Yet Another Multicoupler Thread

[kruser]

Do you hear fm stations out of band now? Also not sure by Civ air you mean airband? If yes fm filters can make a big difference since air and is so close to fm stations being in the 118-134 mhz range. Not sure how mobile antennas would affect it I only have a base station

Airband should really be air bands (plural). There are two, one Civil and the other being the Military air band which is UHF from around 225 MHz up to well above 300 MHz and still using AM modulation. Part of the upper portion of the military air band is now used by P25 military comms systems located across the US at least. Not sure about other countries
FM Broadcast does generally only affect those using radios susceptible to desense from FM Broadcast stations when trying to monitor the civil air band.

 

[dlwtrunked]

Receiver overload can cause intermod *in other bands* even on fairly expensive radios (even premium ICOM receivers including my ICOM R9500) particularly when listening for weak non-local signals and particularly when pushing gain high. I live one mile from a relatively lower powered FM broadcast and 3 miles from one with higher power. There is still a need for the FM block in many environments. My need for FM broadcast band blocks has been driven by problems other than the civil air band where I rarely listen.
Also, desense from FM broadcast station desense can occur clear into higher VHF high band (>150 MHz) *with some radios*--I have seen it and so have others.

 

[yellingsoftly]

Quick question, does anyone know if theres a difference between minicircuits power splitters with + on the end vs not? For example ZBSC-615+ vs ZBSC-615? I see ones on ebay without the + sign some and wasn't sure if just older model or what?

 

[yellingsoftly]

Airband should really be air bands (plural). There are two, one Civil and the other being the Military air band which is UHF from around 225 MHz up to well above 300 MHz and still using AM modulation. Part of the upper portion of the military air band is now used by P25 military comms systems located across the US at least. Not sure about other countries
FM Broadcast does generally only affect those using radios susceptible to desense from FM Broadcast stations when trying to monitor the civil air band.

Your right thanks for the explanation.

 

[APX8000]

I just looked in my future project box and it looks like I need to put a few multicouplers together or do something with all these amps. I found three ZHL-1010s, two ZHL-2010s and a 75 ohm ZHL-1010. Plus a spare ZBSF-95 FM trap and some RF limiters. I don't really need a multicoupler at this time but I can mount a ZHL-1010 and the 10MHz to 1GHz 8-way divider to a small aluminum plate with an RF limiter and FM trap in front of the amp and maybe make it available to people for testing to see if the design works ok in their area.

View attachment 158873

Hey if you build it I'm 1000 ft ASL between a County/State site and a commercial site. I'll give it a whirl.

 

[prcguy]

As threatened I cobbled together a multicoupler from some parts I had on hand. Everything is mounted to an 8 X 8” aluminum plate with a MiniCircuits FM trap at the front end then an HP limiter to a MiniCircuits ZHL-1010 amplifier then 4-way divider. Overall gain is about 3dB over 50-1,000MHz and so far using an Icom R8600 for testing it just makes signals a tiny bit bigger with four equal output ports. The noise floor is about the same with no IMD or problems detected. It runs on 12v at about 450ma (!) and it’s using an 850ma rated linear wall wart I had in a junk box.

Total cost on this thing was under $200 with most parts coming from eBay. I think it will run circles around a Stridsberg costing similar. Noise figure is about the same as the Stridsberg, IP1 is about 9dB better and IP3 is about 14dB better. Plus the Stridsberg does not have an expensive 10w rated RF limiter in the front end or a world class FM trap filter. If all parts were purchased new I think this thing would run over $1k to build.

Homebrew rocks, let’s give Stridsberg something to worry about and build more of this stuff. BTW, check out the little toggle switch under the red LED. I bought a surplus rack panel from NASA around 1974 with a bunch of those switches on it and have used them on many projects over the last 50yrs and this was my very last switch. I don’t know who made them but they are the sexiest little switches I’ve ever seen. Wish I could find some more.

 

[Pape]

This is really nice.
I got something similar but I have put the coax in the middle therefore pushing the filter and preamp at the antenna reducing my total lost.
On the left we have the 8 way divider and the power injector, on the right we have the preamp and the FM trap.
This work pretty good for mostly cheap part but this is far from the final version.


P.S antenna is in the attic, no need for lightning arrestor.