Counterpoises for KAT100
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Id like to pigtail counterpoises for 10, 30, 80 and 160 meters for my
200+/- wire which is configured as an endfed inverted U up about 65-70. The horizontal run is about 90; the down-turned end is about 50 long, and stops about 15 from earth. The horizontal run is across a steel-shingled roof with a ridgeline up about 26 from earth. (If the 50' downturn is counterproductive, I could eliminate it, but the antenna doubles on my dx xtal radio set and seems to work better with this ant.) For the ¼ wave counterpoises, Id like to feed them to my KAT100 with a single wire 6 long. I would prefer to join the longer c.p.s to this single wire outside the window. Is this practical? I assume I would subtract the 6 from the calculated ¼ wavelength of each band and attach wires of respective lengths to the 6 wire. Ill probably pigtail the 10 meter c.p. closer to the KAT100 inside the shack and keep it along the floorboard. C.P. height: Resources indicate a preferred height of 6-8 above ground. Is this a minimum or could I lay the 80 and 160 meter c.p.s on top of my roof? I will not be able to lay out the 160 meter c.p. in a straight line in any event. Tnx es 73, Gil NN4CW _______________________________________________ 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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Gil,
For effective counterpoise operation, you should tune them to the proper length. If you tune them in place, you will not have to worry about ground effects and proximity to other objects detuning them. Cut them longer than you think you will need. Yes, you can connect them to your single 6 ft. wire as long as you include that wire in the tuning process. If you have an antenna analyzer, or better yet, an old fashioned grid dip meter, put the wires in place (disconnected from the KAT100) and find the resonant frequency of the counterpoise wire (hint, it will be a half wave 'dipole' at double the operating frequency and should show resonance by a dip or zero impedance - how to couple the meter into the wire is the main problem to be solved here). Once you get them tuned, they should be effective in providing a good RF Ground at the KAT100 ground connection (where it should be). Yes, the wires should be at least 6 to 8 feet high - in other words, keep them out of reach for humans and pets - they will carry RF Current and have high RF Voltage at the far end, so plan on using adequate insulators. 73, Don W3FPR > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]]On Behalf Of Gil Stacy > Sent: Wednesday, November 02, 2005 11:57 AM > To: [hidden email] > Subject: [Elecraft] Counterpoises for KAT100 > > > Id like to pigtail counterpoises for 10, 30, 80 and 160 meters for my > 200+/- wire which is configured as an endfed inverted U up about 65-70. > The horizontal run is about 90; the down-turned end is about 50 > long, and > stops about 15 from earth. The horizontal run is across a > steel-shingled > roof with a ridgeline up about 26 from earth. (If the 50' downturn is > counterproductive, I could eliminate it, but the antenna doubles on my dx > xtal radio set and seems to work better with this ant.) > > For the ¼ wave counterpoises, Id like to feed them to my KAT100 with a > single wire 6 long. I would prefer to join the longer c.p.s to this > single wire outside the window. Is this practical? I assume I would > subtract the 6 from the calculated ¼ wavelength of each band and attach > wires of respective lengths to the 6 wire. Ill probably pigtail the 10 > meter c.p. closer to the KAT100 inside the shack and keep it along the > floorboard. > > C.P. height: Resources indicate a preferred height of 6-8 above > ground. > Is this a minimum or could I lay the 80 and 160 meter c.p.s on top of my > roof? I will not be able to lay out the 160 meter c.p. in a > straight line > in any event. > > Tnx es 73, Gil NN4CW > > > _______________________________________________ > 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: 7.1.362 / Virus Database: 267.12.7/156 - Release Date: 11/2/2005 > > _______________________________________________ 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 |
RE: Counterpoises for KAT100
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One comment to add to Don's is that the length of the common wire must be
SHORT in terms of WAVELENGTH. As Don said, you want the counterpoises to be close to a resonant 1/4 wavelength on each band Six feet is small on 80 or 40 meters, but it starts becoming significant on the higher bands. For example, on 10 meters you only need an 8-foot counterpoise. Hooking other counterpoises only two feet from the high-impedance far end will drastically detune it. I doubt if you can get it to show any sort of resonance on 28 MHz. It may well be an issue as far down 14 MHz as well. If you want to band-hop as fast as your KAT100 can switch between them, arrange separate counterpoises on the higher-frequency bands. Instead of running outdoors, try running them along your baseboards with each one going directly to the rig. Another way to deal with that is to use a small single-ended matching network just like you'd use with any end-fed antenna except the 'hot' lead to the transmitter connects to the transmitter case or ground, of course. Then you adjust the network for maximum current into the counterpoise for the band you are using. SWR is not any concern, just maximum RF current. How do you measure the current? Put a small flashlight bulb in series with the counterpoise temporarily to tell what adjustment produces the best current. Unless the counterpoise is very short in terms of wavelengths, one adjustment will be FB for an entire band. Once you've found it, short out the bulb to keep it from burning out. Often a watt or less will produce a lot of light! Once you know the settings you can not them so you can simply reset the controls to the right places for each band. For a matching network, a simple tapped coil and series variable will work. Some companies make these circuits all built up and ready to hook up, complete with a wiggly-meter RF current indicator. MFJ's "Artificial Ground" is one. Ron AC7AC _______________________________________________ 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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On 11-02-05; Ron, AC7AC wrote:
"For a matching network, a simple tapped coil and series variable will work. Some companies make these circuits all built up and ready to hook up, complete with a wiggly-meter RF current indicator. MFJ's "Artificial Ground" is one." *FYI....If you enjoy melting solder, take a look at the Ten-Tec RF Counterpoise, **model 1251.** It's a kit and if you enjoy melting solder you may find the construction superior to "brand x". Of course, your mileage may vary. Carry_on KXBill * _______________________________________________ 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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