Electronics > RF, Microwave, Ham Radio

Frequence response of through hole resistor vs power rating? (attenuators)

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Hamelec:
if you are pissed you should change your Hobby

coppercone2:
why, its just a shitty old design. You come across some serious trash every decade.

What I will do is throw away the PCB and put a new nice amplifier inside the box with a real attenuator.

Pressing a solder cup into a bent piece of metal and fixing a BNC into an aluminum ring with a set screw is trash. Totally appalled by the construction quality of this amplifier. Made in the USSR I assume.  :-DD

HP got away from this garbage since the 3403C thermal RMS meter, they finally decided a panel cutout going into a can with a properly mounted BNC on it is superior to trying to make thread on VHF electronics based on something that might make sense for a small motor. The design in the HP461A attenuator looks like something someone came up with when they crashed a motor cycle into a dumpster. The best I can figure other then insanity is that sales absolutely demanded that there cannot be a screw on the front panel, and a small sheet metal bracket that mounts it to the chassis properly is too expensive.

Thank your lucky stars someone came up with the idea of a RF can with screws on top that can attach to something with screw holes on the bottom. At least this should only effect the 461 and 462 amplifiers, the 465 is fine. If they put a side ways wafer switch that turns to depress the button on top of the amplifier it would be better too, even if the attenuator is a sad sad construct.


This is literally: drive a nail into the outlet and wedge a coke can under neath

coppercone2:
In case my point is hard to understand...

Mechanism in use by HP461A:


proposed mechanism


I heard the 461A attenuator switch inspired this (original HP designers appeared in this scene wearing suits):

coppercone2:
I think I might have a go at removing the aluminum decapitator from the waffle switch and to mill a slot on the front panel for a lever switch that properly pushes down the attenuator. It might be a good project for the MF70 mill to make a quality mechanism out of brass (I call it the finger) :-DD

Possibly the first useful clock work construct in my lab. I feel a little bad throwing away all those coils in there... but that switch is not acceptable by any means. Maybe I will make a collet on the clicky switch to accept the front panel BNC connector as well.

coppercone2:
I decided to take another crack at it, I wound a spring by drilling a hole in a old damaged eyeglasses repair screwdriver with a carbide drill bit and a proxxon mini sensitive drill press, then I wound a spring around it that I tore out of a broken pen. I used nylon pliers to wind it, and carbide flush cutters to cut it.

I made the new spring lever arm thing out of some kind of alan bradley spare part for something or another for furnaces (piece of spring steel with same dimensions).

I used a oil stone and other stones to smooth out the spring lever, and I plan on giving the guilotine a bit of sanding. too lazy to try to make an alternative mechanism, and I felt bad throwing the amp away

I just need to spot weld a section of screw driver to the lever arm to make a mounting stud for the spring. but after i sanded it down with the diamond file on a leatherman, it does not appear to want to move. I feel like locating the stud is going to be a pain. maybe a drop of epoxy. if I do anything but the natural position its going to want to get jammed.

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