开云体育

A majority of acceptance is not proof of correctness.

开云体育

开云体育

开云体育

开云体育

Sorry in advance if this has already been done.? I know people will often connect up a VOM to measure the voltage drop across the 10 ohm resistor in the PS-120 or PS-500 power supplies to monitor the Plate idle current.? As most know 0.7V for an equivalent 70mA current.

I was contemplating a noninvasive method to provide a better ‘almost’ direct plate current measurement.? By noninvasive, I mean using the same 10 ohm resistor in the power supplies via their Tip Jack connections.?? Then it dawned on me, I have a decent assortment of meters, so why not use a 0-500uA meter and simply divert 1/1000th of the current going through that 10 ohm resistor.? Robbing 1/1000th your plate current will go without notice under normal operation.? For 200mA of plate current I’d be diverting 0.2mA of current, barely noticeable.

Found a nice vintage Triplett 500uA FS DC meter in my junk box.? It was actually NIB!??? The schematic couldn’t be simpler.? I have essentially around 10K of adjustable resistance in series with the meter and it gets connected to the same power supply TIP jacks that everyone uses to monitor the idle & plate current (via voltage).? Even though the schematic shows a 5K fixed resistor and a 5K pot, I naturally used a 4.7K resistor and a 10K series connected (recommended) pot.? Ain't much current going through these components so high wattage is not of concern.



Calibration is supper easy.? Either using a DC power supply or even a low voltage, one to three volt, battery connect the meter circuits leads to the DC source.? Then adjust the pot to correspond to which you measure with either your VOM or better yet with a decently accurate DMM.?? So for a battery that measures 1.5VDC you would set the meter to read 150.?? Once adjusted it will never need adjustment again!

I installed the meter in a case, I also had lying around, and painted it in a similar two tone Hallicrafters gray, or the best I could get using off-the-shelf spray paint.? Notice, I just added a decal to the front of the meter face that indicates the reading is X1000.? So 70 on the meter is 70mA, 200 is 200mA, etc.



No more old VOM’s needed and I have a continuous noninvasive method for monitoring the plate current on my personal SR-150 transceiver.

73
Don N9OO

开云体育

开云体育

开云体育

A majority of acceptance is not proof of correctness.

开云体育

开云体育

Why does every one forget the SX 32 lol.

73 tony WA4JQS

So I decided to ask Gemini AI assistant the question about flywheel tuning in Hallicrafters receivers, how many had it.? The interesting answer is below.

While it's challenging to provide an exact count of all Hallicrafters shortwave receivers that featured flywheel tuning without access to a comprehensive historical database of every model and its specifications, we can identify several prominent examples known for this feature.

Based on available information, here are some Hallicrafters shortwave receivers that incorporated flywheel tuning for smoother operation:

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?? Hallicrafters SX-28 "Super Skyrider": This is a well-known receiver and its tuning mechanism is described in detail, explicitly mentioning the use of heavy flywheels for both main tuning and bandspread. The design allowed for rapid spinning of the dial across the bands using the momentum of the flywheels.

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??? Hallicrafters SX-28A "Super Skyrider": As a successor to the SX-28, it's highly likely that the SX-28A also retained the flywheel tuning system, as it was a highly regarded feature of the original.

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??? Hallicrafters SX-88: This top-of-the-line receiver from Hallicrafters also featured gear-driven tuning knobs weighted with heavy flywheels, contributing to its smooth tuning feel.

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1. Hallicrafters SX-88 and SX-99 - DXing.com

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? Hallicrafters SX-96: This model is described as having "smooth flywheel tuning," indicating its inclusion of this feature for ease of operation.

It's important to note that flywheel tuning was often a characteristic of higher-end communications receivers as it provided a more refined and user-friendly tuning experience compared to direct drive mechanisms. Therefore, it's plausible that other models in Hallicrafters' lineup, particularly those marketed as "Super Skyrider" or high-performance communications receivers, also included flywheel tuning.

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The more basic or entry-level models, such as the Hallicrafters S-38 and S-120, are generally not noted for having flywheel tuning. Reviews of the S-120 specifically mention the lack of a flywheel and the effort required to tune across the bands. The service bulletin for the S-38 details the dial cord stringing without any mention of a flywheel.

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To get a more precise number, a detailed examination of the specifications and features of each Hallicrafters shortwave receiver model produced would be necessary. However, the SX-28, SX-28A, SX-88, and SX-96 are confirmed examples of Hallicrafters receivers that utilized flywheel tuning.

K2WH