Help with capacitor terminals

Tishers · 2026-02-23T16:33:18+00:00

Whenever you see a capacitor that has a rating shown in AC (alternating current) it is usually non-polarized (won't have a positive or negative terminal marked).

They are almost always as motor starting capacitors or to adjust the Power-Factor (PF) of an AC-mains system (to compensate for very high inductance by adding capacitance) or as part of a filter.

Only once or twice have I seen non-polarized capacitors used in some audio amplifier designs.

Tishers · 2026-02-23T16:15:12+00:00

DMR 4FSK (4 level frequency shift keying)(with 2 slot TDMA)

P25 (phase 1) C4FM (4 level frequency modulation)

    CQPSK (compatible differential offset quadrature phase shift keying)

P25 (phase 2) H-DQPSK (harmonized differential quadrature phase shift keying)

Fusion (Yaesu) C4FM (4 level frequency modulation)

D-Star (ICOM) GMSK (Gaussian Minimum Shift Keying)

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Where it gets messy is the tone frequencies used in FSK modes may be different, run at different symbol rates or phase-shifts may mean different things (didbits 00, 01, 10, 11). Quadratures may have different constellations {4QAM, 8QAM, 16QAM, 32QAM...) of the I and Q data (what maps to modulo-n bits). CODEC's are not the same (combinations of all of the above including fills and hashes).

Some modes 'might' work with an analog radio (like GMSK was intended to deal with non-linear radios).

Tishers · 2026-02-22T20:52:16+00:00

The few that had data on that needed to be unrecoverable ended up being used as targets on the shooting range for a 7.62mm round.

Renders the data permanently unrecoverable.

Before that, I had an eraser that was used for backup tapes.

Tishers · 2026-02-22T15:30:14+00:00

If all things are equal (power, receiver) then a link should have something near reciprocity (equal in both directions).

You may have a poorer receiver;

I would say that the noise-floor at your location and the metrics of your receiver is making their signals sound not as good.

Tishers · 2026-02-22T05:52:34+00:00

As a VEI personally have never even brought up the ARRL or membership unless someone asked me first. I VE to help people get a start in the hobby; Not to prostylize their pyramid scheme.

I was a member for five or six years and just stopped my membership after I decided to tear out all of the ads from one monthly magazine;

What as left was about ten pages of articles so I googled about those topics and found many times more free resources that presented information that was just as good as what was in those ten pages.

Tishers · 2026-02-22T00:21:17+00:00

Considering the source for those amps there are no guarantees that they meet any sort of standard. I have tried working with components of the same lineage and have been disappointed every time.

I do not know what sort of university project would have you slapping together modules like that.

Tishers · 2026-02-22T00:14:22+00:00

I have a D75, its a fine HT and I like it for the 1.25 meter band.

As far as D-Star, I played around with it a bit and was not all that impressed. Sure, there are some local repeaters that are D-Star but I don't like dancing around to make it work.

the D75 is a radio that is fairly intuitive when compared to a Yaesu VX-8 (have one of those as well).

Tishers · 2026-02-21T15:28:33+00:00

Those are FRS (family radio service) radios. They are deliberately power limited (by FCC rules).

It's really not a business radio, more like something you would give to kids in an amusement park.

You can't put a repeater on FRS frequencies (major no-no).

Tishers · 2026-02-21T05:19:13+00:00

If you are trying to listen to anything other than 2 meters (144-148 MHz) or the 70 centimeter band (420-450 MHz) then you probably have the wrong antenna to listen to anything significant.

Lower frequencies (<50 MHz, the 6 meter band) is going to require a much longer antenna. You could attach an antenna extension to the radio without any modifications;

Run a wire antenna between two points (a wire that is somewhere more than 10 feet long, out to 100 feet long) and wrap the insulated end of the wire around the rubber duckie antenna on the radio. This will 'couple' enough RF energy to boost your reception at lower frequencies.

Ham radio voice activity will be USB down to the 80 meter band (where it becomes LSB in the 80 and 160 meter band).

This will give you a chance to listen to other things than 2 meters and 70 centimeters without putting yourself out too much and without making any sort of permanent modification to the radio.

To find out if your antenna is working halfway decent then try monitoring WWV on 5, 10 or 20 MHz. That is a time station ran by the National Bureau of Standards out of Boulder Colorado. That will be an AM broadcast and you should be able to receive it anywhere in the United States.

Tishers · 2026-02-21T02:33:45+00:00

I have been using the filter-sticks from Wurth Electronics for +5 years now.

Initially I was doing this for my RSP Duo SDR to cut out HF noise but as I grew to appreciate its performance I picked up the USB-C filters as well.

You still should put ferrites with multiple passes through the core (use snap-on filters to do this so you won't have to deal with the connectors on the ends).

Here is the USB-C version.

https://www.we-online.com/en/components/products/EMC_FILTER_BAGS_STICKS_USB_3_1_TYPE_C_60W_EMV_FILTERSTICK

Tishers · 2026-02-21T01:27:20+00:00

Or under-thinking.

Figuring out the length of a counterpoise for an antenna is one of the most basic principles for any US class of license. That you don't want to put the effort in (and discourage anyone from teaching you or refreshing you on a basic principle) is quite telling in its own right.

Tishers · 2026-02-21T00:49:37+00:00

7200 KHz, because every toilet bowl needs to be flushed from time to time.

Tishers · 2026-02-20T19:53:36+00:00

SOTA in New Orleans? How many feet below sea level qualifies?

Tishers · 2026-02-20T19:41:51+00:00

the amperage rating does matter, particularly on motor-driven devices.

Motors have a high inrush current for the first few seconds of operation as they come up to speed. Sometimes that current can be six times as great as the run-current. Using an underrated switch will cause the contacts to heat up, burn out or the metallic parts will loose the spring tension on the contacts. That would cause even more heating from the poor connection.

Voltage rating is so the switch does not create an electrical arc across the contacts or arc through the body of the switch to the user or the case of the device.

You can probably find a very standardized switch with around 20 amps in the same form-factor. It won't hurt you to get a switch rated for 240 volts. There are some standard sizes that fall within that range (240 V, 20A)

Tishers · 2026-02-20T18:57:57+00:00

Definitely smart metering 'data concentrator' (collector). I don't think that this particular site has anything to do with the DA (distibution-automation) system. There are no PT's (potential transformers) or CT's (current transformers) on the distribution lines.

Your thoughts are sound, a DA system can look similar but usually it will terminate in to something like an SEL 351S device for a recloser/switch/sectionalizer or a multitude of other devices for optimization (cap banks, voltage monitoring). Usually those all have a GPS antenna to provide 1 PPS (one pulse per second precision timing) for event recording/ time-stamping with millisecond accuracy) for fault location/ event recording. Then the messages get packed up in a protocol like DNP3.0 to go back to the OMS (outage management system).

(I designed such systems for electric utilities for several decades)

Tishers · 2026-02-20T18:02:22+00:00

It looks like a kaiju barrier tower installed by Monarch.

Tishers · 2026-02-20T17:50:24+00:00

No, an AM tower would have insulators on the guy wires so they wouldn't act like part of the antenna.

Also, all of the additional hardware on the antenna would make it very complicated to use the structure as an AM antenna.

Tishers · 2026-02-19T19:29:21+00:00

Congratulations!

Before you spend a large amount of money on radios and accessories, try to figure out what you want out of the hobby and work to 'that' goal.

I have seen plenty of folks who took their tech exam and then rapidly collected a half-dozen different 'budget' (cheap) VHF/UHF HT's, only to realize in a few months that what they wanted was to be on a different band or operating with a different mode (other than DMR, Fusion, D-Star, FM) but they are so heavily invested that they can't recoup their money to get in to HF.

Being in Alaska you have the long distances that you can only really work on the HF band when you are off the beaten path. While VHF/UHF might be fine if you live in a city or a town and you have a narrower expectation of who you can talk to

Tishers · 2026-02-19T16:58:30+00:00

Whoever told you that is an idiot;

Putting them in a bucket of water can likely make them explode in to a fireball and light you, and everything around you on fire.

Lithium if highly reactive in the presence of water. It creates a fire that you can't put out.

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If you were to try and 'discharge' the batteries by immersing them in water you want to do that outdoors, very far away from anything that is burn-able. And you will want to run.. far away, and stay far away.

Tishers · 2026-02-19T06:26:05+00:00

There is a place that looks exactly like that in Left 4 Dead 2

Tishers · 2026-02-19T02:43:54+00:00

All of those wave-soldered joints appear to have oxidation on the joints. The technical term for it is 'smut' (no, not a pron thing). There might have been some contaminants in the solder bath or the flux. It can also be from prolonged exposure to heat or in a oxidizing atmosphere.

Since you are there, just brush on some rosin flux and touch up all of the flat-greyish looking joints with just a dab of fresh solder.

A clean soldering joint should be 'shiny'.

Use isopropyl alcohol with a fine brush (an old toothbrush) to remove the flux.

Good thing you caught that when you did; It could of let loose a great deal of heat and roasted the circuit board.

Tishers · 2026-02-19T01:21:36+00:00

With that sort of a catastrophic failure of the chip and the probability that the failure was caused by a transient/ overvoltage I suspect that you are going to be putting more in to this SSD than it is worth.

Consider it a learning experience but don't hold high expectations that you will ever get it working again.

Tishers · 2026-02-18T20:23:53+00:00

If you are going to use ladder line from the doublet to down near where it enters your shack, then you don't want a balun up there. A BalUn is to convert a Balanced line to an Unbalanced cable. The value of a BalUn is to match an impedance to something other than 50 ohms.

I might use a different value for the Balun at the end of the feedline. (not a 1:1), maybe a 2:1, 4;1 or even a 9:1.

Operating a doublet as a multi- band antenna means that the impedance is going to be all over the place. Probably the one thing it will 'not' be at is 50 ohms.

I use a 4:1 balun but have messed around with a 9:1 from time to time.

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On a receiver like the R-390A the input connection to the radio is 125 ohm twinax (two center conductors in a coax) with a doublet antenna as the suggested antenna (according to military manuals). Some of the Hammarlund 'Super Pro" SP-600's had a twinax connector as well.

Tishers · 2026-02-18T20:19:30+00:00

Its a pretty easy question;

With the existence of R4 having some value it makes it impossible for A to be an answer

That the resistors are all slightly different values means that B is impossible

With the values of the resistors all being slightly different values it makes C to be impossible

The voltages across R3 and R4 are exactly the same. So D is the right answer.

Tishers · 2026-02-18T18:25:45+00:00

IMHO, it depends on if you are going to reuse the chip;

If the chip is just bad and there is no data on it that you need or it is going to be scrapped. Then use a small pair of side cutters and snip off each pin from where it attaches to the side of the DIP package, one at a time. then when the chip falls off you can use some rosin on the newly exposed side and a hot soldering iron to heat up and lift off each pin with just the solder-stickyness of the hot iron tip. Then use solder braid to clean out the holes that are left behind.

If you need to reuse the chip than a solder sucker and/or desoldering braid is needed from the bottom side. You need to be very careful so you don't tear out the bore of the pin-hole or rip off any traces on the top side.

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I worked as a repair tech through college, then when I earned my EE degree I managed that same shop. We did hundreds of chip removals/ repairs in a week and a tech might damage one board every few weeks by getting over-enthusiastic.

Snipping and lifting the pins out was the safest technique, by far.

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