Deployment ICOM radio project
 

I have been tasked with setting up an ICOM radio system where I am currently deployed. I have some components, but not all of them.

I have 4 IC-FR3000 repeaters. They came with duplexers, but no instructions on how to use them. The duplexer is labeled with a TX value: 150,000, RX: 155,000. there are 3 n style connectors on the duplexers which are labeled low pass, antenna, and high pass. the back of the duplexer has 6 screws on it to connect wires to.

Question 1) How do I set up this duplexer effectively? I have no knowledge in this area, and having little luck with general internet research.

The repeaters did not come with antennas. The instructions for the unit say that the unit uses a 50 ohm antenna...real specific haha. Will an antenna (such as a jungle) using 50 ohm wire for the transmission line fulfill that need? For now, the radios need to cover about 5 square km, maybe further (40 km) in the future. I think an omni-directional antenna would work well here, initially for testing I will be using jungle antennas.

Question 2) What makes a jungle antenna a 50 ohm antenna? I read on electronics tutorials.com that the 45 degree down angle creates an artificial ground leading to an impedence of 50 ohms...but I don't understand how that works!

Question 3) Does anyone know what the corresponding default frequencies from the factory on a 16 channel ICOM F11 model are? No luck on researching that one so far. The radios did not come with programming cables/software, so I have to order those. The only thing I can think to do for now is plug in frequencies to an MBITR to see if i can talk to the icom.

Thanks to anyone who can help!

I am going to try an address some of your questions. Some of my answers are not very helpful I realized after typing them up, but could send you in a direction to find more answers. I am trying to pull up some documentation on your equipment and see what I can figure out about it. Do the duplexer's have a IC-xxxx model number?


Without seeing the Duplexer configuration, I can tell you that the antenna connection obviously goes to the antenna, and the high and low pass connectors go to the receiving and transmitting radio. I am unsure about the 6 post-terminals you are referring too.


This duplexer as it is configured can only be used if you use the frequencies listed on it. It may work slightly outside of those values, but will work in a degraded manner, if at all. You can also bypass using the duplexer for the time being by using two separate antenna's, separated by a fair amount of physical distance, 10+ feet for a 5+ MHz spread. A duplexer filters out all but a specific range of frequencies so that you cannot overload one duplexer has band-passes that are specifically tuned for particular frequencies. Whether or not your are tunable by the user I do not know. Tuning them is also a rather complex and delicate task.



What the manual means is that the radio needs a 50ohm impedance on the transmitting antenna, and other than that your antenna choice is pretty much up to you. Any antenna that can handle 50 Watts (what your repeater puts out) would be suitable, as long as it is tuned relatively to frequency, and does not have an insane SWR. There are plenty of VHF antenna's you can choose from, or depending on you OE you could construct your own as well.


This is a complex question that delves into physics, the way electrons move on a wire, the way radio-waves interact in free space, and real space, etc. I suggest Google-Fu and maybe a couple ARRL books on the subject.


Without the spec's from Icom (try e-mailing them) your next easiest solution is a spectrum analyzer, key up the mic and hone in on the spike. I don't know where you are operating out of, but I would just mention that frequencies (EMSO)are managed by US forces as well as most host countries. Food for thought before you start "hi-jacking" frequencies. Also for repeater use, unless the radio's are pre-programmed with repeater offset channels instead of single channel simplex channels, those repeaters will not do you much good.


Erik

The six screws on the bottom of your duplexer (diplexer) are likely for mounting the unit. The only connections you need to concern yourself with are the N-type connectors; High-pass to transmit, low-pass to receive and the antenna is self-explanatory. No-Hertz, in his post was correct--you do not need to use the duplexer; just use two antennas. If you do, place one of the antennas above the other (at least three to six feet). If you place them side by side the two antennas will couple and you will have some serious interference problems.

I downloaded the manual from ICOM's technical support site, which also has email a phone contact information. PM me and I'll send you the link.

I downloaded the manual also and posted it to a site I own.

Here's the link: Manual

Here's the service manual: Service Manual

Replys
 

Thanks to all who have replied to this topic.

No-hertz, the model of the duplexer is IAS RDN 165A. I have a pic, but can't post...still need an admin to bless me off on QP status.

Thank you for the antenna advice...I will probably not use the duplexer's and set up two antenna's (plenty of speaker wire and 12 gauge copper wire laying around). Also, the service manual post was handy in case I do install the duplexers. I ran into an element here that has a spectrum analyzer, so I will be able to make some tests before my programming equipment comes. Thanks again for the help!

Update...
 

Was able to determine that the ICOMS come with a RX freq of 146.03 PT FM on channel 1 (factory), still trying to find the TX if someone could help that would be great! I talked with a guy that had a spectrum analyzer, who provided me with the freq...should have been the TX but its not working with an MBITR.

I am a little surprised by this. Most of those radios have a 25Khz step for analog and 12.5Khz step for digital if they have it.

146.03 seems weird to me. did you watch him do any of this, or did he just give you the info. Also, how do you know it is the RX freq, did you make one way commo, RX only?

have you tried transmitting from an MBITR, using different CTCSS tones? Some of those radio use tones by default as well, which is something you will not notice with a O-Scope. time consuming, but start at 67.0 and work your way up. I have a handy Yaesu VX-6R that will tone scan on it's own, but I imagine you don't have too many HAM radio's in your toolbox.

ICOM RX/TX
 

I am able to transmit from the MBITR to the ICOM on channel 1 at 146.03 MHz. This works in both FM and NB, and with any value entered in for CTCSS. I am yet unable to figure the freq/settings for RX from the ICOM to the MBITR. I am hoping this will be solved when I recieve the programming software/cables for the repeaters and individual ICOM RT's.

I am willing to try to make some antenna's that cover the 146-174 MHz range. I ordered a 5/8 wavelength TRAM antenna to see how it is constructed, hoping to learn a bit more about antenna theory and how to apply it a little bit further than the basics learned in the Q course. Does anyone have ideas/blueprints?

just out of curiosity have you tried 146.000 MHz?

I am still baffled that the carrier is on 146.03. obviously it is working for you, but just seems a rather odd center freq.

Baffling
 

Me too, especially since the specification in the manual (link above) state the bands of operation to be 148-172MHz or 150-174MHz depending on the version.

Have you tried contacting customer support?

Project Update
 

The programming software/cables have arrived for both the radios and repeaters. Upon reading the radios default channels, I determined that channels 1 - 3 were pre-programmed at the factory. Channel 1's freq was set to 146.03. The radios operate between 146-174 according to the manual...so while its an number, it does match what was determined by a spectrum analyzer. I set the CTCSS tone to 150.0, and as before I am able to talk from the MBITR to the ICOM. I still unable to talk from ICOM to MBITR. This will not stop the project in its tracks, but it would be nice to have the option to have two way coms with the locals...I will continue to investigate this side of the problem.

I had ordered one VHF antenna, but it has yet to arrive. A second antenna will be needed if a duplexor is not used, which I prefer not to in this situation. I dont want to limit traffic to one TX/RX freq if the locals decide to set up a "backup channel" structure.

I have constructed 2 100ft cables made of RG213, with N style connectors to terminate to the repeaters, and PL259 connectors on the opposite side to terminate into the antenna's SO239 connection.

Still hoping someone can provide a good blue-print for a antenna in the 146-174 range! Any takers?

I will give you a couple links to get you started, but if you Google "2m ham antenna" there will be thousands of different sets of plans and variations on them that all the HAM guys use on 2 meters. Only a small adjustment to get up to your frequencies. 2m is technically 150Mhz, but due to FCC band allocation, resides between 144-147.99 Mhz.

http://home.comcast.net/~buck0/hampage.htm

http://www.ac6v.com/antprojects.htm

Most of the time I end up picking the antenna based on my available construction material.

Just a note, I have a couple 2m copper tubing J-Poles I use at home for shooting the shit on local repeaters, seem to work well for me.

Thank you for the replies!
 

No-hertz, your last reply was very helpful. The links you provided have steered me right in the direction I was looking for...I have a small bit of ladder line, and constructed the ladder line j-pole with RG213 as the transmission line. A bit of tweaking got me to 1:1.4 SWR...not bad for a 100ft transmission line (Eventually the antenna of choice will be going up in a radio tower). The solid copper wire 5/8 stack J-pole is my next project...just have to wait for the wire to arrive by mail and I'll be busy again. Thanks again for the help, this was exactly what I needed!!

glad to help out. I am active in amateur radio (when home) and probably the most enjoyable part for me is making antenna's, getting them working well, and just tinkering to stretch those watts a few more miles.

out of curiosity what are you using to measure your SWR, a field meter with a pass through style or an antenna analyzer ala MFJ-269 style?

SWR meter
 

I am using the MFJ-259B, kinda wishing I would have sprung for the 269 in case I start working with higher freqs!