I know that ambient noise drops as frequency increases. That is why we strive for ever lower noise figures in our preamps as we operate higher bands. What I am looking for is a chart, or graph that shows this noise level from about 30 MHz up. At this moment I am particularly interested in 50 MHz. The reason is I am putting a yagi for six meters out on the tower behind the house. I will have 100 feet of LMR 400 and 250 feet of 1/2 inch superflex between me and the antenna. I want to know if I need a preamp. I went through this exercise when I mounted the yagi at 50 feet right by the house and had only 75 feet of 1/2 inch hardline feeding it. It did no good to put a preamp at the antenna. I have been googling and evidently haven't used the proper terms because I don't get the results I need. Any link to this info would be greatly appreciated. Thanks & 73, Dave, K4TO

https://en.wikipedia.org/wiki/Radio_noise#/media/File:Atmosphericnoise.PNG On Tue, Jun 30, 2020 at 5:19 PM Dave Sublette via mvus-list < mvus-list@lists.febo.com> wrote: > I know that ambient noise drops as frequency increases. That is why we > strive for ever lower noise figures in our preamps as we operate higher > bands. > > What I am looking for is a chart, or graph that shows this noise level from > about 30 MHz up. > > At this moment I am particularly interested in 50 MHz. The reason is I am > putting a yagi for six meters out on the tower behind the house. I > will have 100 feet of LMR 400 and 250 feet of 1/2 inch superflex between me > and the antenna. I want to know if I need a preamp. > > I went through this exercise when I mounted the yagi at 50 feet right by > the house and had only 75 feet of 1/2 inch hardline feeding it. It did no > good to put a preamp at the antenna. > > I have been googling and evidently haven't used the proper terms because I > don't get the results I need. Any link to this info would be greatly > appreciated. > > Thanks & 73, > > Dave, K4TO > _______________________________________________ > mvus-list mailing list > mvus-list@lists.febo.com > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com > -- Trevor R.H. Clarke Computer Science House Rochester Institute of Technology retrev@csh.rit.edu http://www.csh.rit.edu/~retrev/

Thanks Trevor, I found that graph, but it stops at 30 MHz. In the meantime, I think I have answered my own question IF the info I found is correct. I found an article by a Dutch amateur that stated "the noise figure on 50 MHz is >6dB. " If this is true, then the noise figure of my receiver plus loss in the feedline can be as high as 6 dB and it won't do any good to put a preamp at the antenna. The total loss of 100 feet of LMR400 is .9 dB. The loss of 250 feet of 1/2" superflex is 1.825 dB. The sum of the two in 2.7 dB. My Rx front end is surely less than 3 dB (Elecraft K3s). So I don't think I need a preamp for my proposed installation. But it all hinges on the statement that the atmospheric terrestrial noise figure at 50 MHz is 6 dB. Anybody got any better number for this?? 73, Dave, K4TO On Tue, Jun 30, 2020 at 5:29 PM Trevor Clarke <retrev@csh.rit.edu> wrote: > https://en.wikipedia.org/wiki/Radio_noise#/media/File:Atmosphericnoise.PNG > > > On Tue, Jun 30, 2020 at 5:19 PM Dave Sublette via mvus-list < > mvus-list@lists.febo.com> wrote: > >> I know that ambient noise drops as frequency increases. That is why we >> strive for ever lower noise figures in our preamps as we operate higher >> bands. >> >> What I am looking for is a chart, or graph that shows this noise level >> from >> about 30 MHz up. >> >> At this moment I am particularly interested in 50 MHz. The reason is I am >> putting a yagi for six meters out on the tower behind the house. I >> will have 100 feet of LMR 400 and 250 feet of 1/2 inch superflex between >> me >> and the antenna. I want to know if I need a preamp. >> >> I went through this exercise when I mounted the yagi at 50 feet right by >> the house and had only 75 feet of 1/2 inch hardline feeding it. It did no >> good to put a preamp at the antenna. >> >> I have been googling and evidently haven't used the proper terms because I >> don't get the results I need. Any link to this info would be greatly >> appreciated. >> >> Thanks & 73, >> >> Dave, K4TO >> _______________________________________________ >> mvus-list mailing list >> mvus-list@lists.febo.com >> http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >> > > > -- > Trevor R.H. Clarke > Computer Science House > Rochester Institute of Technology > retrev@csh.rit.edu > http://www.csh.rit.edu/~retrev/ >

If you look carefully it extends to 40 so you can extrapolate a bit. I also found the graph I've used before and it does include 6m. I'm not sure what you're location is like so nf will vary. https://owenduffy.net/blog/wp-content/uploads/2016/01/Screenshot-10_01_16-09_49_56.png Trevor R.H. Clarke, K8TRC On Tue, Jun 30, 2020, 5:58 PM Dave Sublette <k4to.dave@gmail.com> wrote: > Thanks Trevor, > > I found that graph, but it stops at 30 MHz. In the meantime, I think I > have answered my own question IF the info I found is correct. > > I found an article by a Dutch amateur that stated "the noise figure on 50 > MHz is >6dB. " If this is true, then the noise figure of my receiver plus > loss in the feedline can be as high as 6 dB and it won't do any good to put > a preamp at the antenna. > > The total loss of 100 feet of LMR400 is .9 dB. The loss of 250 feet of > 1/2" superflex is 1.825 dB. The sum of the two in 2.7 dB. My Rx front end > is surely less than 3 dB (Elecraft K3s). So I don't think I need a preamp > for my proposed installation. > > But it all hinges on the statement that the atmospheric terrestrial noise > figure at 50 MHz is 6 dB. Anybody got any better number for this?? > > 73, > > Dave, K4TO > > On Tue, Jun 30, 2020 at 5:29 PM Trevor Clarke <retrev@csh.rit.edu> wrote: > >> https://en.wikipedia.org/wiki/Radio_noise#/media/File:Atmosphericnoise.PNG >> >> >> On Tue, Jun 30, 2020 at 5:19 PM Dave Sublette via mvus-list < >> mvus-list@lists.febo.com> wrote: >> >>> I know that ambient noise drops as frequency increases. That is why we >>> strive for ever lower noise figures in our preamps as we operate higher >>> bands. >>> >>> What I am looking for is a chart, or graph that shows this noise level >>> from >>> about 30 MHz up. >>> >>> At this moment I am particularly interested in 50 MHz. The reason is I >>> am >>> putting a yagi for six meters out on the tower behind the house. I >>> will have 100 feet of LMR 400 and 250 feet of 1/2 inch superflex between >>> me >>> and the antenna. I want to know if I need a preamp. >>> >>> I went through this exercise when I mounted the yagi at 50 feet right by >>> the house and had only 75 feet of 1/2 inch hardline feeding it. It did >>> no >>> good to put a preamp at the antenna. >>> >>> I have been googling and evidently haven't used the proper terms because >>> I >>> don't get the results I need. Any link to this info would be greatly >>> appreciated. >>> >>> Thanks & 73, >>> >>> Dave, K4TO >>> _______________________________________________ >>> mvus-list mailing list >>> mvus-list@lists.febo.com >>> http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >>> >> >> >> -- >> Trevor R.H. Clarke >> Computer Science House >> Rochester Institute of Technology >> retrev@csh.rit.edu >> http://www.csh.rit.edu/~retrev/ >> >

Dave, I think this is the same (or similar, I didn’t look closely) as the second chart Trevor posted from VK1OD. It’s in Reference Data for Radio Engineers, 7th ed. 73, —Ethan, K8GU. On Tuesday, June 30, 2020, Trevor Clarke via mvus-list < mvus-list@lists.febo.com> wrote: > If you look carefully it extends to 40 so you can extrapolate a bit. I also > found the graph I've used before and it does include 6m. I'm not sure what > you're location is like so nf will vary. > > https://owenduffy.net/blog/wp-content/uploads/2016/01/ > Screenshot-10_01_16-09_49_56.png > > Trevor R.H. Clarke, K8TRC > > On Tue, Jun 30, 2020, 5:58 PM Dave Sublette <k4to.dave@gmail.com> wrote: > > > Thanks Trevor, > > > > I found that graph, but it stops at 30 MHz. In the meantime, I think I > > have answered my own question IF the info I found is correct. > > > > I found an article by a Dutch amateur that stated "the noise figure on 50 > > MHz is >6dB. " If this is true, then the noise figure of my receiver > plus > > loss in the feedline can be as high as 6 dB and it won't do any good to > put > > a preamp at the antenna. > > > > The total loss of 100 feet of LMR400 is .9 dB. The loss of 250 feet of > > 1/2" superflex is 1.825 dB. The sum of the two in 2.7 dB. My Rx front > end > > is surely less than 3 dB (Elecraft K3s). So I don't think I need a > preamp > > for my proposed installation. > > > > But it all hinges on the statement that the atmospheric terrestrial noise > > figure at 50 MHz is 6 dB. Anybody got any better number for this?? > > > > 73, > > > > Dave, K4TO > > > > On Tue, Jun 30, 2020 at 5:29 PM Trevor Clarke <retrev@csh.rit.edu> > wrote: > > > >> https://en.wikipedia.org/wiki/Radio_noise#/media/File: > Atmosphericnoise.PNG > >> > >> > >> On Tue, Jun 30, 2020 at 5:19 PM Dave Sublette via mvus-list < > >> mvus-list@lists.febo.com> wrote: > >> > >>> I know that ambient noise drops as frequency increases. That is why we > >>> strive for ever lower noise figures in our preamps as we operate higher > >>> bands. > >>> > >>> What I am looking for is a chart, or graph that shows this noise level > >>> from > >>> about 30 MHz up. > >>> > >>> At this moment I am particularly interested in 50 MHz. The reason is I > >>> am > >>> putting a yagi for six meters out on the tower behind the house. I > >>> will have 100 feet of LMR 400 and 250 feet of 1/2 inch superflex > between > >>> me > >>> and the antenna. I want to know if I need a preamp. > >>> > >>> I went through this exercise when I mounted the yagi at 50 feet right > by > >>> the house and had only 75 feet of 1/2 inch hardline feeding it. It did > >>> no > >>> good to put a preamp at the antenna. > >>> > >>> I have been googling and evidently haven't used the proper terms > because > >>> I > >>> don't get the results I need. Any link to this info would be greatly > >>> appreciated. > >>> > >>> Thanks & 73, > >>> > >>> Dave, K4TO > >>> _______________________________________________ > >>> mvus-list mailing list > >>> mvus-list@lists.febo.com > >>> http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com > >>> > >> > >> > >> -- > >> Trevor R.H. Clarke > >> Computer Science House > >> Rochester Institute of Technology > >> retrev@csh.rit.edu > >> http://www.csh.rit.edu/~retrev/ > >> > > > _______________________________________________ > mvus-list mailing list > mvus-list@lists.febo.com > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com > -- http://www.k8gu.com/ Repair. Re-use. Re-purpose. Recycle.

Thanks again Trevor. This one shows maybe 8 dB at a quiet rural location, which I consider my QTH to be. That gives me even less reason to consider a preamp. I am waiting for the waterproofing compound to dry on my Oak blocks, to which are mounted the elements. But the element is sandwiched between two layers of plexiglass and bolted to an aluminum angle. The Oak blocks are just to raise the element away from the boom a bit more. It is my version of a Stauf clamp. I'm too cheap to buy the real ones. I got the mounting plate ready to go up on the side of the tower this afternoon. I plan to put it all up with one climb. I don't have enough stamina for more than one climb these days. 73, Dave, K4TO On Tue, Jun 30, 2020 at 6:11 PM Trevor Clarke via mvus-list < mvus-list@lists.febo.com> wrote: > If you look carefully it extends to 40 so you can extrapolate a bit. I also > found the graph I've used before and it does include 6m. I'm not sure what > you're location is like so nf will vary. > > > https://owenduffy.net/blog/wp-content/uploads/2016/01/Screenshot-10_01_16-09_49_56.png > > Trevor R.H. Clarke, K8TRC > > On Tue, Jun 30, 2020, 5:58 PM Dave Sublette <k4to.dave@gmail.com> wrote: > > > Thanks Trevor, > > > > I found that graph, but it stops at 30 MHz. In the meantime, I think I > > have answered my own question IF the info I found is correct. > > > > I found an article by a Dutch amateur that stated "the noise figure on 50 > > MHz is >6dB. " If this is true, then the noise figure of my receiver > plus > > loss in the feedline can be as high as 6 dB and it won't do any good to > put > > a preamp at the antenna. > > > > The total loss of 100 feet of LMR400 is .9 dB. The loss of 250 feet of > > 1/2" superflex is 1.825 dB. The sum of the two in 2.7 dB. My Rx front > end > > is surely less than 3 dB (Elecraft K3s). So I don't think I need a > preamp > > for my proposed installation. > > > > But it all hinges on the statement that the atmospheric terrestrial noise > > figure at 50 MHz is 6 dB. Anybody got any better number for this?? > > > > 73, > > > > Dave, K4TO > > > > On Tue, Jun 30, 2020 at 5:29 PM Trevor Clarke <retrev@csh.rit.edu> > wrote: > > > >> > https://en.wikipedia.org/wiki/Radio_noise#/media/File:Atmosphericnoise.PNG > >> > >> > >> On Tue, Jun 30, 2020 at 5:19 PM Dave Sublette via mvus-list < > >> mvus-list@lists.febo.com> wrote: > >> > >>> I know that ambient noise drops as frequency increases. That is why we > >>> strive for ever lower noise figures in our preamps as we operate higher > >>> bands. > >>> > >>> What I am looking for is a chart, or graph that shows this noise level > >>> from > >>> about 30 MHz up. > >>> > >>> At this moment I am particularly interested in 50 MHz. The reason is I > >>> am > >>> putting a yagi for six meters out on the tower behind the house. I > >>> will have 100 feet of LMR 400 and 250 feet of 1/2 inch superflex > between > >>> me > >>> and the antenna. I want to know if I need a preamp. > >>> > >>> I went through this exercise when I mounted the yagi at 50 feet right > by > >>> the house and had only 75 feet of 1/2 inch hardline feeding it. It did > >>> no > >>> good to put a preamp at the antenna. > >>> > >>> I have been googling and evidently haven't used the proper terms > because > >>> I > >>> don't get the results I need. Any link to this info would be greatly > >>> appreciated. > >>> > >>> Thanks & 73, > >>> > >>> Dave, K4TO > >>> _______________________________________________ > >>> mvus-list mailing list > >>> mvus-list@lists.febo.com > >>> http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com > >>> > >> > >> > >> -- > >> Trevor R.H. Clarke > >> Computer Science House > >> Rochester Institute of Technology > >> retrev@csh.rit.edu > >> http://www.csh.rit.edu/~retrev/ > >> > > > _______________________________________________ > mvus-list mailing list > mvus-list@lists.febo.com > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >

I have that book. I will go look for it. It is a different chart, but similar in layout. Thanks, Dave On Tue, Jun 30, 2020 at 6:28 PM Ethan Miller K8GU via mvus-list < mvus-list@lists.febo.com> wrote: > Dave, > > I think this is the same (or similar, I didn’t look closely) as the second > chart Trevor posted from VK1OD. It’s in Reference Data for Radio > Engineers, 7th ed. > > 73, > > —Ethan, K8GU. > > On Tuesday, June 30, 2020, Trevor Clarke via mvus-list < > mvus-list@lists.febo.com> wrote: > > > If you look carefully it extends to 40 so you can extrapolate a bit. I > also > > found the graph I've used before and it does include 6m. I'm not sure > what > > you're location is like so nf will vary. > > > > https://owenduffy.net/blog/wp-content/uploads/2016/01/ > > Screenshot-10_01_16-09_49_56.png > > > > Trevor R.H. Clarke, K8TRC > > > > On Tue, Jun 30, 2020, 5:58 PM Dave Sublette <k4to.dave@gmail.com> wrote: > > > > > Thanks Trevor, > > > > > > I found that graph, but it stops at 30 MHz. In the meantime, I think I > > > have answered my own question IF the info I found is correct. > > > > > > I found an article by a Dutch amateur that stated "the noise figure on > 50 > > > MHz is >6dB. " If this is true, then the noise figure of my receiver > > plus > > > loss in the feedline can be as high as 6 dB and it won't do any good to > > put > > > a preamp at the antenna. > > > > > > The total loss of 100 feet of LMR400 is .9 dB. The loss of 250 feet of > > > 1/2" superflex is 1.825 dB. The sum of the two in 2.7 dB. My Rx front > > end > > > is surely less than 3 dB (Elecraft K3s). So I don't think I need a > > preamp > > > for my proposed installation. > > > > > > But it all hinges on the statement that the atmospheric terrestrial > noise > > > figure at 50 MHz is 6 dB. Anybody got any better number for this?? > > > > > > 73, > > > > > > Dave, K4TO > > > > > > On Tue, Jun 30, 2020 at 5:29 PM Trevor Clarke <retrev@csh.rit.edu> > > wrote: > > > > > >> https://en.wikipedia.org/wiki/Radio_noise#/media/File: > > Atmosphericnoise.PNG > > >> > > >> > > >> On Tue, Jun 30, 2020 at 5:19 PM Dave Sublette via mvus-list < > > >> mvus-list@lists.febo.com> wrote: > > >> > > >>> I know that ambient noise drops as frequency increases. That is why > we > > >>> strive for ever lower noise figures in our preamps as we operate > higher > > >>> bands. > > >>> > > >>> What I am looking for is a chart, or graph that shows this noise > level > > >>> from > > >>> about 30 MHz up. > > >>> > > >>> At this moment I am particularly interested in 50 MHz. The reason > is I > > >>> am > > >>> putting a yagi for six meters out on the tower behind the house. I > > >>> will have 100 feet of LMR 400 and 250 feet of 1/2 inch superflex > > between > > >>> me > > >>> and the antenna. I want to know if I need a preamp. > > >>> > > >>> I went through this exercise when I mounted the yagi at 50 feet right > > by > > >>> the house and had only 75 feet of 1/2 inch hardline feeding it. It > did > > >>> no > > >>> good to put a preamp at the antenna. > > >>> > > >>> I have been googling and evidently haven't used the proper terms > > because > > >>> I > > >>> don't get the results I need. Any link to this info would be greatly > > >>> appreciated. > > >>> > > >>> Thanks & 73, > > >>> > > >>> Dave, K4TO > > >>> _______________________________________________ > > >>> mvus-list mailing list > > >>> mvus-list@lists.febo.com > > >>> http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com > > >>> > > >> > > >> > > >> -- > > >> Trevor R.H. Clarke > > >> Computer Science House > > >> Rochester Institute of Technology > > >> retrev@csh.rit.edu > > >> http://www.csh.rit.edu/~retrev/ > > >> > > > > > _______________________________________________ > > mvus-list mailing list > > mvus-list@lists.febo.com > > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com > > > > > -- > http://www.k8gu.com/ > Repair. Re-use. Re-purpose. Recycle. > _______________________________________________ > mvus-list mailing list > mvus-list@lists.febo.com > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >

I suspect the 6dB everyone seems to have is meant to be a lower limit so probably a good figure to use for this sort of question Trevor R.H. Clarke, K8TRC On Tue, Jun 30, 2020, 6:29 PM Dave Sublette via mvus-list < mvus-list@lists.febo.com> wrote: > Thanks again Trevor. This one shows maybe 8 dB at a quiet rural location, > which I consider my QTH to be. That gives me even less reason to consider > a preamp. > I am waiting for the waterproofing compound to dry on my Oak blocks, to > which are mounted the elements. But the element is sandwiched between two > layers of plexiglass and bolted to an aluminum angle. The Oak blocks are > just to raise the element away from the boom a bit more. It is my version > of a Stauf clamp. I'm too cheap to buy the real ones. I got the mounting > plate ready to go up on the side of the tower this afternoon. I plan to put > it all up with one climb. I don't have enough stamina for more than one > climb these days. > > 73, > > Dave, K4TO > > On Tue, Jun 30, 2020 at 6:11 PM Trevor Clarke via mvus-list < > mvus-list@lists.febo.com> wrote: > > > If you look carefully it extends to 40 so you can extrapolate a bit. I > also > > found the graph I've used before and it does include 6m. I'm not sure > what > > you're location is like so nf will vary. > > > > > > > https://owenduffy.net/blog/wp-content/uploads/2016/01/Screenshot-10_01_16-09_49_56.png > > > > Trevor R.H. Clarke, K8TRC > > > > On Tue, Jun 30, 2020, 5:58 PM Dave Sublette <k4to.dave@gmail.com> wrote: > > > > > Thanks Trevor, > > > > > > I found that graph, but it stops at 30 MHz. In the meantime, I think I > > > have answered my own question IF the info I found is correct. > > > > > > I found an article by a Dutch amateur that stated "the noise figure on > 50 > > > MHz is >6dB. " If this is true, then the noise figure of my receiver > > plus > > > loss in the feedline can be as high as 6 dB and it won't do any good to > > put > > > a preamp at the antenna. > > > > > > The total loss of 100 feet of LMR400 is .9 dB. The loss of 250 feet of > > > 1/2" superflex is 1.825 dB. The sum of the two in 2.7 dB. My Rx front > > end > > > is surely less than 3 dB (Elecraft K3s). So I don't think I need a > > preamp > > > for my proposed installation. > > > > > > But it all hinges on the statement that the atmospheric terrestrial > noise > > > figure at 50 MHz is 6 dB. Anybody got any better number for this?? > > > > > > 73, > > > > > > Dave, K4TO > > > > > > On Tue, Jun 30, 2020 at 5:29 PM Trevor Clarke <retrev@csh.rit.edu> > > wrote: > > > > > >> > > > https://en.wikipedia.org/wiki/Radio_noise#/media/File:Atmosphericnoise.PNG > > >> > > >> > > >> On Tue, Jun 30, 2020 at 5:19 PM Dave Sublette via mvus-list < > > >> mvus-list@lists.febo.com> wrote: > > >> > > >>> I know that ambient noise drops as frequency increases. That is why > we > > >>> strive for ever lower noise figures in our preamps as we operate > higher > > >>> bands. > > >>> > > >>> What I am looking for is a chart, or graph that shows this noise > level > > >>> from > > >>> about 30 MHz up. > > >>> > > >>> At this moment I am particularly interested in 50 MHz. The reason > is I > > >>> am > > >>> putting a yagi for six meters out on the tower behind the house. I > > >>> will have 100 feet of LMR 400 and 250 feet of 1/2 inch superflex > > between > > >>> me > > >>> and the antenna. I want to know if I need a preamp. > > >>> > > >>> I went through this exercise when I mounted the yagi at 50 feet right > > by > > >>> the house and had only 75 feet of 1/2 inch hardline feeding it. It > did > > >>> no > > >>> good to put a preamp at the antenna. > > >>> > > >>> I have been googling and evidently haven't used the proper terms > > because > > >>> I > > >>> don't get the results I need. Any link to this info would be greatly > > >>> appreciated. > > >>> > > >>> Thanks & 73, > > >>> > > >>> Dave, K4TO > > >>> _______________________________________________ > > >>> mvus-list mailing list > > >>> mvus-list@lists.febo.com > > >>> http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com > > >>> > > >> > > >> > > >> -- > > >> Trevor R.H. Clarke > > >> Computer Science House > > >> Rochester Institute of Technology > > >> retrev@csh.rit.edu > > >> http://www.csh.rit.edu/~retrev/ > > >> > > > > > _______________________________________________ > > mvus-list mailing list > > mvus-list@lists.febo.com > > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com > > > _______________________________________________ > mvus-list mailing list > mvus-list@lists.febo.com > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >

Good point. On Tue, Jun 30, 2020 at 6:38 PM Trevor Clarke <retrev@csh.rit.edu> wrote: > I suspect the 6dB everyone seems to have is meant to be a lower limit so > probably a good figure to use for this sort of question > > Trevor R.H. Clarke, K8TRC > > On Tue, Jun 30, 2020, 6:29 PM Dave Sublette via mvus-list < > mvus-list@lists.febo.com> wrote: > >> Thanks again Trevor. This one shows maybe 8 dB at a quiet rural location, >> which I consider my QTH to be. That gives me even less reason to consider >> a preamp. >> I am waiting for the waterproofing compound to dry on my Oak blocks, to >> which are mounted the elements. But the element is sandwiched between two >> layers of plexiglass and bolted to an aluminum angle. The Oak blocks are >> just to raise the element away from the boom a bit more. It is my version >> of a Stauf clamp. I'm too cheap to buy the real ones. I got the mounting >> plate ready to go up on the side of the tower this afternoon. I plan to >> put >> it all up with one climb. I don't have enough stamina for more than one >> climb these days. >> >> 73, >> >> Dave, K4TO >> >> On Tue, Jun 30, 2020 at 6:11 PM Trevor Clarke via mvus-list < >> mvus-list@lists.febo.com> wrote: >> >> > If you look carefully it extends to 40 so you can extrapolate a bit. I >> also >> > found the graph I've used before and it does include 6m. I'm not sure >> what >> > you're location is like so nf will vary. >> > >> > >> > >> https://owenduffy.net/blog/wp-content/uploads/2016/01/Screenshot-10_01_16-09_49_56.png >> > >> > Trevor R.H. Clarke, K8TRC >> > >> > On Tue, Jun 30, 2020, 5:58 PM Dave Sublette <k4to.dave@gmail.com> >> wrote: >> > >> > > Thanks Trevor, >> > > >> > > I found that graph, but it stops at 30 MHz. In the meantime, I think >> I >> > > have answered my own question IF the info I found is correct. >> > > >> > > I found an article by a Dutch amateur that stated "the noise figure >> on 50 >> > > MHz is >6dB. " If this is true, then the noise figure of my receiver >> > plus >> > > loss in the feedline can be as high as 6 dB and it won't do any good >> to >> > put >> > > a preamp at the antenna. >> > > >> > > The total loss of 100 feet of LMR400 is .9 dB. The loss of 250 feet >> of >> > > 1/2" superflex is 1.825 dB. The sum of the two in 2.7 dB. My Rx >> front >> > end >> > > is surely less than 3 dB (Elecraft K3s). So I don't think I need a >> > preamp >> > > for my proposed installation. >> > > >> > > But it all hinges on the statement that the atmospheric terrestrial >> noise >> > > figure at 50 MHz is 6 dB. Anybody got any better number for this?? >> > > >> > > 73, >> > > >> > > Dave, K4TO >> > > >> > > On Tue, Jun 30, 2020 at 5:29 PM Trevor Clarke <retrev@csh.rit.edu> >> > wrote: >> > > >> > >> >> > >> https://en.wikipedia.org/wiki/Radio_noise#/media/File:Atmosphericnoise.PNG >> > >> >> > >> >> > >> On Tue, Jun 30, 2020 at 5:19 PM Dave Sublette via mvus-list < >> > >> mvus-list@lists.febo.com> wrote: >> > >> >> > >>> I know that ambient noise drops as frequency increases. That is >> why we >> > >>> strive for ever lower noise figures in our preamps as we operate >> higher >> > >>> bands. >> > >>> >> > >>> What I am looking for is a chart, or graph that shows this noise >> level >> > >>> from >> > >>> about 30 MHz up. >> > >>> >> > >>> At this moment I am particularly interested in 50 MHz. The reason >> is I >> > >>> am >> > >>> putting a yagi for six meters out on the tower behind the house. I >> > >>> will have 100 feet of LMR 400 and 250 feet of 1/2 inch superflex >> > between >> > >>> me >> > >>> and the antenna. I want to know if I need a preamp. >> > >>> >> > >>> I went through this exercise when I mounted the yagi at 50 feet >> right >> > by >> > >>> the house and had only 75 feet of 1/2 inch hardline feeding it. It >> did >> > >>> no >> > >>> good to put a preamp at the antenna. >> > >>> >> > >>> I have been googling and evidently haven't used the proper terms >> > because >> > >>> I >> > >>> don't get the results I need. Any link to this info would be >> greatly >> > >>> appreciated. >> > >>> >> > >>> Thanks & 73, >> > >>> >> > >>> Dave, K4TO >> > >>> _______________________________________________ >> > >>> mvus-list mailing list >> > >>> mvus-list@lists.febo.com >> > >>> http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >> > >>> >> > >> >> > >> >> > >> -- >> > >> Trevor R.H. Clarke >> > >> Computer Science House >> > >> Rochester Institute of Technology >> > >> retrev@csh.rit.edu >> > >> http://www.csh.rit.edu/~retrev/ >> > >> >> > > >> > _______________________________________________ >> > mvus-list mailing list >> > mvus-list@lists.febo.com >> > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >> > >> _______________________________________________ >> mvus-list mailing list >> mvus-list@lists.febo.com >> http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >> >

I found an RSGB publication on my shelf entitled "Amateur Radio Astronomy". It is stated that on 50 Mhz a system noise figure lower than 3 dB is not necessary. This sort of muddies the waters as my feedline loss is almost 3 dB. I may have to put one out there just to compare. :-) Dave, K4TO On Tue, Jun 30, 2020 at 6:43 PM Dave Sublette <k4to.dave@gmail.com> wrote: > Good point. > > On Tue, Jun 30, 2020 at 6:38 PM Trevor Clarke <retrev@csh.rit.edu> wrote: > >> I suspect the 6dB everyone seems to have is meant to be a lower limit so >> probably a good figure to use for this sort of question >> >> Trevor R.H. Clarke, K8TRC >> >> On Tue, Jun 30, 2020, 6:29 PM Dave Sublette via mvus-list < >> mvus-list@lists.febo.com> wrote: >> >>> Thanks again Trevor. This one shows maybe 8 dB at a quiet rural >>> location, >>> which I consider my QTH to be. That gives me even less reason to >>> consider >>> a preamp. >>> I am waiting for the waterproofing compound to dry on my Oak blocks, to >>> which are mounted the elements. But the element is sandwiched between >>> two >>> layers of plexiglass and bolted to an aluminum angle. The Oak blocks are >>> just to raise the element away from the boom a bit more. It is my >>> version >>> of a Stauf clamp. I'm too cheap to buy the real ones. I got the >>> mounting >>> plate ready to go up on the side of the tower this afternoon. I plan to >>> put >>> it all up with one climb. I don't have enough stamina for more than one >>> climb these days. >>> >>> 73, >>> >>> Dave, K4TO >>> >>> On Tue, Jun 30, 2020 at 6:11 PM Trevor Clarke via mvus-list < >>> mvus-list@lists.febo.com> wrote: >>> >>> > If you look carefully it extends to 40 so you can extrapolate a bit. I >>> also >>> > found the graph I've used before and it does include 6m. I'm not sure >>> what >>> > you're location is like so nf will vary. >>> > >>> > >>> > >>> https://owenduffy.net/blog/wp-content/uploads/2016/01/Screenshot-10_01_16-09_49_56.png >>> > >>> > Trevor R.H. Clarke, K8TRC >>> > >>> > On Tue, Jun 30, 2020, 5:58 PM Dave Sublette <k4to.dave@gmail.com> >>> wrote: >>> > >>> > > Thanks Trevor, >>> > > >>> > > I found that graph, but it stops at 30 MHz. In the meantime, I >>> think I >>> > > have answered my own question IF the info I found is correct. >>> > > >>> > > I found an article by a Dutch amateur that stated "the noise figure >>> on 50 >>> > > MHz is >6dB. " If this is true, then the noise figure of my receiver >>> > plus >>> > > loss in the feedline can be as high as 6 dB and it won't do any good >>> to >>> > put >>> > > a preamp at the antenna. >>> > > >>> > > The total loss of 100 feet of LMR400 is .9 dB. The loss of 250 feet >>> of >>> > > 1/2" superflex is 1.825 dB. The sum of the two in 2.7 dB. My Rx >>> front >>> > end >>> > > is surely less than 3 dB (Elecraft K3s). So I don't think I need a >>> > preamp >>> > > for my proposed installation. >>> > > >>> > > But it all hinges on the statement that the atmospheric terrestrial >>> noise >>> > > figure at 50 MHz is 6 dB. Anybody got any better number for this?? >>> > > >>> > > 73, >>> > > >>> > > Dave, K4TO >>> > > >>> > > On Tue, Jun 30, 2020 at 5:29 PM Trevor Clarke <retrev@csh.rit.edu> >>> > wrote: >>> > > >>> > >> >>> > >>> https://en.wikipedia.org/wiki/Radio_noise#/media/File:Atmosphericnoise.PNG >>> > >> >>> > >> >>> > >> On Tue, Jun 30, 2020 at 5:19 PM Dave Sublette via mvus-list < >>> > >> mvus-list@lists.febo.com> wrote: >>> > >> >>> > >>> I know that ambient noise drops as frequency increases. That is >>> why we >>> > >>> strive for ever lower noise figures in our preamps as we operate >>> higher >>> > >>> bands. >>> > >>> >>> > >>> What I am looking for is a chart, or graph that shows this noise >>> level >>> > >>> from >>> > >>> about 30 MHz up. >>> > >>> >>> > >>> At this moment I am particularly interested in 50 MHz. The reason >>> is I >>> > >>> am >>> > >>> putting a yagi for six meters out on the tower behind the house. I >>> > >>> will have 100 feet of LMR 400 and 250 feet of 1/2 inch superflex >>> > between >>> > >>> me >>> > >>> and the antenna. I want to know if I need a preamp. >>> > >>> >>> > >>> I went through this exercise when I mounted the yagi at 50 feet >>> right >>> > by >>> > >>> the house and had only 75 feet of 1/2 inch hardline feeding it. >>> It did >>> > >>> no >>> > >>> good to put a preamp at the antenna. >>> > >>> >>> > >>> I have been googling and evidently haven't used the proper terms >>> > because >>> > >>> I >>> > >>> don't get the results I need. Any link to this info would be >>> greatly >>> > >>> appreciated. >>> > >>> >>> > >>> Thanks & 73, >>> > >>> >>> > >>> Dave, K4TO >>> > >>> _______________________________________________ >>> > >>> mvus-list mailing list >>> > >>> mvus-list@lists.febo.com >>> > >>> http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >>> > >>> >>> > >> >>> > >> >>> > >> -- >>> > >> Trevor R.H. Clarke >>> > >> Computer Science House >>> > >> Rochester Institute of Technology >>> > >> retrev@csh.rit.edu >>> > >> http://www.csh.rit.edu/~retrev/ >>> > >> >>> > > >>> > _______________________________________________ >>> > mvus-list mailing list >>> > mvus-list@lists.febo.com >>> > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >>> > >>> _______________________________________________ >>> mvus-list mailing list >>> mvus-list@lists.febo.com >>> http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >>> >>