[MRCA] Gilbert AAR #5

David Olean k1whs at metrocast.net
Mon Sep 30 11:20:34 EDT 2019 

Hello MRCA

Well the picture that appeared is a shot of my display table with the 
REL / Eldico twins.  The proper story is that the military wanted a 
second source for the Collins gear to adhere to contractual regulations 
for the MIL supply chain. An agreement was worked out with Collins, the 
govt, and REL, where the rigs would be produced and sold to the US 
Government for use strictly by the Military in MARS stations. (Collins 
was selling many thousands of S- line and KWM-2s at the time.) From what 
I have learned, only 1500 units were manufactured by REL.  Fast forward 
to the end of the contract, and REL / Eldico tried to sell the same rig 
to hams and Collins complained and made them stop.  I have been looking 
through old CQs and QSTs looking for any ads for the Eldico and the 
S-119 SSB system,  but have not found any yet. I guess this would be 
1960-1963 or so. My rigs all have 1959 date codes on the crystals.

I have restored two transmitters, one receiver, and a bunch of the P-109 
power supplies.  I have the third transmitter on the bench now, but it 
is fighting me all the way.  I lose the TX signal at the high IF 
frequency bandpass coils. I am sure I will find the trouble. The coils 
are OK. I suspect a bad  mica cap in the balanced mixer. I took a break 
from the transmitter, and have been rebuilding all of the power 
supplies. They are really nice quality and it is fun to go through and 
get them running again. The 800 volt supply circuit has two 
electrolytics in series. These are always in need of replacement. At 
least one of the caps has leakage up at the working voltage!  The low 
votage (280V) power supply has a humongous electrolytic cap for a filter 
and no choke as in the HV section.  All of these low voltage caps check 
fine, and I have left them alone. They are very large in size for their 
capacity, 400 MFD at 450 volts DC.  I ran the DC voltage up slowly and 
watch for any leakage. At 450 volts, they settle down and draw no 
current after awihle. When I disconnect the HV, I watch the decay as the 
DC level drops. These things stay charged over night! They have 
discharge curves just like a new capacitor! Out of the six supplies, 
five have the original 400 MFD low voltage cap still working. #6 was 
changed out before I got them.

One modification that I made might be of interest to any hams who try to 
use these rigs on CW. Like the Collins 32S-2, the T-102 uses a 1200 Hz 
phase shift oscillator to generate a tone and introduce it into the 
audio line to generate a CW signal.  This was a poor way to get on CW as 
any distortion in the audio will cause crap and sidebands to appear on 
either side of the CW carrier frequency. If you look at the schematic, 
the output of the phase shift oscillator ( supposedly a low distortion 
circuit) gets routed out to the audio gain pot to generate the tone for 
CW operation. To set the level that is way down from the audio 
oscillator output, they used a 100 pf coupling capacitor.  The teeny 
weeny capacitor attenuates the 1200 Hz signal but allows higher 
frequency distortion products  to pass thru with much less attenuation. 
I could see distortion on the RF signal out of the balanced modulator. I 
replaced the 100 pf cap with a 0.1 MFD cap and a resistive divider to 
knock down the signal to the proper level. The 0.1 MFD cap has a lower 
reactance and it cleaned up the RF distortion by a very noticeable amount.

Dave K1WHS


On 9/30/2019 1:27 PM, Doran Platt wrote:
>
> To continue.... I still have the manuals for the system I had. 
> Apparently  Collins protested the contract and they had to cease 
> production.  Heresay or fact?
>
> Jeep K3HVG
>
>> On September 30, 2019 at 9:24 AM Doran Platt <jeepp at comcast.net> wrote:
>>
>> Yes, the USAF bought a bunch of them, many ended up in MARS 
>> ststions.  I still hav
>>
>>> On September 29, 2019 at 7:29 PM Rich Arland <k7sz at live.com> wrote:
>>>
>>> WOW!! A complete Eldico HF station!! Last one I was 1972 in the Azores
>>> at CT2AA's QTB.
>>>
>>> I need one of those MRCA shirts. Where does one procure one ( or two)?
>>>
>>> Sent from my T-Mobile 4G LTE Device
>>> Get Outlook for Android <https://aka.ms/ghei36>
>>>
>>> ------------------------------------------------------------------------
>>> *From:* mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> 
>>> on behalf of Chance Wolf via MRCA <mrca at mailman.qth.net>
>>> *Sent:* Sunday, September 29, 2019 3:52:07 PM
>>> *To:* mrca at mailman.qth.net <mrca at mailman.qth.net>
>>> *Subject:* Re: [MRCA] Gilbert AAR #5
>>> I started installing my GRC-106 in my own M151A2...got to where it 
>>> appears in the pic here — then sat in the driver’s seat and then 
>>> quickly realized where my head would wind up if I got rearended in 
>>> it (again.)  So, that kind of put an end to that.  I just stuck with 
>>> the RT-524/ KY-57 setup on either side.
>>>
>>> Sent from my iPhone. Probably because I'm outside wrestling wolves.
>>>
>>> > On Sep 29, 2019, at 1:45 PM, MilComm Guy <m38inmaine at gmail.com> 
>>> wrote:
>>> >
>>> > <DSCN0059.JPG>
>>> > Ray's SP 106
>>> > <DSCN0061.JPG>
>>> > <DSCN0062.JPG>
>>> > <DSCN0064.JPG>
>>> >
>>> > ______________________________________________________________
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>>
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>
>
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