[Milsurplus] Fwd: Re: OT ?

Thu Oct 9 12:29:44 EDT 2014

Hi All,
Just a small update.  While I was able to get new connectors from Bill Perry, the avionic guys are no help.  They will sell a whole manual for $165 but will not take the time to even copy the pin-out (at a price of course).  So, I am still searching for the wiring diagram for this out dated civilian RT if anyone can lend a hand or direct me to a true source for the diagram.

Thanks for all the suggestions, I wish the folks in this industry were as helpful as they are in the mil radio business.

Regards
Bruce

________________________________
 From: Glen Zook via Milsurplus <milsurplus at mailman.qth.net>
To: "nerd at verizon.net" <nerd at verizon.net>; "milsurplus at mailman.qth.net" <milsurplus at mailman.qth.net> 
Sent: Friday, September 26, 2014 7:33 AM
Subject: Re: [Milsurplus] Fwd: Re:  OT ?

Aviation shops may have changed.  But, a number of years ago, at least around here, a goodly number of them did not know their posteriors from a hole in the ground.

I got talked into purchasing a Cessna 150 during the time period when I owned the Motorola reconditioned equipment center for the south-central United States.  The aircraft was an i.f.r. trainer and had 2 NAVCOM radios, and so forth.  The main radio had terrible modulation, but so did a number of other aircraft at the airport.  This radio had been checked out, numerous times, at each of the 3 radio shops at the airport, paid for by the previous owner when he owned the aircraft.

It soon became apparent that something had to be done.  So, the radio was "pulled" and brought to the reconditioned equipment center.  Since myself, and a number of my employees, had the required FCC licenses to service the equipment, this was perfectly legal.  I had one of the technicians work on the unit.  Almost immediately, he found an electrolytic capacitor, in the modulation circuitry, that had been installed backwards, by one of the airport radio shops probably several years before.  Replacing this capacitor got rid of the distortion.  Why the mis-wiring of the capacitor went unnoticed, for years, is beside me!

Next, the microphone was replaced with a Motorola noise cancelling microphone.  That really improved things.

Before kluging up a test jig to measure the modulation percentage (we dealt with FM, not AM, and didn't have such readily available), I telephoned each of the 3 aviation radio shops at the airport to ask them how they measured modulation.  The owner of the first shop didn't even know what I was talking about!  He didn't know that it was possible to measure the modulation percentage, didn't know that it really should be done, and didn't care about it at all!  The owner of the second shop admitted that he knew the modulation should be checked, but he didn't bother to measure it.  The owner of the third shop actually did measure the modulation percentage, at least at times.  When asked how he did this measurements, he told me that he had a meter, that had been built by a former employee, several years before.  He had absolutely no idea how it worked, it had not been calibrated since the employee quit, but he did use it, at times!  Needless to say, we rigged
up a test jig and did our own checking!

After putting the radio back in the airplane, we called the FAA tower for a "radio check".  The controllers were very familiar with how the radio sounded before and could not believe that it was the same radio.  Out of several hundred general aviation aircraft hangered / tied down at the airport, the controllers said that it was the best "sounding" of them all!

They requested that the airplane be taxied over to the tower so that each controller could come down and actually see what had been done and ask questions.  That was done.  The controllers were amazed that just by getting a mis-wired component replaced, and then by changing the microphone, that such a drastic improvement could be made.  It was "mentioned" that maybe a "talk" should be had at each of the radio shops.  But, since I didn't have anything to do with those shops, I don't know if anything came of that.

Glen, K9STH 

Website:  http://k9sth.net

On Thursday, September 25, 2014 10:53 PM, Peter Gottlieb <nerd at verizon.net> wrote:

I've had better luck, not only getting diagrams but having them save gear for me 
that they would have discarded.

I guess it really varies.  I've run into shops that had such a bad attitude I 
wouldn't bring work there.  Ask around with aircraft owners.

PEter

On 9/25/2014 11:46 PM, Bruce Gentry wrote:
>
>
>
> -------- Original Message --------
> Subject:     Re: [Milsurplus] OT ?
> Date:     Thu, 25 Sep 2014 23:40:18 -0400
> From:     Bruce Gentry <ka2ivy at verizon.net>
> To:    nerd at verizon.net
>
>
>
> As a collector of older aircraft radios, I have had aweful luck with
> avionics shops.  They are often so full of themselves their noses are so
> high in the air as to be a hazard to navigation. I hope and trust there
> are also good decent ones around that might help you. I tend to resort
> to EPAY.  One caution- aircraft radio manuals are often broken into two
> or more very compartmentalized manuals.  Ask the seller  about EXACTLY
> what is in the manual you are about to buy. I have bought manuals,
> waited for them, and when they arrived, found the diagram or schematic I
> desperately needed was not included.  The seller gushed with apologies
> and assured me they would be glad to provide  supplement XKZX-7492, for
> a "nominal" fee, of course!   Buyer, be hyper aware!
>
>       Bruce Gentry, KA2IVY
>
>
>
> On 9/25/14 11:21 PM, Peter Gottlieb wrote:
>> Do you have or use a plane?  If so, ask at the avionics shop.
>>
>> Peter
>>
>> On 9/25/2014 10:05 PM, Skywarrior via Milsurplus wrote:
>>> Hi all,
>>> I am looking for a wiring diagram for the commercial Cessna ARC 1000
>>> RT-1038A VHF aircraft radio.  I need to make a wiring harness to
>>> connect the control head.  I have had no luck finding such through
>>> many searches.
>>>
>>> TIA
>>>
>>> Bruce
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