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propagation "numbers" virtually the same as last night (at the same time), I was able to work 2 stations that were only "ESP" last night (S92UN and YO2RR). It seems as though lowering the TO angle from 20 degrees to 15 degrees and increasing the gain by .5 dbi does make a difference when you are dealing with a shortened antenna such as the Force-12 Sigma 5. Both were on 20M and I ran 400W. I had to call quite a few times - but less than 10 minutes worth. Not bad for a 9' antenna . . . . well I guess its 15' now (hi hi). By the way, the feedline and control cable run 90 degrees away from the antenna for 1/4 wl and there are no objects near the antenna for at least 1/2 wl. I don't know if that matters - but I thought that would be the right way to go. And these stations were contacted outside of gray line. I will see what happens later tonight during the EU / AFR AM grayline, (when conditions have been very good the last 2 -3 days). Even if all of this is wishful thinking, I certainly haven't hurt anything by raising the antenna. I will NOT go higher because high angle lobes would form and I think roof mounting a Sigma 5 would HURT its performance. At least EZNec shows these lobes when the antenna is > 6'. Cebik has an article on short hatted verticles and he seems to agree with the 6' height . . . . . his is a full sized 1/2 v.d fed with ladder line - which is essentially what the Sigma 5 is since it uses center loaded coils and the "hats" to "lengthen" the sides of the dipole. Even though I have no desire to roof mount the antenna, if anyone has and didn't notice a performance degradation I'd be interested. I do know that when you move the antenna up or down, the feedpoint impedance changes - which can be "settled" by using a tuner. I use a Ten Tec 238B "L network" tuner since it has fairly low insertion loss, and I use it as "protection" since I have an amp in line. 73, Rich KY6R ----- Original Message ----- From: "Rich Holoch" <rholoch@attbi.com> To: <Force12Talk@qth.com> Sent: Wednesday, April 23, 2003 14:01 Subject: [Force 12 Talk] RE: Sigma 5 Height > Actually - I use 200W max on 30M, 400 - 500W max on 40 - 10M, but only > after I first try with 100W (I hate turning on the amp as I am an "ex-QRP > only" guy). For Oceania and Asia I try to work the DX using my new Argonaut > 5 or Elecraft K1 set at 5W. The S05X, TY5ZR and JY9QJ QSO's were all on 20M > during their gray line at about 400W. > > Receive performance is what I am most interested in since I listen most of > the time. I certainly agree - propagation is key - and I have noticed that > since late February there has been more "high angle" noise which severely > affects the MA5B, but doesn't affect the Sigma 5. I can actually hear DX > stations and work them on the Sigma 5 where its just noise on the MA5B. S05X > was the best test - crummy conditions on the West Coast and huge pileups. > My 30M dipole up 35' with a tuner outperformed my MA5B. The Sigma 5 did even > better. > > * * * * * > > I just re-ran the numbers and it looks like at 6' up, the TO angle for all > bands 20 - 10M on the Sigma 5 is 15 degrees and the gain is almost .5 dbi > higher than with the antenna at 2'. I'll see if i can tell the difference > now that I've just raised it up to 6'. > > Rich > KY6R > > > > > -------------------------------------------- > 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 |
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