At 03:03 PM 12/9/2011 -0800, you wrote: >In the 1960's one very popular and cheap H.F. antenna was the folded dipole. >Often they were made from the ubiquitous 300 ohm "twin lead" used on TV >antennas and fed with the same twin lead since the impedance of a folded >dipole is close to 300 ohms. The first time I saw 4:1 baluns being sold to >Hams was to make it easy to connect the 300 ohm feeder to such a folded >dipole to the output of a rig designed to feed 50 ohms. > >As Hams migrated away from rigs with tunable output networks to rigs with >fixed tuned outputs, MFJ and others produced a line of antenna tuners >specifically designed to correct feed line mismatches since that could no >longer be done at the rig. They included the popular 4:1 balun for those who >were feeding various open wire lines (typically 300 to 600 ohms but which >may have significant SWR - so the impedance might vary much more). > >It seems that many Hams considered the 4:1 ratio some sort of magic number, >when all it was intended to do was provide a good transfer between 300 ohms >and 50 ohms. > > >Ron AC7AC
Hi Back in late 50's early 60's I bought my first balun from Heathkit ... made from special Bifiler wound Airdux coils which could be connected in either 1:1 or 4:1 configuration. I still have that balun in its 5"x9"x9" aluminium case. I used it with my first Xmiter which was homebrew, 300 watts, and plate modulated AM. I used a folded dipole made of 300 ohm twinlead fed by the same twinlead and the balun in a 4:1 configuration. The dipole was strung between 70ft towers. It was a wonderful setup at a wonderful time (from a propagation point of view). The ZL's and VK's were like locals! es we used to chat about the best way to grow tomatoes hihi These days I still use a balanced feed system with either 300 or 450 ohm feed line ... but with fixed impedance output xmiters and vy much lower power. I no longer use fixed resonant folded dipoles ... but a nonresonant dipole that is useable on multiple bands with a matching unit at the shack. The matching unit I use is a link coupled L network .. often referred to as a "Z-match". The system seems to be vy efficient as I have no problem working the world with 20 watts. SSB for local contacts and nets and CW/PSK for DX. No problems with RFI !! Back in the day .. my 300 watt AM xmiter was a TV killer .... but then no one in out neighborhood watched TV during the day (week-ends excluded) and the (1 station) shut down at midnight. I just had to stay up late and/or skip school hi hi. Jim, VE3CI >-----Original Message----- > >I can attest to what Vic says. I have an 88-foot long doublet, hung about 45 >feet up, fed with 85 feet of 600-ohm ladder line. At the shack end I have a >1:1 balun, and then about six feet of RG/8X running to the K3. The K3's >tuner likes the combination. I tried replacing the 1:1 balun with a 4:1 from >the same manufacturer. The K3 was quite unhappy with the change in >components. The 4:1 went back on the shelf, the 1:1 went back inline. YMMV > >Jim / W6JHB ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
