[TenTec] Answers to some of your questions

[pywacker@fuse.net]

Stuart, thanks for the info. Concerning the Key Pad, I placed a unknown
composition core brand name KG right where the cable plugs into the key pad
and 5 cores where the cable plugs into the rig. Four of the cores are
approx. 1 inch in length and clamp tightly around the cable and one core
brand name TOKEN has one turn of the cable through it. It is about 1 1/4
inches in length and can clamp almost snuggly around RG8U coax, again the
important factor, I do not know the composition; However whenever I have had
to use a core to eliminate RFI this has been the core of choice. Debco
Electronics in Cincinnati sells both brands and in one size only.

I do have plenty of  Toroidal cores made of 43 and 77 material but did not
use them for the cable. They are the circular donut shaped type, non-split.

73 de KE4WY Jim


----- Original Message -----
From: "Stuart Rohre" <rohre@arlut.utexas.edu>
To: <pywacker@fuse.net>
Cc: <tentec@contesting.com>
Sent: Wednesday, April 18, 2001 2:51 PM
Subject: [TenTec] Answers to some of your questions


>
> I think Carl answered the why of not keeping the bandwidth center
frequency
> fixed as you change SSB widths.  Another way of saying what Carl did is,
you
> would go below zero frequency under some conditions and see the aliasing
> frequency folded down from the upper frequency ranges.
>
> Now as to floating a speaker.  That is an excellent way to REDUCE RFI.
> Another reason, is they may be using a bridged audio amplifier, saving the
> cost of a transformer, and distributing the power load to more than one
> active device, thus reducing localized heat sources.  It is not too hard
to
> run a zip cord to an external speaker, or even a shielded cable, the main
> thing is to avoid grounding to the case of the radio, transmatch, etc.
>
> If you have too many things external to the radio also grounded to station
> ground or AC ground, (case ground), you can pick up computer hash thru
> ground loops, and pick up RFI, etc.
>
> Ten Tec rigs traditionally have been able to operate into SWR greater than
> 1:1, without folding back power until you get above 3:1.  Mine do well
> without use of a transmatch over the whole of the phone bands.  Any
> transmatch only introduces losses.  I like to use resonant antennas, and
> have fewer losses.  There are good design ideas for either approach, to
> always have a transmatch, or not.  It all depends on how the individual
uses
> their radio, their antenna farm, etc.
>
> It would be useful to describe to the list where you put the choke core to
> eliminate your RFI from the keypad.
> Was it close to the pad itself, or close to the rig, or somewhere along
the
> cable, and how many turns?
>
> Few Yaecomwood noise "limiters" really work on the noises I have wanted to
> fix; that is a "ham holy grail" that may never be possible to overcome
> without a lot of extra hardware.  Each of us has our own hearing, and thus
> audio is best shaped by equalizers for our own transmit and receive
> perception of what sounds "good".  Often hams use way too high a fidelity
> earphone for receivers, and hear the on board rig computer.  The best
radio
> headphones I have are NOS 1955 vintage double magnetic phones of 15,000
ohms
> impedance.  They are so sensitive, you do not need to turn audio up, and
> amplify the low level computer stuff.  Also, their fidelity is limited to
> the voice bands, for more intelligibility. For cushions, since the
original
> rubber snap on covers are not made, one can go to a drugstore cosmetics
> dept. and find disks of sponge material.  cut a hole in the middle of two,
> and apply double sided scotch tape to the ear piece of the mil phones.
> Stick the flat sponge pad onto the hard rubber of the earphone, and they
> will be very comfortable once you adjust the head band to your liking.
The
> cosmetic powder cushion pads come two or four to a package, thus you can
> replace them at low cost when they wear over time.  Keep the spares out of
> sunlight, and tube light range to preserve the sponge spares until use.
>
> GL and 73,
> Stuart K5KVH
>
>
>
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>



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