[RTTY] External DSP devices

[Don Hill AA5AU]

Bob is correct on this one.  An external DSP audio filter is not going to help
you.  I use the JPS NIR-12 (no longer available) on both radios and the only
thing it does is make the audio sound nice to my ears (and maybe the sound
card).  I would probably decode just as well without them.

I did want to make one comment on the Kenwood TS-570.  I used one as a second
radio in a CQWW RTTY contest a few years ago and the 250 hz filter did not work
well at all.  Nearby stations killed the AGC and made it nearly impossible to
copy weak signals.  The Kenwood TS-870 does not have this problem and has
excellent filters.

But nothing I've used so far compares to the Icom IC-756PRO III.  This appears
to be the ultimate, affordable, RTTY radio with it's Twin Passband Filter.

I hope to put all three of my TS-870 radios up for sale in the foreseeable
future so I can purchase a second (and possible 3rd) PRO III.  I still love the
'870 and it is my main radio on 10, 20 and 80 meters in RTTY contests, but I
really want a band scope on both radios.

73, Don AA5AU

-----Original Message-----
From: rtty-bounces at contesting.com [mailto:rtty-bounces at contesting.com] On Behalf
Of Robert Chudek
Sent: Sunday, January 29, 2006 10:00 PM
To: rtty at contesting.com
Cc: k8jwt at adelphia.net
Subject: Re: [RTTY] External DSP devices

Jacob,

An external audio DSP unit will help fight some interference, but it is not the
right answer to your problem. I have the Timewave DSP unit, but it is a
disappointment for serious RTTY contesting.

What you really need is a radio that provides selectable filters of 500 Hz or
tighter. If you're hearing RTTY stations 2.5 KHz away, these signals are
desensing your receiver by applying excessive AGC. It's the "FM principle". The
loudest station captures the radio and you (your decoder) can't hear the weaker
stations.

One radio that is relatively inexpensive that works well on RTTY is the Kenwood
TS-450SAT. Also, the TS-690SAT is the same radio but includes 6 meter coverage.
You can install optional 500 Hz (or 400 or 270 or 250 Hz) filters in either
transceiver. The filters work on both CW and RTTY. In addition, the radio has
true FSK built in, so you eliminate the AFSK issues. The current product in this
line is the TS-570.

I might sound like a Kenwood salesman, but I know this radio because I have a
TS-690SAT and have used it on RTTY. I have not used the TS-570.

These transceivers come up on eBay from time to time and seem to sell for $400 ~
$600 depending upon the condition and options. As a matter of fact, there's a
TS-690SAT on eBay right now, Item 5860705398 as well as a couple of 450's.

There are probably other lower cost radios that provide good RTTY capabilities
too. But this is the one I can tell you about first hand.

My opinion is save your money on the external DSP unit and put it toward a
second rig (or an upgraded rig)!

73 de Bob - K0RC


* * * * * * * * * * * * *
Message: 7
Date: Sun, 29 Jan 2006 19:57:39 -0500
From: "K8JWT" <k8jwt at adelphia.net>
Subject: [RTTY] External DSP devices
To: <RTTY at contesting.com>
Message-ID: <000301c62538$2b492cd0$6800a8c0 at K8JWT>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original

I am looking into buying a external DSP device for contesting as my Yaesu FT-840
is crappy on SSB/RTTY as I can hear stations as far as 2.5KC away from me.  Was
looking at the MFJ-784B I think it is as it is $200.00 cheaper than the TIMEWAVE
DSP-599z.

So was wondering if anyone has used or is using one of these devices, the MFJ
that is...

Jacob Tennant - K8JWT
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