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From: Tauno Voipio <tauno.voipio@notused.fi.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Valve frequency multipliers
Date: Sun, 9 Feb 2025 18:32:23 +0200
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On 9.2.2025 12.23, Liz Tuddenham wrote:
> legg <legg@nospam.magma.ca> wrote:
> 
> 
> [...]
>>
>> I'd be more selective of the crystal frequency. Two triplers might get
>> you there with a lot less grief.
> 
> You were right: with a crystal frequency of 16.656 Mc/s and two triplers
> the results are much better.
> 
> New block diagram:
> <http://www.poppyrecords.co.uk/other/Transceiver/BlockDiag6c.gif>
> 
> New oscillator circuit:
> <http://www.poppyrecords.co.uk/other/Transceiver/XtalOsc4c.gif>
> 
> The stages are: EF91 Reactance, EF91 Oscillator, ECC91 Tripler+ tripler.
> 
> The new crystal necessitated changes to the component values in the
> 'pulling' circuits, but the basic concept remain unchanged.   Over large
> frequency swings the reactance valve characteristic appears curved but
> with 0dBm audio input at 400 c/s  there is no audible distortion and the
> frequency swing is around 15 Kc/s pk/pk, which is three times larger
> than the permitted deviation in the amateur bands.
> 
> I tried putting a parallel-tuned circuit in the anode circuit of the
> oscillator, to resonate at the third harmonic, but there was very little
> signal, so I decided to use one triode of the ECC91 as the first
> tripler.  I then resonated the anode tuned circuit of the oscillator at
> crystal frequency but discovered that this made it unreliable at
> start-up.  Eventually I found that just an aperiodic [untuned] anode
> choke gave plenty of drive to the grid of the first tripler and allowed
> the oscillator to start reliably.
> 
> The parallel-tuned circuit of the first tripler and series-tuned circuit
> between the second tripler and the output cable both have comfortably
> gentle tuning, which is an advantage because they should hold their
> settings without adjustment for a long time.  The output voltage is only
> around 300mV rms into 75 ohms, but this can be stepped up when it gets
> to the mixer grids by a further resonant circuit.
> 
> 

Are you sure that the crystal lets you pulll it by 11 kHz and add angle
modulation to it?

Please design and verify the 144 MHz transmit and receive filters
associated with the mixers for enough attenuation on the 150 MHz band.

-- 

-TV