[TenTec] Ten Tec Omni D, Why so quiet ?

[Richard Detweiler]

Have useing the omni-D  for a long time,  I've fixed a number of them for 
friends in the area too.

I only recently upgraded to the Orion because the OMNI A/C/D has such a good 
receiver it often outperforms most of the current commercial gear out there. 
  Add a DSP and Keyer and you are up with the best.

Three Technical reasons should provide a clue as to why it is quite,

1) single conversion receiver,  Less Mixing, Less noise from the mixing 
products.
2) No PLL circuit, thus no Phase Noise, but a little bit of drift ( about 
1KH in 10 hours ) still good enough for PSK.
3) this is the biggie,  Preselect,  the key to all ten tecs great receivers 
has been the preselect circuits.  Makes the antenna look better to the front 
end and matches it's impedance.  Thus a real sensitive receiver.  Anything 
outside of the passband is attenuated to the first amplifier.

If you have the two Optional filters,  You got a great radio.

Another idea,

If the OMNI A/C/D goes quiet on you and you are not receiving at the same 
'S' levels as before, then look at the antenna input diodes,  A pair of 
them, designed to protect the front end,  Those things will short out after 
a big lightning storm and you haven't disconnected the antenna or switched 
it to ground.

Hope this helps.

Thanks
Richard.

>From: Newberry Gary <gnn01 at yahoo.com>
>Reply-To: tentec at contesting.com
>To: tentec at contesting.com
>Subject: [TenTec] Ten Tec Omni D, Why so quiet ?
>Date: Wed, 18 Feb 2004 11:01:29 -0800 (PST)
>
>
>I hve a friend that's a recent convert to Ten Tec rigs
>mainly because of their quiet receiver. I hadn't paid
>much attention to it until this morning. On my Yaesu
>FT-857 ( an Icom 706 MKIIG clone ) On the Yaesu it
>sounded like there was a thunderstorm in the not to
>distant area with static noise levels around S5 or S6.
>I fired up the Omni D (Series C)on the same antenna
>and it was as quiet as a church mouse, the S meter
>would drop to almost it's resting state and the noisy
>Midcars net I was listening to sounded almost like a 2
>meter FM station at full quieting. I know the Omni
>isn't insensitive as I've had it back to Ten Tec for
>an alignment within the past couple of months.
>
>I've got some 120 KV lines and a substation about 500
>feet behind my house and wonder if for some reason the
>Yaesu is sensitive to that noise and the Omni isn't ?
>
>I just wonder if someone has a good logical
>explanation, I'm in Flint, Mich and worked a mobile
>running 5 watts in Mass. on a poor condition 40 meter
>CW band and I doubt with the noisy receiver of the
>'857 I would have heard him at all.
>
>I just wonder if anyone has any technical explanations
>for this ? Needless to say I'm not going to part with
>the old Omni D anytime in the near future.
>
>Thanks in advance
>
>Gary K8IQ
>
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