What is the advantage of Auto-ATU's w/ motorized Air Caps vs. N7DDC type auto ATU?

[Naysayer]

I only recently got an auto-ATU to learn about. Not the miracle I hoped for it has it's uses.

I see auto ATU sections removed from HF Base Stations being sold on eBay. They typically have motorized variable air caps coupled with toroids larger than I would associate with a 200w max limit on an n7ddc type unit. What is the typical use for such a parted-out unit and why opt for one over an N7ddc type auto tuner?

neil, NYC

 

[nomadradio]

The one thing a parted-out tuner is good for is to replace the broken one in the buyer's radio.

A variable-element tuner can zero in on a finer impedance match than one that tunes in steps with relays.

Drawback for the variable-element tuner is moving parts and complexity. The N7DDC approach is mechanically simpler and also simpler to manipulate with a microcontroller.

Using relays instead of variable caps and inductors is cheaper and lightweight compared to roller inductors and air variable caps.

73

 

[Naysayer]

Thanks for the explanation on that. I did not understand why there were so many auto tuner sections listed for sale. I only recently got an auto ATU to play with and it gave me a new appreciation for my old and heavy, T-Match.

 

[SuperLid]

Thanks for the explanation on that. I did not understand why there were so many auto tuner sections listed for sale. I only recently got an auto ATU to play with and it gave me a new appreciation for my old and heavy, T-Match.

I have several Icom AH-x tuners and an LDG. The Icom's are great, but limited to Icom radios and the LDG sucks. So, I was considering the Chinese N7DDF and consulted a friend, who told me what a POS it is. I read the Eham reviews, which cancelled any thoughts of owning one. I also have the MFJ -998RT, but have yet to power it up. Motorized are VERY slow.

 

[nomadradio]

A fast motor makes it too easy to overshoot a peak.

73