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loss of hf+6 tx

 

HF+6 fault help.
My 4m modded 847 has suddenly developed a TX fault affecting hf&6 only 2/70 are fine. when tx-ing on any hf band or 6 there is about 50% power all modes and a horrid hum/buzz on the output. anyone had this experience?
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Hi Shayne, what current does you 847 take when transmitting, at minimum power out?.
At 5 watts on 6m mine takes just under 10Amps.
I suspect you have a blown HF P/A unit.
Leighton. GW3FSP.
 

The pa itself seems fine It's pulling around 17amps on 6 but if I look at the output via an sdr the emission looks like an over horizon radar on every mode (numerous peaks close spaced and about 300k wide) with or without modulation and shifted some 500k high of the dial frequency. Receive is perfect fine and 2/70 performs normally.
 

Looks like your PA is self oscillating! Check decoupling caps and earthing

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On 19 Sept 2024, 12:02, at 12:02, Shayne Jones <shayne109@...> wrote:
The pa itself seems fine It's pulling around 17amps on 6 but if I look
at the output via an sdr the emission looks like an over horizon radar
on every mode (numerous peaks close spaced and about 300k wide) with or
without modulation and shifted some 500k high of the dial frequency.
Receive is perfect fine and 2/70 performs normally.

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