The AM Forum

If anyone is interested I documented my Johnson Ranger restoration and upgrade over the last two months. The direct link is

http://www.crompton.com/hamradio/JohnsonRanger/RangerRestoration.html

and it is also available as a link off of my hamradio page - www.crompton.com/hamradio

Thanks for the help on my questions over the past few months.

73 Doug

Excellent and extremely well document Doug.  The rig sounded very good yesterday on the air. 

Steve-HX, seems like Doug's article would be a candidate to be put on "The AM Window".

Joe, GMS

Very nice. Thank you for the documentation.

C

That looks great. Really good work and craftsmanship I think. Now for the next project??

Doug:

Excellent job on the restoration as well as the web page!

I enjoyed speaking with you on your maiden voyage with the rig.

73,
Dan
W1DAN

Hello,
How did you figure out the values of resistors for the screen modulation improvement.
I mean the 60 and 40% values?
I would like to do this on my Valiant II.
Thanks,
Don W9BHI

First of all thanks for all the nice replies about my page. I had a few errors in the links that are now corrected. I also added a few more photos.

In answer to Don's question about the screen voltage mixing there is a link on my page that directs you to the AM forum where this was discussed. The link is:

http://amfone.net/Amforum/index.php?topic=32893.0

It was authored by Dean WA1KNX and there is a gif link at the bottom.

I also found that you really need to look at the PA screen voltage and current requirements based on your current plate voltage. The screen resistors used in these rigs in many cases is too low a value. The Ranger used a 30K but my combined screen resistance in the Ranger is about 50K. This is based on a 550-600 volts on the plate. Using the higher values results in less dissipation through the clamp tube on CW or loss of RF to the final.

73 Doug

How do you know what the screen voltage and current should be?
There are three 6146's in the Valiant.
The manual shows about 180 volts on the screens and about 625 volts to the plates.
I never actually measured it.
They are using a 12k 20 watt for the screen dropping resistor in the circuit.
I need a little help figuring this one out.
Thanks,
Don W9BHI

The normal 6146 screen current range is 7-9ma so in your case 625-180=445 @ 24ma (3*8ma) = ~18K. 20 Watts might be a  little light though because when the clamp tube conducts it puts the 18K to ground with 625 on the screen end. That would be 21 watts. I am assuming that rig uses a clamp tube. If it doesn't then you could probably get away with a 10 watt. When you use the mixing circuit you might find you can use a combination of 3-5 watt resistors in series to get the proper resistance. In my case I used two 68K 2 watts in series on the unmodulated side and three 24K 2W in series on the modulated side. yours would differ because you are using three 6146's.

This works out to just about 1/3 of my 50K for one 6146 vs. three.

So in Deans formula I would use 24ma 180 volts for the screen in the 60/40 ratio.

73 Doug

I did the math for your Ranger and the unmodulated resistor (136k) for 40% comes out right but the modulated resistor comes out to 90k.for 60%
Your value is 72k that is about 75%.
What am I missing?
Thanks,
Don

Doug,

Your work looks great!

Chuck

Pulled the Valiant out of it's cabinet and took some readings.
The B+ is 693 volts.
The screen is 175 volts.
The screen current is 41 Ma. for three 6146's
This does calculate out to about a 12K resistor.
That is what is in the unit.
41Ma sounds kinda high doesn't it?
If there should be 24Ma. for three (8Ma. each) then the screen resistor should be closer to 21k which gives 160 volts on the screens.
I also see a 20Ma. downward swing on the plate meter with the 20K screen resistor.
Does this sound correct, what do you think?

Thanks,
Don W9BHI

I guess the short answer is that it is not that critical. My actual values were 122K and 81K - I used 132K and 72K

The screen current I quoted is from the tube table in the back of any handbook.  I think your 180 volts might be high.  The tables show 600 volts plate modulated with 160 volts at 7.8ma on the screen. That is for 6146 or 6146A.  For a 6146B they show 175 volts at 9.5ma

So 693-160=533/.024 = 22K    assuming your plate voltage is 693 under full load.

So you would use the number .0048 for the modulated and .0032 for unmodulated for a single 6146.
.0144 and .0096 for three 6146's

693-170=523/.0144 = 36K  (10W)   523/.0096=54K (6.6W) - so to use smaller resistors you could use 4 - 3W resistors to add up to 36K and 3 - 3W to add up to 54K, Again tis is not super critical. If you are of a few K in direction or the other. Again this is calculating the screen load only for wattage. If your clamp tube takes it down to ground you would want to use more wattage but you could still use small resistors if the wattage's added up.

Attached are 2 pdfs of pages from the E. F. Johnson Amateur Equipment Catalog number 957 (1957 edition I presume).

The first pdf is the inside front cover page that declares "amateur radio is fun" and the second pdf is the 2 pages on the Ranger.  The Ranger kit price was $230 in 1957 which was nothing to sneeze at as $230 is still a significant amount of money.

The catalog pages on the Ranger are nice to have even if you have the manual as the specifications and features are concisely stated.

Doug, you may want to add the catalog pages to your documentation.

Enjoy.

Thanks Tom, I will add those pages.

$230 in 1957 would be $1879 today. A 717% increase.  So there is no money in (most) old amateur equipment, just the joy of having and using it. That would have been like buying a full featured HF transceiver today. But then you would also have had to buy the receiver and other extraneous accessories to go with it. So a modest ham station in 1957 would probably be $3500 in today's dollars.

(http://www.crompton.com/hamradio/JohnsonRanger/RangerPhotos/DSC00567.jpg)

"The rear panel. Left section - Microphone and key jacks, RX mute and amplifier key jacks, and TX and RX antenna jacks. Right section - 8 pin octal (not used), modulator bias, modulator scope out, fuse, and line cord. No case modification are necessary for the new connectors."

It's a 9 pin.

You might also run a spell check and grammar check through the entire document to correct some issues.

I will correct that to 9 pin. I don't use it so it really didn't matter.

Hey if you see something that is not spelled right or phrased right I would be glad to know about it. Send me a note off list - qrz is fine for email.   My spelling check shows no errors but nothing is 100%

I guess my point is that since you spent the time to fully document your Ranger restoration and modification project for the online world to see (probably for many years to come), you would also want it to be grammatically, within reason, accurate. All I did was copy and paste your entire document into Microsoft Word and let it show me questionable spelling and grammar. As an example, in my previous post, your words under the picture include, "No case modification are necessary for the new connectors". Correctly, it should be either "modifications are" or "modification is".  It's all up to you; it's your document; but as I have told others over the years, your written document becomes somewhat a reflection of who you are and how you deal with accuracy and being grammatically correct with your written word.

Oh so I left an "s" out, so sorry the reflection is really going to bother me, NOT. The reflection that I would see is a somewhat more positive one, that 98% of the hams out there would never even be able to accomplish what I did on this rig. It just happens that the other 2% are here.

The nice thing about Web publication is that it is dynamic. If it were printed in a publication it is forever unchangeable. So lets say this page is evolving and will have many changes in the future including adding an "s" here and there!

"No good deed shall go unpunished" (Clare Boothe Luce), with apologies to the Professor for using a double-negative on these august pages.

This is exactly the reason that I don't publish any of my work on this site or any other!  You have people that have nothing better to do than nit pick minor things that have no significance to what you have conveyed.  Also, the better ones work is, the more these people look for other things to criticize.   So take it as a compliment that someone had nothing better to do than cut and paste it into Word and look for grammatical or spelling mistakes! 

Jooooe, oh sorry its Joe-GMS       

   Actually this nit pick might be a good thing considering what used to occur. We seem to have moved past censoring posters using long expired Copyrighted content (the eyebrows of the ARRL twitching), and have moved on to grammar issues. This is progress.  ;)

Good work Doug.

Jim
WD5JKO

Great work Doug and thanks for documenting all of it.

Who cares about those who are overly critical, and whose first impulse is to nit pick. To paraphrase his words..its a reflection of who he is and how he deals with other peoples work apparently. He should get a life.

Al VE3AJM

Actually, it wasn’t my first impulse. The impulse came after I read it. I’ve always believed in the old adage, “if it’s worth doing, it’s worth doing right” and to me, that means both accurate technical (technically it’s great) and grammatical content. But hey, I really don’t care; it’s not my document. Grammatical screw-ups seem to be the norm today in many writings on the internet.  Even here on the forum: “receiver” spelled incorrectly in over 290 posts, running sentences, lack of punctuation, etc. I'm sure it doesn't go unnoticed. It’s your reflection, not mine. Let’s move on.

I did notice that spelling/grammatical error in the previous post. No matter. I'm sure you are a gentleman and a scholar nevertheless.  ;D

Al VE3AJM

"Even here on the forum: “receiver” spell incorrectly in"


Wow poor grammar or spelling? from the nit picker!

The best revenge it to buy a Crown Victoria and enjoy it.

I always appreciate when someone calls to my attention my grammatical or spelling typos. I've corrected it. Thanks for the support of my original point in the thread.

 I prefer Crown Royal over the Crown Vic.


klc

Very interesting article and nice restoration. I just finished working on a very early Ranger. I acquired this one at a local auction for less than a hundred dollar bill. It too was a kit built unit and the wiring was not too bad but I did have to do a bit of clean up work on poor soldering. This unit is before the bias tap was added to the low voltage B+ winding. It did however have the keying mod installed. The voltage for the 6AL5 bias rectifier was taken directly from the low voltage B+ winding. A resistor/divider network consisting of a 150K 2 watt resistor and three 18K 2 watt (paralleled) in each cathode circuit of the 6AL5 was used to drop the voltage to approximately 55 volts. These resistors were mounted on the underside of the keying sub chassis and I believe this may have been provided with the kit as the terminal strips used were the same type used throughout the transmitter. I did add the PTT mod using a 12 vdc relay. A voltage doubler taken from the 6 volt filament supply  was constructed to power the relay coil.  I removed the self bias from the modulators and used a 10K pot to supply adjustable bias. I also replaced the tube rectifiers with solid state, upped the filter capacitors in the HV to two 220 MFD@400 volts in series. That big 20 watt HV bleader resistor was moved above the chassis and attatched to the shield that runs length wise across the chassis. I haven't made any mods to the audio, maybe at a later date. This is the transmitter I coveted when I got my license in 1961, but it was simply way above my price range at the time. SSB was becoming the rage so as soon as I could afford it, the DX-60 was retired and I moved in that direction. Now, all the years later, I finally have the transmitter I always wanted for AM and having much fun chatting with the AMers. The station can be viewed on QRZ.

Bill - K5MIL

Publish you work and bypass the nit pickers, they aren't worth your attention.

Bill

Bill,

  Great on your restoration of your Ranger. It sounds like you did some good things to the old rig. I like your station. It looks like the Ranger has been well taken care of. Your shack looks a lot like my upstairs shack as I have a 32s1/75s1 and HW101 in mine also. My first RX was a Knight Span Master but when I was a novice I had a Knight TX60 and Heath HR10. I have all those old receivers in my mini museum but unfortunately not the originals that I once had.

You mentioned the 6AL5 bias rectifier but you did not say if you changed that to a solid-state device. When you use fixed bias on the modulators it needs to be reliable and the 6AL5 can be a weak point. Not long ago on this forum someone lost a Ranger modulation transformer due to loss of bias. I believe it was blamed on the 6AL5.

You could also get rid of a lot of heat and energy consumption by dumping the big resistor. Replace it with 68K 3W balancing resistors across the series electrolytics on the HV and run the modulator screens directly off the LV supply via the functions switch. The modulator screens should only be turned on in the AM mode. You would need to re-adjust the modulator bias with your pot.  

Thanks for your comments on my restoration. There are many ideas out there on how to do it and hopefully this will give others some more options.

I am picking up another Ranger tomorrow. Someone in our radio club offered it to me for free. I am anxious to see what it looks like.

73 Doug
WA3DSP
www.crompton.com/hamradio

Nice job on the ranger....Thanks for documenting it....