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Title: Balun Identification Post by: Mike/W8BAC on October 04, 2008, 07:15:32 PM Have a look at this auction before the listing and pictures are gone.
http://cgi.ebay.com/10KW-HF-RF-Balun-Broadcast-Shortwave-Ham-Radio-Collins_W0QQitemZ130259618302QQcmdZViewItem?hash=item130259618302&_trkparms=39%3A1%7C66%3A2%7C65%3A13%7C240%3A1318&_trksid=p3286.c0.m14 (http://cgi.ebay.com/10KW-HF-RF-Balun-Broadcast-Shortwave-Ham-Radio-Collins_W0QQitemZ130259618302QQcmdZViewItem?hash=item130259618302&_trkparms=39%3A1%7C66%3A2%7C65%3A13%7C240%3A1318&_trksid=p3286.c0.m14) My question is, If you had this item in front of you, could you tell by testing if it is a 4:1 (voltage) balun or a 1:1 (current) type balun? If so, how would you/I test it? Thanks for your help in advance. Mike Title: Re: Balun Identification Post by: Opcom on October 05, 2008, 12:08:42 AM the only wya is to look it up or ask the seller.
Title: Re: Balun Identification Post by: Steve - WB3HUZ on October 05, 2008, 12:46:57 AM Sig gen on one side, scope on the other. Measure the voltage ratio, calculate the turns ratio.
The description of the item sez 50 Ohms to 600 Ohms. Title: Re: Balun Identification Post by: WA1GFZ on October 05, 2008, 08:59:43 PM Hang 600 ohms noninductive across the output to reflect 50 ohms back to the generator. $500 is a bit high for someting you could build for under $40.
So all you get is a fancy case for all that money Title: Re: Balun Identification Post by: Mike/W8BAC on October 06, 2008, 05:31:48 AM Hi Frank,
I didn't buy it. I'm just asking about it. If I have it straight it is a 12:1 transformer. The business about a balun being a Voltage or current type is still unclear. I was under the impression this would be useful to convert a 50 ohm feed line to a 600 ohm line but if the wire antenna is higher or lower than 600 ohms it wouldn't work. So the balun is for a 600 ohm feed line into a rhombic perhaps. Thanks for your help. Mike Title: Re: Balun Identification Post by: WA1GFZ on October 06, 2008, 08:53:31 AM yup terminated Rhombic or T2FD
Title: Re: Balun Identification Post by: Ralph W3GL on October 06, 2008, 03:35:14 PM Back in the day, the military/commercial point to point transmitter sites used a standard of 600 ohm outputs...There were some transmitters that had 50/70 ohm output like the AN/FRT15 or PW-15 as well... . W2PFY's GE - MW-2 is set up directly for 600 ohm output! The transmitter building used a trolly line system to route the outputs to different antennas. Antennas used for more or less close in communications (out to 300-500 miles) were delta fed dipoles at a mean height of 1/4 to 1/2 wave above ground while long haul antennas were rhombics or curtans, etc all with mostly 600 ohm open wire feeds. There are antennas out there that are fed with 50/70 ohm feedline and these are generally broadband units with a octave range of 2 or 3 like the standard Discone antenna...... This $500 box was meant to go between a transmitter like the FRT-15, (PR 4x1's modded by a pr 4x1's, 2 to 22 MCS coverage) or higher output up to 10 KW, to match into the open wire feeds of whatever antennas to be used. This info comes from actual experience as OIC of a remote transmitter site, way back in the 50's...We had rigs running as much as 76KW input (AN/FRT-4) to 2.5KW input (MW-2's) with many in between those units of different power levels. Ralph, W3GL |