I have a 253 Auto coupler and MFJ 989B. The MFJ998RT in the shop for
repairs from abuse. Non of these tuners will tune 160M on their own.
Each of these I had to add an inductor L network for 160M. Everyday I have
to retune my 99 foot inverted L, unlike 80-10M dipoles that I have had in
the past. This L network is a hairpin coil to ground and an inductor in
series with the antenna cause it is short. The Ten-Tec 253 is just a pain
in the output. Shift freq tune, Sun rise tune, Sun set tune, over and over
again.
The beauty of the 99 foot L is that the network can be bypassed with relays
and operate on 80-10 m.
What would I accomplish by adding a 1000pF capacitor to ground for 160M? I
have seen this suggested many times. With the L inductor network the
1000pF cap at the top of the hairpin to ground the cap adjustment on the
tuners inside the shack can now be adjusted to minimum SWR. With out the
cap minimum SWR is around 1.4:1 best it can do.
Put all this on a smith chart? I have know idea what my impedance really
is. All I care is that near 1:1 match in the shack and weather or not I am
getting more than 60% of my signal out. That 60% I have no idea if I am
getting that.
BCI from nearby AM station renders my MFJ analyzer just about useless.
Transmitter reads about SWR 2.5:1 with out the tuner in line.
This is a hit and miss tuning proposition on 160M. Starting to think on
giving up on the inverted L and shunt feed the 50 foot tower thats next to
the house. Something tells me I will have the same problems.
--
Jim K9TF
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|