srbecker Posted May 3, 2021 Report Share Posted May 3, 2021 Hello all. Its me again with probably another stupid question, but here it goes. Some buddies and I are looking to pitch in and build a budget friendly repeater, install it at my house and hope it reaches all of us. Most of us are within 8-9 miles from my house and I am pretty central to everyone. We are not looking for anything state of the art, but obviously want something that works. Here is the plan so far, but I need help modifying said plan. Repeater: Retevis RT97 (been told it is a decent repeater for personal/private use) Antenna: Need help Antenna Pole/mount: Need help Grounding plan: Need help Coax type: Need help The plan is to install a mast attached to the side of my chimney that will extend about 10' higher than my chimney. This would likely give me roughly 50' or so for my antenna. I will then run the coax and grounding line down the chimney and into the basement where the repeat will be. I will have the repeater plugged into an outlet that is on my generator switch so if power does go out, the repeater will boot back up after a minute. What I really need help with is choosing the type of coax cable, determining how to mount my antenna mast, which antenna to get and a WIRING DIAGRAM that shows all of this and how I should connect it. Any help/assistance is very much appreciated and your opinions are very much welcome as I am pretty new to GMRS. If this is a stupid idea, simply say so, I can handle the truth lol. Quote Link to comment Share on other sites More sharing options...
BoxCar Posted May 3, 2021 Report Share Posted May 3, 2021 The range for your installation is dependent on three factors, antenna height, surrounding terrain and power. Your antenna's propagation pattern is from the center of the antenna rather than the tip. With a short antenna, it makes little difference from where you measure the height from the ground. With longer antennas, the best result is if you measure from the antenna feed point to the ground. But all that is for naught if the terrain around your install is higher than the antenna. UHF radio waves don't bend around hills. srbecker 1 Quote Link to comment Share on other sites More sharing options...
srbecker Posted May 3, 2021 Author Report Share Posted May 3, 2021 Thank you BoxCar! I live in a pretty flat area of the country. There isn't much difference in elevation and no major hills like you would see in a mountainous or hilly area. The biggest obstacles for us are going to be foliage and infrastructure such as houses. Line of sight from my house to their houses don't even really have major buildings or sky scrapers, just housing and trees, so my hopes are that a decent height antenna running at 30-50 watts will reach 9-10 miles. Quote Link to comment Share on other sites More sharing options...
BoxCar Posted May 3, 2021 Report Share Posted May 3, 2021 The coax you choose is open to a lot of debate. It's safe to say that hard line, air core will have the best results, but then using a good foam filled coax will make the install less costly but incur slightly less power available at the antenna when comparing the two types. The radiation pattern from a vertical antenna can be visualized as a beach ball with the top and bottom of the ball indented. Increasing the gain of the antenna pushes up and down on the ball resulting in less energy being directed up and down but more toward the horizon. A 3 dB gain effectively increases the energy being radiated to double the input while 6 dB is a quadruple increase. I also recommend an antenna with radials as this ensures the antenna has a ground reference and sets where the "bottom" of the beach ball pattern is. The top of the ball is the antenna tip. In all cases, antenna height above ground is the primary factor for distance covered. srbecker 1 Quote Link to comment Share on other sites More sharing options...
mbrun Posted May 4, 2021 Report Share Posted May 4, 2021 I would advocate that you conduct simplex testing first to confirm you can communicate between your intended sites before investing in repeater specific gear. The results of those tests will be incredibly beneficial. If you achieve exceptional results doing simplex, then there is reasonable chance of success with a repeater.I have considered hosting a repeater on my property, but have not yet chosen to do so. Even though my elevation is good (at or above everyone else for miles) I know from testing I would still need to get my antenna well above the trees (perhaps 100-120 feet or more AGL) to achieve reliable repeater coverage out to 8-9 miles and be suitable for reliable use with an HT. My range limitation is mostly foliage density (i.e. the trees are my enemy). The cost of the tower to achieve that elevation detracts me from moving forward.If you are considering the Retevis repeater, it is only 5 watts, so your simplex testing would need to yield exceptional results using only 5 watts of power. I say exceptional, because the Retivis will not work as well as a simplex radio solution.For my testing, I opted for a HD fiber glass pushup mast and high-gain collinear antenna on top. It was suitable for testing, and has found itself now semi-permanently installed next to the house.Here is an image taken when i was doing my simplex testing. Top of antenna in this picture is 56’ AGL.Bottom line, if you can’t simplex between the intended sites from your desired antenna elevations, using the intended amount of power, there is zero chance of repeater success. So, my advise is to keep your expectations realistic, do your testing first so that when you do decide to invest in a repeater your expectation bubble will not burst.MichaelWRHS965KE8PLM Extreme and srbecker 1 1 Quote Link to comment Share on other sites More sharing options...
srbecker Posted May 4, 2021 Author Report Share Posted May 4, 2021 Well damn! No disrespect to anyone, but that answer makes the most sense to my simplistic mind yet lol. Fair enough. So, invest in a mobile unit that can double as a base, and a GOOD antenna setup is my new goal I guess. Worry about myself, not appeasing my friends lol Quote Link to comment Share on other sites More sharing options...
n4gix Posted May 4, 2021 Report Share Posted May 4, 2021 15 hours ago, mbrun said: If you are considering the Retevis repeater, it is only 5 watts, so your simplex testing would need to yield exceptional results using only 5 watts of power. I say exceptional, because the Retivis will not work as well as a simplex radio solution. The specs on the RT-97 cite 10 watts. From testing my own I've found that after going through the duplexer the power out is just a tiny bit over 6 watts. Quote Link to comment Share on other sites More sharing options...
mbrun Posted May 4, 2021 Report Share Posted May 4, 2021 The specs on the RT-97 cite 10 watts. From testing my own I've found that after going through the duplexer the power out is just a tiny bit over 6 watts.Agreed, but my understanding is that GMRS version is only 5.MichaelWRHS965KE8PLM Quote Link to comment Share on other sites More sharing options...
gortex2 Posted May 4, 2021 Report Share Posted May 4, 2021 Its really about antenna and line as has already mentioned. Power isn't necessarily the factor. If your only talking to the repeater on a 4 watt HT having a 50 watt repeater wont make it work better. In the LMR world we would "balance" repeaters all the time to get them close. Also as said above. Take a portable and hook it to your antenna system. If it doesn't work a repeater wont help. Quote Link to comment Share on other sites More sharing options...
MacJack Posted May 5, 2021 Report Share Posted May 5, 2021 SirBeck58, I like your dream and I did my personal repeater for $400 that is either 10 watt or 20 watt and can go as high as 50 watts but not worth it. Got a free hand me down GMRS commercial antenna a list price of 1K. All the advise from this guys on this post are my mentor and coaches and are giving you the best answers... I like trying doing Simplex with your buddy first. I use this program on the web by putting in the GPS locations for you and buddy with height of antenna will let you know if it will work or not. https://www.scadacore.com/tools/rf-path/rf-line-of-sight/ So with the above web base line of sight and your Simplex text will tell if you have a chance. Just so you know, I live in the mountains of Western NC and I get 8 miles with my repeater. If you past the above test, I will tell you what I use as a repeater and it is not RT-97 which looked good but I went for a commercial repeater which has a longer duty cycle and will not die. Quote Link to comment Share on other sites More sharing options...
OldRadioGuy Posted May 5, 2021 Report Share Posted May 5, 2021 MacJack is right. That "line of sight" tool is amazing and highly useful for site surveys. You can probably tolerate a grazing contact with the soil but not much more. My path to the repeater 15 miles from here shows that I am almost line of sight with just a glancing blow to a hill between here and there. It's so marginal it makes a definite difference whether I am upstairs or downstairs. Also, the antenna makes a difference. So it's a close call just like the tool says. Now if it would only shade all the areas that are LOS from my location. Probably have to pay extra for that feature. Vince Quote Link to comment Share on other sites More sharing options...
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