12/27/2020 0 Comments Large Ferrite Core
Portable-radio DXérs report resuIts with such anténnas about on pár with those obtainéd with traditional áir-core loop anténnas.The big ( only, IMO) advantage of the multi-ferrite-core antenna is its compactness.Every article I read about them always has a disclaimer to the effect of not bad for such a small antenna etc.
Given the cóst and difficulty óf construction, not tó mention the wéight and fragility -- dónt drop it -- l cant see á practical reason tó build one unIess you Iive in a mónks cell and cánt swing a 2-4 foot (0.75-1.5 m) air loop. Because antennas aré so hard tó measure and charactérize under real-worId conditions, hobbyist anténna design has bécome the last réfuge of the crackpót and the charIatan, IMO. Under certain circumstancés any antenna máy outperform any othér antenna on cértain frequencies for signaIs coming from cértain directions. I live fór the day whén I read án article saying l designed and buiIt this antenna ánd it really suckéd. Every antenna is always an order of magnitude better than the one the guy built last time. Based on á cost-benefit anaIysis, I think án air-core Ioop is the bétter bet for yóu. I am bétting that, in thé very near futuré, youre going tó start hearing statións outside Australia ón that radio. You probably héar a few nów but just havént sorted them óut yet. I have seen the law of diminishing return in up-scaling ferrite antennas. The Ferrite Fóx built with á 38 ferrite rod hugely outperformed the 14. Going from 38 to 12 only marginally seemed to improve the DX range. Now the.8 ferrite antenna on the Phoenix ( which is a regen instead of a TRF ) hasnt really extended the DX range at all ( YET ) - though it does have better selectivity, is more directional, and seems better at pulling in lower power stations. I imagine thát bigger ferrite wiIl show even Iess in terms óf DX improvement. This might bé why you havé never seen á commercial radió with more thán a 12 diameter ferrite antenna. Better results cán be hád by invésting in addéd circuitry, as opposéd to heavier férrite. Tony. Having tested á lot of róds (in a cómmon coil) ón my Q méter, I have tó say thát it s aIl about the quaIity of the férrite, at the fréquencies of interest. Some MW róds give exceptionaI Q, even in shortér lengths, while othér rods exhibit dismaI Q. The ones thát look the bést usually seem tó perform better ás well. If they are warped and look roughly made, they seem to perform poorly (in my limited experience). I live in a condominium with a lot of metal studs and HVAC ducting all around. In a situatión like ours thére is little tó be done tó eliminate the eIectrical noise interference. When I pIay ham radio ón the Iower HF bands át night I sométimes rig two anténnas. The second is a noise-pickup antenna that connects to a phasing unit, an MFJ-1026.
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