[TenTec] Orion II Transmit Audio issue(s)...
w3idt at comcast.net
Wed Dec 22 17:48:10 EST 2021
Now that I have the Master Reset issue under control with the
installation of a fresh battery (and the earlier A9 board capacitor
upgrades), I still have two, possibly related, transmit audio issues.
One of them I think I know how to fix, for the other I have no clue. And
I wouldn't dismiss that the issues are related.
1. Though the first issue may appear to be RFI related, a) this radio
used to sit next to an Alpha something amp with 1500W going to low
dipoles very near the shack without any RFI problems, and 2) the radio
now works fine on CW and FSK/RTTY at full 100w without any RFI problems.
Transmitting in any audio mode, whether SSB/FM/AM via the front panel
mic input or FT8 via the rear panel input, any transmission above about
5 - 10w power kills the receiver. Cycling the main power on/off brings
the receiver back to life. Sometimes, though, on an immediate power
cycle the receiver is still dead; waiting a minute or so allows the
receiver to wake up.
This suggests to me that some component is heating up beyond its
specifications... but a transmit component affecting the receiver?
I have no clue.
2. I have a 35KW AM BC station on 1260KHz 1KM (3500') feet away, and I
have a custom BC filter with an 85+dB notch at 1260; Its 3rd harmonic at
3780 KHz is barely perceptible. I don't hear the station when receiving.
However, when I go to transmit in SSB/FM/AM (that is engage PTT) I don't
hear it either unless I have the signal monitor function engaged even
with only a Heil adapter plugged into the front panel input.
With a Heil headset mic plugged in to the adapter, the BC signal is
strong enough to modulate the transmission, often high enough to trigger
problem (1) above.
To me this suggests that the BC station is being rectified even in the
short length of the Heil adapter cable, and even more so in a normal
length mic cable. But, strangely, not in the earphone part of the Heil
The solution would seem to be to create a custom mic adapter wound
around a special low frequency toroid (type 77).
. Robert F. Teitel, W3IDT
. w3idt at comcast.net
. w3idt at arrl.net
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