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public:blog:antenna_changes [05/07/26 16:57 BST] – [Antenna Changes] johnpublic:blog:antenna_changes [07/07/26 10:04 BST] (current) – [Antenna Changes] john
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 ====== Antenna Changes ====== ====== Antenna Changes ======
  
  
 Now that I'm turning my attention back to QRP I decided that the antenna I've used for many years - an Inverted-L held up by (over the years) different supports, and currently a 10m SOTA-pole with the top few sections removed - tuned against a mess of radials and ground rods by a CG-3000 Auto-ATU - was due for a change. Now that I'm turning my attention back to QRP I decided that the antenna I've used for many years - an Inverted-L held up by (over the years) different supports, and currently a 10m SOTA-pole with the top few sections removed - tuned against a mess of radials and ground rods by a CG-3000 Auto-ATU - was due for a change.
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 +=== ===
  
 The Auto-ATU needs "a few watts" to trigger a re-tune on a new frequency. Occasionally it'll work with 5W but not consistently, and certainly won't re-tune at anything lower than 5W. This means occasionally having to give it a carrier from a QRO radio to re-tune before switching to a QRP radio.  The Auto-ATU needs "a few watts" to trigger a re-tune on a new frequency. Occasionally it'll work with 5W but not consistently, and certainly won't re-tune at anything lower than 5W. This means occasionally having to give it a carrier from a QRO radio to re-tune before switching to a QRP radio. 
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 This removes the need for a good, low impedance ground connection and simplifies things. It also means "more wire" in the air for each band. This removes the need for a good, low impedance ground connection and simplifies things. It also means "more wire" in the air for each band.
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 +===== First Step - EFHW for 30m  =====
  
 I removed the Auto-ATU and put my nanoVNA on the current antenna/ground feed point to see what I've got now (a totally random length). The first resonance/low SWR is around 3.2MHz. That means a 1/4 wave at 3.2MHz or around 23m. I can perhaps squeeze a little more wire into the space but I'll accept that the new antenna overall length will be limited to "around 23m". I removed the Auto-ATU and put my nanoVNA on the current antenna/ground feed point to see what I've got now (a totally random length). The first resonance/low SWR is around 3.2MHz. That means a 1/4 wave at 3.2MHz or around 23m. I can perhaps squeeze a little more wire into the space but I'll accept that the new antenna overall length will be limited to "around 23m".
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 No need for an ATU (auto or manual). No need for an ATU (auto or manual).
  
-==== Next step - 2 bands 30m/40m ==== +===== Next step - trapped EFHW for 2 bands - 30m & 40m ===== 
  
 I made a trap for 10.1MHz and added it to the end of the current antenna, then added wire to make a dual-band 30m / 40m antenna. That should cover my normal CW operations for a while. I made a trap for 10.1MHz and added it to the end of the current antenna, then added wire to make a dual-band 30m / 40m antenna. That should cover my normal CW operations for a while.
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 +~~DISCUSSION~~