Re: {Collins} 75A-4 Test Procedure - 100 ohm Dummy antenna ?



I agree with Glen. I didn't see him mention, however, that 50 uv will be the standard for S9 instead of 100uv when connected to a modern 50 ohm signal generator. Additionally, I believe your AVC threshold would be set at a lower generator level.

Joe - KB9R


On 1/2/2012 07:08 PM, Glen Zook wrote:
Collins used several different "matching" systems between the signal generator and the receiver.  This was basically done because, at the time, the vast majority of signal generators did not present a true 50-ohm impedance.  Many of the older generators started incorporating a 6 dB "matching pad" to force the output to 50 ohms.  Basically, when using a modern signal generator, or one of the older generators with a true matching pad, you just connect the cable from the generator to the receiver without using anything.  It is only if the generator doesn't have a true 50-ohm output then you have to use the resistor.
Glen, K9STH


Website:  http://k9sth.com


________________________________
  From: john starr001<jstarr001@xxxxxxxxxxx>
To: collins@xxxxxxxxxxxxx
Sent: Monday, January 2, 2012 5:43 PM
Subject: {Collins} 75A-4 Test Procedure - 100 ohm Dummy antenna ?


I got an 75A-4 that I replacing caps, etc and aligning.  The Collins Test Procedure for this radio has several tests that first requires the following:   "Connect the output of the signal generator to the antenna terminals with a 100 ohm dummy antenna in series."  How does one connect "
How do you connect a dummy load and signal generator in series to the radio.  Is this just adding a big wattage 50 ohm resistor in series to a standard 50ohm dummy load?  Why 100 ohms?
tnx and HNY 2012john


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  NETS: Tues&  Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
   SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200 Central
   1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT)

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