[HCARC] Antenna Tuners

[ALoneStarYank at aol.com]

MFJ uses young people, usually college kids off during the summer, to  
assemble their products. In many of these tuners they don't tighten the screws  
and nuts properly and the soldered joints are sometimes questionable. I, 
myself,  use MFJ tuners for field work only after I've given them the "once  
over".
 
There are several things about using tuners:
 
When using a tuner on 160 meters, you need to de-rate the tuner wattage by  
at least 2/3. A 300 watt tuner can only handle 100 watts (barely) on 160  
meters or arcing can occur.
 
When buying a tuner, look at the switches very closely. The flimsy  
wafer-type band switch (also called a tapped coil switch) which MFJ  uses, needs to 
be replaced with a heavier duty ceramic switch  or it will burn out.
 
NEVER, NEVER, NEVER  change your tapped coil  switch selection with RF 
flowing thru it. (or any other switch for that  matter) It will cause the 
contacts to arc and might even blow your rigs  finals.
 
 
Before MFJ took over Ameritron and Vectronics, they had decent tuners, as  
did a few others.  Palstar tuners are also a great buy.  The MFJ  971  tuner 
should be avoided when you use anything over 10 watts although  it can 
handle 100 watts. The reason is the cheap design. The two knobs that are  
screwed onto the capacitor shafts do not have insulated couplings so RF is  
directly connected to the set screws and touching them during operation can  cause 
rf burns! I wrote to MFJ about 15 years ago and their reply was: "So don't  
touch the knobs!". 
 
At home, I use an "Amp Supply AT1200" which hasn't been made in about 20  
years.  You can't kill it... lol 
 
If built properly, the Heathkit tuners are great, so are the Johnson/Viking 
 tuners although some have no metering. Kenwood has a nice tuner, I believe 
the  model is AT-230.
 
I shy away from auto-tuners. 
 
Bob W2IK