helitim Posted October 11, 2016 Report Share Posted October 11, 2016 Flight, My new GTN 750 and 225 for Comm 2 have been an amazing addition. On a flight yesterday, the reception on the 750 was poor and the 225 pretty much unreadable from about 125 miles out at 4500 feet. Trying to pick up Oakland center from Marysville (just NE of SAC). The comm 1 antenna is on bottom and comm 2 on top. Tower said they received us loud and clear. It was only the planes reception that was an issue. I realize there are many factors that can affect transmission and reception but, does this seem normal to you? It just seems like in the past that I was able to communicate some rather long distances with the older radios. Tim Quote Link to comment Share on other sites More sharing options...
Bennett Posted October 11, 2016 Report Share Posted October 11, 2016 My two GTNs (750, 650) have been reliable without any transmission or reception problem over the last several years. Both of my comm antennas are on the top of the fuselage. Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
helitim Posted October 11, 2016 Author Report Share Posted October 11, 2016 But what is your approximate range without signal degradation? Quote Link to comment Share on other sites More sharing options...
larryb Posted October 11, 2016 Report Share Posted October 11, 2016 Center has many transmitters in different locations. Sometimes they use the wrong one by mistake. So it's hard to know how far you tried to talk. I would not worry unless it happens more often. 1 Quote Link to comment Share on other sites More sharing options...
helitim Posted October 11, 2016 Author Report Share Posted October 11, 2016 Larry, what you are saying is kind of how I feel. Not being used to the new equipment I'm simply not sure if this is considered acceptable. Thank you, Tim Quote Link to comment Share on other sites More sharing options...
larryb Posted October 11, 2016 Report Share Posted October 11, 2016 You could do another flight and try to call up a bunch of distant airport towers. At least with them you have a better idea of real range. I'm pretty sure I cannot talk 125 miles from 4000 feet though. Quote Link to comment Share on other sites More sharing options...
Marauder Posted October 11, 2016 Report Share Posted October 11, 2016 I have the 650/255B combo. The 650 uses the top antenna and the 255B uses the bottom. 125 miles is a long, long distance and I am not sure is reasonable to be able to transmit or receive that distance at that low altitude.I have the 255B with a bottom mounted antenna because I was having issues with the 650 not transmitting as far as my old Narco Mark 12D+. I replaced it with the 16W 255B and there is no doubt they can hear me.Sent from my iPad using Tapatalk Quote Link to comment Share on other sites More sharing options...
Piloto Posted October 11, 2016 Report Share Posted October 11, 2016 (edited) Line of sight distance to the horizon is approximately nm = √(h/.7). For range between two planes nm = (√(h1/.7))+(√(h2/.7)). h = height in feet For 12,000ft range is 131nm plus the range of the receiving end. When flying into TJIG I can contact San Juan Oceanic on VHF at HARDE (171nm) with my GNS 530AW (16 watts). But have to admit that the ATC towers are on 2,000ft mountains. Airliners at 40,000 can contact ATC at 250nm on VHF(20 watts). This is the range to the oceanic boundary were you switch to HF. The San Juan Oceanic North Boundary is at 240nm north. Height is the predominant limiting range factor. José Edited October 11, 2016 by Piloto 1 Quote Link to comment Share on other sites More sharing options...
TWinter Posted October 13, 2016 Report Share Posted October 13, 2016 Have faith in your GTN 750....Last year I was working with a New York controller (don't remember the distance) and we struggled transmitting and receiving with each other..In his most New Yorkish accent he told me over the air I had a "crappy radio" and he couldn't hear me..I had to laugh it off and replied something like, thanks, I'll check it out....He was the only ATC that complained my entire 900 mile trip. Maybe he was on his crappy radio.. It's all relative to conditions. I guess being busy NY ATC and I was just flying VFR w/ FF I was fortunate that he even bothered to keep working me Maybe wait and see how others hear you since it's a new to you GTN750. Just my .02 -Tom Quote Link to comment Share on other sites More sharing options...
chrisk Posted October 13, 2016 Report Share Posted October 13, 2016 Did you turn the auto squelch off by pressing the volume knob? It's not obvious if you didn't read the manual carefully Quote Link to comment Share on other sites More sharing options...
helitim Posted October 13, 2016 Author Report Share Posted October 13, 2016 (edited) Turns out it wasn't exactly the auto squelch but something very close. The volume on the 750 acts like a master volume over the 225. Apparently when you push in the volume knob. It also limits the 225's ability to be turned up. Sitting in the plane today without the engine running I noticed how low the volume was thru the overhead speaker and knew this wasn't right. Kept messing with knobs until I pressed the volume knob in on the 750 and the 225's volume control became active again. Maybe that is the auto squelch and I simply don't realize it. To say that I don't understand how or why that would be designed into a system is an understatement but, it seems to have fixed the problem, I think. Flew for 1.2 around the area and had no further problem. Will continue to monitor closely though. Edited October 13, 2016 by helitim Quote Link to comment Share on other sites More sharing options...
carusoam Posted October 13, 2016 Report Share Posted October 13, 2016 Sounds like they let you set the volumes separately to your liking, then pair them together for simplified adjustment down the road. Pairing them together before the proper individual adjustment seems to be a challenge. challenges of modern technology. Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Marauder Posted October 13, 2016 Report Share Posted October 13, 2016 Sounds like they let you set the volumes separately to your liking, then pair them together for simplified adjustment down the road. Pairing them together before the proper individual adjustment seems to be a challenge. challenges of modern technology. Best regards, -a- I will need to look into that. I have a GTN / 255 combination and I don't recall this in the manual. Sent from my iPad using Tapatalk Quote Link to comment Share on other sites More sharing options...
Jerry 5TJ Posted October 13, 2016 Report Share Posted October 13, 2016 On 10/10/2016 at 10:18 PM, Marauder said: ......not transmitting as far as my old Narco Mark 12D+. I replaced it with the 16W 255B and there is no doubt they can hear me. Maybe you should add one of these 50W amplifiers "to be sure." http://www.ebay.com/itm/390654866963?_mwBanner=1&redirect=mobile Quote Link to comment Share on other sites More sharing options...
Marauder Posted October 13, 2016 Report Share Posted October 13, 2016 Maybe you should add one of these 50W amplifiers "to be sure." http://www.ebay.com/itm/390654866963?_mwBanner=1&redirect=mobile If I did buy that, I would need to find a crusty old electrical engineer to wire it up for me. Know anyone? Sent from my iPad using Tapatalk Quote Link to comment Share on other sites More sharing options...
Jerry 5TJ Posted October 13, 2016 Report Share Posted October 13, 2016 While we're installing the amplifier let's get a better antenna for your F, too. https://www.tessco.com/products/displayProductInfo.do?sku=473513 Quote Link to comment Share on other sites More sharing options...
Marauder Posted October 13, 2016 Report Share Posted October 13, 2016 While we're installing the amplifier let's get a better antenna for your F, too.https://www.tessco.com/products/displayProductInfo.do?sku=473513 I was thinking more about this one:Sent from my iPad using Tapatalk Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.