried using them that way? Too low in sensitivity or too noisy maybe? I've scored one against this idea, but might want to go back for some more before they go away tomorrow.

[W1ITT]

Video DAs typically deal with a volt of video, whereas receiver multicouplers are dealing in microvolts.  I'm not sure how noisy they would be when operated at very low levels.  Also make certain that they aren't, for some reason, outputting a DC voltage that might be unfriendly to your receiver's front end.
But if you already have one, it can't hurt to give it a try as a one in, one out first and see what happens.

[WBear2GCR]

Kevin,

Maybe open one up and see what they are using for the amps? Discreet? Chip? Read the numbers, look it up and you will get pretty close to the noise figure.

Then too, you can put it on the front of a quiet receiver and compare the noise floor with the input of the receiver shorted to the input of the amp shorted... assuming it is a unity gain device. If it has gain then you'd want to consider that contribution in dB.

Seems like a possible plan.

                    _-_-

[WB2EMS]

I started to do those things last night and got held up by finding that both of the units had between .4 and .6 volts on all the outputs. Need to get some dc blocking in there somehow and then move forward with some testing. I'll report back when I have some results.

[N8ETQ]

   I feed up to 8 RX's from a common antenna with
Mini-circuits PSC-8.  (Power Splitter/Combiner)
8 ports out 50 ohm .5 to 175 Mcy.

   These were used in computer "Clustering"
applications. On HF the loss is negligible.

   A small preamp would easily overcome the
small loss.


http://www.everythingrf.com/products/power-dividers/mini-circuits/612-12-psc-8-1


GL

/Dan

[Opcom]

I've used them. A blocking cap in and out is good. They are usually good from around 50Hz to 6-10MHz, but you can hack them for higher frequency bandwidth and put in small coupling caps going in to restrict the low frequency response.

[WB2EMS]

They are usually good from around 50Hz to 6-10MHz, but you can hack them for higher frequency bandwidth and put in small coupling caps going in to restrict the low frequency response.

I think the ones I've been looking at are good up to 300 mhz or so. We're used for high end visualization monitors.

[pa0ast]

Video distribution amplifiers are very good amplifiers , flat amplitude and phase respons from DC or nearly dc  till  over 100 MHz with  low noise figures used in studio's. If they were not very good the tv programs had problems with signal to noise ratio's  and color change due to differential phase and gain.
The input is often High impedant at two input connectors and You have to connect a 75 Ohm resistor to one to make it a 75 Ohm input
 With a 50 Ohm loadresistor on one connector its 50 Ohm in. The output is 75 Ohm with resistors You can change them to 50 Ohm ones for Your purpose. DC output should be 0 V and can be adjusted usual  with a potmeter. As wel the gain and phase response.
Anton