[AMRadio] BC-610 down=up


James M. Walker chejmw at acsu.buffalo.edu
Thu Oct 27 11:45:15 EDT 2005


Well Mike and group,
The coupler itself doesn't generate TVI! The transmitter that is connected
to
it might, the coupler just pass along the signals that go to it.

The "coupler" was never intended to , tune a dipole antenna, nor an
open wire fed antenna. It was for a base fed "Whip" antenna and the
manual for the SCR-399/499 called out the length of the feed cable
to the base of the whip, and also the length of the whip. If you followed
the manual and provided those lengths, AND also if stationary, provided
the ground system suggested, the coupler worked as intended. As in it
put most if not all of the RF into the wire.

I think most of the stories about generating TVI are bogus, or at least
leaving out all the information about the type of antenna that was being
used. To ease the pain of not knowing about the usage, anyone wanting
to use the BC-939(*), or the TN-339(*) coupler should first read the
manuals for those units.

I have learned that any "hunk" of wire will radiate, if you get the RF to
it.
These units provide the means for that, but they require that the guide
lines for usage be followed.

Jim
WB2FCN

----- Original Message -----
From: "Mike Sawyer" <w3slk at uplink.net>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Wednesday, October 26, 2005 4:28 PM
Subject: Re: [AMRadio] BC-610 down=up


> The way I understand is that the BC-939 was a helluva TVI generator. What
is
> neat is that they used the exact same thing for the BC-610's younger
> brother, the T-368. Only difference is they put it in a battleship grey
box.
> Mike(y)
> W3SLK
>
> ----- Original Message -----
> From: "Todd, KA1KAQ" <ka1kaq at gmail.com>
> To: "Discussion of AM Radio" <amradio at mailman.qth.net>
> Sent: Wednesday, October 26, 2005 9:23 AM
> Subject: Re: [AMRadio] BC-610 down=up
>
>
> On 10/26/05, W7QHO at aol.com <W7QHO at aol.com> wrote:
> >
> > In a message dated 10/25/05 8:18:51 PM, chejmw at acsu.buffalo.edu writes:
> >
> > > Actually,
> > > The BC-939 (*) handles an end fed long wire, the recommended length
for
> > > 2 - 18 Mhz is 44 feet. That number changes to 77 feet for 160 meters
and
> > > works quite well.
> > >
> > Actually,   a 44 (or 77) ft antenna is not a very "long" wire even at 18
> > MHz.
> >   The term is usually used to describe wires measured in wavelengths as
> > opposed to feet and inches, see various ARRL and other antenna books.
>
> Apparently Hallicrafters and/or the military considered it long enough
> to qualify since the 3 position switch on front of the tuner has 'long
> wire' specifically listed in the center position. My guess is that
> they considered any random length beyond what would qualify as a
> 'whip' to be a long wire, perhaps in the spirit of the original term.
>
> The odd thing about my A model is that the lower vacuum cap has been
> removed and replaced with an air capacitor, screwed to the base with
> heavy wire soldered to each of the two clips. It resembles a moderate
> sized air variable but with only 5-6 stationary plates. Looks to
> either be factory installed or later upgraded. Haven't had time yet to
> investigate the value or rating.
>
> Very well-built piece of equipment, even if it has limited utility.
>
> ~ Todd/'Boomer'  KA1KAQ
>
>
>
> --------------------------------------------------------------------------
------
>
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