The AM Forum

OK, call me an appliance operator, but after weeks of internal debate, I finally pulled the trigger on a new AL 80B. (Hey, it's modern, but at least it has a tube in it.)  Hope to have it on this weekend, and you guys may actually be able to hear me on 75.   ;D

Since this is my first amp, I am pretty clueless.  Any tips for operating this puppy, particularly on AM?  I know it would work better on 220V, but that's not gonna happen soon.

John,

Tune up the amp as usual for max smoke.  Then, use the power output control on your rig to adjust output down to no more than 200 watts carrier.  Advance the ALC control full clockwise when running AM (so no ALC action can take place).

Adjust your audio level so the wattmeter just barely deflects up on voice peaks.

Good luck!

Tony

Good tune up notes.

What are you running now?  You might get 200 watts of reasonably distortion free 100% duty cycle AM from the Ameritron, since it's rated at 1000 PEP output.
The instantaneous RF bias feature, of course, for "70% efficiency" won't be available on AM.

Single 3-500 Z amp. looks nice. Ameritron makes two levels of amplifiers, in sturdiness, coil stock guage, fit and finish, etc. I looked over both lines with the covers off at Timmonium last year and noted the two different standard lines.  

Found it with a parts list.
http://www.ameritron.com/Product.php?productid=AL-80B (http://www.ameritron.com/Product.php?productid=AL-80B)

I have a Pro II running about 30W.

Oh. - Then that'll make a good difference.
And the pro II has lots of audio shaping to play with. You'll have a very nice sounding signal from the 3-500.  8) 
Hope to see ya on the air.

Thanks for the tune-up tips Tony.

Sometimes it helps to increase the loading on the linear just a little bit as a last step, remember your peaks are going to be 4X your carrier power so the loading needs to be adequate to pass the peaks. Ideally, you'd tune the linear up at 4X your expected AM carrier power, then back off the drive to 1/4 of that output level without touching the loading.

If you have access to a scope, it would be a great help.

I guess you have committed to the AL80B. Ameritron makes nice strong amps.
You Shudda bought an AL82. Has two 3-500Z's and legal limit AM.
But I  can understand the financial part, as the AL82 is $2700?
200 watts carrier makes a good transmitter even on 160M. On top band, though the antenna starts to be the main focus.

Fred

Guess you probably saw this excerpt from the manual......


"The efficiency of any conventional linear amplifier must remain below half the peak efficiency
under maximum signal conditions (less a safety factor) in AM operation. Since this linear amplifier
has a peak plate efficiency of nearly 65%, the carrier efficiency must be kept below 30% to maintain
linearity. The power dissipated in the tube anodes will be more than twice the carrier output power.
The carrier power must be kept below 200 watts for clean and safe AM operation. With 200 watts of
carrier, the peak envelope power will reach 800 watts with 100% symmetrical modulation. The
modulated AM power output should be limited to 1000 watts peak with non-symmetrical
modulation that enhances the positive peaks."

Yeah, normally the price delta would not be as big a deal, but with the economy the way it is, and my plant (and salary) cut back to a 4 day work week, I have to be careful right now.  I would definitely consider the AL82 if/when we are safely out of the woods.

Actually, no.  Thanks for pointing it out.

John,

Your new amp will definitely help your signal under marginal conditions and my only addition to the good advice you have gotten so far is definitely let the amp run for a few minutes after your last transmission to cool things down a bit.  The 3-500Z is a pretty robust tube but you don't want to kill the power immediately after a long transmission, give the fan time to cool the tube seals a bit.

To add more tubes to your station you might think about picking up a member of the Drake 4 line (T-4X transmitter family or one of the TR-3 or 4 series transceivers).  These run controlled carrier on AM (the carrier level tracks the voice amplitude on average so the average carrier output is fairly low).  Controlled carrier AM is very friendly to modern linear amps.  You could get some complaints from folks who don't like seeing their S meter twitch on AM but if their AGC is up to snuff controlled carrier sounds OK.  There are, of course, a number of other transmitters running controlled carrier including a number of the vintage Heath lower power rigs.  Just trying to up your tube count a bit  ;)

Rodger WQ9E

Good advice Roger on the cool down. 

I also have an FT101ZD MKII with tube finals to up the tube count, but I need to swap the FM and AM boards to get it on AM. 

I have never heard control carrier AM mentioned in a posive light before.  I started out on voice in 1975 with a DX60.  I guess it reduces the average dissapation while increasing the power on peaks?  In the attic, I have a DX60B in unknown working condition.  I have a Drake 2NT with an Eico VFO.  I think the VFO is the proper frequency to drive the DX60. 

Hi John,

Congrats on the new amp.  A single 3-500Z is a good, clean tube to use for linear service.

As far as tuning it up, for the cleanest signal, you want to load it slightly heavier than when at a "tuned for maximum output" setting.

Here's how:
Look inside and figure out which direction to rotate the loading capacitor to decrease its value. (Less capacitance - plates less meshed)
Then tune both the tuning cap and loading cap for maximum output. Then decrease the loading cap a little bit until power output goes down maybe 5-10%. Then re-peak the tuning cap for maximum.

This procedure will place the tube's operating range more into the straight (linear) part of its transfer curve and produce the cleanest signal possible for the amplifier.

As a result, your efficiency will decrease slightly and you will draw more plate current for a given power output, but the amp will have side products that are down lower than the average ham amp on the band. Keep an eye on the tube plates to be sure you're staying within heat ratings. A 3-500Z should show some dull red color, but not real bright red or yellow or white... :-)  Hopefully they use a chimney with air coming from the bottom to the top. If they use a fan blowing air across, modify it in a hurry.

When you go from 30W carrier to 200W carrier, there also comes a responsibility to your ham neighbors on the band. At 30W you can run most anything and not bother anyone.

BTW, pssst - whisper -  it's not too late to cancel the order - I'll show ya how to homebrew four 813's in parallel GG (linear) and get out 2KW pep, cheap!  caw mawn.  :-)


Later -

Tom, K1JJ

I had another thought that might become an issue in the tunning department.
It is my understanding that you need enough driver power to drive the linear to max output, then you tune your Plate and Loading accordingly.
You mentioned that you have a Pro II, 30 watts.

Fred

The Pro II puts out 30W of AM.  For tuning purposes I can put out 100W of CW.

Do you have the plans for such a beast?  ;D

Good choice on the amp! I use an AL-80B with my Pro III and it produces an easy 125 - 150 watts of AM. It's capable of providing about 200 watts of AM output, but I have found the Pro III sounds best on AM at somewhere between 10 - 15 watts. Definitely go with 220 volt primary voltage if you have it available. The amp works fine with 120 vac, but I found the plate voltage tends to sag when wired for 120 vac, even with a dedicated 20 amp circuit.

There's reams of information about tuning the AL-80B, but you will find it is extremely easy to tune and very forgiving. I always do it in three steps, starting with about 25 watts of drive in cw mode, and then about 40 watts, and then roughly 75 - 80 watts which produces maximum output with grid current under 100 ma and plate current between 400 - 450 ma. The last thing you do is advance the loading control slightly to the right, enough to drop grid current and power output slightly. Then you simply run your Pro II with about 10 - 15 watts of AM and you have a nice medium power station!

If you did not opt for the grid protection circuit, consider getting it. It's very slick, easy to install, much cheaper than a new tube (40 bucks), and simply drops the amp to standby if your grid current moves towards a dangerous level. With the grid protection circuit, you can safely avoid the whole crappy ALC connection inconvenience.

The one thing many AL-80B owners hate is the stupid dynamic bias, which puts the tube at cut-off between syllables and cw notes. It's a distortion circuit and easily defeated with a single 1/4 watt resistor should you wish to eliminate it. I did, and it no longer sounds gritty on the leading edge of syllables.

You'll love the amp, it's very dependable! Mine is vintage 1999 and still cruising along just fine.

Rob W1AEX

I think TOM has plans for tubes with handles on them too.
813's are very nice tubes!!!!!

Fred

I think Rob nailed it on the power issue, running at the 125 to 150 watt level your amp should be well within its capabilities and live a long and happy life.  As noted by a previous poster, a lot of heat is generated running full AM through the amp and the typical power supply and cooling design is biased towards providing the capability for rated power on SSB and CW while allowing for a competitive price and corporate profit.  I use my Drake L-7 a fair amount on AM because my Desk KW and Viking 500 don't cover 160, I drive it with a TR7A which is full carrier unlike the earlier Drake tube type gear and set it at the 200 watt carrier output level.  The only linear amp I own that I feel safe running at the legal limit on AM is one I built for contest duty several years ago and it uses 3 4CX800 tubes in parallel with a Dahl 4 kW CCS rated transformer in the power supply; the output network is similarly over-sized.

I have contacted a number of stations running controlled carrier AM and although it doesn't sound as good as a well adjusted traditional full carrier system it does work just fine.  With controlled carrier you can generally run the amp at or very close to its SSB ratings.  Under marginal conditions this can be the difference between making or not making the contact.  Like others, when conditions are good fairly wide band high level AM sounds great but under poor conditions I would much prefer a copyable controlled carrier or audio with some speech clipping as opposed to trying to pull a really weak signal out of the mud.  I do enjoy DXing and I participate in some contests but for AM operations armchair copy is my strong preference no matter how the signal needs to be generated on the other end to accomplish this outcome.  I know that many others do feel differently about the issue of audio quality.

best vintage TX linear driver ever: Johnson Viking Challenger. 100 W CW, 15 W AM, screen modulated, super easy to restore
and cheap for vintage gear. 80 - 6 meter coverage. just change the filters and do some mike amp work and you are done. 100X better than any controlled carrier rig. Whips a DX-60 like a bad doggie.

Instead of an 813 leenyar, you could always go this route...

http://www.amwindow.org/tech/htm/813/813.htm

Another one of Tom's great designs.

John,

I don't have any plans, but you could use just about any GG amplifier as a guide.

The four 813's in parallel would all have lantern chimneys with plenty of forced air. This would bring the dissipation up to at least 250W each. Use fat aluminum plate caps.

Use 4KV on the plates.  They will show unwanted color, but good for 2kw pep out on ssb. I have a friend who did it. The tubes would be a little over their plate dis ratings, but they would probably do OK if ya talk fast... :-)

The 813 filaments are way oversized and can develop the emission required.

I know someone who planned on using 12 in parallel WITHOUT air, as a quiet linear. He accumulated all the tubes and sockets, but never built it. Now THAT would be a very FB, quiet amplifier.


Good luck with the new 3-500Z amp.

Yes, Tony, that 813 AM rig wud be a great starter kit for John - good idea.  John, use the 3-500Z amp and slowly accumulate the parts for the 813 Am rig!

T

12 813's in parallel would be an interesting setup; I imagine it would be a little problematic on the higher frequencies with so much output capacitance from the tubes.  As I recall WRL/Galaxy had a 10 or 12 tube 6HF5 amp to match their Mark III or V transceiver and it ran at pretty low plate voltage with the plate current measured in amps resulting in a very low output impedance.   With plate impedance that low you could seriously consider using broadband output transformers similar to those used in modern SS gear.

I started digging out the stuff tonight to build a version of the K1JJ 813 design.  I have a nice Gates roller inductor and a vacuum variable that will soon be living in the output network.  I finally found a mod reactor to go with a WWII era Westinghouse mod transformer I picked up a few years ago.  My plan is to set it up for 160-40 meter operation, 160 in particular.  I have pretty much all of the parts and some chassis from another ham's start at an 813 rig.  My New Year's resolution was to turn more parts into rigs so this is my attempt to keep it.

Rodger WQ9E

BTW, the name is John  ;D

Don't worry John. Al is going to build that 813 rig for you.   ;D

I am familiar with that schematic, but I heard there are some errors in it. ;D

My brain is turning to silicon, John... :-)


Errors on the schematic? Don't worry ~  I hear they hired some guy named Al to fix it up.

T

I'm not sure where the AL-80B dumps its heat, but if you can increase the heat removal, especially past the tube pin and anode seals, it will be alot happier on AM in continuous duty.

Most older amps just fire the hot stuff out the top, and a 10" 220V 'muffin' or "Tarzan" fan sitting up there on little rubber feet is good for them. The 220V makes it quiet on 120V, yet the 10" size moves alot of air out of your expensive amplifier. That's a real nice amp, a good brand for a modern amp and uses a cheap tube to boot.

Sometimes I listen to AM on my rotten little 40FT wire antenna while I am working in the lab. Maybe I will hear you now!

Well I popped the cover (all 21 screws) and installed the tube.  Looks like I may already have a problem.  The plate supply (no load) is only 2600 instead of the 3100 it's supposed to be.  Line is 120.2.  The transformer is factory set for 125.

Might be bad filter caps but it could also be the metering resistors are out of spec.

It may well be that lower indicated plate voltage is just a result of running on 120 vac instead of 240 and that you are 5 v below the tap setting of 125. Is there a tap for 117 or 120v?

I thought about that, but assuming a linear relationship between input and output voltage, being 5V low on the input (96%) should correspond to 2796.  2600 should correspond to a 104V input.   I have taps for 90, 100, 110, 115, 125 130 & 140.

I can only get about 600 -700 W out, but part of that could be the line dropping to about 105.  The Vplate fully loaded is supposed to be 2700V.

The line voltage drop of 15 volts (120 - 105) is about 12.5 percent.  If a lower tap (117 or 120) is selected, the line voltage will sag even more, due to larger current draw under load.   Considering this voltage drop, I would assume you may be using a regular 15 amp circuit wired with #14 conductors for the amplifier.   If this is the case, I would recommend either a dedicated 20 amp 120 volt circuit using #12 conductors, (upsize to #10 if it is a rather long run to the panel) or better yet a 20 amp 240 volt circuit, again using # 12 conductors, in this  case no upsize is needed even if it is a rather long run from the panel.

Also it is not clear whether your voltage readings are from the internal meter, or an external calibrated meter.  If you are only using the internal meter, it may not be accurately calibrated, or the multiplier might be high in value.  If you do not have a variac, one way to more safely determine meter calibration is to connect the rig to a 120 volt source, but wire the rig for 240 or 250 volt input.  Then the high voltage meter will read half the expected value, and can be measured with an external calibrated meter in the 1500 volt range.  Still follow all safety precautions, and do not try to load it up with low filament voltage, or better yet, remove the tube when performing the voltage tests.  If you cannot confirm the accuracy of the internal meter, all we know at this point is that you need a source that can handle the current requirements, and there may not be any problem with the actual equipment.

John
It's a lot more work, but it's worth it. It already looks like your 115VAC is sagging under the load of the amplifier. You should switch to 220VAC.
And the fan, if it's like the Heathkit SB1000 is nothing but a little muffin fan for a microwave oven. That 3-500Z will get very hot in there!!

I have an AL811 made by Ameritron and switching that amp to 220vac DID NOT make any difference in output power. As the manufacturer stated.
But your amp is making 1KW out and you're gonna need more A.C. volts.

200 watts for an A.M. carrier is very rescpectable.

Fred

Hi Rodger,

Sorry I missed your post the other day.

Yes, that Galaxy amp was something else. I have a friend who actually built a duplicate of it in high school physics class... :-)

The (12) tube 813 linear amp was meant to be used mainly on 160 and 75M, so the plate capacitance wouldn't be an issue. The great thing about that design is silence. For ssb, blower noise is such a pain if you want to run some processing.

Good on the JJ 813 rig you want to build. Sounds like you have a good start with the parts. There's probably at least a dozen rigs out there now in various forms. I like it as a middle of the road rig. I'll tell ya though, one day I'd like to do a quad 813's by quad 813's. Use a 1:1 mod xfmr.  With 3KV on it, it wud be silent and deadly. Or, add the Deitz? lantern chimneys for cooling, with a slight breeze -like mine pictured below. (One 813 final modulated by a pair)

BTW, I built up a great audio driver for the 813 modulators designed by Tom, WA3KLR. It uses about 5 watts TOTAL power and its FET's drive the cathodes of the 813's. Very clean and efficient. The schematic is available if you are interested. Mine is in the little silver box on top of the 813 rig in the pic below.  You need about +50V on the 813 grids to make it work right.

Keep us informed on your new 813 project, Rodger!

John: Your amp.... I doubt it has a problem this early on. It's probably just a matter of getting a stiff AC mains. Though, many pairs of 3-500Z's barely put out 1300W with 2700 V. Maybe a pair will do 1500W pep out with 3KV, so 750W pep out using one is not bad.  So, at your present 600W, an extra 150W is obtainable.  750 pep/4 = 187W carrier, so 150W of carrier might be about right unless you can squeeze more pep out.

I would get in there with a VOM and measure what's coming in at the primary and see how much it sags at full power output.  Definately consider going with 240V. This is something that you need for rigs now and in the future now that you're playing the QRO game... :-)


73,

Tom, K1JJ

Here's the WA3KLR  FET solid state driver. Quite innovative, really.  I use it to drive my 813's modulators. It drives the cathodes and requires about 5W of power. Very efficient. You also need about +50 volts on the 813 grids to get the positive peaks.  One volt in is all it takes.

The schematic is the FIRST file below called, " 833dvr7build.pdf "

Tom, K1JJ

While we're at it...

Some "before" shots...

T

Shots of old, never seen before.... :-)


The quad 4X1's are the two finals and two pdm modulators.  Parts all lined up like toy soldiers ready for service.


T

I am not to concerned with the power sag.  I expected it, particularly when I have the amp plugged into a power strip plugged into an outlet feeding about 5 other power strips (a few computers and other stuff).  :o  What does concern me is the low no-load voltage.  The sag issue is irrelevant at no load.  I find it hard to believe the unit would ship with the meter so far out of calibration, but it is possible.  I think I have a HV probe around here somewhere.  If not, I can probably bring home a calibrated HV divider from work. (I work for a HV power supply company, but our stuff is PWM regulated to 0.005%. ;) )

With that much equipment on a single receptacle, I suspect the wiring and the breaker might get just a bit warm.  Much more important, I would expect any "Old Buzzard" AM transmission to be prematurely extinguished, along with the unsaved computer data. 

I would certainly use a dedicated circuit for any 3-500Z linyear, and if a circuit needs to be added, it would be 240 volts.  Just my two pesos. 

Yeah I know, but I need a 3ft heavy duty extension cord to reach a different outlet for now, and then I can think about running 220V in the future.  Since I am only running about 150W AM to limit the dissipation and maintain linearity, the input power should be fairly modest anyway.

John,

Just a couple of thoughts regarding the AL-80B. Whenever I move mine on the bench, I have to check the pivots on both cross needle meters. They are sloppy and have a tendency to bind a bit, restricting movement and affecting accuracy. Usually, a little wiggle of the front panel pivot adjustments will free them up. With my unit, the grid current pivot is the one that requires the most attention. This is not an unusual annoyance for any of the Ameritron amps using these meters.

When I first fired up my AL-80B it was wired for 120 vac. The plate voltage initially was sitting at around 2700 vdc with no load and sagged to around 2400 vdc when loaded. It was quite a trick to get much more than 625 watts CW output on any band. I did move the primary tap on the transformer to get it to rest at slightly above 2900, but I still experienced more than 300 volts of sag under load. The maximum output when set up that way was a bit less than 700 watts with CW. The lamps in the room dimmed impressively whenever the amp drew current.

After I ran a dedicated 30 amp 240 vac line up to the station room, the amp performed much better. At idle it typically sits at slightly more than 3000 vdc and under full load will drop to slightly more than 2800. No problem reaching the full rating of 800 watts out with roughly 85 watts of drive (CW) at those voltages. The meter swings to 1000 watts PEP output without any strain. For what it's worth, the PEP meter on the Palstar tuner concurs with that power measurement.

I don't think what you are seeing is at all unusual. If you plan to run the AL-80B on 120 vac for the time being, it might be worth it to move your primary tap to attain a higher plate voltage, closer to 2900 at no load would be good, to allow you to reach higher power at less current.

Incidentally, the internal fan does an excellent job of moving air through the amplifier. I'm not aware of anyone having any heat-related issues with the AL-80B or the 3-500 final as long as there is clearance around the amp for unrestricted air flow. The amp has a decent power supply and in fact the AL-80B is rated for 500 watts output RTTY (1/2 hour continuous carrier duty). Mine has not complained during AM sessions at 125 - 150 watts output, even when I babble longer than anyone cares to listen. I have run it at 200 watts output at times, and it doesn't even flinch then.

Rob W1AEX

Thank you so much for clearing this up Rob.

On the one hand, this is excellent news because it means the conditions I am seeing are normal.  On the other hand, I am ticked at Ameritron for not putting this information in the manual.  Seems kind of strange they would intentionally get the turns ratio wrong at 125V, but the least they could do is "fess up", particularly when it appears the unit will not make full power as advertised at a typical 120V input line on the 125V tap as shipped.

I was going to get a Variac and take some measurements at reduced voltage, but then I realized that I can't make any sense of the schematic they provide.  They show one stage of the HVDC filter cap circuit completely shorted out.  I can't believe it's actually wired this way.  Has anyone ever done a mark-up of this schematic to make it intelligible?

OK John
on a temporary hook-up on 115vac, but the P.E.P. might get flat-topped because the H.V. supply is starved for some moe juice.

I was already for 220 operation on my AL811 and the manufacturer said it would be a waste of time...............and it was, as I stated earlier. 3-500Z's need a lot more current than the lowly 811's.

fred

As was done here at ZedLR radio I finally after all these years ran a separate 100 amp service to the Xmitter site...and we'll be putting in a 2x1 813 machine in as well...collecting parts now... :)

Check your existing 120V wiring: if any of your outlets have a separate 120 volts feed, it's very easy to reuse the same wire for 220v. This assumes that it's modern wire, such as 12-2 "with ground", but you do not need a separate neutral for a 220V outlet at that current level.

The code requires that the wire be marked at both ends and at any splice points, but that's all: if you have a separate piece of wire already in place, then a double-ganged breaker and a 220V outlet will put you in business.

HTH.

73,

Bill W1AC

Don't know about your wiring but usually in a bedroom or utility room there is only one feed of #12 wire for everything.  At most that gives you 15 amps of current for everything in the room.  Given your description of where your amp is gettling AC, it is understandable.

In the kitchen you might see two separate circuits and, again, I don't know about your house.  If it was built many years back it may be wiring challenged, which would explain a lot of sag.

If you have a couple of extra slots in your electrical panel, run a 20 amp 220 V circuit to a dedicated plug and convert the amp to 220.  It, and you, will be much happier and cooler.

The old section of my house includes the den/computer room/ham shack.  And yes, the entire den is on one 15A breaker.  This section was completely gutted and re-done about 15 years ago when we added a "house" onto our existing "addition", so all the wiring is reletively new. I have a separate 100A sub-panel for this section, so I need to investigate if it is wired for 220V. Unfortunately, all the breaker slots are are filled with 1/2 size breakers.  I have one 20A circuit that is only being used for the basement outlet/dehumidifier and a tiny sump pump.  I might be able to free that up and move the sump pump & dehumidifier over to the dedicated 20A circuit for the washer.

Another option is to run a wire all the way back to the main panel, which unfortunately, has no empty slots.  I think I can change some breakers to 1/2 size to free up some space for a new 220V breaker.  As near as I can tell, the only 220V circuit in the entire house is for the septic pump, as we mostly use oil or propane and have no major appliances which require 220V electric.

BTW, when running 150W of AM, the sag on the line is currently only 2V.

While you are at it, why not check to make sure you have 5V at the filament, so it is neither high nor low.

I really don't think you need to do any troubleshooting or testing on the PS. The 125V tap and your 120V line voltage along with perhaps a slightly out of spec multiplier resistor are probably the reason for your lower than expected indicated plate voltage. I did take a look at the schematic that is in the on-line manual from Ameritron. That manual was dated 1995 and I would think that they would have fixed that error by now as they do show C124 shorted out.

I just got the recap kit for the DX60B.  I also got a manual for it.  The guy I got the manual from does nice repro work at about 1/2 the price I have seen elsewhere.  Comb binding with heavy sheet protector plastic covers over heavy paper covers. I don't want to mention his call due to the recent Heath copyright issues.  I don't want to see him shut down.  PM me if you need a Heath manual and are interested.

 :) Wonderful, so this means I will hear you on the DX-60 net soon with your DX-60B, right ?

I don't know about "soon".  I have no idea what might need fixin'.  This is not my original DX60. 

I don't even remember how I got this.  I think I traded something for it.  ???  I also need a Dowkey relay to switch the antenna. (There is one on eBay for $233 - they are out of their minds!!)

You only need a Dow Key relay for bragging rights at the DX-60 power level, a regular DPDT relay with 120 volt coil available from numerous places for less than $10 including Radio Shack will  work just fine.  I use this type of relay for T/R switching on most of my low and medium power vintage gear and move up to vacuum relays for the legal limit stuff.  I have a couple of pieces of gear using Dow Key relays because it came with them but I would not go out of my way to find one, especially at collector pricing.

You can mount the relay in a small project box and use that to mount connectors for coax hookup or at the DX-60 level you can use RG-58 which is small and flexible enough to easily solder directly to the relay contacts with appropriate coax connectors on the other end.  I imagine many DX-60 stations originally sported manual T/R switching for that classic novice "high involvement" feel.

Rodger WQ9E