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Building a Capacitor Discharge Stick…Chicken Stick…Jesus Stick

There are multiple ways to build a Capacitor Discharge Stick:

1). Screw drive across the cap and watch the sparks fly.
2). Holding a resistor in a pair of insulated plier and touching the caps needing discharged.
3). Placing your hand or a friends on the caps and hoping for the best.
4). Using a brazing rod wrapped in shrink wrap with a wire connected to an alligator clip.
5). Using two pieces of wire with a resistor in the middle and touching each end of the capacitor.

The only one of those 5 methods I’ve ever used is a trusty screw drive #1 above.

In my search I settled on the following manufactured Capacitor Discharge Stick which is rated to 600 volts. I’ve used it with great success to discharge AC capacitors. A little pricey but it works.

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I wanted to build a Capacitor Discharge Stick (know as CDS from henceforth) capable of discharging approximately 4KV as my amplifiers run 3.5-4KV. In my mind I can’t see an entire Bleeder Resistor board going bad. Therefore most of the voltage would be discharged by the working Bleeder Resistors. That said, better safe than sorry. After thoroughly researching the topic here’s the items I decided upon.

Parts List:
1. Teflon/PTFE Rod 2 foot long 1/2 to 1 inch diameter with at least 5/16 to 1/2 hole down center. Purchased from ZORO. McMaster-Carr has some good sizes as well.
2. Resistor…calculate value needed and then 5 watt or 10 watt. I choose these:
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3. HV wire. I purchased 15KV and 30KV. Ended up using the 30KV rated wire.
4. Probe of some kind. Banana plug, welding rod, old antenna whip whatever works. I settled on these:
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5. Shrink Wrap
6. Soldering Iron
7. Crocodile Clip for attaching to chassis or ground. These are great off Amazon:

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The reason for a hole down the center is that I’m using a 3000 ohm ohmite 10 watt resistor. I want the resistor to solder directly to my probe tip which is a banana plug and then slide it up inside the rod.

The following photos show the build:

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The above banana plug is Flood Soldered and then the capacitor lead inserted.

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Then slide the assembly up the center of your Teflon rod.

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I would greatly appreciate any feedback for ways to improve and what others see as a hazard that I haven’t considered. Yes please tell me if I have a “FATAL ERROR” in my design/project.

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When choosing the value of resistor needed one needs to consider the Ripple Current of the capacitor being discharged. This is provided in the manufactures specifications or can be calculated.

While the above CDS will discharge the dangerous voltage, I use my manufactured CDS for any voltage not discharged. Always verify with the meter on your amplifier or your volt/ohm meter that all voltage has been discharged. Even after that I still use my trusty screw drive to ground the capacitors. Keep in mind that it’s not uncommon for some voltage to develop in a discharged capacitor which is why I use a test alligator jumper to keep the capacitors discharged.

Notes: The hole down the center needs to be large enough for the resistor to slide into. I’ve found that 5/16 is usually large enough. The HV wire isn’t carrying High Voltage because it’s after the resistor. Now if you placed the Resistor at the Crocodile Clip HV is traveling that wire until it hits the resistor.

Most of the time when purchasing wire for around the home or in our autos were more concerned with Amperage rather than Voltage. Amperage is based on guage of wire while voltage handling is based on Insulation of the wire.

Brad
KE0XS
South of Pittsburgh

MFJ 849 SWR/Power Meter

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This meter has always intrigued me. It's costly - $230. And made by a company that sometimes has difficulties with Quality Control. Despite that, I bit the bullet and got one.

The good:

1. Large, 3.5" easy-to-read display.

2. SWR at-a-glance. No time spent adjusting the set point or interpreting a cross needle reading.

3. SWR accuracy appears splendid as readings vary only a few hundredths from those of my RigExpert analyzer. For example:
AA-35 MFJ849
28.300 1.06 1.04
28.400 1.02 1.02
28.500 1.07 1.05

4. Forward power accuracy appears pretty good too. I have no numbers to compare to as my analyzer doesn't measure power. Here are the power settings on the radio compared to the meter readings:
Radio MFJ 849
5 watts 4.86 watts
50 watts 48.76 watts
100 watts 99.92 watts

5. It also displays reflected power.

6. Once you unkey, the readings remain on the screen for a few seconds before reverting to 0.00.

The not-so-good:

1. The meter claims to be a peak reading meter but it clearly doesn't have peak hold. When transmitting on SSB, the numbers jump all over the place. And quickly. o_O Power readings are pretty useless really. Unless you're whistling. The SWR readings jump as well but don't vary by much and are useful. The best results, of course, are determined using a steady carrier like CW or AM.

2. Maximum of 200 watts.

Conclusion? I like it. A lot. (y)

I posted this thread in the Ham Equipment forum as the meter works on both HF (1.6 - 60 MHz) and V/UHF (125 - 525 MHz). But set to HF, it would be great for CB as well. (As long as you're under 200 watts.) :p

Homebrew 1/4 Wave 10 Meter Ground Plane

Easy Peasy. Works great!

Used this: https://m0ukd.com/calculators/quarter-wave-ground-plane-antenna-calculator/

Came up with 98.77" for the vertical. Had a Buddistick shockcord antenna I trimmed to 99 inches. Aluminum tubing or even a crappie pole and wire should work as well.

Attached it to a typical stud connector and mirror bracket atop a 4.5' light stand from Lowes. https://www.lowes.com/pd/CRAFTSMAN-72-04-in-to-72-04-in-Plastic-Work-Light-Stands/1000655903

Used 16 ga. wire for radial. Started with 110" and trimmed for lowest SWR at 28.400 MGZ (10 Meter Calling Channel). Wound up with a SWR of 1.02 using a tick over 100".

Trying to approximate an angle of 76.5 degrees, I attached it to the top notch on my electric fence post. (76.5 is the recommended angle for achieving an impedance of 50 ohms when using a single elevated radial. 45 degrees is recommended when two or more or used. https://www.qsl.net/kk4obi/Elevated Radials.html.)

10 meters is still pretty quiet but opens up occasionally during the day, especially in the afternoons here in north Texas. When it does, it is mostly DX and rarely stateside. :)

10 Meter Antenna.jpg 10 Meter.jpg IMG_1037.jpg IMG_1030.jpg IMG_1032.jpg

An SB-220 needing lots of attention

All,
I have undertaken another long term project. It started in early September and is nearing the finish line now. A local operator I have done work for in the past brought me a Heathkit SB-220 in original but very dirty, neglected and homely condition. (I felt a little sick seeing it for the first time.) Operating condition unknown. He came by it through another local operator who purchased and built the kit while he was living and working for an oil company in Venezuela around 1970. The original owner/builder of this amplifier is in his 90's now and is thinning his collection.
The amplifier has its original set of Eimacs in it and includes the original Heathkit assembly manual with the Eimac warranty card stapled to the inside of the back cover. Interestingly, replacement parts and parts prices at the rear of the assembly manual show replacement Eimac 3-500Z tubes priced at $47.00 each. (Another sick feeling!;))
I have taken many pictures of this rebuild/rehab and will eventually get to the point where I can organize and post them to this thread. For now, I will post a few here for your entertainment.

Day 1, as received.
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A peek in the RF Compartment reveals 30 or 40 years of Pall Mall grunge-hence the sick feeling!
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This is why the Grids should be directly grounded.
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Original Rectifier/Metering board with signs of previous repairs.
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Did I mention that it was dirty?
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As I get the pictures uploaded and sorted/organized on my computer, I will post updates.

73
David

(Airsick bags are not provided by the Author of this thread!)

The Elecraft KPA1500: A Top of the Line HF Amplifier

Earlier this year, I decided to sell my trusty Ameritron AL-800H tube amp so I could purchase the Elecraft KPA1500 solid state 6-160 meters amplifier with built-in auto tuner. Boy am I glad I did.
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My goals were fairly simple: I've been wanting to play QRO on 6 meters for years, and I was looking forward to the experience of changing bands without having to retune both the amp and the tuner. Initially I thought I might be able to eliminate the Ameritron ATR-30 tuner, but I ended up keeping it in line - more on that later.

The KPA1500's rich feature set is intended for use with any modern transceiver. My current HF rig is the Elecraft K3 (upgraded to the K3S), I purchased the matching Elecraft transceiver interface cable. The amp has several interface capabilities but my needs are pretty straight forward. I use the control cable to connect to the ACC port on the K3, the Key In line which runs to the iPlus mic/speaker switch box, the USB interface to my PC, and the requisite coax antenna/input connections.

The rear panel picture shows the additional interface features.
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The ethernet connector provides an alternate control mechanism with the same functionality as USB but is useful for remote operations not involving a remote PC. Most of the other ports are for use with the various brands / types of HF rigs. The TX Sample line is for a future implementation of Pure Signal. Power is supplied by the included 50V power supply which can be positioned up to 10 feet away from the RF deck.

If you hook up the amp to a PC using either the USB or Ethernet interface, you can use Elecraft's KPA1500 Utility app to view everything that is going on. You can also see all of these details using the front panel and controls. Unless there are specific questions, I won't go into all of the intricate details of what is monitored by these controls as the manual is pretty clear and concise.
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Using this amplifier is a complete joy. If you have the amp fully interfaced to your rig, it auto switches bands when you change bands on your rig. The ATU remembers the best setting for a particular "segment" in each band; the number of "segments" varies per band and the number of segments can be configured. When you switch bands using either the rig or the amp front panel, the internal ATU switches to the saved setting for the nearest operating frequency that it reads from the rig. If the ATU is engaged, it will automatically tune if the SWR is higher than the user-definable SWR threshold setting. Note that this frequency tracking feature can be turned on or off and is really useful if you have multiple antennas connected via external switch to each port. If you want to manually initiate the ATU, pressing the ATU TUNE button automatically switches the attached rig to CW mode, changes the rig power level to 20 watts (also user configurable) tunes the antenna, and then switches the rig back to the previous operating mode. It's all very slick.

You can set the preferred antenna output per band, as well as default whether the ATU is engaged by band. As an example, in my station I have a 6 meter M2 3 element beam tuned for the lower portion of the band input to ANT 2. When I select 6m, the amp auto selects the correct antenna and bypasses the ATU. If you have a specific band set to default to a particular antenna port, it will always remember to choose that port even if you later select the alternate antenna.

I have read other reviews that complain about the power supply fan noise. I just don't understand those reviewers' perspective as this amp fan noise is WAAAY less than anything I experienced with a tube amp. The fans on both the power supply and RF deck automatically adjust speed based on internal temperature and when they kick up the speed, they cool things down pretty quickly and settle back down. I just don't find the noise an issue, at all.

The internal ATU is rated to handle 3:1 SWR at 1500 watts and varies from there based on the presented impedance. The amp will require turning down the drive / power output if you exceed the presented SWR limit. I've found that that the ATU will tune up just about anything I give it, and backing the power down from the amp limit will still allow you to operate with considerable power with all kinds of oddball mismatches. When I want to use the amp, I regularly operate around 1200+ watts without worrying about what the internal ATU is doing across the band. On the other hand, my 80 meter antenna has a very narrow bandwidth, which is why I opted to keep the Ameritron ATR-30 manual tuner inline, using it to deliver max smoke from the Elecraft amp while bypassing its internal ATU once the SWR is higher than the Elecraft ATU likes.

One note on linearity. QST published a linearity test between the Elecraft KPA1500 and the ACOM 1200S a few years ago. Here is the graph they published that tells the story on both 20m and 6m:
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The straighter the line/curve the more linear the amp is. These charts show that the KPA1500 amp is quite linear on both bands all the way to its rated power output. Unfortunately, the Acom 1200s doesn't perform nearly as well.

This amp is called a "legal limit" amp, but it will do more than that. In my tests, it appears that the amp has an auto protection trip at 1800 watts. One neat additional trick that you get with the Elecraft K3 (and I presume the K4) is that since the rig knows when you have the amp enabled, it can remember the transceiver power output setting per band both with the amp on and when off. So if you decide to turn the amp on, the rig automatically adjusts the power output to the level last used with the amp on that band. Again, this is very slick.

After using it for the better part of this year, I am still in love with the Elecraft KPA1500. It is not an inexpensive purchase, but this falls into the category of "you get what you pay for". I'm hoping that Elecraft introduces the Pure Signal capabilities soon; that will put it at the top of its class at signal purity.

New M2 6M3 Install: 3 element 6m Yagi

This summer I've been making a few upgrades to the station and now I've installed a 3 element 6 meter yagi on the roof. In the past, I've just tuned my Alpha Delta DX-CC multiband dipole for 6m, but I've been wanting a proper small yagi for quite some time. So I pulled the trigger on the M2 6M3, bought a new rotator and got it on the roof.




While light weight, this antenna is built like a tank and will last for years with little to no maintenance. All of the materials are top quality. The tuning instructions for the T match and element lengths where clear and concise, making the job easy. I added a few Palomar Mix 31 ferrite split beads on the LMR 400 for good measure.

The old TV rotator I used on this vent pipe for the previous 2M antenna was shot (it was pretty old), so it was time to toss in the trash and buy a new one. I picked up a new RCA TV antenna rotator, which has zero problems with an antenna of this size. This rotator is the same one sold through Ameritron and rebranded, but you'll get it for less money through Amazon.




The new controllers have memory buttons. I programed button B for North and J for South, and just went around the compass using the other letters in the grid. Pretty easy.

It would be nice to have this mounted on a tower, but for the home owner in the big city, this antenna mounted on the roof at about 15 feet works remarkably well. Gain is very noticeable over the tuned dipole with a 40' feed point, Plus, the nulls in the antenna pattern really help with unwanted stations. This antenna can handle a ton of power (3KW), which means it makes a nice match for my Elecraft KPA1500 legal limit amplifier.

Here are the specs from M2 for the antenna: