[TenTec] Popping Noise from Orion and Centurion

[Ken Brown]

Hi Toby,

If the popping occurs when you are not generating 1 kW of RFfrom the 
amp, and not even generating 60 or 100 watts from the transceiver, then 
I think it is reasonable to conclude that the problem is not transmitter 
RF getting into somewhere that generates the objectionable popping. I 
have been assuming that the pops occur at keydown (or PTT) and then 
another pop again at key up (or release of PTT), do you really mean that 
there is a continuous stream of popping all the while that the key (or 
PTT) is closed? That is not the way I was interpreting it at first.

By relay coil current switching, I mean the switching of the current 
that actuates any tranmit/receive relays in the amplifier. Since it is a 
Ten-Tec amplifier and is QSK capable the relays are keyed hard and fast 
to minimize relay closure time. The current to the relay coils is 
switched by transistors or other semiconductor switching devices, which 
ultimately are controlled by the keying control line from the 
transceiver. The transition from zero current (relay not activated) to 
full current (relay actuated) has a slope with a short rise time and 
possibly overshoot and ringing. The overshoot and ringing (resonance of 
inductance of relay coil and other inductances and capacitances in the 
circuit) can make a pop that can be heard over a wide frequency range. 
The circuit should be damped sufficently to prevent this. If certain 
components failed or changed value, the relay actuation circuitry might 
still function, and make RF pops at the on and off times. This would not 
explain a continuous stream of pops while the relay remains actuated.

Similarly if the HV plate supply, or any other power supply in the 
amplifier that has a current which is switched with a steep slope (high 
slew rate) and has ringing this could generate a pop. I think this is 
rather unlikely, not impossible. With no drive there should be not much 
plate current being switched, and no pop. Something funny with the 
switching of the tube bias from idle bias voltage to operate bias 
voltage might generate a pop.

Does the audio volume control effect the pop loudness? The pop is coming 
from the transceiver speaker or headphones, right? Not something you 
hear in the room and not from the audio output of the receiver? Does the 
band you are operating on make a difference in the strength or character 
of the popping sound? Do you have a good ground connection (other than 
the sheilds of coax and control cables) between the transceiver and the 
PA? What if you disonnect the PA from the transceiver completely and key 
the amp with something else, still hear a pop in the Orion RX Audio? Or 
leave them hooked up normally and listen with another receiver. Does it 
hear a pop too?

DE N6KB

Toby Pennington wrote:

>Ken,  Thanks for your thoughts on the popping.  I am using paddles for keying the rig and amp.  In the menu it is called SSB:CW Jack PTT.  This in effect keys the rig and amp on SSB but puts no power out unless I talk into the mike.  So, it doesn't matter what the power setting is on the Orion,  the popping is still there as long as the amp is being keyed.  When the amp is not being keyed, no popping is noticed.  I also can use the PTT button on the mike and the same results occur. So, the pops are still there when I am not generating any RF at all.  Simply just keying the rig and amp with no output.........Of course, when i talk into the mike the pops are there also.  Same popping occurs when using  VOX.  So, in summary,  just keying the rig and amp with no output at all produces popping.
>
>When you say, "keying the load on the power supply" I assume you are referring to the supply in the amp?  Also,  explain where"relay coil switching" occurs.
>
>One of my first thoughts was RF getting into the keying line, but I hooked the dummy load directly into the amp and could still hear the popping, but it was not as loud.  So, it is is RF, then it is being internally generated and not coming from the antenna.  
>
>Thanks for your help!   Toby W4CAK
>
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