DLI Multicoupler Initial Observations

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KC1UA

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Hello,

There has been mention by a few (very old posts) that own them, so as a refresher here's the link:

Wideband RF Multicoupler - 16 Radios, Surge Protected, 50 Ohm

I decided to give one a try given the 15 day return policy. The documentation is adamant that unused ports be terminated. I have the suggested BNC terminators (1/2 watt, 50 ohm) on order. In the meantime I did a preliminary check without them and found this multicoupler's performance to be inferior to that of my 4 and 8 port active Stridsberg units. I have never terminated unused ports on those units and have had no problems. Apparently either it is of the utmost importance with the DLI unit or the one I have is defective.

Testing with an Icom IC-R7100 receiver, I noticed considerable attenuation (or outright non-reception) of signals at higher frequencies, primarily in the 851-860 MHz range, but frequencies in the VHF and UHF ranges are down a bit as well. This is testing with the antenna connected to the multicoupler and then directly to the same antenna via my existing patch panel.

Does anyone have any experience with this? It most assuredly indicates "glaringly" on the front of the unit and in the manual that all unused ports must be terminated, so I'm hoping this is my issue.

Thanks,
Scott
 

prcguy

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Terminating unused ports is standard practice for any power divider or splitter. When they are not terminated you will have some VSWR problems and the frequency response will not be flat and port to port isolation can be degraded. This goes for any splitter including the one in a Stridsberg.

Most people would never notice the degradations unless you use some test equipment to measure the splitter, so not terminating the ports on your new multi coupler is probably not the main problem.
prcguy



Hello,

There has been mention by a few (very old posts) that own them, so as a refresher here's the link:

Wideband RF Multicoupler - 16 Radios, Surge Protected, 50 Ohm

I decided to give one a try given the 15 day return policy. The documentation is adamant that unused ports be terminated. I have the suggested BNC terminators (1/2 watt, 50 ohm) on order. In the meantime I did a preliminary check without them and found this multicoupler's performance to be inferior to that of my 4 and 8 port active Stridsberg units. I have never terminated unused ports on those units and have had no problems. Apparently either it is of the utmost importance with the DLI unit or the one I have is defective.

Testing with an Icom IC-R7100 receiver, I noticed considerable attenuation (or outright non-reception) of signals at higher frequencies, primarily in the 851-860 MHz range, but frequencies in the VHF and UHF ranges are down a bit as well. This is testing with the antenna connected to the multicoupler and then directly to the same antenna via my existing patch panel.

Does anyone have any experience with this? It most assuredly indicates "glaringly" on the front of the unit and in the manual that all unused ports must be terminated, so I'm hoping this is my issue.

Thanks,
Scott
 

EricCottrell

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Hello,

The manual says that it has five 4-port dividers so that is at least 12 dB loss right there, but there is an amplifier to compensate.

The main problem maybe the amplifier in the coupler. The 4-port and 8-port dividers do not need as much gain to overcome the divider loss. The MCA204M and MCA208M has a OP1dB of 17 dBm. The 16-port is -5dBm at 1GHz.

The sensitivity problem maybe due to the coupler being overloaded because of the wide open front end of the coupler.

73 Eric
 

KC1UA

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I assume performance would be similar to that of the Stridsberg units given the indicated low noise amplification to overcome the loss of splitting the signal so many times. If it turns out to be a defective unit I'll return it and just get another 8 port Stridsberg instead. My BNC terminators should be arriving tomorrow so I'll likely know one way or another at that point.

I'm used to terminating unused CATV ports and never think twice about that, but I guess I'll start terminating unused ports on all of my multicouplers as well.

Thanks for the replies and info.
 

KC1UA

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I received my 50 ohm 1/2 watt BNC terminators today and went back to this project. Adding them to the mix made no difference. Using the same test platform of an AntennaCraft Scantenna ST-2 and Icom IC-R7100A receiver, there is a remarkable difference in this case between the receiver being directly connected to the antenna and then via the multicoupler, especially as frequency increases. The difference at VHF-HI was somewhat subtle testing with a distant NOAA weather broadcast on 162.400. Via the Scantenna the 7100a's stingy S meter sat at S1 but the signal was full quieting. Via the multicoupler there is some hiss introduced. The real issues begin in the UHF range where a signal from a DMR control channel with a direct connection to the antenna is an S5, but an S3 through the multicoupler. At 800 MHz, a MOT Type II control channel on 855.5375 (MSP Zone 04) falls from an S8 to an S5 when connecting via the multicoupler.

As prcguy stated above there is no notable difference to the eye or ear whether the unused ports on the multicoupler are terminated or not.

My thought is that either this is defective, or is just not nearly as good a performer as the Stridsberg models. In any case I have emailed DLI's support for their opinions and indicated that I am considering returning it for a refund within their 15 day trial period.
 

KC1UA

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There's a very positive conclusion to this. DLI very quickly responded to my email. Without hesitation they shipped me another unit so that I could compare it to the original. I was pleasantly surprised that they would do so without asking for the possibly defective one back, at least "cross-shipped".

The replacement arrived last Friday, and after some testing there's no doubt that the original was in fact defective. This one performs as I'd expect it to. If there is any "knock" on it I'd have to say that the Stridsbergs may do better at 800 and 900 MHz, but it's not a loss so drastic that it would make me consider returning it. Performance at VHF and UHF seems to be on a par with the Stridsberg units.

I've always been a huge fan of my Stridsberg units, I have a 4 and an 8 port and they'll never leave my shack, but kudos to DLI for being so receptive to a non-government hobbyist user of their products. Great service, and now confirmed good performance as I'd expect.
 
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