I'd say the rig was used for swl purposes, and the owner was trying to get
maximum sensitivity out of it, although questionable how much more, if any.
I seem to remember this mod on one of the swl lists/sites.
David
Wd9cmd
----- Original Message -----
From: "Jim Shorney" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Wednesday, December 03, 2008 9:56 PM
Subject: Re: [Drakelist] Drake TR7 and R7
Hi John,
On Wed, 3 Dec 2008 21:06:24 -0000, John Stringer wrote:
1. The RIT on the R7 should be about plus or minus 3khz It has been
modified
to plus or minus 200hz. Yes 200hz. Why?
Probably the same reason I reduced the range on the RIT control in my
HR2510. WHen using the RIT as a "fine tune" control, you're not usually
going more than a couple of hundred Hertz, at the most. There's really
not much need for 6 KHz of range, and reducing the range makes it
easier to fine tune with that tiny knob.
2. An SO239 has been installed on the back panel
A. Connect the antenna to the SO239 so bypassing the Antenna Switch.
B.Install a jumper between the SO239 and the spare RCA socket and put the
antenna into its proper RCA connector so routing the antenna via the
Antenna
Switch--in other words the normal way.
That's an interesting one. My fisrt thought is to allow the user to
bypass the antenna selector, as the splitter has some loss through it.
There is theoretical 3 dB dignal drop through any two-way splitter
(half the signal goes to each port), plus circuit losses, which
typically adds up to 3.5 to 4 dB in the real world. However, I was
looking at the schematic just a couple of nights ago, and it appears
that the splitter circuit is bypassed when the antenna selector is set
to Main/Alt ... which would make sense. This would leave and small
(probably insignifigant) loss in the cables and switch itself.
In light of that, the only thing that really makes sense me is pehaps
the owner wanted to use the antenna selector to feed two other radios
other than the R7 from one of two antennas, at the same time the R7 was
being used on a third antenna. Or maybe that it was an easy place to
put a real antenna connector, and the owner elected to bypass what was
essentially an unused feature when the radio was used in that
configuration, or the isolation between ports wasn't sufficient for
some reason.
Maybe someone else has a more obscure reason?
73
-Jim
NU0C
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