TenTec
[Top] [All Lists]

[TenTec] Calling all Omni Six Owners

To: <tentec@contesting.com>
Subject: [TenTec] Calling all Omni Six Owners
From: paulc@mediaone.net (Paul Christensen)
Date: Wed, 7 Oct 1998 09:15:48 -0400
This is a multi-part message in MIME format.

------=_NextPart_000_0078_01BDF1D3.12A468C0
Content-Type: text/plain;
        charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Those of you who have an Omni Six/Six Plus that exhibit a slight =
transmitted CW chirp may be in for some good news.  George, W2VJN at =
INRAD has agreed to manufacture a 2.8 kHz BW 9 MHz I.F. filter if we can =
demonstrate enough of a demand for it.  This is a replacement filter for =
the stock 2.4 kHz BW 9 MHz filter.  This is the only filter in the Omni =
that shares the receive and transmit function.  This same filter also =
exacerbates the slight chirp caused by frequency-shift-keying the Omni's =
9 MHz BFO circuit board on some Omnis. =20

How can you tell if your Omni is transmitting with chirp?  Yes, of =
course you listen for it.  But in many cases is can be subtle.  It's =
when you compare the CW note against another Ten-Tec when you notice the =
difference the most.  Here's a test you can use: key your transmitter in =
the CW mode, sending a string of characters, listening carefully to the =
CW note on another receiver.  It's best to use a wide SSB bandwidth for =
monitoring. Next, depress the Omni's FSK mode button.  Again. key the =
transmitter by sending a string of characters, listening for any change. =
 In FSK, the CW transmit circuit is identical, with the only exception =
being that the sidetone monitor is disabled, but more importantly....the =
transmit BFO frequency is HIGHER than it is in CW, placing the CW well =
above the lower skirt of the 2.4 kHz filter.  If CW sounds cleaner to =
you in FSK than it does in CW, you've got the problem I'm discussing =
here. =20

I want to make this point clear: the problem does NOT manifest on all =
Omnis.  Nevertheless, on those that are not problematic of a chirp, the =
CW BFO transmit offset frequency of 9,000.400 is running dangerously =
close to the 2.4 kHz filter's lower passband skirt.  When the CW =
transmit BFO frequency reaches the filter skirt, chirp results and the =
transmitted CW waveform can become truncated on the trailing edge.=20

Recall that the Omni's CW transmitted BFO frequency is 9,000.400 kHz.  =
The center frequency for this filter is mid-way between the LSB and USB =
transmitted BFO frequencies at 9,001.500 kHz.  Therefore, the margin of =
lower skirt freedom in the designed Omni Six/Six Plus is only 100 Hz; =
the filter cuts off at 9,000.300 kHz.  If the filter is not near =
perfection in manufacturing, the CW BFO frequency can indeed fall square =
on the filter's edge as it does in two of my Omni Sixes. =20

Other's have repeatedly asked me why the Omni V sounds so consistently =
good on CW transmit in comparison with some Omni Sixes.  With the Omni =
V's CW circuitry being a close 99% match to that of the Omni Six, the =
answer again lies with this filter.  Only in the Omni V, the fixed CW =
offset is 9,000.600 kHz, well out of harms way of the lower filter =
skirt.  Here, the Omni V has a margin of freedom of 300 Hz, not 100 Hz =
as in the Omni Six series.

A 2.8 kHz BW, 9 MHz I.F. filter will provide for the same 300 Hz of =
safety to the lower filter skirt.  While this corrects the problem on =
CW, how will it affect SSB operation?  If the USB and LSB BFO =
frequencies remain the same, the audio response goes from 300Hz - 2.7 =
kHz to 100 Hz- 2.9 kHz.  As a practical matter, this should not present =
a problem.  Yes, the occupied bandwidth is slightly greater, but not so =
much as to cause QRM to QSOs near your operating frequency.  As a side =
note, Kenwood once sold a filter with this bandwidth and the Yaesu =
FT-1000MP has a menu choice for expanded transit SSB audio response.  =
Also, since the USB and LSB frequencies are adjustable, the audio =
passband characteristics could be shifted slightly if desired.

A minimum of five brave souls are needed for George to make this filter. =
 Cost of the filter to us is $110.  Shipping is 2 months ARO.

If you have an interest in this, please e-mail me directly and I will =
forward your commitment to George.  Thanks.

-Paul, W9AC
Jacksonville, Florida=20

-----Original Message-----
From: George Cutsogeorge <w2vjn@rosenet.net>
To: Paul Christensen <paulc@mediaone.net>
To: <tentec@contesting.com>
Date: Tuesday, October 06, 1998 5:01 PM
Subject: Re: Omni Six Filter


Hi Paul,
=20
Glad you were able to isolate the problem.  We can have a 2.8 centered =
on 9001.5 made with similar specs to our 2.1.  If you can get 4 or 5 =
orders together, we will order 10 pcs.  Our minimum order is 10, so we =
like to know some of them will sell.  Delivery is about 2 months ARO.
=20
George

------=_NextPart_000_0078_01BDF1D3.12A468C0
Content-Type: text/html;
        charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

<!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN">
<HTML>
<HEAD>

<META content=3Dtext/html;charset=3Diso-8859-1 =
http-equiv=3DContent-Type><!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 =
HTML//EN"><!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"><!DOCTYPE HTML =
PUBLIC "-//W3C//DTD W3 HTML//EN">
<META content=3D'"MSHTML 4.72.2106.6"' name=3DGENERATOR>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT color=3D#000000 size=3D2>Those of you who have an Omni =
Six/Six Plus that=20
exhibit a slight transmitted CW chirp may be in for some good =
news.&nbsp;=20
George, W2VJN at INRAD has agreed to manufacture a 2.8 kHz BW 9 MHz I.F. =
filter=20
if we can demonstrate enough of a demand for it.&nbsp; This is a =
replacement=20
filter for the stock 2.4 kHz BW 9 MHz filter.&nbsp; This is the only =
filter in=20
the Omni that shares the receive and transmit function.&nbsp; This same =
filter=20
also exacerbates the slight chirp caused by frequency-shift-keying the =
Omni's 9=20
MHz BFO circuit board on some Omnis.&nbsp; </FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>How can you tell if your Omni is transmitting with=20
chirp?&nbsp; Yes, of course you listen for it.&nbsp; But in many cases =
is can be=20
subtle.&nbsp; It's when you compare the CW note against another Ten-Tec =
when you=20
notice the difference the most.&nbsp; Here's a test you can use: key =
your=20
transmitter in the CW mode, sending a string of characters, listening =
carefully=20
to the CW note on another receiver.&nbsp; It's best to use a wide SSB =
bandwidth=20
for monitoring. Next, depress the Omni's FSK mode button.&nbsp; Again. =
key the=20
transmitter by sending a string of characters, listening for any =
change.&nbsp;=20
In FSK, the CW transmit circuit is identical, with the only exception =
being that=20
the sidetone monitor is disabled, but more importantly....the transmit =
BFO=20
frequency is HIGHER than it is in CW, placing the CW well above the =
lower skirt=20
of the 2.4 kHz filter.&nbsp; If CW sounds cleaner to you in FSK than it =
does in=20
CW, you've got the problem I'm discussing here.&nbsp; </FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT color=3D#000000 size=3D2>I want to make this point clear: the =
problem=20
does NOT manifest on all Omnis.&nbsp; Nevertheless, on those that are =
not=20
problematic of a chirp, the CW BFO transmit offset frequency of =
9,000.400 is=20
running dangerously close to the 2.4 kHz filter's lower passband =
skirt.&nbsp;=20
When the CW transmit BFO frequency reaches the filter skirt, chirp =
results and=20
the transmitted CW waveform can become truncated on the trailing edge.=20
</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>Recall that the Omni's CW transmitted BFO frequency =
is=20
9,000.400 kHz.&nbsp; The center frequency for this filter is mid-way =
between the=20
LSB and USB transmitted BFO frequencies at 9,001.500 kHz.&nbsp; =
Therefore, the=20
margin of lower skirt freedom in the designed Omni Six/Six Plus is only =
100 Hz;=20
the filter cuts off at 9,000.300 kHz.&nbsp; If the filter is not near =
perfection=20
in manufacturing, the CW BFO frequency can indeed fall square on the =
filter's=20
edge as it does in two of my Omni Sixes.&nbsp; </FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>Other's have repeatedly asked me why the Omni V =
sounds so=20
consistently good on CW transmit in comparison with some Omni =
Sixes.&nbsp; With=20
the Omni V's CW circuitry being a close 99% match to that of the Omni =
Six, the=20
answer again lies with this filter.&nbsp; Only in the Omni V, the fixed =
CW=20
offset is 9,000.600 kHz, well out of harms way of the lower filter =
skirt.&nbsp;=20
Here, the Omni V has a margin of freedom of 300 Hz, not 100 Hz as in the =
Omni=20
Six series.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>A 2.8 kHz BW, 9 MHz I.F. filter will provide for the =
same 300=20
Hz of safety to the lower filter skirt.&nbsp; While this corrects the =
problem on=20
CW, how will it affect SSB operation?&nbsp; If the USB and LSB BFO =
frequencies=20
remain the same, the audio response goes from 300Hz - 2.7 kHz to 100 Hz- =
2.9=20
kHz.&nbsp; As a practical matter, this should not present a =
problem.&nbsp; Yes,=20
the occupied bandwidth is slightly greater, but not so much as to cause =
QRM to=20
QSOs near your operating frequency.&nbsp; As a side note, Kenwood once =
sold a=20
filter with this bandwidth and the Yaesu FT-1000MP has a menu choice for =

expanded transit SSB audio response.&nbsp; Also, since the USB and LSB=20
frequencies are adjustable, the audio passband characteristics could be =
shifted=20
slightly if desired.</FONT></DIV>
<DIV><FONT size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2>A minimum of five brave souls are needed for George =
to make=20
this filter.&nbsp; Cost of the filter to us is $110.&nbsp; Shipping is 2 =
months=20
ARO.</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT color=3D#000000 size=3D2>If you have an interest in this, =
please e-mail=20
me directly and I will forward your commitment to George.&nbsp;=20
Thanks.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT color=3D#000000 size=3D2>-Paul, W9AC</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2>Jacksonville, =
Florida&nbsp;</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2><B>-----Original =
Message-----</B><BR><B>From:=20
</B>George Cutsogeorge &lt;<A=20
href=3D"mailto:w2vjn@rosenet.net";>w2vjn@rosenet.net</A>&gt;<BR><B>To: =
</B>Paul=20
Christensen &lt;<A=20
To: <tentec@contesting.com>
href=3D"mailto:paulc@mediaone.net";>paulc@mediaone.net</A>&gt;<BR><B>Date:=
=20
</B>Tuesday, October 06, 1998 5:01 PM<BR><B>Subject: </B>Re: Omni Six=20
Filter<BR><BR></DIV></FONT>
<DIV><FONT size=3D3>Hi Paul,</FONT></DIV>
<DIV><FONT size=3D3></FONT>&nbsp;</DIV>
<DIV><FONT face=3D"" size=3D3>Glad you were able to isolate the =
problem.&nbsp; We=20
can have a 2.8 centered on 9001.5 made with similar specs to our =
2.1.&nbsp; If=20
you can get 4 or 5 orders together, we will order 10 pcs.&nbsp; Our =
minimum=20
order is 10, so we like to know some of them will sell.&nbsp; Delivery =
is about=20
2 months ARO.</FONT></DIV>
<DIV><FONT face=3D"" size=3D3></FONT>&nbsp;</DIV>
<DIV><FONT face=3D"" size=3D3>George</FONT></DIV></BODY></HTML>

------=_NextPart_000_0078_01BDF1D3.12A468C0--


--
FAQ on WWW:               http://www.contesting.com/tentecfaq.htm
Submissions:              tentec@contesting.com
Administrative requests:  tentec-REQUEST@contesting.com
Problems:                 owner-tentec@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm


<Prev in Thread] Current Thread [Next in Thread>
  • [TenTec] Calling all Omni Six Owners, Paul Christensen <=