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EF205A1 - 14 MHz 5 el. Monobander 

Ova antena je urađena za YT1BB koji nikako nije bio zadovoljan svojom originalnom HyGain antenom HG205BA. Problem je bila njena uskopojasnost i potreba da se krajevi elemenata često skraćuju ili produžavaju, zavisno da li je trebalo raditi CW ili SSB kontest. Obzirom da se radi o zaista ogromnoj i teškoj anteni, razumljivo da to nije bilo jednostavno i lako često raditi, pogotovo po lošem vremenu što je često bio slučaj. 

Zaintrigiran antenama koje sam u to vreme uradio za 4N1SM kod kojih sam postigao da sa skoro istim pojačanjem pokrivaju ceo radni opseg sa ekstremno malim SWR pitao me je da li bi mogao da re-dizajniram njegovu originalnu antenu i postignem sličan rezultat. Naravno, izazov je bio veliki i vrlo rado sam se upustio u taj poduhvat. 

Pre početka rada, OM Vlado mi je rekao da on ima na raspolaganju dodatnu količinu odgovarajuće cevi kojom bi boom mogao da se produži na celih 15m pa je to bila prilika da se izvuče i više pojačanja nego što je davala originalna antena. Korišćeni su svi originalni elementi HG205 antene kao i nosači elemenata što je u mnogome olakšalo rad. Sve što je bilo potrebno uraditi je bilo pomeranje položaja elemenata na nove pozicije na boomu i korekcije krajeva elemenata na nove dužine što je urađeno veoma brzo i lako. 

Krajnji rezultat je bio iznad svih očekivanja jer je dobijeno dosta veće pojačanje, izuzetno dobar F/B i što je najvažnije, antena sada pokriva ceo opseg sa SWR koji je < 1:1.10 – čak i bolji nego što su pokazale kompjuterske simulacije. Priložen je dijagram izmerenog SWR radi poređenja. 

Nakon verifikacije rezultata OM Vlado je pitao da li bih mogao da spremim repliku “iste” antene ali sa drugačijim prečnicima elemenata jer originalnih (imperijalne dimenzije) nije imao. To je već bio mnogo lakši zadatak i posle nekoliko dana uradjena je nova antena nazvana EF205A2 koja je dala identične specifikacije, samo sa drugačijim setom prečnika elemenata. 

Vlado je sada te dve antene stakirao u sistem (gornja je na 35m a donja na 20m) i vrlo često se na DX klasteru mogu videti oduševljeni izveštaji o fantastičnom signalu koji OM Vlado sada ima na 20m.

  

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  This antenna was designed for YT1BB who was not very pleased with his original HyGain HG205BA antenna. Problem with BA205 was narrow band performance and need to lower antena down for element tips correction, depending if he was planning to work CW or SSB contest. Having in mind that it is not light and small antenna at all, that task was qiute demanding especially if that had to be done over poor weather conditions. 

Intreeged with my recent designs done for 4N1SM 15m monobanders that had almost flat SWR response over entire band he asked me if I can re-design his original antenna by using original elements and achieve similar result. For me that was a real challenge so I gladly accepted it. 

Before I started working Vlado told me he had a lot of boom tubing equal to HG205 boom so antenna can be extended up to 15m (49.2ft) so it was a good chance to get even more gain than original antenna. All original HyGain elements and brackets were used and that made whole job much easier. All what was needed is to relocate brackets to new positions and adjust element tips to fit new total length of the elements. It was done easy and smooth in a couple of days. 

Final result was far better than expected since we got much more gain, extremely good F/B ratio and most importantly flat SWR of < 1:1.10 over entire band – even better than computer simulation has shown. Attached is meassured SWR for comparison to simulated values. 

After few days of testing and performance verification, Vlado asked me if I possibly could make a replica of that antenna but with completely different set of tubing since imperial sizes are not available here. That was much easier thing to do and just after few days new antenna named EF205A2 was ready and it gave just identical results as the original antenna – just with different set of element tubing sizes. 

Those two antennas are now stacked at 35m / 20m and very often on DX CLX we can see reports of his big signal produced on 20m with those remarkable antennas. 

 

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FREE SPACE GAIN       10.20 dBi       ( 8.06 dBd )

  GAIN AND PATTERN IF ANTENNA IS AT 20m A.G.