[TenTec] TenTec Digest, Vol 158, Issue 27

[Rob Atkinson]

> And we should also build or own cars because we can all build better cars
> than what GM and Ford (etc.) are selling us.  ;-)
>

That's a specious comment.  Cars are not antennas or impedance
matching networks.


> Rob, as perfectly correct as your email was, it is no longer a viable
> solution for 90% of the hams out there today.  A couple of guys might
> actually manage to find what they need at hamfests, but there aren't enough
> components available to support the masses.
>

 You are equating mass production needs with a few people homebrewing.

> To categorically claim all Palstar and all MFJ matchboxes are bad is not
> fair either.

"fairness" is irrelevant.  I'm writing about building a better piece of gear.

By the way, I have seen their products and in my opinion they are
poorly constructed and a ham can do better homebrewing with old parts
purchased second hand.  Period.


> They were designed for the kind of antennas most hams use today, not for the
> openwire antennas of yesteryear.
>

Antennas and feedlines have not changed substantially.  Not on HF.


> In order to have a good match to an openwire fed antenna, you need two
> things:
> 1). A means of matching
> 2). A means of managing the Common Mode Current (CMC) which sometimes can be
> hefty.
>
> The old Link-Coupled tuners Rob speaks of were great and inherently had an
> advantage in coping with CMC.  But there are way now days to do it using
> today's products.
> It is only a huge challenge if you insist on doing it with 1500w.
> It's all about choice of balun and where you physically locate it.
>

Forget baluns.  they stink.  They become reactive and lossy in 99% of
cases.  They are only useful if you have an engineered system with one
where they transform a resistance and for that to happen you have to
stay on one frequency.  If a ham does that they are fine.   Have a
nice life on your frequency.

Also, network designs have not really advanced apart from superficial
controls, switching relays, motorized additions etc. to create an
automatic tuner.  Link coupling is still the best way to go for a
transition from unbalanced to balanced and vice versa.

Further, you imply a high power capability tuner is not necessary for
low power.  On the contrary, it is even more important because high
power capability in the entire antenna system including feedline
results in better efficiency and lower loss, which is very important
for low power.

> The recommendation for 4:1 balun (as the only balun) under any circumstances
> is bad advice.  The balun should always be a 1:1 current balun.  Of course
> if you have an older symmetrical matchbox (Johnson or Annecke) you don't
> need any balun at all.
>

This is correct except that with a link coupled design you don't need
any kind of unun or balun ever.

> Using the 1:1 current balun does not prohibit also using a 4:1 balun as a
> transformer, in addition to the 1:1, but it should only be switched in when
> absolutely necessary.
>

Throw it away.  You are always better off using a method that does not
require the use of a balun.

Okay enough.  I have things to do.  You all do what you want and learn
the hard way like I did, I heard that hams today don't care what they
have for a load as long as their "automatic tuner" can keep their
plastic radio from folding back.

73
Rob
K5UJ