[GreenKeys] CRT Question

[Ralph Mowery]

By doing that you do get a sharper display.  However the tuning may not 
really be as good as the 'banana" tuning.  By adding sharper filters, they 
may not be tuned to exectally the same frequencies as  the mark/space
filters.

  If you have the time and equipment, one way to do it is to send in a mark 
tone and look at it across the filter with a voltmeter or scope and see 
where it peaks at.  Then take a grease pencile and mark the trace on the 
tuning scope tube, then do the same for the space tone.  This gives you the 
tuning points provided the transmitting station is sending out tones that 
are matched to your filters.  All this is assuming that you have a TU that 
has seperate mark and space filters.

----- Original Message ----- 
From: "Lester Veenstra" <lester at veenstras.com>
To: <greenkeys at mailman.qth.net>
Sent: Friday, August 21, 2015 9:46 AM
Subject: Re: [GreenKeys] CRT Question


In the Altronics Howard Model L they took the channel filter (Mark and space
filters) and passed them to a dual channel amplifier, driving the
oscilloscope plates, However, across the plates were an additional high q
tank (the usual 88 mhy torroid based). Since this was a very high impedance
point (the scope defection plates), the high Q allowed a very narrow
bandwidth. Therefore, instead of the usual sloppy bananas tuning display, he
was able to present a clean crossed line display that allowed unambiguous
tuning.


Lester B Veenstra MØYCM K1YCM W8YCM