Balun Identification

[Mike/W8BAC]

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

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

[Opcom]

the only wya is to look it up or ask the seller.

[Steve - WB3HUZ]

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.

[WA1GFZ]

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

[Mike/W8BAC]

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

[WA1GFZ]

yup terminated Rhombic or T2FD

[Ralph W3GL]

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