[TenTec] Does this happen to you on transmit...OMNI V ??

Bob McGraw - K4TAX RMcGraw at Blomand.net
Mon Feb 24 21:21:37 EST 2014

Jim mentions the RCA connectors on the rear.  Please understand the Audio IN 
on the rear is the same exact input only isolated by a 22K resistor from the 
mike input on the front.  Anything that is connected to the Audio IN on the 
rear, when using the mike, may allow RF into the TX audio.  Unfortunately, 
from experience, one must use one or the other but not both unless you are 
asking for trouble.   Later radios provided a selection for the MIC input or 
the Line/Aux input.

On coax jumpers and connectors, today's connectors typically are lacking in 
quality although the plating is "pretty".  I always snug the PL-259's with a 
pair of 4" channel lock pliers that reside at the desk.  I've found that 
finger tight is simply not good enough and is often the source of RFI 

Bob, K4TAX

----- Original Message ----- 
From: "Jim Brown" <k9yc at audiosystemsgroup.com>
To: <tentec at contesting.com>
Sent: Monday, February 24, 2014 7:02 PM
Subject: Re: [TenTec] Does this happen to you on transmit...OMNI V ??

> On 2/24/2014 2:56 PM, Bob McGraw - K4TAX wrote:
>> Initially seems like a RFI issue to me.
> Might be. Suggestion #1 gets both to that and the PS voltage issue.
>> 1. Try it on a known good dummy load with a known good jumper between the 
>> radio and the load.
>> 2. Make sure the DC power connections and connectors, both on the cable 
>> and at the radio are solid, clean and tight.
> I also smell too much voltage drop in the DC supply.  What is the supply? 
> What is the DC cable between PS and rig?  What cable diameter and length?
>> 3. Make sure the power supply voltage is correct at the radio and thus 
>> the PS regulator is not falling out of regulation.
>> If it works on #1 then it is likely the antenna or the associated jumpers 
>> connecting various pieces of equipment.
> Yes, poor quality coax jumpers can do this.  Anything from crummy coax to 
> poorly installed connectors -- even junk connectors.
> Back to the "RF in the shack" issue -- the Omni V has Pin One Problems at 
> all of the RCA connectors on the rear panel, and may have one at the mic 
> connector too.  RF feedback is CAUSED by Pin One Problems. If our  antenna 
> is working and is close to the shack, we WILL have RF in the shack, but it 
> is the job of our gear to reject it. Pin One Problems COUPLE RF into our 
> gear. Any cable plugged into a connector with a Pin One Problem, including 
> those RCA connectors, becomes an antenna coupling our TX RF back into the 
> rig.
> Study k9yc.com/RFI-Ham.pdf and the other stuff at k9yc.com/publish.htm 
> that talks about Pin One Problems.
> 73, Jim K9YC
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