The AM Forum

Forgive me as I posted this in the transmitter section which doesn't seem to get much traffic, so I'll post it here.  I have a Johnson Courier (matches Ranger1) which I'd love to put on 160M.  Has anyone done this?  If so, how did you do it and does it screw up the other bands?  73, Mike WB0SND

The "Transmitter Section" part of the online handbook, and is intended for completed articles, not general questions.

Unfortunately I can't help you with your main question, but I would suppose that you would have to re-do the output inductor, need larger capacitors for the tune and load, and possibly install a plate choke with more inductance.

If you do get this project completed, by all means write it up and post it in the Transmitters section.

The Courier was a short run amplifier that seems to prized by many collectors. It might be easier either to sell the Courier and put the money toward a new amp that covers 160M or build a single band 160 M amplifier. You might want to review the QST article, "Putting the SB-200 on 160 Meters", Nov. 1987, page 33, that should provide insight into the modification/design strategy of converting an amp to 160M.  Although the Courier comes stock with 811's, 572B's drop right in. The SB-200 uses a pair of 572B's so both amplifiers share similar designs.

Pete's probably right.

You might try making the tank a Pi-L only on 160. The existing C2 will be the weak link due to increased voltage at the image impedance.

Beef up the output R.F. connector to something with Teflon and the whole deal could be in a small box.

The Tron had luck with this idea on one of his AMplifires.

Sell the Courier on ebay and use the money to get a better amp. Couriers are bringing big money right now.

Navigators are bringing in huge coin. saw one go for 700 and change not long ago.

You also have to screw around with the Courier's tuned input circuitry. And, this baby also uses one of those infamous fused plugs.

I own a Courier and I love it.  If you're short of coin -- do the ham community a favor and sell it and get something that covers 160.  If you are using the low power required feature due to the grid input of the Courier that's another story. But it will take some special engineering -- I see the problems as follows:

• Tuned input will have to be changed - that's a design issue
• Neutralizing requirement will take special consideration -- after all the mods that gets put in for 160 M operation that still has to work
• Outpoot tank will have to be redesigned - consider previous comments about existing components not having enuf poop to do the job

Good luck but if you think you are a little uncomfortable with the task be sure to befriend a ham who is

Gl es 73, Al

Hey, thanks guys.  Well, not sure what to do.  The Courier is a cool looking amp for sure which matches the Ranger I but probably doesn't meet my needs totally.  I'm comfortable making very mild mods, but it appears this is too much for me.  I'll probably just use it on the other bands....or sell it. 

I actually have an amp I'm going to try that may be kind of a perfect match for the Ranger, however, it's pretty modern.  It's a Emtron model DX-1B made in Australia.  It's a single 4CX800 which takes about 40 to 60 watts to drive to full power which may be a good fit.  I don't own it yet, but if it works with the Ranger I might buy it if the price is right.  I'm a little uncomfortable with the company as it was very difficult to get them to email a manual or help troubleshoot a bad T/R relay.  If somthing else goes wrong, I may very well be screwed!  Anyone out there got a desk KW they want to sell? (I know they can be modified for 160). 

As soon as I get finished with the Ranger, I'll let you all know how it worked out.  I'm doing a minor rebuild on it right now.  I'm not going to put in a lot of mods at this point..at least yet.

Thanks for all of your responses.  I'm glad I found this site.

73,  Mike

You will need to build or buy an attenuator to use with the Emtron amp.  The rating is 60 watts SSB peak power input. The Ranger produces 50 to 60 watts of carrier power.  Anywhere from 130 to 160 watts PEP.  It will hurt the Emtron the first time you key it.  The emtron wants about 10 to 15 watts of carrier intput.  Do yourself a favor and just dont get the Emtron and if you do, use it for what it was meant for, an SSB amp.


C

Well I already have the Emtron amp, (sort of....I haven't paid for it yet) so I thought I'd give it a try.  Wouldn't installing the power output control mod which varies the screen voltage reduce the output to the level the amp wants to see for AM operation?  Reducing the loading on the Ranger gets the power down to where the Emtron doesn't kick out due to overdrive and it puts out full power (CW) although I am not going to run it this way.  BTW anyone have any recommendations about where to get the 4 watt pot needed for the screen control? 

Yes. You can do the adjustable screen mod.  That is helpfull. I have that on a valiant and it works nicely.  The trouble with lowering the load on the ranger is that you throw off the match of the Mod transformer. This can creat high voltages at the mod trans and blow it out. You really want to load it up to what Johnson suggests. Then you can fine tune it from there using an O scope.  But even then, I am telling you that the Ranger just wont want to be much lower then 40 to 50 watts carrier.  That is just way to much for the emtron.   

Look up Johnson Power reducers.  They where made by johnson to do what you want to do. You just hook it up inline and it reduces the power to the amp.  There are designs all over the web and you can even just copy the johnson design. Look up the manual for the johnson Tbolt amplifier. In that manual it tells you how to build the Reducer for use with other higher power radios. The Tbolt had two 4-250 or 4-400s and needed only about 15 watts of Drive.

The Emtron is a great amp. It just wont like that peak power the ranger produces.  With some work, You can make both the amp and the radio happy.

Good luck!

C

You can also run the Ranger final on the low voltage supply. Quick way is to use jumpers in the 9 pin socket on the back. However, that way makes the plate current meter inoperable.

Oh, I know that running any transmitter like this with less than full loading causes problems.  That's why I said I don't plan on running it that way.  Years ago I bought a Thunderbolt which I have since sold, but it came with a homemade attenuator.  I have it somewhere (challange is to find it).  So, I will use that for sure.

Running the final on the LV supply is an interesting option, but I'd prefer the variable screen mod and attenuator since both are easily changable and variable.

Another thing, does anyone have a copy (or original) of the Courier manual they want to sell.  Bama just has a brochure for it.  I'm cleaning and re-capping the Courier right now.  Thanks again for everyone's input.  73, Mike WB0SND

I just don't get why folks resist the low power mod for the Ranger. Change one wire on the accessory plug and you have instant low power without screwing up modulation transformer OR plate load impedance. The modulation also improves due to the extra dynamic headroom. If one can't live with the plate current meter not working install an ammeter in series with the connection OR use a relay to switch from high to low power. Load up in high power and flip the switch. Retuning isn't necessary. It's a class C final and should work proportionately. One can also rewire the meter so it works no matter what. It's a little brain work but can be done.

Lowering with screen voltage will change the load on the modulation transformer in the wrong direction especially in Valiants, DX-100s and other rigs with a high mod xfmr ratio. 

I think probably that people, including myself, would not like losing the meter functionality.  It's also relatively simple to make an attenuator that you can switch in and out with a 2 pos. coax switch.  If there wasn't a meter issue and you could use a switch to go between low and high power, I'd opt for that mod rather than the attenuator.  I think that the main resistance to low power mod is loss of the meter.  Remember part of the allure of this old stuff is seeing the meters, etc.

I always run my Thunderbolt with the Ranger operating at the lower voltage. It wasn't rocket science to do a minor rewiring to get the plate meter to work. I built the resistor pad years ago but I dislike my RF radiating away as heat in the resistors. At higher frequencies, 15/10 meters, resistive pads can get "squirrely" unless the resistors are non inductive.

Thanks for the explanation.

There are lots of solutions. I think these guys laid it out.  You just need to decide which one to do. Lots of good ideas here.   Hope to work you on AM soon

C

I don't get it.
The courier runs a pair of 811's no?

Wont the power output of the amp on AM be the same or less then a barefoot ranger????


Brett

Bingo! ;D

I run mine at about 70 watts carrier (maybe a stretch at 100 watts) -- ~6dB for peak RF = about the limit for a Courier.  Doesn't sound like much of an increase.  I use mine to alleviate the the demands of AM on my solid state  Flex.  Figgering about a 20 watt safe level bare foot carrier for my Flex that comes out to not even an S unit increase - - but it does help and it does give the Flex a little help -- the carrier out of the Flex  is about 3 to 4 watts as I recall.

Does the xmtr in question put out ~40 to 50 watts?  That's not even 1/2 a S unit

Al

Well, you're right about the AM power level.  I have a confession to make.   :-X  I actually operate mostly CW.  So, the AM power level isn't as much of a concern for me.  However, I will be operating AM some.  I just think this amplifier is so cool as it matches the Ranger (probably the reason it demands so much money).  It really isn't much of an amplifer with only 2 811A's.  Eventually I hope to end up with something that has high level plate modulation like a Desk KW or something homebuilt.  Being a Collins collector, I'd love a KW1 but just can't let go of that much money for one.  I do have a 32V-2 working great on AM at present.

I'm probably going to use the Emtron amp mentioned earlier in this thread (capable of 800 watts carrier).  Or a friend of mine has a homebrew 4X 811A amp which covers 160 that actually be the most promising amp.  I'm gonna look into that one next.  Thanks for all of the guidance, guys. 

It is a cool looking amp.
I figure four 811's will be smoking at 100 watts carrier out, so forget that on AM.
For CW, I don't see the need, 100 watts is plenty in most cases unless you want to win contests or break DX pileups, then you would need 1500 plus a good antenna/beam....

I think if I was wanting an amp for ssb and cw, I would get one of the 1200 watt solid state no tune amps.
The mfj stuff seems ok if you resolder it when it arrives....

Before I built the amplifier, I ran the flex barefoot at 25 watts out with good results (very smug)...

Brett

I have 572B's in my Courier and also solid stated the power supply. The Flex, Icom's 756 PRO II, 7000, Kenwood Twins, Lafayette HA-410(for 10 meter fun)  all drive it fine. Generally hold the RF output to about 100 to 110 watts.

The Courier has plate iron larger than an SB-200.

Probably could get rid of the choke input, solid state and pop in a pair of 572Bs for an easy 125 watts carrier out.

I had two of these and sold them off to very happy buyers.

The temptation was not enough to hack them.  

Pete, Dave

I haven't SS'd the power supply but I did for quite for some time run mine at 100 watts AM carrier but after carefully looking at the envelope on a scope and getting a report of flattopping (thanks Dirk) I decided 70 was a better place to have things.  At no time did I experience any  blush on the plates.

I just cannot bring myself to making those kind of changes (possibly SSing the power supply) but it's close to a 50 year old machine and it just aint worth it to me to even try.  She's a grand old girl and I expect she will outlive me.

Al

Its got mercury vapor rectifiers, no?
Solid stating wont get you anything there....
They do have plug ins, so you dont have to mod anything, but its not going to improve things much.

Brett

As Dave indicated, got rid of the choke, added a string of diodes in the power supply, and added a pair of 572B's. When I got the Courier ($25), one 811 and 866 were missing. The other 811 had a open filament. Since I'm not fond of mercury vapor tubes to start with, I sold the remaining one for $5. Courier has been running this way since the late 80's both on AM and SSB. It rocks on SSB.

Brett. I have the direct SS plugins - made em myself.  Pete - I bet it does rock. What kind of PEP do you get?

I suggested cap input and forget the choke to allow more voltage for the 572Bs and hopefully keep the plate load where it started.

Rectifier requirements go way up with cap input.

Fortunately we have Pete to tell us his numbers.

On SSB, the PEP output was somewhere around 600 or 650 watts, I seem to remember the last time I measured it back around 1989. On AM, I generally adjust the RF exciter feeding the Courier for a Courier RF output of about 100 to 110 watts. Still using the same 572B's I put in back in the 80's.