[TenTec] Inrad #762 Info and Availability

[Bill Tippett <btippett@alum.mit.edu>]

W4CAK:
 >Thanks for your input with all the backup info regarding the 500 HZ
roofing filter.  I will just use the 1KHZ filter from now on when trying to
copy weak signals. I went to Inrad's website and did not see the 762 filter
listed for sale yet.

I wrote:
>It IS for sale now but you may have to send them an E-mail.
I suspect the price is around the same as their other filters.
Last I heard deliveries should begin late Summer but I could be
wrong.

        I got a note from George W2VJN about Inrad's #762 filter.  This is a
completely assembled #352 600 Hz 4-pole filter which is compatible with
Orion's 1000 Hz slot.  He has some in stock for $80 but says they are going
fast.  It is not on Inrad's webpage yet but will appear when his Webmaster
updates the site.  The filter's response curve is nearly identical to this
one (the #350):

http://www.qth.com/inrad/graphs/350.gif

except that it is centered on 9.001500 MHz and has 6dB BW of 640 Hz.

        According to Rob Sherwood:

> At 5, 10 and 20 kHz, there is no significant difference between the
> stock 1.0 kHz Ten-Tec filter and the Inrad filter.
> At 2 kHz spacing, the improvement is on the order of 6 to 7 dB.
> At 1 kHz spacing the improvement is closer to 10 dB.
> There is some strange hysteresis of a couple dB, as you change the level
> around.  The IMD does not act exactly as one would expect.
> I am guessing the digital AGC is doing strange things, causing the
> hysteresis.
>
> The insertion loss of filters #2 and #3 are identical to the Ten-Tec 1.0
> kHz filter.

By "filters #2 and #3" he means my SMT cap version of #352 and N1EU's
NPO disc cap version.  Filter #1 was made by someone else and was
defective, giving all of us some heartburn until #2 and #3 were tested.
From my website notes about the #352:

>       11.  Everything functions perfectly in my unit.  I have full DSP
range and full Pitch range for both CW passbands.  My filter is very
slightly offset (I can correct by setting PBT = 50), but this
is not enough to worry about in a 640 Hz filter (BTW I measured
the same bandwidth George did).  If you previously had the 500
Hz position enabled, you should disable it now. I previously sold
my Inrad 400 Hz since the #352 is a much better solution
because of the IMD problems the 500 slot introduces.  I'm
keeping my 250 for the time being, but may sell it also.

                                                73,  Bill  W4ZV 

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