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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