[TenTec] Omni VI audio problem
Greg S
oldlongbeard at yahoo.com
Tue Sep 18 22:25:18 EDT 2018
Run both audio sources in the back. Switch between them with a conveniently mounted DPDT switch. These rigs ain’t worth much any more. I little hole, or a bracket added somewhere isn’t gonna kill what little value they have left. I like mine, but have a few tinkerers mods slated for the upcoming winter months.
Kind regards,
Greg, KC8HXO
Sent from my Linux device
> On Sep 18, 2018, at 09:29, Bob McGraw K4TAX <rmcgraw at blomand.net> wrote:
>
> Even with that approach, any noise coming out of the computer sound card output stage will be sent to the input of the Omni VI. This will occur even when the audio gain of the computer is reduced or muted as the gain control is before the output stage of the sound card. Just the fact, any noise coming out of the computer will be introduced into the MIC audio due to the design of the circuit.
>
> One can add some 20 dB of attenuation in the form of an L Pad between the output of the computer and the input to the radio. This will reduce the amount of noise to perhaps a satisfactory level. But still, there will be some noise coming from the computer sound care, reduced 20 dB. And one will then need to raise the gain of the data signal in the computer application to off-set this 20 dB attenuation. While I find this works and I operated this way for years, the digital artifacts from the computer may still exist to some lesser extent, although may be found to be satisfactory.
>
> The best solution is to disconnect the cable to the rear input when not used. But when used, you will still likely need the 20 dB attenuation to clean up the digital noise out of the computer. A Transformer is an OK idea as long as it is configured to have voltage loss and not matched loss. The idea of the transformer is to eliminate a "ground loop" what ever that might be. {The only ground loop I'm familiar with is upon less than a careful landing of a Piper Tripacer in a cross wind.}
>
> 73
>
> Bob, K4TAX
>
>
>> On 9/18/2018 4:50 AM, Barry N1EU wrote:
>> Stan, to get rid of the residual hash do one of the following:
>>
>> 1. assure you have the computer chassis and Omni 6 chassis properly bonded
>> to common station ground.
>> 2. put an audio isolation transformer in the line between PC soundcard and
>> Omni 6 audio in
>>
>> 73, Barry N1EU
>>
>>> On Tue, Sep 18, 2018 at 2:41 AM, Stan Gammons <s_gammons at charter.net> wrote:
>>>
>>> Hi Bob,
>>>
>>> I removed the split core I had on the audio cable and put a solid core
>>> with several turns of the the audio cable wrapped around the core at the
>>> sound card output. That drastically reduced the hash picked up from the
>>> PC. So, it should have a MUCH cleaner digital signal now. Now when I
>>> remove the mic and short pin 3 to ground and turn the mic gain fully
>>> clockwise, the rig is putting out maybe 1 watt. Much better than the 100
>>> watts it was putting out when I tried the same thing before! Yeah, it is a
>>> bummer that both are hot all the time. I'll have to remember to
>>> disconnect the cable from the PC when operating phone. Would have been
>>> nice if one were able to select the audio source.
>>>
>>> Thanks for your help. Hopefully I'll sound better when I check into the
>>> net now :)
>>>
>>> 73
>>>
>>> Stan
>>> KM4HQE
>>>
>>>
>>>
>>>> On 9/17/2018 9:25 PM, Bob McGraw K4TAX wrote:
>>>>
>>>> Stan
>>>> Unfortunately that input on the rear is "hot" all of the time and the
>>>> signal (noise) is mixed with mike audio. It is isolated by a 10k ohm
>>>> resistor. The MIC gain and SP level controls both inputs.
>>>>
>>>> You must physically connect one or the other, but never both. There is no
>>>> provision in the radio to select between the two inputs.
>>>>
>>>> I wouldn't bother with chokes as any noise from the computer or interface
>>>> will appear in mike audio. Just the way it works. Bummer.
>>>>
>>>>
>>>>
>>>> Bob, K4TAX
>>>>
>>>>
>>>> Sent from my iPhone
>>>>
>>>>> On Sep 17, 2018, at 9:16 PM, Stan Gammons <s_gammons at charter.net> wrote:
>>>>> Hi Bob,
>>>>>
>>>>> One thing I forgot to check before and I pretty sure I found out what
>>>>> the problem is. I have the PC soundcard out connected to the audio in on
>>>>> the back of the radio so I can use it for digital modes. Seems as though
>>>>> it's picking up hash from the PC and it's getting mixed with the audio from
>>>>> the mic. When I disconnect the cable from the PC, things are normal. Dang
>>>>> it! Guess I need to put another or more ferrite cores on the audio cable.
>>>>> I hear the computer hash when I test PTT with WSJT-X too. So it's
>>>>> transmitting a cruddy digital signal too. That's unacceptable. I have to
>>>>> fix that.
>>>>>
>>>>>
>>>>> 73
>>>>>
>>>>> Stan
>>>>> KM4HQE
>>>>>
>>>>>> On 9/17/2018 8:51 PM, Bob McGraw K4TAX wrote:
>>>>>> Stan:
>>>>>>
>>>>>> First I suggest turning the speech processor OFF and forever leave it
>>>>>> OFF. If you want to use it, just remember, more is worse.
>>>>>>
>>>>>> Even though the mikes worked on the TR7, I view this is no indication
>>>>>> the wiring is correct for the Omni VI. I suggest checking the manual for
>>>>>> the correct mike wiring and physically confirm the mike of choice is wired
>>>>>> correctly. I find mike wiring standards to be as varied as dust
>>>>>> particles in a Texas sandstorm.
>>>>>>
>>>>>> Pin #1 is mike high or mike audio
>>>>>>
>>>>>> Pin #2 is ground and shield. Be sure the shield of the mike cable also
>>>>>> folds back into the Amphenol cable connector to make contact with the shell.
>>>>>>
>>>>>> Pin #3 is PTT
>>>>>>
>>>>>> Pin #4 is +4 DCV for use with an Electrect mike.
>>>>>>
>>>>>> Check the plug in filters on the bottom to see they are seated
>>>>>> correctly and correct location. Again, contact cleaning of their pins
>>>>>> might be in order.
>>>>>>
>>>>>> One other test, disconnect the mike, turn the MIC gain fully
>>>>>> counterclockwise {off}, transmit and listen to the radio. With the 2nd
>>>>>> receiver, tune across the frequency and listen for carrier. In general all
>>>>>> should be quiet. If you hear significant carrier, there is a procedure to
>>>>>> null the carrier. Probably need an oscilloscope and dummy load to do that.
>>>>>>
>>>>>> Next would be to check the frequency of the BFO crystals. Again there
>>>>>> is an alignment procedure. This must be adjusted in the exact steps
>>>>>> outlined in the manual as there is interaction between the adjustments.
>>>>>> Repeat the procedure a couple of times. A frequency counter is required
>>>>>> for this adjustment. Don't skip one step just because you don't intend to
>>>>>> use that mode. There is interaction between the adjustments.
>>>>>>
>>>>>> And of course my last suggestion, which normally is my first
>>>>>> suggestion..........take time to pull each cable, using a Q-Tip moistened
>>>>>> with contact cleaner, scrub the male pins of each and every connector.
>>>>>> Then plug and unplug the connector a couple of times so as to wipe the
>>>>>> female contacts. Do this one at a time and double check to see each
>>>>>> connector is inserted fully and correctly.
>>>>>>
>>>>>> NEVER NEVER NEVER spray anything into the radio. {One fellow I know
>>>>>> [not me] removed the plugin IC's, sprayed into their sockets, and now he
>>>>>> has a radio full of issues and weirdness. Remember contact cleaner is
>>>>>> used to promote the flow of current. Imagine what takes place in a logic
>>>>>> IC socket that is wet with cleaner. ugh!!!! }
>>>>>>
>>>>>> With a radio of that age, it not at all unusual for the electrolytic
>>>>>> caps in the audio stage to deteriorate. One issue which can exist is the
>>>>>> output of a stage can drift negative a few millivolts. In effect it will
>>>>>> reverse polarize the coupling capacitor. The result is after time the 1
>>>>>> MFD cap will migrate to about 0.01 MFD. Not a good path for audio in these
>>>>>> circuits. Makes the radio sound funny too. I always replace the audio
>>>>>> coupling capacitors with nonpolar electrolytics of the same voltage and C
>>>>>> value. There is no need to change parameters. Problem solved. I had a
>>>>>> lengthy discussion with Tentec management and engineering on the subject
>>>>>> some years ago. It almost caused me to not buy a new Omni VI Plus.
>>>>>> Finally, I did and loved it.
>>>>>>
>>>>>> Hope this helps.
>>>>>>
>>>>>> 73
>>>>>>
>>>>>> Bob, K4TAX
>>>>>>
>>>>>>
>>>>>>> On 9/17/2018 8:00 PM, Stan Gammons wrote:
>>>>>>> Hi All,
>>>>>>>
>>>>>>> I was tinkering with an old D-104 T-UG8 that I had put a Heil
>>>>>>> conversion kit in since the original element bit the dust. I ask for an
>>>>>>> audio report from some of the locals that know what I sound like and they
>>>>>>> said I sounded terrible. So, I switched to the Ten-Tec 707 mic, same
>>>>>>> report. So, I tried my trusty old EV-638. Same story. I didn't try it with
>>>>>>> the converted D-104 to see what it sounds like. They initially told me it
>>>>>>> sounded like the mic was picking up something like a fan maybe, so turning
>>>>>>> the gain down helped a little but not a lot. SO, today I decided to put the
>>>>>>> Omni VI on a dummy load and listen to it with my Drake TR7. Yuck! The Omni
>>>>>>> VI sounds terrible! It's almost like there is a little bit of a carrier
>>>>>>> and it has what sounds like digital hash on it. It gets worse the higher
>>>>>>> the mic gain is cranked. When I modulate, the audio sounds all distorted.
>>>>>>> Even without modulation, if I turn the processor on and crank it up, the
>>>>>>> digital hash in the audio seems to get even wo
>>>>>>>
>>>>>> rse. SO, just to make sure it wasn't something weird going on, I did
>>>> the same thing with the TR7. I put it on a dummy load and listened to it
>>>> with the Omni VI. I tried it with the same mics and the audio is clean. No
>>>> hash or anything. Anyone heard of a problem like this with an Omni VI?
>>>>
>>>>>>> 73
>>>>>>>
>>>>>>> Stan
>>>>>>> KM4HQE
>>>>>>>
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