I used the marker generator, which was not available on my first 
receiver, the 75A1, but the crystals in my transmitter, were on yh0 
meters, 3726, on 40 meters 7126Hz and I used a 40 meter crystal to 
triple to 15 meters (don't remember the frequency) but at first that is 
what I had.

My Elmer at the time built a marker generator which went down to every 
25Khz and then all I need do was count up from a known spot or down from it.

My first "talking" radio was a Ten Tec OMNI D with the SSI calculator 
speech chip which was then, amazing!


Curtis Delzer
H.S.
K6VFO
Rialto, CA
[log in to unmask]

On 7/16/2023 10:40 AM, Martin McCormick wrote:
> Those were the days, all right but at the risk of sounding like a
> spoiled sport, did you know that light bulbs aren't a very good
> load for tuning up?
>
> This is kind of wonky but here's what happens with
> incandescent light bulbs.
>
> Try reading the resistance of a 60 or 100-watt bulb with
> an ohm meter.
>
> Of course, you have to do this with the bulb off as you
> hold it in your hand and touch the leads to the screw base and
> the center contact of the bulb.
>
> You will read close to a dead short but ohm's law shows
> that a 100-watt bulb made for 120-volt service should have a
> resistance of about 144 ohms to draw the 0.8333 or 833 milliamps
> current to equal 100 watts.
>
> Whose right? This is where the real world barges in.
> The answer is that there is another factor here that makes a huge
> difference.
>
> Meet the thermal coefficient. It's a law of physics and
> has to do with the effect of rapidly moving atoms versus
> slower-moving atoms.
>
> When you heat metals, their atoms vibrate much more
> quickly when the metal is several thousands of degrees hot than
> they do when it is at room temperature.
>
> When that happens, their electrical resistance in ohms
> goes way up.
>
> A light bulb filament in a cold bulb is at the
> temperature of it's surroundings. Turn on the juice and the bulb
> almost instantly produces normal light because that filament
> reaches maybe 7 or 8-thousand degrees, the temperature of the
> surface of the Sun.
>
> So, when you first throw the switch and the 120 volts
> hits the bulb, the current drawn if you happened to catch the
> peak of a half cycle is possibly scores of amps which would
> convert to thousands of watts using ohm's law.
>
> The circuit that the bulb is on couldn't stand a load
> like that and a fuse or circuit breaker would soon trip to
> prevent burning down your house but that load only lasts for a
> split-second.
>
> The filament probably heats up in a few hundredths of a
> second and presto, the impedance of the bulb goes from almost 0
> ohms to right around 144 ohms. If you connected the bulb to a
> double-pole double-throw switch so that it was possible to take
> the bulb from AC power to the leads of your ohm meter very
> quickly, you would see a 144-ohm resistance that rapidly dropped
> to near 0 as the filament faded to black and cooled down. You
> could actually read the temperature of the bulb if you had a
> chart of the thermal coefficient of that filament.
>
> I strongly suggest not trying this experiment because you
> don't want the possibility that one set of contacts on your
> switch makes before the other breaks which would expose you and
> your ohm meter to a brief spike of AC power which might be
> dangerous but that's what you would see if you could take
> resistance measurements at a rate of several hundred per second.
>
> So, if you use a light bulb as a dummy load, it is
> actually changing resistance as the brightness changes.
>
> It almost goes without saying that the new LED light
> bulbs do not exhibit thermal resistance characteristics so they
> do not cause a sudden spike of current when first turned on.
> Don't try one of those.
>
> Since modern transmitters may have output-reducing
> devices in their final output stages, they might do odd things
> when faced with a light bulb filament.
>
> Anyway, the real world is a spoiler a lot of times when
> it comes to physics experiments but it makes life more
> interesting.
>
> 73 WB5AGZ
> "Chris Zenchenko" <[log in to unmask]> writes:
>> How about a National NCX5.
>> I think that was the model.
>> It belonged to our ham club at the school for the blind In Janesville WI.
>> It had a gear driven dial so it didn't slip and had solid stops at each
>> end.
>> From the counter clock wise solid stop on 40 meters you moved the 
>> crank to
>> the 6 o'clock position then exactly 10 full turns clock wise was 7.1MHZ.
>> The novice band was exactly 5 full turns from there to 7.150MHZ.
>> We had a cheat-sheet in braille on the table near the radio and had the
>> counts for 80 through 10 meters for novice and general band allocations.
>> 300 wats PEP out of it and what a great improvement over our crystal
>> controlled Heathkit DX60B transmitter and military surplus receiver.
>> Before I got my audio SWR meter with tone I used a light bulb mounted 
>> on a
>> short piece of 2by4.
>> With light perception you could dip the plate and peak the drive for
>> brightest light.
>> Using the tone based meter you had a base tone about 100HZ when turned on
>> then you tuned for peak pitch then flipped a switch on the meter to look
>> at
>> reflected.
>> You tuned for least change from base tone with the antenna tuner then 
>> back
>> to forward power and peak again.
>> This is a long ways from today's synthesized radios with auto tuners and
>> SWR
>> protection and at least voice frequency read-out.
>>
>
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