[Boatanchors] WTB: Knightkit T-60 Transmitter

[Rodger Singley]

I suspect a big problem with excess harmonics from the T-60 is that it is likely operating with far excessive grid drive in many cases given the lack of grid current metering and the simple instructions to tune everything for maximum output.  I have too many other projects to get to it anytime soon but I have a T-60 and spectrum analyzer and I will check to see how its harmonic level varies with different levels of grid drive.

Several simpler rigs relied upon slight de-tuning of the driver stage to provide proper drive to the final and the T-60 with a highly active crystal or a higher output VFO like Knight’s own VFO tuned for maximum drive likely provides far more grid drive than needed to the final increasing its level of harmonic generation.

The typical pi network used in a most popular vintage rigs doesn’t provide a tremendous amount of harmonic attenuation which is one of the reasons I use a homebrew L network tuner for my vintage rigs; it provides a low pass filter response in addition to matching.  For comparison to the typical class C rig, Heathkit rated the harmonic output of their SB series gear using properly driven linear output stages at from -35 to -45 db down depending upon model so it is not surprising that vintage rigs using the same fairly simple output network with a robust harmonic generating class C stage produce a lot of harmonic output at the antenna terminal.  Most are prolific harmonic generators but a badly overdriven final amp will be worse and I suspect that describes the typical T-60.

Rodger WQ9E

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From: Grant Youngman<mailto:ghyoungman at gmail.com>
Sent: Sunday, June 21, 2020 2:22 PM
To: Ron VE8RT<mailto:ve8rt at yknwt.ca>
Cc: boatanchors at mailman.qth.net<mailto:boatanchors at mailman.qth.net>
Subject: Re: [Boatanchors] WTB: Knightkit T-60 Transmitter

The Hallicrafters HT-40 has been reported to have some 2nd harmonic problems.  Never encountered any issues with the Globe Chief 90 or various Scouts, DX-40/60 etc. .. And have used all of those at one time or another.

Grant NQ5T

> On Jun 21, 2020, at 2:58 PM, Ron VE8RT <ve8rt at yknwt.ca> wrote:
>
>   Was this true of other novice CW rigs, I'm wondering about my Globe
> Chief 90A?
>
>
>> Hi Rob:
>>
>> You too???!!!!
>>
>> Got my pink slip from the FCC monitoring station in SoCal for working 80/40/20 at the same time! OBTW: I was in eastern Washington (state) at the time!!! Pretty good DX for a Novice running a T-60!!!
>>
>> Vy 73
>>
>> Rich  K7SZ
>>
>>

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