PMP450 3GHz - Why the 4 prong power plug?

First, I absolutely am loving the PMP450 3GHz product line. It’s blowing away anything we’ve ever seen in LTE from a capacity and performance standpoint. And the cnMaestro system makes it a breeze to administer.

Now - the only “what were they thinking” concern we’ve run into is the power connector on the Medusa product line.

“What were they thinking???” Why are we running tiny little 4 wire power into the connector rather than just larger 2 wire like every other radio unit takes? The 4 wire creates all kinds of issues – the conductors are very little, so more fragile; the requirement to find 4 wire DC cable rather than the standard 2 wire; extra parts to break.

Is there a good reason why the 4 wire was chosen? Am I missing something here?

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I think there were some plans to be able to use the extra leads to provide a sync source over power to the radio. You’d use this if you were just using fiber and DC to the radio.

I mean… that would be awesome! But then, can you run the DC on just 2 wires? Or do you actually need the 4?

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You only need 2.

Wasn’t there some concern about the unit not being able to draw enough amperage over just 2 though?

You still wire up all 4 pins, you just use 2 large gauge wires instead of 4 medium gauge wires.

So what, just divide the two wire into the separate pins when it gets to the connector?

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Stupid 20 character requirement. Yes.

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Please be careful in doing this… you need to leave enough length of 4 conductor cable. A voltage differential in a very short cable run (when splitting 2 wires into 4 wires) can be very hard on the power circuit in the 450m. I will work on getting additional information on this, and update this post.

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Thanks for this warning – I’m trying to understand what you’re saying.

In a short run (how short are we talking), why would there be a voltage differential if the two wire splits to 4 wire at the radio? I would think you’d risk the most voltage differential running 4 wire all the way up the tower.

It would be awesome if Cambium would just release a 4 wire to 2 wire adapter plug.

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I was corrected and it’s a current imbalance that worries the engineers.

With 16 or 18 AWG, the 4-conductor cable should be at least 3m in length. Another note on best practice is that this balancing length needs to be straight or bunched, not coiled, to reduce inductive pick-up from surges.

Also, we are looking into an adapter plug as you mention. We are also looking into a variant of the LPU that has input (from the ground) into a 2-terminal screw in connector, then output (4-wire) into the radio.


That would be awesome. Overall this product is amazing. The power plug is by far the worst part of it. The conductors are so small it’s almost hard to work with. Traditionally we run 12AWG up to equipment on towers, but there is no way to get that size of a cable into the connectors for the 4 pin connectors.

LPU variant would also be great, as you could then just buy pre-made jumpers to go from the LPU to the Medusa, and just run standard 12 AWG up to the LPU.

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I too am impressed with the 450M but the power plug to me is an example of over engineering. Look at us, our product is superior because we have engineered a four port plug and the competition uses only a two port. The four wire I ordered from Cambium was metric 0.75mm cable which is the equivalent of 19 AWG. This wire is thin. When you combine the two wires of each polarity, they are still smaller than one 14 AWG wire. Cambium could have kept it much simpler by requiring the use of 14 or even 12 AWG wire and used a much simpler two port screw tighten plug. As a work around, I had someone make up some 4 port jumpers for me and I tie them into our standard 14 AWG two wire cabling via a Transtector DC Defender 48-5.

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Yup. I would much rather see a 2 pin with screw connector.

A 2 pin molex would be fine, with larger wire.

A T-plug would be fine too… any number of things. The 4 plug thing just baffles me.

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Could not agree more with RFWaveRider. The four pin molex connector seems to be a special form of punishment for RF installers. Try putting one of these together up on a tower?

We are starting to use the Transtector surge suppressors as they have a simple screw down terminal connection. Pure genius ; )

Is there an update to this proposed 2-4 pin adapter?

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Almost a year now… how’s the looking going?

FWIW we ordered a handful of these which takes away the tedious crimp/solder of the p4 PSU adapter provided with Medusas. Just cut off the ATX end and butt splice/heat shrink your power cable to this adapter

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Might do that ourselves… thanks for the idea. It is a royal pain in the antenna to make these.

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