[Hallicrafters] RTMA Dummy Antenna needed for alignment?

[Glen Zook]

It depends on the TV balun as to whether or not it
will make it down into the HF region.  Those baluns
made for use with cable television systems (and most
baluns available these days are made for use with such
systems) have to make it down to at least 5 MHz
because of various signaling that is used in many such
systems.  Frankly, it has been my experience that most
TV baluns make it down to the 160 meter band and even
into the AM broadcast band.

For the article on using TV baluns with amateur radio
equipment that appeared in Electric Radio a while back
go to

http://k9sth.com/Page_2.html

The article is the 16th link under the heading
"Articles".

Although the usual 4:1 matching is not "perfect", it
has been my experience that using one with the old
3-terminal antenna connection receivers usually makes
a "night and day" improvement in sensitivity when
antennas fed with coaxial cable are used.

Yes, a separate antenna tuning unit between such a
receiver and a coaxial cable fed antenna will allow a
better match between the antenna and the receiver. 
When I first got the Collins 75A-1 receiver (s/n 4)
going I found that having such a tuner improved the
sensitivity from absolutely dismal to extremely good. 
However, whenever changing bands (and even within some
bands) I had to adjust the tuner for best performance.
 Then I tried a TV balun and that worked very well and
did not require any tuning when I changed bands. 
Depending on the band the improvement between the
antenna tuner and the TV balun ranged from no
difference to a very slight difference when measured
with a signal generator with a well calibrated
attenuator.  But, considering the fact that the TV
balun required no physical effort the very slight
difference in sensitivity was immaterial.

The article describes the effect that using a TV balun
had on various receivers.  In every case the TV balun
helped.

Glen, K9STH


--- jeremy-ca <km1h at jeremy.mv.com> wrote:

If the input coils were designed for a high impedance
antenna and a low impedance generator was placed
across them then the excessive loading would give
erroneous readings. You can notice the effect when
using a coax fed dipole; in many cases the signal drop
is rather dramatic.
 
If the dummy load isnt available, missnamed since it
is an early attempt at a broadband matching device,
isnt available then wind a 9:1 balun on a FT50-43
ferrite toroid. The old TV baluns are pretty much
useless below 20MHz if you want accurate readings.









Glen, K9STH

Website:  http://k9sth.com


      ____________________________________________________________________________________
Be a better friend, newshound, and 
know-it-all with Yahoo! Mobile.  Try it now.  http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ