[TenTec] RE:INRAD Omni6+ mod

[Robert & Linda McGraw K4TAX]

This discussion peaked my interest in "what is the detected frequency
response" of this radio.  I just completed some simple measurements using my
HP8656B generator modulated externally by a broadband pink noise source.  In
looking at the Audio Out jack on the back and the speaker out signals with a
1/3 octave spectrum analyzer it was easy to see the response with the stock
Tentec 2.4 KHz filter.  What I found was a response of 500 Hz -> 2.5 KHz +/-
3dB. Both LSB and USB gave the same results.  This confirmed that the PBT
alignment is correct.  The 400 Hz signal was down some 9 dB and the 3.1 KHz
down some 15 dB.  About what I expected but a good bit different than the
ARRL report.

I didn't measure the transmit frequency response but I will endeavor to do
that in the next day or so.

It's not Hi-Fi.........it's ham radio.

73
Bob, K4TAX


----- Original Message ----- 
From: <KD7EFQ at aol.com>
To: <tentec at contesting.com>
Sent: Wednesday, May 26, 2004 12:57 PM
Subject: [TenTec] RE:INRAD Omni6+ mod


> Hello, The Omni 6+ design was primarily for optimum dynamic range /
rejection properties. I was told by Ten Tec that they designed it with good
communications grade audio response, but the QST review shows that the audio
passband is rather restricted for SSB operation compared to its competitors.
the FT 1000mp audio range was somewhere around 2200hz where the Omni 6+
stock was only around 1600 hz.
>
>  George at INRAD changes some audio passband capacitors and a resistor in
the notch filter circuit, along with recommending the wider 2.8 IF filters
for better SSB audio fidelity. I have done this mod and found it
satisfactory, however, for SSB ragchew audio fidelity, I've found that my
Brand K TS-570 does better audiowise on SSB, and it is stock.
>
>  You just have to decide which is more important to you. If you're
primarily a CW op, I wouldn't bother with it. If SSB ragchewing that is
pleasant and comfortable to listen to is your bag, you might try it, (or
another radio, say a Jupiter) but I've found the difference not to be as
"Dramatic" as I was expecting. 73. Todd
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