[Kenwood] ts850 rf feedback

Mon, 5 Aug 2002 20:21:34 -0400

Hi All,

This information may be helpful, and can be found at www.mods.dk follow
links to Kenwood then TS850... This site and www.qsl.net/k0bx have excellent
info to fix bugs in the radio... both have been very helpful to me.

QUOTE:

A common problem when using a KAM-Plus multimode with the Kenwood TS-850 or
TS-450 occurs when the KAM-Plus is coupled to the Accessory-2 socket on the
back of the transceiver, producing noticable distortion of the transmitted
audio when using the microphone in SSB mode..

The problem is easy to cure by disconnecting the Accessory-2 plug from the
back of the tranceiver, but this meant moving the transceiver around every
time one wished to operate on SSB..

The problem is caused by the input sensitivity of the rear Accessory-2
socket being set to high, so that it picks up very low level noise from the
KAM-Plus and associated computer wiring, this mixes with the microphone
signal, to produce the distortion.

The cure is to reduce the input sensitivity of the radio, thus reducing the
chance of distortion, also it goes without saying that the output from the
KAM-Plus must be increased to compensate for this.

With both the TS-450 and TS-850, adjusting the input sensitivity is straight
forward and the transceiver manuals show you the appropriate control and its
location.. This is in both cases VR18 to be found on the main board of the
radio,(refer to manual) in practice I found that it was best to adjust this
control fully counterclockwise..

Then we need to adjust the output from the KAM-Plus by varying potentiometer
R28 and setting removable link (K9), this link is factory set on one post
only, (in the open position)!! this should be connected shorting the two
posts, thus putting the KAM-Plus into the high output position, and then
potentiometer R-28 is adjusted to give full power out from your HF radio
with very little ALC deflection, when the MIC gain is in the normal
operating position..

Then I am sure you will find that your problem is over, you can now simply
change from digital modes to SSB.. Remember if you have your Beacon
activated to turn it OFF or it could cause a few comments when operating
SSB..

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UNQUOTE:

73, Dean - 8P6SH

----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Sunday, August 04, 2002 9:39 AM
Subject: [Kenwood] ts850 rf feedback

> I am using a TS850 MC60 mike and PK232MBX for rtty.  With the cable
plugged
> into the TS850 acc2 jack from the TNC, there is rf feedback when trying to
> use the mike on ssb.  The only cure to use ssb is to unplug the cable from
> acc2.  I tried ferrite beads and shielding on the cable to no avail.  When
I
> qso VK4SJ and mentioned the rf feedback problem she asked if I were using
a
> TS850 and a MC60 mike before she knew my setup - it must be a common
problem!
>  She said the only cure was to throw away the MC60 mike.  Without the rtty
> cable plugged in, the TS850 audio quality is outstanding and I very often
> receive comments on how good it is.  I looked in the service manual and it
> appears that the TS850 already has adequate bypass capacitors on the acc2
> connections.  I looked in the Kenwood archives and didnt see any
discussion
> of this problem.  Is there any cure other than unplugging the cable or
> throwing the mike away?  73 Bob W7LR in MT          [email protected]
> - - -
>
> Your moderator for this list is:
> Larry Wilson KE1HZ [email protected]
>
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