[600MRG] IC735 mods...an alternative

[John Molnar]

Neil's approach is a good one.  A cap across an inductor forms
a 'suck out' of a specific frequency and if designed to kill 950 kHz
is very effective.  With reasonable Q inductor and good quality cap it's
easy to obtain a -50 dB or better notch with steep skirts at 950...

John WA3ETD

On Fri, Jan 26, 2018 at 10:48 AM, Neil Klagge <w0yse at msn.com> wrote:

> I too have taken that drive around The neighborhood to listen to my second
> harmonic on 950 kHz. Adding 1750 pF across one of the inductors in the LPF
> of my GW3UEP amplifier squashed the harmonic down to almost nothing.
>
> Neil, w0yse
>
> Sent from Neil's iPhone
>
> On Jan 26, 2018, at 07:41, John Langridge <kb5njd at gmail.com> wrote:
>
> >Since the target frequency is below 160M, why would harmonics be much of
> an issue with the 160M LPF?
>
>
> Second harmonic of 475 is 950, which is in use in many BC markets...
> 473's third harmonic is right around 1420...
>
> Many of us have taken the drive of shame where we activate our stations on
> WSPR or CW and still hear our signals on 950 kHz many miles away.  Never a
> good thing.  Adding one of the W1VD-designed filters made it where I
> couldn't hear myself sitting in my drive way.
>
> 73,
>
> John
>
>
> On Fri, Jan 26, 2018 at 9:32 AM, J Mcvey via 600MRG <
> 600mrg at mailman.qth.net> wrote:
>
>> Got $9 in the budget?
>> https://www.mouser.com/Passive-Components/Frequency-Control-
>> Timing-Devices/Oscillators/_/N-7jdfi?P=1z0woad
>> just add 3.3 to 5V , a cap and a filter if you like...
>>
>> Those Ic735 mods mostly seem to extend the PA capability downward in
>> frequency.
>> Not sure what shorting the transistor in receive section  was about but
>> those were my initial impressions.
>>
>> The LPF might need some tweaking for 630M. I think going all the way down
>> to 2200 meters is too much of stretch, though.
>> I might try before and after tests with a spectrum analyzer to see what
>> happens when I get time to do it.
>>
>> Since the target frequency is below 160M, why would harmonics be much of
>> an issue with the 160M LPF?
>> Add a 630M section in series with the 160M LPF?
>>
>>
>> On Friday, January 26, 2018 7:53 AM, N1BUG <paul at n1bug.com> wrote:
>>
>>
>> >> Why ruin a perfectly good radio???
>>
>> If I'd had a IC-735 around that wasn't being used on HF, I probably
>> would have 'ruined' it in a heartbeat. That would have been the most
>> cost effective way to get on.
>>
>> With a little help to keep it within budget I build a really cheap
>> transmit converter. But since a good stable 10 MHz oscillator isn't
>> happening here for some time, I'm using a signal generator that I
>> would prefer not to leave running for so many hours. So even now, if
>> I had a 735 that wasn't needed for HF I'd dig into the little
>> bugger... ;-)
>>
>> 73,
>> Paul N1BUG
>>
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