[AMRadio] LINK COUPLING)

[Larry Szendrei]

On 9/19/13 9:11 PM, W5AMI wrote:
> Hi Larry,
>
> Well, the wire I had, which is now just a messy bundle, was a half 
> wave dipole cut for 75/80 meters, fed direct with 450 ohm ladder line 
> from the tuner.  I have two large ceramic feed thru insulators to 
> bring it into the house, and the home brew tuner is mounted on the 
> wall right where the insulators are.
>
> I could tune anything for 160 to 20 meters with pretty good success.  
> 20 and above was very touchy, since the coil and caps are so big 
> (inductance & capacitance).  I'm sure on 160 it was not very efficient 
> due to the antenna being cut for 80 meters, but it would tune just 
> fine.  80 and 40 were a breeze.  If I went to 40, I didn't even have 
> to change taps on the coil, just tweak C1 a little.
>
> Now that my old antenna is down, thanks to my 200+ lbs great dane, I 
> am going to put up a 1 & 1/4 wave doublet and feed it the same way.  
> Been wanting to try one for a long time, and my dog has now given me 
> reason to do so.  I have lots of property here on the farm, but also 
> lots of trees in the way.
>
Thanks, Brian,

The reason I asked is I have a similar tuner I had built, except instead 
of link-coupling I feed the unbalanced 50 ohm input to a tap up the coil 
on one side or the other, as Dn K4KYV described in a recent post. I can 
tune either my 160M dipole or 80M dipole (both fed with open wire line) 
from 160M through 40M with that tuner, but like you mention, the coil 
has too much parasitic reactance to tune the higher HF spectrum, in this 
case 20M or higher. This isn't a big deal for me, since I have a 
Cushcraft A3 for 20M, 15M, and 10M, as well as another tuner (50 ohm 
balun on low-Z side feeding a balanced pi network which feeds the OWL), 
and am able to tune at least up through 17M with that system. I could 
wind a smaller coil for the 1st tuner for the higher bands and make them 
changeable if I was so-motivated, but since I have other ways of 
radiating a signal on 20M and above, I'm not ;-)

73,
-Larry/NE1S