My ex-wife’s kitchen comment was always, “If you can still tell what it is,
it’s not done yet!”.
I installed a smoke detector in the kitchen - I used it as a dinner bell.
She did, however, create in me a taste for blackened fish…blackened chicken…
blackened eggs…
The oven had a nickname - the incinerator.
A friend asked me why I bought a sand blaster. I told him “My job is to clean
the pans!”.
She had a few recipes that made it into a very famous and important book - The
Handbook of Hazardous Materials.
Once she dropped some food on the floor. I asked if she was going to pick it
up. She said "No, the mice will eat it”. I said “No, they have other options!”.
> On Feb 28, 2019, at 2:06 PM, Mike Bryce <prosolar@sssnet.com> wrote:
>
> Whoa!
>
> That’s a great catch. I’d never would have suspected the Jones filter to
> cause a transmit issue. Are you producing full RF output now?
>
> Only once did I find a shorted .01 capacitor and that was in a Drake W4
> wattmeter. I found one of the old micas (the rectangular shaped ones with the
> dots) that was dead short in an old tube audio amplifier.
>
> Working with these old radios reminds me of my ex-wife’s cooking—Every bite
> was different!
>
> mike, wb8vge
>
> “The trouble with quotes on the Internet is that you never know if they are
> genuine”
>
> —Abraham Lincoln
>
>> On Feb 28, 2019, at 2:27 PM, MadScientist <dukeshifi@comcast.net> wrote:
>>
>> Thanks!
>>
>> I now find that, no matter how long I work on stuff like this, I never stop
>> learning new things! I guess that’s part of the reason I do it.
>>
>> This Scout came to me with “no transmit”. It did receive.
>>
>> I made measurements on the driver stage, based on the schematic, and found
>> the “base" voltages to be quite far off (greater than 0.7 volts base to
>> emitter) so I assumed that the devices, which at the time I thought were
>> bipolar transistors, according to the schematic so I assumed that they were
>> bad, possibly from an oscillation problem, so I ordered replacements using
>> the numbers on the devices that were in the radio. I had no reason to
>> question whether they were bipolar or FET’s since the schematic was quite
>> clear on this matter.
>>
>> Then, in an effort to test the calibration of my signal generator and
>> attenuator for checking sensitivity of an Omni 6 I am repairing, I found
>> that the Scout had very weak reception, only showing about S 9 at 0 dBm! You
>> could still hear signals but touching the center of the unterminated coax
>> connector only produced a barely noticeable hiss, not the screaming noise to
>> which I am accustomed in my noisy basement shop.
>>
>> I concluded that the receiver also had problems. After a long and
>> frustrating evening of following the signal from the antenna terminal to the
>> IF board, through the filters etc., I found that the Jones filter was
>> attenuating signals by about 40 dB!
>>
>> Thanks to a reference on one of the ham sites, I found a link to the patent
>> for this filter. That gave a detailed schematic and technical description of
>> the filter so I decided to try to fix it. I terminated the ends with 50 ohms
>> and applied my spectrum analyzer’s sweep generator to the input and followed
>> signal through the filter with the analyzer’s input.
>>
>> I didn’t have to go very far. Much to my surprise, the 0.01 uF ceramic
>> capacitor coming from the input terminal to the first crystal was dropping
>> 40 dB from one end to the other.
>>
>> Now I have never in my life seen an open ceramic capacitor, especially in
>> low level circuits like this. I have seen them explode in TV high voltage
>> supplies and in electron microscope supplies but never in small signal
>> applications.
>>
>> I replaced the cap and got exactly the passband shown in the patent at all
>> control voltages, with only a few dB insertion loss.
>>
>> Then after I reinstalled the filter into the radio I checked for TX drive at
>> the input to the predriver transistor. I found that I had drive to burn! So
>> the Jones filter was the culprit all along!
>>
>> Put this one into the archive…
>>
>> Gary
>>
>> W0DVN
>>
>
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