Interesting. No, there was no data with it. On Fri, Nov 22, 2019 at 12:00 PM Björn <[email protected]> wrote:
> The N for North is because the phase center offsets are not symmetrical. > With a convention to orient the antennas the same way the offset could be > corrected. > > /Björn > > Sent from my iPhone > > > On 22 Nov 2019, at 17:07, Bill Dailey <[email protected]> wrote: > > > > I would like to tag on to this. I have a large Leica L1 choke ring > antenna. It has an indicator for “N”. Not sure why. I placed it on the > roof without respect to directionality. I will rotate it with “N” facing > north in a month or so to see if there is any effect. > > > > Bill Dailey > > > > Negativity always wins the short game. But positivity wins the long > game. - Gary Vaynerchuk > > > > Don’t be easy to understand, > > Be impossible to misunderstand > > - Steve Sims > > > >> On Nov 21, 2019, at 6:00 PM, Dana Whitlow <[email protected]> > wrote: > >> > >> Most modern GPS receivers are very quiet even barefoot. So, one could > >> argue that one should > >> not have much more LNA gain in the antenna than required to make up for > >> feedline loss, which > >> should be easily calculable. While excess gain in the antenna can > improve > >> overall system noise > >> figure a small amount, it will degrade intermod performance, which is > >> likely to be a worse problem > >> than simple weak signals. It's likely that the cure is worse than the > >> disease, as my doctor likes to > >> say. > >> > >> Dana > >> > >> > >> > >>> On Thu, Nov 21, 2019 at 4:00 PM Taka Kamiya via time-nuts < > >>> [email protected]> wrote: > >>> > >>> So.... concensus is, 50dB gain antenna is too much gain, unless feed > line > >>> is too long, reception is poor, or there are other circumstances extra > gain > >>> is desired? > >>> > >>> --------------------------------------- > >>> (Mr.) Taka Kamiya > >>> KB4EMF / ex JF2DKG > >>> > >>> > >>> On Thursday, November 21, 2019, 3:00:14 PM EST, Bob kb8tq < > >>> [email protected]> wrote: > >>> > >>> Hi > >>> > >>> That is indeed the gotcha. Once you get past a certain amount of gain > in > >>> the > >>> preamp, the C/N levels don’t change enough to notice. Looking today vs > >>> looking > >>> tomorrow is unlikely to be of any help if you are after a fraction of a > >>> db. > >>> > >>> About the only way to check would be to fast switch an attenuator in > and > >>> out of > >>> the signal path. Watch things for a minute at one setting and then do > the > >>> same at > >>> another setting. Run for a while and log all the deltas. If you see a > >>> degradation of > >>> more than a few tenths of a db, you are getting towards the minimum > gain > >>> point. > >>> > >>> Indeed there are some receivers that have an AGC built in. *IF* your > >>> receiver has one > >>> and *IF* you can get at it, that would be a great way to work this out. > >>> Indeed anybody > >>> who makes it past both of those constraints has a pretty unique device. > >>> > >>> ==== > >>> > >>> Simple answer for a 50 db antenna is to put an attenuator in after the > DC > >>> has > >>> been eliminated from the circuit. It’s not idea, but it’s the best you > can > >>> do. Running > >>> a great big splitter is one great way to come up with attenuation ….. > >>> > >>> Bob > >>> > >>> > >>>>> On Nov 21, 2019, at 10:29 AM, John Ackermann N8UR <[email protected]> > wrote: > >>>> > >>>> Bob, this is a great summary, thanks! > >>>> > >>>> One related question, especially with mixed systems -- how do you tell > >>>> if you have optimum signal level at the receiver? > >>>> > >>>> Most show some sort of SNR or Cn value. What should we look for? > What > >>>> are the indication of *too much* signal? One issue in particular is > how > >>>> to handle a modern GPS that expects modest antenna gain when it's > >>>> plugged into a system with a 50dB gain antenna at the top. > >>>> > >>>> Thanks! > >>>> John > >>>> ---- > >>>> > >>>>> On 11/21/19 8:00 AM, Bob kb8tq wrote: > >>>>> Hi > >>>>> > >>>>> Way back in time, the first gear out there to use what we now look at > >>> as “normal” antennas > >>>>> was survey gear. For various reasons they decided on a 12V power > supply > >>> and 40 to 50 db > >>>>> of gain in the preamp mounted in the antenna. They also got into L1 / > >>> L2 pretty quickly. > >>>>> > >>>>> A bit later the cell phone (and later broadcast) guys got into this. > In > >>> a location with a lot of > >>>>> RF (like a cell site) having a lot of gain at the antenna didn’t work > >>> all that well. IMD issues > >>>>> got into the act pretty quickly. In addition, front end filtering was > >>> required to reduce overload > >>>>> issues. The focus was on L1 only so filtering was relatively easy. > >>>>> > >>>>> There is a whole separate set of antennas that put a big chunk of the > >>> RF portion of the radio > >>>>> in the antenna. Those still survive here and there. I have one of > them > >>> and probably a couple > >>>>> of dozen of the more “normal” antennas. > >>>>> > >>>>> As time marched on, supplying 12V to antennas became a bit less > >>> popular. Most of the cell > >>>>> guys went over to a 5V antenna supply. The net result was 12V 50 db > >>> survey antennas that did > >>>>> L1/L2 and much smaller 5V 25 db antennas for “timing”. The timing > >>> antennas didn’t do L1/L2 so > >>>>> not going to work for survey. The survey antennas had way to much > gain > >>> and no filtering so > >>>>> not going to work for a cell site. > >>>>> > >>>>> Indeed things did and do get crossed up in various pro and basement > >>> systems. With care and > >>>>> the right set of circumstances things may work. In other cases the > >>> result can be an ongoing set > >>>>> of systems issues over an entire network of stations. > >>>>> > >>>>> Prices for a good new survey antenna are up in the many thousands of > >>> dollars range. They have > >>>>> very stable phase centers and (usually) test results to allow > >>> correction of any residual phase > >>>>> issues. This is part of what lets you get into the “couple of mm” > range > >>> on a survey. > >>>>> > >>>>> For timing, you have to dig a bit and answer a few questions. Is your > >>> concern how close you > >>>>> are to BIH? If so you will need to know all the delays in your > system. > >>> This includes the delays > >>>>> in the antenna filters and the preamp. Is your concern (or measure) > the > >>> ADEV at 1 second? > >>>>> If so the delays are not a concern. Your antenna choice may be a bit > >>> different depending on > >>>>> this focus. > >>>>> > >>>>> Bob > >>>>> > >>>>> > >>>>> > >>>>>> On Nov 21, 2019, at 1:25 AM, Taka Kamiya via time-nuts < > >>> [email protected]> wrote: > >>>>>> > >>>>>> I have been looking antennas. Prices seem to range less than 30 > >>> dollars to more than 500 dollars. Some are 20db gain and some are 40 > db > >>> gain. Some are specified as marine use only. Some are specified as > timing > >>> use. Some doesn't say anything at all. Power supplies are different. > >>>>>> Other than obvious, antenna is an antenna, isn't it? It captures L1 > >>> signal, amplify it and send it down the coax. What makes one more > costly > >>> than others? What makes one timing antenna and one navigation > antenna? It > >>> doesn't make sense to me. > >>>>>> > >>>>>> I did some simple experiment with 26db, 40db, and magnetic stick on > >>> type. I didn't really see significant difference. Signal level itself > >>> even wasn't all that different. I have nearly a clear sky view 360 > degrees > >>> above 30 degrees above horizon. In some directions, clear view to > >>> horizon. My feed is Timewave type. So It may not be the best but > nearly > >>> ideal. > >>>>>> > >>>>>> Can someone shed light on this topic? (of course, I know some > antenna > >>> has integrated receiver. I am not talking about those) > >>>>>> > >>>>>> --------------------------------------- > >>>>>> (Mr.) Taka Kamiya > >>>>>> KB4EMF / ex JF2DKG > >>>>>> _______________________________________________ > >>>>>> time-nuts mailing list -- [email protected] > >>>>>> To unsubscribe, go to > >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >>>>>> and follow the instructions there. > >>>>> > >>>>> > >>>>> _______________________________________________ > >>>>> time-nuts mailing list -- [email protected] > >>>>> To unsubscribe, go to > >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >>>>> and follow the instructions there. > >>>>> > >>>> > >>>> > >>>> _______________________________________________ > >>>> time-nuts mailing list -- [email protected] > >>>> To unsubscribe, go to > >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >>>> and follow the instructions there. > >>> > >>> > >>> _______________________________________________ > >>> time-nuts mailing list -- [email protected] > >>> To unsubscribe, go to > >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >>> and follow the instructions there. > >>> > >>> _______________________________________________ > >>> time-nuts mailing list -- [email protected] > >>> To unsubscribe, go to > >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >>> and follow the instructions there. > >>> > >> _______________________________________________ > >> time-nuts mailing list -- [email protected] > >> To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >> and follow the instructions there. > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > -- Doc Bill Dailey KXØO _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
