Diffcult to answer for your question...
We are talking here about two different things.
The fix no. 1 helped most, if you consider the amount of
work I put into the project. The noise is practicaly gone...
But if you never work on higher bands
you never will be disturbed by that noise...
In case of fix no. 2 the most paid off, gives reduction of the RF gain knob
from max to 16:00 o'clock. Some people say they have to
reduce it to 15:30 to get rid of that noise. The soldering job give
very little pay off.
Best regards
Piotr LA9HFA
At 08:17 AM 2/7/00 -0600, you wrote:
>Piotr;
>
>Thanks for the feedback and information. I posted the original OMNI
>NOISE msg.
>
>Do you think any 1 or 2 specific changes made a big difference. You've
>gone to a lot of work. What changes produced the most result in noise
>reduction?
>
>Thanks in advance.
>
>73
>Bob K4TAX
>
>Piotr Tomczak wrote:
>>
>> Hello to All noise interested people...
>>
>> There has been some discusions about the noise and I discoverd that
>> I do heard two different types of noise on my OMNI VI+ 9 months
>> old model.
>>
>> 1. The syntesier noise, mostly heard on a quiet night, specialy when you
>> tune around but it can also be heard on some frequencies as a currier.
>>
>> 2. The Front/End noise of the RF/IF stage when the RF gain is on max.
>> Some body asked who runs with RF on MAX ??? I did on Drake
>> but I do not on TenTec.
>>
>> Answers to problems...
>> 1.... I add additional screening to the controller board. Put physical
>> cover on the
>> top of the board compartment.
>> I add ferrite bead on the DC +12V power lines into the control board.
>> I put most of the cables going out of the control board compartment though
>> the ferrite clips.
>> I add dcoupling capacitors of 10nF-20nf to most IC +/- legs
>> located on the controller board
>>
>> It helped !!! The noise is so much reduced that I can bearly hear it at
all.
>> Lots of effort but it is worht it.
>>
>> 2.... There are some of the boards in TT which are double sided but the
>> laminate
>> do not have through plated holes. (pitty for a rig so expansive and
produced
>> at the end of 20th century but it is a fact...)
>>
>> What I did I soldered caps and resistors to the grounding layer on
>> both sides of the laminate. Be careful not all components tolerate
>> overheating !!! Do it with causions. It is better to leave one cap
>> unsoldered on both sides then demage it.
>>
>> Some boards are modified it that way directly from the factory!!!
>>
>> It helped but not as much as I thought it will do.
>> So I run the rig with the rf gain at 16:00 and it is perfec.
>> The gain is still there and the noise is gone. I have more plans to
>> fix it permamently but right now I do not have neither idea or time
>> to do it.
>>
>> For removing confusions . If you increas the RF gain from
>> 16 to 17 o'clock the signal is not increased only the noise.
>>
>> Best regards It was my 1 krone to the discusion.
>>
>> Maybe some fanatics did not liked it but maybe some
>> will try to improve the good rig any way to be better.
>>
>> Good Luck
>> Piotr LA9HFA
>>
>> --------------
>> \\\@///
>> · ·
>> o
>> -------------
>> Piotr Tomczak Ham call: la9hfa
>> Nera ASA E-mail: pito@satcom.nera.no
>>
>> --
>> 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
>
>
>
>
>
--------------
\\\@///
· ·
o
-------------
Piotr Tomczak Ham call: la9hfa
Nera ASA E-mail: pito@satcom.nera.no
--
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
|