Re: External PTT connection

Rich Seifert

On Sep 26, 2019, at 5:57 AM, Bob Hoffmann, K4CQO <rjhoffmann@...> wrote:

I am trying to connect a QRM noise canceler to the unit (using a QRM-180) and I am having trouble getting the PTT relay to switch the noise canceler out of the circuit.

I purchased a cable that is connected to the ACC connection (13 pin plug) with an RCA jack on the other end with a built in relay. However, this is what I am seeing: on VHF the relay is not operated; on HF the relay is operated. This is the case if I transmit or receive -- it does not change the relay setting.

It appears to be set to control using an external amp for HF instead of for VHF -- but I am confused why it does not change when I transmit. Is there a setting that I have to use -- or did I get the wrong cable (the cable is supposed to be good for the ic-7000), or maybe the incorrect way of connecting the ic-7000 to the noise canceler?

The noise canceler uses a ground connection to switch it from receive mode to out of the antenna path when transmitting.
If you look at page 12 of the IC-7000 manual, you will see that there are TWO pins for PTT:

—Pin 3 (HSEND) is normally used for PTT on HF/50 MHz. Pulling this pin low will enable transmit on HF/50 MHz. It will not enable transmit on VHF/UHF.

—Pin 7 (VSEND) is normally used for PTT on VHF/UHF. It works exactly the same as pin 3, but for 144/430 MHz only.

This arrangement actually makes sense. In most applications (particularly mobile), you will use a different antenna for HF/50 MHz than for UHF/VHF. Additionally, the output drivers in the IC-7000 are separate for HF/50 MHz and UHF/VHF.

Now, you can change this behavior in the “Set” menu. What is shown above is the default. Look at page 131 of the manual, and you will see that, under the “Set” menu, you can change the parameter “VSEND Select” to “Off.” In this configuration the HSEND pin on the ACC jack will enable transmit (PTT) on ALL bands. This may be what you want.

Rich KE1B

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