[TenTec] Re: OMNI 6+

Bob & Linda McGraw K4TAX RMcGraw@InfoAve.Net
Tue, 10 Jul 2001 09:17:32 -0700

cc: Tentec list

Sounds like you have all the latest mods to improve the Omni VI+.  Those
have been done to mine as well and I'm pleased with the results.

As to the RF issues.  I haven't had any problems with RF getting into
the Omni VI+ when used as a "bare bones" radio.  The mike is a 705 desk
mike.  However, when I start connecting cables to the rear panel, i.e.
audio in/out for PSK, PTT, relay, and 12V and etc then some problems do
appear.  In most cases I added a 0.1 mfd disk ceramic to the RCA
connector inside the radio to near-by chassis/ground.  The audio in/out
I added a .005mfd.  I use the radio mostly as the IF on 10 M for the VHF
transverters (2M) and UHF transverters (70 cm).  I run lots!!! of power
on these band as I do EME and MS work.  The VHF and UHF antennas are fed
with 1/2" Andrew hardline.

On HF the Centurion sits beside the Omni and also a 238 tuner.  HF
antennas are (1) coax fed 1/2 wave with RG-213, with a 1:1 balun at the
top for 75M and (2) a center fed 1/2 wave on 160M with balanced feed
brought all the way to the tuner.  I'm in a wood frame house, on the 2nd
floor, middle of the house.  The feed lines go up behind the operating
station, through the ceiling into the attic, out the eve, up the tower. 
RF ground is non existant at the station operating position due to the
distance between the operating position and "mother earth".  I do use
3rd pin AC ground for safety reasons. This is true also for the amps
which all have 3 wire 230 volt service back to the main house breaker
panel.  That run is about 60 ft.  Tower grounding.....that's another
topic for discussion however.  We are 550 ft above average terrain. 
Lightening everywhere here on the mountaintop!

The computer and monitor are some 3 or 4 feet from the radio position (I
can and do use both at the same time) and are on the same outlet as the
radios.  No problems with computer noise or RF into the computer.  The
TV antenna is on the side of the tower which has all the HF, VHF/UHF
antennas.  We are 85 miles from the nearest VHF TV station and there is
no TVI nor does the TV interfer with the HF or VHF/UHF operation.  TV
antennas are coax fed 75 ohm.  All coax lines are closely tied to the
legs of the Rohn 25G.  The balanced feed line for the 160M antenna is on
several home made PVC stand-off arms that keep the line 18" from the

If any one has questions, don't hesitate to send me an e-mail.  I'll try
to help.


pywacker@fuse.net wrote:
> Bob, thanks for the info. Wish I knew exactly what Paul instructed you to
> do. I am plagued with RF here from time to time also on the TenTec stuff. I
> recently purchased a beautiful 1998 Omni VI+ and hand carried it to Ten Tec
> two weeks ago requesting updates.
> (1) Changed the oven to TCXO.........Night and day
> difference....WOW!!((Initial turn on voices sound on frequency immediately)
> again WOW!
> (2) Updated logic chip from 1.02 to 1.03.............changes PLL timing to
> eliminate CW chirp per TT
> (3) S.T. click mod to IF/AF added  ....
> (4) Keyer speed mod to logic board added
> (5) Reduced some birdies  2-3 db by adding grounds and rerouting cables
> (6) BFO alignment, checked carrier null, RX alignment plus check RX and TX
> functions
> I have since added the 2.8 INRADS.
> Going back to the cores and caps I noticed a number of ferrite beads were
> already on the mic wires where they attach to the front panel mic jack
> I still had to add a snap on core around the 705 mic cable to keep RF out. I
> also have a recently acquired used Jupiter and a Pegasus that I had bought
> new which is now for sale and any cabling attached to them has snap on
> cores. Also inside the rigs I have added additional snap on cores. I also
> typically just run 500-1000 at the most when using these radios. The two
> Japanese rigs I do not worry about RF and easily run 1500 with no signs of
> RF.
> 73 de KE4WY Jim
> ----- Original Message -----
> From: "Bob & Linda McGraw K4TAX" <RMcGraw@InfoAve.Net>
> To: <VE1BN@aol.com>
> Cc: <tentec@contesting.com>
> Sent: Tuesday, July 10, 2001 1:25 AM
> Subject: [TenTec] Re: OMNI 6+
> >
> > Don & TENTEC List:
> >
> > Well I started this so I best finish it.  I've had several direct
> > inquiries about this.
> >
> > I suffered with RF getting into the audio of my Paragon I.  Admittingly
> > the operating position was some 15 ft from the vertical antenna. Since
> > the vertical was mounted on the our boat dock in a tidal salt water
> > canal, ground was not an issue or concern and moving the antenna was not
> > an option. (Florida property restrictions)  The vertical was fed with a
> > buried length of RG-213 from the antenna feed point and then up through
> > the floor in the shack.  Moving the radio was not an option either.
> > (Wife restrictions)
> >
> > In the process of finding the problem, I changed mikes, mike cables and
> > a few other things without satisfactory results.  Using the Centurion
> > amp was out of the question too.  I called Paul Clinton at Tentec,
> > discussed it throughly and was provided, at no charge, some ferrite
> > beads and some ceramic C's.  I don't recall the actual values.  I was
> > instructed to place them on the 4 leads inside the radio at the MIC
> > connector.  Did so.  Problem solved.  I think the RF was getting into
> > the radio via either the + voltage for the mic or the PTT line.
> > Couldn't prove this one way or another.  Now I could run the Paragon and
> > Centurion on any band 75 M - 10 M without any problems.  Same antenna,
> > same feed, same location. Just lots more power.
> >
> > Oh yes, the dock pile mounted vertical in a salt water tidal canal is a
> > killer of an antenna.  However SWR does change slightly with the tides.
> > (So the ground moves a bit up and down.)
> >
> > Traded the Paragon for a Omni VI+ in 1997.  Recently I had the need to
> > open the Omni and noticed that the beads were on the wires from the mic
> > connector.  Don't recall about the C's.  One other recent e-mail
> > correspondent indicated that his Omni of 1994 vintage did not have them.
> >
> > Just thought you'd like to know.  If there are questions, please direct
> > them to me.
> >
> > 73
> > Bob K4TAX
> >
> >
> > VE1BN@aol.com wrote:
> > >
> > > Hello Bob -
> > >
> > > I am also one of the curious OMNI 6+ owners who would appreciate it if
> > > you
> > > would tell me what TT sent you to clean up any RF problems in your
> > > rig.  I
> > > also have a Paragon and seems like there is a cure here too.
> > >
> > > I am not suffering from RF like we are hearing from some of the
> > > Jupiter
> > > owners,  but will you let me know about the above?  What and how much?
> > >
> > > Regards,
> > >
> > > Don    VE1BN@aol.com
> >
> >
> > --
> > FAQ on WWW:               http://www.contesting.com/FAQ/tentec
> > Submissions:              tentec@contesting.com
> > Administrative requests:  tentec-REQUEST@contesting.com
> > Problems:                 owner-tentec@contesting.com
> >
> >

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