Using MFJ-916B Duplexer (

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2 жыл бұрын

David, N9BSA, is trying to merge two antennas using a Diamond Phasing Harness ss770r, but Dave has a better suggestion....
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Пікірлер: 29

@3dPrint_and_chill 2 жыл бұрын

Good luck with those 800+ emails! 😬

@davep6977 2 жыл бұрын

Here's a little tip I started using over the years. He has the perfect solution, but I found wx proofing all the connectors a pain. What I do is make a ray dome or weather head. Get like a 3 inch diameter pvc drain pipe ( a foot or so long) and a cap at the local hardware store. Mount it on the mast with zip ties (vertically with the cap on top) and put the duplexer inside it and all 3 coaxs coming out the bottom. I stuff some Styrofoam or steal wool in the bottom to keep birds out. Taping the PL-259 won't hurt but I got tired messing with rubber or butyl tape. I use them on all connections like were I go from hardline to 213. Since water can't run up hill everything stays dry.

@darinhitchings7104 2 жыл бұрын

great advice!

@billrupp9261 2 жыл бұрын

FYI, I use one for my satnogs station. I ordered the outdoor mastmount version and they had the silkcreening for the bands backwards.. They did send me a replacement unit.

@VE9ASN 2 жыл бұрын

Great video, as always! I'm curious if there is a device that works similarly, but let's both antennas aid in receiving on both bands, but still offers the isolation on transmit? 73!

@ntrjohn 2 жыл бұрын

Great video as always Dave! Thanks for sharing your knowledge and for all that you do for Amateur Radio. One thing to be aware of: You mentioned using the duplexer outside at the antenna but the product description on MFJ's website states "The MFJ-916B is designed for indoor use. If you use the MFJ-916B outdoors, it should only be used for short periods of time under good weather conditions. Do not use the duplexer outdoors when there is any kind of precipitation." Again thanks for all your knowledge sharing! -John KN4YMJ

@davecasler 2 жыл бұрын

Indeed, needs to be protected from rain.

@eccolture 2 жыл бұрын

How far from each other have to place the vhf and uhf antennas?

@darinhitchings7104 2 жыл бұрын

Question: can this duplexer be used for HF on one port and UHF / VHF on the other? Is there any frequency dependence here? Other small question, for connections outside, are you putting anything on the external connections to seal them against water and snow?

@Johnyrocket70 2 жыл бұрын

Antenna switch

@prestonshute7243 2 жыл бұрын

Dave Did you make a video on the DX Commander vertical? 73 wd4dda

@davecasler 2 жыл бұрын

Not yet. Still uncompleted.

@daveN2MXX 2 жыл бұрын

Please cue the duplexer vs diplexer comments!

@ianharling9569 2 жыл бұрын

I would call that device a Diplexer. 73.G7HFS/PA3IKH

@davecasler 2 жыл бұрын

I agree--I can't keep straight which are which. MFJ calls it a duplexer.

@subramanianr7206 2 жыл бұрын

@@davecasler hi, a Duplexer is a contraption meant for separating Rx and Tx signals within a ham band. We use a Duplexer in the 2 meter repeaters. The difference is just 600 kHz and it needs a very high Q band reject notch filter. Cascading 3 or more such filters would offer attenuation in the order of 60-90dB. It can use even use a single antenna. The front end of the Rx is well protected as the high power output from the TX would not enter into the Rx. The Rx receives the signal from a HT at a distance and the same is being transmitted almost simultaneously in high power with a 600 kHz (+/-) difference. A Diplexer is a device used to separate the Rx and Tx signals between two amateur bands; that's what you discuss here in the video. MFJ has erroneously labelled it as a Duplexer. De VU2RZA

@KA9DSL Ай бұрын

David, it's called a Diplexer not a Duplexer. The two have totally different uses. I'm a retired TV Radio transmitter engineer, we know the difference! Be correct.

@mrkattm 2 жыл бұрын

You really don't need to use a duplexer for one radio and two antennas, just put the two antennas in parallel on the same coax with a Tee connector. 2meters and 70 cm are far enough apart that the opposite antenna of the band you are are on will be at a high enough impendence to reject the signal and the antenna of the band you are on will be at 50 ohms and vice-a-verse. Think fan dipole, you don't use a duplexer in that situation. Also, you must keep your antennas a 1/2 wave length apart and follow all the other rules of antenna placement but the duplexer in this situation is definitely a belt and suspender kind of thing. If you take the duplexer apart you will see that it is a high pass and low pass filter network that in the best case scenario has 1.5 dB insertion lost in the transmit path which is nothing on 2 meters but starts to add up on 70cm when you take into account all the other .5 dB- 1 dB insertion loses you have in the signal path. Important, you MUST use the duplexer with two radios and one antenna, failure to do so will be catastrophic.

@darinhitchings7104 2 жыл бұрын

Great advice, appreciate it

@ahbushnell1 2 жыл бұрын

Must be a low pass and high pass filter.

@ernestb.2377 7 ай бұрын

I know you old-skool ham's don't care much for terminology, as obviously the MFJ producer also doesn't, but what you describe here would de a diplexer and not a duplexer. As I see with decade long ham's I talk to, they would say pateto-potato, but diplexer and duplexer are very different circuits. A duplexer would be more of a circulator, and hence the name duplex (2-way) 1 path (1 way street) goes from the transmitter to the ant., and the other path (also 1 way) goes from the ant. to the receiver. Typical separation about 60dB. A diplexer is more of filter and separates based on the freq. Advantage of being a novice is the necessity to look things up for the first time 😀 But the old-skool ham's know what they are talking about, regardless of the terminology, I understand that, so no warries about that part. You can call it whatever, they know how it works, and I am just starting to learn...

@ernestb.2377 7 ай бұрын

...and one more thing, as the most of the people calling it a duplexer it "becomes" a duplexer.

@SJKile 2 жыл бұрын

Well this isn’t about the MFJ-916B. At the very least if you say you’re going to talk about something, talk about it first so you don’t waste my time.

@rsluggy6485 2 жыл бұрын

Did you watch *this* video before writing that comment? This video is about two practical applications of the MFJ-916B. One of those use cases addresses the viewer's issue, which was outlined in the introduction of the video.

@darinhitchings7104 2 жыл бұрын

And you paid how much for this content again?

@SJKile 2 жыл бұрын

@@darinhitchings7104 Every month I have $12.86, $154.32 a year deducted by Utube. How much are you paying?

@darinhitchings7104 2 жыл бұрын

@@SJKile yes I'm paying KZfaq but that's not the question I'm asking. I'm asking how much did you pay Dave Casler to produce this video?

@SJKile 2 жыл бұрын

@@darinhitchings7104 Myself, & others, that watch ads pay Utube & Utube pays the content creators. They aren’t doing it for free & I’m not watching for free either. Why don’t you ask him how much money he got for his video. Besides, I determined early on that it was not what I wanted.