MFJ 916B Duplexer - Tested and Reviewed

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[@paulbock1867]

From K4MSG: Excellent review, very comprehensive. I used one of these to "split" 144 & 432 from a single-port radio for EME on both bands and never any issues, but I do strongly advise using external preamps on receive to mitigate the insertion losses due to the extremely weak signals on EME. I was also using external PAs on transmit. Please note that I also used the "BN" version of the MFJ device because I'm a stickler for using Type N connectors on 144 & above.

[@bosspatis369]

Hi. Is it possible to use a dual.band radio base and a portable that has a cross band repeater capability (Retevis Rt23) on this duplexer? Thanks.

[@PsynceFiction]

Question: I want to use an Endfed 80-10m antenna for listening (on a receiver) in the livingroom downstairs, and for transceiving in the attic. Is this MFJ-916B duplexer what I need then? Thanks for the review!

[@JayN4GO]

They also market these as bandpass filters for us sat operators. Do you see adequate low pass and high pass filtering in this device ?

[@stevec5000]

You were correct about the connector, it does break loose from the PCB pretty easily but it's not just the one, since they are only held with a setscrew all of them can twist and break loose if you aren't careful.

[@theradiomechanic9625]

With anything MFJ I pull it apart and check connections and hardware before use. Treat their products like a partially built Heathkit. Stuff usually works fine once it is gone over.

[@jimeagle1]

There is definitely truth to what you say. QCBC is rampant these days whether by MFJ or Walmart. "QCBC" = Quality Control By Customer. ;-)

[@sergiocavazos8963]

broke one myself... when tried to disconnect the cable it was stuck to the duplexer... use pliers and ended up whith the conector of the duplexer in my hand... very sad... mfj quality control is shown again

[@M9A1MAN]

Can I transmit on the vhf radio and uhf radio at the same time?

[@K1QS_Radio]

now that's a review! thank you.

[@theradiomechanic9625]

Your welcome, that one was fun.

[@dalewdavis3034]

Thumbs up...very detailed. .thank you

[@borayurt66]

Very informative and well done review. Thanks for your time and effort. I am using a homebrew diplexer which I made using a schematic found on the internet. I have tested it with a SWR/Power meter and an actual transmitter as the power source :D, using a dummy load (homebrew again) got very good results. But unfortunately I do not have equipment to test insertion loss accurately.

[@theradiomechanic9625]

Hi Bora. Thanks for watching and thanks for the nice comment. Couldn't pass it up for the price. Would have "rolled my own" but by the time you do all the work and buy an enclosure it would end up costing as much. The unit works surprisingly well for the price. Vern

[@mahdihutalla2737]

diy vhf antenna duplexer schematic diagram

[@mahdihutalla2737]

Sir please help search that schematic diagram

[@jimeagle1]

Your results square with mine in a review of this product I did about a year ago. I also show what I did to weatherize the unit for my California location in San Jose. Your recommendation of using a box is the best way to go about it, of course, but mine has worked for quite some time in our relatively mild weather. I used it to be able to use a single coaxial cable up beyond my antenna rotor where I then mounted the Diplexer and split off to the 2m and 70cm antennas. I also concluded that this unit is not suitable for use at 220-225 MHz. I played around with the tuning of the inductors a bit but could not improve performance on this band. WB6JNN

[@theradiomechanic9625]

Hi James, Thanks for watching and confirming my data. I bought the unit strictly for a dry location so was not too worried about it. Just happy I didn't intend to use 220. Otherwise not a bad unit. A cleaver ham will find a way to weatherproof things. Even so called weatherproof items will benefit from a "rain hat" if only to keep the UV off of them. 73 N1CKX

[@uforover3596]

I would advise against trying to 'seal up' a unit like this and put it out in the bare elements (Instead leave it unsealed with a vented enclosure around it.) Here's what is going to happen. Hot day, black box, it gets warm. Rain comes along, quickly cools down unit and a vacuum develops inside and sucks a small pinhole in your sealing job. It then sucks in MOIST AIR which will eventually condense and now you have water inside the unit. WORSE, that water has no way to drain out. Same thing can happen during simple diurnal temperature changes. It needs a way to 'weep'. The same problem occurs with hollow feedline up a tower when someone weather seals BOTH ends of a run... not supposed to seal up the 'shack end' so that when the temperature change hits, it will suck air out of the unsealed shack end. This is why many hollow hardlines are charged with gas (nitrogen?) to keep 'moisture ingress' from happening. So by sealing it up and putting it in an environment where it was not designed to be, you just created the problem you were trying to avoid. NEVER seal units like this, especially remote coax switches... you are CREATING a problem. The manufacturer knew what they were doing by leaving the 'underside left open to provide a 'weep' path.

[@jimeagle1]

As I indicated in the video I did this experiment to see what would happen and I specifically suggested that it was not appropriate for climates not as moderate as that of San Jose, CA. However I absolutely agree with your comments about trying to hermetically seal things that are left in the environment, especially in climates subject to constant humidity, heat, sudden changes in air pressure and temperature, heavy rains, snow, ice, and so forth. I have often seen the results of trying to do this in my professional work (I'm now retired) where waveguide based antennas were mounted between railroad tracks for an RFID system but have gotten water in them due to flooding and wouldn't drain afterward because the water had no way to get out. On the other hand, I've also designed sealed RFID tags about the same size as the MFJ unit that were used for auto assembly lines that survived hundreds of cycles through various dip baths (up 5 ft deep), cleaning spray operations, paint operations which included high temperature ovens (400 F), and the typical heavy vibrations and jolts (>10 G's) along an assembly line... all without leaking. So I know that one can seal such items if sufficient care is taken. The best solution for a mast mounted duplexer is the one that MFJ offers. The MFJ-916BM (UHF connectors) and 916BMN (N connectors) are mounted in a box in the manner that you suggest. Unfortunately this unit seems to only be available directly from MFJ thus the listed $59-69 price is increased by the additional shipping costs required to get it from MFJ to the customer. I actually have a

[@sergiocavazos8963]

@@uforover3596 you are totally right! saw that video in the one that ask to seal very well the duplexer... big mistake, the water went in with no where to get out... now i'm installing this mfj duplexer again up in the antenna mast (one brand new) and what I did was sealing the upper part only, and taking out the two lower screws . It's better to have a place where the water or moist can get out... The first sealed duplexer was totally distroyed in very short time, lets say a year, ... was corroed and had moist inside with a white pouder , went directlly to the garbage can.

[@13yearsaprepperr.jtilbury.51]

what i find anoying is on the ft897 the 2 metre and 70 cm are on on antenna and the hf is on the other antenna out ,,, these duplexers dont work on them as theh share the HF and VHF on one leg UHF on thr other

[@ayieAbj]

hi, i use 2 radio at the same time..1 for uhf and 1 for vhf (2 meter) so now i want to use 1 antenna only (dual band) and my question cant i use this MFJ 916B for 2 radio 1 for uhf and 1 for vhf (2meter) ...tq... de 9W2YDB - ayie

[@theradiomechanic9625]

Yes sir. Put the Dual band on one port and the Radios on the other. Works like a charm.

[@subzerolives]

@@theradiomechanic9625 can these be used for shortwave listening? For example 1 antenna 2 receivers?

[@theradiomechanic9625]

@@subzerolives Not in the traditional sense of "Shortwave". These are for VHF/UHF.

[@watson946]

I opened my n type version of this unit, capacitors have 500 v printed on them.

[@budprepper3811]

very good, thanks

[@davemallett1239]

That is because you decided to go with pl-259/so239 There okay for HF … Go (N) and you may have a more harmonious outcome.

[@kansas7614]

Can you use this unit for 2 uhf radios to 1 antenna? 1 for RX and 1 for TX, Do I need a Diplexer or Duplexer, Sorry I'm new this ham radio.

[@theradiomechanic9625]

This will provide enough isolation in most cases to allow a 2 meter radio and a 70 cm radio to share a dual band antenna. Info on the MFJ web site.

[@kansas7614]

The Radio Mechanic Thank you very much for your reply. 73s

[@AlexCausey]

Questions, is the wattage rating of 200 Watts CW or PEP? My stepfather is running TE system 1410 G linear rated at 160-200 watt output @144 MHZ and 4410G TE linear 430 MHZ @ 100watts. If I changed the caps to Silver mica at higher voltage do you think I would be OK? -N6JJI Maybe this would be a better choice? click on link: www.ebay.com/itm/Maldol-Antenna-HS-790D-RF-Microwave-Duplexer-HF-144-430MHz-VHF-Type-N-m-50Ohm-/272863972974?_trksid=p2385738.m4383.l4275.c10

[@theradiomechanic9625]

Hi Alex, MFJ doesn't say. However I find that they are usually very "generous" on their ratings. That is, I would be careful when approaching 200 watts. Changing over to high voltage SM caps is a good Idea. However you probably will need to tune it again with a network analyzer.

[@ernestb.2377]

As a novice radioamateur I realize the terminology confusion. Experienced hams use the term interchangeably, but a novice needs to look it up. My colleague at work has some 40+ years experience and says yesterday diplexer and duplexer is the same, as both starts with du.. and di... what means 2 🤔 Not quite as I read. The term Duplexer comes from 2-way communication, and clearly has different application. It has more in common with a circulator, and maybe that would be a synonymous, as I am really a novice. I was looking for a circuit that separates my rig from a SDR RSP1A receiver, both being connected to 1 antenn. The reason is that I have an Yaesu FT450D rig, of course without fancy waterfall visualizations and I have the SDR I could use "at the same time". The duplexer could do the work but I could not be able to receive on both devices. Maybe I wouldn't need to, as the SDR receives very well. There are even ways to move the Yaesu freq. simultaneously from the PC, and other way around. Back to terminology, what you tested in the video would be a diplexer (according to a quick internet search). Thanks for the insights and this video channel! Cheers

[@RuossFamilyAdventures]

Hello i'm want to build a GMRS Repeater do to in PA we don't have a lot of Repeaters here and don't have a lot of cash do to being on disable i was wanting to know if i have to buy a Duplexer like this or one of the Black Boxes and do i have to buy 2 annts for this

[@theradiomechanic9625]

This type of duplexer is for separating two different bands. GMRS is all in one band and uses a 5 MHz split. You will need something like a cavity duplexer for that application and they are not cheap.

[@RuossFamilyAdventures]

The Radio Mechanic I have not found one yet in my buget and the other thing the wait time

[@searchingthethruth4776]

Sir,is this product will fit to my 2 baofeng repeater at frequency around 147.000 to 148.000 mhz..i have no idea on my project..

[@DJCaverna]

perfect review .... for me decide if i get one or not ... i think the duplexer for 1.5 to 150mhz and 430 to 460mhz its perfect for the price payed hehehe ... tanks again .. de PY7DJ - NETO (BRAZIL)

[@theradiomechanic9625]

You are welcome, I am happy to see the information is useful.

[@leadfarmer4life335]

well that sucks, I just bought one for 220. dangit.

[@theradiomechanic9625]

I'm soooooooo sorry.....