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Author Topic: W5DXP no-tuner antenna  (Read 1320 times)
NI3S
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Posts: 67




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« on: July 20, 2013, 07:24:16 PM »

I am thinking of building one of these, mostly because the stuff is laying around here and I have had good success with a previous doublet. 

http://www.w5dxp.com/notuner.htm][url]http://www.w5dxp.com/notuner.htm[/url]

Ideally relays would switch the lengths of ladder line.  Any 4 pole relays that have been used with good results?  DPDTs could always be paired if that is a better solution.

Secondly, the Balun design uses RG-400.  That seems a bit difficult to locate and kind of lossy.  Is there another design or coax that can be substituted? 

Thanks and 73,

Bill
NI3S
 
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W5DXP
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« Reply #1 on: July 21, 2013, 07:27:54 PM »

Ideally relays would switch the lengths of ladder line.

When I first implemented the idea, I obtained samples of 12v OMRON LY4 4PDT relays and they worked well at 100 watts. They have an anti-arcing plastic shield between contacts. I ran them from my 12vdc backup battery during AC power outages.

When I bought my SG-500 amp I went to larger 24v PB KUP DPDT relays that I got for $2 each from an electronic surplus store in Phoenix. I ran them from a 24vdc power supply.

After a couple of AC power outages during which I lost my 24vdc and antenna tuning ability, I started using the knife switches instead of setting up a 24vdc backup battery.

Quote
Secondly, the Balun design uses RG-400.  That seems a bit difficult to locate and kind of lossy.

I chose RG-400 for its high voltage characteristics - available from The Wireman.

http://www.thewireman.com/coaxp.html

RG-58 can be used as seen from the following chart. With the relatively short length of coax used to wind the balun, I wouldn't worry about losses.

http://www.karinya.net/g3txq/chokes/
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
NI3S
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Posts: 67




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« Reply #2 on: July 22, 2013, 05:36:01 PM »

Cecil, thank for the guidance. 

One more  question if I may, can I roll up or fold up or compact in some other way, the longer pieces (4', 8' 16') of switched feedline with out effecting performance? 

Thanks,

NI3S
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W5DXP
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« Reply #3 on: July 22, 2013, 07:00:14 PM »

One more  question if I may, can I roll up or fold up or compact in some other way, the longer pieces (4', 8' 16') of switched feedline with out effecting performance? 

Sorry, all ladder-line must be kept about four inches away from all other ladder-line. I formed the long sections into a spiral that honored that rule.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
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