How to build a repeater for beginners.

[shevo7385]

Hello everyone and thank you for taking the time to read this question and answer it. I do realize that this may be a heavily asked question; however, I am hoping to make the answer more efficient and richer in data so others who find themselves to a similar position may have answers or at least a direction to go in. I am relatively new to the GMRS world and even newer to the repeater side of things so my knowledge is severely limited, at best. Using the forum here to gather information on the topic I found that a simple basic repeater system is composed of the following:

1.     Dual-use or Omni antenna for transmitting (TX) and receiving (RX) signals.

2.     Feedline or Hardline to connect the antenna to the duplexer.

3.     Duplexer

4.     Receiver

5.     Repeater

6.     Transmitter

For a visual representation of this system, a great visual will be used from www.repeater-builder.com listed as figure 1. Now that the basic premise of a repeater has been shared, along with my depth of knowledge on the subject, let me pose my question to the greater community: Looking at each of the six enumerated items above, what is a business that sells them (please include a link to their page) and what is the closest you can get to plug-and-play type of system (what model)? Ideally, in as simply a way as possible, how does one build a repeater from scratch without having to endlessly search Ebay or other sites for old transmitters/receivers. I would like to purchase new, with the ability to change my broadcasting power (not be stuck with 10w pre-made systems but rather make a 50w or greater system). Along with having a link to each of the numbered items showing a product and how to connect all of them. Think of this as setting up a computer for your parents who have never seen/used one. Explain here is the printer, it prints things you want and here is a hyperlink to brand X printers. It will use a USB cable to connect to the computer itself and here is a link for each of those. Then so on and so forth. Once all of the information has been gathered and collected, I will repost so it is a simple way to find information and resources to purchase. As of the current time I am looking at how to build the repeater and what it will take to make it work when I flip the switch and not the FCC document submissions…yet. Once the system is built, functioning, and I have made my measurements I then will submit all of the information to the FCC seeking permission to install and “open for business”. Thank you all for your help with this and look forward to all of the information!

< Figure 1 courtesy of www.repeater-builder.com

[Sshannon]

19 minutes ago, shevo7385 said:

Hello everyone and thank you for taking the time to read this question and answer it. I do realize that this may be a heavily asked question; however, I am hoping to make the answer more efficient and richer in data so others who find themselves to a similar position may have answers or at least a direction to go in. I am relatively new to the GMRS world and even newer to the repeater side of things so my knowledge is severely limited, at best. Using the forum here to gather information on the topic I found that a simple basic repeater system is composed of the following:

1.     Dual-use or Omni antenna for transmitting (TX) and receiving (RX) signals.

2.     Feedline or Hardline to connect the antenna to the duplexer.

3.     Duplexer

4.     Receiver

5.     Repeater

6.     Transmitter

For a visual representation of this system, a great visual will be used from www.repeater-builder.com listed as figure 1. Now that the basic premise of a repeater has been shared, along with my depth of knowledge on the subject, let me pose my question to the greater community: Looking at each of the six enumerated items above, what is a business that sells them (please include a link to their page) and what is the closest you can get to plug-and-play type of system (what model)? Ideally, in as simply a way as possible, how does one build a repeater from scratch without having to endlessly search Ebay or other sites for old transmitters/receivers. I would like to purchase new, with the ability to change my broadcasting power (not be stuck with 10w pre-made systems but rather make a 50w or greater system). Along with having a link to each of the numbered items showing a product and how to connect all of them. Think of this as setting up a computer for your parents who have never seen/used one. Explain here is the printer, it prints things you want and here is a hyperlink to brand X printers. It will use a USB cable to connect to the computer itself and here is a link for each of those. Then so on and so forth. Once all of the information has been gathered and collected, I will repost so it is a simple way to find information and resources to purchase. As of the current time I am looking at how to build the repeater and what it will take to make it work when I flip the switch and not the FCC document submissions…yet. Once the system is built, functioning, and I have made my measurements I then will submit all of the information to the FCC seeking permission to install and “open for business”. Thank you all for your help with this and look forward to all of the information!

< Figure 1 courtesy of www.repeater-builder.com

4, 5, and 6 are typically sold in a single box, called simply a repeater.  If you don’t want much power you can even buy a single box that includes the duplexer. The shopping area of this site has both types of repeaters. So would most commercial radio stores or online radio shops. 
Good luck!
 

[gortex2]

As @Sshannon said in mygmrs store there are examples of repeaters for sale. 

https://shop.mygmrs.com/collections/repeaters-and-accessories

You can also look at the Midland Package that just came out. Its very similar to the RT97 but in a KISS method. 

There is no licensing of a GMRS repeater with the FCC. Its covered under your license. Many folks list it on mygmrs.com but its up to you. Regardless of the repeater you need to manage expectations. Locations and antenna height are far more important than power. a RT97/Midland on a 5000' summit with a good antenna will talk miles further than a 50 watt mobile with an Ed Fong antenna on your garage. Repeaters are good tools when implemented properly but can be costly to do if your expectations are a 50 mile radius. My GMRS repeater at home gets about 10 miles on a mobile with a GR1225 (25 watts - 15 to antenna)/ DB404 and 10' of LDF4-50 Hardline. If I could get it up in the air I could get more but it covers my area I need to cover fine. 

[WRUU653]

Something else to consider for your list is a way to ID your repeater if you are going to make available for people outside of your immediate family. Something like a ID-O-Matic… 

[shevo7385]

Sshannon, gortex2, and WRUU653 I appreciate the feedback! So to sum up a few things and ask a few other questions.

1) There is zero requirement for filing further FCC paperwork because my license already covers repeater capability and it is my choice to list it and research proper frequency as to not disturb other systems, correct?

2) Provided I have excellent elevation, 10-15 mile line-of-sight range, and want to build a large and powerful system say 50 watts or greater, what would a good system be as far as each component I listed above in figure 1 showing the components of a repeater? I LOVE the KISS method and want this to be relatively as easy as possible. So for instance, antenna use this, duplexer use this, etc. (PS I hope this doesn’t come off as bossy or demanding in tone, I ask from a purely learning perspective and will use these answers as a great jump-off point!) I want to do this as proper as possible and want a good functioning system that I may set up and allow people to use in order to grow this whole community.

3) When you say ID-O-Matic, are you referring to the voice you hear at the top of the hour announce the station ID and the time?

4) Looking here at the shopping link, I found this system listed in the link. If I purchase this, what else would I need to make it work? I would need what kind of antenna? Also, just a regular coax cable to connect the two lines and that is it, it is ready to repeat signals? Lastly for this, I would have to research a frequency not interfering with another repeater and send that to this company to program it to, correct? https://shop.mygmrs.com/collections/repeaters-and-accessories/products/bridgecom-systems-bcr-40du-400-470-mhz-uhf-repeater-w-internal-duplexer

[Sshannon]

1. Yes, but you only have eight frequency pairs to choose from.

2. Yes, but you’re limited to no more than 50 watts.

3. Yes, or Morse Code, and it must also happen during long conversations and at the end. 
4. Here’s where I’m going to let others review what you listed. 

[gortex2]

The Bridgcom is one choice and if purchased from Mygmrs would most likely come programmed to what you want and ready to go out the door. You would then need decent cable and a good antenna. 

While you can build a repeater out of boxes normally its easier to buy a complete bult unit. I had linked some others in another post here.

 

Remember antenna cable and antenna is am important part of the system. You want the best shortest cable you can use and a good antenna. 

[shevo7385]

Gortex2, I looked at that other post and that was alot of good information you shared! So all that is left are two questions, what antenna would you use and what cable/hardline would you use? Thank you for all of your information so far!!

[gortex2]

I use Comscope/Andrews Hardline (LDF4-50A) for mine but many can't afford it. If you want ebay and other places short chunks go on sale randomly. Some have had OK luck with LMR400. Keep it short and make sure you seal all connections from water and it would be a good start. I run the DB404 at minimum on all my repeaters. The Laird FG series is a nice starter antenna if funds are short. I do carry one in my camp stuff for my camp repeater. 

[shevo7385]

Gortex2, awesome info! One last thing I am curious about, I see on the back of the BridgeCom 40 DU there is an antenna connection for receiving then a second connection for transmitting. The antenna you shared, DB404, appears to only have one cable connection (unless I am mistaken) so how do I go from one single connection on the antenna to the two respective ports on the repeater? Do you put a splitter on the cable or is there 2 connections on the antenna and the pictures/manual just don't show it? Thank you so much for your help! I will be running the BridgeCom, the LDF4-50A cable, & the DB404; however, I just was confused by the above question. 

[Sshannon]

7 minutes ago, shevo7385 said:

Gortex2, awesome info! One last thing I am curious about, I see on the back of the BridgeCom 40 DU there is an antenna connection for receiving then a second connection for transmitting. The antenna you shared, DB404, appears to only have one cable connection (unless I am mistaken) so how do I go from one single connection on the antenna to the two respective ports on the repeater? Do you put a splitter on the cable or is there 2 connections on the antenna and the pictures/manual just don't show it? Thank you so much for your help! I will be running the BridgeCom, the LDF4-50A cable, & the DB404; however, I just was confused by the above question. 

With a repeater you either have to have two antennas, separated by enough distance that the transmitted signal doesn’t overwhelm the receiver or you need a duplexer.  The transmit side goes into the transmit connector on the duplexer and the receive side of the duplexer runs to the receive connector in the repeater.  Then the antenna connector on the duplexer runs to the antenna.

The diagram you attached in your first post illustrates it.  Just remember that both the transmitter and receiver are in the same box.

[wayoverthere]

5 minutes ago, shevo7385 said:

Gortex2, awesome info! One last thing I am curious about, I see on the back of the BridgeCom 40 DU there is an antenna connection for receiving then a second connection for transmitting. The antenna you shared, DB404, appears to only have one cable connection (unless I am mistaken) so how do I go from one single connection on the antenna to the two respective ports on the repeater? Do you put a splitter on the cable or is there 2 connections on the antenna and the pictures/manual just don't show it? Thank you so much for your help! I will be running the BridgeCom, the LDF4-50A cable, & the DB404; however, I just was confused by the above question. 

This is where a duplexer comes into play. The low port goes to the transmitter connector, the high port to the receive connector, and the middle port to the antenna's one connector.

I won't guess if this one is good or bad, but here is an example for visual...

https://www.buytwowayradios.com/xlt-dp-gmrs-50.html

[shevo7385]

AHA!! So the duplexer was a separate device from the repeater I confused myself as I thought the duplexer was built into the repeater on mygmrs.com the BridgeCom 40du. I went to the manufacturer website and saw the duplexer and it all makes sense. Low to transmitter, high to receiver, and middle to antenna. Now it all makes sense. I will make another post to sum everything up into simple bullet points and ensure I have it down. Again, thank you everyone! This has been extremely helpful!

[Sshannon]

11 minutes ago, shevo7385 said:

AHA!! So the duplexer was a separate device from the repeater I confused myself as I thought the duplexer was built into the repeater on mygmrs.com the BridgeCom 40du. I went to the manufacturer website and saw the duplexer and it all makes sense. Low to transmitter, high to receiver, and middle to antenna. Now it all makes sense. I will make another post to sum everything up into simple bullet points and ensure I have it down. Again, thank you everyone! This has been extremely helpful!

The low power Retevis RT-97 and RT-97s both have an integral duplexer but for higher power a duplexer can be quite large. 

[wayoverthere]

31 minutes ago, shevo7385 said:

AHA!! So the duplexer was a separate device from the repeater I confused myself as I thought the duplexer was built into the repeater on mygmrs.com the BridgeCom 40du. I went to the manufacturer website and saw the duplexer and it all makes sense. Low to transmitter, high to receiver, and middle to antenna. Now it all makes sense. I will make another post to sum everything up into simple bullet points and ensure I have it down. Again, thank you everyone! This has been extremely helpful!

Depending on the type and the power it needs to handle, it CAN be built in, especially with UHF. The higher frequencies need less space compared to VHF, while higher power generally means larger in either case.

This thread has a look at the internals of the rt97:

https://forums.mygmrs.com/topic/3314-retevis-rt97-heat-dissipation/