[RTTY] MARK V USERS-Filter Selection

[Jerry]

Hi Again

	Regarding other radios for RTTY, I have played with the PRO-3 for about an
hour, and of course read Don's comments. Remember Don can beat us with any
radio you can think of. The only time I can beat Don is when he is called
to work. 

	As far as I can see the PRO-III is not much different than the PRO-II,
with two exceptions. Of course there are cosmetic effects and changes in
the operating software, but essentially the changes are the 15 KHz(!!) wide
roofing filter and a new preamp/mixer design from the IC-7800.  These
changes are to answer the basic weakness of the IF DSP designs ranging from
the TS-870 through the IC-Pro series of radios. That is the front end
overload before the bandwidth limiting elements. The front end can saturate
form signals well outside the passband of the IF DSP, causing loss of weak
signals and frustration to the operator under contest conditions. Under
non-contest conditions of course the radios are very very good.

	The ORION handles this problem, being a ham band only radio, by providing
multiple front end filters at the 8-9MHz first IF.  With a 500 hundred of
250 HZ filter even a relatively cheap one the DSP works very well. (See
John's , ON4UN, write up in the 3830 reflector. 

	I handle this dynamic range problem by not using the preamp in the MK-V
Field. In fact when possible use additional attenuation above and beyond.
Changed the attenuation in the mark-V to 10, 20 and 30 dB. by changing the
resistors. Did it the same time when adding the 5 KHz roofing filters. With
the roofing filter in place, the Mark-V is a poor radio for listening the
40 meters broadcasts. When I want to SWL use the second radio in the MK-V.
It's audio performance is much better.

	Never worry what the "S" meter reads, as long as copy is above the noise
level. My problem is staying in the chair. Lose more contests by fatigue
than by radio performance. Such is life, I still enjoy RTTY contesting, and
while it nice to get near the top of the list, at least am participating.

	A final note: Th IC-7800 can-not receive on the second receiver while
xmitting on the first!! Hell, with two $2000 dollar radios can do a true
SO2R.  Too bad. Maybe someday the manufacturers will "use" there radios
before they are put into production. 

		73 de Jerry NO2T