# (Frequnecy of) Bias tees and looking for online retails

Currently, I'm looking for some bias tees to add some DC bias to RF signals (whose carrier frequency is not determined yet, but definitely lower than 30 MHz and amplitdue does not exceed +/- 3 V.)
Since I'm not familiar with electrical engineering, I've referred some articles and papers and found bias tees from Aeroflex/Inmet.
In the page, I'm curious that what does frequency column stand for. Is it cutoff frequency of bias tees? And can I use those bias tees for my application?

And for the price around $420, it is a bit expensive than I expected (Detail price will be different after quote.) Therefore, I'd like to look up other bias tees on some online retails and could you recommend some retails? I already know one, element14. ## 2 Answers Yes, the frequency is the frequency range of the RF input. The Mini-Circuits ZFBT-4R2GW+ should do the job for US$80. These are very reliable.

For RF frequencies below 30 MHz, you can build your own without too much electronics knowledge. However, you need to know both the minimum and maximum RF frequencies, and you should know the output impedance of the RF source and the input impedance of the RF load.

Those are very high end bias tees intended primarily for microwave and mm wave applications. If you're not going to use them above 1 GHz, get something cheaper. The frequency range listed is for the main signal path, so 50 kHz to 18 GHz would work for RF ranging from 15 kHz all the way up to 18 GHz. These are designed to pass that range through the RF side with as few purturbations as possible while blocking it from flowing back out the DC port. They also block DC from flowing between the RF ports.

The bias tees from mini circuits are probably a much better choice - their 200 kHz to 12 GHz bias tee costs about \$100. They also have one from 100 kHz to 4.2 GHz for a bit less. See http://www.minicircuits.com/products/BiasTees.shtml .

• I am too slow :( – Dave Kielpinski Feb 6 '15 at 9:10