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.
Ever since I repaired a TS-850 for a close friend I have been wanting a TS-850 of my own. I do have a TS-950 and the TS-850 appears just as good and considerably lighter in weight. On top of that I know how to keep it running.
Like many Kenwood radios, you can get them with or without certain options. The ATU is one such option and raises the price of the radio. Is an antenna tuner really needed? It is only needed if you don’t have antennas and feedlines that ensure an impedance match to your radio. The ATU will ensure a match to the feedline at the operating position. That keeps the transmitter happy but could make the operator unhappy as the power is dissipated as heat in the transmission line.
You are much better off using well designed, resonant antennas. They radiate better, more efficiently and also ‘hear’ better and you don’t need an ATU to use them.
Depending on condition the 850 is worth from $500 to $600 if it is electrically perfect. Trouble is, even new out of the factory, some of these radios were not perfect. That makes their value on the used market below $500. Unfortunately most sellers of this radio do not agree and ask prices that take them out of the used equipment market.
Recently I have come to the conclusion that it is more enjoyable to play with new radios than to try and repair some sick broken toy that no one wants.
Sure, I can repair it and make it work but it is still an old toy looking for a place to die. It is just not worth the time it takes to keep the old stuff working when the new stuff works better and does much more.
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
100 memories to hold freq and mode info
audio peaking filter for CW
multimodes AM, FM, CW, RTTY, PSK31
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.
K2 or K3 or KX3 or TS-950SD ?????
Too late for the KX3 and TS-950SD. I already have one of each. I am currently considering a K2 or a K3. Recenly I decided it would have to be a K3.
In order to get the K3 I would sell the TS-950SD and a couple of linear amps to fund the purchase of the K3.
When I told my wife the good news she had several questions I could not answer.
“What is wrong with the new KX3? I thought you were happy with it. Is the K3 so much better that you have to sacrifice to get one?”
Well, I had to admit that the only thing I knew for sure about the K3 was that it came in a bigger box.
“If the K3 is better, maybe you should sell the KX3 instead of the 950. Is there something wrong with the 950?”
After having ooed and ahhed over it for the last three days there was no way I was going to sell the KX3. Right now I had it driving the old TL-922 amp and getting about 200 watts to the antenna with superb audio reports on 40 meter sideband while using the MH3 Elecraft hand mike.
After sleeping on this exchange of ideas I have decided not to sell the 950. There is nothing wrong with the 950SD. It is not a 950SDX but there is little operational difference between the two. Besides, the SDX had some problems with cold solder joints and uses higher voltage finals that some think are not as good as the ones used in the 950SD.
The 950SD came out in 1989 priced at $3800. Today it is worth $950 as a used radio but its performance is still equal to a 1989 $3800 radio.
I still want a K3 but I am not going to dump the 950 to get one.
The Kenwood has three variants of the TS-950 series Transiever, the original two TS-950 S (100 % ANOLOG)and TS 950 SD (DIGITAL TRANSMIT) were released in 1989, it was available as a “S” stock radio, without the Digital Hang Under unit,and with only minimal number of crystals installed or as the “SD” Digital version, which had the added Digital Hang Under unit I think its Part # was a “D-10 unit” The 950 SD came loaded with all the filter options as a completed Maxxed Out Top of the line Transiever. Those two Radios came with low voltage trans Finals, and You could remove the digital unit and filters or add the filters and D-10 package to make it more or less fully complete, The outside of the TS 950 S and the TS 950 SDRadios are identical, you could make one into the other and visa-versa. Then about two years later the released the 950 SDX radio which is a totally different radio altogether , it did not come stock with all filters installed and it had a Menu Driven from the outside front knobs along with I think 50 volt Trans Finals. You can upgrade a 950 S to a 950 SD, but you could not do a upgrade of either. to turn them into a 950 SDX. I hope I have those details correct. 73′s Terry McCoy
I have tried many radios but none have more pleasant listening audio when the bands are open. One of the most sensitive receivers I have ever had. The best mix of analog and digital so it sounds great all the time. I have tried the TS-950SDX and it is a nice radio too, but not better enough to warrant the extra few hundred dollars. Most of the 950SDX radios have been modified so much and with the cold solder problems kenwood admitted to, it’s hard to find a nice reliable one anymore. A newer more modern DSP radio can dig the signals out of the noise better when the bands are not good, but still not very pleasant to listen too. If you are not using it for contesting and you just enjoy spinning the dials when the bands are fair, you will be very happy rag chewing with this radio. I’m like a child on Christmas morning every time I turn it on and it just looks great sitting in front of you (still a very modern looking after over 25 years)!
I also have the TS-870S. It too is a great radio. The receiver on my TS-950SD is a little more sensitive, but the TS-870S IF DSP is a little better at bringing the signal up out of the noise when the bands are not great. The TS-950SD is easier to search the bands as the TS-870S does not have direct band jumping buttons, it does however have band up and down buttons that will scroll thru the bands in order. The biggest difference between them is my TS-950SD has the 120 vac power supply built in and it does not operate on 12 vdc. The TS-870S operates on 12 vdc only, making it a much lighter and smaller radio (no power transformer). The TS-950SD has 150 watts output on ssb and the TS-870S has 100 watts output on ssb, but most stations I talk to cannot tell the difference because the TS-870S does a great job with the DSP giving it a more pronounced (hot) audio. Do not let this be a deciding factor when considering either radio. I use ssb only. I can not comment on the CW difference, but most reviews I have read like the TS-870S better for this mode.
These are solely my impressions and are based on unmodified radios. They are both truly great radios ahead of their time (thanks to Kenwoods great engineers) and if you cannot decide, just get both like I did!
I will add a PX3 to the KX3 and learn to use that combination along with my laptop before even thinking about a K3 again.
A week ago I became the owner and user of a new KX3 transceiver.
I use the KX3 in a fixed station application powering from an old reliable PS-30 power supply. I run the KX3 at maximum power and use it to drive a TL922 amplifier to about 250 watts on 40, 20, 15, and 10 meters. I frequent those bands because I have resonant antennas covering those frequencies.
I am also blessed with three other linear amplifiers each could easily bring my signal up to the legal limit but I have not found a need to do that.
The KX3 has spoiled me. It is superior in all respects to any and all rigs I have ever used since starting in ham radio in 1959.
I was reluctant to commit over $1000 for the KX3 but it was worth the investment. Actually the KX3 purchase was funded from proceeds from the sale of equipment I no longer used so there was no out of pocket financial burden.
My satisfaction with the KX3 has fueled a desire to acquire a K3. I would sacrifice my TS-950 and one of the better linear amplifiers to help fund the purchase of a K3.
The questions now are, K3 or K2? New or used?
A K2 is priced at half the cost of a K3. You can buy two K2s for what you would have to pay for a K3.
The following information from Elecraft has helped me decide in favor of the K3.
> …what is in the K3 that requires 4x more current? What do the additional current consumers contribute to the operation of the radio?
The K3 has the following stages that add both current and features or performance advantages:
- high-dynamic-range, dual-conversion superhet architecture with heavily biased mixers, post-amp, etc.
- multiple stages of high-bias PIN-diode T/R switching and other PIN-diode path switching
- high-performance 32-bit DSP I.F.s for main and sub receiver
- large, brightly lit LCD with dual VFO displays, alphanumeric display for text decode, etc.
- four multi-function encoders, each with two LED indicators
- ATU that uses non-latching relays to maximize tuning speed
- digital voice recorder (DVR)
- high-power stereo AF amplifier
- misc. support and I/O circuitry (not found on the K2)
This isn’t a comprehensive list, but you get the idea. Yes, it’s more current drain than a K2, but we were able to provide excellent performance and a wide range of features in the K3 while consuming 1/2 to 1/4th the current drain of most transceivers in its class.
The KX3 is another interesting point of comparison. Its receive current drain is about 200-250 mA, typically, while providing the highest performance of any ultra-compact transceiver by a wide margin.
The only decision point left is to decide on buying new or used.
Used prices asked for K3 and K2 are only a few hundred dollars less than the new prices. Two or three hundred dollars is significant when considered on its own. It looses some significance when compared to a $1000 or $2000 purchase. If you can justify spending one or two thousand dollars, an additional $300 is not that much of a stretch. Especially when that additional cost buys you minty new gear fresh from the factory with all the old boo-boos and blemishes fixed and updated. Buying new also gets you a factory one year warranty. Most factories are reluctant to warranty used equipment they have not seen even if it was originally built by them. For that reason warranties are not usually transferable.
Also, you have to wonder why someone would sell his older equipment. People don’t sell off equipment they cherish. People sell equipment to fund the purchase of something better. We all seek something better and hope for the best. You don’t get there by accepting discards even if they are superior to your present equipment.
No, I don’t buy into the idea that they need the money. People in financial difficulty usually need far more than a few thousand to ease the pain. You just cant get rich selling radio onesies.
I used to lowball my hobbies. I embraced QRP not because it was ‘fun’, but because it was cheap. At least it was cheap in 1959 when you built your own from parts salvaged from TV sets and radios found in the dump.
Imagine my horror to discover QRP prices that rivaled the cost of ‘real’ radios. That cured me of my lowball approach to ham radio.
I was not turned into a spendthrift. I still require value for money spent but I no longer search for parts in the junkyard.
I appreciate useful features over bells and whistles. Bells and whistles make noise and draw attention but they don’t become features until someone finds them useful.
The K3 provides useful features that are worth the extra expense. Factory fresh, minty new, updated and current features under warranty are also worth the nominal additional cost.
So when am I going to order a new K3?
First I need to divest myself of a TS-950 and the linear amp that goes with it. I need to find someone with money and the physical strength to lift that equipment.
Is a ‘Rebuilt’ SB-220 worth $1300?
The rebuilder certainly thinks so. If you go through his laundry list of repair items you will find that he does have at least $1300 tied up in the rebuilt SB-220.
Unfortunately that does not answer the question as to worth. Unwise investments seldom attract wise buyers and it is the wise buyers that have the money.
We need to investigate the linear amplifier market. What else can we find for $1300?
Found, a used but operational Alpha 76A for $1200!
The Alpha did not need a rebuild to remain useful and still produces 1500 watts output from the original pair of finals.
Unless the SB-220 rebuild included a significant upgrade it will probably need another rebuild after the present one wears off.
Then, even if the SB-220 rebuild did include upgrading, the amp is still an SB-220.
Remember the volkswagen beetles with the Rolls Royce hoods pretending to be something they could not live up to?
A search of the marketplace discloses that a working SB-220 is worth about $700. That is based on sales and what an educated buyer is willing to pay. That price is actually about twice what the SB-220 kit was selling for originally. That is also about half of what mister rebuild was asking.
So, is the SB-220 undesirable? No, for the person who only has $700, the SB-220 is very desirable. However, If you are considering the purchase of a $1300 SB-220, you would be much better off buying a used Alpha.
Ham Radio Classifieds
The ham radio classifieds is where you go to buy used and abused radio equipment that is no longer wanted by its owners.
It is a good place for new comers to ham radio to find out what not to buy. Of course not everything listed is junk, just 90 percent of the stuff being offered.
The intent of the classifieds is to buy on-line. You are invited to send serious money to someone you don’t know and will probably never meet for equipment you have not seen or inspected. The opportunity for fraud is a serious problem and draws many a would be crook. A person intent on larceny does not need to engage in a burglary, he merely has the victim send him the item at the victims expense.
Sponsers of the classifieds service try to convince users that all participants have ham radio call letters and are familiar with the super secret two digit code hams use to mean ‘best regards’. Why some of those claiming call signs may even have radio licenses issued by the government. All that is supposed to make the participants honest without exception.
Recent efforts to verify the licensed status of participants suggested including the persons QSL card in the picture taken of the equipment being offered.
I suppose a license from the FCC innoculates holders from any tendancy to commit larceny.
Shortly after the QSL card suggestion we saw a lot of 3 by 5 cards with hand written call letters. I guess it was not possible to take a picture of the license itself or even find a real QSL card.
It is no wonder why sellers consider prospectve buyers to be dumber than mud fences. How dumb is it to send big bucks to someone you don’t know for something you have not seen?
Applying a little more logic we find there is no reason to believe that the picture portrays the actual equipment being offered. Even if the picture was of the equipment offered, the picture cannot verify that the equipment works. Scare word phrases like ‘It worked the last time I used it’ merely raise more questions about the item. Why that is almost an admission that the thing is dead. Why else would the seller not want to test it now?
In any case, regardless of what is right or wrong with the item, it is no longer wanted by the seller. That indicates it may not be wanted by anyone except the person considering the ad. If that is you, are you willing to spend serious money to find out what is wrong with the item or the seller?
How critical is the physical configuration of a Moxon rectangle? How rectangular does it have to be?
I can’t give actual tolerances or even measurable before and after results but I can relate a recent experience that suggests minor deviations from true rectangular geometry are allowed.
I built a wire Moxon for 40 meters according to the formula and supported it on two trees, the chimney mount and one eave of the house. The height at the trees was about 30 feet, The chimney at 20 feet, and the eave at 15 feet. The orientation was SE to NW with the antenna favoring NE and SW directions. The parasitic element was rigged with a relay system that could make it a reflector or director.
It seemed to work. On several occasions signals were effected up to 15 db on the S-Meter by flipping from reflector to director.
It was less than perfect. One end was too low and I suspected I had lots of feedline radiation when running high power. High power operation caused interference with computers, radios, tvs, and dvd players. Most of these problems were solved by adding an rf choke to the antenna feedpoint but I also wanted to raise the Moxon to at least 30 feet. I could do that if I suspended it from the trees and two towers. Trouble was that the distance between the main mast and the closest tree was only 42 feet. The stock moxon rectangle needed 50.5 feet.
My first attempt at getting to 42 feet was to take it out of the middle, at the feedline, by dropping the feedpoint down by 4 feet. I ended up making sort of a modified delta feed with the top of the delta measuring about two feet. The two foot distance was maintained with two feet of parachute cord and PVC insulators.
This allowed the long section of the rectangle to fit into the 42 feet available but it also raised the resonant frequency by 300 khz. I tried winding the 4 foot wire drops at the feedpoint into coils to lower the frequency. For reasons I still do not understand, that did not work. The resonant frequency remained 300 khz too high.
After sleeping on it, the next day I decided to take the 8 feet out of the long dimension by moving the support points 4 feet closer in to the feedpoint. I did the same for the parasitic element. After this wire antenna was raised to the 30 foot level, the resonant frequency came back down and the antenna exhibited a broad band characteristic. The 1:1 SWR points were measured to be from 7.140 to 7.340. the SWR at 7.000 was only 1.5:1. A little tweaking would get the 1:1 SWR points into the middle of the band but this was close enough to be useful.
Initial testing verified that the wire beam still exhibited some directional characteristics. Appears that it has a 20 db front to back. It is now oriented to beam east or west. Its physical dimension is now 42 by 25 feet. The original configuration had it 50 by 17 feet. This 8 foot change in dimensions did not appear to have a significant effect on performance. Note that the total lengths of the wires were not changed. They were merely re-distributed to change the long dimension from 50 feet to 42 feet.
SWR and Power Meter Accuracy
Is a high degree of accuracy necessary when measuring SWR and power? It depends on what you intend to do with the measurement.
Most of us just need to adjust our antennas for minimum SWR. As long as that minimum can be determined to be less than 1.5:1 we have met our goal. It does not matter if that value is 1:1 or 1.2:1.
Likewise, most of us just tune our amps for maximum output. Knowing the exact value of that output does not make the amp work any better. A relative indication of power out is more than adequate for most uses.