I would suggest wiring the HC-5 direct and bypass the amp in the G stand base.
The purpose of the amp was to provide a very Hi Z load to the original crystal
element, about 3 megohm, and to provide a Lo Z source to solid state radios in
the order of 10k ohms.
The HC-5 should drive the mike input of the Omni VI adequately and without
issues.
Bob, K4TAX
Sent from my iPhone
> On Sep 18, 2018, at 10:15 PM, Stan Gammons <s_gammons@charter.net> wrote:
>
> Yes, 9 o'clock on the mic gain seems to be about right for the EV-638.
>
> Think I'll put the 707 on shelf next to that Vibroplex bug... :) I may tinker
> with the converted D-104 some more. I think the Heil conversion uses the
> HC5.1 element. Not sure how that element will work with the amplified
> D-104's.
>
> I'll try the L pad and bonding the computer chassis to station ground.
>
> Thanks Bob.
>
> 73
>
> Stan
> KM4HQE
>
>
>> On 9/18/2018 9:55 PM, Bob McGraw K4TAX wrote:
>> I've found typically the mike gain runs 9 o'clock to 10 o'clock on these
>> radios. Yes the 707 has much lower output and will require one to raise
>> the gain a considerable amount. My 707 sits on the shelf with my original
>> D-104. They "look good" sitting there, which is where I prefer they remain.
>>
>> I fought the computer interface issues to my Paragon and my Omni VI series.
>> Both have the same type of input on the rear where the mike audio and the
>> rear connector audio are summed together through a pair of 47K resistors on
>> the TX audio board.
>>
>> The better solution I found was to build a resistive L pad with about 20 dB
>> loss. The 1/8 watt resistors were mounted in the shell of the RCA
>> connector which plugged into the rear connector. This required I raise
>> the level out of the computer sound card but in doing so, I improved my
>> transmit S/N ratio about 20 dB. This is worth doing regardless of your
>> final decision. Makes for cleaner digital signals and allows easier
>> adjustment of the audio out of the computer for transmit level control.
>> This allowed me to keep the mike gain at the 9 o'clock position. Just be
>> sure the mike connected to the front is off so that any room noise being
>> picked up is not transmitted.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>
>>> On 9/18/2018 9:43 PM, Stan Gammons wrote:
>>> For now I'm just going to disconnect the sound card output from the PC when
>>> operating phone. I did try another core at the sound card output and for
>>> some strange reason that made matters worse. One core on each end of the
>>> cable reduces the hash/noise a lot. Only when I have the mic gain around 1
>>> o'clock do I notice the increase in output when I have the rig keyed
>>> without a mic attached. Normally, I run the mic gain around the 9 o'clock
>>> position. I don't believe Ten-Tec 707 has as high an output as the
>>> Electro-Voice EV-638, but 9 o'clock on the mic gain seems to be Ok with
>>> either mic. The 707 is pretty, but I like the EV-638 as much or more.
>>>
>>> I don't have the PC chassis bonded to station ground. I'll mess with that
>>> this coming weekend.
>>>
>>> Thanks for all the replies.
>>>
>>> 73
>>>
>>> Stan
>>> KM4HQE
>>>
>>>
>>>> On 9/18/2018 9:25 PM, Greg S via TenTec wrote:
>>>> 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@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@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@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
>>>>>>>>>>>
>>>>>>>>>>> _______________________________________________
>>>>>>>>>>> TenTec mailing list
>>>>>>>>>>> TenTec@contesting.com
>>>>>>>>>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>>>>>>>>>
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