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Re: [TenTec] Intermitten Omni VI RX Falloff

To: atrampler@att.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Intermitten Omni VI RX Falloff
From: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Reply-to: geraldj@weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sat, 28 Aug 2010 14:09:39 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>

On 8/21/2010 9:35 AM, Art Trampler wrote:
> Jerry,
>
> I'm not familiar with switch on back of rig for AUX RX...only on front of
> rig next to AGC.

That's where it is on the Omni VI I see when I checked the manual. On my 
Corsair II its on the back panel and handles RF. Tends to go open 
disconnecting the receiver from the transmit antenna. So its diode 
switched in the Omni VI.
>
> Am I missing something?
>
> Funny how many (different) answers one question got!

There are thousands of parts and connections between the antenna and the 
speaker, and any one or a group of them can have been badly soldered or 
leads welded to chips inside diode, transistor, or IC packages. And for 
all those that answered, some have experienced one or more of those 
failures. Could be signal cables, or card edge connectors. You can 
isolate by signal tracing or signal injecting to find where the signal 
is lost. Or you can shotgun cleaning every cable and board edge 
connector with a drop of DeoxIT and some exercise. That includes the 
insulation displacement cable connections. Maybe you can induce the 
failure and recovery by applying heat (hair dryer, hot air gun) and cold 
(Freeze Mist was made for that job) alternatively, at first generally, 
then do a binary chop (each time do half the area previously temperature 
cycled) until you get it down to the part. Sometimes another shotgun 
technique is to resolder a suspect board and some in other Tentecs have 
been known to need that, but that's only really successful if your 
soldering is better than the factory's.

Sometimes its shock or vibration that brings on the fault, but most 
often its heat if it recovers after the radio has been off a while. You 
can speed those up with hot air and Freeze Mist.
>
> Art
>
> -----Original Message-----
> From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
> On Behalf Of Dr. Gerald N. Johnson
> Sent: Thursday, August 19, 2010 10:21 PM
> To: tentec@contesting.com
> Subject: Re: [TenTec] Intermitten Omni VI RX Falloff
>
> Aux RX switch on the back of the radio. Needs cleaning.
>
> 73, Jerry, K0CQ
>
> On 8/19/2010 10:15 PM, Art Trampler wrote:
>> Hey All,
>>
>>
>>
>> On my Omni VI Opt 3, the RX periodically drops off 20 to 25db, using a
>> 6db/S-unit scale.  If I wiggle the RF gain it can pop back, or if I go key
>> down for one “dih.”  I haven’t tried simply closing the PTT to restore (as
>> opposed to any transmission) but I think that would also do it.
>>
Wiggling the RF gain makes me suspicious of that control or the board 
its attached to. Likely there's a great voltage change on that part when 
going to transmit and returning to receive to break down the errant poor 
connection. Could be IN the pot, or its connections, or somewhere on the 
board its mounted on.
>>
>>
>> I’d think “Relay” or “Diodes” if it only popped back with closing the
>> PTT/sending; I’d think bad solder joint if it was only the RF gain.
> What’s
>> interesting is that the RX is not lost, just significantly
>> reduced/attenuated.
>>
>>
>>
>> Your thoughts?
>>
>>
>>
>> Thanks,
>> Art
>>
>>
>>
>> Art Trampler, KØRO
>>
>>
>>
>>
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