Entries Tagged 'HamRadio' ↓

DC Power Distribution

This device is a plug-strip to provide power to devices requiring 12 volt DC power at up to 30 amps.

Such a plug-strip is available commercially but it is somewhat pricey at around $100. I had better things needing my $100 so I built my own plug-strip for about $20 worth of parts.

My plug-strip provides two groups of four 30 amp connectors per group. Each group is protected with a single in-line fuse. One group is powered from an old PS-30 power supply. The other group of four gets its power from a battery that is kept charged by a 100 watt solar cell.

The 8 connectors are held in a groove cut into a block of redwood. holes drilled through the wood block allow the wires to extend to the back of the wood block for termination.

The connectors are glued into the groove using epoxy. Epoxy is also used to glue a sheet of aluminum to the top of the wood block. The aluminum extends past the ends of the block and has holes drilled in the extensions to mount the plug-strip to the underside of a shelf.

Power comes into the block from behind through the in-line fuses. The wires are soldered to the mass terminations formed by the connections from the individual power connectors.

Make sure the connectors are working properly before being glued into the wood block. The silver plated tongue of the connector must be inserted far enough to engage the the metal leaf spring in the bottom of the connector housing. Otherwise the act of inserting the mating connector will push the tongue back into the housing an break the electrical contact.

Insulate all terminations with heat shrink or electrical tape. All interconnects need to be soldered.

I saw no need to fuse each plug-strip location individually but it could be done that way if you want. Just buy six more in-line fuses and holders.

Note that the fuses protect the battery and power supply. They are not designed to provide protection to devices plugged into the plug-strip.


Instead of gluing a mounting strip to the power strip, we used shoe goo to glue the strip to the top of a removable metal sheet that is used to protect the desk surface. This was far easier and simpler than trying to install the strip at the back of the underside of the shelf.

Power connections to the srip were made using two pin molex connectors. The connectors were keyed to ensure connections could not be reverse polarized and provision was made to ensure the power sources could not be interchanged. Solar/battery power could only be supplied to one set of four sockets and PS-30 power could only be supplied to the other set of four sockets.

Light/Dark Activated Switch

These are switches used to turn on lights at dusk and turn them off again at sunrise. Generally, a light sensitive device like a photocell, optical sensor of some sort is ties to an opamp comparator which energizes a relay to switch on the lights. A less sophisticated approach might be a simple mechanical timer. The timer does not need to sense light levels.

An even simpler solution is to use a low voltage mechanical relay energized by a solar panel. This approach assumes that a solar panel system is already in place. Even a 5 watt panel can develop enough power to energize a 5 volt, 150ma relay without significantly effecting its ability to provide useful electrical power.

For the solar panel solution to work reliably the relay needs to be sensitive enough to energise even on a cloudy day or the lights will stay on. Also, the relay needs to provide both normally open and normally closed contacts. The idea is to allow the solar panel energy to turn ON the relay which turns OFF the lights.

To prevent the 18 volts from the panel from over powering the relay a series resistor and 5 volt zener across the relay will keep the relay coil at a maximum of 5 volts. A capacitor across the relay coil would introduce some hysteresis to prevent the relay from cycling on and off at certain light levels.

The rig is so good, it is used by DXpeditions

So goes the sales pitch for a well known amateur radio manufacturer. To be fair, that radio is superior to most. It is sensitive, selective and can be used in crowded RF environments. Why it can even resist blocking interference from a ham next door running full legal limit. Is that really what is needed on DXpeditions?

DXpeditions go to remote locations, are assigned rare call signs, and operate where they are the only radio signal for many miles around. They don’t need special super equipment to make contacts because hundreds of distant hams are going to be falling over themselves for contacts with their rare calls and distant locations. These DX enthusiasts will be using high power and directive antennas to push as much signal as possible toward the DXpedition. The DXpedition is not going to have any trouble hearing them. So what is the real reason DXpeditions prefer that particular radio?

Turns out that the company making the claim offers their radios to DXpeditions free of charge!


You may already know that reasonable cost factory radio repair does not exist. Read on for proof.

If your radio acts up or stops working and you can’t fix it yourself, your best bet is to sell it as an as-is non-working parts radio and buy a new one. Maybe, this time, select a brand that is less likely to fail.

Here is why this is your best option.

If your radio was made by one of the big three (ICOM, Yaesu, Kenwood), good luck. Even if you do get an rma chances are the radio will be shipped back to you with a note that they could not duplicate the problem. Of course you will be able to duplicate the problem and the rig will join the many offered for sale after just having been to the factory and serviced. You can compensate the round trip shipping and $100 evaluation fee with whatever some poor fool pays for your nightmare radio.

Why do they do this, you ask. Because you are one of thousands in a nich market of toy hobby radios. The manufacturers don’t make any money repairing. The make money selling. They also know you will most likely buy another of their radios since you have already demonstrated that you don’t have the ability to repair the one you have.

I know of two personal experiences with radio problems. One involved an Omni-D. It was sent to the factory for service. They replaced two electrolytics and a resistor. The repair charge was $250 plus round trip shipping. At the time the radio was worth $500. The total cost of the service came to close to $300. A sick Omni-D could very likely have fetched $250. Add that to the $300 that was wasted and you would have had half the price of a new and more capable rig.

The second horror story involves a portable rig that got fried by a power supply failure. it was sent to the factory for repair. The factory promised repair after five weeks due to a backlog. Less than a week after they received the radio, they called back and declared it unrepairable. They implied that there might be some surplus boards available to replace the bad ones in the radio but the boards in the original radio were beyond economical repair.

A few days later I got an email from their sales guy offering me a replacement radio for 75% the cost of a new one, or I could pay them for three hours of technician time at $100 an hour. No mention was made as to disposition of my broken radio but they did declare that the replacement radio was only warrated for six months.

My first inclination was tell them to stick it where the sun does not shine.

After I declined their offer, they offered to reassemble my busted radio for an additional $100. This was getting close to ass kicking time!!!

I ended up talking to someone in sales that had a brain. I explained that I had no problem paying a tech $100 an hour as long as he was worth $100 an hour. A person who takes 3 hours to conclude he cannot repair something is only worth $30 an hour.

So I ended up losing a total of $160 for round trip shipping and worthless tech help.

I also have a pretty good idea why the factory used radio only carried a 6 month warranty. They buy the boards from a board manufacturer (possibly off shore) who gives them a 12 month warranty. The boards in the radio they were offering me were already six months old hence the six month warranty.

This may also explain why this radio is available as a no-solder kit. The soldering is done in a reflow furnace by their board manufacturer. Surprisingly, the radio is also available as a factory assembled radio at $100 more than the ‘kit’ price.

I have no problems with the radio. It is/was superior in all respects. I do have a problem with the sort of nonsense their sales guy tried to pull. Having lost all respect for this manufacturer I look forward to not having to do business with them in the future.

Solar Power

I have had a small 50 watt solar system up and running for about two years. It keeps a single 12 volt automotive 24F class battery charged. The system provides power to light and run a modest 2 meter ham station located in my bedroom closet. The station is on all the time monitoring the local repeater.

Recently I have been considering adding a more capable solar system to compliment the 1KW emergency gas generator in the generator hut.

My interest in solar was raised when I discovered 100 watt solar panels priced at under $150.

The solar panel is not the only thing you need to build a solar power system but at $1.50 a watt, it becomes competative with gas powered generators.

So I bought a single 100 watt solar panel. It has been cloudy for the last two days since the panel arrived but even with light overcas the panel produces 20volts open circuit and 2.5 amps lighting the large filament of an automobile brake light.

The final system will have four 100 watt panels connected in series to produce up to 80 volts. Provision will be made to route the 80 volts to a 1000 watt sine wave inverter. The inverter costs $100 and will provide over 300 watts of 120vac 60 cycle power when the sun shines.

Antenna Switches

Over time I have used a number of tower based antenna switches. They all worked but were never able to select between morew than four antennas.

These switches were controlled through the coax feedline by using chokes and capacitors to isolate the control voltages from the RF energy. This seemed to work even at high transmitter power levels but the additional components required to do this would certainly have an adverse effect on reliability over time. I did not need another toy to repair at some future date so I decided to run a separate control line to power the relays used in my antenna switch.

By using a tower mounted antenna switch I need only one coax feedline from the shack to the tower and I have relatively short feedlines runs from the switch to the five antennas. Otherwise I would need five long feedlines into the shack, one for each antenna. The antenna switch more than pays for itself in money saved buying coax. The main downside is that you can only use one antenna at a time.

So if you own more than one ham rig, you can’t use that other ham rig on the antennas connected to the antenna switch when they are in use by the main rig. That is actually a good thing. Two rigs in close proximity and running power could easily blow each others front ends.

There is one valid reason for running more than one feedline to the shack, diversity reception. That is using two receivers one one a vertical and the other on a horizontally polarized antenna to enhance reception.

My antenna switch uses three 12 volt 30 amp SPST relays and a four conductor control line. Two of the relays have thier coils wired in prallel to act like a DPDT relay. They are wired just like the Heathkit four position antenna switch but use an additional SPDT relay. The extra relay takes the normally #4 antenna selection and translates it into #4 and #5.

The control cable is an old landline phone line. It has red, green, yellow, and black conductors and is dirt cheap. Power to the relays is 14 volts provided through diodes and a rotary switch at the operating position. The diodes isolate the five selections needed to provide proper sequencing of the relays.

Key Line Isolation

Interfacing the keying line to an amplifier used to be very simple in the old days when transceivers used a spare set of contacts in their TR relays to do that job.

Today modern transceivers use solid state switching to key external amps. The solid state switching is quieter making QSK operation much more pleasent. Solid state switching is also less capable of handling the higher keying voltages found in older amplifiers.

There is no shortage of interface circuits to solve the problem. You can build your own or purchase ready made devices available at under $100.

We do not like spending our money on ready made devices when we can build them ourselves. We also dislike external boxes with their wire leads cluttering the operating area. So we build our own and install the circuit into the transceiver if at all possible. We feel the keying problem is caused by inadequate transceiver keying ability, not excessive amplifier keying requirements. Besides, if you have more than one old amp and you don’t want to build more than one higher voltage keying circuit, the circuit needs to go into the transceiver.

Most decent interface circuits use fets, transistors, and diodes. The diodes isolate the amp from the transceiver, the fets switch the higher amp keying voltage, and the transistors control the switching fet. All this circuitry can be replaced with one small relay. The relay provides superb isolation but introduces time delays that might effect QSK operation.

The circuit we employ uses opto isolators which provide the superior isolation while preserving high speed keying.

A 4N35 is energized from the transceiver keying line. As the keying line goes to ground, it takes the cathode of the opto LED to ground causing the LED to illuminate the opto output transistor. The output transistor collector goes to ground taking the positive bias off the PNP fet driving transistor. As the base of the PNP transistor goes to ground, it conducts and allows a positive voltage to arrive at the gate of the fet. The fet turns on and keys the amp.

Custom Control Console

This concerns antenna switching and SWR measurements. For convenience the switching and measuring is best done close to the operating position. Perhaps in a console located right next to the radio.

We have built such a console. It contains a multipurpose power supply, a 100 watt linear amplifier, an SWR/Power meter and controls, and switches allowing selection of three antennas on each of two coax feedlines.

Initially this supply was intended to provide power for a small solid state linear amp and some LED lighting. The amp was for use with the KX3 to boost its 10 watts to a level better suited to drive a larger linear close to full power. The small amp needs 24 volts at up to 3 amps. A 5 amp linear regulator was used to supply the 24 volts.

The transformer in this supply is capable of delivering at least 500 watts. A second 5 amp regulator was installed to provide 14 volts to the KX3 and LED lighting. Additional 1 amp regulators were installed for 12 and 5 volts. The 14 and 12 volt sources were brought out to the back panel through PowerX connectors.

The power amplifier is an EBY design using a pair of IRF540 fets. It covers all bands. A band switch is provided on the front panel. The amp is built into the console along with the power supply. This amp is not protected and must be used cautiously.

This is an old heathkit meter that can measure up to 2000 watts. Its sensing unit is located remotely to make antenna cabling more convenient.

There are two switches mounted to the front panel. One for each of two coaxial feed lines. The switches are double pole double throw with a center off position. The switches are connected to remotely located power and coax interface boxes through four wire shielded cable.

These switches route power to antenna relays located on the antenna tower through the coax feed lines. Plus polarity, negative polarity, and power off, select one of three antennas through the relays.

This system is patterned after a Heathkit remote switch which allowed selection of four antennas. The fourth selection was accomplished by feeding AC to the relays where two half wave rectifiers and filter capacitors activate both relays simultaneously. I could not make the AC feature work with the relays I used so I ended up with only three antenna selections.

Both feed line isolators and their power supply are located near the two amplifiers they serve. The amplifiers are located on the floor below the desk. The remote isolators are mounted to the back of the desk.

A patch panel located below the center console allows connection of any number of radios to the amps. When the amps are not powered up or set to standby, the radios are connected directly to the antennas.

Soft Key – where to install it

References to Soft Key are normally found in articles dealing with linear amplifier modifications. The Soft Key circuitry is most often installed in amplifiers whose design incorporates high voltage bias to fully cut off the tubes when the amplifier is not keyed.

Typically this bias voltage is around 120 volts. This value is conveniently chosen to provide full cut off as well as current needed to actuate the 120 vdc antenna changeover relay. By taking the relay return to ground these amps activate the relay while also removing the cut off bias. So by a single connection to ground we route the exciter input to the amp input, route the amp output to the antenna, and remove standby bias all at the same time.

The only problem here is that the 120 vdc keying line needs a device that can handle 120 vdc at 10 to 30 ma.

That is not a problem with exciters that provide a relay closure to activate the keying line. Modern solid state exciters may not provide relay closures. Those that don’t may not be able to handle 120 vdc.

Recently I bought an exciter that will not handle more than 40 vdc at 20 ma.

If I install Soft Key in the amp, that amp will be the only amp I can use with the new exciter. I do have other amps. All the amps I have work well with all the older exciters I own. I do not want to install Soft Key in every amp I own to make them all safe to use with the new exciter.

That is why I will install Soft Key in the new exciter and enable its use with any amp.

Since the new exciter is portable, its use with other amps (amps I may not own) is a very real possibility.

The Soft Key circuitry will operate off 14.8 vdc. The same 14.8 vdc that runs the exciter. The soft key output is a high voltage switching transistor. The Soft Key circuit is conveniently mounted into the same box that contains the 2 amp hour Lithium ion batteries that can be used to run the exciter as a portable.

To prevent damage to the exciter in the event of failure of the Soft Key circuitry, Soft Key circuitry uses an opto isolator between the switching circuit and the exciter.

Do I still want a KWM2?

I recently saw a KWM2 and speaker power supply offered for sale for $1500. As little as twenty years ago I might have considered buying it. Today I would rather spend that sort of money on a KX3 and PX3 from Elecraft. Below is a list of capabilities the Elecraft radio provides that are not available in the KWM2.

Adjustable speed keyer
RTTY transmit and receive with scrolling readout
PSK31 transmit and receive with scrolling readout
CW transmit and receive with scrolling readout
160 to 6 meters including WARC bands
effective DSP
100 memories to hold freq and mode info
notch filter
audio peaking filter for CW
noise blanker
multimodes AM, FM, CW, RTTY, PSK31
speach compressor
SWR indicator
Power indicator
integrated panadapter/w color waterfall and spectrum displays of up to 200 khz of any band.
The panadapter turns the rig into a spectrum analyzer.
audio equalizer for custom audio response (TXandRX)
audio compression for microphone
digital voice recorder
easy interface to computer controlled operation.
general receive from below the broadcast band to the high end of 6 meters.
Optional antenna tuner
optional 2 meter coverage
optional 70 cm coverage
portable battery operation
enough power to drive a linear amp to 200 watts output.

These features make the KWM2 look like the obsolete boat anchor it has become.

All is not lost. A KWM2 can be made to include most all of the features listed by adding external equipment. Unfortunately the additional equipment required will cost upwards of $1000. Since we can get all those features for around $1500 from Elecraft that limits the price we can pay for the KWM2 to a maximum of $500.

Add to this the very real possibility that a 60 year old KWM2 is probably in need of having its electrolytic capacitors replaced, we are looking at another $200 to $300 expenditure to bring the old rig up to spec.

So, do I still want a KWM2? Yes, but I am not willing to pay more than $200 for one and that includes the speaker power supply.