I recently sold an 8 Band EQ to a customer for use with the ORION. Having sold
hundreds of EQ's for use with other TenTec radios we shipped the customer one
of our TenTec 4 to 8 pin mic adapters along with a cable to go between the EQ
and the Orion. This was the first ORION, that I knew about, that the 8 Band EQ
had been connected to. The customer was using a Studio 1 Heil Mic. To my
surprise the hardware shipped would not key his radio. The customer was shipped
another EQ and cables. This did not work also. I downloaded the Orion operating
manual and looked at it. Before the Orion prior Ten Tec radio's had 4 pins mic
configurations where the audio ground and the PTT grounds were shared on pin 2
of the 4 pin mic connector, + audio was connected to pin 1, PTT was connected
on pin 3 and +9 volts DC was connected on pin 4. Figure 2-4 on page 10, of the
Orion manual ,is not the configuration of the 4 pin male connector of the ORION
but a configuration of a mic output without a
connecting cable. Figure 2-5 , I believe was meant to represent the cable
that connects between the mic in figure 2-4 and the Orion input shown in figure
2-3 shown on page 9 of the manual. The key thing to understand is that the
ground return for the PTT instead of being shared with pin 2 is connected to
the shell of the connector. Using the shell connection of the 4 pin mic
connector makes it possible to provide a 5-th signal for mic control (+ Audio,
Audio gnd, PTT, + 9 VDC and PTT gnd) We experienced RFI in the audio when
using a linear amplifier when the PTT and Audio shared a ground. When the PTT
and audio grounds were isolated (the EQ utilizes an audio transformer) the
audio was clean. I have not talked to Ten Tec but I would have to believe that
having to use the shell of the connector was probably something that they
found was needed after the radio was designed. Those of you that have mic's
that share PTT grounds and audio grounds beware. You will likely have an
RFI problem when using a linear. I hope this explains what is going on. I hope
my explaination helps. Thanks to N4VB for making me aware of postings on this
subject Julius (W2IHY)
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