[MRCA] GRC-106 Pin J

Sat Sep 3 22:16:07 EDT 2016

Well then we will have the first "documented" trial of the GRA-39 with 
the GRC-106.
Z

On 9/3/2016 9:59 PM, Al Klase wrote:
> Gang,
>
> I don't know much about the 106, but, as someone pointed out verbally, 
> the the 50-ohm (carbon) mic input, pin 17, hits a 10:1 voltage divider 
> before it joins up with the 600-ohm input, pin 16, at test point J1.  
> In other wards the carbon mic input is attenuated 20 dB.  Looks to me 
> like they were anticipating supporting dynamic mics in some application.
>
>
>
> Figure FO-18, page 634 of the TM 11-5820-520-34 PDF from radio Nerds. 
> http://www.radionerds.com/images/4/4e/TM_11-5820-520-34.pdf
>
> And, from page 29:
>
> *1-14. TRANSMIT SECTION CIRCUIT ANALYSIS. (CONT)*
> A. Audio Amplification.
> The audio intelligence is applied to either pin 17 or pin 16 of 
> connector J1. Pin 17 is the input for
> carbon microphones, and pin 16 is the input for dynamic microphones. 
> Resistor A2R1 is used to
> connect the required dc bias to the carbon microphones. Capacitor A2C1 
> is used to block the
> microphone bias from being applied to transmit audio attenuator A2Q1. 
> Resistors A2R2 and A2R5
> provide a voltage divider to reduce the higher input levels from the 
> carbon microphones to one
> near that of the dynamic microphones. Resistor A2R5 also provides the 
> 50-ohm termination for
> the carbon
>
>
> I'll bet they were anticipating the new family of audio accessories.
>
> My two cents,
> Al
> Al Klase – N3FRQ
> Jersey City, NJ
> http://www.skywaves.ar88.net/
>
> On 9/3/2016 9:04 PM, B. Smith wrote:
>> So it looks like using  using break out boxes for the connectors and 
>> feed audio out from the GRA-39 C-2229 to pin "J" will drive the 
>> GRC-106 mic input. Kinda like to figure this out now and not at 
>> midnight at Gilbert after the pop corn Walt ?
>> That will be the basic plan but wondering if we will have enough 
>> drive? -- perhaps have a small amp for the mic line on standby?
>> Z
>>
>> On 9/2/2016 6:16 PM, Tom B wrote:
>>>
>>> I should have added that pin J is NC on the H-33.
>>>
>>> Tom
>>>
>>>
>>> On 9/2/2016 6:11 PM, Tom B wrote:
>>>>
>>>> According to the GRC-106 manual, the dynamic mic input goes 
>>>> directly from 1A5 to pin J on both audio connectors J18 and J19.  
>>>> It looks to me like you could easily make it work with the GRA-39 
>>>> with the correct cable.  It looks like only one wire is moved.
>>>>
>>>> I have some cables here that have two U-228 connectors and one U-77 
>>>> but I don't know what they were made for.  It would fit the GRC-106 
>>>> for this application but I am not sure what these were for.
>>>>
>>>> I have seen a similar cable for the PSG-2.
>>>>
>>>> Tom
>>>>
>>>>
>>>>
>>>> On 9/2/2016 5:59 PM, WA5CAB--- via MRCA wrote:
>>>>> It is still listed in SB 11-6 (FSC 6135 Primary Battery Supply 
>>>>> Data) dated 28 May 1982.  I don't have anything more recent.
>>>>>
>>>>> But TM 11-5820-489-nn do not all date from 1983 through 1987.  The 
>>>>> initial manual of the series, TM 11-5820-489-35P (which replaced 
>>>>> SIG 7 & 8 AN/GRA-6) was dated 11 June, 1962.  TM 11-5038, which 
>>>>> originally dates from 18 April, 1951, wasn't replaced by a 
>>>>> long-number version until some time after Change 7 dated 16 May 1967.
>>>>>
>>>>> Robert Downs - Houston
>>>>> wa5cab dot com (Web Store)
>>>>> MVPA 9480
>>>>>
>>>>> In a message dated 09/02/2016 16:01:41 PM Central Daylight Time, 
>>>>> RAFANTINI at salisbury.edu writes:
>>>>>> The TM 11-5820-489 family of books all date from 1983 to 87 so 
>>>>>> the AN/GRA -6 family of products were still in production and use 
>>>>>> around the same time as the AN/GRA-39. I would speculate that the 
>>>>>> GRA-6 was kept around just for that fact that it would directly 
>>>>>> support the AN/GRC-106 family of radios. The GRA-39 always 
>>>>>> appeared to be a newer and better box but maybe the more 
>>>>>> primitive GRA-6 had its place?
>>>>>>
>>>>>> Will have to look and see if I can find production dates on my set.
>>>>>>
>>>>>> How long was the BA-414 (45 volt B Battery) available???
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Ray F/KA3EKH
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>>
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