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Author Topic: Look what followed me home!  (Read 18458 times)
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AF9J
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« on: July 06, 2008, 08:26:44 PM »

Like most of you I've been just taking it easy over the 4th of July weekend.  Today, I went to the South Milwaukee/Oak Creek swapfest.  The stray radio below followed me home!

How it happend is a little weird.  A couple of hams at the swapfest were looking at a fixxer upper HW-101.  One of them made the comment "I don't know, after all, I have too many (radios) as it is."   I commented that I knew what they meant.  I was mulling a little bit over a Gonset, 6m Communicator IV, in spite of the fact that I really didn't need another 6m AM rig, since I have a Yaesu FT-620B that works just fine on 6m AM.  One of the guys mentioned that they run the 6m AM net, that's in the Chicago area, and I should check in on the Wednesday nights the net is held.  I said I'd love to, but being in the Milwaukee area, I don't have the power, and the directional antennas needed to make the grade (5W of carrier, with my rain gutter).  Both of the guys agreed that yes, my setup wouldn't cut during the propogation that existed during most net nights.  I mentioned that 2m would be a different story (I have my small log periodic, which is directional, and has gain on that band), but that there is basically no 2m AM activity in this part of the country.   
 
One of the tow guys then surprised me with some information.  He told me that they also run a 2m AM net.  It meets on 144.144 MHz (instead of the more AM traditional 144.400 MHz [APRS has hijacked that freq. for its use]), on Wednesday nights, after the 6m AM net is done.  Everybody uses vertical polarization (they use their FM antennas)."   Oh Cool!  The same guy who was selling the Gonset, was selling a Heathkit Twoer for peanuts.  I have an antenna with enough gain, that combined with my FM bricks (I have 2: a 70 watter; and a 30 watter that has a GasFET receive preamp in it) should do the trick, since AM rigs work OK with Class C amps.   So, I decided to get me a 2m AM rig.  Unfortunately, unlike last year, there weren't any Clegg 22ers at the 'fest this year (which is too bad - Clegg gear is pretty decent stuff).  So, I decided to do some more looking.  I found a Lafayette HA-144 2m AM portable.  But it mainly runs off of batteries.  And, the battery compartment was corroded (probably no big deal).  But it did have the manual, and mic. The guy selling it said he'd give it to me for $25.  I decided to do more looking.  I ran into some of the gang who were at the AM get together I went to last week.  They tried to egg me into getting the Lunchbox, saying it had more character than the Lafayette.  I decided to look some more.  I couldn't find anything else 2m AM related.  I walked past the table with the Gonset Communicator IV, and the Benton Harbor Lunchbox for the 3rd time, and the guy selling them aksed what I was willing to pay for the Twoer. I said $10. He asked me if I'd pay $12, and I said sure. So for $12, I became the owner of a Heathkit HW-30, 2m AM transceiver.  I bought the proper amphenol mic connector, and an RCA to SO-239 adapter (for the antenna jack)  from a parts vendor who was at the 'fest for another $6.  An old timer sold me a Shure 419A hand mic (I just downloaded the spec. and wiring sheet for it - it's high impedance, which should keep the Twoer happy [it's next to the Twoer in the photo]) for $2.  So, other than recapping (and any other internal stuff), and getting my hands on the appropriate crystal (I need one for 8008 kc), I'm good to go on 2m AM.   There is a big switch up by where the Heathkit logo is supposed to be. I'll have to figure out what that's all about.  But other than that, it shouldn't (hopefully) be a big pain to get the Lunchbox up and running.

73,
Ellen - AF9J


* My Twoer - Hamfest Day July 6, 2008.jpg (194.26 KB, 1600x1200 - viewed 816 times.)
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kf6pqt
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« Reply #1 on: July 06, 2008, 09:30:56 PM »

Wow, the biggest score was finding out about that net!  I very much wish someone would start something similar here.

$12 to Bry Carling should get you the rock you need.

Let me know if you need any un-obtanium parts for the twoer, I've got a couple that are hacked-up junkers.

Let us know how it works out!

73,
Jason kf6pqt
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AF9J
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« Reply #2 on: July 06, 2008, 09:35:43 PM »

Thanks Jason!

73,
Ellen - AF9J
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« Reply #3 on: July 06, 2008, 10:29:09 PM »

I have an antenna with enough gain, that combined with my FM bricks (I have 2: a 70 watter; and a 30 watter that has a GasFET receive preamp in it) should do the trick, since AM rigs work OK with Class C amps. 

Ellen,

I think you'll want to do some more checking on those bricks: if they're really running Class C, they won't be usable for AM, since AM requires a linear amp unless you're going to build an outboard modulator.

BTW, I didn't know there was a Clegg model "33'er". Did I miss an inside joke?

73,

Bill W1AC
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AF9J
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« Reply #4 on: July 06, 2008, 11:26:19 PM »

Ahhhhh!  I goofed!  You're right Bill.  Clegg made the 22er.  MY bad!  Last year the swapfest had FOUR of them at various tables.  This year there wasn't a single one.  I didn't know you couldn't run the typical Class C FM amp for AM.  I guess I erroneusly assumed that since my Viking II runs Class C to get it's 100W of carrier with 2, 6146s, that Class C in General was OK for AM rigs.   Thanks for the info.  Hmmm.  I guess I'll have to get my hands on an old Mirage 2m SSB & CW brick.     

73,
Ellen - AF9J
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« Reply #5 on: July 06, 2008, 11:48:18 PM »

Yah, Bill has that right Ellen. Your Viking II uses high level plate modulation to handle your pair of 6146's running in class C. As you surmised, you will need to use a linear amplifier to boost the little two-er. That's a great find, congratulations!

Rob W1AEX
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« Reply #6 on: July 07, 2008, 03:22:03 AM »

The HA-144 was a real dog even when it was "new" out of the box. The HW-30 is generally very broad on receive, so if you have some strong SSB or FM stations transmitting near by (within a couple hundred KHz), the receiver becomes useless. The Clegg 22'er or 22'er MKII are great 2 meter AM rigs. So is the Gonset Communication series. My favorite 2 meter AM rig is the Lafayette HA-1200.

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AF9J
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« Reply #7 on: July 07, 2008, 07:40:45 AM »

Yep Pete,

I really wanted a Clegg 22er.  But there are few that come up for sale on the internet.  If only I'd known last year (I found out to my chagrin that the 2m AM net was already in existence then), I would have bought one of the 4 I saw then.  They were going for only 20 or 30 dollars.  I know about the Twoer's superregen being broad as a barn door for selectivity.  Usually Wednesday nights are pretty quiet around here.  I just hope that Ken, W9GA in Germantown (about 15 miles north of me) doesn't decide to fire up on 2 when the Twoer is in use.  With the KW he uses on 2 (Ken runs big power [several hundred watts or so] all the way up to 2304 MHz), he'll probably nuke out the front end. 

73,
Ellen - AF9J
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« Reply #8 on: July 07, 2008, 12:04:51 PM »

  I didn't know you couldn't run the typical Class C FM amp for AM. 
Ellen - AF9J


Ellen, before you buy a new brick "linear" maybe you can use the class C ones you have.   I saw your original comment and figured you were thinking what I am about to say when running class C amps as LINEAR AM amplifiers.... This is not printed in the handbooks and surprised me when I first tried it....


Yes, normally, a class C amp will have severe cross-over distortion on ssb cuz there is no signal passing thru at low levels since the amp is biased below cutoff for the low level signal. But once this same  signal gets stronger and moves into the conduction area, the class C amp amplifies linearily OK due to flywheel effect. This is only if a fixed (regulated) grid bias is used. A grid leak bias (often used for AM high level amps) will not produce a clean linear amplified signal (when low level grid driven)


Now here's the rub.  I have tried many homebrew LINEARS on AM where I was able to change the FIXED bias from class A all the way down past class C, way past cut-off.  In class C on ssb, they sound terrible, of course.   BUT... on AM they sound fine. It seems that the constant carrier is keeping the tube into the conduction cycle creating a "simulated" class AB operation.

In efficiency tests, I could not see much difference between full carrier AM using class AB or class C operation. The dead carrier efficiency is still about 33% and the peaks still run about 60% or so.  There are no free lunches here.

So, when using class C, fixed bias, running a full AM carrier appears to work because of the normal tank "flywheel effect," -  whereas the audio is now pushed within the conduction range - cuz the constant carrier keeps the tube on. (And maybe some flywheel effect too.)

In the past I've talked this over with a few people who knew more about amplifers than me, and they have noticed similar results.

So, if your brick class C amps use fixed bias (they probably do) you might like to try them as-is for constant carrier AM operation.

Last resort, see what it takes to bias the class C amps into class B. Maybe just a lower zener voltage change.  But my gut feeling is if your SS amps are like tube operation, they will be OK on AM in class C for the reasons discussed.

Other opinions and experiences welcome.

T
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« Reply #9 on: July 07, 2008, 02:44:15 PM »

  "  BTW, I didn't know there was a Clegg moder "33'er". Did I miss an inside joke?  "

I think you are thinking of the Latrobe 33.


klc
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The Slab Bacon
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« Reply #10 on: July 07, 2008, 03:19:44 PM »

Ya just nevah know what might follow you home! I came to work today and a poor orphaned HQ-140X followed me to my truck and jumped in!! I'm gonna take him home and give him a good new place to live!! Cool


As far as lunchboxes go, no one has more of them that Vortex Joe!! He most have at lease 200 of them!! Shocked Shocked

                                                The Slab Bacon
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« Reply #11 on: July 07, 2008, 05:00:01 PM »

Ellen,
I came home with the 6m version sometime ago.  Never put it on the air. It's in good shape but have no idea if it really works. Something to play with.
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AF9J
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« Reply #12 on: July 07, 2008, 05:01:11 PM »

Yep, cool stuff people!  

JJ, thanks for the info.  I was wondering why a Class C FM amp wouldn't work for AM.  I've known for a dog's age that due to their cutoff, Class C amps won't ramp up fast enough, to properly amplify an SSB signal to avoid crossover distortion.  I was assuming/hoping that maintaining a signal into the finals would keep them conducting, and make them behave for AM.  Also, the guy I talked to yesterday, told me that many of the net participants use FM amps with pretty decent results audiowise during the net.  I'll try out my little 30W brick first, to see how it goes.  Once again, many thanks for the info JJ.

73,
Ellen - AF9J
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AF9J
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« Reply #13 on: July 07, 2008, 05:03:38 PM »

Ellen,
I came home with the 6m version sometime ago.  Never put it on the air. It's in good shape but have no idea if it really works. Something to play with.

Hi Bob,  Yep, I figured it might make a fun/quick and dirty summertime project.  But, it does have a mod to it (a switch or pot [I don't know - it seems to be jammed]), up where the Heathkit logo goes.  I just hope it isn't one of those kluged together mods.

73,
Ellen - AF9J
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« Reply #14 on: July 07, 2008, 09:53:02 PM »

Yep, cool stuff people!  

JJ, thanks for the info.   Also, the guy I talked to yesterday, told me that many of the net participants use FM amps with pretty decent results audiowise during the net.  I'll try out my little 30W brick first, to see how it goes.  Once again, many thanks for the info JJ.

73,
Ellen - AF9J


Ellen,

Sounds good. 

When you get the Twoer and Class C FM amp on the air, do a test. First, go barefoot and count to twenty -  let your buddy tune up and down the band to determine your relative bandwidth crud.  Then put on the amp and have him put in 10db of RX attenuation and you count again. Your side products may be slightly wider by a kc or so, but not real bad. 

Make sure the amp is not being overdriven, as that will cause more side crud than anything else.

 Let me know what you find... I'm curious.

T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

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There's nothing like an old dog.
AF9J
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« Reply #15 on: July 08, 2008, 12:02:06 AM »

Well, the FM amp use for AM issue, just became less crtical for me.  My Power Plus HL-35V 2m amp w/GasFet receive pre-amp, is an all mode linear amp.  Most cool.  I never even realized that the amp is all mode. I got it for my HT about 11 or 12 years ago.  It's still made.  The cost about $30 more than when I bought mine.  The other 2m brick I have (a TPL Econline - given to me by my neighbor),is an FM only amplifier.  Oh well.  At least I have a useable amp. 

73,
Ellen - AF9J
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K1JJ
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« Reply #16 on: July 08, 2008, 11:42:06 AM »

That's good.  Looks like you're all set.

Well, if you could, try the same side crud test comparing the FM class C amp against the linear. I'll bet others could use this info if they ever find themselves in the same situation in the future.  This being an AM BB, it would give a special technical use advantage that ssb does not have with class C amps... Grin

Personally, I've only tried TUBE class C linear amps on AM and never tried it with a SS amp. I'm wondering if final L/C tank in a solid state amp is sufficient as well as the AM carrier simulated bias effect.

Later -

T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

Wise Words : "I'm as old as I've ever been... and I'm as young as I'll ever be."

There's nothing like an old dog.
AF9J
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« Reply #17 on: July 08, 2008, 02:43:41 PM »

Sure thing JJ.  I'm kind of curious myself.

73,
Ellen - AF9J
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« Reply #18 on: July 08, 2008, 03:09:10 PM »

just FWIW, some years back, we found a quick and dirty way to get some cheap power for 6 & 2 using outpoot strips from old land mobile 2-way stuff. (GE and Motorola) This stuff was (and still is) cheap and plentiful.

For FM, of course it worked FB right out of the box. But.......... for SSB it was a little trickier due to the fact these were class-C amps. I used to get crazy using
"pull up" resistors to get them somewhere closer to class B or AB. Using pull up resistors sometimes caused some instability problems with these amps.

By accident we found an even quicker and dirtier way to do it!! Leave the power strips operating class-C, and induce a little background noise into the microphone to start the transistors conducting. This really dramatically reduced the distortion when using them for SSB. they actually sounded quite respectable for what they were.

Back then we never tried them for AM, but having a constant carrier should do the same thing as the background noise. Hmmmm....................

Just my $.03 worth.

                                                The Slab Bacon 
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AF9J
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« Reply #19 on: July 08, 2008, 05:07:21 PM »

<Written while listening to Davie Allan & the Arrows performing "Blues's Theme">

I forgot to mention - I didn't have time to open up the Twoer last night (I got home late from helping out at the animal shelter, and I just wanted to eat and go to bed).  But, I did open it up, and take a quick peek inside before I left for work.  The mod on the front panel, is for channel switching.  Whoever owned it way back when, made it capable of switching between 2 crystals with an old wafer switch.  The crystal holder - a tube socket!  Just like some of the old novice transmitters.  From looking at the wiring & the socket, it should be able to hold 2 crystals.

At the risk of straying off into the Technical section of the forum, I have a question.  During my quick look at the Twoer, I noticed a big honking metal can capacitor on the top of the chassis.  I looked at it to try to read what value it was.  I saw 4 rows of what looked like different capacitance values stamped on it.  Do the Heathkit lunchboxes use 4 section/value capacitors in them? I remember replacing a couple of two dual capacitors in my Viker 2.  It was a big enough pain mounting replacement capacitors in that radio.  I shudder at the thought of trying to install/mount up 4 replacement capacitors in the Twoer.

73,
Ellen - AF9J
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« Reply #20 on: July 08, 2008, 05:39:00 PM »

Yes, it is a 40/40/25/25 uF cap.

Take advantage of the smaller axial caps available today - order thru Digi-Key. Use a small pipecutter, tubecutter or saw to cleanly cut the multi-section cap apart (I usually cut 1/4 to 1/2" from the bottom). You may need to heat the cap up with a hair-dryer to warm up the wax/adhesive inside, to allow you to pull the top of the can off. Clip the capacitor from its lugs.

Using leads, bus wire and heat shrink, build the capacitor assembly - cover all of the non-grounded leads. Solder to the lugs on the bottom end of the can. The side of the can, and the corresponding markings on the bottom end (you know, square, half-moon, triangle) will tell you what goes where....

Then fix the rest of the radio (if you left the base of the can in place), or test your new cap (if you took it out). Wait until you know that cap is OK. Experience talking ;-(

Once you know things are OK, gob some electronic RTV into the top can, slip it over your assembly, use some tape to hold the two parts of the can together. Wait 48 hours. Then, come back, use some epoxy to glue the can together - J-B Weld ain't bad. Apply the tape again. Wait, or leave it on for good - up to you.

Seems like alot of work, but it is so much nicer to fit the caps this way than stuffing them into space that might be taken up by power resistors and such.

David Goncalves
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W1EUJ
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« Reply #21 on: July 08, 2008, 05:44:35 PM »

Also, companies like Antique Electronic Supply, Hayseed Hamfest, and Frontier Capacitor are making multisection caps, perhaps even the exact replacement for what you have.

Good luck. I'm rebuilding caps for a Tempo One power supply.
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AF9J
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« Reply #22 on: July 08, 2008, 07:10:32 PM »

Thanks for the info Dave. 

I'll probably just get a direct replacement for it.  It looks like a twistlock cap. I remember replacing the HV twistlocks last year, in the HP-23A power supply I recapped.  Those things are a pain to remove (due to the solder used to ground the twist tabs to the rings).  I ended up just clipping the old caps off at the tabs, and gluing the replacement radial caps I got in place. 

73,
Ellen - AF9J   
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« Reply #23 on: July 08, 2008, 07:32:26 PM »

Hi Ellen,

I had a Twoer given to me by an expired novice when I was a little peanut whistle in high school. It was immaculate and a local ham gave me a crystal so I could check into the civil defence net every Sunday night at 8 PM.

The two tube transmitter was really simple and the modulation was excellent being a center tapped Hiesing arrangement. About 3 Watts out but into my horizontal cut 6 (a cut down TV yagi antenna) it was heard 35 miles away regularly by an OT using an Ameco converter into an HRO. He had a nice antenna farm and a big transmitter and I could easily copy him. Super-Regens are fun, very sensitive and broad as a barn, capturing everything that is strong enough (including bad things like a nearby FM repeater!).

Downside:
The receiver although buffered by a common grid stage if I remember, still managed to screw up a ham nieghbor with re-radiation.

I hated the loud rushing noise of the receiver when no signal was present and the audio stages were somewhat microphonic.

The lever transmit switch is at first cool - then a pain.

Later in life I actually was successful at making a squelch for a super-regen, but that circuit turned out to be 3X more complex than the super-regen itself!

Good Luck!

Mike WU2D
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W1EUJ
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« Reply #24 on: July 08, 2008, 08:48:44 PM »

As goofily simple as this sounds, fat solder wick, a good soldering iron tip, needlenose pliers, and a solder sucker will extract anything. I've extracted twistlocs this way myself.

Anyway, good luck on the twoer.

David Goncalves
W1EUJ
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