Posted: 3/5/2015 2:29:59 AM EDT
| I would like to be able to hit a 2m repeater that is 49 miles from me but there is a mountain in the way. The mountain is 3.5 miles from me and 500 feet taller then my location. Would this be possible with a beam antenna and/or more power or is that mountain just gonna make it impossible ? |
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It's possible... How high is the repeater? I have hit a repeater at over 50 miles with a 500 ft hill about 5 miles in front of me. Mag mount antenna and it worked at 5 watts. It is doable but I think it is very location dependent. The repeater had a decent antenna and was fairly high, but probably more than 500 feet below the hill in the way. I could hit another repeater farther away, over the same hill - probably closer to 100 miles with 50 watts.
It can be done but I believe it is dependent on local conditions - angles, etc. to get the knife edge diffraction to work. |
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Its probably doable.
I am in the mountains of NC and there is a mountain between me and 90% of the repeaters I work. Power gets it done. With 100w and a 7 db directional antenna I hit repeaters in TN with at least 3 5000+ foot ridges between it and me, and I am at 2400 feet. |
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It's possible... How high is the repeater? I have hit a repeater at over 50 miles with a 500 ft hill about 5 miles in front of me. Mag mount antenna and it worked at 5 watts. It is doable but I think it is very location dependent. The repeater had a decent antenna and was fairly high, but probably more than 500 feet below the hill in the way. I could hit another repeater farther away, over the same hill - probably closer to 100 miles with 50 watts. It can be done but I believe it is dependent on local conditions - angles, etc. to get the knife edge diffraction to work. Simplified knife edge diffraction path loss calculator here. |
Here is a plot of the terrain from me to the repeater from radio mobile. I don't know the height of the repeater antenna so I put in 75 meters. My antenna is 10 meters above ground. A friend of mine can reach this repeater from 70 miles away with 15 watts but he is in a very flat area. The goal is to reach my friend thru this repeater. |
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http://i1341.photobucket.com/albums/o742/mtbguy350/RM71D252663E40_6_zpsnznofuqu.gif Here is a plot of the terrain from me to the repeater from radio mobile. I don't know the height of the repeater antenna so I put in 75 meters. My antenna is 10 meters above ground. A friend of mine can reach this repeater from 70 miles away with 15 watts but he is in a very flat area. The goal is to reach my friend thru this repeater. What is the path loss according to radio mobile? |
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You should be able to hear the repeater then (in theory). Is that the case? Quoted:
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16.45 dB of obstruction, 137.56 dB total You should be able to hear the repeater then (in theory). Is that the case? Yes, I can hear the repeater. That is why I want to get into it. However since the obstruction is so close to me I'm trying to figure out if it is going to be possible. |
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Yes, I can hear the repeater. That is why I want to get into it. However since the obstruction is so close to me I'm trying to figure out if it is going to be possible. Quoted:
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16.45 dB of obstruction, 137.56 dB total You should be able to hear the repeater then (in theory). Is that the case? Yes, I can hear the repeater. That is why I want to get into it. However since the obstruction is so close to me I'm trying to figure out if it is going to be possible. If you can hear it, then with enough power/gain you can make it hear you. |
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About 130 air miles total, from about 3000' asl flanking a 6500' mtn range, over that range and across a valley to a repeater on the second mountain range over at 2000', in a mobile running 25W into a 5/8 2M antenna, driving 70 MPH. Done and repeatable, knife edge effect is pretty stable over a given path I think.
Your situation may or may not be doable or it may be doable seasonally, it depends. But I'm willing to bet that given enough antenna gain and/or power you can find a path. |
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This. What transceiver, feedline and antenna are you using right now? Quoted:
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If you can hear it, then with enough power/gain you can make it hear you. This. What transceiver, feedline and antenna are you using right now? A baofeng, and ten feet of 5 of rg58 going to a slim jim made my m9tax just hang from the wall in the living room lets me hear this repeater. I also have a home made slim jim which I did not test for swr (bec I don't have a meter yet) mounted about 25 feet above ground with lmr 400 running to it. I use the same 10 foot rg58 wire to connect the lmr to the baofeng. With that antenna the repeater is much more clear. |
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A baofeng, and ten feet of 5 of rg58 going to a slim jim made my m9tax just hang from the wall in the living room lets me hear this repeater. I also have a home made slim jim which I did not test for swr (bec I don't have a meter yet) mounted about 25 feet above ground with lmr 400 running to it. I use the same 10 foot rg58 wire to connect the lmr to the baofeng. With that antenna the repeater is much more clear. Quoted:
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If you can hear it, then with enough power/gain you can make it hear you. This. What transceiver, feedline and antenna are you using right now? A baofeng, and ten feet of 5 of rg58 going to a slim jim made my m9tax just hang from the wall in the living room lets me hear this repeater. I also have a home made slim jim which I did not test for swr (bec I don't have a meter yet) mounted about 25 feet above ground with lmr 400 running to it. I use the same 10 foot rg58 wire to connect the lmr to the baofeng. With that antenna the repeater is much more clear. So you're feeding a relatively low-gain, non-directional antenna with just a few watts of transmitter power. Upgrading to a 40-70 watt mobile rig and a small yagi would make a HUGE difference. |
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A baofeng, and ten feet of 5 of rg58 going to a slim jim made my m9tax just hang from the wall in the living room lets me hear this repeater. I also have a home made slim jim which I did not test for swr (bec I don't have a meter yet) mounted about 25 feet above ground with lmr 400 running to it. I use the same 10 foot rg58 wire to connect the lmr to the baofeng. With that antenna the repeater is much more clear. Quoted:
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If you can hear it, then with enough power/gain you can make it hear you. This. What transceiver, feedline and antenna are you using right now? A baofeng, and ten feet of 5 of rg58 going to a slim jim made my m9tax just hang from the wall in the living room lets me hear this repeater. I also have a home made slim jim which I did not test for swr (bec I don't have a meter yet) mounted about 25 feet above ground with lmr 400 running to it. I use the same 10 foot rg58 wire to connect the lmr to the baofeng. With that antenna the repeater is much more clear. You need to get the M9TAX slim jim hanging 20' up or so, outside of the house and try that. I tried a commercially made slim jim inside and I don't think it liked being next to the wall. Get it out in the clear and see how it works, even if for five minutes. Your home made antenna may be able to receive but not broadcast efficiently if not tuned. Using the M9TAX will let you know if the Baofeng can hit it or not. More power may be required. While I could get my 50+ mile repeater to work over the ridge, it was much clearer on 50 watts than 5 watts. |
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when you assemble the yagi, make sure you fix polarity correctly too-good luck!
FWIW: I was also given an 11 element (Cushcraft) 2m yagi. It's installed on the eave of the barn/shack with a RS Rotator and a Chain-link top section as it's mast. It works Really Well! |
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16.45 dB of obstruction, 137.56 dB total Quoted:
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What is the path loss according to radio mobile? 16.45 dB of obstruction, 137.56 dB total I assume that is from your location to the repeater? What is the calculated path loss from the repeater to your location? |
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I assume that is from your location to the repeater? What is the calculated path loss from the repeater to your location? Quoted:
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What is the path loss according to radio mobile? 16.45 dB of obstruction, 137.56 dB total I assume that is from your location to the repeater? What is the calculated path loss from the repeater to your location? Actually I posted the wrong numbers the correct path loss is 44.72 dB of obstruction, 166.21 dB total from me to the repeater. I didn't do the reverse, however I can hear the repeater. |
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Actually I posted the wrong numbers the correct path loss is 44.72 dB of obstruction, 166.21 dB total from me to the repeater. I didn't do the reverse, however I can hear the repeater. Please run the numbers both ways. If it's 138 dB from the repeater to you, but 166 dB from you to the repeater, you're going to need that yagi. |
Easy. Move to the top of the mountain! 
Is there a path around the mountain that you could reflect a signal from, using the yagi? Has anyone tried putting an antenna on an obstruction like this? I believe it would re-radiate the signal from your yagi. Could you get a mobile rig with cross-band repeat, and put it on the mountain? |
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Please run the numbers both ways. If it's 138 dB from the repeater to you, but 166 dB from you to the repeater, you're going to need that yagi. Quoted:
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Actually I posted the wrong numbers the correct path loss is 44.72 dB of obstruction, 166.21 dB total from me to the repeater. I didn't do the reverse, however I can hear the repeater. Please run the numbers both ways. If it's 138 dB from the repeater to you, but 166 dB from you to the repeater, you're going to need that yagi. From the tower to me it is almost the same: 45 dB of obstruction loss, 167 dB total |
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From the tower to me it is almost the same: 45 dB of obstruction loss, 167 dB total How many feet of rg-58 and lmr-400 on your end? If 167 dB is correct you're going to need every dB you can come up with. http://en.wikipedia.org/wiki/Link_budget |
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Please run the numbers both ways. If it's 138 dB from the repeater to you, but 166 dB from you to the repeater, you're going to need that yagi. Quoted:
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Actually I posted the wrong numbers the correct path loss is 44.72 dB of obstruction, 166.21 dB total from me to the repeater. I didn't do the reverse, however I can hear the repeater. Please run the numbers both ways. If it's 138 dB from the repeater to you, but 166 dB from you to the repeater, you're going to need that yagi. That's not possible, a path is a path it doesn't matter which direction. If OP can hear the repeater he should be able to transmit to it, unless it's running a high power transmitter. If it's running a high power transmitter, it's almost certainly using multiple receive sites so a directional antenna would likely not point at the transmitter. You also need to make sure you're using the correct tone for access. Take a drive sometime and get on the repeater and make sure it's working, and talk to people, they might have local info that would be helpful to you. As I mentioned before, the best path is quite possibly not over the mountain which the software is trying to calculate, but around it via reflections. |
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Success ! With the 10 element yagi and 75 watts I was able to have a qso with someone on this machine.
At first I could get into the machine but was unreadable. But then some hams started a conversation and while they were talking I kept adjusting the direction the beam was pointing until the S meter read the highest. When they were done talking I threw out my call and one of them responded. |
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Success ! With the 10 element yagi and 75 watts I was able to have a qso with someone on this machine. At first I could get into the machine but was unreadable. But then some hams started a conversation and while they were talking I kept adjusting the direction the beam was pointing until the S meter read the highest. When they were done talking I threw out my call and one of them responded. 
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