Re: Topband: Lab style comparison results on 160m small lot antennachanges.
Tests to answer the question "is the FCP better than counterpoise X" can be answered by 28 MHz scale models. The question "the FCP is better at 1.8 MHz by Y dB" cannot be answered by 28 MHz scale models. What question do we really need answered? Dave WX7G On Dec 21, 2012 11:30 AM, "Tom W8JI" wrote: > > - Original Message - From: "Guy Olinger K2AV" < > olin...@bellsouth.net> > To: "TopBand List" > Sent: Thursday, December 20, 2012 7:25 PM > Subject: Topband: Lab style comparison results on 160m small lot > antennachanges. > > > A prior poster, lamenting the nature of FCP success reports, wrote: >> >> "Who has done that, with only a radial change, against an unchanged >> reference antenna that is in the far field of the antenna under test. >> [Where's the post with the details] ?" >> >> Perfectly logical question. We all would like that answered with posts >> listing lab grade experiments. >> > > > Because of antenna size, laboratory measurements are impossible on lower > bands. For that reason we can't make lab-style comparisons. > > There is one thing, though, that we probably all agree on. > > If more than one thing that can affect results changes in an unknown way > in any test or experiment, like the ionosphere or reworking an entire > antenna system from less-than-good system to a new one, we really don't > know what caused the change or if any one particular thing was responsible > for the change. > > If we A-B against any unchanged reference, we at least know which was > better than the reference and how much better. None of this requires a lab, > precise equipment, is unreasonable, or is in the most remote way unfair. It > just requires reasonable methods. > > 73 Tom > __**_ > Stew Perry Topband Distance Challenge coming on December 29th. > ___ Stew Perry Topband Distance Challenge coming on December 29th.
Topband: 80M (almost Topband) 4-sq loading coils
Well, I ran out of time. Work keeps getting in the way. I wont get the radials down before the ground freezes as I still need to clean out the wild growth. Presently I have three ¼ wave radials at each elevated feedpoint. The feedpoints are presently elevated because I have uneven terrain plus lots of wild growth towards the West. It seems over the past couple of years the ice loading has stretched the wire somewhat from the original dimensions. That affected the pattern. Last year I made sure all the lengths were fine again and the pattern seemed to improve. This past winter with heavy ice loading I seemed to have some stretching of the #14 wire. The pattern seems to be quite sensitive to the matched lengths of the radials. After reading N6LFs info and realizing I cant put up a plethora of ¼ wave elevated radials I want to try some shortened elevated radials to see if that helps the pattern. Hopefully the gain wont be affected much. The feedpoints are about 8 above ground. If I make the radials 36 long I can put up 6 at each feedpoint with fairly close symmetry. I believe that means I would need roughly 16-18uh at each feedpoint to resonate the radials. Instead of going with coil stock, is there any reason for not using a toroid with a number of turns? If not, I assume I would want to use a powdered-iron core? Any issues I should be concerned about? Any recommendations for what type of core I should use for this application? I plan on using #14 enameled wire. I would assume it is best to cover the core with glass tape first? Anything I am missing with this plan or am I wasting my time with the shortened radial idea? This winter I will finish cleaning the area to the West of the tower where I have lots of wild growth. Next year I will be able to put down ground mounted radials in all directions. The plan then will be to put down 30 radials under each feedpoint and lower the feedpoints to the ground. Figured going with 50 length radials. As always, all comments and suggestions are welcomed. 73 and Merry Christmas N2TK, Tony ___ Stew Perry Topband Distance Challenge coming on December 29th.
Re: Topband: Lab style comparison results on 160m small lot antennachanges.
- Original Message - From: "Guy Olinger K2AV" To: "TopBand List" Sent: Thursday, December 20, 2012 7:25 PM Subject: Topband: Lab style comparison results on 160m small lot antennachanges. A prior poster, lamenting the nature of FCP success reports, wrote: "Who has done that, with only a radial change, against an unchanged reference antenna that is in the far field of the antenna under test. [Where's the post with the details] ?" Perfectly logical question. We all would like that answered with posts listing lab grade experiments. Because of antenna size, laboratory measurements are impossible on lower bands. For that reason we can't make lab-style comparisons. There is one thing, though, that we probably all agree on. If more than one thing that can affect results changes in an unknown way in any test or experiment, like the ionosphere or reworking an entire antenna system from less-than-good system to a new one, we really don't know what caused the change or if any one particular thing was responsible for the change. If we A-B against any unchanged reference, we at least know which was better than the reference and how much better. None of this requires a lab, precise equipment, is unreasonable, or is in the most remote way unfair. It just requires reasonable methods. 73 Tom ___ Stew Perry Topband Distance Challenge coming on December 29th.
Re: Topband: Lab style comparison results on 160m small lot antenna changes.
DAVID CUTHBERT wrote: > why must we continually test NEC against measurements? The work by N6LF has > shown great correlation between simulation and the real world. > Those of us who design electronic circuits (including EM) in the world of > computer simulation have great faith in the various programs and NEC-4 (and > possibly NEC-2) should give us an adequate A-B comparison. The question of correlation with reality must be answered for each particular sumulation. NEC works most accurately with straight thin wire antennas. It leaves much to be desired with telescopic tube elements, and it fails completely to predict effects of booms in case of VHF/UHF antennas, etc. In those and other cases, there are programs that work much better. For example, WIPL-D computes telescopic tube elements much more accurately than NEC (or MININEC), and can also accurately model influence of booms and other nearby conductors. 73, Sinisa YT1NT, VE3EA ___ Stew Perry Topband Distance Challenge coming on December 29th.
Re: Topband: Lab style comparison results on 160m small lot antenna changes.
Dave, I have a lot of faith in NEC and N6LF's work, also. But I think the testing is required partly because we cannot successfully model Guy's folded counterpoise in NEC to determine the changes in ground loss, etc. I would love to remote-switch between a few elevated radials and an FCP under an inverted-L here at my QTH. 73, Mike www.w0btu.com On Fri, Dec 21, 2012 at 8:21 AM, DAVID CUTHBERT wrote: > Guy, > > why must we continually test NEC against measurements? The work by N6LF has > shown great correlation between simulation and the real world. > > Those of us who design electronic circuits (including EM) in the world of > computer simulation have great faith in the various programs and NEC-4 (and > possibly NEC-2) should give us an adequate A-B comparison. > > Dave WX7G > ___ Stew Perry Topband Distance Challenge coming on December 29th.
Re: Topband: Lab style comparison results on 160m small lot antenna changes.
"Trust but verify". As with SPICE or any other simulation program... garbage in, garbage out. An experienced antenna modeler knows what assumptions are good to make because of past verifications of results. Modeling of ground conductivity and losses involves more assumptions than most of the wires/poles in the air (and you will note, is where most of the arguments are about!). And of course we can always argue about how many helicopters it takes to do the verification step :-) Tim N3QE -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of DAVID CUTHBERT Sent: Friday, December 21, 2012 9:21 AM To: Guy Olinger K2AV Cc: TopBand List Subject: Re: Topband: Lab style comparison results on 160m small lot antenna changes. Guy, why must we continually test NEC against measurements? The work by N6LF has shown great correlation between simulation and the real world. Those of us who design electronic circuits (including EM) in the world of computer simulation have great faith in the various programs and NEC-4 (and possibly NEC-2) should give us an adequate A-B comparison. Dave WX7G ___ Stew Perry Topband Distance Challenge coming on December 29th. ___ Stew Perry Topband Distance Challenge coming on December 29th.
Re: Topband: Lab style comparison results on 160m small lot antenna changes.
Guy, why must we continually test NEC against measurements? The work by N6LF has shown great correlation between simulation and the real world. Those of us who design electronic circuits (including EM) in the world of computer simulation have great faith in the various programs and NEC-4 (and possibly NEC-2) should give us an adequate A-B comparison. Dave WX7G ___ Stew Perry Topband Distance Challenge coming on December 29th.
