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
issues.
73
Bob, K4TAX
----- Original Message -----
From: "Jim Brown" <k9yc@audiosystemsgroup.com>
To: <tentec@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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