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| Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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17th Nov 2023, 6:48 pm
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#1 |
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Pentode
Join Date: Aug 2010
Location: Isle of Wight, UK.
Posts: 224
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AR88 local oscillator
Hello all
the manual for the above specifies the anode voltage for the local osc. [V3] to be 110volts. I find a variation for different bands; Band 1 103v band 2 103v band 3 100v Band 4 97V Band 5 71v Band 6 71v. Is this normal? I cannot find an obvious fault Regards Ian Rose |
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17th Nov 2023, 11:53 pm
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#2 |
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Hexode
Join Date: Nov 2011
Location: Chippenham, Wiltshire, UK.
Posts: 323
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Re: AR88 local oscillator
The anode of the 6J5 local oscillator is fed through two resistors R11 and R12 from the anode of the VR150 voltage stabiliser. The voltage on the 6J5 anode will depend on the current through the resistors, which will vary from band to band depending on the operating point of the valve at that frequency.
Therefore, a variation in anode voltage is to be expected. If the valve is oscillating and the injection voltage to the mixer is adequate, there's nothing to worry about. Peter G3PIJ |
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18th Nov 2023, 11:43 am
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#3 |
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Pentode
Join Date: Aug 2010
Location: Isle of Wight, UK.
Posts: 224
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Re: AR88 local oscillator
Thank you, Peter.
Best regards Ian |
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18th Nov 2023, 11:47 am
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#4 |
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Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: AR88 local oscillator
Also the added shunting effect of the meters capacitance (probes etc) between anode and cathode can affect the anode voltage at higher frequencies.
Lawrence. |
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