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>
To: <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.
>>>
>>>
>>>
>>> --
>>> 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
>>
>>----------------------------------
>>E-Mail: patents@dx0man.prestel.co.uk
To: <tentec@contesting.com>
>>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
>>Administrative requests: tentec-REQUEST@contesting.com
>>Problems: owner-tentec@contesting.com
>>Search: http://www.contesting.com/km9p/search.htm
>>
----------------------------------
E-Mail: patents@dx0man.prestel.co.uk
To: <tentec@contesting.com>
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
Submissions: tentec@contesting.com
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Problems: owner-tentec@contesting.com
Search: http://www.contesting.com/km9p/search.htm
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