It is called a "Bias T" and you will need two of them to accomplish your goals. One at the shack end and one at the antenna end. A sample of a commercial bias t can be seen here. http://www.mfjenterprises.com/products.php?prodid=MFJ-4116
Hope this helps.. /joe -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Don Wilhelm Sent: Sunday, February 18, 2007 7:53 PM To: [EMAIL PROTECTED]; elecraft@mailman.qth.net Subject: RE: [Elecraft] K2 to antenna Power Bob, That technique is often done to switch relays, so yes it can be used in the presence of transmit RF voltages. Basically the way it is done is to capacitor couple the RF to the coax at both ends (a series capacitor) and feed the DC to the coax through RF Chokes sized to have at least 10 times the coax impedance at the lowest operating frequency. The capacitors must be large enough to have a low impedance at the operating frequency and their voltage rating must be large enough to withstand the peak RF voltages present - all with adequate safety factors (3 is usually good) considered. Note that none of these parameters relate to the control voltage or current - of course the RF chokes must be able to handle whatever current is required for the control mechanism. I do not have a handy reference to a schematic, but that is the 'jist' of how it is accomplished - the capacitors keep the DC voltage off the transmitter and the antenna and the RF Chokes keep the RF out of the control signals. 73, Don W3FPR > -----Original Message----- > > > Good evening Elecrafters, may your Monday be a restfull one! > > I would like to send a low voltage limited current up the coax from > my K2 to the antenna for powering a small device. What would be the > best way to inject this voltage into the antenna feed (coax) at the K2 > and recovering it "up the stack"? I was hoping to continue supplying > this voltage even while transmitting 100 watts. I thought that the > transverter manuals might have some advice about powering preamps but, > not a word. > > Best regards, Bob K7HBG. > K2# 2836 which "Will only be pried from my cold dead fingers" > _______________________________________________ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.441 / Virus Database: 268.18.1/691 - Release Date: > 2/17/2007 5:06 PM > -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.18.1/691 - Release Date: 2/17/2007 5:06 PM _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
