K2 to antenna Power
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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: [hidden email] 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 |
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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: [hidden email] > 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: [hidden email] 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 |
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In reply to this post by k7hbg @dslextreme.com
You need as a minimum a capacitor in the coax center lead to your K2 in
order to prevent DC from getting into the radio. Second you will need a choke on your low voltage supply at a value that presents a large impedance to RF frequencies you are operating on and therefore blocking RF from entering your small supply voltage. There really should be other components to ensure a fairly flat impedance reading across the bands you wish to operate. The Handbook should have some examples of this. Regards, Robert VE3RPF [hidden email] wrote: > 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: [hidden email] > 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: [hidden email] 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 |
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In reply to this post by Don Wilhelm-3
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: [hidden email] [mailto:[hidden email]] On Behalf Of Don Wilhelm Sent: Sunday, February 18, 2007 7:53 PM To: [hidden email]; [hidden email] 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: [hidden email] > 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: [hidden email] 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: [hidden email] 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 |
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