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> Mini-circuits tmo-1.5-1 rf transformers 1.5:1 (qty.2)
Mini-circuits tmo-1.5-1 rf transformers 1.5:1 (qty.2)
Mini-Circuits TMO-1.5-1 RF Transformers 1.5:1, 0.1 .. 300MHz (Qty.2)
Match between 50ohm : 75ohm systems, LF..VHF, test gear adaptors, etc
On offer is one lot of 2 new old stock RF transformers, part number TMO-1.5-1-8 by Mini-Circuits. These are now discontinued and can be hard to find.
The most obvious application for a 1.5 : 1 tranformer is matching of impedance between 75 ohm and 50 ohm RF systems. Quite often 75 ohm devices and cables appear on the surplus market from the A/Vand broadcast sectors and these transformers will allow them to be used in 50 ohm systems. They will, of course work in both directions, so a pair is useful to match both input and output of a device. There's an interesting article on the 50 Ohm vs. 75 Ohm thing at http:// /encyclopedia/why50ohms.cfm.
Minicircuits has some good general info on the basics of RF transformers at: http:// /pages/pdfs/howxfmerwork.pdf and http:// /pages/pdfs/tran14-2.pdf
The ratio given, as specified by Minicircuits is the 'ohms ratio' NOT the turns ratio between primary and secondary windings. A transformer transforms resistance as the square of the turns ratio, so a 1:4 ohm ratio transformer (eg. T4-6) has a turns ratio of 1:2 ... and a 1:16 ohms ratio (of the T16-1) is realised with a 1:4 turns ratio. Following this logic you can see why the 1:1.5 ohms ratio of the TMO-1.5-1 (as needed to match 50 ohm to 75 ohm) is not so straightforward to implement well ... the turns ratio must be the square root of 1.5 (ie 1:1.2247). I admit I'm not sure how ... Clever stuff! ;-)
http:// /cgi-bin/spec?cat=tranfrmr&model=TMO1.5-1&pix=a03.gif&bv=4
* The data above is still on the MCL site in their old CGI web system but not searchable/findable from the homepage. The electrically equivalent model T1.5-1 has a datasheet on the site at: http:// /pdfs/T1.5-1.pdf.
Mini-Circuits no longer produce the 1.5 : 1 ratio transformers in these high reliability (military grade) metal packages. Other ratios in the 'TMO' package retail over $10 US each. I know of no other source for these, mine came from a US hamfest via a friend. I have a few more so will likely list again but supply definitely limited.
The past year has been a challenging one; the relocation and a host of other factors combined ... so let's just say I'm looking forward to better fortune in 2010.
Indeed I wish each and every one of you a fine year ahead ... may your projects be successful with a minimum of unexpected smoke ... though of course if you ever need replacement parts you know someone to ask ;-)
!! Seasons Greetings to All !!
