[TenTec] OMNI V J310's
Dr. Gerald N. Johnson, P.E.
geraldj@ames.net
Sun, 24 Jan 1999 13:30:01 -0600
Bill Cook wrote:
>
> patents@dx0man.prestel.co.uk wrote:
>
> > Thanks Steve & Jerry ! Two points:-
> >
> > (i) if the J-310s feel warm (= hot ?) after some period of
> > use, then perhaps its time to fit clip-on heat sinks ??
> > The one(s) with lowest internal R will presumably run hotter and their
> > parameters will tend to drift faster than the cooler ones. Not very
> > fast perhaps, but with prolonged use then who knows ?? This could be
> > the kind of fault that gradually sneaks up on you.
> >
> > I think I now have a clue as to why my OMNI-V RF gain seems to drop
> > slowly over several hours, if I leave it running. The effect is that
> > on 10/12/15/17 and even 20 when the band is near dead. I need to
> > steadily increase the RF gain setting, to over-ride the IF/audio
> > noise. Note that I'm talking hours here and its much less noticable if
> > the bands are lively.
> >
> > (ii) those switching diodes .... I checked my notes and I see that I
> > researched their replacement to avoid ordering them from TT and
> > getting hit by airmail and even Customs charges. But in the end I
> > found them listed by a small UK parts house who regularly attend
> > hamfests. They were happy to get me a bag full of the original BA
> > 482s and you are right; they are vhf switching diodes and its unclear
> > if the architecture is PIN. Now to ask them if they will do a similar
> > low cost deal for a bag of J-310s.
> >
> > 73 - John G3JAG
> >
> > On 23-Jan-99 Steve Baron wrote:
> > > Understand.
> > >
> > > This radio was used when I got it Happened to check the 310
> > > voltages one
> > > day and found that most were around 1.5 (1.7 ?) volts. Some were
> > > as low as
> > > 0.5 volts.
> > >
> > > Replaced some (from TT) and all came up to the higher value. That
> > > was a few
> > > (5 ?) years ago. My impression at the time was that it cleaned up
> > > 40 and
> > > 80; note that very quantitative statement.
> > >
> > > Just spot checked them a few weeks ago while doing something else,
> > > and saw
> > > that a few (2 ?) had dropped to about 0.9...so I asked the
> > > question. Sort
> > > of a purely academic question.
> > >
> > > My impression is they work (have to) fairly hard (feel them) and
> > > maybe they
> > > really do change - at least some of them.
> > >
> > > Not paranoid about it...just curious.
> > >
> > > My recollection is that TT recommends not replacing their diodes.
> > > Looked
> > > into it once and found out that the diodes they use are kind of
> > > funny --- if
> > > I remember correctly, they are described as pin diodes but really
> > > may not be
> > > exactly ...think their recommended use was rf switching at VHF freq
> > > ?
> > >
> > > We have had several excellent quantitative articles by several
> > > authors who
> > > have highlighted the improvement which can be obtained by changing
> > > some of
> > > the diodes in some rigs - rigs that we know have problems and ones
> > > which we
> > > did not buy - perhaps exactly because of those problems.
> > >
> > > I would not switch my diodes without some proof - quantitative - of
> > > improvement.
> > >
> > > My impression is that one must be careful with diode selection
> > > since
> > > impedance in the on state, current requirements, etc are all
> > > important.
> > > All pin diodes are not created equal and unless you select the
> > > right one and
> > > 'install' it properly you may be wasting your time...gee, wonder if
> > > you
> > > could get a 'quieter' rig because your diodes weren't switched
> > > fully on!
> > >
> > > Hope that helps
> > > -----Original Message-----
> > > From: patents@dx0man.prestel.co.uk <patents@dx0man.prestel.co.uk>
> > > To: Steve Baron <stevebaron@starlinx.com>
> > > Cc: TenTec <TenTec@contesting.com>
> > > Date: Saturday, January 23, 1999 2:25 AM
> > > Subject: RE: [TenTec] OMNI V J310's
> > >
> > >
> > >>
> > >>I'm intrigued by your query about the OMNI-V J310's. I have an
> > >>OMNI-V
> > >>and its now quite ancient. Are there any symptoms associated with
> > >>J310 ageing ?? I feel, but cannot verify, that I've recently been
> > >>getting more intermod than I used to get when the rig was newer,
> > >>especially on 40m. Could be that the European QRM is a lot louder
> > >>now
> > >>I use ladder line instead of 100ft of coax, but it has occurred to
> > >>me that I might also have a front end problem developing. The
> > >>front
> > >>end sensitivity on the HF (20 and up) bands appears to be low,
> > >>although I can hear signals way down to the antenna noise if I
> > >>crank
> > >>up the RF gain. I cannot crank up the audio gain without getting
> > >>noise of the wrong sort - not from the antenna. (My RF gain is
> > >>usually
> > >>well up, at 3-4 PM; audio stays down at 9-10 PM).
> > >>
> > >>The J310 is easily obtainable here, but I'm not sure how to set
> > >>about
> > >>matching a set of four. I think any replacement must use a well
> > >>matched set, or it will defeat the object of sharing the work load.
> > >>
> > >>Incidentally, I replaced all the front end switching diodes with
> > >>locally obtained pin diodes (not necessarily the best ones for the
> > >>job - see recent comment on Paragon diode swap). This was before I
> > >>discovered the obvious - I had a stuck reed relay !! There was no
> > >>noticable performance improvement, even when I fixed the relay
> > >>(with the help of the TT service dept).
> > >>
> > >>But I wonder if I should really be considering a complete
> > >>re-alignment
> > >>(is there any info on that available ?) after so much heavy use.
> > >>
> > >>73 John G3JAG
> > >>
> > >>
> > >>On 20-Jan-99 Steve Baron wrote:
> > >>>
> > >>> A few years ago I noticed that the voltage on a few of the J10's
> > >>> was
> > >>> significantly lower (0.5 to 1 V) than the others which were up
> > >>> around 1.5
> > >>> (1.7 ?) or so. Replaced some and all were 'balanced'.
> > >>>
> > >>> Recently had the covers off and checked them again and saw that a
> > >>> few had
> > >>> dropped again.
> > >>>
> > >>> Would appreciate any input on the effect of reduced voltage - and
> > >>> perhaps a
> > >>> number for the lowest that should be tolerated.
> > >>>
> > >>> Thanks.
> > >>>
> > >>>
> > >>>
> > >>> --
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> > >>
> > >>----------------------------------
> > >>E-Mail: patents@dx0man.prestel.co.uk
> > >>Date: 22-Jan-99
> > >>Time: 14:03:35
> > >>John Crux
> > >>Consultant in product forgery - Asia and
> > >>Africa
> > >>
> > >>----------------------------------
> > >>
> > >>--
> > >>FAQ on WWW: http://www.contesting.com/tentecfaq.htm
> > >>Submissions: tentec@contesting.com
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> > >>
> >
> > ----------------------------------
> > E-Mail: patents@dx0man.prestel.co.uk
> > Date: 23-Jan-99
> > Time: 08:41:30
> > John Crux
> > Consultant in product forgery - Asia and
> > Africa
> >
> > ----------------------------------
> >
> > --
> > FAQ on WWW: http://www.contesting.com/tentecfaq.htm
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>
> Ideally you want to set the J310 to between 10 and 15 milliamps
> quiesent, total current drain. Yes they do run a little hot/warm to the
> touch. Look up the specs you'll be surprised how hot they can run.
>
> Bill Cook N4WC
>
> --
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I think the devices are only matched when they have nearly the same
currents with the same value source resistors.
73, Jerry, K0CQ
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