[TenTec] Fw: Cooling fans and IF gain

[Mike Coogan W7MGC]

I noticed the same heat build up on the 962 p.s. for my Omni 6+ when 
running Rtty. I mounted a TT 310 fan on the heat sink of the power 
supply, powered from the 12v dc outlet on the p.s.

 Mike  W7MGC
Vancouver, Washington

Omni 6+ >>253 Auto Tuner>>HercII amp, Love it!


----- Original Message ----- 
From: "Robert & Linda McGraw K4TAX" <RMcGraw at Blomand.Net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Friday, July 15, 2005 6:08 AM
Subject: Re: [TenTec] Cooling fans and IF gain


> Interestingly enough, the Omni VI+ PA is rated at 100% duty cycle 
> while the
> 961 power supply is not.  I've found that additional cooling on the 
> power
> supply is necessary in high duty cycle modes, partly caused by the 
> bridge
> rectifier being mounted to the bottom plate for heat dissipation.  A 
> small
> 12V fan blowing on the heat sink in the rear takes care of the 
> problem.
> Also, one might take note that if the power supply is sitting flat on 
> the
> desk there is little room at the bottom rear for vertical air 
> convection.
> If possible, elevate the power supply, allow the heat sink to hang off 
> of
> the rear support and allow the heat sink to have more "breathing 
> room".
>
> As to the Omni VI+, I've found that heat build up within the radio 
> does
> cause some frequency drift primarily due to BFO frequency changes.  I
> changed my BFO's to TXCO's and found a nice improvement.  All in all,
> probably not worth the investment, time and effort, for such a small
> benefit.
>
> I've read cases where one removed the speaker, replaced it with a 
> computer
> type 12 V fan that made improvements of about the same magnitude to 
> the
> radio. This would be a lot less work and a lot less $$.
>
> 73
> Bob, K4TAX
>
>
> ----- Original Message ----- 
> From: "Chuck Guenther" <ni0c at earthlink.net>
> To: <tentec at contesting.com>
> Sent: Thursday, July 14, 2005 8:17 PM
> Subject: [TenTec] Cooling fans and IF gain
>
>
>> N6KB wrote: "I find that operating my Omni VI in CW contests a fan on 
>> the
>> PA heat
>> sink is necessary. My Kenwood TS-440 has a built-in fan with 
>> temperature
>> controlled speed, or at least duty cycle. The TS-440 receiver
>> performance in contest conditions does not compare to the Omni VI
>> though. I wish Ten-Tec would have included a built in fan. I have 
>> never
>> tried, or thought that I needed, a fan to ventilate the insides of 
>> the
>> Omni VI though."
>>
>> I used a TS-440S for about seven years (in fact I still have it). 
>> The
>> only time the cooling fan ever came on was during an RTTY contest (I 
>> was
>> running about 60 watts).  It never came on when operating CW or SSB.
>>
>> With the Ten Tec rig, I find the heat sink of my 961 PS always runs 
>> at a
>> higher temperature than the Omni 6 PA heat sink.
>>
>> Today, in order to alleviate my gain problem, I swapped out the Ten 
>> Tec
>> 221 filter for the INRAD 753 (which has a few dB less insertion 
>> loss).
>> The gain seems adequate (and more stable) now, so perhaps my problem 
>> was
>> in the filter, or the connections thereto.
>>
>> 73,
>> Chuck  NI0C
>> .
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>
>
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