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Kenny, What you say is true. However, I would very much trust the figures that W4RNL quotes as all his figures are derived from computer models (just like F12). Also, don't the ARRL refuse to accept gain figures from manufacturers unless they are supported by computer models? Therefore I have no reason to doubt the figures in their own publication. Besides, the larger antenna in the ARRL Antenna Book is showing a little bit more gain than the smaller antenna of W4RNL which going by the difference in boomlength seems about right. As the T10 is somewhere in the middle with regards boomlength, it's not unreasonable to assume the gain is somewhere in the middle also. This is not like comparing tribanders with different trap designs (and hence, different losses), these logs all use non-loaded elements and appear to have a very similar design constant. Andrew Williamson GI0NWG / AC6WI Homepage = http://www.gi0nwg.freeserve.co.uk/ One of the ZL9CI gang http://www.qsl.net/zl9ci/ In message <AA-2A839778B3BE152AD1140DEA3E5D8F5A-ZZ@www4.prodigy.net>, Kenny K2KW <K2KW@prodigy.net> writes >Andrew, > >Unfortunately you cannot compare gain figures from >different souces, as they most likely have different >reference specs. Force 12 numbers are "conservative" >relative to others, but are more realisitic. More >important, Force 12 exactly explains how it derives >it's gain figures, where others do not. > >The Force 12 RK-10L, their 10 ele LP on a 30' boom, >has 2.1 to 3.0 dB Net Gain. Comparing Force 12 to >Force 12, the delta is on the order of 4 dB, which is >BIG. LP's are totally compromised antennas from a >gain perspective and a well designed LP simply cannot >compete with a well designed Yagi. > >Kenny K2KW > > >--- Original Message --- >From: Andrew Williamson <andrew@gi0nwg.freeserve.co.uk> >To: Force12Talk@qth.com >Subject: Re: [Force 12 Talk] Force 12 vs. Tennadyne > >> >>A Tennadyne T10 is on a 24ft boom which, if properly >designed should >>give something in the region of 6.3dBi (or about >4.15dBd). >> >>On page 10-14 of the ARRL Antenna Book (19th edition) >it shows a design >>for a 12 element log on a 26ft boom giving gain in >the 6.6-6.9dBi >>(4.45-4.75dBd) region across its range. I have no >reason to doubt these >>figures. >> >>On the L.B. Cebik W4RNL webpage >(http://www.cebik.com/3lpda.html) he >>shows a nine element log on a 21ft boom giving gain >in the region of >>5.63-6.33dBi (3.48-4.18dBd) across its range. Again >I have no reason to >>doubt these figures. >> >>The T10 should therefore fit somewhere in between >these figures, which >>would suggest gain in the 6.0-6.6dBi (3.85-4.45dBd) >region across its >>range, as opposed to the totally outrageous 8.24dBi >quoted on the >>Tennadyne webpage >(http://www.tennadyne.com/specs&prices.htm). >> >>Force12 quote the C31XR as having 8.15-9.55dBi (6.0- >7.4dBd) gain across >>10/15/20M, or about 2.5db (on average) above the >T10. This is a >>substantial difference. >> >>The N1217 is quoted as having 8.15-8.25dBi (6.0- >6.1dBd) across its bands >>which equates to about 2dB over the T10, again a >substantial difference. >> >>The other thing to take into account is the amount of >boom and number of >>elements you will be happy to try to keep in the >air. >> >>Going the Tennadyne route results in 10 elements, >24ft of boom and 10.1 >>sq ft of windload whereas the F12 route results in 21 >elements, 49ft of >>boom and 15.7 sq ft of windload. >> >>Really, the decision you have to make is to consider >whatever you would >>be happy keeping in the air and what compromise you >want to make on >>gain. >> >>Andrew Williamson GI0NWG / AC6WI >>Homepage = http://www.gi0nwg.freeserve.co.uk/ >> >>One of the ZL9CI gang >>http://www.qsl.net/zl9ci/ >> >> >>In message <E19CWEV-0000bo-OA.2003-05-05-04-02- >30@imailg1.svr.pol.co.uk> >>, KEN SILVERMAN <k2kw@prodigy.net> writes >>>A WELL designed log often has no more than 3 dB of >gain per band, sometimes >>>less. F/B performance is also not the same as a >monoband Yagi. If you are >>>interested in busting pileups easier, creating your >own pileups, or looking >>>to improve contest scores, go with the C31 XR and >12/17 Yagis. LPs are >>>simply not equal to the performance of well designed >monoband Yagis, which >>>is what you are getting with the latter. If you >want an LP (I personally >>>cannot think of why someone would ever consider an >LP unless you do serious >>>MARS or out of band RXing), buy a Force 12 LP! >>> >>>Kenny K2KW >>> >>> >>>----- Original Message ----- >>>From: "Law Offices of J D Lambright, PLLC" ><JDLambright@the-law-offices.com> >>>To: <Force12Talk@qth.com> >>>Sent: Sunday, May 04, 2003 9:17 AM >>>Subject: [Force 12 Talk] Force 12 vs. Tennadyne >>> >>> >>>> I would like to hear your comments and >recommendations regarding my >>>antenna >>>> choices. I have recently acquired the following >antennas second-hand: >>>> >>>> A. Tennadyne T-10 log periodic (10 elements on a >24 foot boom) >>>> >>>> B. Force 12 C-31-XR with 14 elements on a 31 foot >boom for 10, 15, and 20 >>>> meters - (wide-spaced 3 element 20 meter Yagi, >wide-spaced 4 element 15 >>>> meter Yagi, and a 7 element 10 meter Yagi). >>>> >>>> C. Force 12 N1217 with 7 elements on an 18 foot >boom for 12 and 17 meters. >>>> >>>> D. Force 12 EF-706 with 7 elements on an 18 foot >boom for 6 meters. >>>> >>>> For HF coverage, I'm trying to decide whether to >install the T-10 or, >>>> alternatively, the two Force 12's. (I think they >are all great antennas, >>>so >>>> perhaps I should find a way to install all three!) >My towers are a Rohn >>>100' >>>> SSV freestanding commercial-type tower and a >Wilson 61' crank-up pole >>>tower. >>>> >>>> I would most appreciate hearing your comments on >the pros / cons of these >>>> antennas and your suggestions on how best to >install them. I am located >>>near >>>> Houston, Texas, so things like ice are not a >problem. >>>> >>>> J D Lambright >> >> >> >>-------------------------------------------- >>Force12Talk mailing list provided as a service by >Force 12 Antennas, Inc. >>Force12 Web Site: http://www.force12inc.com >> >>To Submit Message to the List: Force12Talk@qth.com >>To unsubscribe and view the Message Archive: see >http://qth.com/force12/list >>For problems with the list: contact n4zr@qth.com >> > > > -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact n4zr@qth.com |